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R Vishwanath

Publications and source records attributed to R Vishwanath.

22 records · Page 2Linked to original sources
PubMed1990

Electron microscopic observations on the effect of gossypol on rat cauda epididymis.

Gossypol administered orally to male rats at a daily dose of 20 mg/kg body weight for 63 days caused hypertrophy of the cauda epididymal epithelium, with more than fourfold increase in height of the cells. The principal cells lost most of their microvilli and formed apical blebs which appeared to produce the dense secretory material which was found in the lumen. Less dramatic but similar changes also occurred after 9 days on the same regimen, with the height of the epithelium doubling. However after 19 days on this regimen, with the height of the epithelium doubling. However after 19 days on this regimen, the epithelium looked fairly normal apart from a maintained hypertrophy. As reported in other studies, the cauda epididymal sperm were severely damaged and immotile; many were decapitated and the oxygen uptake was low. Ultrastructural defects were abnormal or absent mitochondria, absence of plasma membranes and axonemal components and accessory fibres.

Animals↗
PubMed1988

Studies of the mechanism of action of gossypol as a male antifertility agent.

Gossypol administered orally to male rats at a daily dose of 20 mg/kg body weight for 62 days caused infertility. There were changes in the epididymal epithelium and the sperm were severely damaged and immotile. The sperm head was often detached; other defects were abnormal mitochondria, absence of plasma membranes and axonemal and accessory fibres and a lower oxygen uptake. To study the effect of gossypol on the motor apparatus of sperm, ram sperm were demembranated with the detergent, Triton-X-100. Such sperm models can normally be reactivated with ATP but gossypol (2.5-12.5 microM) decreased reactivation and must have a direct effect on the axoneme. Gossypol also inhibited ram sperm adenyl cyclase which is essential for maintaining high levels of cAMP in sperm and, in turn, motility. Ram sperm adenyl cyclase required Mn2+ for activity and high Mn2+ concentrations protected the enzyme from gossypol inhibition. Electron spin resonance studies proved that gossypol chelated Mn2+ with the formation of a 2:1 complex.

Adenosine Triphosphate↗
PubMedDate not supplied

Effects of cryopreservation on bull sperm head morphometry.

Artificial insemination using cryopreserved semen is a common management tool of the contemporary livestock producer. However, cryopreservation is detrimental to sperm function and fertility, killing some 50% of the spermatozoa during the process. Prediction of cryopreservation damage from prefreeze samples remains elusive. Computer-automated sperm head morphometry was used in this study to determine the effects of cryopreservation on bovine sperm head morphometry. Semen was collected from 18 bulls and was divided. One portion was extended to 200 x 10(6) sperm/ml and a microscope slide was prepared, while the remaining portion was cryopreserved in a Triscitrate-yolk extender. After thawing, the cryopreserved samples were prepared on microscope slides. All slides were air dried and were stained with hematoxylin and rose bengal. The morphometric dimensions for length, width, width/length, area, and perimeter for a minimum of 200 sperm heads were analyzed from each slide by computer-aided sperm head morphometry analysis, and the mean measurements were recorded. Bull sperm heads were significantly (P < 0.01) smaller in cryopreserved spermatozoa than in the companion extended samples for length (8.56+/-0.07 vs. 8.63+/-0.08 microm), width (4.39+/-0.05 vs. 4.48+/-0.05 microm), area (28.42+/-0.07 vs. 29.14+/-0.08 microm), and perimeter (23.33+/-0.21 vs. 23.70+/-0.23 microm) for all bulls. Width/length was also different (0.513 vs. 0.519). In addition, differences (P < 0.05) were found within 14 of 18 bulls for at least four of the morphometric parameters. The percent change in measures after cryopreservation were correlated (P < or = 0.05) to the variability of the extended sample. Variations in sperm head measurements were lower (P < or = 0.05) in extended samples of the four bulls in which no changes occurred than in extended samples of the remaining 14 bulls. These data suggest that the variability in sperm head measurements of individual bulls, or ejaculates, may be an indicator of sperm cryosurvivability.

Animals↗