No abstract

Biochemically known mucopolysaccharides can rarely be identified unequivocally in specific tisse sites by histochemical methods. Moreover, many carbohydrate-rich substances that have been detected histochemically (in terms of their vic-glycol content and characteristic acid groups) cannot be related to mucopolysaccharides and glycoproteins known to biochemists. Accordingly, a terminology and classification is proposed for delineating mucosubstances in situ in terms of their histochemical properties. Mucosubstance and mucosaccharide are recommended as general terms for tissue entities rich in carbohydrate, but the term [acid] mucopolysaccharide is restricted to biochemically known mucopolysaccharides of connective tissue. The terms sulfomucin and sialomucin are suggested for acidic epithelial mucosubstances containing sulfate esters and sialic acid, respectively. Neutral mucosubstance is reserved for naming periodate-reactive entities, except glycogen, that lack demonstrable acid groups. The various muscosubstances that have been found in tissue sections so far are tabulated with suggested names.

Sialidase digestion of histological sections releases sialic acid from some sialic acid rich nonsulfated mucins. Such treatment eliminates the metachromatic staining and alcian blue affinity of these mucopolysaccharides. The procedure furnishes a method for histochemical localization of certain sialomucins.