Staining

Staining

Tissues & cells are colorless. So, must be stained for examination >> Stains are

 either acidic or basic >> The classic stain used is Hematoxylin + Eosin [H & E] >> Hematoxylin is a basic stain [Stains acidic components like DNA of nucleus] [The affinity of acidic structures to basic stains is called basophilia] >> Eosin is an acidic stain [Stains basic components like proteins, mitochondria, collagen,…] [The affinity of basic structures to acidic stains is called acidophilia]

Some Special Stains for L.M

Vital stain: Staining a living structure inside a living animal 

 Ex.: Staining of phagocytic cells using trypan blue or India ink >> Supravital stain: Staining a living cell outside a living person

 Ex.: Brilliant cresyl blue → Stains reticulocytes (immature RBCs) in a blood film. >> Metachromatic stain: The stain gives a different color from the original one due to chemical combination between the stain & certain structures within the cell [Metachromasia]

 Ex.: Toluidine blue stains granules within mast cell with a violet color. >> Histochemical stains: Using enzyme reaction to demonstrate an enzyme or chemical components of the cell

 Ex.: -Alcian blue: used to detect mucin protein in mucous secreting cells -Acid phosphatase enzymes: used to detect enzymes of lysosomes -Periodic Acid-Schiff reaction [PAS]: used to detect polysaccharides in cell membranes >> Immunohistochemical stain: Based on specific reactions between antigen + antibodies labeled with fluorescent dye to emit visible light [Immunofluorescent technique]