Before PAS staining, which carbohydrate is digested by diastase, leading to a negative result for glycogen?

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Multiple Choice

Before PAS staining, which carbohydrate is digested by diastase, leading to a negative result for glycogen?

Explanation:
Diastase digestion in PAS testing is used to remove glycogen from tissue sections. Diastase hydrolyzes glycogen’s alpha-1,4 glycosidic bonds, breaking it down so it no longer yields a positive PAS reaction. This creates a negative result for glycogen after diastase treatment, which is why diastase-PAS helps distinguish glycogen from other PAS-positive substances like mucins. Neutral and acid mucins are not digested by diastase, so their presence won’t be eliminated by this step. So, the carbohydrate digested by diastase, leading to a negative PAS for glycogen, is glycogen.

Diastase digestion in PAS testing is used to remove glycogen from tissue sections. Diastase hydrolyzes glycogen’s alpha-1,4 glycosidic bonds, breaking it down so it no longer yields a positive PAS reaction. This creates a negative result for glycogen after diastase treatment, which is why diastase-PAS helps distinguish glycogen from other PAS-positive substances like mucins. Neutral and acid mucins are not digested by diastase, so their presence won’t be eliminated by this step. So, the carbohydrate digested by diastase, leading to a negative PAS for glycogen, is glycogen.

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