LAB|midterm Flashcards
Primary aim of fixation
Primary aim: preserve the morphological and chemical integrity of the cell in as life-like manner.
Secondary goal of fixation
harden and protect the tissue from the trauma of further handling
fixed to structural proteins and thus rendered insoluble
Stabilizing proteins
fixative becomes part of the tissue
Additive fixation
fixative does not incorporate
Non-additive fixation
Duration of fixation of buffered formalin
24 h
Hydrogen Ion Concentration
pH 6 and 8
Fixative According to composition
i. Simple Fixative
ii. Compound Fixatives
types of Metallic Fixatives
- Mercuric Chloride
- Chromate Fixatives
- Lead Fixatives
- Heat
made up of only one component substance.
Simple Fixative
made up of two or more fixatives
Compound Fixative
permits the general microscopic study of tissue structures
Microanatomical Fixatives
preserve the specific parts and particular microscopic elements of the cell itself
Cytological
preserve nuclear structures
Nuclear Fixative
preserves cytoplasmic
Cytological Fixatives
preserve chemical contents of cells and tissues
Histochemical Fixatives
Use mercuric chloride and potassium dichromate
LIPID FIXATION
fixation for phospholipids
Baker’s formol calcium
CARBOHYDRATE FIXATION
Alcoholic formaldehyde
PROTEIN FIXATION
Neutral buffered formol saline or formaldehyde
GLYCOGEN FIXATION
Rossman’s fluid or absolute alcohol
widely used ALDEHYDE FIXATIVES
Formaldehyde
white precipitation
paraformaldehyde
Removal of precipitate is addition of 10% methanol
Formaldehyde
- preserves enzymes and proteins
- fixation of CNS Tissues and General post-mortem tissues
10% Formol-Saline
- preservation of surgical, post-mortem and research specimens
- best fixative for iron-containing tissues
10% Neutral Buffered Formalin/Phosphate-Buffered Formalin
preserves human brain, pH 7
10% Neutral Buffered Formalin/Phosphate-Buffered Formalin
- routine post-mortem tissues
- excellent in silver reticulum methods
- fixes lipids, especially neutral fats and phospholipids
Formol-Corrosive (Formol Sublimate)
- immunoperoxidase studies on tissues
- used for rapid diagnosis
- good for preservation of glycogen and for micro- incineration
-used to fix sputum, since it coagulate mucus
Alcoholic Formalin (Gendre’s Fixative)
- two formaldehyde residues linked by 3C chains
- used for enzyme histochemistry and electron microscopy
- preserves plasma proteins
Glutaraldehyde
- most common metallic fixative
- Tissues fixed with mixtures containing mercuric chloride (except Susa) contain black precipitates of mercury.
- Routine fixative of choice for preservation of cell detail in tissue photography.
MERCURIC CHLORIDE
- Renal tissues, Fibrin, Connective tissues and muscles
- Black deposits may be removed by adding saturated iodine solution in 96% alcohol, the iodine being decolorized with absolute alcohol in the subsequent stages of dehydration.
MERCURIC CHLORIDE