Yep Flashcards

Question

Where are the cell body of sensory neurons situated?

Answer 1

They are situated immediately or a short distance below the integument.

Answer 2

Between two and five and in gustatory one of these may be mechanosensory.

Answer 3

Protect the odorants from degrading enzymes present in the lymph and, by diffusion, transport these across the sensilar sinus.

Answer 4

It is possible but it is generally thought that the recognition is done by the receptors on the dendrite membrane.

Answer 5

Water-satiated Culiseta inornata which would not give labellar response when the arboral sensilla were touched with water, would do so if, at the same time, the tarsi were in contact with sucrose, revealing central integration of gustatory stimuli.

Answer 6

Neurons with dendrites in the distal antennal segment (flagellomere 13) that are phasic thermoreceptors that respond to temperature change rather than absolute temperature and they express IR21a (Anopheles gambiae)

Answer 7

Greppi uses 4% CO2 for 20 seconds

Answer 8

It does not disrupt orientation toward sensory cues and argue against the presence of global deficits in the mutants

Answer 9

They modified a previously used olfactometer. When DEET was presented alone the mosquitoes moved toward the source. When combined lactic acid with DEET they did not observe any attraction or repulsion

Answer 10

DEET is a neutral compound.

Answer 11

Rogan and Rossignol presented deet and lactic acid impregnated gauze pads side by side in a Petri dish, we observed the same inhibitory response. The deet–lactic acid trials gave significantly different results than the control. deet and lactic acid impregnated gauze attracted only 14% of the mosquitoes; using ethanol (the diluent for most repellents) as the control attracted 52% of the mosquitoes. They concluded that deet acts on the mosquito and not directly on lactic acid. Furthermore, in Pellegrino et al.: In response to the suggestion that DEET and odours may interact in the vapour phase, we first quantified the respective amounts of vapour-phase 1-octen-3-ol emitted from the stimulus pipette in the presence and absence of DEET, using solid-phase microextraction (SPME) followed by gas chromatography mass spectroscopy analysis (GC–MS). The SPME measurements coupled to GC-MS showed that the addition of a second filter paper containing pure DEET in the stimulus pipette had no significant effect on the release of 1-octen-3-ol (10−2 dilution). Thus, we can rule out any fixative role of DEET under the conditions used here. Bahbot (2011): One possible explanation for the inhibitory effects observed for DEET on responses of AaOR8 to octenol is that DEET might reduce the amount of ligand available for delivery to the receptor. This reduction in the amount of the proper ligand might be accomplished by diminishing the amount of octenol present in the solution due to the reactivity of the amide and carbonyl moieties present in the DEET molecule with octenol. Extracts of physiological solutions containing DMSO and octenol with or without DEET revealed nearly identical quantities of both compounds (Fig. 4).

Answer 12

No, the chemical structure of DEET (N,N-Diethyl-meta-toluamide) is different from that of picaridin (known as Icaridin outside the US), which is also known as 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester. DEET contains a toluene group and a diethyl group, while picaridin has a piperidine ring and a carboxylic acid ester. Although both chemicals are used as insect repellents, they have different chemical properties and mechanisms of action.

Answer 13

It was complex and dependent on odorant receptor, odour and concentration. In some OSNs DEET suppressed odor-mediated inhibition, in other it decreased activation.

Answer 14

the effects of DEET were strongly concentration dependent, such that high odour concentrations often overcame the effects of DEET

Answer 15

DEET presented alone, without odour stimuli, elicited no response above that evoked by solvent in ab2A and ab3A neurons, slightly activated ab2B neurons and slightly inhibited ab3B neurons; but responses were considerably smaller than those elicited by cognate odour ligands.

Answer 16

Notably, 1-octen-3-ol presented in a dilution of 10−2 had opposite effects on the two neurons housed in ab2 sensilla, inhibiting the ab2A neuron expressing OR59B–ORCO (Fig. 1d) and activating the ab2B neuron expressing OR85A–ORCO (Fig. 1e). Co-application of DEET inverted OSN responses to odour, leading to activation of the ab2A neuron (Fig. 1d) and suppressing the odour-induced activation of the ab2B neuron (Fig. 1e). Similar opposite effects of DEET were observed when the ab2 sensillum was stimulated with a different odour, 1-octanol

Answer 17

- Scrambling hypotheses - A single, naturally occurring polymorphism in an odour-specific odorant receptor can modify receptor interactions with an inhibitory odour and render the receptor insensitive to modulation by DEET.

Answer 18

The data demonstrate that repellents can act as olfactory agonists or antagonists, thus modulating OR activity, bringing concordance to conflicting models.

Answer 19

DEET may directly target insect acetylcholinesterases, mosquito ORs and it may chemically sequester a mosquito attractant.

Answer 20

Ditzen et al. (2008) previously characterized DEET interactions with Anopheles gambiae ORs co-expressed with AgOR7; activation of AgOR2 by 2-methyl phenol and AgOR8 by racemic 1-octen-3-ol was differentially inhibited by DEET suggesting that DEET selectively inhibited the different odor-specific subunits (OR2 and OR8) rather than the common co-receptor (ORCO)

Answer 21

Yes, DEET administered alone activated AaOR2 in a concentration dependent manner.

Answer 22

AaOR2 response to indole was only slightly inhibited by DEET.

Answer 23

AaOR8 response to octenol was strongly and significantly inhibited by DEET. Ditzen: The B cell responded to 1-octen-3-ol with a median effective concentration (EC50) of 1.7 × 10−10 , which was shifted to 2.5 × 10−7 in the pres- ence of DEET (Fig. 1D).

Answer 24

AaOR2 and AaOR8 were exposed to a range of IR3535 and Picaridin concentrations (1027 M21022 M) in the presence of their respective odorants indole and octenol (both at 1027 M) (Fig. 5A and 5C). Both compounds strongly and significantly reduced AaOR2 and AaOR8 responses to indole and octenol in a concentration dependent manner.

Answer 25

Bahbot (2011): In our study, millimolar doses of repellents were necessary to achieve both odorant-independent activation and odorant-depen- dent inhibition of ORs. These high concentrations are consistent with the high amounts of repellents required in commercial formulations and the large quantities needed to elicit physiological responses in mosquito OSNs [4,5,37]. While the amount of repellents going into vapor phase is unknown, it is clear that large quantities are required to achieve close range protection against arthropod bites. At the physiological level, indole-sensitive neurons were activated by DEET only at high concentrations (apparent threshold of 100 mg). Our observations have in common with prior studies that DEET activates OSNs at extremely high concentrations consid- ering the reported sensitivity of these neurons to their cognate ligands. For example, in our study, both DEET and 2-U respectively activate OR2 and OR8 at 1023 M while their respective ligands are active at 1028 M

Answer 26

DEET and 2-U differentially inhibited odorant- induced activity of AaOR8 and AaOR2, but in opposite relationship with repellent induced activation, suggesting inde- pendent OR binding sites for activation and inhibition. The differential inhibitory activities of DEET and 2-U on AaOR2 and AaOR8 suggest that inhibitory binding sites for these repellents associate with the OR2 and OR8 subunits. Inhibitory activities of DEET and 2-U may thus be more influenced by differences in OR2 and OR8 sequence than the activities of IR3535 and Picaridin.

Answer 27

DEET alone has been shown to inhibit several classes of OSNs in insects, including lactic acid-sensitive OSNs in Ae. aegypti [19,20], various Drosophila OSNs and the 1-octen-3-ol receptor neuron of An. gambiae [4]. Ditzen et al. [4] showed that responses of AgOR2 to 2-methylphenol and AgOR8 to racemic 1-octen-3-ol were differentially inhibited by DEET in the oocyte system with the strongest inhibitory effect on the latter

Answer 28

The inhibitory effects of all four repellents were reversible upon fresh exposure to the odorant alone, suggesting that the interaction between the inhibitors and the ORs is as labile as the one between the receptor and its cognate odorant.

Answer 29

DEET, IR3535 and Picaridin all possess an amide moiety. Small amide derivatives have been shown to affect a wide range of molecular pathways through allosteric regulation of various proteins including proteases [39,40], the cannabinoid receptor 1 (CB1) [41], the a7 nicotinic acetylcholine [42] and GABA A receptors [43]. The broad activity of such compounds is mirrored by DEET’s inhibitory effects on phylogenetically unrelated cation channels [4] and underscores that there might be alternative modes of action yet unknown.

Answer 30

It inhibits them.

Answer 31

CO2-evoked responses of the cpA cell were unaffected by DEET, suggesting that olfactory transduction mediated by the CO2 receptor is not affected by the repellent. Syed and Leal: We found no difference in neuronal responses, including spike frequencies and magnitude and kinetics of the receptor potential, when the carbon dioxide-sensitive ORN in the sensilla on the maxillary palps (10) were stimulated with CO 2 in the presence or absence of DEET [

Answer 32

Yes, in Ditzen (2008) To investigate whether DEET inhibition of electrophysiological responses of ab5B translated to an effect on behavior, we carried out trap as- says with 3-methylthio-1-propanol. Flies showed potent attraction to 3-methylthio-1-propanol (Fig. 3E, left), and this attraction was significantly de- creased by DEET (Fig. 3E, right). Odor-evoked activity in the Or47a- and Or83b-expressing ab5B neuron thus contributes to attractive behavior that can be inhibited by DEET and allows us to cor- relate a selective electrophysiological effect of DEET with a behavioral phenotype. Consistent with the failure of DEET to inhibit methyl acetate responses of ab2 (Fig. 3B, top), DEET did not alter behavioral responses to methyl acetate in the trap assay (Fig. 3F). We were unable to test the behavioral relevance of ab5A inhibition by DEET because flies were not attracted to geranyl acetate in our trap assays.

Answer 33

Ditzen analyzed current-voltage relation curves during ligand stimulation in the presence and absene of DEET. The effect of DEET on OR-evoked current was symmetric at positive and negative potentials, and no change in reversal potential was observed. This suggests a reduction in permeabilityof the channels affected by DEET, but no change in ion selectivity.

Answer 34

mouse TRPM8 (mTRPM8), the het- erotrimeric rat olfactory cyclic-nucleotide gated (CNG) channel, and the Drosophila ether-a-go- go potassium channel (Fig. 4L). This suggests that DEET may interfere generally with the ionic permeability of a subset of cation channels.

Answer 35

Mosquito smell and avoid DEET directly and a trichoid sensilium responds to DEET in a dose-dependent manner that also responded to terpenoids. They found no difference in response when they administered DEET with 1-octen-3-ol.

Answer 36

Terpenoids, also known as terpenes, are a large and diverse group of naturally occurring organic compounds that are found in plants, fungi, and some animals. They are derived from five-carbon isoprene units, which can be combined in a variety of ways to form a vast array of different terpenoids. Terpenoids are responsible for many of the distinctive aromas and flavors of plants, such as the fresh, citrusy scent of lemons and the spicy aroma of cloves. They also have a wide range of biological functions, including acting as signaling molecules, serving as structural components of cell membranes, and providing defense against herbivores and pathogens.

Answer 37

This is controversial. Syed and Leal observed that DEET alone is sufficient to induce repulsion. Some indoor and field experiments cited in that paper also indicated that DEET acted as a repellent even when just CO2 was provided.

Answer 38

They have only one morpholical and physiological type of olfactory sensilia, the peg sensilia on the fourth segment.

Answer 39

Syed and Leal using quinquefasciatus have observed no responses to DEET in the >100 peg sensilla.

Answer 40

It responded in a dose-dependent manner to terpenoid compounds such as thujone, ecualyptol and linalool (all reported as repellents)

Answer 41

Syed and Leal observed a significant decrease in the amounts of the major compounds release from the skin, namely 6-methyl-5-heptn-2-one, octanal, nonanal, decanal, and gernayl acetone

Answer 42

Yes (Syed and Leal)

Answer 43

Labella and tarsi

Answer 44

A pair of front tarsi that contain the Haller's organ, and a pair of pedipalps. The receptor proteins in these two structures differ from the mosquito sensory receptors found in the antennae and max palps.

Answer 45

Chelicerata and Hexapoda are two subphyla of Arthropoda (ticks belonging to Chelicerata and mosquitoes to Hexapoda). The ancestors of Chelicerata and Hexapoda diverged about 300 million years ago from a common ancestor. An important difference between these two subphyla is that Hexapoda have odorant, gustatory, and ionotropic receptors, whereas Chelicerata only have gustatory and ionotropic receptors

Answer 46

Some hours. Luker_Hansen (2023) reports up to 6 hours for both ticks and mosquitoes.

Answer 47

Ar-turmerone belongs to the class of organic compounds known as sesquiterpenoids. Sesquiterpenoids are a type of terpenoid, which are organic compounds produced by plants and other organisms, and they are built from three isoprene units (15 carbon atoms in total). Ar-turmerone is a specific type of sesquiterpenoid that is found in the essential oil of turmeric (Curcuma longa). It is known for its potential health benefits, including anti-inflammatory and antioxidant effects.

Answer 48

Caryophhyllene (E-), Longifolene, and Myrtanol Acetate

Answer 49

For mosquito contact repellency testing, the US EPA reccomends testing pesticide products through field testing or arm in cage assay both of which requires a live volunteer.

Answer 50

It is very complex with individual oil containing dozens of different terpenes. Essential oils that contain few terpenes such as castor oil don't repel mosquitoes or ticks (Luker_Hansen).

Answer 51

Luker founds that the solvent used for essential oil repellent product greatly determines an essential oil's property to repel mosquitoes and protect from bites.

Answer 52

AaegOR84, AaegOR113, and AaegOR11 are three of the most74 expressed ORs in the female yellow fever mosquito antennae

Answer 53

To many compounds including fenchone a potent repellent but did not evoke repellency compared to DEET in Wu and Leal (2022). It also responded to 2,3-dimethylphenol that has strong repellency activity.

Answer 54

They target the lateral horn (Fisek, Wilson).

Answer 55

Here we show that lateral horn neurons (LHNs) receive input from sparse and stereotyped combinations of glomeruli that are coactivated by odors, and certain combinations of glomeruli are over-represented. One morphological LHN type is broadly tuned and sums input from multiple glomeruli. hese neurons have a broader dynamic range than their individual glomerular inputs do. By contrast, a second morphological type is narrowly tuned and receives prominent odor-selective inhibition through both direct and indirect pathways. We show that this wiring scheme confers increased selectivity. The biased stereotyped connectivity of the lateral horn contrasts with the probabilistic wiring of the mushroom body, reflecting the distinct roles of these regions in innate as compared to learned behaviors.

Answer 56

it is sufficient to mediate behav- ioral responses to odors that do not involve learned associations3,7,8, and it receives the majority of glomerular projections.

Answer 57

A theoretical study by Riffell proposed that LHNs might add and subtract sparse, weighted inputs from coactivated glomeruli. Suggesting that combinations of glomeruli should be overreprestented, namely glomeruli whose sum or difference represents a behaviorally useful computation.

Answer 58

Fisek and Wilson identify two classes (Type I and Type II, dorsomedial and ventrolateral respectively) and they innervate different parts of the protocerebrum. The former are broadly tuned, whereas the latter were more selective. Type I neurons received inputs from 3 to 4 invariant glomeruli co-activated by many fruity-smelling organic acetates.

Answer 59

The postsynaptic response was accurately predicted by summing the responses to each input alone. So the input sum in a fairly linear manner, although they elicit modestly supralinear postsynaptic responses at weak presynaptic firing rates. Summing input in this manner could allow LHNs to be sensitive to a broader range of stimuli than any single one of their input glomeruli (they encode a broader range of concentrations as compared to their individual presynaptic PNs).

Answer 60

It is narrower than the input to Type I neurons. In some cases just one PN from one glomerulus project to a type I neuron. This input might be gated by inhibition of other glomeruli which makes the LH not sensitive to all the odors of the cognate glomerulus.

Answer 61

Some inhibition arises from a direct GABAergic projec- tion from the antennal lobe, and additional inhibition arises from a local GABAergic circuit within the lateral horn. Although inhibition is much more prominent in type II neurons, it can occasionally be seen in type I neurons as well

Answer 62

In Drosophila (Fisek and Wilson): Our paired recordings also showed that different glomerular inputs to an LHN can be associated with nonuniform and stereotyped syn- aptic weights. This idea has been proposed previously as a way to render LHNs more selective for a particular olfactory feature4. This result also indicates a high level of precision in the development of this circuit.

Answer 63

Broad odor tuning to a group of related chemicals might be a useful way to link a large region of chemical space (for exam- ple, odors associated with fruit) with an innate behavioral program (for example, feeding).

Answer 64

In Drosophila, higher-order olfac- tory receptive fields represent weighted sums of molecular features. In other sensory systems, receptive field structures are nonrandom insofar as they have a strong tendency to sample from overlapping regions of stimulus space, reflecting the statistical regularities of the environment

Answer 65

Here, we describe a machine-learning-driven high-throughput method for the discovery of novel repellent molecules. To achieve this, we digitized a large, historic dataset containing ~19,000 mosquito repellency measurements. We then trained a graph neural network (GNN) to map molecular structure and repellency. We applied this model to select 317 candidate molecules to test in parallelizable behavioral assays, quantifying repellency in multiple pest species and in follow-up trials with human volunteers. The GNN approach outpeormed a chemoinformatic model and produced a hit rate that increased with training data size, suggesting that both model innovation and novel data collection were integral to predictive accuracy. We identied >10 molecules with repellency similar to or greater than the most widely used repellents.

Answer 66

No, (Wei, 2023), picaridin is effective against Aedes aegypti but is ineffective against Anopheles mosquito and is not reccomended for use in malaria-endemic regions.

Answer 67

Structure-targeted modeling of ORCO led to discovery of picaridin and VUAA1. Scaffold hopping in combination with arm-in-cage testing, led to the discovery of IR3535 and DEPA

Answer 68

we found that molecules selected by our model are enriched in benzenoids, ethers, carboxylic acid derivatives, and organoheterocyclic molecules when compared to the molecules measured by the USDA dataset

Answer 69

Typically two, but some house three or four ORNs.

Answer 70

roughly 50

Answer 71

Most individual ORN types respond to multiple ligands, and most individual li- gands activate multiple ORN types. The best ligands for a neuron often do not fall into a single chemical class.

Answer 72

The firing rate rise with increasing concentration; they have typical dynamic range of approximately two orders of magnitude in odor concentration. Increasing concentration tends to recruit responses in a larger number of ORN types and ORNs become broadly tuned at higher concentrations.

Answer 73

Yes, spike rates peak rapidly and subsequently relax to a tonic level of activity.

Answer 74

Importantly, swapping receptors between ORNs swaps their odor responses (Hallem et al. 2004). Recep- tor swap also recapitulates the dynamics of odor responses. Thus, all of the diversity in ORN odor responses is likely due to diversity in ORN odorant receptor expression. In other words, the different ORN types are function- ally generic, except that they express different receptors

Answer 75

They respond to social odors. For example, two types of ORNs respond to CVA (cys-vaccenyl acetate) which is produced exclusively by males. These odors trigger robust behaviors. Some of the central neurons postsynaptic to these ORNs have unusual properties or patterns of connectivity, suggesting specialization for social odor processing.

Answer 76

Yes, all ORNs fire spontaneously and each ORN type has a characteristic spontaneous firing rate. Mutating odorant receptor diminishes the spontaneous rate. In some cases an odor can inhibit spontaneous firing.

Answer 77

No, most odors inhibit at least one ORN type while exciting other types, meaning no odors is inhibitory per see. Kreher and Carlson: At the higher doses, most odorants inhibited at least one receptor, and most receptors were inhibited by at least one odorant.

Answer 78

Spontaneous activity in ORNs is puzzling from a functional standpoint because it sim- ply adds noise to the system. Why hasn’t the fly evolved odorant receptors that are inac- tive when unbound? Spontaneous transduction might be useful because it depolarizes the cell’s resting potential to near its spike threshold. Al- ternatively, it might just be difficult to evolve a receptor protein with the requisite specificity and kinetics that is never activated in the ab- sence of a ligand

Answer 79

On average, a Drosophila ORN fires 8 spikes/s in the absence of an odor (de Bruyne et al. 1999, 2001). Because each antenna contains 1,200 ORNs (Stocker et al. 1990), the brain is continuously barraged by ∼20,000 ORN spikes/s, even when no odor is present.

Answer 80

By multiple ORN types with overlapping receptive fields.The recruitment of multiple ORN types is also important because each type is sensitive to concentration over a restricted concentration range.

Answer 81

Every ORN odor response depends on (a) odor identity, (b) odor con- centration, and (c) the rate of change in odor concentration. Nevertheless, behavioral experiments indicate that odor identity and concentration are encoded independently in the Drosophila brain.

Answer 82

A stimulus that evokes a high firing rate in a given ORN type also tends to evoke a high firing rate in many other ORN types. Conversely, a stimu- lus that elicits unusually weak activity in a given ORN type also tends to evoke weak or little activity in most other ORNs. In other words, there is substantial redundancy in ORN odor representations (Haddad et al. 2010, Luo et al. 2010, Olsen et al. 2010). This too has important implications for downstream odor processing.

Answer 83

The number of ORNs in a given glomerulus varies across glomeruli by a factor of about four and is correlated with glomerular size.

Answer 84

Each glomerulus contains the dendrites of several PNs, termed sister PNs; these sister PNs have highly correlated patterns of activity

Answer 85

PN responses show less variability in trial-to-trial spike count than do the responses of their presynaptic ORNs to the same stimulus. They are more broadly tuned to odors than their presynaptic ORNs. The odor responses of a PN can be sup- pressed by recruiting additional activity in other glomeruli. For example, when mixed with a second odor, an odor that elicits no response in a given PN when presented alone can inhibit that PN’s re- sponse to the second odor

Answer 86

This is explained by a small asymmetry in ORN neurotransmitter release properties: The ORN releases ∼40% more neurotransmitter per spike from its ipsilateral axon branch than from its contralateral axon branch. As a result, when an odor stimulus is lateralized, the PNs that are ipsilateral to the stimulus spike at slightly higher rates and with a slightly shorter latency than do those that are contralateral to the stimulus

Answer 87

They are cholinergic.

Answer 88

The net effect of lateral input to a PN is generally inhibitory. A PN odor response is typically disinhibited by silencing input to other glomeruli. Conversely, adding new odors to an odor mixture typically produces either sublinear summation or frank suppression.

Answer 89

Yes, because of lateral inhibition. These effects can be blocked by a combination of GABAa and GABAb receptor antagonists.

Answer 90

It is generally presynaptic, at the ORN axon terminal. Robust lateral inhibition requires active neurotransmitter release from ORN axons. When ORNs are silent, most lateral inhibition disappears.

Answer 91

The overall level of inhibition in the antennal lobe rises with increasing stimulus intensity. These results imply that the spatial pattern of GABA release depends on the stimulus, thereby suggesting a model where specific subsets of glomeruli are linked by inhibitory subnetworks and ORN input to a glomerulus recruits LN input to a specific sub- set of other glomeruli

Answer 92

The total ORN activity alone; that is, the identity of the active ORNs did not matter. Indeed, PN odor responses could be predicted with high accuracy on the basis of only two factors: the firing rate of the PNs cognate ORNs and the total firing rate of the entire ORN population. This finding susggests a model whereby inhibition is global, meaning all glomeruli inhibit each other.

Answer 93

Some LNs innervate a relatively subset of glomeruli and could therefore permit specific interactions between glomeruli. However, most individual LNs innervate most or all glomeruli. Therefore, some glomeruli might be interconnected in specific subnetworks. These subnetworks might be created by LNs with sparse innervation patterns or by electrical compartmentalization within the arbors of broadly innervating LNs.

Answer 94

Recall that even when no odor is present, ORNs as a population continuously barrage the brain with ∼20,000 ORN spikes/s. If ORNs wired ran- domly to PNs, then the task of detecting (for example) 10 odor-evoked spikes in this bar- rage would seem hopeless. But, if all 10 spikes were fired nearly synchronously by ORNs that were presynaptic to the same glomerulus, then they would likely summate effectively enough to drive a PN above its spike threshold. Thus, the orderly wiring of the olfactory system repre- sents a computational machine par excellence: an extreme and illustrative example of what has been proposed to be a generally useful strat- egy for organizing neural connectivity (Abbott 2008).

Answer 95

When sister ORNs are firing at a low rate, small increases in their firing rate cause relatively large increases in the firing rates of their postsynaptic PNs (Olsen et al. 2010). When ORNs are firing at high rates, they tend to saturate their postsynaptic PNs. Conse- quently, odor stimuli that elicit low ORN firing rates occupy the lion’s share of a PN’s dy- namic range (Bhandawat et al. 2007). Because most odor-evoked ORN firing rates are low (<50 spikes/s) compared with the maximum ORN firing rate (∼300 spikes/s) (Hallem & Carlson 2006), most of a PN’s dynamic range may be devoted to the most common odor stimuli (Figure 2). Thus, this property of PN tuning should maximize rates of information transmission (termed histogram equalization; Laughlin 1981). In simulations, the compres- sive nonlinearity in the relationship between ORN and PN firing rates substantially im- proves odor discrimination by a linear encoder (Luo et al. 2010, Olsen et al. 2010)

Answer 96

LNs collec- tively pool input from all glomeruli, and they inhibit ORN neurotransmitter release as ORN activity increases. This behavior makes PNs less sensitive to the firing rates of their cognate ORNs (Olsen et al. 2010, Olsen & Wilson 2008, Root et al. 2008). As a consequence of inhibition, PN firing rates do not saturate as easily as they would otherwise, and their dy- namic range becomes more closely matched to that of their inputs (Figure 2). In simulations, this type of lateral inhibition substantially im- proves odor discrimination by a linear decoder. In particular, it improves a decoder’s ability to identify an odor in a concentration-invariant manner (Luo et al. 2010, Olsen et al. 2010), implying that lateral inhibition may help flies identify odors in spite of natural variations in odor concentration. Lateral inhibition also decorrelates the activity of different PNs. The computation implemented by this type of lateral inhibition has been called divisive normalization, and it appears to play a role in a wide variety of sensory systems

Answer 97

Glomeruli differ in their levels of neuropeptide and neurotransmitter receptor expression; they may also differ in sen- sitivity to neurotransmitters (Nassel et al. 2008; Root et al. 2008, 2011).

Answer 98

Odors that activate multiple glomeruli elicit a behavior that can be accounted for by summing the weights associated with each glomerulus (Semmelhack & Wang 2009). This summation would predict that coactivating two attractive glomeruli would always produce attraction, never aversion. Is this true? Notably, many odors are attractive at low concentrations but aversive at higher concentration

Answer 99

This observa- tion can be reconciled with the sum-of-weights model, but only if the receptors for aversive glomeruli are systematically recruited only at high odor concentrations, implying low ligand-receptor affinities.

Answer 100

1) Reduced dimensionality of the tracked data. 2) Computed the distance between each pair ofbouts. 3) Combined similar bouts into exemplars by micro-clustering 4) Non-linear embedding using the distances between exemplars to generate the final behavioral space.

Answer 101

The goal of non-linear embedding is to find a mapping that can transform the original data into a lower-dimensional space, while preserving the local and global relationships between the data points. Unlike linear embeddings, which use linear transformations such as principal component analysis (PCA), non-linear embeddings use non-linear transformations that can capture more complex relationships between the data. One popular non-linear embedding technique is t-SNE (t-distributed stochastic neighbor embedding), which maps high-dimensional data points to a two- or three-dimensional space, while preserving the local structure of the data. Another example is UMAP (Uniform Manifold Approximation and Projection), which is a newer algorithm that uses a different mathematical framework to achieve similar results as t-SNE.

Answer 102

Mechanical and neural constraints impose limits on the possible posture configurations for an animal;

Answer 103

As our tracking provides overly redun- dant measurements along the tail, we performed principal component analysis (PCA) on the sequence of all tail postures. Three PCs explained 85% of the variance in tail shape (Fig- ure 1D). These PCs define postural modes and can be repre- sented by a set of tail shapes known as ‘‘eigenfish’’ [17, 34, 35] (Figure 1E). As posture is dynamic over time, these shapes trace a trajectory in three-dimensional coordinate space

Answer 104

He used dynamic time wapring, which handles temporal offsets and small variations better than Euclidean distance. From these dis- tances, we generated micro-clusters (each represented by a single exemplar) using affinity propagation

Answer 105

Next, we performed isomap embedding [39] using the DTW distances between exemplars (Figure 1I), which preserves global behavior structure preferentially to local structure. We could not discern any additional structure if we embedded all bouts, suggesting that we were not losing information about the structure of behavior by only embedding exemplars

Answer 106

He decomposed the one-step transition frequency matrix between micro-clusters into a set of transition modes, each of which captures some feature of temporal behavioral dynamics.

Answer 107

He compared the observed probabilites to randomly shuffled bout sequences.

Answer 108

With an increase in action potential frequency.

Answer 109

Carlsson and Hansson noticed that in the moth Spodopter littoraliis the most active glomerulus was concentration-dependent. Activity foci were only persistent across concentrations in 25% of the recorded concentration series. However, movement of activity focus was generally restricted to adjacent or proximal glomeruli.

Answer 110

The number of activate glomeruli increases. Dose response-curves often reach a plateau in the most strongly responding glomeruli, suggesting a sigmoid function.

Answer 111

Similarity is highest between responses evoked by the same compound. The correlation, however, decreased when the difference in concentration between stimuli increased. In some instances the glomerular patterns were actually more similar across odorants than across concentrations. The pattern evoked by distinct compounds tend to be more similar to each other when each is at highest concentration. However, this effect seems to depend on the similarity of the odorants.

Answer 112

In contrast to ORNs, LNs and PNs are often much less concentration-dependent and many interneurons do not express increased spike activity at concentrations above threshold levels.

Answer 113

A circularly permuted EGFP flanked on one side by the M13 fragment of myosin light chain kinase and on the other by the calcium binding site of calmodulin. In the presence of calcium, calmodulin interacts with the M13 fragment eliciting a conformational change in EGP resulting in elevations in fluorescent intensity that reflect changes in the intracellularcalcium concentration.

Answer 114

An enhancer trap line, GH146-Gal4, has been characterized that drives the expression of Gal4 in approximately 90 of the 200 PNs (Stocker et al., 1997; Jefferis et al., 2001). This subset of PNs innervates 34 of the 43 antennal lobe glomeruli (Laissue et al., 1999).

Answer 115

1) Fly was decapitated 2) Cuticle and connective tissue were removed from the head by microdissection to reveal the brain and attached antennae. 3) Specimen is embedded in agarose gel, and the antennae were exposedto allow quantitative delivery of odors via an olfactometer. This preparation provided responses up to five hours.

Answer 116

At low odor concentrations, the glomerular response is sparse. Exposure to three different odors, 1-octen-3- ol, hexane, and isoamyl acetate at 8% saturated vapor concentration (SV), reveals that each odor elicits a different pattern of glomerular activity and these patterns are conserved among different animals (Figure 1). At 2% SV, many odors fail to elicit a significant response and those that do activate a small number of glomeruli. At higher odor concentrations, the number of glomeruli activated by a given odor increases to reveal a dense map with individual odors activating from two to as many as 15 of the 23 glomeruli analyzed (Figures 2 and 3). The response to six odors at 33% SV results in a denser map with greater overlap. The VM2 and DM2 glomeruli for example respond to four or five of the six odors tested

Answer 117

The variability in antennal lobe structure appears at first to contrast with Drosophila melanogaster, where each glomerulus can be clearly identified and named. However, we note that the antennal lobe map in Drosophila melanogaster has been refined with the advent of new genetic techniques, starting with 35 glomeruli in the original atlas (Stocker et al., 1990), then modified to 40 glomeruli (Laissue et al., 1999), and further refined in numerous studies (Couto et al., 2005; Fishilevich and Vosshall, 2005; Tanaka et al., 2012) including a recent count of 54 (Grabe et al., 2015) and 58 (Task et al., 2020) glomeruli. We have refrained from naming glomeruli in Ae. aegypti at this time because we believe that a more stereotyped anatomy will emerge as new genetic lines are generated that allow cell-type-specific labelling.

Answer 118

mproving the resolution, and increasing the dimensionality, of the common low dimensional and end point behavioral assay has the potential to increase the predictive validity of translational repellent and to increase the rate at which basic science findings are translated to the field.

Answer 119

It might, in Abdoo-Saboor: Additionally, these data demonstrate that the nature of the response when an animal withdrawals its paw might be a more reliable indicator of pain state than the number of times the animal lifts its paws to a given stimulus. In other words, paw withdrawal fre- quencies revealed great variation across the seven strains (Figure 1), whereas paw trajectory pat- terns to a given stimulus showed quite stereotyped responses among these strains (Figure 2).

Answer 120

The seven behavioral features we extracted from video each provide more useful information than paw withdrawal frequency alone. Nevertheless, the simplest way to score behavior is using a univari- ate pain scale derived from these behavioral features. To accomplish this, we used ordinal logistic regression to identify a univariate linear subspace of the seven behavioral features that best sepa- rates the four somatosensory stimuli: CS, DB, LP, and HP. We did this for two cases: first, restricting to just four features quantifiable in the pre-peak period (t < t*), and then for all seven features quan- tified during the post-peak period (Figure 4H and I, respectively). For both the pre- and post-peak paw features, the two no-pain stimuli (CS and DB) cover the same parts of the subspace and are largely indistinguishable. By contrast, the low and high pain conditions (LP and HP) clearly separate from the no-pain stimuli and also separate from each other in this univariate pain score.

Answer 121

The performance of the univariate pain score was evaluated by leave-one-out (LOO) cross-valida- tion for individual mice (Figure 5A), and by leave-one-strain-out for strains (Figure 5B). We com- pared the pre- and post-peak paw univariate pain scale classifications to a null model that assigns pain classes according to their probability in the training data, without reference to measured behav- ioral features. For prediction, CS and DB were treated as a single ‘no-pain’ class, while LP and HP were treated as a single ‘pain’ class, resulting in a binary classification: no-pain or pain (Figure 5— figure supplement 1).

Answer 122

hile this methodology for measuring pain in rodents is not fundamentally flawed, it lacks resolution – a limitation that can now be overcome with advances in videography and automated tracking. Here, by automatically tracking paw dynamics at sub-second speeds with high-speed vide- ography coupled with machine learning approaches, we reveal stereotyped trajectory patterns in response to innocuous versus noxious stimuli spanning genetically diverse mice. With an accurate pinpoint of the paw at high spatiotemporal resolution, a freely available software package we term PAWS automatically quantifies seven behavioral features that are combined to determine the mouse pain state.

Answer 123

Lima-Camarra: he field (Laranjeiras, Sergipe, Brazil) and laboratory (Rockefeller) populations were characterized for the presence of the Val1016Ile kdr mutation, associated with pyrethroid resistance, and locomotor activity. Repellency bioassays were performed to assess the response of the mosquitoes to human odor by exposing them to 10% DEET applied to the skin in ethanol. Samples from the field population showed higher frequency of the kdr mutation, 21.9% homozygous and 21.9% het- erozygous, greater locomotor activity and greater sensitivity to DEET than the laboratory population. These results suggest increased sensitivity to DEET in field populations and a possible interaction between insecti- cide exposure and sensitivity to DEET.

Answer 124

Since the introduction of yellow fever (1685), dengue (1845), chikungunya (2014), and Zika (2015) arboviruses, epidemics are re- corded in different regions of Brazil (Zanotto et al. 2018). Urban yellow fever is considered eliminated since 1942, but the recent virus circulation through the Southeastern Region in the second half of 2017 have caused the biggest wild epidemic in the last 80 yr (Possas et al. 2018). Despite dengue epidemics are increasing in time over the last decades, the challenging neurological problems in newborns associated with Zika virus and rheumatic sequelae of chikungunya virus, national policies are still based on the same standard strategies to Aedes aegypti (Linnaeus, 1762) control as house survey, use of larvicidal products and ultra-low volume (UBV) nebulization.

Answer 125

Due to these control policies, mosquito populations are under high pressure of insecticides and a number of studies have shown Ae. aegypti resistance to the groups of insecticides used to vector control in Brazil, such as organophosphates (Macoris et al. 1999, La Corte et al. 2018) and pyrethroids (Macoris et al. 1999, Luna et al. 2004, Linss et al. 2014, Liu 2015). In addition, the use of domestic insecticides increases the resistance to these products, especially to the pyrethroid (Gray et al. 2018). More recently, changes in the sus- ceptibility of Ae. aegypti to the larvicide pyriproxyfen (currently in use) have also been reported (Campos et al. 2020, Carvalho et al. 2020)

Answer 126

The main mechanisms of insecticide resistance involve structural changes in target sites, in the case of pyrethroids mutations in the voltage-gated sodium channel gene, known as knockdown resistance (KDR), and metabolic resistance due to the increased insecticide de- toxification capacity mediated by enzymes such as esterases and multi-function oxidases. These two mechanisms modify vector performance in terms of physiologic, reproductive and neural functions.

Answer 127

Among reported consequences of Ae. aegypti pyrethroid resistance are fitness change (Brito et al. 2013, Viana-Medeiros et al. 2017) increased locomotor activity (Brito et al. 2013, Nakazato et al. 2021) and decreased re- sponse to spatial repellents (Wagman et al. 2015, Amelia-Yap et al. 2018). Voltage-gated sodium channels are reported to be implicated in the electrical message from the olfactory receptor neuron to the central nervous system (Zwiebel and Takken, 2004) so that KDR mutations are likely to affect response to olfactory stimulus. In fact, the pyrethroid resistant Ae. aegypti Puerto Rico strain was less re- sponsive to several kinds of repellents than the susceptible Orlando strain (Yang et al. 2020). Andreazza et al. (2021) confirmed cross- resistance between KDR resistance and tolerance to transfluthrin in Rockefeller (ROCK) strain, but failure to demonstrate tolerance to N,N-diethylmethylbenzamide (DEET).

Answer 128

As resistance to pyrethroids has been associated with a high fitness cost for Ae. aegypti (Brito et al. 2013), a resistance-reversal trend would be expected some generations after discontinuation of the selective pressure (Garcia et al., 2019). However, as pyrethroid use remains high in domestic applications and commercial fumigation services (Clayton and Sander 2002, Diel et al. 2003), resistance is expected to persist in field populations, as observed in our study

Answer 129

No. Studies have shown that in populations resistant to pyrethroids, organophosphates, and carbamates, the activity and number of detoxifying enzymes of the P450 enzyme complex may be changed be- cause of overexpression of the genes encoding these enzymes (Djouaka et al. 2008, Bonnet et al. 2009, Liu 2015). Changes in monooxygenase levels and overexpression of genes encoding these enzymes have been found in resistant populations. Bonnet et al. (2009) demonstrated that cytochrome P450 is responsible for the increased toxicity of DEET and for the synergistic effect between DEET and propoxur. Although the mechanisms behind this finding remain unclear, there is growing evidence for the association between cytochrome P450 enzymes and DEET activity (Corbel et al. 2009, Ramirez et al. 2012, Koloski et al. 2019) as well as the synergistic effect between DEET and various classes of insecticides (Bonnet et al. 2009, Pennetier et al. 2009, Faulde and Nehring 2012, Abd-Ella et al. 2015).

Answer 130

There is a laboratory strain of Anopheles gambiae that was susceptible to insecticides but only weakly repelled by DEET, whereas other strains of this species that were resistant to pyretrhoids were repelled by DEET.

Answer 131

It is a natural volatile and non-volatile substance involve in the intra and or interspecific communication between organisms.

Answer 132

Single-walled (basiconic or trichoid) sensilla. ORCs that respond to compounds such as ammonia, short chain carboxylic acids and amines are housed in double-walled (grooved peg and coeloconic) sensilla (Pappenberger et al., 1996; Diehl et al., 2003; Benton et al., 2009; Hussain et al., 2016) and do not express ORs but instead IRs. The IRs form ionic channels activated by ligands (Benton et al., 2009) and are expressed with one or two broadly expressed co-receptors different from ORCO

Answer 133

For instance, different strains of the European corn borer (Ostrinia nubilalis) are attracted to precise pheromone blend ratios (Klun et al., 1973). Similarly, different species of Yponomeuta moths, which feed on the same host and share the same three pheromone constituents, are reproductively isolated due to differential attraction to species-specific blend ratios (Löfstedt et al., 1991). Similar findings were also reported on aphids (Dewhirst et al., 2010) and plant bugs (Byers et al., 2013). While the importance of ratios is crucial for the design of trap lures, the neural mechanisms underlying this phenomenon just began to be understood

Answer 134

In moths and cockroaches, information about the female sex pheromone is processed by a small number of male-specific AL glomeruli forming a distinct structure, the macroglomerular complex (MGC; e.g., Boeckh and Boeckh, 1979; Hildebrand et al., 1980). Although the MGC sub-system of moths is distinctive and particularly large, the synaptic organization and structure of its constituent glomeruli is akin to that of the rest of the AL glomeruli. In some moth species, each MGC glomerulus processes a cognate pheromone component (e.g., Heliothis virescens; Berg et al., 1998), but in other species multiple components are encoded in the same MGC subcompartment

Answer 135

Because only these two components (out of eight total) are required to elicit odor- induced orientation behaviors in males (Tumlinson et al., 1989), this provides a simple binary system to investigate the neural mechanisms mediating pheromone processing, including blend ratio processing. When males are stimulated with the pheromone blend, two distinct populations of ORCs are specifically activated by those two essential components, one evoking excitatory responses in Cumulus projection neurons (cPNs) and the other in Toroid projection neurons (tPNs; Kaissling et al., 1989; Hansson et al., 1992; Hildebrand, 1996; Heinbockel et al., 1999; Lei et al., 2002). Additionally, recent findings suggest that cPNs and tPNs correlate their synaptic output to signal the presence of the pheromone blend (Lei et al., 2013; Martin et al., 2013). In principle, the odor-evoked spiking activity of cPNs and tPNs could serve to report the chemical identity and concentration of each blend component. However, since their outputs converge in the same regions in the protocerebrum (the delta region of the lateral horn and the mushroom body calyces), the relative timing of input spikes from cPNs and tPNs in postsynaptic neurons may have a physiological effect, that is, coincident spikes would evoke a stronger response in postsynaptic neurons than sequential spikes, allowing the representation of an odor mixture as a single odor object (see also Section Effects of Background Odor).

Answer 136

Indeed, using simultaneous dual-electrode intracellular recordings, Lei et al. (2002) showed inter- and intra-glomerular spike synchrony among PNs in response to pheromone blend stimulation. Odor-induced interglomerular synchrony in the AL was also reported in cockroaches using voltage-sensitive-dye imaging methods, suggesting that the synchrony code operates at a broad spatial scale (Watanabe, 2012). Moreover, experiments that simultaneously recorded neuronal activity across the glomerular array in M. sexta showed that neurons with the most similar odor response profiles produced the highest degree of coincident spikes (Lei et al., 2004). These results support the notion that PNs may use a correlative neural code. Further, it has been shown that spike coincidence in M. sexta AL neurons is modulated by the pheromone blend ratio. Behaviorally, the moths respond best to the mixture of the two essential pheromone components at the naturally occurring 1:2 ratio, and deviations from this ratio deteriorate blend attractiveness (Martin et al., 2013).

Answer 137

The mechanisms determining spike correlations are unknown, but balanced inhibition may be involved. Upon pheromonal stimulation, both PNs and LNs are activated, with cPNs and tPNs excited by their cognate pheromone constituents and reciprocally inhibited through GABAergic LNs (Lei et al., 2002). LNs likely respond in a dose-dependent manner, allowing the inhibitory effect exerted onto PNs to be modulated by the relative proportion of the blend constituents. Moreover, the degree of spike coincidence between PNs is positively correlated with the strength of the inhibitory input onto those PNs (Lei et al., 2002). Similarly, in the AL of cockroaches, GABAergic LNs also mediate synchronization of PN outputs (Watanabe, 2012). Thus, balanced lateral inhibition is a plausible mechanism by which stimulation with a pheromone blend of optimal ratio can produce the highest degree of correlated spikes in PNs.

Answer 138

The odor-evoked spikes of PNs innervating a particular glomerulus DA1 are highly correlated and provide converging input to their target neurons in the lateral horn.

Answer 139

The constitutens ratios

Answer 140

Yes, Culex quinquefasciatus gravid females, which are vectors of filariasis and West Nile Virus (among others), are attracted to a pheromone released from maturing eggs in conjunction with an indole compound derived from grass infusions (Mboera et al., 2000; Logan and Birkett, 2007), and these components evoke electrophysiological activity from antennal ORCs

Answer 141

Filariasis and West Nile Virus. Culex mosquitoes are major vectors of pathogens including the human filarial nematode, Wuchereria bancrofti, and arboviruses such as St. Louis encephalitis, Japanese encephalitis, Venezuela equine encephalitis, Western equine encephalitis and West Nile virus.

Answer 142

Yes, depending on its concentration. This has been shown for trans-2-hexenal in cockroaches and in Rhodnis prolixus.

Answer 143

1) Insects usually respond to specific mixtures of host odorants, even when they include ubiqutitous odorants. 2) Even when some cosntituents of those mixtures are essential to evoke a behavioral response, in some cases certain components could have redundant roles and therefore could be removed without decreasing attraction 3) Moreover, key components could be replaced without affecting attractiveness.

Answer 144

For instance, the encoding of odor mixture identity involves synchronous firing of PNs throughout the activated glomeruli, which may serve to “bind” the components of the odor mixture (Riffell et al., 2009a,b). In addition, stimulation with an odor mixture can evoke a glomerular activation pattern which is different from that evoked by the summation of the activity patterns evoked by each component (see below).

Answer 145

Interestingly, it has been proposed that just a few (sometimes just three) key components of an odor blend are sufficient for reliable host recognition, even when the insects can detect a higher number of host odorants

Answer 146

CO2 is a food and/or oviposition host cue used by some herbivorous and hematophagous insects (Guerenstein and Hildebrand, 2008). Glomerulus-specific CO2 PNs in the AL of M. sexta can follow high frequency CO2 pulses, suggesting that these PNs report information about long-distance CO2 cues (Guerenstein et al., 2004a). This idea is also supported by the finding that nectar-rich flowers emit relatively high levels of CO2 (Guerenstein et al., 2004b). In fact, foraging moths use floral CO2 as a long-distance cue to find those flowers (Thom et al., 2004; Goyret et al., 2008).

Answer 147

Odor mixtures are thought to be represented in the insect brain as single “odor objects,” so that the unique mixture identity prevails over the information about its constituents (Lei and Vickers, 2008; Wilson and Sullivan, 2011; Stierle et al., 2013). When odor baits (usually odor mixtures) are used in the field for insect monitoring and control, they are necessarily presented against an odorous dynamic background (another odor mixture/s). Background odors can either be irrelevant, “mask” the target odor (making it unrecognizable), or can enhance the response to a target odor. This idea is also supported by experiments in honeybees, in which odorants presented simultaneously (simulating components of a single odor source) were represented as a single object, while odorants presented with an inter-stimulus delay were represented separatel

Answer 148

A particular constituent of the volatile background, CO2, also affects the behavior of at least some insects (Guerenstein and Hildebrand, 2008). Information about this odor cue is processed as information about other odors, while the background level of CO2 is simultaneously encoded (Guerenstein et al., 2004a). In hematophagous insects this cue is used to detect and find vertebrate hosts (e.g., Geier et al., 1999b; Barrozo and Lazzari, 2004b), while in moths it is used to detect and find oviposition sites and nectar resources (Stange, 1997; Thom et al., 2004; Goyret et al., 2008). While those CO2 sources evoke clear responses from the CO2 ORCs at natural CO2 background levels, higher CO2 background levels interfere with those responses

Answer 149

In mosquitoes, an elevated CO2 background impedes take-off and source contact by masking the stimulus signal (Majeed et al., 2014).

Answer 150

“a chemical that acting in the vapor phase prevents an insect from reaching a target to which it would otherwise be attracted."

Answer 151

a product causing the insect “to leave the prospective host, with true behavioral repellency involving avoidance of the source of the repellent material, whether placed on the prospective host or near it”

Answer 152

topical repellents are usually applied onto the skin offering individual protection, while spatial repellents volatilize into the air, creating a vector-free space which provides protection for multiple individuals (Achee et al., 2012).

Answer 153

For centuries humans have used diverse parts of plants to repel biting insects (Moore and Lenglet, 2004). Among these so- called “botanical repellents,” various species of basil (Ocimum spp.) have been historically used to repel mosquitoes. In addition, oil extract from the leaves of neem (Azadirachta indica) has also been used as a personal mosquito and sandfly repellent (Yarnell and Abascal, 2004). Other botanical insect repellents include the oil from leaves of citronella (Cymbopogon nardus), palmarosa (C. martinii martinii), lemongrass (C. citratus), and Eucaliptus (Eucalyptus spp.). The active components of these botanical repellents are often unknown although citral, a major ingredient in volatiles from lemongrass oil, and p-menthane-3,8- diol, from lemon eucalyptus, have repellent effects on a variety of mosquitoes

Answer 154

In a way analogous to DEET smell and repel effect in C. quinquefasciatus.

Answer 155

These strategies divert away from a valuable source (push) into an attractant (pull)

Answer 156

1) DEET, picaridin, IR3535 activated the odorant receptor CquiOR136 of the southern house mosquito. 2) Ephyis and behavioral assay showed that reducing OR136 transcript levels led to significant decrease in ephys response and a complete lack of repellency. 3) CquiOR136 was activate by methyl jasmonate, a repellent derived from jasmonic acid in the signaling pathway of plant defenses.

Answer 157

It is very low. 5.6 × 10−3 mm Hg at 20 °C

Answer 158

Picaridin and methyl jasmonate share similar structural motifs, which are essential for activity. And methyl jasmonate is a repellent for the southern house mosquito and ticks.

Answer 159

Jasmonic acid is a nonvolatile compound and therefore, unlikely to repel at distance, whereas methyil jasmonate has the ideal vapor pressure for a repellent and is released by injured plants and has been demonstrated to be a repellent.

Answer 160

Increase the signal:noise ratio. Adapt to different environments. Extract salient stimuli and ignore irrelevant stimuli. Format the signals in a way that allows for memory formation. Evaluate an odor valence according to the current motivational state.

Answer 161

Projections neurons are either uniglomerular or multiglomerular. Most uniglomerular PNs target the MB and also the lateral protocerebrum and are excitatory and most multiglomerular PNs target the LP only and are inhibitory.

Answer 162

The LP can be described as being more complex than the MB, in that there are no easily identifiable structures, or as being less complex, in that there are fewer neurons

Answer 163

These neurons release biogenic amines (octopamine, serotonin) and influences physiological properties of the target neurons in the relevant structures.

Answer 164

When two substances that use the same interaction site on the recpetor are mixed, the two substance compete for binding.

Answer 165

Banana volatiles contain one of the best ligands for OR22a, ethyl butyrate, but also a larger amount of a weak OR22a ligand, isoamyl acetate (Jordan et al., 2001). A detailed analysis of the response properties of OR22a to banana-like mixtures revealed that the weak ligand, isoamyl acetate, accounts for most of the banana response, rather than the strong ligand, ethyl butyrate (M€unch et al., 2013). In other words, within the mixture this receptor appears to be anosmic to its own better ligand, which is masked by another, weaker ligand! For the olfactory system as a whole this means that mixture processing may be perceptually simpler than previously thought, if it is true that the response properties of ORs lead to masking of the effects of substances in the mixture. Thus, complex mixtures from a chemical point of view may turn out to be equivalent to simpler mixtures from a perceptual point of view.

Answer 166

The increase in signal:noise ratio. Nose originates from two sources. The first is the basic noise in each cell, i.e. the occurrence of spikes that are not related to an odorant molecule binding to a receptor. This noise is present all the time, given that ORNs typically have background activity already in the absence of stimulation. The second is the noise in the response, i.e. a variability. The first is a noise constant that can be added to the ORN response and the second is related to the response magnitude. In both cases, the noise in one ORN is statistically independent from the noise in another ORN. As a consequence, averaging responses across recep- tor cells lead to an increase of the signal : noise ratio, as illustrated in Fig. 2.

Answer 167

The input synapse of ORNs to PNs is highly non-linear (Olsen et al., 2010). At low spiking frequencies of ORNs, a small change in the ORN firing rate leads to a large change in PN firing rate, whereas this transfer function is more shallow at higher frequencies. Thus, the transfer function of the ORN–PN synapse follows a satu- ration curve that increases the information (i.e. the dynamic differ- ences) at low response levels, at the expense of loss in dynamic range at the higher response range.

Answer 168

The ORN–PN synapse does not only have a steep response curve, it also has a relatively long integration time, which is important when stimuli have a low concentration. Integrating over time allows for small input signals to have an effect on PN responses, because temporal summation is increased

Answer 169

This step of lateral inhibition shifts the response range of PNs, and thus increases the contrast of the across-glomeruli signal. Indeed, a computational test modeling MB KCs showed that lateral inhibition improved the capacity of a linear decoder to extract the pattern identity

Answer 170

First, the global activity factor (i.e. the input to LNs) correlates well with total input activity (in the experiments by Olsen et al. (2010), these were measured as electroantennograms). Therefore, in my proposed network (Fig. 1), I assume that these LNs receive direct input from ORNs. Second, these LNs do not inhibit the PNs directly, but the presynaptic terminal onto the PNs (Olsen & Wilson, 2008; Root et al., 2008). At high concentrations, the inhibitory lat- eral network pushes activity down (Das et al., 2011), enhancing the interglomerular contrast (Silbering & Galizia, 2007; Silbering et al., 2008) and flattening the dose-response curves (Sachse & Galizia, 2003). The net result is a network that efficiently and quickly adapts to the overall sensory input to the system. Thus, a global nor- malisation network of this kind can create responses that look like ‘disinhibitory’ responses. Similarly, this network creates PN responses that are, on average and across glomeruli, delayed as compared with LN responses, in concordance with experimental findings

Answer 171

When recording from PNs across glomeruli for long time periods without any olfactory stimu- lus it becomes apparent that this spontaneous activity is controlled by a network of LNs, as there is no preferential pattern of activity, as shown by a principal component analysis across glomeruli (Galan et al., 2006). What is the functional significance of this? In many sensory systems, the neurons are kept very close to their activity threshold, in order to increase their sensitivity to even minute input. This is termed the spring model

Answer 172

In our previ- ous work (Sachse & Galizia, 2006) we postulated a push–pull mech- anism; PNs are spontaneously active [as shown, for example, by their tendency to respond with excitation at the end of olfactory stimuli to which they do not respond (rebound excitation as release from lateral inhibition)], and this activity drives inhibitory LNs that downregulate all PNs across glomeruli. As PNs become more silent, LNs become less active, inhibition on PNs is reduced, and PNs start to fire again. Such a network of feedback inhibition creates the desired ‘spring model’ (or stochastic resonance) characteristic. It is also a network that has a propensity to oscillate when the system is driven by strong input.

Answer 173

Thus, a biased implementation of lateral processing exists. In Dro- sophila, where the morphology of LNs has been studied systemati- cally (Chou et al., 2010), most LNs branch across all glomeruli, but a substantial part omits some glomeruli, or has a patchy innervation pattern. Does this selective pattern have a functional property? It appears that, in the case of Drosophila, glomeruli with narrower tuning properties are less innervated (Chou et al., 2010). Narrow tuning also means less common activity with other glomeruli, and therefore possibly less necessity to engage in lateral inhibition.

Answer 174

We know, however, that, as a first approximation, the inhibitory connections between glomeruli follow a function similar to a Mexican hat, i.e. glomeruli tend to inhibit other glomeruli that have an overlapping response profile (Linster et al., 2005). Functionally, this creates a sharpening that in image processing corresponds to an unsharp-mask filter (Fig. 6). The result is an odor representation where the across-odor contrast is stronger than in the ORN input, a situation that is probably partic- ularly important when processing odor mixtures. Indeed, odor mix- tures show particularly high occurrences of across-glomeruli inhibitions

Answer 175

Mushroom body: odor identification Lateral protocerebrum: odor evaluation

Answer 176

In the AL, each glomerular channel from the AL is attributed a value along a valence scale, and the LP computes a global valence. When two odors are compared for their valence, this comparison is highly correlated with the similarity of their across-glomerular patterns (either as Euclidean distance in a multidi- mensional space, or as their angular distance, which is the corre- spondent, intensity-invariant measure)

Answer 177

This view of the function of the LP is essentially binary; each odor can be either ‘good’ or ‘bad’, consistent with observations in humans that pleasantness is the most important (although not the only) descriptor of odors (Khan et al., 2007). In fact, in most cases, the behavioral response of an animal is mostly unidimensional – either approach (positive) or withdraw (negative); either copulate (‘positive’) or reject (‘negative’); either lay an egg (‘positive’), or search another site (‘negative’). The ‘hardwired’ LP is consistent with this view; ePNs from ‘positive’ glomeruli have strongly excit- atory input to LP neurons, and ePNs from ‘negative’ glomeruli have strongly inhibitory input to the LP neurons (most likely via interca- lated inhibitory neurons, not shown in Fig. 1). The feedforward inhibitory input from the AL to the LP is module-specific, i.e. selec- tive for food odors or pheromones (Liang et al., 2013; Fisek & Wil- son, 2014). Because the readout maybe unidimensional to a large degree, some odors code in a way that resembles a ‘labeled line’ under experimental conditions (see below).

Answer 178

Most DEET formulations have a short duration of action, which is a serious hindrance for military use.

Answer 179

Yes, Syed (2011) demonstrated that Drosophila is repelled by DEET, and by IR3535 and picaridin in a choice assay that requires the olfactory system (endpoint). But they do not specify the concentration.

Answer 180

Syed (2011) working in Drosophila: During this mapping, at least three sensilla of each type (basiconic, coeloconic, and trichoid) were challenged with these insect repellents. Although we did not find a single ORN sensitive to DEET or IR3535, one neuron housed in ab3 sensilla responded to picaridin with high sensitivity (threshold 0.1 mg, source dose) (Fig. 2). Based on the large spike amplitude (Fig. 3), the picaridin- sensitive neuron was identified as ab3A, which is known to harbor DmOr22a/b [18].

Answer 181

Syed (2011) working in Drosophila: Next, we performed single unit recordings from all olfactory sensilla in the maxillary palps and found an ORN in the basiconic sensilla pb1 that responded to DEET (Fig. 4) in a dose-dependent fashion (Fig. 5). Surprisingly, these sensilla showed apparent higher sensitivity (lower threshold) to DEET than sensilla previously identified in the Southern house [20] and the yellow fever [21] mosquitoes (Fig. 6). The same ORN responded to IR3535 and picaridin in a dose responsive manner.

Answer 182

Although the ‘‘empty neuron’’ has been demonstrated to be an invaluable system for testing/ deorphanizing antennal ORs from the fruit fly [27] and other insects [29], it is not entirely surprising that a transplanted receptor does not perform well in the system [27,29]. After all, odorant- binding proteins, odorant-degrading enzymes and other olfactory proteins are not transplanted along with test ORs.

Answer 183

Syed working in Drosophila: Although it was not possible to unambiguously correlate ORN excitation vis-a`-vis behavior as repellence was not impaired in flies with palps surgically removed (as well as those with antennae surgically excised), the discovery of an OR directly stimulated by DEET and other insect repellents and its ORN paves the way for practical applications in repellent R&D.

Answer 184

This study further showed that, although larvae containing only Or1a- or Or49a-functional ORNs did not chemotax toward any tested odors, larvae containing both an Or42a-functional ORN and either an Or1a-functional ORN or an Or49a-functional ORN responded to a somewhat different subset of odorants than did larvae containing only an Or42a-functional ORN. These data supported a model in which the larval behavioral response depends on the combined input from multiple odor receptors. The results illustrate the value of a systematic analysis of the role of the entire larval receptor repertoire in generating behavior.

Answer 185

Kreher_Carlson (2008): Receptors varied a great deal in the number of odorants that excited them strongly. At one extreme, Or67b was strongly excited by eight odorants (30% of the panel), and Or42a and Or85c were strongly excited by seven at the higher concentration. At the other extreme, four of the 21 receptors were not strongly excited by any odorants. The receptors showed a smooth distribution between these two extremes

Answer 186

Kreher_Carlson (2008) working on Drosophila larvae: Odorants of diverse chemical classes elicited strong responses of the same response mode, i.e., the strongest attractants (E2-hexenal, propyl acetate, 2-heptanone) are an aldehyde, ester, and ketone, respectively. Likewise, the repellents included a terpene, a ketone, an alcohol, and aromatics.

Answer 187

The odor masking paradigm is based on the behavioral paradigm shown in Figure 3A. Responses to a point source of odorant A are measured in the presence of a background of odorant B; odorant B is uniformly distributed across a filter that covers nearly the entire lid of the Petri dish in which the assay is conducted. We then determine whether the background of odorant B decreases the response of the animals to odorant A. This paradigm was used in a previous study of Drosophila larvae (Rodrigues, 1980), and a very similar paradigm has been used in C. elegans (L'Etoile and Bargmann, 2000, Wes and Bargmann, 2001): if the worms responded to odor A in a background of B, then they were inferred to be able to discriminate A from B; if they cannot discriminate A from B, then a background of A was expected to block the response to B.

Answer 188

The ability to identify odors in a background of other odors has also been described as odor segmentation

Answer 189

We found that at least one odor masked the response to a point source of each of the five tested odorants. When ethyl butyrate was used as the point source, ethyl acetate masked the response as potently as did ethyl butyrate itself. Reciprocally, among the five odorants other than ethyl acetate that were used as a point source, ethyl butyrate most potently masked response to ethyl acetate (Figure 5B).

Answer 190

The more distant two odors are in the odor space the less they mask (Inverse correlation)

Answer 191

Interestingly, the response of Or42a−Or42b+ mutants declines and becomes repellent as the concentration increases. One possible interpretation, among others, is that hyperactivation of Or42b, which is very sensitive to ethyl acetate, triggers a repulsion circuit but that in wild-type this circuit is overridden or suppressed by activation of Or42a. In any case, this result is consistent with the existence of nonlinearity in the olfactory circuitry and the possibility of interactions among ORNs in the larval antennal lobe via lateral connections, which have been documented in the more complex olfactory system of the adult fly.

Answer 192

Kreher_Carlson (2008) Drosophila larvae: As an initial step, we summed the total number of action potentials elicited by each odorant from all 21 receptors of the receptor repertoire and plotted each sum against the response index obtained for that odorant. Although we had not expected to find a simple relationship, we found a modest but clear correlation between the total spike input and the behavioral response: greater spike input correlated with greater RIL (Figures S5A and S5B). (RIL is used for statistical rigor; the RI was expressed as a log-odds ratio, i.e., logit transformed to yield RIL, as described in Experimental Procedures, to best satisfy the normality assumptions of the analysis. A plot of RI versus total spike input is nearly superimposable.) The correlation was observed when we plotted the total number of spikes elicited by a 10−2 dilution of each odorant (R2 = 0.33, p = 0.002) or by a 10−4 dilution (R2 = 0.28, p = 0.006). We found comparable correlation coefficients for attractants and repellents when considered separately, in the case of both concentrations (data not shown). We were surprised to find that the responses of small subsets of receptors were powerful predictors of behavioral response. Remarkably, 81% of the behavioral variation could be explained by the activity of only five receptors (Or42a, Or45a, Or74a, Or82a, and Or85c), as follows.

Answer 193

Kreher_Carlson (2008): We noticed a striking relationship between repellency and inhibitory responses across the repertoire: of the three odors that elicit the greatest number of inhibitory responses from the receptors of the repertoire, all are repellents. The 26 odors of our panel elicited between 0 and 8 inhibitory responses from the 21 receptors when tested at a 10−2 dilution (Figures 1A and S2A). The two odors that elicited eight inhibitory responses were 2-methyl phenol and fenchone, which are among the strongest repellents; the one odor that elicited seven inhibitory responses was 1-nonanol, also a repellent (Figure 3B and Cobb et al., 1992). The one odor that elicited six inhibitory responses, moreover, was 4-methyl phenol, one of the weakest attractants. Overall, the mean number of receptors inhibited by the repellents was 5.8, whereas only 2.9 inhibitory responses were elicited by nonrepellents (p < 0.01, Mann-Whitney test). Heretofore we have used a stringent definition of inhibition: a reduction in response to <50% of the spontaneous rate. As another test of the relationship between repellency and inhibition, we adopted a less stringent criterion: that the mean response rate is less than the mean spontaneous rate. Using this criterion, we found that repellents inhibited 10.0 receptors versus 5.3 receptors for nonrepellents

Answer 194

We first show that negative deviations from baseline can exist in calcium imaging of neuronal activity. Then, we use simulated data to test three popular algorithms for image analysis, CaImAn, suite2p, and CellSort, finding that suite2p may be the best suited to large datasets. We also tested the spike inference algorithms included in CaImAn, suite2p, and Cellsort, as well as the dedicated inference algorithms MLspike and CASCADE, and found each to have limitations in dealing with inhibited neurons. Among these spike inference algorithms, FOOPSI, from CaImAn, performed the best on inhibited neurons, but even this algorithm inferred spurious spikes upon the return of the fluorescence signal to baseline. As such, new approaches will be needed before spikes can be sensitively and accurately inferred from calcium data in inhibited neurons. We further suggest avoiding data analysis approaches that, by assuming non-negativity, ignore inhibited responses. Instead, we suggest a first exploratory step, using k-means or PCA for example, to detect whether meaningful negative deviations are present. Taking these steps will ensure that inhibition, as well as excitation, is detected in calcium imaging datasets. (Vanvelleghem_Scott)

Answer 195

One interpretation of these results is that odors that are close in odor space elicit similar activity patterns that are difficult for the system to resolve. Thus, the signal of the point source is lost in the background of the masking odorant because they elicit similar firing patterns. Another explanation is crossadaptation: if the point source odor and the background odor activate the same receptors, then adaptation to the background odorant might prevent these receptors from signaling the presence of the point source

Answer 196

We were nonetheless surprised not only that a linear model was so powerful but also that such predictive power can be achieved with so few receptors. Two of the receptors in the model, Or42a and Or85c, are broadly tuned and respond most strongly to subsets of odorants that are largely complementary. These odorants are attractants, and the coefficients of Or42a and Or85c in the model are, correspondingly, positive. By contrast, Or82a is excited only by geranyl acetate, and Or82a is the only receptor in the repertoire that is excited by geranyl acetate, presumably explaining its value in the model. Consistent with this explanation, its coefficient in the model is negative, indicating that sensory input via this receptor contributes to the repellent response elicited by geranyl acetate. Likewise, of all 21 receptors, Or74a is the receptor that responds most strongly to the repellent 1-nonanol, and its coefficient in the model is negative as well. Thus, it is possible that the Or82a and Or74a receptors activate a repulsion circuit.

Answer 197

It is possible that receptor coexpression may allow an ORN to perform simple logical operations, such as an “and” function that signals the coincidence of two odorants.

Answer 198

A simple logic to the identification of insect repellents from a rapid physiological screen of receptor activity could thus be of value in the control of insect pests

Answer 199

A priori, this correlation is consistent with two mutually compatible interpretations. First, inhibitory responses may contribute to a repulsion response by virtue of a general reduction in overall activity of the receptor repertoire. Second, a repulsion circuit may be triggered by the specific patterns of receptor activity. For example, all odors that are repellents at a 10−2 dilution inhibited Or13a and Or42b, suggesting the possibility that one or both receptors are elements of a repulsion circuit.

Answer 200

Pham_Ray (2015) Drosophila: We investigated known innate avoidance pathways from five species at different evolutionary distances: D. melanogaster, D. yakuba, D. suzukii, D. pseudoobscura and D. virilis. Surprisingly, only DEET shows strong repellency across all species, whereas CO2, citronellal and ethyl 3-hydroxybutyrate show only limited conservation.

Answer 201

The CO2 receptor is comprised of two 7-transmembrane proteins Gr21a and Gr63a, which are housed in the ab1C neuron on the D. melanogaster antenna. We found that the amino acid sequences of both Gr21a and Gr63a are extremely well conserved in the D. suzukii genome (99% and 94%, respectively). In order to test whether the functional expression of the receptors occurs, we used single sensillum electrophysiology on the D. suzukii antenna (N = 5–6). Our results indicate that an ab1C-like neuron in D. suzukii is present and is in fact more sensitive to CO2 than D. melanogaster across different concentrations [this is not the same sensiulium that responded to Deet in Syed and Leal (2011)]

Answer 202

Leal (2018) Culex quinquefasciatus: Our initial test dose (1%) is close to what is found in many commercial products in the US and overseas, e.g., OFF! Familycare® unscented, Cutter Skinsations®, Cutter All Family®, all 7% DEET (US); Super Repelex®, 6.7% DEET; Xo Inseto!®, 7.5% DEET (Brazil), just to cite a few.

Answer 203

in behavioural tests with 5- to 7-day-old host-seeking females from the Davis colony, DEET at a 1% dose provided significantly higher protection (n = 12; P = 0.0002, unpaired, two-tailed t-test) than picaridin provided at the same dose (Fig. 2). Similar results were observed with a laboratory colony initiated from mosquitoes collected in Recife, Brazil, and maintained at FIOCRUZ-PE since 2009. Protection elicited by picaridin at a 1% dose against 5- to 7-day-old host-seeking females of the Recife colony were not significantly different from the protection observed with the Davis colony (Mann Whitney two-tailed test, P = 0.301).

Answer 204

Because picaridin was developed at the end of the last century, there have been many studies comparing DEET and picaridin formulations. A review of these efficacy tests21 concluded based on peer-reviewed literature that DEET at a concentration of 20% or greater had the greatest efficacy against Aedes mosquitoes, and that Culex mosquitoes are easier to repel, with all four repellents reviewed (DEET, picaridin, IR3535, and Citridora [p-menthane-3,8-diol]) providing good protection21. To the best of our knowledge, there were only two studies comparing DEET with picaridin in solutions rather than commercial formulations. One of these studies concluded that picaridin was significantly less effective than DEET in reducing Ae. aegypti bites22, whereas the other showed the two repellents were not significantly different for protection against Anopheles gambiae, but picaridin was 1.5x more potent than DEET for Ae. aegypti23

Answer 205

Both DEET and picaridin had somewhat lower protection against 5- to 6-day-old, host-seeking Ae. aegypti females (Fig. 3) than observed for Cx. quinquefasciatus of similar age and using repellents at the same dose (Fig. 2). Despite its lower protection against the yellow fever mosquito than the southern house mosquito, DEET at 1% was a significantly better repellent (protection, 80.5 ± 4.3%) against Ae. aegypti than picaridin (protection, 51.8 ± 8.5%) was at the same dose (n = 4–6; P = 0.018, Mann-Whitney two-tailed test)

Answer 206

Mosquitoes used for testing repellent efficacy in standard protocols must be nulliparous (never had a blood meal) and young, i.e., preferentially 5–7 days post-emergence17, or 5–10 days old16, according to WHO and EPA guidelines, respectively.

Answer 207

Although EIP for ZIKV is not yet known, considering a lower estimate (10 days) for dengue virus (DENV)24, mosquitoes in the wild are unlikely to be ZIKV vectors before 12 days after emergence (given that they do not feed for the first time until they are about 2 days old). Therefore, the most dangerous mosquitoes are old individuals that already had at least one blood meal. Our initial tests and those for commercial repellents have been performed with mosquitoes too young (5–10 days old) for virus transmission.

Answer 208

Zika could not change it. Leal found that albeit the mosquito infected with Zika showed a lower sensitivity to DEET this had more to do with their older age (they had to have at least one blood meal and gonotropic cycle) than the actual infection.

Answer 209

For a couple of hours in the backyard, a product containing 10 to 30% DEET should provide adequate protection. For a camping trip or a long hike, a 40 to 50% DEET preparation may be necessary. (Brown Hebert, 1997)

Answer 210

orco (+) neurons on the mosquito antenna were grossly localized to hair-like trichoid sensilla. Dendrites of IR8a neurons appeared confined to grooved peg sensilla on the antenna. Gr1 and orco neurons were found in the capitate peg sensilla on the maxillary palp. (Raji_Mcmeniman)

Answer 211

It codes for the pre-synaptic protein Bruchpilot.

Answer 212

Herre_Younger counted 41 whereas Raji and Mcmeniman counted roughly 63, 15 IR8a and 1 Gr1 glomerulus.

Answer 213

Yes, in the systematic reference for key for A. aegypti antennal lobe nomenclature Shankar and McMeniman determined that that 63 out of 80 glomeruli could be found in stereotipyical spatial positions based on synaptic labeling.

Answer 214

-(Raji and McMeniman) visualized orco+ neurons innervating the taste center of the insect brain known as the SEG.

Answer 215

CaMPARI is a calciummodulate photoactivatable ratiometric indicator to map patterns of activity in the antennal lobe. This genetically encoded ratiometric calcium indicator photoconverts from green to ren when simultaneously exposed to 405 nm light and high levels of calcium.

Answer 216

IR8a+ neurons are silent in response to either ligand alone (lactic acid or CO2) so Raji and McMeniman hypothesize that the binary synergism may occur via disinhibitory local circuitry operating between the CO2-sensitive glomerulus MD1 and axon terminals of these lactic acid-sensitive IR8a glomerulu in the antennal lobe.

Answer 217

- CO2 is detected by the largest unit of olfactory coding in the antennal lobe. -Synergistically, CO2 detection gates pre-synaptic calcium signaling in olfactory sensory neuron axon terminals that innervate unique antennal lobe regions tuned (IR8a) tuned to lactic acid.

Answer 218

1) This study characterized the responses of olfactory receptor neurons (ORNs) in different types of antennal olfactory sensilla in Ae. aegypti to 48 chemicals that exhibited repellent activity in various insect species. 2) Both excitatory and inhibitory responses were observed from ORNs in response to these chemicals and differential tuning properties were also observed among ORNs. 3) Remarkable excitatory responses were recorded from the ORNs in sensilla SST1, SST2, SBTI, SBTII, and LST2, while inhibitory activities were detected from a neuron in sensillum SST2 in response to several terpene/terpenoid compounds. 4) Moreover, the temporal dynamics of neuronal responses were found to be compound-specific and concentration-dependent. 5) Hierarchical cluster analysis and principal component analysis of the response to each compound across ORNs in seven types of olfactory sensilla in Ae. aegypti revealed that odor reception depended not only on chemical class but also specific chemical structure.

Answer 219

Interestingly, although camphor, eucalyptol, (−)-α-thujone, (−)-menthone, and (S)-(−)-perillaldehyde are structurally related, as shown in Fig. 2a and b, the temporal dynamics of the neuronal responses induced by these compounds in SST1 and SBTII ORNs were different. (Chen, Liu, Liu)

Answer 220

(Chen, Liu, Liu): Insects in a natural habitat typically experience a dynamic olfactory environment in which odors are encountered at varying concentrations. Thus, we also characterized the temporal firing activity of neuronal responses across serial dilutions. For example, eucalyptol elicited different temporal firing activities at two concentrations, with a more phasic response at high concentration (e.g.10−2 dilution) compared with a more tonic response at lower concentrations (e.g. 10−3 dilution) (Fig. 3b). However, eucalyptol and (S)-(−)-perillaldehyde at either a 10−2 or 10−3 dilution elicited prolonged responses in the ORNs of SST2 (inhibitory response) and SBTII (excitatory response) sensilla, respectively (Fig. 3b).

Answer 221

(Chen, Liu, Liu): To visualize relationships among compounds in the odor space, we carried out a hierarchical cluster analysis (Fig. 4a). Results demonstrated that compounds from the same chemical class tended to cluster together, though in no case was there a cluster that included all members of a class (Fig. 4a). Specifically, compounds with similar structures were tightly clustered together, such as eucalyptol, (−)-α-thujone and camphor (Fig. 2b and 4a). These results suggest that the chemical class is one but not the only feature that determines the response pattern of ORNs in Ae. aegypti.

Answer 222

- orco mutants are impaied in both honey and host odor attraction.

Answer 223

Oroc mutants are attracted to vertebrate hosts, but are impaired in their ability to discriminate between them.

Answer 224

To test the olfactory effect of DEET at close range, we used a host proximity assay that measures the effects of DEET over a distance of 2.5 to 32.5 cm (Fig. 5b). In this assay, a human arm treated with solvent or 10% DEET was placed 2.5 cm from the side of a screened cage

Answer 225

A repres- entative orco2/5 mutant mosquito is repelled within 60 msec of contact with DEET-treated skin

Answer 226

The fact that orco mutants retain very strong olfactory host attraction indicates that the first hypothesis cannot be correct. If the olfactory repellency of DEET acted solely to inhibit the OR pathway, DEET would not be an effective insect repellent. Instead, our results are consistent with the second or third hypotheses. Our genetic analysis of orco mutants indicates that either mechanism must overcome the strong baseline attraction to hosts in the presence of CO2 seen in orco mutants.

Answer 227

(Van Bruegel_Dickinson) 5-15 m

Answer 228

The attraction to this visual feature persisted through the entire length of the 3-hr CO2 presentation. During these exploratory bouts, the mosquitoes hovered near the visual object at a distance of approximately 3 cm.

Answer 229

In contrast to the female mosquitoes, males vigorously explored the visual feature in clean air (Figure 2D). In the presence of CO2, the males did not show any qualitative behavioral changes compared to their clean air responses and did not exhibit any evidence of plume-tracking behaviors. Thus, the influence of CO2 on the reaction to visual features appears to be a sex-specific behavior associated with blood foraging. ( Van bruegel and Dickison).

Answer 230

Many of the mosquitoes that approached the visual feature continued to explore the area for another 10 s or more without reencountering the plume (see Movie S1). These results indicate that attraction to visual features can be triggered by a brief prior exposure to odor and does not require simultaneous experience of the two cues.

Answer 231

Van Bruegel_Dickinson: Our estimates are necessarily conservative because our tracking system cannot reliably maintain the identities of individual mosquitoes over periods longer than 10–20 s.

Answer 232

Van Bruegel_Dickinson: Water vapor from rapidly evaporated perspiration has been attributed as another cue mediating host-seeking behavior in mosquitoes [12]. To investigate the possible role of water vapor on host localization in combination with visual and thermal cues, we placed a small petri dish containing a moist KimWipe over each glass pad in combination with the infrared pass filter that provides the visual cue. In this case, mosquitoes showed a significantly stronger response to the warm object at altitudes of 6–8 cm, rather than the narrow 2-cm region above the floor in which mosquitoes responded to the heat plume without H2O (p < 0.01) (Figure 3G). These results suggest that the secondary effect of increased humidity over a warm object may be a more important cue than the temperature of the object itself. This behavior would help mosquitoes differentiate warm radiant objects, such as dark rocks heated by the sun, from animals, which increase the humidity around them when perspiring

Answer 233

Van Bruegel_Dickinson: In our experiments, we deliberately created a simple continuous odor plume so that we could register it with the mosquitoes’ reactions. Under more natural conditions, however, CO2 would move with the wind in intermittent packets of high concentration interspersed with background air [24]. The intermittent structure of natural plumes will cause an animal to experience a brief puff of odor, and then nothing for seconds, or even minutes [24, 25, 26].

Answer 234

In our proposed scheme, the behavioral modules employed by mosquitoes to find a host are both independent and interacting. The modules are independent from one another in the sense that mosquitoes may bypass individual steps in the sequence. For example, if mosquitoes happen to fly near a warm object without having previously encountered CO2, they may still approach the object and land. The behavioral modules may also interact with one another indirectly. For example, the influence of CO2 on both arousal and visual feature attraction will greatly increase the probability that mosquitoes come close enough to a host to detect its thermal plume.

Answer 235

A mosquito’s perception of CO2 triggers a strong attraction to visual features A mosquito’s attraction to thermal targets is independent of the presence of CO2 Olfaction, vision, and heat trigger independent host-seeking behavioral modules Interactions among behavioral modules underlie multimodal sensory integration

Answer 236

-Synthetic repellents didnot activate Anopheles coluzzii ORs, picariding activate only at high concentrations. -Natural repellents strongly activated smallnumbers of ORNs in the Anopheles mosquito antennae at low concentrations. -The masking effect was concentration dpeendent. Makser repellents masked the activator (natural) repellent effects as well.mixing eugenol with DEET, IR3535, or picaridin strongly decreased the eugenol-alone olfactory response.

Answer 237

They diverged about 190 mya. (for context mice and humans diverged about 75mya)

Answer 238

They focus on just one segment of the antennae (11th segment)

Answer 239

Potte_Afify: mosquito antenna was tested sequentially with several odorants (OR ligands alone and mixtures of OR ligands with re- pellents). These repeated measurements might be correlated within the same animal, which violates two assumptions com- mon to many statistical models: independence and constant variance of outcomes. In addition, there could be an order effect whereby early measurements might affect subse- quent measurements. Therefore, we randomized the order of odorants tested and paired each OR ligand with its respective mixture; e.g., OR ligand X was always paired with (precedes or follows) the mixture of OR ligand X + repellent. In order to ac- count for potential correlation due to repeated measurements and non-constant residual variation, linear mixed effects regression models were used to model olfactory responses.

Answer 240

First, olfactory masking could occur at the odorant receptor level, whereby the repellent binds to an odorant receptor complex and prevents its activation by other odorants [11, 12, 18–20]. Second, olfactory masking might occur at the chemical level by which the repellent reduces the volatility of an odor, resulting in decreased neuronal responses [16]. To determine whether masking occurs at the odorant receptor level, we modified how the repellents and OR ligands were delivered to the mosquito antenna in our calcium imaging system.

Answer 241

In this setup, the odorants from the upper filter paper would pass by the lower filter paper as they travel toward the antennae. We found no repellent masking effect when the repellent was on the upper filter paper, but the response to 1-octen-3-ol was significantly reduced when DEET, IR3535, or picaridin were applied to the lower filter paper (Figures 5C, S6E, and S6F). This second setup mimics situations in which a masker repellent is applied to clothing, which may allow the activating OR ligand to mix with the repellent on their way toward the mosquito an- tenna. Nonetheless, the olfactory response in the non-mixed condition remained significantly higher than the response to 1-octen-3-ol when it was physically mixed with DEET, IR3535, or picaridin (Figures 5C, S6E, and S6F).

Answer 242

The chemical nature by which DEET (and the other synthetic repellents) chemically masks odors requires future investiga- tion. Nonetheless, the low volatility of DEET (vapor pressure 0.0017 mmHg at 25C) suggests it may contribute to this mech- anism, as mixtures with a low volatile odorant can reduce the overall volatility of the mixture (Raoult’s Law). To test this, we used three compounds with low vapor pressures similar to DEET (nerolidol, 0.001 mmHg at 25C; a-humulene, 0.008 mmHg at 25C; and farnesene, 0.01 mmHg at 25C; http://thegoodscentscompany.com) in mixtures with 1-octen- 3-ol (vapor pressure 0.531 mmHg at 25C; http://thegood scentscompany.com). The three compounds (at 30%) masked the response to 1-octen-3-ol to differing levels (data not shown). Interestingly, farnesene by itself elicited strong neuronal responses in some antennal neurons and yet acted as a masker for 1-octen-3-ol responsive neurons (data not shown). This suggests that low volatile odorants can elicit antennal neuronal responses detectable by calcium imaging. In addition, these results suggest that low vapor pressure chemicals can generally mask odors and can be considered candidates for new masker repellents

Answer 243

We describe the molecular effects of 10 insect repellents and a pyrethroid insecticide with known repellent activ- ity on two highly specific Aedes aegypti (Diptera: Culicidae) ORs, AaOR2 + AaOR7 and AaOR8 + AaOR7, exquisitely sensitive to key mosquito attractants indole and (R)-(−)-1-octen-3-ol, expressed in oocytes of Xenopus (Anura: Pipidae). Our study demonstrates that insect repellents can both inhibit odorant-evoked currents mediated by ORs and independently elicit currents in the absence of odorants. All of the repellents had effects on one or both ORs; most of these compounds were selective inhibitors and showed a high degree of specificity in their capacity to activate the two ORs.

Answer 244

Based on their dominant effects on both receptor com- plexes, seven compounds were classified into two functional subgroups (Fig. 3A, B). DEET and IR 3535 primarily inhib- ited AaOR2 + AaOR7 responses to indole, whereas PMD, the pyrethroid, 2-U, nepetalactone and callicarpenal pri- marily inhibited AaOR8 + AaOR7 responses to (R)-(−)-1- octen-3-ol (one-way anova, Bonferroni post-tests, P < 0.01 and P < 0.001, respectively)

Answer 245

By lack of knowledge of the mechanisms of action of repellents.

Answer 246

Pyrethroids exhibit both killing and repellent effects (Debboun et al., 2007); the repellent effect is independent of the knock-down mechanism mediated by locking sodium chan- nels in an open state in both insects and vertebrates (Vijverberg & van den Bercken, 1990; Narahashi et al., 1992, 1998; Corbel et al., 2004). (Bohbot_Dickens, 2011)

Answer 247

We had previously proposed insect repellents as modula- tors of ORs (Bohbot & Dickens, 2010). The observation that DEET and SS220, two amides with similar chemical struc- tures, activate and inhibit the same receptor, albeit with dif- ferent magnitudes, serves as further evidence to support this view. Interestingly, callicarpenal and 2-U, which have very different chemical structures, have similar effects on both receptors (Fig. 4

Answer 248

Mosquito olfactory neurons express multiple chemoreceptors A given neuron can express multiple members of several chemoreceptor gene families Single-nucleus RNA-sequencing points to an unexpectedly large diversity of neurons Chemoreceptor co-expression is functionally relevant to odorant responses

Answer 249

Unexpectedly, neurons that expressed Ir25a projected to almost all glomeruli in the antennal lobe (89.9 ± 1.4%, mean ± SEM, n = 3) and expression overlapped extensively with glomeruli labeled by Orco (Herre)

Answer 250

o determine if Orco and Ir25a are co-expressed, we used the Split-QF2 system (Riabinina et al., 2019), which “splits” the transcription factor QF2 into two components, the DNA binding domain (QF2-DBD) and the activation domain (QF2-AD) each tagged with a synthetic leucine zipper (Figures 2A and 2B). When both the QF2-DBD and QF2-AD are co-expressed in the same cell, the two domains associate via the leucine zipper, reconstitute a functional QF2 protein, initiate transcription at the QUAS enhancer, and drive expression of a reporter gene (Figure 2C).

Answer 251

In addition to neurons that contain both Orco and Ir25a protein, we saw neurons that express either Orco or Ir25a alone (Figures 3A–3D), indicating a mixed population of OR cells, IR cells, and OR + IR cells. Staining was absent in the respective Orco and Ir25a mutants, confirming the specificity of the antibodies (Figures 3E–3H). To confirm and extend these results, we performed RNA in situ hybridization on wild-type antennae with Orco, Ir76b, and Ir25a probes (Figures 3I–3K) and discovered that almost half of Orco cells co-express Ir25a, and vice versa. In contrast, few Orco cells co-express Ir76b. We confirmed extensive co-expression of Orco and Ir25a (Figures 3L–3N) and found that substantially fewer cells co-express either Orco and Ir8a or Orco and Ir76b, even after accounting for fewer total Ir76b and Ir8a cells

Answer 252

Each female Ae. aegypti maxillary palp contains approximately 35 capitate-peg sensilla that each house three chemosensory neurons (McIver, 1982) termed “A,” “B,” and “C” cells based on their size, from largest to smallest respectively (Figures 5A–5C and S3V).

Answer 253

Max palp afferents expressing Gr3- and Ir25a.

Answer 254

Glomerulus 2 and Glomerulus 3 received input from Orco-, Ir25a-, and Ir76b-expressing neurons.

Answer 255

We show definitively that Or8 and Or49 are expressed in segregated populations of Orco-expressing neurons (Figure 5M) and, when combined with the results of the previous experiment (Figure 5L), that these cells are all Ir25a-positive. Or8 was shown to be modulated by DEET in Bohobot and inhibited by Picaridin.

Answer 256

Yes, DEET and bitter tastants induce avoidance of an otherwise attractive sucrose solution in Apis mellifera.

Answer 257

Dennis: Remarkably, applying either bitter tastant to skin had no effect on mosquito biting and blood-feeding behavior (Figure 1F; Video S1), even though they were delivered at 10-fold higher concentrations than those that deterred sugar feeding.

Answer 258

Mosquitoes contact the skin surface with the proboscis and the terminal segments of the leg, called the tarsi (Figure 1G). To bite a human arm, a mosquito must first saw through the skin and insert a needle-like appendage, the stylet, under the skin (Figure 1H). Therefore, only the stylet is in direct contact with the blood, while the labellar lobes of the proboscis and the tarsi remain on the surface of the skin.

Answer 259

To test if the proboscis is sufficient to mediate contact DEET repellency, we modified the arm-in- cage assay to restrict the area of skin available for the mosqui- toes to contact (Figures 2A and 2B). The 1.5 mm diameter circle of exposed skin we used in this assay is smaller than the distance between a mosquito’s forelegs, and it therefore cannot touch the skin with both proboscis and legs at the same time (Figure 2B). In this assay, mosquitoes blood fed equally on solvent- and DEET-treated arms, demonstrating that the proboscis alone is not sufficient for DEET repellency (Figure 2C). In contrast, when we enlarged the diameter of exposed skin so that both the legs and the proboscis could con- tact the skin (Figure 2D), DEET remained an effective contact repellent (Figure 2E)

Answer 260

Dennis: While observing the animals interact with these small areas of avail- able skin surface, we noticed that they did not always contact the skin with all six legs (Figures 2D and 2G). We therefore asked if any pair of tarsi was dispensable or required for contact DEET repellency. Leaving any pair of tarsi unoccluded was sufficient to decrease biting events (Figure 2K), suggesting that any pair of tarsi is sufficient to deter blood feeding on DEET-treated arms. Scoring of individual landing events indicated that, in the rare cases where an animal bit a DEET-treated arm, they often contacted the skin with only occluded legs and the pro- boscis (Figures S1A–S1D), and biting events were usually brief (Figures S1E–S1H). We speculate that the chemosensory neu- rons and receptors that sense DEET are present in tarsi on all six legs

Answer 261

-DEET inhibits ingestion and act as a potent contact chemorepellent in the mosquito. -Contact chemorepellncy is mediated by the tarsal segments of the leg and not by the proboscis. -Substances that taste bitter to flies and mosquitoes when ingested are ineffective in repelling mosquitoes on contact.

Answer 262

Although there is strong genetic and anatomical conservation in chemosensory systems across insects, mosquitoes have likely evolved specialized sensing mechanisms relevant to their lifestyle as blood-feeding insects. Drosophila walk on their food while they ingest it so that the same tastants are stimulating tarsal neurons and ingestive neu- rons in the proboscis. In contrast, female mosquitoes walk on the surface of the skin but must puncture the skin to drink blood so that different tastants are stimulating tarsal and inges- tive neurons.

Answer 263

We show that the olfactory receptor MhOR5 from the jumping bristletail4 Machilis hrabei assembles as a homotetrameric odorant-gated ion channel with broad chemical tuning. Using cryo-electron microscopy, we elucidated the structure of MhOR5 in multiple gating states, alone and in complex with two of its agonists—the odorant eugenol and the insect repellent DEET. Together, our data support a model in which diverse odorants share the same structural determinants for binding, shedding light on the molecular recognition mechanisms that ultimately endow the olfactory system with its immense discriminatory capacity. Here we show that MhOR5 detects a wide array of odorants through a single promiscuous binding site, offering structural insight into how such flexible chemical recog- nition is achieved. Notably, odorant binding relies predominantly on hydrophobic interactions, which lack the strict geometric constraints inherent to other intermolecular associations (such as hydrogen bonds) that frequently mediate ligand recognition. Olfactory receptor tuning thus depends on the stereochemistry of its ligands25,26 , but does not adhere to the classic lock-and-key mechanism that governs many receptor–ligand interactions.

Answer 264

A comparison of the structure of MhOR5 with the previously elucidated structure of Orco from the wasp Apoc- rypta bakeri10 showed that these two receptors, despite sharing only about 18% amino acid conservation, display notable similarity, both in the fold of each heptahelical subunit and in the tetrameric organization of the subunits within the membrane plane (Extended Data Fig. 5a, b). As in Orco, each MhOR5 subunit contributes a single helix (S7b) to the central ion conduction pathway, and their S0–S6 helices form a loosely packed domain that projects radially away from the pore axis (Fig. 1d). Within the membrane, the contacts between MhOR5 subunits are mini- mal and confined to the pore, whereas about 75% of the residues that form inter-subunit interactions reside within the intracellular ‘anchor’ domain, formed from the intertwined S4–S7 helices of all four subunits (Extended Data Fig. 5d). Analogous to the Orco structure, the tightly packed anchor domain of MhOR5 exhibited the highest local resolution (Extended Data Fig. 4c), consistent with a structural role in stabilizing the loosely assembled S0–S6 transmembrane domains within the lipid bilayer. The limited sequence conservation across neopteran ORs and Orcos maps to residues predominantly within the pore and anchor domain10 , further underscoring how the architecture of this receptor family can accommodate a high degree of sequence diversification while maintaining the same overall fold, a feature that is likely to have facilitated the rapid evolution of ORs

Answer 265

The dilation of the S7b helices thus appears to be sufficient to gate the ion conduction pathway—this small conformational change would present a low energetic barrier to gating, consistent with the low affinity of most odorants 11,17 and with functional evidence that MhOR5 channels, as with many insect olfactory receptors, open spontaneously even in the absence of ligand (del Marmol)

Answer 266

del_Marmol: Density corresponding to DEET localized to the same binding pocket as eugenol, encased within the same box-like configuration of aromatic and aliphatic side chains (Fig. 4a, b, Extended Data Figs. 6b, 9d). As with eugenol, computational docking of DEET yielded multiple poses with comparable docking scores that fit the experimental density well.

Answer 267

inding of DEET to the same site offers structural corroboration that this insect repellent might exploit the promiscuity of diverse ORs and serve as a molecular ‘confusant’ by scrambling the olfactory code31 . Other modulators of olfactory receptors, such as VUAA1 (which inhibits MhOR5), cannot favourably dock within this binding pocket owing to their much larger size, suggesting that insect olfactory receptors might possess additional points of allosteric modulation that expand their signalling mechanisms.

Answer 268

The promiscuous and arbitrary nature of odorant recognition is likely to impose substantial selective pressures on the structure and function of olfactory circuits, driving the evolution of synaptic and circuit mechanisms that can decorrelate, decode, and impose meaning onto combinatorial patterns of receptor activity32 . Odour discrimina- tion is thus transformed from a biochemical problem at the receptor level to a neural coding problem within the brain

Answer 269

Finally, our work sheds light on the evolution of the insect olfac- tory system. We demonstrate that MhORs can function as homomeric odorant-gated channels, supporting the proposal that they lie at the ancestral origin of the insect olfactory receptor family 4,14 , which expanded massively across insect lineages to emerge as possibly the largest and most divergent class of ion channels in nature2 . Why neop- teran ORs became obligate heteromers with Orco remains unclear, but presumably reflects the fact that Orco confers structural stability on the complex, thereby relaxing evolutionary constraints on the ORs and allow- ing them to further diversify, to ultimately support the flexible detection and discrimination of an enormous and ever-changing chemical world.

Answer 270

Some people are consistently more attractive to mosquitoes than others, due to skin odor differences IR mutants (Ir25a and Ir76b) show reduced overall attraction to humans Mosquitoes with broad olfactory deficits can distinguish highly and weakly attractive people Highly attractive people have higher levels of carboxylic acids on their skin

Answer 271

A single female mosquito will bite multiple humans during her 3- to 6-week lifetime to obtain sufficient protein to produce a new batch of eggs as often as every 4 days (Ponlawat and Harrington, 2005). This repetitive human-directed feeding behavior allows the mosquito to contract and transmit pathogens in successive bites. Aedes aegypti are efficient vectors of disease because they specialize on human hosts

Answer 272

Although carboxylic acids are neutral or repellent when presented individually or in combination with each other, they strongly increase mosquito attraction when combined with ammonia and lactic acid (Smallegange et al., 2005, 2009). Mosquito attraction behavior is elicited much more reliably using live human hosts or natural odor blends collected directly from humans, than it is by mixing pre-specified compounds, despite improvements in synthetic odor blends as lures for attract-and-kill traps for use in the field (Bernier et al., 2007; Njiru et al., 2006; Verhulst et al., 2011a).

Answer 273

Although there is some overlap in ligand tuning, ORs generally respond to esters, alcohols, ketones, and aldehydes, and IRs respond to carboxylic acids and amines.

Answer 274

These data indicate that mosquitoes have evolved highly redundant sensory systems permitting them to retain attraction to humans even with significant genetic disruption of their olfactory system (Herre et al., 2022). Nevertheless, mutating the IR pathway produced stronger effects on overall mosquito attraction to humans than the OR pathway.

Answer 275

Highly attractive subjects produced significantly higher levels of three carboxylic acids—pentadecanoic, heptadecanoic, and nonadecanoic acids—as well as 10 unidentified compounds in this same chemical class. The specific blend of these and other carboxylic acids varied between different high attractive subjects. Therefore, there may be more than one way for a person to be highly attractive to mosquitoes.

Answer 276

Notably, the carboxylic acids we identified are not especially volatile. Hence, it is unclear whether they are important for differential mosquito attraction to humans across long distances. It is possible that the compounds we identified may give rise to more volatile components that are also enriched on the skin of “mosquito-magnet” subjects but which were not found in our study due to the analytical methods used. (De Obaldia)

Answer 277

Not all behavior requires locomotion (grooming), there is no change in parameters if you use just the centroid. So you miss information.

Answer 278

A simple and lightweight encoder-decoder CNN. You start with the image of an animal fed into a series of convolution to extract features. Outsample it until you get a set a multi channel image with each channel being the confidence map for each individual body part.

Answer 279

1) Fast training on single GPU 2) The fast training enables the human-in-the-loop training.

Answer 280

When yu have two different hypotheses of how distinct body part should be grouped in a single frame among twoinstances (to which animal do they belong). It is solved using part affinity fields, representing the connectivity between body parts as a set of vectors.

Answer 281

- A general structural framework with high probability for repellent activity was developed through molecular modelling techniques. - Electrophysiological studies on the insects' olfactory receptor organs reveal that certain cell types, which are not involved in perception of the attractive odorants, respond to deet and/or KBR 3023. As soon as one of the compounds is presented together with an attractant, a new input is active in the brain, which adds to the input from other receptors activated by the attractant. This new overall pattern clearly differs from that elicited by the attractant, so that the insect is no longer able to detect the latter. -The specificity and mode of action of KBR 3023 was investigated by experi- ments exploring second-messenger responses elicited in antenna1 preparations of male P . americana. KBR 3023 induced a rapid increase in the concentration of inositol triphosphate in a dose-dependent and tissue-specific manner; other second-messenger systems were not affected. These observations suggest that KBR 3023 may act via subsets of G-protein-coupled receptors in sensory neu- rones

Answer 282

All the structures have a pattern consisting of an amide group, a sp3 hybridised oxygen atom within a hydroxyl or ester group and a lipophilic core linking the two functional groups. The essential feature in the amide group was the carbonyl oxygen atom. All compounds in the set have a more-or-less flexible linkage between the two functional groups. For each molecule this flexibility may lead to a large set of ener- getically possible relative arrangements of the carbonyl oxygen atom (mostly in the amide group) and the sp3 hybridised oxygen atom. The model shows some character- istic features: 0 the essential binding points, i.e. the two oxygen atoms represented by their lone pair centroids (colour codes in yellow) in a well-defined distance and orientation (the equivalent functional groups are colour-coded in green and red, respectively); 0 a lipophilic moiety linking the two attachment points which may be of considerable volume, although we identified some forbidden spatial regions ; 0 a lipophilic moiety beyond the carbonyl group, which turned out to be of high relevance for tuning the size of the repellent effect

Answer 283

For delivery, most studies use a solvent to elute odour extracts from sorbent collection tubes and then allow the solution to evaporate from a vial, septum or filter paper. However, the diverse odorants in a blend often require different solvents and will evaporate from solution at different rates based on volatility33, changing the character of a blend over time. We therefore developed an odour-delivery system involving thermal desorption34 that enabled us to deliver natural extracts directly from sorbent tubes to mosquitoes with precise quantitative control (Fig. 2f and Extended Data Fig. 3). Importantly, we were able to match the total odour concentration of diverse samples delivered to the same mosquito (Fig. 2g) and to deliver replicate puffs of the same sample to different mosquitoes, while maintaining the original blend ratios (Fig. 2h).

Answer 284

Three glomeruli dominated responses at low and middle doses (Fig. 3a–d). One was strongly activated by the odour of all three species (cyan arrowheads), whereas another responded strongly to human odour but was insensitive or only weakly sensitive to animals (green arrowheads). A third glomerulus was strongly activated by both animals, but not by humans (orange arrowheads). We tentatively refer to these as the broadly tuned (B), human-sensitive (H) and animal-sensitive (A) glomeruli, respectively. Although additional glomeruli were activated by the highest dose of each host blend (Fig. 3b–d), and there may be weak responses below the sensitivity threshold of our preparation, we were struck by the simplicity of this pattern. The relative activity of three glomeruli cleanly separated human and animal odours across the concentration gradient (Fig. 3e, f). The B glomerulus was again strongly activated by all of the odour extracts, including the two nectar odours, whereas the H and A glomeruli were most strongly activated by human and animal odours, respectively.

Answer 285

Despite the overlap in blend components, human and animal samples differed consistently in blend ratios, leading to a clear separation in a principal component analysis (PCA) (Fig. 4b and Extended Data Fig. 5e). Loadings on the human–animal axis of the PCA showed that human odour was enriched in three ketones: sulcatone, geranylacetone and acetoin. Human odour also stood out for its high relative abundance of the long-chain aldehyde decanal (ten carbons) and low relative abundance of the short-chain aldehydes hexanal and heptanal (six and seven carbons)

Answer 286

Decanal, undecanal and the combo stimulus (which included decanal and undecanal) all evoked strong and prolonged activity in the H glomerulus (Fig. 5c–e and Extended Data Fig. 7a). The B glomerulus was strongly activated by acetoin and modestly activated by the combo blend of non-acetoin compounds (Fig. 5c, e), probably the sum of a number of weak individual responses (Extended Data Fig. 7a). No human odour components evoked activity in the A glomerulus at physiological concentrations. Previous research implicated a sulcatone-sensitive receptor in Ae. aegypti preference for humans3. Although we did not see consistent activity in response to this compound at its concentration in 1× human odour (Fig. 5c), several glomeruli responded at higher doses (data not shown), suggesting that it may be more relevant to behaviour at close range. Taken together, the antennal lobe response to 1× human odour is largely explained by individual responses to a subset of perceptually dominant components, including long-chain aldehydes and acetoin (Fig. 5e).

Answer 287

Remote focusing allows rapid switching of the imaging plane by moving a small, lightweight mirror located upstream in the imaging path. This alternative focusing method does not involve mechanical movements near the specimen, thereby avoiding specimen agitation and permitting axial scan speeds faster than those associated with traditional piezo-objective units.

Answer 288

- Aedes spp. are effective pollinators of Platanthera obtusata orchid. -P obtusata orchid emits an attractive, nonanal-rich, whereas Platanther species not visited by mosquitoes, emit scents dominated by lilac aldehyde. - Calcium imaging exper- iments in the mosquito AL revealed that nonanal and lilac aldehyde each respectively activate the LC2 and AM2 glomerulus, and re- markably, the AM2 glomerulus is also sensitive to N,N-diethyl- meta-toluamide (DEET), a mosquito repellent - Lateral inhibition between these 2 glomeruli reflects the level of attraction to the orchid scents. Whereas the enriched nonanal scent of P. obtusata activates the LC2 and suppresses AM2, the high level of lilac aldehyde in the other orchid scents inverts this pattern of glo- merular activity, and behavioral attraction is lost.

Answer 289

Yes, and the LC2 glomerulus in Lahonder also responded to nonanal.

Answer 290

Interestingly, for Ae. aegypti, the AM2 glomerulus showed the strongest response to lilac aldehyde, followed by DEET, a strong mosquito repellent (23–26) (SI Appendix, Fig. S7), although these responses were suppressed when stimulated with the orchid mixture

Answer 291

To better understand how the ratio of lilac aldehyde and nonanal altered the activation of the LC2 and AM2 glomeruli, we tested mixtures of lilac aldehyde and nonanal at different concentration ratios and found that lilac aldehyde suppressed the response of LC2 to nonanal, suggesting lateral inhibition between these 2 glomeruli. Higher lilac aldehyde concentrations increased LC2 suppression, but reciprocally increased AM2 activation (Fig. 4 E and F). By contrast, nonanal caused suppression of AM2 re- sponses to lilac aldehyde, with higher nonanal concentrations causing increased AM2 suppression, while increasing the activa- tion of LC2 (Fig. 4 E and F).

Answer 292

Next, we pharmacologically manipulated the inhibition by focally applying GABA-receptor antagonists (1 μM CGP54626; 10 μM picrotoxin) onto the AL during our experiments. During application of the vehicle (saline) control, LC2 and AM2 responses to the P. obtusata scent were similar to those described above (Fig. 4 E, F, and H and SI Ap- pendix, Fig. S9), whereas during antagonist application, the effect of nonanal was blocked and the small amount of lilac aldehyde in the scent was sufficient to evoke a strong response in AM2 (Fig. 4H).

Answer 293

The qualitative similarities in the scent profiles of attractive nectar sources, and the attractiveness of the P. obtusata scent across mosquito species, raises the question of whether flower scents may be activating conserved olfactory channels, such as homol- ogous odorant receptors (34). Our results will hopefully motivate research to identify the odorant receptors that are responsive to floral compounds, and their projections to the AL, such as the LC2 and AM2 glomeruli (34).

Answer 294

They form the outer cortex with neurons projectingprocesses centrally to form a dense fibrous central neuropil.

Answer 295

The neuropil is stereotyped and highly ordered with functional segregation evident even at the level of the gross anatomy. The VNC is clearly subdivided in the dorso-ventral plane: ventral regions of the thoracic neuropils are innervated by neurons associated with the legs (Merritt and Murphey, 1992), whereas the dorsal neuropils are innervated by neurons associated with the wings and flight (Leise, 1991; Milde et al., 1989; Strausfeld, 1992) with intermediate regions serving to link legs and wing control (Namiki et al., 2018) (Figure 1).

Answer 296

The tectulum (Tct) was described by Power (1948) as a discrete dorsal region of the VNC, overlying the mesothoracic neuromere like a saddle and extending from the posterior prothoracic to the anterior metathoracic neuromeres.

Answer 297

The lower and intermediate tectulum show no overt signs of segmental barriers and are considered to lack a segmental organization. The upper tectulum, however, does have some segmental specializations and can be segregated on the basis of the synapse rich neuropils revealed by N-Cadherin/bruchpilot expression into three neuromere specific neuropils: neck, wing, and haltere tectulum for the ProNm, MesoNm, and MetaNm neuromeres, respectively

Answer 298

Unlike the tectulum, the leg neuropils exhibit clear segmental boundaries and, although each thoracic neuromere is slightly different, they all conform to the same organizational principles (Figure 2A; Video S2). The legNps contain the sensory afferent endings of leg sensory neurons, the leg motor neurons, and local interneurons that control leg movement. The leg neuropils are best described in transverse section and can be partitioned into distinct regions along the dorsoventral axis (Figure 2A; Video S2). The ventralmost layer of leg neuropil, the ventral association center (VAC) (Merritt and Murphey, 1992) is readily distinguishable as synapse rich neuropils (VAC, Figures 1E-1G and and2A;2A; Video S2). The VAC is innervated by sensory afferents from sensory neurons associated with tactile bristles on the leg (Murphey et al., 1989b). Adjacent to the VAC is a paired globular structure, the medial ventral association center (mVAC) (mVAC, Figures 1E-1G and and2A;2A; Video S1). The mVAC is a bilaterally symmetrical neuropil region that can be identified both by its fine textured appearance and as dense synaptic neuropil (Merritt and Murphey, 1992). In Drosophila, the mVAC is innervated by a subset of femoral chordotonal organ (FeCO) sensory neurons which form a “club”-shaped projection that terminates in the mVAC (Phillis et al., 1996).

Answer 299

- Here, we examined Drosophila olfactory sensory neurons and found that inhibitory odors triggered outward receptor currents by reducing the constitutive activities of odorant receptors, inhibiting the basal spike firing in olfactory sensory neurons. - Remarkably, this odor-evoked inhibition of olfactory sensory neurons elicited by itself a full range of olfactory behaviors from attraction to avoidance, as did odor-evoked olfactory sensory neuron excitation. - These results indicated that peripheral inhibition is comparable to excitation in encoding sensory signals rather than merely regulating excitation. - Furthermore, we demonstrated that a bidirectional code with both odor-evoked inhibition and excitation in single olfactory sensory neurons increases the odor-coding capacity, providing a means of efficient sensory encoding. First, in flies with only one type of functional OR, odor-evoked inhibition can drive olfactory behaviors, just as odor-evoked activation does. Second, a single type of OSN can drive two opposing behaviors and discriminate odor mixtures if inhibition and activation coexist. Third, genetic disruption of odor-evoked inhibition induces a switch of olfactory behaviors. Fourth, odor-evoked inhibition of OSNs increases odor-coding capacity by reducing response saturation and decorrelating odor representation.

Answer 300

Cao_Luo (2017): The Or85a-expressing OSNs exhibited spontaneous firing in the absence of stimuli, and this effect was reversibly abolished by acetophenone (Fig. 1a, top). Correspondingly, an outward receptor current was induced by acetophenone under a voltage-clamped configuration

Answer 301

odor-evoked OSN inhibition is produced by the closure of ion channels that are opened by constitutively/thermally activated ORs, thus yielding an outward receptor current. Our findings support the hypothesis that OR molecules fluctuate between active and inactive states in a temperature-dependent manner, with inhibitory odors stabilizing their inactive states. (Luo_Cao)

Answer 302

The coexistence of odor-evoked inhibitory and excitatory responses in the same OSN raises a possibility that the two responses may interact with each other. Next, we examined whether acetophenone could inhibit the ethyl 3-hydroxybutyrate-induced excitatory responses in Or85a-OSNs. In the presence of a background ethyl 3-hydroxybutyrate, a larger acetophenone-induced outward receptor current was obtained (Fig. 3a), suggesting that acetophenone could inhibit the basal inward current and odor-evoked excitatory responses. Acetophenone inhibited the inward receptor currents triggered by ethyl 3-hydroxybutyrate in a dose-dependent manner (Fig. 3b), but it did not inhibit the inward currents mediated, for example, by the exogenously expressed ATP-gated P2X2 cation channels (Fig. 3c and Supplementary Fig. 2a, see also “Methods” section) or by the light-gated channelrhodopsin ChR2 (Fig. 3d and Supplementary Fig. 2b, c, see also “Methods” section). Therefore, in Or85a-OSNs, acetophenone specifically inhibited the activity of Or85a receptors. To further explore the property of acetophenone-induced inhibition, we examined the dose–response relationship of the excitatory responses to ethyl 3-hydroxybutyrate in the presence of a background acetophenone. We found that acetophenone shifted the dose–response relationship of excitatory responses by significantly increasing the half-saturating odor concentration (Fig. 3e), while maintaining the amplitude of the maximal excitatory responses and the kinetics and shape of the responses (Fig. 3e and Supplementary Table 1). These results indicate a competitive inhibition of ethyl 3-hydroxybutyrate-induced excitatory responses by acetophenone.(Luo_Cao)

Answer 303

Unexpectedly, linalool, an odor that inhibits the basal firing and calcium signals of Or56a-OSNs and that does not elicit chemotaxis in Orco −/− flies, attracted flies with Orco restored to Or56a-OSNs (Fig. 4c). Similar inhibition-elicited attraction behaviors were observed in flies with Orco restored to either Or82a-OSNs or Or92a-OSNs (Fig. 4c). In contrast, geraniol, an odor that inhibits Or10a-OSNs, repelled flies with Orco restored to Or10a-OSNs (Fig. 4d). Similar avoidance behaviors elicited by inhibition were also observed in flies with Orco restored to Or42b-OSNs or Or85a-OSNs (Fig. 4d). On the other hand, odor-evoked activation alone also elicited attraction (Fig. 4e) and avoidance (Fig. 4f) behaviors depending on the type of OSNs activated. These gain-of-function results demonstrated that similar to odor-evoked activation of OSNs, odor-evoked inhibition of basal activities in the OSNs also encodes odor information for perception and behaviors.

Answer 304

Luo_Cao: odor-evoked bidirectional responses in the same OSN enable olfactory computations at the level of single OSNs, which can be used to effectively discriminate odor mixtures.

Answer 305

Luo_Cao: In adult Drosophila, odor recognition is based on the activity patterns of ~50 ORs. Our gain-of-function studies have revealed that odor-evoked OSN inhibition encodes odor information in flies that have only one type of functional OR. A question is whether such inhibition could contribute to odor coding when many ORs are functional. To address this question, we expressed tetanus toxin (TNT) in Or85a-OSNs to block their synaptic transmission to the antennal lobe (see “Methods” section). We examined the chemotactic behaviors of these flies to acetophenone that inhibits the basal firing of Or85a-OSNs, and found that Or85a-TNT flies were attracted to acetophenone, which normally did not elicit chemotaxis in wild-type (WT) flies (Fig. 6a). In contrast, flies expressing an inactive TNT exhibited no chemotaxis to acetophenone (Fig. 6a). Knockout of Or85a receptor elicited attraction behaviors to acetophenone (Fig. 6a, see also “Methods” section). These loss-of-function results indicate that olfactory system integrates an avoidance signal from Or85a and an attraction signal collectively from other chemoreceptors, thereby leading to a non-chemotactic behavior to acetophenone in WT flies.

Answer 306

the inclusion of odor-evoked inhibition in OSNs increases the information entropy of most OSNs and the total entropy of the whole system for all odor number tested (Fig. 7b, inset). Mechanistically, the inclusion of OSN inhibition increases the coding capacity of OSNs by preventing response saturation (Supplementary Fig. 7) and making the responses more uniformly distributed within the response dynamic range (Supplementary Fig. 8). the inclusion of OSN inhibition decorrelates odor-evoked responses across OSNs, thus increasing the independent dimensions of odor coding. Therefore, an OSN with both odor-evoked inhibitory and excitatory responses can compute and amplify the difference between similar odor mixtures (Luo_Cao)

Answer 307

Two alternative mechanisms may drive such an odor- and OR-specific inhibition17. Odors might bind to OR proteins, leading to the opening of an inhibitory conductance such as potassium channels11, 26 to counteract the basal activity. Alternatively, odors might bind to ORs and stabilize them in inactive state21, thus directly reducing the basal activity of ORs. In the absence of odor stimulation, we observed a basal inward current in the voltage-clamped OSNs, which increased at higher temperatures but was abolished in the absence of OR/ORCO complex. These results suggest that ORs can be constitutively/thermally activated, producing a basal inward current. This basal current is directly inhibited by inhibitory odors, demonstrated by our finding that inhibitory odors reduce the basal membrane conductance in the voltage-clamped OSNs. In addition, we found that inhibitory odors also inhibit the responses to excitatory odors. Therefore, inhibitory odors can inhibit both spontaneous OR activity and excitatory odor-induced OR activity.4

Answer 308

Where this synergism arises in the brain 54 remains unclear. CO2 is known to be detected only on the maxillary palps, while L-lactic 55 acid responses have been observed in Ir8a-expressing neurons on the antennae in 56 mosquitoes (Davis & Sokolove, 1976; Grant et al., 1995; Kellogg, 1970; Raji et al., 2019; 57 Shankar et al., 2021), suggesting that the synergism may be downstream from the 58 sensory neurons.

Answer 309

Fluctuating plumes, rather than homogenous plumes are more attractive to mosquitoes. CO2 plume structure is known to affect behavior in other insects also. This makes evolutionary sense as insects encounter non-homogenous plumes of odo in the natural environment. These 67 behavioral observations are difficult to explain with labeled-line models of olfactory 68 preferences (Haverkamp et al., 2018), as the same labeled-lines should be activated by 69 the homogenous and the non-homogenous plume patterns. (Goyal_Gupta, 2023, BioRxviv)

Answer 310

Many types of PNs, such as those innervating I-AM1, I-AC1, I100 PD1, I-AD2, and I-AD4 glomeruli, did not respond to CO2. I-CD2 and I-PD4 PNs typically 101 showed inhibitory responses to CO2 (Figure 1a, Supplementary Figure S1). In 6 102 glomeruli, for each of which we had at least 8 PNs in our dataset, we checked whether 103 the response magnitudes over all PNs in the glomeruli were statistically different from 0: 104 we found the firing responses of PNs were significantly inhibitory in I-PD6 significantly excitatory in I-MD3 (8.26 ± 106 13.53; P=0.004, n= 16 PNs), and not significantly different from 0 in I-PD2, I-AL2, I-AM2 107 and I-AL3 glomeruli. However, careful examination of the CO2 responses of different PNs 108 within the same glomerulus revealed heterogeneity. For example, among the recordings 109 from two I-PD6 PNs shown in Figure 1b, the first PN showed an inhibitory response to 110 CO2 and while the second PN showed no response. Similarly, among I-V3 and I-AD5 PNs, 111 some PNs showed excitatory responses while some did not respond to CO2 (Figure 1c, 112 1d). Even among I-MD3 PNs, which were more frequently activated by CO2 among the 113 PNs examined in our dataset, there was considerable heterogeneity in the responses 114 (Figure 1e): the first two PNs included in the figure showed clear excitatory responses to CO2. Given that I-MD3 118 PNs primarily receive their input from the 1-octen-3-ol-sensitive sensory neurons in the 119 capitate peg sensillum (Singh et al., 2022), it is likely that the excitatory responses to CO2 120 observed in some of the I-MD3 PNs are mediated by lateral excitatory inputs within the 121 AL.

Answer 311

Our patch-recordings in 128 the AL also included LNs, whose identity was confirmed by dye fills. Overall, our dataset 129 included 49 LNs that were tested with CO2. Consistent with our expectation, we found 130 that some LNs showed excitatory responses, some showed inhibitory responses, and 131 some did not respond to CO2 (Figure 2a, b). The frequency of excitatory responses in LNs 132 was slightly above 20% (10 out of 49 PNs), which was more than that seen in PNs (14 out 133 of 163 PNs, i.e., less than 10%). A similar proportion of LNs (9 out of 49) was also 134 inhibited by CO2. Overall, these results indicate that CO2 activates or inhibits a sizeable 135 fraction of LNs, which could then spread the activity to diverse PNs in the AL. (Goyal_Gupta, 2023)

Answer 312

even at the antennal lobe level, the magnitudes of the neural responses do not 191 appear to change with the temporal patterns of CO2 stimulation. However, the 192 information about the temporal pattern of the stimulus appeared to be retained in the 193 temporally patterned spikes of PNs, which could carry this information to downstream 194 neurons. We quantified this information by asking if the stimulus pattern of a recording 195 could be predicted by looking at the spiking responses in each PN (see Methods). 196 Compared to the chance level of 0.33 in predicting one of the three stimulus patterns, 197 we could predict the stimulus patterns of recordings with a significantly higher accuracy 198 of 0.64 ± 0.27 (P = 0.02, n = 9 PNs, signed-rank test; Figure 4g). Thus, PN response 199 patterns indeed contain information about the temporal patterns of stimuli, which can 200 potentially be used by the downstream neurons in the higher olfactory centers to 201 generate stronger behavioral preference to non-homogenous patterns of CO2.

Answer 313

Recent studies have 249 shown that Ir8a-expressing sensory neurons innervate a subset of glomeruli in the AL 250 (Herre et al., 2022; Shankar et al., 2021; Shankar & McMeniman, 2020), which map onto 251 11 glomeruli (I-LC1, I-LC2, I-PL1, I-PL2, I-PL3, I-PL4, I-PL5, I-PD2, I-MC3, I-CD2, I-CD4) in 252 the brain atlas we used (Ignell et al., 2005)

Answer 314

- the tarsi and wings can sense chemicals in a gaseous form. -Odors produce differing responses on different appendages. -Most consistent and strongest response occurred when exposed to triethylamine. -Antennae and mouthparts showed nearly identical responses pattern to all tested compounds. -Hindleg tarsi only responded to TEA, indicating that the hind legs are not as chemoreceptive.

Answer 315

No, it is expressed in both the antenna and the maxillary palp. (Bohbot 2007, Bohbot 2014).

Answer 316

Yes, in Yang and Bloomquist the response pattern to chemical was similar in foreleg and midleg.

Answer 317

Triethylamine.

Answer 318

- DEET based products provided complete protection for the longest duration. - Complete protection times correlated positively with DEET concentration.

Answer 319

Fradin_Day (2002): A formulation containing 23.8 percent DEET had a mean complete-protection time of 301.5 minutes. A soybeanoil–based repellent protected against mosquito bites for an average of 94.6 minutes. The IR3535-based repellent protected for an average of 22.9 minutes. All other botanical repellents we tested provided protection for a mean duration of less than 20 minutes. No non-DEET repellent fully evaluated in this study was able to provide protection that lasted more than 1.5 hours.

Answer 320

Fradin_Day (2002): The controlled-release formulation we tested did not prolong the duration of action of DEET. The alcohol-based product containing 23.8 percent DEET protected significantly longer than the controlled-release formulation containing 20 percent DEET

Answer 321

Fradin_Day (2002): The protection provided by DEET is proportional to the logarithm of the dose; higher concentrations of DEET provide longer-lasting protection, but the duration of action tends to plateau at a concentration of about 50 percent.

Answer 322

Most commercially available formulations now contain 40 percent DEET or less, and the higher concentrations are most appropriate to use under circumstances in which the biting pressures are intense, the risk of arthropodtransmitted disease is great, or environmental condition tions promote the rapid loss of repellent from the surface of the skin

Answer 323

Despite the substantial attention paid by the lay press every year to the safety of DEET, this repellent has been subjected to more scientific and toxicologic scrutiny than any other repellent substance. The extensive accumulated toxicologic data on DEET have been reviewed elsewhere.17,35-39 DEET has a remarkable safety profile after 40 years of use and nearly 8 billion human applications.35 Fewer than 50 cases of serious toxic effects have been documented in the medical literature since 1960, and three quarters of them resolved without sequelae.35,37 Many of these cases of toxic effects involved long-term, heavy, frequent, or whole-body application of DEET. No correlation has been found between the concentration of DEET used and the risk of toxic effects.

Answer 324

Neurotransmitter release from ORNs is driven by two distinct sources of excitation: direct activity derived from the odorant receptor and stimulus-selective lateral signals originating from stereotypic subsets of other ORNs. Consequently, the level of presynaptic neurotransmitter release from an ORN can be signiﬁcantly dissociated from its ﬁring rate.

Answer 325

Stimulus-selective lateral signaling results in the distributed representation of CO2—a behaviorally important environmental cue that directly excites a single ORN class—in multiple olfactory glomeruli, each with distinct response dynamics. CO2-sensitive glomeruli coupled to behavioral attraction respond preferentially to fast changes in CO2 concentration, whereas those coupled to behavioral aversion more closely follow absolute levels of CO2. Behavioral responses to CO2 also depend on the temporal structure of the stimulus: ﬂies walk upwind to ﬂuctuating, but not sustained, pulses of CO2.

Answer 326

(Zocchi_Hong):Lateral crosstalk between glomeruli begins in ORNs, where global GABAergic inhi- bition at presynaptic terminals regulates the gain of olfactory input.6,7 In addition, a small population of excitatory local neurons mediates weak coupling between PNs

Answer 327

(Zocchi_Hong): The only intervention that affected lateral signaling was pharmacological inhibition of the Na+/K+-ATPase by ouabain, which selectively abolished the excitatory component of CO2-evoked responses (Figure S4D). The mechanism(s) by which Na+/K+-ATPase inhibition affects lateral signaling requires more investigation but could include changes in local ionic concentrations, changes in excitability, and/or direct effects on receptors mediating intercellular communication

Answer 328

Leal (2014) Review: Despite its low cost, more affordable alternatives are highly desirable, particularly for those in endemic areas where cost is an impediment. Alternative compounds like IR 3535 and picaridin have been developed using molecular modeling, but the lack of knowledge of the molecular target(s) for DEET has retarded progress toward low cost alternatives.

Answer 329

Leal (2014) Review: To put it simply, a repellent is an odorant that must act in the vapor phase, but some ‘repellents’ are either nonvolatile or have extremely low vapor pressure and, therefore, unable to convey a signal away from the source. On the other hand, other repellents have such high vapor pressure (low boiling point) that their repellency might be misleading as they only last for a short period of time. In practical terms, the end user wants to apply a repellent, which lasts for hours, not one that evaporates quickly — a criterion already known in the early days of product development [4].

Answer 330

A high boiling point (and consequently lower vapor pressure) confers lower evaporation rate and, consequently, a long protection time — one of the essential properties of a repellent if it is to remain competitive in the market.

Answer 331

Out of the four top tier insect repellents that remain competitive in the worldwide market, two have been designed more recently by using molecular modeling. In the 1970s, Merck developed the insect repellent 3535 thus named IR 3535 or Merck 3535 (IUPAC name: ethyl 3-[acetyl(butyl)amino]propanoate, a derivative of b-alanine [8]. In the sunset of last century, Bayer developed KBR 3023 (IUPAC name: 1piperidinecarboxylic acid 2-(2-hydroxyethyl)-1-methylpropylester), which is also known as picaridin, icaridin, and Bayrepel

Answer 332

The sex pheromone of the silkworm moth, bombykol, was discovered almost a decade after DEET was already protecting the lives of war ﬁghters and later being used by the public at large. Scientists have already unraveled the intricacies and molecular details of bombykol reception and perception. We now know how bombykol is transported inside insect antennae by a carrier pheromone-binding protein and delivered to a neuron-housed odorant receptor. The molecular details of the silkworm bombykol receptor, including putative binding sites, have been untangled. It has been unraveled how bombykol signals are processed in the brain and integrated with other stimuli to ultimately start odorant-guided navigation (reviewed in [13]). By contrast, DEET is older than any investigator interested in its mode of action yet our understanding of DEET reception is still in its infancy. Our ignorance of the subject is due in part to the lack of appropriate funding, the challenging nature of the subject, the one-size-ﬁts-all attempts to understand vector biology with surrogates, and, perhaps dogmatic positions against new insights that challenge old models.

Answer 333

Insect repellents like DEET, and particularly picaridin, share similar structural motifs with methyl jasmonate. Jasmonic acid elicited very small currents from CquiOR136/CquiOrcoexpressing oocytes, but methyl jasmonate displayed dosedependence responses, slightly stronger than those elicited by DEET.

Answer 334

Pauluch_Coats: Even with a long history of research investigating how chemicals can influence mosquitoes, there are many challenges for the advancement of insect repellent science. With the large accumulation of information, it has become increasingly difficult to interpret the significance of repellents tested under different laboratory conditions, or to explain how compounds with a wide variety of structures can influence insect behavior under field conditions. Much of current knowledge of repellents was acquired in the United States during the 1940s with research on the development of synthetic chemicals to repel arthropods, which resulted in products containing dimethyl phthalate (DMP), indalone (butyl 3,3-dihydro-2,2-dimethyl-4-oxo-2H-pyran6-carboxylate) and ethyl hexanediol, known as Rutgers 612 (2-ethyl-1,3-hexanediol) (Figs 1 and 2). It was also around this time that DEET (N,N-diethyltoluamide) (Fig. 1), the gold standard of repellents, was first tested by the USDA Orlando, FL, laboratory and further developed for use in topical applications in the 1950s

Answer 335

Pauluch_Coats: Since that time there have been significant efforts in academia, government and the private sector to identify new insect repellents. They were largely driven by reports of DEET toxicity,1 – 4 minimal efficacy against some arthropod vectors (e.g. Anopheles spp. of mosquitoes),5 high incidence of arthropod-borne diseases,6,7 decreasing consumer acceptance8 – 10 and the potential for insects to develop resistance to certain chemicals.

Answer 336

In recent years, universities have played an important role in the advancement of insect science by providing verification of new product efficacy for registration, as well as exploring novel repellent chemistries. One example is the development of the BioUD active compound 2-undecanone, which was identified as a mosquito repellent by Farrar and Kennedy24 at North Carolina State University and then licensed to HOMS, LLC, a North Carolina-based biotech company. The active compound was identified from a wild tomato, Lycopersicon hirsutum Dunal f. glabratum CH M ̈ull, and is thought to play a role in natural plant defense mechanisms against insect herbivores.25 Zhu et al. 26 at Louisiana State University have been working with the insecticidal and repellent properties of vetiver grass, Vetiveria zizanioides Lynn Nash, essential oil. One of the primary components, nootkatone (4,4a-dimethyl-6-prop-1- en-2-yl-3,4,5,6,7,8-hexahydronaphthalen-2-one), a sesquiterpene, was also investigated by Dietrich et al.21 at Oregon State University as one of the repellent components of Alaska yellow cedar oil, Chamaecyparis nootkatensis (D. Don) Spach. Pauluch_Coats

Answer 337

Since the time DEET entered the market in the 1950s, it has provided good residual protection against a broad spectrum of insects, including mosquitoes, black flies, chiggers, ticks, bedbugs and fleas.62 The general public registered DEET for public use in 1957 and completed a re-registration eligibility decision in 199863 for use in households and in topical applications to human body and clothing, cats, dogs and horses. Complications with DEET toxicity were reported in some circumstances among children and elderly people.64 – 66 Significant amounts of this chemical can be absorbed through the skin,67 and there is some evidence of neurotoxicity resulting from high-level exposure of DEET in combination with permethrin and pyridostigmin bromide (all of which were commonly used by soldiers during the Persian Gulf War).68 In addition, DEET can also dissolve plastics, and it has been described by some as having an unfavorable odor and as feeling greasy. Even with these concerns, estimates report that DEET is used by approximately 30% of the US population.69 According to a recent survey by HealthStyles, 40.3% of respondents had repellents containing DEET in the household.70 For over 50 years, DEET has maintained the status of a general-use insect repellent with minimal toxicity and safety issues.

Answer 338

The early work by Gertler on the insect repellency of N,N-diethylbenzamides (US Patent 2,408,389) in 1949, and then by McCabe et al.53 with ortho-, meta- and para- N,Ndiethyltoluamide isomers, initiated the development of today’s most widely used active repellent. Some of the early work with derivatives included ring-substitutions with hydroxyl, alkoxy, and dihalogen, which were less effective. It was the alkyl-substituted diethylbenzamides that were more active repellents.53,54,59 A trend was also seen with the number of carbons between the ring and amide group, which showed that one carbon was optimal and that an increase in the number of carbons decreased repellent activity.58 Further exploration of this class of compounds was conducted on acid amides.71 Other promising amides that were made included DEPA (N,N-diethyl phenylacetamide),53 MGK 264, MGK 326 and ethyl N-acetyl-N-butyl-3-aminopropionate (IR 3535 or MERCK 3535), formulated by Merck in 1975.

Answer 339

More recent investigations, including those by Ma et al.,73 suggest that the van der Waals surface, dipole moments, electrostatic potential and charge of the amide nitrogen, as well as the electrostatic potential of the amide oxygen, are essential for activity within this class of repellents. Interpretation of the electrostatic potential and dipole moment descriptors was that the intrinsic electrophilicity of the amide is important, and that there is an optimal range for lipophilicity or hydrophobicity (3.25–3.82 D).

Answer 340

Using a molecular overlay approach, Natarajan et al.85 compared topological descriptors to develop a stereochemical structure–activity relationship. In this model, Picaridin, SS220 and DEET shared similar structural motifs that might be useful for developing new repellents. Further, a three-dimensional quantitative structure–activity relationship (QSAR) was developed to improve on this initial model.

Answer 341

arthropod. A successful mosquito is able to locate and approach a potential host, evaluate the quality of the food source and begin feeding without alerting the host to its presence. Careful execution of this process is needed for mosquito growth and reproduction, and is controlled on different levels. Life history characteristics of the female mosquito are important for consideration, as these details often pertain to host-seeking ability.109 One major distinction is that of autogeny versus anautogeny, where some female mosquitoes emerge from the pupal state with enough protein for egg development while others require a blood meal to provide the nutritional requirements for egg maturation. In the yellow fever mosquito, Ae. aegypti, which is an example of an anautogenous female, there is a time period required for maturation and the increased sensitivity of the receptors needed for host location.

Answer 342

Pualuch: (1) primary odors, which do not change regardless of changes in an individual’s diet; (2) secondary odors, which are related to an individual’s diet and interaction in the environment; (3) tertiary odors, which arise from outside sources (e.g. lotions, hair products, make-up, etc.).

Answer 343

Carbon dioxide (CO 2 ), in contrast, elicits avoidance over a wide range of concentrations [5, 6] and acti- vates only a single glomerulus, V [5]. The V glomerulus receives projections from olfactory receptor neurons (ORNs) that coexpress two GPCRs, Gr21a and Gr63a, that together comprise a CO 2 receptor [7–9]. These CO 2 -sensitive ORNs, located in the ab1 sensilla of the antenna, are called ab1c neurons [10]. Genetic si- lencing of ab1c neurons indicates that they are neces- sary for CO 2 -avoidance behavior [5]. Whether activa- tion of these neurons alone is sufficient to elicit this behavior, or whether CO 2 avoidance requires addi- tional inputs (e.g., from the respiratory system), re- mains unclear. Here, we show that artificial stimulation of ab1c neurons with light (normally attractive to flies) elicits the avoidance behavior typical of CO 2 . Thus, avoidance behavior appears hardwired into the olfac- tory circuitry that detects CO 2 in Drosophila.

Answer 344

The demonstration that the activation of ab1c neurons by light is sufficient to elicit avoidance in a T maze, taken together with the requirement of these neurons for CO 2 avoidance [5], indicates that this behavior is exclusively mediated by ab1c ORNs and does not involve combina- torial or temporal coding of odor identity. It also indi- cates that CO 2 avoidance does not require other sen- sory input, e.g., from the respiratory system. The fact that activation of a single population of ORNs suffices to trigger avoidance further suggests that this behavior is hardwired into the olfactory circuitry that detects CO2 in Drosophila. By contrast, the concentration-de- pendent, combinatorial coding for most other odorants [3, 4, 18] allows for more flexible behavioral responses. These two classes of olfactory stimulus-response mechanisms may be thought of as analogous to innate versus adaptive immune responses [19]. Mosquitoes contain similar CO 2 receptor genes as Drosophila [7] but are attracted to this odorant; whether the CO 2 re- sponse in mosquitoes is also innate, but of opposite valence, or rather is adaptive and flexible remains to be determined.

Answer 345

Here we try all the combinations one by one to find the optimal solution. This is tedious approach because as the number of tasks and cranes go on increasing, the number of calculations also increases. The complexity is n! which is not very efficient.

Answer 346

The algorithm is easier to describe if we formulate the problem using a bipartite graph. We have a complete bipartite graph G=(S, T; E) with n worker vertices S and n job vertices (T), and each edge has a nonnegative cost c(i,j). We want to find a perfect matching with a minimum total cost.

Answer 347

In this case, the algorithm will choose the lowest cost worker to be assigned to the task as the first assignment, then choose the next lowest cost worker to be assigned to the task, and so on until all tasks have been assigned. The algorithm repeats this procedure until all workers have at least one task. Greedy algorithms try to get close to the optimal solution by improving a candidate solution iteratively, with no guarantee that an optimal solution will actually be found.`

Answer 348

- D sechellia displays selective, large expansons of non-detecting OSNs and this trait is multigenic. - These expansions are accompanied by an increase in synaptic connections OSNs and their PNs (number of PNs remains the same) - OSNs does not lead to heightened PN sensitivity but rather these pathways exhibit non-adapting PN activity upon odour stimulation. -Increase OSN numbers contribute toward persistence in plume-tracking.

Answer 349

1000, roughly classified into 50 types based on their expression of one. (Takagi_Benton, 2023)

Answer 350

Yes, th size of individual OSN populations range from 10 to 65 nurons and is stereotyped across individuals reflecting the genetically hardw-red aspect of this trait. (Takagi_Benton, 2023)

Answer 351

Multipl non exclusive reason exist. A higher number of OSNs increases basline PN activity (due to OSN spontaneous activity) and odor-evoked activity. However, the upper limit of PN activity dampens the effect of increased OSN inputs during odor stimulation at high activity. This results in a reduced difference in activity between the beginning and end of an odor stimulus which sustain the PN responses for longer.

Answer 352

At high concentrations cause an atypical action potential burst, followed by inhibition in multiple ORNs

Answer 353

A brief exposure to volatile ammonia abolishes attraction to human skin odor for several minutes ((Clark_Ray, 2023))

Answer 354

Low concentration of ammonia present in human sweat act as attractive cues for Anopheles gambiae and Aedes aegypti (Clark_Ray, 2023)

Answer 355

Grooved peg sensilla in the antenna (Clark_Ray, 2023)

Answer 356

Ammonia causes neuronal inhibition due to its high pH. (Clark_Ray, 2023)

Answer 357

The human scent emitted by the skin is produced by the microbiome resident in hair follicles and sweat glands. Human sweat glans belong to three distinct classes, eccrine, apocrine, and sebaceous whichsecrete amino acids, fatty acids, and salts, that are used as nutrients by the microbiome. The metabolization of these nutrients leads to the release of small molecules such as lactic acid ammonia and short and middle chain carboxylic acids. (Coutinho_Akbari, 2023)

Answer 358

(Coutinho_Akbari, 2023) Lactic aid and acetic acid.

Answer 359

Using a plasmi encoding a transposable element, such as Hermes, Mariner, and piggyBac, carrying a gene of interest along with a helper plasmid encoding a trasposase. Even though multiple genes were inserted in the genomes of mosquitoes, the lack of site-specific integration required the development of programmable gene-editing.

Answer 360

The zinc finger nuclease (ZFN) gene-editing strategy takes advantage of the zinc finger DNA-binding domains present in multiple transcription factors and the FokI restriction enzyme from Flavobacterium okeanokoites [3.]. As each zinc finger domain interacts with three nucleotides, the specificity of the FokI-zinc finger domain-fused protein relies upon the presence of multiple zinc finger domains (Figure 1A ) [3.]. The transcription activator-like element nuclease (TALEN) gene-editing technique relies upon the TALEs of the bacterium Xanthomonas, which bind to specific nucleotide sequences based on specific two-amino acid codes [4.]. Fusing specific TALEs to the FokI nuclease (Figure 1B) can be used to generate targeted-specific mutations

Answer 361

As components of these binary expression systems can cause toxicity, precluding more extensive application in different tissues and insect species, removing nonessential domains of the transcriptional activators was vital for the implementation of such a system for the neuronal expression of fluorescent markers in fruit flies and mosquitoes [19.]. Two versions of the QF transcription activator lacking the middle domain (QF2 and QF2w) exhibited very low toxicity and similar expression patterns to Gal4 in the Drosophila melanogaster neural system [19.]. Whereas the QF2 version induces stronger expression of the effector protein in specific neuronal classes, QF2w works best with strong promoters and for expression by multiple neuronal classes (broad expression)

Answer 362

Two versions of the QF transcription activator lacking the middle domain (QF2 and QF2w) exhibited very low toxicity and similar expression patterns to Gal4 in the Drosophila melanogaster neural system [19.]. Whereas the QF2 version induces stronger expression of the effector protein in specific neuronal classes, QF2w works best with strong promoters and for expression by multiple neuronal classes (broad expression)

Answer 363

It was inserted in-frame into the third exon of each target gene, allowing the expression of QF2 factor under the control of the natural gene promoter.

Answer 364

reverse polarity (repo), as even though these cells belong to the nervous system they do not depolarize.

Answer 365

These neurons expressed eyeless and DopR2 as cell-specific markrs.

Answer 366

The Transcriptional Activation following Arrestin Translocation (Tango) system is a sensor of neuromodulatory activities [55.,56.] that has been adapted to D. melanogaster to sense transient interactions between neuromodulators and receptors and record them by expression of a reporter molecule [55.,56.]. In fruit flies, the Tango system was built to detect the activity of dopamine in taste neurons. To do so, a transgenic fly line was constructed with a UAS binding site controlling the expression of an exogenous dopamine receptor tagged to a TEV protease cleavage site, the lexA transcription factor (tagged by the HA epitope), the 2A ribosomal skipping sequence, and the arrestin1 gene linked to the TEV protease sequence (Figure 3A ). The 2A sequence allows the generation of a bicistronic transcript that is translated into two polypeptides: (i) the dopamine receptor linked to the lexA transcription factor by the TEV protease cleavage site (TEVp cv); and (ii) arrestin1 linked to the TEV protease. The fly line also has a lexA operator (lexAop) controlling expression of the reporter fluorescent protein-encoding gene (Figure 3A). Binding of dopamine to its receptor triggers the recruitment of the arrestin1-TEV protease to the cell membrane and leads to cleavage of the TEV protease cleavage site and release of the lexA transcription factor. The latter translocates to the nucleus and binds to lexAop, inducing the expression of GFP (mCD2::GFP) (Figure 3A) [38.,39.]. In this system, expression of the UAS components was driven by a Gal4-GeneSwitch construct under the control of a pan-neuronal promoter (elav), only induced by the presence of an exogenous hormone (RU486) [56.]. With this Tango fly line, it was shown that hunger increases behavioral sensitivity to sugar by the release of dopamine onto primary taste neurons

Answer 367

The next generation of Tango design replaced the artificial transcription factor (LexA) with a deactivated version of the Cas9 nuclease (dCas9) (Figure 3B), which allows programmed control of the expression of multiple endogenous genes in response to specific extracellular signaling molecules [57.]. In this new system (CRISPR ChaCha), dCas9 is linked to beta-arrestin-2 (ARRB2) by the TEVp cv. dCas9 is also fused to transcription activators to regulate the transcription of target genes (Figure 3B). The TEV protease is then linked to the C termini of the G-protein-coupled receptor (GPCR) via the V2 tail of the arginine vasopressin receptor 2. Upon ligand binding to the GPCR, arrestin-TCS-dCas9 is recruited and cleaved by the TEV protease, releasing dCas9, which translocates to the nucleus and activates the expression of the reporter gene

Answer 368

- Odor-evoked responses in two specific IR8a glomeruli were dramatically elevated when mosquitoes were co-stimulated with Lactic acid and CO2 yet they were silent when stimulated with either ligand alone.

Answer 369

They were grossly localized in the hair-like trichoid sensilla. Also in the capitate sensilla of maxillary palp together with Gr1+ neurons.

Answer 370

They were localized and confined in grooved-peg sensilla on the antenna.

Answer 371

3Xp3 markers typically used in insect transgenesi induced both spurious reported and background fluorescence in the A. aegypti brain central brain when integrated as part of the T2A-qf2 IN FRAME FUSION CASSETTES (McMeniman, Campari paper).

Answer 372

It depended on 3 GRs: GR32a, GR33a, and Gr66a. The same GRs were required for responses to DEET when DEET was delivered not as a volatile but as a conventional taste solution. In GR32A and GR33a mutants not only was an excitatory response was absent, but an inhibitory response was observed. In GR93a mutant, DEET produces a greater response than in control.

Answer 373

Dweck_Carlson showed that these OFF responses depende on the same receptors as ON responses

Answer 374

All species of Drosophila showed OFF rsponses but there are major evolutionary shifts in the response patterns. Additionally, in D. mojavensisthere is no OFF response to SPS; the ON response is somewhat smaller than in D. melanogaster but is consistently observed. Thus, ON and OFF responses can be uncoupled over evolutionary time. (Dweck_Calrson, 2023)

Answer 375

The low firing frequency may provide a mans of increasing their sensitivity: A low concentration of tastant that elevates the firing frequency by a few spikes per second thereby produces a large fractional increase in activity. (Dweck_Carlson, 2023).

Answer 376

We found that taste neurons respond to the vapor of DEET, COU, and most members of a panel comprising 47 structurally diverse odorants. The magnitude of the responses depends on the neuron, the odorant, and the concentration; thus, the GRN repertoire provides a representation of the identity and intensity of the odorant. In summary, GRNs can function as ORNs.

Answer 377

The ecological significance of these olfactory responses is an interesting issue. The labellum is on the order of 200 to 240 μm in length in the antero-posterior direction, and sensilla range from ~15 to ~35 μm in length (16). We have found responses to DEET at distances of 1 to 50 μm (fig. S6), but, in nature, these responses to volatile compounds may be detected at greater distances depending on wind, temperature, and concentration. A taste sensillum of a fly that is exploring a potential food source in a microenvironment may often first encounter a compound via the air and shortly thereafter via contact. When contact is made, the stimulus may be part of a complex mixture that includes a wide variety of nonvolatile molecules, some of which could reduce the salience of the volatile cues. The effect of early airborne activation of taste neurons on decision-making awaits further study; in some cases, it could signal the presence of compounds at sufficiently high levels as to be aversive. In any case, our results suggest that Grs, in addition to binding a remarkable diversity of tastants, are also able to bind a wide range of odorants. Chemical compounds can evidently become solubilized in the lymph of taste sensilla and reach membrane receptors whether delivered to the sensillum via a solution or via the air.

Answer 378

The mosquito exoskeleton contains waxes and polysaccharides that prevent water loss across cuticle. The loss of water can be mitigated through change in body size, metabolism, composition of cuticular hydrocarbons, and a variety of behavioral and biological adjustment including adjustment in expression of aquaporin-2.

Answer 379

- They identified two genetically diverse lines of Ae. aegypti from Senegal with difference in dessication tolerance and Zika virus susceptibility. -Identified a gene AePer50 encoding a peritrophin protein. -AePer50 is required to limit midgut infection across arbovirus families.

Answer 380

Accoti_Dickson (2023): are expressed in the peritrophic matrix, a chitinous sac that envelops the blood bolus following a blood meal.

Answer 381

- Many odorant receptors responded to indole like compounds that affect Ae. aegypti behavior. - ORs responded to blends of chemical compounds. While there is some responsiveness to multiple blends by ORs, all demonstrated a pronounced specificity for one blend over the others.

Answer 382

4-chromanone (indole)

Answer 383

1-octen-3-ol (alcohol)

Answer 384

3-methylindole (indole)

Answer 385

cis-deca-hydro-1-napthol (and fenchone) terpenes

Answer 386

4-ethyl-phenol (indole)

Answer 387

1-hexanol (phenethyl proprionate) and alcohol

Answer 388

tetrahydrolinalool

Answer 389

farnesol (alcohol)

Answer 390

2,3-dimethylindole (indole)

Answer 391

4-quinolinecarboxaldehyde

Answer 392

TRPA1 acts internally to control the slowly developing preference response of flies exposed to shallow thermal gradient. - The rapid response of flies exposed to a steep warmth gradient does not require #TRPA1 but rather the gustatory receptor #GR28B

Answer 393

The arista #arista contains six neurons: three warmth-responsive HC neurons and three cool-responsive neurons.

Answer 394

In flies, high salt avoidance is driven by both "bitter" taster neurons and a class of glutamatergic "high salt neurons" expressing #Ppk23.

Answer 395

Generally, sodium activates attractive taste cells, but attraction is overridden at high salt concentrations by cation non-selective activation of aversive taste cells. Higher concentrations of any salt activate two aversive GRN populations that override sodium attraction: bitter GRNs labeled by #GR66a and a population of #ppk23

Answer 396

#IR7c is expressed in glutamatergic high salt neurons, where it functions with co-receptors neurons, which endogenously express #IR76b and #IR25a, confers responsiveness to non-sodium salts. IR7c is expressed in high salt neurons and is essential for their repsonses to NaCl and KCl (it responds dose-dependently to increasing concentrations of both salts, exhibiting lack of sodium selectiviy characteristic of high-salt cells).

Answer 397

IR7c did not respond to sugar, bitter compounds, acetic acid, or a mxiture of amino acids, demonstrating their specificity for salt. IR7c salt tuning, however, was broad, with strong responses to all salt species tested. Interestingly, while IR7c mutants showed complete loss of responses to all monovalent salts tested, there was no effect on the detection of CaCl2 and McCl2. This suggests that IR7c is specifically required for the detection of monovalent cations.

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