CHAPTER 7: CHEMICAL FIXATIVES PART 3

Question 1

• Common metallic fixative (5-7%)
• Widely used as secondary fixative
• Used as alternative to formaldehyde-based fixatives to overcome poor cytological preservation and include such well-known fixatives such as B- 5 and Zenker’s
• Tissues fixed with mixtures containing mercuric chloride (except Susa) contain black precipitates of mercury.
• Treating the section with 0.5% iodine solution in 70% ethanol for 5- 10 minutes

Answer 1

Mercuric Chloride

Question 2

Advantages of Mercuric Chloride

Answer 2

1. It penetrates and hardens tissues rapidly and well.
2. Nuclear components are shown in fine detail.
3. It precipitates all proteins.
4. It has a greater affinity to acid dyes and is preferred in lieu of formaldehyde for cytoplasmic staining
5. Trichrome staining is excellent
6. It is the routine fixative of choice for preservation of cell detail in tissue photography.
7. It permits brilliant metachromatic staining of cells.
8. It is recommended for renal tissue, fibrin, connective tissue and muscle.

Question 3

Disadvantages of Mercuric Chloride

Answer 3

• It causes marked shrinkage of cells (this may be counteracted by addition of acid).
• It rapidly hardens the outer layer of the tissue with incomplete fixation of the center; therefore, thin sections should be made.

Question 4

Compound solutions containing this fixative deteriorate rapidly upon addition of glacial acetic acid to formalin. Also, it is extremely corrosive to metals.

Answer 4

Mercuric Chloride

Question 5

Fixation time for Zenker’s solution

Answer 5

12-24 hours

Question 6

• It produces a fairly rapid and even fixation of tissues.
• Stock solutions keep well without disintegration.
• It is recommended for trichrome staining.
• It permits brilliant staining of nuclear and connective tissue fibers.
• It is recommended for congested specimens (such as lung, heart and blood vessels) and gives good results with PTAH and trichrome staining.
• It is compatible with most stains
• It may act as a mordant to make certain special staining reactions possible
• It is a stable fixative that can be stored for many years.

Answer 6

Zenker’s Solution

Question 7

Disadvantages of Zenker’s Solution

Answer 7

1.. Penetration is poor
2. It is not stable after addition of acetic acid
3. It causes lysis of red blood cells and removes iron from hemosiderin.
4. It does not permit cutting of frozen sections.
5. It has the tendency to form mercuric pigment deposits or precipitates.
6. Tissue must be washed in running water for several hours (or overnight) before processing. Insufficient washing may inhibit or interfere with good cellular staining

Question 8

Done by oxidation w/ iodine to form mercuric iodine,
which can be subsequently removed by treatment with sodium thiosulfate

Answer 8

De-zenkerization

Question 9

Excellent for BM, extramedullary hematopoiesis and intercalated discs of cardiac muscle

Answer 9

Zenker-Formol (Helly’s) Solution

Question 10

It produces mercury pigment which should be removed from sections prior to staining and it can
produce chrome pigment if tissue is not washed in water prior to processing

Answer 10

Zenker-Formol (Helly’s) Solution

Question 11

T/F: Lillie’s B-5 Fixative is an excellent microanatomic fixative for pituitary gland, bone marrow and blood containing organs such as spleen and liver.

Answer 11

False (Zenker-Formol (Helly’s) Solution)

Question 12

T/F: Nuclear fixation and staining with Zenker’s solution is better than with Helly’s.

Answer 12

False (Helly’s is better)

Question 13

Despite its mercuric chloride content and consequent problems with disposal, this solution is popular for fixation of hematopoietic, bone marrow
biopsies and lymphoid tissue.

Answer 13

Lillie’s B-5 Fixative

Question 14

• Recommended mainly for tumor biopsies especially of the skin
• Excellent cytologic fixative
• 3-12 hours fixation time
• It penetrates and fixes tissues rapidly and evenly
• It produces minimum shrinkage and hardening of tissues due to the counter-balance of the swelling effects of acids and the shrinkage effect of mercury.
• It permits most staining procedures to be done, including silver impregnation, producing brilliant results with sharp nuclear and cytoplasmic details.
• It permits easier sectioning of large blocks of fibrous connective tissues

Answer 14

Heidenhain’s Susa Solution

Question 15

Susa-fixed tissues may be transferred directly to
95% alcohol or absolute alcohol, thereby (reducing/increasing) processing time.

Answer 15

reducing

Question 16

Disadvantages of Heidenhain’s Susa Solution

Answer 16

1. Prolonged fixation of thick materials may produce considerable shrinkage, hardening and bleaching; hence, tissues should not be more than 1 cm. thick.
2. RBC preservation is poor
3. Some cytoplasmic granules are dissolved.
4. Mercuric chloride deposits tend to form on tissues; these may be removed by immersion of tissues in
   alcoholic iodine solution
5. Weigert’s method of staining elastic fibers is not possible in Susa fixed tissues