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Biomedical subjects

R K Sharma

Publications and source records attributed to R K Sharma.

At least 451 records · Page 25Linked to original sources
PubMed1982

Immunopathology, extent and course of glomerulonephritis with crescent formation.

Ten out of 66 cases of glomerulonephritis (GN) with variable crescent formation appeared to be of post-streptococcal origin. Immunofluorescent studies of biopsies from 42 of the patients showed findings suggestive of immune complex glomerular injury in 86% whilst there was no evidence of immunologic or nonimmunologic injury in the remainder. Anti-GBM GN was not demonstrable, although it can not be certain that there were no cases amongst the patients whose biopsies were not examined by immunofluorescence. Conservative measures were adequate for the treatment of cases with less than 50% crescents. In the others, with greater than or equal to 50% crescents, appreciable improvement was observed with anticoagulation, immunosuppression and dialysis. The mortality was 30% in cases with 50-80% and 65% in cases with greater than 80% crescents. No appreciable difference in survival was observed between post-streptococcal and idiopathic cases. The single most important factor in prognosis, regardless of etiology, appeared to be the extent of crescent formation. Tubulo-interstitial damage was contributory. Necrotizing angiitis, present in 4 cases, affected the course adversely.

Adult↗
PubMed1981

The effect of five fasciolicides on malate dehydrogenase activity and mortality of Fasciola gigantica, Fasciolopsis buski and Paramphistomum explanatum.

The effect of oxyclozanide, hexachlorophene, nitroxynil, rafoxanide and diamphenethide on malate dehydrogenase activity of homogenates of Fasciola gigantica, Fasciolopsis buski and Paramphistomum explanatum was investigated. The ratio of oxaloacetate reduction to malate oxidation in homogenates of Fasciola gigantica, Fasciolopsis buski and P. explanatum was 4.5:1, 3.6:1 and 5.2:1 respectively. Oxyclozanide and rafoxanide at 10(-3) M inhibited enzyme activity by 100% in homogenates from all three species while hexachlorophene at 10(-3) M also caused 100% inhibition in homogenates from Fasciola gagantica and P. explanatum but only 65% of malate oxidation in Fasciolopsis buski homogenates. Nitroxynil at 10(-3) M produced 60% inhibition in F. buski homogenates yet had little effect at this concentration on preparations from the other species. Little inhibition was seen with diamphenethide, even at high concentrations. Rapid death of Fasicola gigantica and P. explanatum resulted in vitro when 10(-3) M oxyclozanide, hexachlorophene, nitroxynil or rafoxanide, were added to the incubation medium. Fasciolopsis buski was killed by 10(-3) M oxyclozanide but at this concentration the remaining compounds only caused reduced activity. Assay of malate dehydrogenase following drug treatment in vitro failed to show any appreciable reduction in enzyme activity in Fasciola gigantica and P. explanatum but oxyclozanide and hexachlorophene produced inhibition in Fasciolopsis buski. The mode of action of these compounds is discussed.

Animals↗
PubMed1981

Mechanism of activation of cyclic nucleotide phosphodiesterase: requirement of the binding of four Ca2+ to calmodulin for activation.

Kinetic studies on the activation of cyclic nucleotide phosphodiesterase (3',5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17) as a function of calmodulin and Ca2+ concentrations have been carried out. A general approach to analyzing the mechanism of activation, which takes into consideration the various interactions among phosphodiesterase and calmodulin liganded with Ca2+ to differing degrees, is presented. The method is applicable to other calmodulin-regulated enzyme systems. Our kinetic analysis reveals that all four Ca2+ must be bound to calmodulin for the protein to form an activated complex with phosphodiesterase. The mechanistic and regulatory advantages of having four Ca2+ sites on calmodulin can be briefly stated as follows. (i) With the enzyme--calmodulin--Ca4(2+) complex as the dominant active species, the activation of phosphodiesterase as a function of Ca2+ concentration is highly cooperative. This phenomenon serves as an effective on/off switch for phosphodiesterase activation. (ii) At normal cellular levels of Ca2+ (less than 0.1 microM), phosphodiesterase and calmodulin do not form a complex. Thus, the distribution of calmodulin among its various target enzymes is reshuffled for each Ca2+ surge. (iii) The affinity between the enzyme and the fully liganded calmodulin (0.1-1 mM) is 10(4)-10(5) times better than that in the absence of Ca2+ (greater than or equal to 10 microM). The tremendous increase in affinity can be achieved rather easily through a 10- to 20-fold increase in the affinity of Ca2+ for the enzyme-calmodulin complex in each of the four binding steps.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Tuberculosis in maintenance haemodialysis patients. Study from an endemic area.

One hundred and fifty patients requiring maintenance haemodialysis were investigated to determine the incidence and pattern of tuberculosis. Twenty patients were found to have tuberculosis, giving an incidence of 13.3 times that of the general population. The most frequent clinical presentations of tuberculosis in these patients were pyrexia, pleural effusion and lymphadenopathy. Diagnostic difficulties were encountered in 7 patients in whom therapeutic trial with anti-tubercular drugs had to be undertaken. Two patients died from tuberculosis. Five patients received renal transplants after initial treatment of tuberculosis.

Adult↗
PubMed1981

Adrenocorticotropic hormone-responsive guanylate cyclase in the particulate fraction of rat adrenal glands.

Low concentrations of ACTH, 7 x 10(-12) M, caused a marked stimulation of the 100,000 x g particulate guanylate cyclase without any detectable change in the adenylate cyclase activity. The lowest concentration of the hormone that elicited adenylate cyclase stimulation was 7 x 10(-10) M, a concentration 100--fold higher than that required to stimulate the guanylate cyclase. Although calcium was found to be obligatory in the hormonally--dependent guanylate cyclase activity, calcium alone could not duplicate the ACTH effect. Sodium nitroprusside and ascorbic acid inhibited the particulate guanylate cyclase activity. While ACTH was unable to stimulate the soluble guanylate cyclase, sodium nitroprusside markedly stimulated this enzyme. From these data, we conclude that the adrenal guanylate cyclase exists in two forms, particulate and soluble. The particulate form is specifically responsive to ACTH, and calcium is one of the essential coupling factors of this hormonally--responsive guanylate cyclase.

Adrenal Glands↗