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Biomedical subjects

K Ramasharma

Publications and source records attributed to K Ramasharma.

24 records · Page 2Linked to original sources
PubMed1981

Isolation and characterization of a bovine seminal plasma protein inhibiting pituitary FSH secretion.

A basic protein with inhibin-like activity was purified from bull seminal plasma by ethanol precipitation, ion-exchange chromatography, gel filtration and preparative disc electrophoresis. The protein migrated rapidly into the acrylamide gel at pH 4.5 but failed to penetrate the gel at pH 8.9. Electrophoresis at pH 4.5 revealed heterogeneity. Its molecular weight by SDS gel electrophoresis was estimated to be approx. 18 000 daltons. It exhibited inhibin activity in both in vivo and in vitro model systems. The partially purified protein fraction was active in suppressing hCG-induced mouse uterine weight in immature mice. It specifically inhibited the castration-induced rise in serum FSH in 34-day-old male rats, blocked the action of synthetic LH-RH in vivo and in vitro in rats and mice respectively.

Animals↗
PubMed1981

Binding of an inhibin-like protein from bull seminal plasma to ovine pituitary membranes.

A purified basic protein from bull seminal plasma having inhibin activity was labeled with 125I and tested for binding with ovine pituitary membrane fractions. The bound radioactivity could be eluted under acidic conditions and shown to rebind to fresh pituitary membranes. The properties of the eluted labeled inhibin were similar to the unlabeled fraction. The eluted labeled inhibin exhibited specific binding to the membranes, which was displaceable in a dose-dependent manner by an unlabeled active fraction. Only those fractions in the purification scheme which had inhibin activity also competed for the binding. A bovine follicular fluid fraction with molecular weight greater than 10 000 and inhibin activity also displaced the bound radioactivity from the membranes. Other purified hormones such as ovine FSH, LH or their subunits, prolactin or bovine serum albumin, dialyzed serum or unrelated basic macromolecules such as lysozyme, polylysine, histones, had no influence on the binding of labeled inhibin to ovine pituitary membranes. Synthetic LH-RH also failed to displace the labeled inhibin from the membranes. The binding was sensitive to heat and trypsin treatments. The data are consistent with the direct action of inhibin on the pituitary and demonstrate the existence of binding sites for the active fraction in this target.

Animals↗
PubMed1981

Effect of inhibin like factors on gonadotrophin release by the mouse pituitary in vitro.

The release of gonadotrophins by the mouse whole pituitary in vitro was investigated. Whole tissue from 34 day old male mice was highly responsive to synthetic LRH in short incubations at 37 degrees C. About 15% of FSH and 17% of LH were secreted during a 3 h pulse with 3 ng of LRH. Pre-exposure of the mouse pituitary to fractions containing inhibin activity, inhibited the FSH release induced by LRH. Inhibin from bovine and human seminal plasma and porcine follicular fluid preferentially inhibited FSH secretion, while LH secretion was also reduced by inhibin like factors from bovine follicular fluid and testicular extract. The inhibition of FSH and/or LH release was measured by specific radioreceptor assays and could not be due to destruction of either gonadotrophin or LRH. Purified bovine seminal plasma inhibin was effective at very low concentrations in vitro. The whole incubation system is simple and an estimation of inhibition of bioactive (binding activity) FSH release can be obtained within 24 h.

Animals↗