Periodic acid-Schiff

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Periodic acid-Schiff (PAS) is a staining method used in histology and pathology. This method is primarily used to identify glycogen in tissues. The reaction of periodic acid selectively oxidizes the glucose residues, creates aldehydes that react with the Schiff reagent and creates a purple-magenta color. A suitable basic stain is often used as a counterstain.

PAS staining is mainly used for staining structures containing high proportion of carbohydrate macromolecules (glycogen, glycoprotein, proteoglycans), typically found in eg. connective tissues, mucus, and basal laminae.

PAS staining can be used to distinguish between different types of glycogen storage diseases.

J. F. A. McManus PAS Method For Glycogen

Fixation:

10% Buffered Neutral Formalin

Section:

Paraffin, @ 6 micrometres

Staining Procedure:

Digest using a diastase, hyaluronidase, or sialidase procedure

1. Deparaffinize and hydrate to distilled water

2. Oxidize in Periodic Acid, 0.5%, 5 minutes and rinse in distilled water

3. Stain in Coleman's Feulgen, or Schiff's Reagent, 15 minutes and wash in running water to develop the pink color, 10 minutes.

4. Counter stain in Haris Hematoxylin, 6 minutes, or Light Green working Solution, 10 seconds. Light Green is better used when delineation of fungi is required. Prepare the working solution by adding Light Green, 0.2% solution 1:5 with distilled water, proceed to step #7, dehydration. Tap water and ammonia decolorize Light Green.

5. Wash in running water and transfer to Acid Alcohol, 1%, for 3-10 quick dips. Wash again in distilled water.

6. Dip in dilute Ammonia Water, 0.3%, to blue the sections and again wash in running water for ten minutes.

7. Dehydrate in 95% alcohol and 100% alcohol, clear in Xylene, two changes each.

8. Mount.

Results:

Nuclei blue

Fungi red

Background when Light Green is used as the counter stain green, pale

References: McManus, JFA: Stain Tech, 23 99 (1946)

AFIP Manual of Histologic Staining Techniques; I. G. Luna 3rd ed. Ed. New York McGaw-Hill Publications. C 1968, p. 160.

Mowry, RW. Annals of the New York Academy of Science: 106: 402 (1963)