Fixation (Part 3) Flashcards
Used to preserve brain tissue for diagnosis of rabies
Acetone and Carnoy’s fluid
Must be used at ice cold temperature
Fixative and dehydrating agent for phosphatases and lipases
Acetone
Disadvantages of acetone
- Volatile (evaporates easily)
- Dissolves fat
Considered as the most rapid fixative
For fixing chromosomes and lymph glands
Carnoy’s fluid
Excellent for glycogen demonstration
Picric Acid Fixatives
Why is picric acid considered as versatile reagent?
- Can be used as decalcifying agent (because it is an acid)
- Can be used as a stain
- Can also be used as a fixative
Disadvantage of Picric Acid
Can impart a yellow color
A picric acid used to preserve embryos, pituitary biopsies & endometrial curettings but contraindicated for kidney structures
Bouin’s fluid
Bouin’s fluid is not compatible with what stain?
Feulgen’s stain
Used for touch preparations
95% Isopropyl Alcohol
Soldifies at 17degC
A nuclear fixative (contraindicated for cytoplasmic fixation)
Often used in combination with other fixatives to form a compound fixative
Glacial Acetic Acid
Used for mucopolysaccharides and nuclear protein
Newcomer’s fixative
Examples of Fixatives for Electron Microscopy (EM) (3)
- Osmium Tetroxide
- Glutaraldehyde
- Paraformaldehyde
Can be used for myelin and peripheral nerves (neurologic structures)
Disadvantage: Slow in Action
Osmium Tetroxide
- Method of fixation that uses chemical fixatives such as formalin, zenker’s, etc
- Immersing the specimen in the fixative
Chemical Fixation
The routine tissue fixative
10% formalin
Method of fixation that uses heat fixation, microwave technique etc.
Can be done in preparing frozen sections
Physical Fixation
- Fixation method that involves thermal coagulation of proteins
- Used in micro, in bacte to prepare bacterial smears
Heat fixation
Fixative volume in Museum preparations
50 to 100 time the volume of the specimen
Used to wash out excess amount of Mercuric fixaitves
Alcoholic Iodine
Used to wash out excess amount of picric acid fixatives
50-70% alcohol
Often used in conjunction with other fixatives to produce a compound fixative other than Glacial Acetic Acid
TCA (trichloro acetic acid
A weak and slow decalcifying agent
TCA
