• K Muralidhar

      Articles written in Journal of Biosciences

    • On the presence of sulphate in pituitary lutropin

      A S Arunasmithasri T Rajendrakumar K Muralidhar

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      The presence of sulphate in the carbohydrate of pituitary lutropin from different species has been investigated using a biosynthetic approach. Pituitaries from rats, rabbits, goats, and buffaloes were incubated in the presence of35SO4- and the35SO4- -labelled proteins in the tissue immunoprecipitated with a well characterized anti-sheep lutropin serum. The incorporation into immunoreactive lutropin was low in the case of rat, rabbit and goat pituitaries while, it was considerable in the case of buffalo pituitaries. Hence further characterization studies were carried out on35SO4- -labelled proteins of buffaloes. The physico-chemical, immunological and biological properties of radio-labelled buffalo pituitary material were shown to be similar to those of standard lutropin. Inin vitro conditions of incubations, most of the incorporation of35SO4- was observed into tissue lutropin while under similar conditions of incubation, [14C]-amino acids were found to get incorporated mostly into medium lutropin. The physiologically specific releasing hormone, lutropin-releasing hormone was found to stimulate the release of35SO4--labelled lutropin from the rabbit pituitaries into the medium. These results give indirect evidence that sulphate could be present in pituitary lutropin.

    • Purification and characterisation of prolactin from sheep and buffalo pituitaries

      K Muralidhar Neeraja Chadha Rita Kohli

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      A study of the problem of structural variants of proteins and their relative contribution to the expressed immunological and biological activity has been initiated using sheep and buffalo prolactins as models. The feasibility of obtaining immunologically and biologically active prolactin in high yields from the discarded ’acid pellet’ of sheep and buffalo pituitaries has been demonstrated. This permits use of the same batch of glands for purifying lutropin, follitropin and prolactin as side fractions. The major component in preparations of buffalo prolactin has a molecular size of 24 kDa. The preparations were active in a radioligand binding inhibition assay and in a rat liver based radioreceptor assay. Charge and size isomers of sheep prolactin and buffalo prolactin have been observed. The reference sheep prolactin did not, in preliminary work, give any indication of being glycosylated. However radioactive sulphate was found to be incorporated into prolactin-rich fractions of sheep and buffalo pituitariesin vitro. By physico-chemical and immunochemical criteria the [35S]-labelled material was similar to standard reference prolactin. The structural implications of sulphation have been probed.

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