PROTEIN HISTOCHEMISTRY IN THE SKIN OF A FRESH-WATER CATFISH HETEROPNEUSTES FOSSILIS (BLOCH) (HETEROPNEUSTIDAE, PISCES)

Abstract

The localization and characterization of proteins and nucleic acids in the various cellular constituents of the skin of Heteropneustes fossilis have been described using several histochemical techniques.The basal cells give weak reactions for protein bound NH2 groups, basic nucleoproteins and tyrosine. The contents of the giant cells are proteineous in nature and give moderate reaction for protein bound NH2 groups, basic proteins, tyrosine and mucoprotein. The perinuclear areas of the giant cells, however, remain almost unstained. The mucous cells remain almost unstained with the various tests employed for proteins. The polygonal cells in the middle and outermost layer give positive reactions for protein bound NH2 groups, basic proteins, basic nucleoproteins, arginine, tyrosine and nucleoprotein. These cells even in the most superficial layer fail to give positive reactions for cysteine bound sulphydrly groups (-SH), disulphide bonds of cystine and Papanicolaou's stain for keratin indicating the non keratinized nature of the epidermis.In addition to the basal layer, the lymphocytes have also been observed in the middle layer and the outermost layer. This has been correlated to increase the efficiency in the local defence mechanism of the fish.A thin layer of compactly arranged elastic fibres at the inner margin of the dermis has been correlated to provide elasticity to the skin, thus facilitating the easy movements of the fish at acute angle.