Search PubMed⌕ Search

Biomedical subjects

R K Sharma

Publications and source records attributed to R K Sharma.

At least 469 records · Page 26Linked to original sources
PubMed1980

Differential interaction of rabbit skeletal muscle phosphorylase kinase isozymes with calmodulin.

Rabbit skeletal muscle contains two phosphorylase kinase isozymes arising from the two different muscle types, the white and the red muscle (Jennissen, H. P., and Heilmeyer, L. M. G. (1974) FEBS Lett. 42, 77-80). The two phosphorylase kinase isozymes could be separated by affinity chromatography on a calmodulin-Sepharose 4B column. In media containing high concentrations of Ca2+, about 2 mM, both isozymes were bound to the affinity column. When the column was eluted with a buffer containing 0.2 mM Ca2+, the red muscle isozyme was eluted, whereas white muscle isozyme was eluted from the column by an ethylene glycol bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid. The purified white muscle isozyme can be distinguished from the red muscle isozyme by its ability to inhibit calmodulin-dependent cyclic nucleotide phosphodiesterase. The two isozymes are also regulated differently by calmodulin. Both isozymes contain tightly bound calmodulin as a subunit (Cohen, P., Burchell, A., Foulkes, J. G., Cohen, P. T. W., Vanaman, T. C., and Nairn, A. C. (1978) FEBS Lett. 92, 287-293), which renders the enzyme sensitive to Ca2+. Only the white muscle isozyme can be activated by exogenous calmodulin.

Animals↗
PubMed1980

Endogenous substrate for cyclic AMP-dependent protein kinase in adrenocortical polyadenylated messenger ribonucleoproteins.

An endogenous polysomal cyclic AMP-dependent protein kinase specifically phosphorylates a 150,000-dalton peptide bound to an adrenocortical polyadenylated messenger ribonucleoprotein complex. There is a possibility that this protein is a physiological substrate of cyclic AMP-dependent protein kinase and that the phosphorylation and dephosphorylation of this substrate may be important in the translation control of adrenal polyadenylated messenger RNA.

Adrenal Cortex↗
PubMed1980

Purification and properties of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase.

Calmodulin-dependent cyclic nucleotide phosphodiesterase was purified from bovine brain to apparent homogeneity by a new procedure involving DEAE-cellulose, Affi-Gel blue, calmodulin-Sepharose 4B, and Sephadex G-200 column chromatographies. The enzyme was purified more than 3,000-fold from the brain extracts with greater than 12% yield. The purified phosphodiesterase could be activated 10- to 15-fold by calmodulin and Ca2+ to a specific enzyme activity of more than 300 mumol of cAMP hydrolyzed/min/mg of protein. Molecular weight of the enzyme was determined to be 115,800 by the sedimentation equilibirum method or 124,000 from the sedimentation constant and Stokes radius of the protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme showed a single protein band with an apparent molecular weight of 58,000. These results suggested that the calmodulin-dependent phosphodiesterase from bovine brain has a subunit structure of alpha2. Molecular weight of the complex of calmodulin and phosphodiesterase was the complex of calmodulin and phosphodiesterase was also calculated from the sedimentation constant and Stokes radius to be 159,000. Since calmodulin has a molecular weight of about 17,000, the result indicated that the stoichiometry of the complex is calmodulin2 alpha2. The catalytic subunit of cylic AMP-dependent protein kinase was found to catalyze the phosphorylation of the purified phosphodiesterase with the incorporation of 2 mol of phosphate/mol of the enzyme.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Fiberoptic bronchoscopy in the diagnosis of pulmonary tuberculosis.

Fiberoptic bronchoscopy was performed in 30 cases of suspected pulmonary tuberculosis. Sputum was negative for tubercle bacilli in all the patients, but in specimens obtained at bronchoscopy tubercle bacilli were found in 86.6%. By postbronchoscopy sputum smear examination tubercle bacilli were detected in 73.3% of the cases.

Bronchoscopy↗
PubMed1980

Ectopic alpha-adrenergic mediated accumulation of guanosine 3',5'-monophosphate in isolated adrenocortical carcinoma cells.

In the normal adrenal cell, epinephrine does not activate the rise of either cGMP or cAMP concentrations. In contrast, epinephrine activates the rise of cGMP but not cAMP concentrations in a concentration-dependent manner in isolated adrenocortical carcinoma cells. This effect was duplicated by the alpha-adrenergic agonist, phenylepherine, but was unaffected by the beta-adrenergic agonist, isoproterenol. The epinephrine-activated increase in cGMP was blocked by the alpha-adrenergic antagonist, phentolamine, but was not interfered with by the beta-adrenergic antagonist, propranolol. Neither acetylcholine, a cholinergic agonist, nor exogenous calcium caused any increase in cGMP. The rise of cGMP maximally activated by ACTH was additive with that obtained with epinephrine. These results indicate that the adrenal neoplastic cell possesses ectopic alpha-adrenergic receptors, and that epinephrine causes a rise of the cGMP level through these receptors. The data, furthermore, suggest that the receptors for ACTH and epinephrine are distinct.

Acetylcholine↗
PubMed1980

The differential phosphorylation of free cytoplasmic and membrane-bound polysomal poly(A)mRNP particles in the bovine adrenal cortex.

Free and membrane-bound polysomes were isolated and incubated under in vitro conditions that allowed the phosphorylation of contained poly(A)mRNP complexes. The three phosphoproteins of 150,000, 67,000 and 45,000 daltons were consistently present in the free poly(A)mRNP fraction and absent in the membrane-bound particles. The major phosphoprotein contained in the membrane-bound poly(A)mRNP complexes was 105,000 daltons. This protein was also present in the free cytoplasmic poly(A)mRNP fraction. It is conceivable that protein kinases differentially regulate these two classes of poly(A)mRNP particles through specific phosphorylations of their associated proteins.

Adrenal Cortex↗
PubMed1980

Coronary arterial dominance associated with congenital bicuspid aortic valve.

Gross examination was done of 186 hearts, principally from adults, for the nature of the aortic valve and the source of the posterior descending coronary artery (origin from the right coronary artery indicated as right dominance, origin from the left circumflex artery as left dominance). Exclusive of cases with coarctation of the aorta, the overall incidence of left coronary dominance in cases with congenital bicuspid aortic valves was 24.4%, while in cases with tricuspid aortic valves the incidence was 9.5%. There appears to be a greater tendency for left coronary arterial dominance in coarctation of the aorta than in the general population regardless of the type of the aortic valve.

Adolescent↗
PubMed1979

Mediatory role of calcium and guanosine 3', 5'-monophosphate in adrenocorticotropin-induced steroidogenesis by adrenal cells.

When incubated in a calcium-free medium, isolated rat fasciculata cells showed neither an increase in the concentration of guanocine 3',5'-monophosphate (cyclic GMP) nor an increase in corticosterone production in response to adrenocorticotropic hormone (ACTH). In response to submaximum and maximum steroidogenic concentrations of ACTH, corticosterone formation was directly proportional to increases in calcium concentration ranging from 0 to 2.5 mM. Higher concentration of calcium, however, inhibited maximal ACTH-induced steroidogenesis. In the absence of ACTH, calcium did not stimulate cyclic GMP accumulation and corticosterone formation. ACTH-induced corticosterone synthesis, preceded by an increase in cyclic GMP, was restored when ACTH and calcium were both present in the medium. Cyclic GMP or dibutryl cyclic GMP-induced steroidogenesis was substantially reduced in the absence of calcium, but in contrast to the ACTH effect a significant amount of corticosterone formation occurred without calcium. It is proposed that at the physiological concentrations of the hormone, calcium regulates the transduction of information between hormone receptors and guanylate cyclase.

Adrenal Cortex↗