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Biomedical subjects

M C Sharma

Publications and source records attributed to M C Sharma.

At least 145 records · Page 8Linked to original sources
PubMed1995

Purification and characterization of constituent testosterone 2 alpha-hydroxylase (cytochrome P450(2)alpha) from mouse liver.

Hepatic microsomal testosterone/androstenedione 2 alpha-hydroxylase (i.e., cytochrome P450(2)alpha) was purified from female CD-1 mice. Protein purification was monitored in eluates from Fractogel, DEAE-sephacel, and hydroxylapatite columns at heme absorbing 417 nm and by cytochrome P450 content, reactivity to a monoclonal antibody against female-specific rat cytochrome P450 2C12, and testosterone 2 alpha-hydroxylase activity. The catalytic activity of the purified cytochrome P450(2)alpha, exhibiting a high degree of regioselectivity and stereospecificity, was basically restricted to the 2 alpha-hydroxylation of testosterone and androstenedione; representing > 96% and > 92% of these respective metabolites. Polyclonal antibodies against cytochrome P450(2)alpha exhibited a dose-dependent and very selective inhibition of testosterone 2 alpha-hydroxylation. The specific cytochrome P450 content of the purified cytochrome P450(2)alpha fraction was 12.06 nmol/mg protein. The specific testosterone 2 alpha-hydroxylase activity of the purified protein was 14 nmol/min/nmol cytochrome P450, which was about 60-fold higher than the respective microsomes. The apparent subunit molecular weight of cytochrome P450(2)alpha was 51,000 and the protein appeared as a single band on sodium dodecyl sulfate polyacrylamide gels. The amino-terminal sequence analysis indicates that cytochrome P450(2)alpha is a member of the murine cytochrome P450 2d family.

Amino Acid Sequence↗
PubMed1995

Hypofibrinogenaemia is the commonest congenital fibrinogen abnormality in north India.

Congenital abnormalities of fibrinogen are rare disorders and all the cases reported in the literature indicate that the incidence of afibrinogenaemia is much higher than hypofibrinogenaemia. Of the total of 20 cases reported from other parts of India only one was congenital hypofibrinogenaemia. In contrast, the present study showed eight patients with congenital hypofibrinogenaemia among a total of nine unrelated North Indian patients with a fibrinogen abnormality. This disproportionately high incidence of hypofibrinogenaemia suggests the existence of a distinct genetic defect in the North Indian population.

Adolescent↗
PubMed1995

Simulataneous isolation of NADPH-cytochrome P-450 reductase and cytochrome P-450 using tentacle ion-exchange chromatography and interspecies comparison of the reductase activity.

Using the same initial Fractogel (tentacle) ion-exchange chromatography to isolate murine cytochrome P-450, mouse hepatic NADPH-cytochrome P-450 reductase (EC 1.6.2.4) was simultaneously isolated from solubilized liver microsomes and purified on a DE-52 column to a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme had a molecular mass of 77 kD, and its specific activity was 25.4 mumol.min-1.mg protein-1. Purified constitutive mouse liver NADPH-cytochrome P-450 reductase was successfully reconstituted in vitro with dilauroylphosphatidyl-choline and constitutive purified mouse testosterone 2 alpha-hydroxylase (cytochrome P-450(2)alpha) with an observed activity of 13.8 nmol.min-1.nmol P-450-1. Although the partially purified reductase obtained from the Fractogel column was contaminated by significant levels of two unidentified proteins, it was as equally effective in the reconstituted system as the DE-52-derived purified reductase. Lastly, we found that rat and mouse NADPH-cytochrome P-450 reductases were similarly effective in supporting the catalytic activity of rat cytochrome P-450 2B1, but the murine reductase was 50% more effective than the rat reductase in a reconstituted system containing mouse cytochrome P-450(2)alpha.

Animals↗
PubMed1994

Inhibition of NAD(P)H:quinone oxidoreductase1 in ethacrynic acid-resistant human colon carcinoma cells.

Human colon carcinoma HT29 cells sensitive (WT) and resistant (HT/M and HT/S) to ethacrynic acid (EA) were used to investigate the role of NAD(P)H:quinone oxidoreductase1 (NQO1) in drug resistance. Significant decreases in the levels of NQO1 activity were observed in resistant cells as compared with the sensitive cells. However, the decreased activities of NQO1 in resistant cells were found to be due to inhibition of the enzyme by EA. Human NQO1 cDNA-derived protein in monkey kidney COS1 cell extract was used to demonstrate that in vitro inhibition of NQO1 activity by EA was rapid, reversible and concentration dependent, with an IC50 value of 250 microM. These results suggest that NQO1 may not have a role in EA resistance of human colon carcinoma HT29 cells and that EA is an inhibitor of NQO1 activity.

Animals↗
PubMed1994

Leishmania donovani: hemolytic activity of promastigotes.

A hemolytically active component was found to be present in Leishmania donovani promastigotes for the first time. It lysed human and rabbit erythrocytes to varying degrees. The optimal pH for the activity was found to be 5.8. The rate of hemolysis was dependent on both erythrocyte and parasite concentrations. Parasites in the log phase were more effective in lysing erythrocytes than those in the stationary phase. Centrifugation at 10,000g showed major activity in the pellet fraction of the autolysate. Boiling in a water bath for 5 min reduced 98% of the hemolytic activity, which was also found to be inhibited by trypsin. The presence of such a hemolytic factor appears to be important in the nutrition of this parasite.

Animals↗
PubMed1994

Neuropathological studies on Plasmodium yoelii nigeriensis-induced malaria in mice.

Malaria infection in mice was produced by intraperitoneal inoculation of 10(6) erythrocytes parasitized with Plasmodium yoelii nigeriensis, a virulent strain of murine malaria. About one week after infection parasitaemia ranged between 60 and 80%, and 100% mortality was observed. Infected animals were killed 6 days after infection to allow the examination of brain tissue. Electron microscopical observations revealed marked damage to cerebral vascular vessel walls with separation of muscular layers, media and adventitia. The endothelial cell layer was discontinuous in places. Activated fibroblast cells producing collagen fibres were seen around the necrotic region of cerebral vasculature. Some parasitized erythrocytes were also seen attached to the endothelial cell lining. Cerebral oedema was prominent around the blood vessels.

Animals↗
PubMed1994

Prognostic role of screening tests of haemostasis and underlying diseases in acute disseminated intra-vascular coagulation in adults.

The significance of precipitating causes of acute disseminated intra-vascular coagulation (DIC) and the severity of derangement of haemostasis based on laboratory investigations carried out initially were evaluated in 98 patients and was related to the fatal outcome in them. It was seen that septicaemia was the commonest precipitating cause. Survival was better in patients in whom DIC was precipitated by obstetric causes compared with those with septicaemia (P < 0.01). Death was also more frequently associated in patients with higher prothrombin time (PPT) ratio (> 1.5) and/or higher activated partial thromboplastin time (APTT) ratio (> 2.5) as compared to their lower values (P < 0.01 each). Death occurred in all the seventeen patients in whom septicaemia was present along with PPT ratio of > 1.5. It is concluded that deranged haemostasis and presence of septicaemia both independent of each other, contribute to the fatal outcome in acute DIC. Combination of both is associated with poorest prognosis.

Acute Disease↗
PubMed1993

Larvicidal and chemosterilant activity of Annona squamosa alkaloids against Anopheles stephensi.

Alkaloids isolated from Annona squamosa have shown larvicidal growth-regulating and chemosterilant activities against Anopheles stephensi at concentrations of 50 to 200 ppm. Adults exposed as larvae to different treatments showed reduced fecundity and fertility in females. Mortality in the larvae, pupae and adults produced about a 52-92% decrease in the laboratory experiment. The total developmental period was slightly reduced from the control. Treatment with the alkaloids had a significant effect on the mortality, emergence and reproductive physiology of An. stephensi.

Alkaloids↗
PubMed1992

Aberrations in cerebral vascular functions due to Plasmodium yoelii nigeriensis infection in mice.

Plasmodium yoelii nigeriensis infection in mice caused an increase in uptake of 125I-labeled bovine serum albumin, 51Cr-labeled erythrocytes and Evans blue dye from peripheral circulation into the brain. Isolated cerebral microvessels which were characterized in terms of their morphology under scanning electron microscope and enhancement of the specific activities of biochemical markers, viz. alkaline phosphatase, gamma-glutamyl transpeptidase, and monoamine oxidase, showed significant decrease in these activities due to P. yoelii nigeriensis infection. On the other hand, relatively minor (statistically insignificant) changes occurred in the first two enzyme specific activities in the cerebral cortex and monoamine oxidase registered an increase in this tissue due to infection. Histological examination of the cerebral tissue of infected animals by light and electron microscopy showed broken blood vessel walls and leakage of erythrocytes into extravascular space, some of which contained intraerythrocytic malarial parasite in a state of cell division.

Alkaline Phosphatase↗
PubMed1992

Study on the physico-chemical characteristics of breeding grounds in relation to the population density of Anopheles stephensi.

The present study which was based on the quarterly sampling and estimation of various physico-chemical factors throw light on the three significant points with regard to the population build up of Anopheles stephensi. Slightly alkaline pH is essential for higher population density, lower the salinity, higher the population density and higher amount of free ammonia in the water is accounted for the higher population density of A. stephensi.

Ammonia↗
PubMed1992

Cerebral ammonia levels and enzyme changes during Plasmodium yoelii infection in mice.

Ammonia, lactate and glutamate levels and the activities of glutamine synthetase (GS), glutamate dehydrogenase (GDH), glutaminase (GLN), aspartate transaminase (AST), phosphofructokinase (PFK) and monoamine oxidase (MAO) were compared in the brain tissue of normal and P. yoelii infected mice. The brain lactate increased by 96% at peak parasitaemia. Cerebral ammonia also exhibited an increase in infected mice which was parasitaemia dependent, while glutamate remained almost unchanged. The brain glutamine synthetase registered an increase of 35% (P < 0.001) in post-mitochondrial fractions, this effect being perceptible even at low parasitaemia, but attained constancy at parasitaemia levels higher than 20%. The activity of monoamine oxidase and phosphofructokinase increased by 105% (P < 0.02) and 41% (P < 0.05) respectively while glutamate dehydrogenase decreased by 15% (P < 0.001). Glutaminase and aspartate transaminase were not significantly influenced by infection (tested only at high parasitaemia levels). It has been postulated that cerebral hypoxia and aberrations in ammonia metabolism may both contribute towards malaria induced cerebral complications.

Ammonia↗