HISTOCHEMICAL ANALYSIS OF GLYCOPROTEINS IN THE UNICELLULAR GLANDS IN THE EPIDERMIS OF AN INDIAN FRESH-WATER FISH MASTACEMBELUS-PANCALUS (HAMILTON)

The unicellular glands in the epidermis of the Indian freshwater fish Mastacembelus pancalus consist of three types of mucous cells and sacc iform cells. The histochemical properties of their secretory glycoprot eins have been analysed by means of a battery of histochemical methods . These included methods for the identification and simultaneous visua lization of oxidizable vicinal diols, O-acyl sugars, O-sulphate esters and sialic acid residues with or without side-chain O-acyl variants. Four general classes of glycoproteins (GPs) were identified. These inc luded (i) CPs with O-sulphate esters and oxidizable vicinal diols, (ii ) GPs with oxidizable vicinal diols and sialic acid residues with or w ithout O-acyl substitution at C7, (iii) GPs mainly with O-sulphate est ers, low moieties of GPs with oxidizable vicinal diols, O-acyl sugars and sialic acid residues with side-chain O-acyl variant predominantly at C8 (or which are di- or tri-substituted) or C9 and in traces of sia lic acid residues without O-acyl substitution or with O-acyl substitut ion at C7, and (iv) GPs with traces of oxidizable vicinal diols, O-acy l sugars and sialic acid residues with O-acyl substitution at C8 (or w hich are di- or tri-substituted) or C9. The physiological significance s of these GP classes and their release on the surface of the epidermi s are discussed with special reference to their role in lubrication, p rotection and inhibition of the invasion and proliferation of pathogen ic microorganisms in the epidermis, as adapted to the peculiar mode of life of the fish.