In PAS staining with diastase digestion (PAS-D), how does glycogen staining appear on sections labeled without diastase compared to sections labeled with diastase?

• A. Glycogen stains bright rose red on sections labeled without diastase and is absent on sections labeled with diastase
• B. Glycogen stains blue on sections labeled without diastase and remains blue after diastase
• C. Glycogen stains brown on both sections
• D. Glycogen stains bright rose red on both sections

Answer: (A)

Glycogen is a PAS-positive carbohydrate, so it stains bright rose/magenta when tissue is stained without diastase. When sections are treated with diastase before PAS staining (PAS-D), glycogen is digested, and the PAS color for glycogen disappears. So glycogen appears as bright rose red without diastase and is absent after diastase treatment. The other options don’t fit because they describe colors or persistence that aren’t consistent with glycogen being digested by diastase.