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Biomedical subjects

S D Sharma

Publications and source records attributed to S D Sharma.

192 records · Page 11Linked to original sources
PubMedDate not supplied

Stimulation of insulin secretion by peptides analogous to the C-terminal tetrapeptide amide of cholecystokinin.

Two tetrapeptides, Glp-Met-Asp-Phe-NH2 (I) and Pro-Met-Asp-Phe-NH2 (II), analogous to the C-terminal tetrapeptide amide of cholecystokinin (CCK-4) have been synthesized and their effect on the release of insulin from the isolated Langerhans islets of rat pancreas compared with that of synthetic CCK-4. Both the new congeners exhibited significant insulin-releasing activity at 10(-8) M and 10(-6) M concentrations, suggesting that the biological activity is retained when the N-terminal Trp residue of CCK-4 is replaced by Glp or Pro.

Animals↗
PubMedDate not supplied

Synthetic analogs of cholecystokinin terminal tetrapeptide that stimulate insulin but not glucagon release from pancreatic islets.

Two synthetic analogs of CCK-4, Glp-Met-Asp-Phe-NH2 (I) and Pro-Met-Asp-Phe-NH2 (II) reported earlier to stimulate insulin release from the isolated rat pancreatic islets in vitro at concentrations as low as 10(-10) M, have now been found to be totally ineffective as glucagon releasers at concentrations as high as 10(-6) M or higher. It is evident that the replacement of Trp in CCK-4 by Glp and Pro residues leads to peptides which exhibit insulin releasing activity without stimulating the release of glucagon.

Animals↗
PubMedDate not supplied

Multivalent melanotropic peptide and fluorescent macromolecular conjugates: new reagents for characterization of melanotropin receptors.

Radioreceptor binding studies have documented the presence of melanotropin receptors on some but not all of the various human melanoma cell lines that have been studied. Using a newly developed class of multivalent fluorescent melanotropin-macromolecular conjugates, we have demonstrated for the first time the presence of specific melanotropin receptors on all of the melanoma cell lines, both mouse and human, melanotic as well as amelanotic, that were investigated. The conjugates developed by us consisted of multiple copies of both a potent melanotropin analogue and a fluorophore, both arranged in a pendent fashion on a biologically inert macromolecule. While the multivalency of these conjugates may have established stronger binding with the melanotropin receptors on the cell surface (perhaps by establishing simultaneous multiple interactions), the presence of multiple copies of the fluorophore also greatly increased the level of detection in fluorescence labeling experiments. Membrane receptor-hormone-associated phenomena, such as capping and internalization of the receptor-ligand complex, also were observed. The details of these methods are described using B-16 mouse melanoma cells as a model system. The demonstration of MSH receptors as a common marker for melanoma suggests that this methodology might be employed for early clinical detection and anatomical localization of melanoma. These results also offer the possibility that substitution of the fluorophore in these conjugates by a chemical agent of (chemo-)therapeutic relevance may provide a powerful tool for site specific (tumor) targeting and cytotoxicity.

Amino Acid Sequence↗
PubMedDate not supplied

Lithium modulates mitogen induced natural killer activity and interferon production.

Incubation of human peripheral blood mononuclear cells with lithium ions in combination with either phytohemagglutinin or concanavalin A resulted in increased natural killer cell activity. Maximum augmentation was observed following three days of culturing peripheral blood mononuclear cells with mitogens and lithium and was accompanied by increased interferon production. Lithium did not enhance the natural killer cell activity of peripheral blood mononuclear cells cultured with Poly I:C.

Cyclic AMP↗