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Biomedical subjects

S K Sharma

Publications and source records attributed to S K Sharma.

At least 649 records · Page 36Linked to original sources
PubMed1977

Histopathological aberration in fish skeletal muscle during induced starvation.

Effects of induced starvation on the histology of the fish skeletal muscle, have been studied in the "red muscle" of Heteropneustes fossilis. The tissue has been studied at weekly intervals, for four weeks. The intrafibrillar as well as the interfibrillar nuclei exhibit different behaviour in the red and the white muscle fibre types. Loss of myofibrils, predominantly in the white fibres, is accompanied with an increase in the non-contractile extrafibrillar tissue.

Animals↗
PubMed1976

First record of a cyclopoid host-Mesocyclops leuckarti (Claus) for an acanthocephalous worm-Acanthosentis dattai Podder from Delhi (India).

Among seven species of Cyclops encountered in four water ponds kept under observation in Delhi during 1973-74 period, six specimens of Mesocyclops leuckarti (Claus, 1857) were found to harbour juvenile stages of Acanthosentis dattai Podder, 1938, parasite of the freshwater fish of the genus Barbus. This is the first record of members of Cyclopidae as intermediate hosts of Acanthocephala in India. The morphology of hitherto unknown juvenile stage of A. dattai is described in this note.

Acanthocephala↗
PubMed1975

Non-specific binding in the affinity chromatography of chymotrypsin.

The strong and specific binding of chymotrypsin on chromatographic columns containing agarose substituted with N-sigma-amino caproyl-D-tryptophan methyl ester is abolished when the sigma-amino groups on the surface of the enzyme are reacted with acetic anhydride. Because the catalytic properties of the acetylated chymotrypsin are identical to those of the underivatized enzyme, it is concluded that the high affinity of chymotrypsin for this column is not due solely to biospecific inhibitor binding, which is by itself very weak, but requires reinforcement through weak non-specific interactions with the column support. It is postulated that these non-specific interactions include electrostatic interactions between agarose matrix and positively charged lysyl residues on the enzyme. The results demonstrate for the first time that residues on the surface of an enzyme not associated with its active site can play an important role in some chromatographic systems previously thought to be based on purely biospecific interactions.

Acetylation↗
PubMed1975

Morphine receptors as regulators of adenylate cyclase activity.

Morphine inhibits adenylate cyclase (EC 4.6.1.1) activity of neuroblastoma times glioma hybrid cells. The inhibition is stereospecific and is reversed by the antagonist, naloxone. The relative affinities of narcotics for the opiate receptor agree well with their effectiveness as inhibitors of adenylate cyclase. Morphine-sensitive and -insensitive cell lines were found, and the degree of sensitivity was shown to be dependent upon the abundance of narcotic receptors. Thus, morphine receptors are functionally coupled to adenylate cyclase. A molecular mechanism for narcotic addiction and tolerance is proposed.

Adenylyl Cyclase Inhibitors↗
PubMed1975

Dual regulation of adenylate cyclase accounts for narcotic dependence and tolerance.

Narcotics affect adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] in two opposing ways, both mediated by the opiate receptor. The first process is the readily reversible inhibition of the enzyme by narcotics; the second is a compensatory increase in enzyme activity which is delayed in onset and relatively stable. Late positive regulation of the enzyme counteracts the inhibitory influence of morphine and is responsible for narcotic dependence and tolerance. The coupled inhibitory and positive regulatory mechanisms for adenylate cyclase provide a means of activating and deactivating neural circuits hours after the initial event and thus may play a role in a memory process.

Adenosine↗