PRELIM: CH11 IMPREGNATION AND EMBEDDING (5)

Without prior clearing of the tissue

An unusual advantage of Ester Wax is that it can be used for impregnation:

It is relatively hard.

Why does Ester Wax require a heavy-duty microtome?

Plastic polymers, mostly polyethylene glycols

Water-soluble waxes are primarily:

It is miscible with water, so dehydration and clearing are not required.

What is a major advantage of Carbowax?

18 or more carbon atoms

Carbowax is commonly composed of polyethylene glycol containing:

Does not remove neutral fats and lipids during processing.

A major advantage of Carbowax for lipid studies is that it:

It avoids excessive heat, hardening, shrinkage, and brittleness.

Why is Carbowax useful in some enzyme histochemical studies?

Its extreme water solubility makes sections difficult to float and mount.

What is a major problem associated with Carbowax during section floating?

Soap

Which substance may be added to water to help reduce distortion and promote flattening of Carbowax sections?

Dimethyl sulfoxide

DMSO stands for:

Scavenging residual transition solvent and improving tissue permeability

What is one proposed function of DMSO in plastic polymer paraffin waxes?

Nitrocellulose

Celloidin is a purified form of:

Have large hollow cavities or are hard and dense, such as bones and teeth

Celloidin is especially useful for specimens that:

Thin 2%, medium 4%, and thick 8% solutions

Celloidin solutions are commonly available in:

Ether and alcohol

The solvents used in celloidin solutions are:

It provides rubbery support with minimal tissue distortion.

A major advantage of celloidin is that:

Whole eye or large brain section

Which tissue is particularly well suited to celloidin embedding?

Its rubbery support helps prevent collapse and separation of delicate structures.

Why is celloidin useful for eye sections?

Processing may take several days, weeks, or even longer.

A major disadvantage of celloidin is that:

Very thin sections

Compared with paraffin, celloidin generally makes it more difficult to cut:

Dehydration should be avoided, especially for histochemical or enzyme studies.

Gelatin impregnation is most useful when:

Delicate specimens and frozen tissue sections

Gelatin is particularly useful for:

It helps prevent fragmentation of tough or friable tissue during frozen sectioning.

Why does gelatin help delicate frozen specimens?

To prevent mold growth

Why is 1% phenol added to the gelatin solutions?

Paraffin is the routine medium; celloidin is useful for hard, delicate, or hollow specimens; gelatin is useful when dehydration should be avoided; and plastic resins are valuable for high-resolution studies and hard tissues.

Which statement best compares the major embedding media discussed in this chapter?