Umesh C. Goswami

Role of ureogenesis in the mud-dwelled Singhi catfish (Heteropneustes fossilis) under condition of water shortage

The air-breathing Singhi catfish Heteropneustes fossilis was kept inside moist peat for 1 month mimicking their normal habitat in summer and the role of ureogenesis for their survival in a water-restricted condition was studied. The ammonia excretion rate by the mud-dwelled fish increased transiently between 6 and 12 h of re-immersion in water to approximately between eight and 10-fold, followed by a sharp decrease almost to the normal level at the later part of re-immersion. The urea-N excretion by the mud-dwelled fish increased to approximately 11-fold within 0-3 h of re-immersion, followed by a gradual decrease from 9 h onwards. The rate of urea-N excretion by the mud-dwelled fish, however, remained significantly higher (approx. threefold more) than the control fish even after 36-48 h of re-immersion. Although there was a significant increase of both ammonia and urea levels in the plasma and other tissues (except ammonia in the brain), the level of accumulation of urea was higher than ammonia in the mud-dwelled fish as indicated by the decrease in the ratio of ammonia: urea level in different tissues including the plasma. The activities (units/g tissue and /mg protein) of glutamine synthetase and three enzymes of the urea cycle, carbamyl phosphate synthetase, argininosuccinate synthetase and argininosuccinate lyase increased significantly in most of the tissues (except the brain) of the mud-dwelled fish as compared to the control fish. Higher accumulation of ammonia in vivo in the mud-dwelled Singhi catfish is suggested to be one of the major factors contributing to stimulation of ureogenesis. Due to this physiological adaptive strategy of ureogenesis, possibly along with other physiological adaptation(s), this air-breathing amphibious Singhi catfish is able to survive inside the moist peat for months in a water-restricted condition.

Metabolism of cryptoxanthin in freshwater fish

In search of other provitamins A, the metabolism of cryptoxanthin was studied in several species of freshwater fish, i.e. Channa gachua, Labeo boga (retinol-rich) and Heteropneustes fossilis (dehydroretinol-rich). The fish were either allowed to starve for 20-25 d to make their intestines free from carotenoids and vitamin A or kept on a vitamin-A-deficient diet for 140-150 d to deplete the initial reserve of vitamin A in the livers. Retinol-rich freshwater fish such as C. gachua and L. boga converted cryptoxanthin into retinol and no 3-dehydroretinol or 3-hydroxyretinol could be isolated from those fish that received cryptoxanthin. 3-Hydroxyretinol and 3-dehydroretinol were isolated from the vitamin-A-deficient H. fossilis, a 3-dehydroretinol-rich freshwater siluroid, after the administration of cryptoxanthin.

Efficiency of a few retinoids and carotenoids in vivo in controlling benzo[ a ]pyrene-induced forestomach tumour in female Swiss mice

The anticarcinogenic effect of vitamin A2 (dehydroretinol and 3-hydroxyretinol) compounds was studied and compared with that of vitamin A1 (retinoic acid, retinol and retinal) and carotenoids (lutein and beta-carotene) in the benzo[a]pyrene (B(a)P)-induced forestomach tumour model of female Swiss mice in vivo. Tumour growth and gross tumour incidence observed after the administration of B(a)P (eight doses of 1 mg, twice weekly for 4 weeks) and retinoids/carotenoids (2.5 and 4.7 microm per animal per d, 2 weeks before, during and 2 weeks after B(a)P) showed that the groups supplemented with lutein and 3-hydroxyretinol produced the best results in inhibiting tumour growth and had low tumour incidence compared with the control group given B(a)P only (P<0.05). Weights recorded after the different treatments showed that the beta-carotene-supplemented group exhibited maximum weight gain, followed by retinal, retinol, retinoic acid, lutein, dehydroretinol and 3-hydroxyretinol. These results indicate that the anticarcinogenicity of the compounds is not related to the vitamin A biopotencies. Vitamin A2 compounds having half the biopotency of the vitamin A1 compounds were seen to be anticarcinogenic. Again, among the carotenoids, lutein, having 50 % less biopotency, showed more significant results than beta-carotene. Thus it is imperative to conclude that the low animal growth achieved with these compounds has a correlation with the highest suppression of tumour occurrence in the present experiment. Therefore, the daily consumption of foods having high content of lutein and vitamin A2 should be given due importance and weight in further studies.

Toxic effect of environmental acid-stress on the sperm of a hill-stream fish Devario aequipinnatus: a scanning electron microscopic evaluation.

Environmental stress due to acidic pH of water was found to be one of the major factors leading to toxic effects on the sperm of a hill‐stream fish Devario aequipinnatus of Meghalaya, India. The Scanning Electron Microscopy of the transverse section of testes of the fish collected from its natural habitat with acidic pH (5.6–6.0) showed that the sperms were clumped together and their tails were either absent or were of extremely small length. The acrosome and midpiece were also not well differentiated. When the fingerlings from the natural habitat were reared to maturity in aquarium with water from natural habitat after changing the pH to alkaline range (8.0–8.2), the clumping of the sperm was not observed. The sperm tail was found to be well‐developed along with well‐differentiated acrosome and midpiece. Since the only change in the water quality parameters of the experimental aquarium as compared to those of the natural habitat was the pH, it is evident that the abnormal features of the sperm observed in fish from natural habitat is mainly because of environmental acid stress. Microsc. Res. Tech., 2009.

Functioning of Lycopene in Mammalian System: A Review

Lycopene is an open chain ‘hydrocarbon carotenoid’ without provitamin A activity, which gives tomato, pink grape fruit, watermelon etc. their red colour. It is a powerful antioxidant that has been shown to neutralize free radicals, especially those derived from oxygen, thereby conferring protection against prostate cancer, breast cancer, atherosclerosis and associated coronary artery disease etc. It reduces (L.D.L) low-density lipoprotein oxidation and helps reduce cholesterol levels in the blood. In addition, preliminary research suggests that lycopene may reduce the risk of macular degenerative disease, serum lipid oxidation and cancer of the lung, bladder, cervix and skin.

Analysis of Gill Structure from a Fresh Water Fish ( Heteropneustes fossilis ) Exposed to Bleached Sulfite Pulp Mill Effluents

The present communication reports toxic effects of bleached sulfite pulp mill effluents in fish (Heteropneustes fossilis) gills, with optical, scanning electron, and transmission electron microscopy. The general adverse effects include dilation of the primary lamellar wall, curling of secondary lamellar terminals, displacement of epithelial cell layers, degeneration of secondary lamella, deposition of mucous, and severe congestion in the gill arch. The significant shortening of secondary lamellae, widening of lamellar tips, and significant decrease in the number of mitochondria in chloride cells as compared to controls are some specific effects of bleached sulfite pulp mill effluents. Scanning electron microscopy demonstrated tearing of tissues in gill lamellae and arches. Transmission electron microscopy revealed membrane distortion of mitochondria in chloride cells, loss of uniformity of microvilli in pavement cells, and abnormalities in nuclear shape in different cells of effluent-exposed fish gills. Toxicity of the bleached sulfite pulp mill effluents and its impact on fish are discussed in the light of existing literature. Further, the importance of microscopy in toxicological evaluation of environmental pollutants is emphasized in view of its specific application potential.

Role of Retinoids in Modulating the Molecular Actions of Environmental Carcinogens

It has been found that carcinogenic growths are associated with the occurrence of low-level retinoids. In the population suffering from malnutrition, vitamin A-deficiency or, as a whole, deficiency of retinoids has been encountered. This is liable to bring about the occurrence of epithelial carcinoma caused by several carcinogens. The experiments relating to the formation of DNA adduct with carcinogen like aflatoxin B1 (AFB1) catalysed by microsomal mono-oxygenase of liver could be controlled through a series of retinoid compounds such as vitamin A and carotenoids having pro or non-pro-vitamin A status. A brief review has been illustrated.