McManus’ PAS Reaction
for 1-2 Glycols
The periodic acid Schiff reaction (PAS) is used to demonstrate the presence of 1-2-glycols, and is consequently an important method in the histochemistry of carbohydrates and the histological demonstration of many structures.
Materials
- Periodic acid (0.5% aqueous specified).
- Schiff’s reagent (Coleman’s specified).
- Harris’ hemalum
- Light green working solution (0.2% aqueous Light Green diluted 1:5 with distilled water)
- Ammonia water (water with 3 drops concentrated ammonia per 100 mL)
Tissue Sample
6 µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are likely to be satisfactory, although glutaraldehyde should be avoided.
Protocol
- Bring sections to distilled water via xylene and ethanol.
- Digest using a diastase, hyaluronidase, or sialidase procedure.
- Oxidize in Periodic Acid for 5 minutes.
- Rinse in distilled water.
- Place in Coleman’s or another Schiff’s Reagent for 15 minutes.
- Wash in running water for 10 minutes to develop the pink color.
- Counterstain with one of the following:–
- Harris’ hematoxylin for 6 minutes, then
- Wash in running water and transfer to 1% acid ethanol for 3-10 quick dips
- Transfer to 1% acid ethanol for 3-10 quick dips
- Wash in distilled water
- Dip in ammonia water to blue the sections
- Wash in running water for ten minutes
- Light green working solution for 10 seconds.
- Harris’ hematoxylin for 6 minutes, then
- Dehydrate with ethanol, clear with xylene, and coverslip using a resinous medium.
Expected Results
- 1-2-glycols – red
- Nuclei – blue
- Background – green (if light green used)
Notes
- Light Green is better used when delineation of fungi is required.
- Tap water and ammonia decolorize Light Green, so proceed directly to dehydration.
- Glutaraldehyde fixed tissues will have a non-specific positive background staining. This must be blocked before step 2.
Safety Note
Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.
References
- McManus, J. F. A., (1946)
Stain Technology, v23, p99.
