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Research Techniques I (Biology 513)

Staining

+Staining

Why stain tissue?

Most tissues are colorless and unless one uses diffraction interference contrast microscopy, one cannot view the tissue easily

+Staining

+Types of biological stains

1) Natural dyes

- hematoxylin (from longwood trees)

- stains nuclei blue/purple

2) Mordants

- metallic salts (iron, aluminium, copper) mixed with a dye to enhance staining

- e.g. iron-hematoxylin stains nuclei and myelin

3) Synthetic dyes

- eosin (stains cytoplasmic elements pink/red)

+Specialized stains

Zoological tissue: Masson’s trichrome

Even though it has tri- in its name, it contains 4 dyes

Hematoxylin, scarlet-acid fuchsin, phosphomolybdic-phosphotungstic acid, aniline blue

Nuclei stain black, cytoplasm, keratin, muscle fibers stain red, collagen and mucus stain blue or light green

+Staining procedure

+Staining procedure

4. Counterstain – background material 

5. Dehydrate in ascending strengths of alcohol (removal of all water) prepare to coverslip slide

6. Clear (xylene, toluene, histoclear)

7. Cover with mounting medium (Cytoseal 60, Permount) and coverslip clearing agent dissolves mounting medium ensuring an even

coating of medium

+Cover slipping procedure