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.
Periodic acid (0.5% aqueous specified).
Schiff's reagent (Coleman’s specified).
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)
6µ paraffin sections of neutral buffered formalin fixed tissue are suitable.
Other fixatives are likely to be satisfactory, although glutaraldehyde should be avoided.
- 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.
- Dehydrate with ethanol, clear with xylene and coverslip using a resinous medium.
- 1-2-glycols – red
- Nuclei – blue
- Background – green (if light green used)
- 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.
McManus, J. F. A., (1946)
Stain Technology, v23, p99.
Last updated January 2019