Stain used for glycogen -

Ans. is 'a' i.e., PASo PAS reaction is a technique for demonstration of glycogen in tissue sections, o PAS strands for Periodic acid schiff.o The purpose of the periodic acid is to oxidize some of the tissue carbohydrates. This produces aldehyde group which can then condense with schiffs reagent forming a megenta colouration, o The t/t with periodic acid oxidize only those carbohydrates which have 1-2 glycols in their structure.o Since all carbohydrates do not include this structure, the PAS is not a method for carbohydrates in general but only for those which contain 1-2 glycols or closely related structure.The following criteria must be presnt in tissue substance to give a PAS postive reaction -i) It must contain the 1-2 glycol grouping, an equivalent amino or alkylamino grouping, or the oxidation product CHOH-CO.ii) It must not diffuse away during fixationiii) It must given an oxidation product which does not diffuse away.iv) It must be present in sufficient concentration to produce a detectable final colour.Carbohydrates which usually stain with this method include -o Polysaccharideso Mucopolysaccharideso Glycoproteinso GlycolipidsP.A.S. staining is useful in all of the following -o Glycogeno Neutral mucosubstanceso Some epithelial sulfomucins and sialomucinso Basement membraneo Cerebrosideso Gangliosideso Cartilageo Kerasin (Gaucher's disease)