Staining Practical Flashcards
Describe the general technique of staining wax sections:
Remove wax (deparaffinize) using a solvent
Rehydrate to staining reagent
Allow dyes to transfer to a tissue section
Dehydrate
Mount tissue section in appropriate mounting media
Describe haematoxylin staining:
Alkaline based dye that stains acidic structures such as chromatin in DNA
Stains a deep blue/ purple colour
Will usually give a background stain to most of the tissue unless it is differentiated
Describe eosin staining:
Eosin is a counterstain that stains basic structures such as cytoplasm, connective tissue and eosinophils
Stains pink/ orange
Intensity of the stain may be improved by altering pH of eosin solution
Describe regressive staining:
Overstain in haematoxylin
Remove a quantity of haematoxylin stain with a differentiation step – usually a weak acid
Removes background staining
Useful for large batches of slides
Describe progressive staining:
Add haematoxylin in small incremental steps until a desired dye intensity met
Usually omits the differentiation stage
Background staining may occur
Difficult method to use for large batches of slides
What is differentiation ?
Differentiation in H&E staining refers to the controlled removal of excess or non-specific haematoxylin staining from tissue sections
This step enhances contrast and ensures that haematoxylin staining is confined to nuclear material, improving the definition of cellular structures
Successful = nuclei have good contrast
Over-differentiation = nuclei faded and poorly contrasted with cytoplasmic staining
Describe Periodic Acid Schiff (PAS):
Used for staining tissue
structures high in specific types of carbohydrate content (e.g. glycogen, proteoglycans, polysaccharides) found in
connective tissue, mucus and basement membrane
Used to stain kidney biopsies,
liver biopsies, certain glycogen
storage diseases and
suspected fungal infections
PAS +ve: Bright Red /Magenta
Describe Casons Trichrome:
Stain for muscle and collagen
One step method
Results:
- nuclei = red
- Erythrocytes = orange
- cytoplasm = red
- collagen = blue
