Michaelmas week 2

Question 1

What is digital imaging and why are cameras cooled, which samples is this especially important for?

Answer 1

Relies on digital cameras based on CCDs
Cameras are cooled to reduce noise levels so faint signals can be detected
Important for fluorescence samples

Question 2

What are advantages of digital imaging?

Answer 2

1) Record data and save for subsequent analysis

2) Images can be manipuated and analysed digitally allowing quantitative analysis

Question 3

What is deconvolution?

Answer 3

A technique allowing reversal of optical distortion in an ordinary microscope image

Question 4

What is the difference between bright-field and phase contrast microscopy?

Answer 4

Bright field - allows you to view structures that absorb incident light
Phase contrast - enhances contrast by influencing the optical path of light
Different parts of a specimen have different optical density so light passes more slowly through dense areas
Phase changes get converted into changes in amplitude which we detect as light and dark

Question 5

How do you get phase contrast on the microscope?

Answer 5

Rotate condenser turret disc to Ph1/2/3

Question 6

Draw a transverse acinus and pancreas under low power

Answer 6

(See notes for diagram)

Question 7

How long is an acinus cell?

Answer 7

15 micrometres diameter

Question 8

What stain do you use to look at the zymogen?

Answer 8

Toluidine blue –> stains nuclei and zymogen blue

Zymogen granules have lots of protein ready to secrete to the lumen

Question 9

Zymogen granules are clustered at one cell edge so cells are…

Answer 9

Polarised

Question 10

Name region where granules are located

Answer 10

Apical region

Question 11

How can you test if pyronin really stains RNA?

Answer 11

Treat section with RNAase and see if pink sections go

Question 12

What happens to the pieces of guinea pig pancreas prior to making the slides?

Answer 12

They are: 1) fixed 2) dehydrated 3) embedded in paraffin wax 4) sectioned

Question 13

Why is histoclear added

Answer 13

To remove the paraffin wax

Question 14

What are stages of making the slides?

Answer 14

1) add histoclear
2) Add ethanol and distilled water
3) Add methyl green/pryonin stain
4) Blot with filter paper
5) Leave to dry
6) add mounting medium and lower coverslip
7) leave on hot plate

Question 15

What kingdom is amoeba?

Answer 15

Protozoan

Question 16

Draw pic of slide view from above

Answer 16

(See notes for diagram)

Question 17

Draw amoeba under 10x magnification

Answer 17

(See notes for diagram)

Question 18

How is movement of pseudopodia produced?

Answer 18

By cytoskeleton

Question 19

How does amoeba ingest food particles?

Answer 19

By ingesting them in food vacuoles (phagocytosis)

Question 20

What is the contractive vacuole and how does it control its water content?

Answer 20

A clear spherical vesicle that periodically evacuates its contents then grows again to full size
It controls its water content by pumping out water that enters osmotically

Question 21

How big are cheek cells?

Answer 21

50 micrometres diameter (1/4 amoeba)

Question 22

What does the pattern on cheek cell surface reflect?

Answer 22

Ripples in the cell surface that increase cell sa, function unclear
Cells secrete mucin so the ridges may hold a layer of mucus in place

Question 23

What are dark objects on the cheek cell slide?

Answer 23

May be bacteria in swab