INFILTRATION/EMBEDDING

Flashcards for Histopathologic & Cytologic Techniques - Infiltration & Embedding

What is the purpose of infiltration/impregnation in tissue processing?

To remove clearing agent from tissues and fill up cavities and tissue spaces, providing a firm consistency for easy cutting.

Why is it important to fill up tissue cavities and spaces during infiltration?

To give the tissue a firm consistency, which facilitates easy cutting.

What is the most commonly used infiltration method?

Paraffin wax infiltration method.

List two advantages of using paraffin wax infiltration.

Rapid process and compatibility with any staining procedures; allows cutting of serial sections.

What are some disadvantages of paraffin wax infiltration?

Prolonged process may cause excessive shrinkage and tissue hardening; inadequate process may cause retention of clearing agent; NOT FOR fatty tissue.

Why is paraffin wax not suitable for fatty tissues?

Because the process involves heat, which will dissolve fats.

What is the melting point for paraffin wax used in routine work?

56°C

Name three methods of paraffin wax impregnation.

Manual, automatic, and vacuum.

Describe the manual method of paraffin wax impregnation.

Carried out using paraffin wax infiltration, requires an oven to keep the wax melted, and requires 4 changes of wax in 1 hour (15 minutes interval).

What is an autotechnicon used for?

Automatic paraffin wax impregnation, which is more rapid due to heat generation and constant agitation.

Why is vacuum infiltration considered the most rapid process?

Because it is a paraffin wax infiltration under negative atmospheric pressure inside the oven.

For what types of specimens is vacuum infiltration recommended?

Urgent biopsies and specimens like lungs, brain, eyes, spleen, and CNS.

Name three substitutes for paraffin wax.

Paraplast, Embeddol, Bioloid, Ester wax, Tissue mat, Carbowax.

What is the melting point of Paraplast?

56-57°C

What types of samples typically use Paraplast?

Bones and brains specimen

What is an advantage of ester wax?

It is soluble to alcohol, does not require clearing only dehydration

What is an advantage and a disadvantage of Carbowax?

Advantage: no longer requires dehydration and clearing; Disadvantage: difficult to float out when cutting

What is Celloidin also known as?

Collodion

What is Celloidin made of?

A purified form of nitrocellulose, soluble to alcohol and ether.

For what type of tissues is Celloidin infiltration suitable?

Tissues with large and hollow cavities that tend to collapse.

Is heat applied during Celloidin infiltration?

No, there is no heat application.

Describe the solutions used in Celloidin infiltration.

2, 4, 8% solutions dissolved in equal parts of ether and alcohol.

What are some disadvantages of celloidin infiltration?

Very slow process; thin sections; sections for photomicrography are all difficult to obtain.

What are the three types of Celloidin infiltration?

Thin Celloidin, Medium Celloidin, and Thick Celloidin.

What percentages are used in the three types of Celloidin?

2-4% (Thin), 4-6% (Medium), 8-12% (Thick).

What is Wet Celloidin mainly used for?

Infiltration of bone, brains, teeth, and whole organs.

What is used for storage for Wet Celloidin?

70% alcohol

What is Dry celloidin used for?

Infiltrating eye specimen

What is used for storage when using Dry Celloidin?

Gilson’s Mixture (combination of chloroform and cedarwood oil)

What is Nitrocellulose Method?

Another form of celloidin soluble in equal concentrations of ether and alcohol; highly explosive

What is added to Nitrocellulose to prevent cracking of tissue?

Plasticizers: Oleum ricini & castor oil

When is Gelatin Infiltration Method recomended?

Frozen section; also, for histochemical and enzyme studies

What is an advantage of using Gelatin Infiltration Method?

Water soluble (no longer required dehydration and clearing); low melting point

What is the recommended thickness of tissue samples for gelatin infiltration?

2-3mm thick

What concentration of formalin is used to harden gelatin-embedded tissues?

l 0% formalin for 12-24 hours

What does 1% phenol serve to prevent?

The growth of molds

What occurrs during Embedding/Casting/Blocking?

Placing infiltrated tissue in a mold containing the embedding medium which is allowed to solidify.

What are the requirements for Embedding/Casting/Blocking?

Embedding mold (paraffin wax commonly used), medium and infiltrated tissue.

When the Paraffin wax is used in embedding, how should the temperature be?

5-10° above its melting point

After embedding how is solidification of the block reached?

Place the preparation inside the refrigerator at -5° or immerse it in cold water

What is Trimming?

Cutting off excess paraffin wax to form a four-sided prism.

What is Double embedding?

Infiltrate using celloidin then embedding using paraffin wax

What are Leuckhart's embedding molds?

Consist of 2 L- shaped strips of heavy brass or metal, can produce block of different sizes and recommended for routine use

When are Compound embedding unit used?

If there is a need to embedded more than 1 specimen

What does Tissue Tek equip you with?

A warm plate to manage the impregnated specimen, and a cold plate at -5°C for rapid solidification of the block.

What is an advantage of disposable Peel away molds?

It can produce perfect block even without trimming

Advantage of paper boats when embedding?

Cheap and easy to make (economical)

When embedding are plastic ice trays recommended for?

Busy routine laboratories

What are Plastic Resins used for?

Embedding for EM, High Resolution Light Microscopy (tissue sections thinner than the usual 4-6 µm, such as renal biopsies a n d bone marrow biopsies), For extremely hard tissues

Example of Expoxy?

Bisphenol (Araldite), Glycerol (Epon) and Cyclohexene dioxide (Spurr)