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Industrial Toxicology > Pesticides > Flashcards

Flashcards in Pesticides Deck (72):
1

OPs

Inhibit AChE, esters of phosphoric acid, much more acutely toxic and less persistent than OCs

2

Sulfur

aracicide/fungicide, H2S binds to cytochrome oxidase (complex IV) on the heme where O2 binds, stops production of O2-->H20, creates H+ gradient, inhibits oxy phos

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Arsenite

As(III) inhibits respiratory enzymes, proteotoxic effects, thiol reactive

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Arsenate

As(V) phosphate analog, inhibits ATP synthesis, uncouples oxy phos, inhibits respiratory enzymes, proteotoxic

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mercury

Hg(II) complexes with two S molecules, breaking disulfide bonds, interferes with protein structure, enzymes function, membrane integrity

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Boric acid

H3BO4, soil tox reference, stomach poison, cuticle damage in insects

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OCs

chlorinated diphenyl aliphatic structures; dichlorophenylethanes, cyclodienes, cyclohexanes

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Dichlorodiphenylethane, a class of OC insecticides

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Cyclodienes, a class of OC insecticides

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Cyclohexanes

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dichloro-diphenyl-trichloroethane

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DDT acute

Dichloro-diphenyl-trichloroethane; acute: neuronal hypersensitivity leading to cell exhaustion, extends after potential and delays repolarization

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DDT chronic

Dichloro-diphenyl-trichloroethane; chronic most through DDE: hormone mediated, feminization, weak ER agonist, AR antagonist, demasculinization

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DDT acute sites of action

(1) reducing k+ pore transport

(2) inactivate Na+ channel closure

(3) inhibit Na/K, Ca-ATPases

(4) calmodulin-Ca binding with the release of NTs

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Methoxychlor

DDT replacement, similar mechs as DDT, less persistent, more readily metabolized, similar to DDE as an EDC, banned

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methoxychlor

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DDE

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Cyclodienes

class of OC insecticide derived from hexachloropentadiene (6Cl, pentagon), soil and seed treatment, very persistent, most toxic group of OCs

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Polychloroterpenes

group of OCs, toxaphene most common, CNS toxicant, banned

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Polychloroterpenes

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Hexachlorocyclohexane

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Mechs of cyclodiene, g-HCH, and toxaphene

Mainly act on GABA NTs: Cl ion transport through inhibition of GABAr, inhibition of Ca-Mg ATPases. effect is build up of Ca-->NTs don't release. inhibit inhibitory NTs, AP fires. 

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Where does ACh binds to on AChE? Where will OPs and Carbamates bind to on AChE

ACh binds to the esteratic and anionic sites. OPs anc carbamates only bind to the esteratic site.

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carbamate

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OP, X is toxic leaving group, R1 and R2 are typically aryloxy or alkoxy (also influence tox)

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Symptoms of OP poisoning

SLUD from overactivation of parasympathetic, anxiety and tension from somatic motor nerve fibers

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OP poisoning treatment

Atrapine is a mAChR antagonist

Pralidoxime reactives AChE (don't use with carbamates) 

Benzodiazepines relieve anxiety and seizures

29

OP chronic 

neurophysiological and behavioural effects: limb weakness (Jake leg), memory, motor and academic skills 

30

OP mech hypotheses

(1) initiation of neuropathy target esterase

(2) desensitization/downregulation of cholinergic receptors in PNS/CNS

(3) altered nicotinic/muscarinic autoreceptor function (4) alterations to high affinity uptake transporters

31

nicotine

broad spectrum insecticide, acts as a post-ganglionic nAChR agonist, not degraded by AChE, paralysis of respiratory muscles

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Three chemical classes of neonics

nitroguanidines, nitromethylenes, N-cyanamides

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Nitroguanadine, class of neonic

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Nitromethylene, class of neonic

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N-cyanamide

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Neonics

hydrophilic nAChR agonists, influx of Na+, only target invertebrates due to nAChR charge differences, only 5% of active ingredient makes it to crop

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Rotenone

botanical derivative, insecticide, piscicide, neutralize with KMnO4, rapidly photodegraded, inhibits flow of E in ETC, inhibits transfer of e- from Fe-S group in complex I to ubiquinone preventing transfer of H+ and thus throws off oxidation of NADH to NAD

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Pyrethrum

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Pyrethrum

extracted from Chrysanthemum, photolysis, requires a synergist to inhibit CYP, used in homes, rapid mammalian metabolism (detox by CYP)

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Pyrethroids

synthetic insecticdes modelled after pyrethrum but with greater efficacy, comes in four generations, all affect sodium channels, can also work by inhibition of Ca/Mg-ATPases, inhibition of calmodulin, and inhibition of GABA Cl- channels

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Allethrin

first gen pyrethroid derived from cinerin I, requires a synergist but more stable

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Tetramethrin and resmethrin

2nd gen pyrethroids with greater efficacy, require synergist

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Fenvalerate and permethrin

3rd gen pyrethroids, stable in sunlight, don't require a synergist

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cypermethrin and decamethrin

4th gen pyrethroids, photostable, don't need a synergist, high efficacy, long residual effects

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1st and 2nd gen pyrethroids

cause repetitive neuronal discharges by holding channels open, produce inappropriate APs, irritable neurons, require a synergist

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3rd and 4th gen pyrethroids

do not cause repetitive discharges, they hold channels open for even longer causing persistent depolarization and thus increasing the refractory period of the neuron (hypersenstivity) and then preventing subsequent firing 

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Why is Bt toxin not of concern in vertebrates?

Bt toxin requires activation by an alkaline gut, vertebrates have acidic guts

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Avermectins

marcocyclic lactone toxins produced by Streptomyces avermetilis. degrade by photolysis, produce rapid paralysis then slow death. Bind to glutamate-gated Cl- channels, increase cell permeability to Cl-, hyperpolarization causing firing then paralysis

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Three main compounds used in avermectins

  1. ivermectin as a nematicide, antiparasite
  2. abamectin controls fire ants, mites
  3. emamectin is a food additive to treat sea lice

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Avermectin

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derived pyrethrum

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Type I pyrethroids

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type II pyrethroids

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2,4-D

dichlorophenoxyacetic acid

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2,4,5-T

trichlorophenoxyacetic acid

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What are the three forms of 2,4-D and which penetrates the best?

Ester, acid, and amine. The ester penetrates the best.

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Phenoxy herbicides

2,4-D; 2,4,5-T; MCPA;

mimic growth hormones causing growth defects, don't kill monocots

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Phenoxy herbicide mammal toxicity and treatment and exposure risk

  1. muscle damage
  2. reduced ribonuclease synthesis
  3. uncouples oxy phos
  4. Treat by washing area, activated charcoal
  5. most exposure risk focused on repeated spray exposure

60

Paraquat

Highly toxic, hydrophilic, non-volatile, photodegradable, poisonings cannot be treated: some kidney damage, big target is lungs (fibrosis) oxidized to a free radical in lungs and does lipid peroxidation 

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Glyphosate

non-volatile, broad-spectrum, modified amino acid (glycine), doesn't bioaccumulate, microorganisms love it, inhibits photosynthesis

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Name a persistent herbicide

Picloram

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Pentachlorophenol

fungicide, herbicide, wood treatment, rapidly absorbed, detox with glucuronide conjugation, uncouples oxy phos, immunosuppressant, treated with cold water and activated charcoal 

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Strychnine

An alkaloid derived from a plant in India, rapidly aborbed (low Ka), competitive antagonist of glycine (inhibitory NT of spine, strychnine causes excitation), become extemely sensitive to external stimuli, seizures, die of lack of oxygen cause can't move diaphragm, treat with sedation, act. char, KMnO4

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Diphacinone and Brodifacoum

2nd gen anticoagulant rodenticides of warfarin, more persistent, protein boudd, well-absorbed, take a week for effects

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mech of action of diphacinone and brodifacoum

clotting factors II, VII, IX, and X, and inhibition of vitamin K1

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What common medicinal, antimicrobial ingredient increases the bioavailability of rodenticides and what two ways does it do this by?

Sulfonamide decreases vitamin K synthesis and protein binding

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Fluoroacetate

targets krebs cycle, replaces acetyl-coA, O2 isn't utilized, requires metabolic activation (symptoms after 2 hours), blocks energy production and cellular respiration, Ca ketoglutarate is best treatment 

69

Zinc phosphate 

Rodenticide and insecticide (fumigant), irritates stomach so rats avoid it, phosphine (PH3) is what's nasty, liver damage, needs to react with HCl

70

alpha-napthyl thiourea (ANTU)

rats sense irritation, people will vomit it up, not persistent, increases lung permeability in pulmonary capillaries leading to pulmonary edema

71

vitamin D3 / cholecalciferol

alter calcium homeostasis, moves from bones to blood, high doses lead to metastatic calcification, treated with act. char., steroids, lipid emulsion, but best with calcitonin

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thallium

metal mined in BC, rapidly absorbed, slowly eliminated, decrease oxy phos, see hair loss and red gums, treat with chelation therapy