CHAPTER 7: CHEMICAL FIXATIVES PART 5 Flashcards
- Used in 1-2% aqueous solution, usually as a constituent of a compound fixative
- It precipitates all proteins and adequately preserves carbohydrates
Chromic Acid
- Used in a 3% aqueous solution
- Fixes bur does not precipitate cytoplasmic structures
- Preserves lipids
- Preserves mitochondria
Potassium Dichromate
- Penetrates tissues well
- Harden tissues better and more rapidly than Orth’s fluid
- Recommended for the demonstration of chromatin, mitochondria, mitotic figures, Golgi bodies, RBC
and colloid-containing tissues
Regaud’s (Muller’s) Fluid
Disadvantages of Regaud’s (Muller’s) Fluid
- It deteriorates and darkens on standing due to acidity; hence, the solution must always be freshly prepared
- Penetration is slow, hence, tissues should not be thicker than 2-3 mm.
- Chromate-fixed tissues tend to produce precipitates
of sub-oxide, hence should be thoroughly washed in running water prior to dehydration - Prolonged fixation blackens tissue pigments, such as melanin; this may be removed by washing the tissues in running tap water prior to dehydration.
- Glycogen penetration is poor; it is therefore, generally contraindicated for carbohydrates.
- Nuclear staining is poor.
- It does not preserve fats.
- It preserves hemosiderin less than buffered formalin
- Intensity of PAS reaction is reduced.
- It is recommended for study of early degenerative processes and tissue necrosis.
- It demonstrates rickettsiae and other bacteria.
- It preserves myelin better than buffered formalin
Orth’s Fluid
- For embryos and pituitary biopsies
- Preserves glycogen well but usually lyses
erythrocytes. - It is sometimes recommended for gastro-intestinal
tract biopsies, animal embryos and endocrine gland tissue - Excess picric should be washed from tissues prior to staining with 70% ethanol
Bouin’s Solution
Advantages of Bouin’s Solution
- It is an excellent fixative for glycogen
demonstration. - It allows brilliant staining with the trichrome method.
- It is suitable for Aniline stains (Mallory’s,
Heidenhain’s or Masson’s methods) - It precipitates all proteins.
- It is stable.
Advantages of Bouin’s Solution
- It is an excellent fixative for glycogen
demonstration. - It allows brilliant staining with the trichrome method.
- It is suitable for Aniline stains (Mallory’s,
Heidenhain’s or Masson’s methods) - It precipitates all proteins.
- It is stable.
It causes RBC hemolysis and reduces the amount
of demonstrable ferric iron in tissue
Bouin’s Solution
Picric acid is highly explosive when dry, and
therefore must be kept moist with distilled water or saturated alcohol at ______% concentration during storage.
0.5 to 1
Bouin’s solution interferes with ____ method of staining; hence, tissues should be thoroughly washed with alcohol.
Azure eosin
- For gastro-intestinal tract specimens and fixation of endocrine tissues
- Less lysis than Bouin’s
Hollande’s Solution
- Improve upon aging
- Preservation of glycogen and carbohydrates
- It produces minimal distortion of micro-anatomical structures and can be used for general and special stains.
Gendre’s Solution
Gendre’s Solution is the preferred fixative for tissues to be stained by ________ for collagen, elastic or connective tissue. (If tissue is fixed in formalin, a
pre-treatment in Bouin’s solution (as mordant prior to trichrome stain) is recommended
Masson’s trichrome
T/F: Gendre’s Solution requires washing out.
False (does not require)
Disadvantages of Gendre’s Solution
- It is not suitable for fixing kidney structures, lipid and mucus.
- It destroys cytoplasmic structures, e.g., mitochondria
- It produces RBC hemolysis and removes demonstrable ferric iron from blood pigments.
- It reduces or abolishes Feulgen reaction due to hydrolysis of nucleoproteins.
Disadvantages of Gendre’s Solution
- It is not suitable for fixing kidney structures, lipid and mucus.
- It destroys cytoplasmic structures, e.g., mitochondria
- It produces RBC hemolysis and removes demonstrable ferric iron from blood pigments.
- It reduces or abolishes Feulgen reaction due to hydrolysis of nucleoproteins.
It is better and less “messy” than Bouin’s solution and is an excellent fixative for glycogen.
Brasil’s Alcoholic Picroformol Fixative
Acetic acid is not used alone for fixation but is incorporated into other fixatives to form a compound solution, most commonly at a concentration of
approximately ____%.
5
- It fixes and precipitates nucleoproteins.
- It precipitates chromosomes and chromatin materials; hence, is very useful in the study of nuclear components of the cell. In fact, it is an essential constituent of most compound nuclear fixatives.
- It causes tissues (especially those containing collagen) to swell. This property is used in certain compound fixatives to counteract the shrinkage produced by other components (e.g. mercury)
GLACIAL ACETIC ACID
T/F: When Glacial acetic acid is combined with Potassium Dichromate, the lipid-fixing property of the latter is destroyed (e.g. Zenker’s fluid)
True
- It is recommended for acid mucopolysaccharides
- It fixes connective tissue mucin.
- It takes up CO2 to form insoluble lead carbonate especially on prolonged standing.
LEAD FIXATIVES
- Also used as a decalcifier and fixative in microscopy
- Sometimes incorporated into compound fixatives
- It is a poor penetrating agent, hence, is suitable only for small pieces of tissues or bones.
TRICHLOROACETIC ACID
Advantages of Trichloroacetic acid
- It precipitates proteins
- Its marked swelling effect on tissues serves to
counteract shrinkage produced by other fixatives. - It may be used as a weak decalcifying agent.
- Its softening effect on dense fibrous tissues facilitates preparation of such sections.
Acetone is not recommended as morphological fixative for tissue blocks, mainly because of its shrinkage and poor preservation effects. Its use is reserved for the fixation of cryostat sections or for tissues in which enzymes have to be preserved.
a. TRUE/FALSE
b. FALSE/TRUE
c. BOTH TRUE
d. BOTH FALSE
c. BOTH TRUE
- It is recommended for the study of water diffusible enzymes especially phosphatases and lipases
- It is used in fixing brain tissues for diagnosis of rabies.
- It is used as a solvent for certain metallic salts to be used in freeze substitution techniques for tissue blocks.
ACETONE (0-4 deg C)
Disadvantages of Acetone
- It produces inevitable shrinkage and distortion.
- It dissolves fat.
- It preserves glycogen poorly.
- It evaporates rapidly.
Provides a stable medium for transport of fresh unfixed tissues, such as renal, skin and oral mucosa biopsies, which will undergo subsequent frozen section and immunofluorescence studies
MICHEL’S SOLUTION
