Cryostat

Question 1

What is the cause of the “freezing artifact” described?

Answer 1

It is caused by improper freezing of the tissue. The tissue should be “snap frozen” to prevent this.

Question 2

If you see an ice crystal artifact in your tissue, can it be corrected?

Answer 2

No, it cannot be corrected.

Question 3

How can the “freezing artifact” be prevented? (List three methods)

Answer 3

Use a heat extractor.

Freeze with isopentane at -150°C.

Use another method of rapid freezing.

Question 4

What should you NOT do to tissue before freezing to avoid artifacts?

Answer 4

The tissue must not be immersed in saline before freezing.

Question 5

What is a common reason for the tissue block loosening from the chuck while sectioning?

Answer 5

The chuck was too cold when the embedding medium was applied.

Question 6

How can you correct a block that has loosened from the chuck?

Answer 6

Re-attach the tissue block with additional embedding medium.

Question 7

What are two key preventative measures to keep a block from loosening?

Answer 7

Maintain the temperature of both the chuck and the embedding medium.

Do not store chucks in the cryostat without embedding medium.

Question 8

What is the primary risk of not embedding tissue flat on the chuck?

Answer 8

The risk of cutting too deep and losing important parts of the tissue.

Question 9

Describe the “slide method” for ensuring tissue is embedded flat on the chuck.

Answer 9

Place the tissue on a slide and surround it with embedding medium.

Place the slide on the freezing bar of the cryostat to freeze.

Coat the specimen chuck with embedding medium and invert it over the tissue.

Allow the tissue to freeze onto the chuck, then remove the slide.

Question 10

What tool, also mentioned for preventing freezing artifact, can help embed tissue flat?

Answer 10

A heat extractor.

Question 11

What is the primary mechanical device that, if maladjusted, causes tissue to curl or roll?

Answer 11

A poorly adjusted anti-roll plate.

Question 12

What happens if the anti-roll plate is too warm?

Answer 12

The sections will not stick to it.

Question 13

What happens if the anti-roll plate is too far above the blade edge?

Answer 13

The sections will rub against the plate.

Question 14

What happens if the anti-roll plate is too far below the blade edge?

Answer 14

The sections will not slide between the blade and the plate.

Question 15

How should the anti-roll plate be correctly positioned?

Answer 15

It should be parallel to and very slightly above the blade facet.

Question 16

Aside from adjusting the anti-roll plate, name a technique to correct a section that is already curling.

Answer 16

Use a fine, cold paintbrush to gently flatten the curled tissue.

Question 17

What are two other conditions of the cutting blade that can help prevent curling?

Answer 17

The cutting blade should be cold and sharp.

Question 18

Besides blade temperature and sharpness, what is the third key factor in preventing tissue from curling at the blade edge?

Answer 18

Using a properly positioned anti-roll plate.