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Prof. Neeta Sehgal
Professor, Department of Zoology, University of Delhi
Our Fish Biology Unit is recognized as a major centre of research on fish physiology and allied areas. Working on several aspects of reproductive physiology of freshwater fishes using murrel and catfish as models. Our studies have established that estrogens regulate the synthesis of vitellogenin and choriogenin in the liver. There is a differential expression of Vg (A and B) genes on exposure of murrel to estrogenic compounds. We have shown existence of three vg genes (vga, vgb and vgc) in the murrel which transcribe and translate three vitellogenins.
To gain a further insight into the hormonal control of the synthesis of these two proteins, we have developed and standardized enzymatic and non-enzymatic techniques for isolation of viable hepatocytes and their short-term culture. These techniques have enabled us to investigate cell metabolism and biosynthetic activities in the liver cells. The techniques have also been employed to study the interaction between estrogens and several non-estrogenic hormones during vitellogenesis.
We have also initiated studies on the effects of xenoestrogens on the hepatic synthesis of vitellogenin and choriogenin in Indian freshwater fishes. We have developed and validated highly specific enzyme-linked immunosorbent assays for detection of extremely small amounts of vitellogenin and choriogenin in the blood of fishes. These homologous ELISAs can be used as biomarkers for pollutants in the aquatic environment. We have designed a protocol to quantify expression of these proteins at transcription level. In addition, other genes viz. heat shock protein and estrogen receptor, associated with the synthesis of vitellogenin have been investigated.
We have shown that H2O2 plays a significant role during spermatogenesis and have proposed a model for regulation of spermatogenesis at the intracellular level. Similar studies have been extended to investigate the phenomenon of oxidative stress during gametogenesis in the catfish.