After diastase digestion, what happens to glycogen staining in the tissue?

• A. Glycogen staining increases
• B. Glycogen staining decreases or disappears
• C. Glycogen staining remains unchanged
• D. Glycogen staining changes color to blue

Answer: (B)

Diastase digestion uses alpha-amylase to break down glycogen, a glucose polymer stored in cells. When tissue is treated with diastase before the PAS stain, the glycogen is hydrolyzed into soluble sugars and washed away, so the PAS-positive glycogen signal is lost. As a result, glycogen staining decreases or disappears after diastase digestion. This technique helps distinguish glycogen from other PAS-positive substances that diastase does not affect, which may still stain.