Histology Reagents
Reagents in histology are used with different purposes. Some reagents are designed to preserve tissue by a process called fixation which is the most important procedure for the processing of biopsy tissue. Some others are use for toning and others for clearing the tissue or to take traces of mercury from already fixed tissue.
Fixatives are histology reagents use to preserve tissue from degradation and to maintain the cell structure. One of the most popular fixative in histology is 10% neutral formalin for light microscopes. There are many others that have increased in popularity like: Davidson's for the fixation of the eyes. Other versions have emerged from Davidson's: Modified Davidson's I and II have became popular in the histology world due to the gentle fix of the tissue in 24 hours.
Bouin's Fluid is another well known fixative use for histology. Carnoy's fluids now can be used without chloroform, avoiding the health hazards of chloroform. B-5 Fixative is widely used as a fixative of hematopoietic and lymphoreticular tissues, now with the great advantage of mercury-free B-5 Substitute. This avoids not only the health hazard but the mercury pigment after fixation.
Acetic Acid, 0.5% up to 10% is used for clearing or differentiation of the tissue after staining; also, Acid Alcohol is used for Clearing. Gold Chloride, 0.1% up to 5% is use for toning. Other reagents can be use to promote a reaction like: an oxidation reaction in those categories which have Potassium Permanganate 0.25% up to 3%. Periodic Acid 0.5% up to 5% reacts with Schiff's reagent to oxidize formaldehyde producing a magenta color for the demonstration of glycogen.