STAIN | DEFINITIONS | PREPARATION | USES

STAIN | DEFINITION | PREPARATION | USES

Staining means the use of dyes to render various tissue constituents variable and distinct from one another. Different parts of cells or tissue react differently to colours due to their chemical and or physical differences. Thus they become easily visible. The preparation, experimenting and uses of stains form a separate science in itself. 

The now widely accepted theory of staining is the view advanced by Witt (1876). The presence of colour in a chemical is by the presence of groups or radicals called chromophors. The material that contains these are called chromogens. The power of imparting this colour to other substances is given to a Christian by the presence of an automotive. Auxochrome are either acid or alkali radicals, which also are responsible for solubility of stains. 

There are many ways in which a colour may be caused to remain on a particular structure. 

1. The ionized stain becomes precipitated upon materials by surface adsorption. 
2. A definite chemical combination is entered into between dye and the tissue. 
3. The saturation of a material with a dye and the subsequent precipitation of the dye in place by the use of solvents for dehydrating in which the dye is not soluble.
4. The tissue is first caused differentially to absorb a substance with which the dye subsequently makes an insoluble compond. These substances are called mordants. 

Stains are classified into many based on varied principle.

The more important stains, their preparation and uses are given below.

• COTTON BLUE / CHINA BLUE / SPRIT BLUE

Both aqueous and alcoholic solution are used. 

Anilin blue (1gm)

Distilled water or 85% alcohol 100ml

This is excellent for filamentous algae and fungi. Stains the cell walls and achromatic figure used in combination with safranin.

• CRYSTAL VIOLET 

Crystal violet 1gm

Clove oil 100ml

This solution works well, since aqueous or alcoholic violets get washed away during dehydration. Nuclear stain. Stains customised and lignified cell walls. A good counter stain for safranin in anatomical sections. 

• CARMINE / ACETACARMINE

Boil 100ml of 45% acetic acid in a flask fitted with a reflux condensed. Add a small pinch of Carmine powder from a weighed out quantity of 2gm. Remove source of heat and add rest of the dye, dissolved in glacial acetic acid until the colour is wine reds. Store in a refrigerator. This stain is customarily used for cytological preparations. 

• FAST GREEN

Fast green (1gm)

Clove oil 75ml

Absolute alcohol 25ml 

Filter when sufficient time has been allowed for the stain to dissolve completely. The stain acts on non lignified tissues and on spindle fibres. Good conversation for safranin. Fresh stain is not be used. Does not fade.