Staining theory Flashcards
Staining
visual labeling of an area of a tissue
Chromophore
portion iof a dye molecule responsible for COLOUR
alternating double and triple bonds
Chromogen
compound containing a choromophore
auxochrome
attaces a chromogen to an area of interest
anions or cations form salts
Anionic auxochromes
carboxyl (-COOH)
hydroxyl (-OH)
sulphonic (-SO3H)
Cationic auxochrome
Amine (-NH2)
Theory behind anionic auxochrome
Bind to positively charged tissue components
Amino groups, basic amino acids
theory behind cationc auxochromes
bind negatively charged tissue components
phosphate groups (nucleus), sulfate groups (mucin, cartilage)
Why are dyes used at a low pH?
Ionization and binding sites
auxochromes will be charged - bind to cationic dyes
(4) methods of staining
- ionic
- size of molecule
- fixation
- van der Waals forces
mordant
metal that binds dye to substrate
tissue elements stain a different colour that the staining solution
metachromasia
property of the tissue
what makes regressive staining different from progressive staining?
Differentiation/decolourization of excess dye
physical staining
selective solubility
porosity
tissue components are demonstated by a chemical reaction creating a coloured product
true histochemical
Progressive staining
stain to desired intensity, stop stain
regressive stain
tissue is overstained then differentiated until desired effect
polychromasia
staining solution with different dye molecules
Staining property
Argentaffin
Silver impregnation method - capable of reducing silver to its metallic form in solution
Argyrophile
Silver impregnation method - not capable of reucing silver, requires an external reducing agent for visualization
