fixation Flashcards
fixatives that chemically alter the tissue by bonding and linking with it
additive fixatives
fixatives - predominantly organic compounds - that act on tissues without chemically combining with it
non-additive fixatives
fixatives that allow solutions to penetrate the interior of the tissues readily
coagulant fixatives
fixatives that act by creating gel barriers that make it more difficult for solutions to penetrate tissues
non-coagulant fixatives
placing an already fixed tissue in a second fixative to act as mordant
secondary fixation
form of secondary fixation in which a tissue is placed in 2.5-3% potassium dichromate for 24 hours for better staining effects
post-chromatization
process of removing excess fixative after fixation to improve staining and remove artifacts
washing out
effect of temperature on fixation
increase in temperature accelerates fixation (but increases rate of autolysis)
fixation time for brain specimens
2-3 weeks
ideal ratio of fixative to specimen volume
20:1 (or 10:1)
interval between interruption of blood supply and the time the tissue is immersed in a fixative
cold ischemia time
maximum allowable cold ischemia time
60 minutes
duration of fixation for electron microscopy
3 hours
pH required for satisfactory fixation
pH 6-8
types of fixatives according to composition
simple and compound fixatives
types of fixatives according to action
microanatomical and cytological fixatives
type of fixatives made up of only one component substance
simple fixatives
type of fixatives made up of two or more components to obtain optimal combined effect
compound fixatives
type of fixatives that permit the general microscopic study of tissues without altering its structural patterns
microanatomical fixatives
type of fixatives that preserve specific parts and particular microscopic elements of the cell itself
cytological fixatives
cytological fixative that contains glacial acetic acid and has a pH of 4.6 or less
nuclear fixatives
cytological fixative that should never contain glacial acetic acid and has a pH of more than 4.6
cytoplasmic fixatives
cytological fixative that preserve the chemical constituents of cells and tissues
histochemical fixatives
fixative that is both a nuclear and histochemical fixative
newcomer’s fluid
these fixatives are satisfactory for routine paraffin sections, electron mx and when histochemical and enzyme studies are indicated
aldehyde fixatives
fixative used for mailing specimen
formaldehyde (formalin)
used to remove brown or black ppts by the action of formic acid in formaldehyde with blood
saturated picric acid
best fixative for tissues containing iron pigments and elastic fibers
10% BNF
rapid fixative that is used to fix sputum because it coagulates mucus
Gendre’s fixative (alcoholic formalin)
fixative used to fix brain tissue for the diagnosis of rabies
Carnoy’s fluid
fixative recommended for chromosomes, lymph glands and urgent biopsies
Carnoy’s fluid
most rapid fixative; fixation time: 1-3 hours
Carnoy’s fluid
fixative recommended for mucopolysaccharides and nuclear proteins
Newcomer’s fluid
excellent microanatomical fixative for blood-containing organs
zenker’s-formol (Helly’s fluid)
fixative recommended mainly for tumor biopsies
Heidenhain’s Susa
fixative for the study of tissue necrosis and early degenerative processes
Orth’s fluid
fixative that demonstrates rickettsiae and other bacteria
Orth’s fluid
fixative recommended for fixation of embryos and pituitary biopsies
Bouin’s solution
expensive and slow-penetrating fixative for special application in neurohistology and neuropathy
osmium trioxide
fixative recommended for the study of water diffusible enzymes esp. phosphates and lipases
acetone
