microscopy & animal models

Question 1

what is extrapolatable refer to in terms of data

Answer 1

the ability to infer the unknown form the known : predicting human data by relying on animal data

Question 2

what is fidelity & discrimination in terms of data extrapolation

Answer 2

fidelity - how close a model is to the organism or condition we are studying in our target species
discrimination - means the extent to which the model reproduces one particular property of the original

Question 3

what are the advantages of using a rodent model

Answer 3

• complex behaviours
• organs homologous to humans
• genetic similarity to humans

Question 4

what is the disadvantages of using model rodents

Answer 4

• very expensive husbandry costs
• experimental cycle long
• ethical constraint

Question 5

what are advantages of using zebrafish

Answer 5

• high reproductive rate
• development is external in embryos
• genetic similarity to humans
• embryos & larvae are transparent a
• possibility to study complex behaviours

Question 6

what are disadvantages of using zebrafish

Answer 6

• moderate predictivity
• moderate translational value

Question 7

what are advantages of using fruit flies

Answer 7

• easy to work with
• short generation time (10 days from fertilised egg to adult)
• low cost of maintenance
• small genome, 4 chromosomes
• useful model to study behaviours such as aggression, sex drive, motivation & insomnia

Question 8

what are disadvantages of using fruit flies

Answer 8

• genetically distant from humans
• relatively simple anatomy (100,000 neurons can also be an advantage)
• no adaptive immune system

Question 9

wht are the three Rs in ethical considerations

Answer 9

replacement, reduction, refinement

Question 10

what do in vitro models differ in compared to in vivo

Answer 10

• presence of biomaterials
• presence of physical and chemical cues such as fluid flow offered by microfluidic devices
• compartmentalizatoin of the cell cultures

Question 11

what are 2d cell cultures

Answer 11

cells/cell lines that can be maintained in culture for an extended period of time

Question 12

what are spheroids

Answer 12

characterised by an agglomeration of cells, formed spontaneously or by force when they are cultured in a way that they are unable to attach to a substrate material

Question 13

what are organoids

Answer 13

also formed of cell aggregates but the cells are capable of self organising and differentiating within the aggregate, creating an organ like structure and mimicking some of its functions

Question 14

what are scaffold based cell culture

Answer 14

they use scaffolds as a support where cells are seeded on top or embedded in the biomaterial

Question 15

what is a brain-on-a-chip model?

Answer 15

an effort to mimic the structural and functional aspects of brain tissue within a miniaturized engineered platform

Question 16

what are the four microscope techniques based on scattering. reflection & absorption

Answer 16

brightfield, darkfield, phase contrast, differential interference contrast (DIC)

Question 17

what is the principle of brightfield microscopy

Answer 17

light passes directly through or is reflected off a specimen. difficult to differentiate unless artifically stained or naturally pigmented

Question 18

what is the principle of darkfield microscopy

Answer 18

direct light is blocked by an opaque disk, specimen is illuminated using oblique rays of light. produces a white image on a dark background

Question 19

what is the principle of differential interference contrast microscopy

Answer 19

same principle as phase contrast, but higher resolution & reducded image artefact. gives 3d effect

Question 20

what is the principle of phase contrast microscopy

Answer 20

amplifies any refraction into larger insensity differences with high contrast that can be easily seen

Question 21

what are microscopy techniques based on fluoroscence

Answer 21

epifluorescence (widefield), confocal, two photon, light sheet, microscopy in behaving animals

Question 22

what are the general principles of fluoresence microscopy

Answer 22

use fluorophores that have the property of absorbing light at a specific wavelength and then emitting light as a longer wavelength

Question 23

what are disadvantages of epifluorescence microscopy

Answer 23

can have hazy out of focus images that appear blurry and lack contrast

Question 24

what are advantages of confocal microscopy?

Answer 24

• accurate resolution in 3d
• discrimination of multiple flurorophores
• possibility of automated image analysis

Question 25

what are disadvantages of confocal microscopy?

Answer 25

• expensive
• high illumination & long acquisition time

Question 26

what are advantages of two photon microscopy

Answer 26

• imaging of deeper structures
• less photobleaching as excitation is limited to a focal point

Question 27

what is photobleaching

Answer 27

the intensity of the light emitted from a flurophore will decrease over time as it is continuously exposed to light

Question 28

what are advantages of light sheet fluorescent microscopy

Answer 28

• combines the speed of wide field imaging with optical sectioning and low photobleaching

Question 29

what are disadvantages of light sheet fluorescent microscopy

Answer 29

• expensive
• unsuitable for tissue with strong light scattering property

Question 29

what is tissue clearing used for

Answer 29

making large fixed biological samples transparent to allow for a clearer image

Question 30

what fluorescent probe is usually used to visualize dynamic signals in live animals

Answer 30

GCaMP is a genetically encoded calcium indicator used as a proxy for electrical activity

Question 31

what are GRIN ‘gradient index’ lens usually used for

Answer 31

optical lenses that can be implanted into a brain to provide an optical access to the neurons of interest