Histochemical analysis of glycoproteins in the unicellular glands in the epidermis of an Indian freshwater fish Mastacembelus pancalus (Hamilton)

Abstract

The unicellular glands in the epidermis of the Indian freshwater fish Mastacembelus pancalus consist of three types of mucous cells and sacciform cells. The histochemical properties of their secretory glycoproteins have been analysed by means of a battery of histochemical methods. These included methods for the identification and simultaneous visualization 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 included (i) GPs with O-sulphate esters and oxidizable vicinal diols, (ii) GPs with oxidizable vicinal diols and sialic acid residues with or without O-acyl substitution at C7, (iii) GPs mainly with O-sulphate esters, 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 sialic acid residues without O-acyl substitution or with O-acyl substitution at C7, and (iv) GPs with traces of oxidizable vicinal diols, O-acyl sugars and sialic acid residues with O-acyl substitution at C8 (or which are di- or tri-substituted) or C9. The physiological significances of these GP classes and their release on the surface of the epidermis are discussed with special reference to their role in lubrication, protection and inhibition of the invasion and proliferation of pathogenic microorganisms in the epidermis, as adapted to the peculiar mode of life of the fish.

Response of mucous cells of the gills of traíra (Hoplias malabaricus) and jeju (Hoplerythrinus unitaeniatus) (Teleostei: Erythrinidae) to hypo- and hyper-osmotic ion stress

“…Neutral glycoproteins have low viscosity and may protect and lubricate gill epithelium against the physical injuries while the acidic and sulphated acid glycoproteins provide high viscosity and may help the adhesion of particles in suspension in water (Sibbing & Uribe, 1985) or prevent the proliferation of potentially pathogenic microorganisms in the epithelial surface (Mittal et al, 1994b). In the case of air-breathing fish, sulphated glycoproteins are also related to the protection against desiccation during emersion to take the atmospheric air (Mittal et al, 1994a;Parashar & Banerjee, 1999a, b;Chandra & Banerjee, 2003.The transference of the erythrinids, H. unitaeniatus and H. malabaricus, to deionized water (absence of ions) or water with high ion concentration resulted in changes of the chemical characteristics of glycoproteins produced by the MC.…”

Glycoconjugates in the branchial mucous cells of <i>Cynoscion guatucupa</i> (Cuvier, 1830) (Pisces: Sciaenidae)

“…It has been proposed that sialic acids cause GC molecules to extend because of their negative charge and that they also play a role in hydrating the immediate environment ( Mittal et al, 1994).…”

“…Likewise, in the fresh-water fish Odontesthes bonariensis (Díaz et al, 2004b), sulphated GCs predominate in their gills. It has been postulated that sulphated GCs deter the proliferation of pathogenic micro-organisms in fresh-water fish which are more likely to become infected in this type of environment (Whitear and Mittal, 1984;Mittal et al, 1994).…”

“…In vertebrates, mucus glycoconjugates take part in lubrication, controlling infections and preventing dehydration (Mittal et al, 1994). The mucus may act as an important diffusion barrier allowing ion absorption without direct contact between sea water and the epithelial cells (Shephard, 1982).…”

“…Several studies have been carried out on the mucous cells of fish skin. These studies describe the morphology of the different mucous cell types and characterize the glycoconjugates with diverse histochemical techniques, including lectin histochemistry (Genten and Danguy, 1990;Agrawal and Mittal, 1992;Mittal et al, 1994Mittal et al, , 1995Fishelson, 1996).…”