PubMed Health⌕ Search

Biomedical subjects

R N Chakravarti

Publications and source records attributed to R N Chakravarti.

At least 19 recordsLinked to original sources
PubMed1992

Free radicals in myocardial injury: experimental and clinical studies.

The exposure of cardiac cells to OFR generated artificially, showed a marked decrease (p less than 0.01) in cellular utilization of glucose along with a significant decrease in calcium uptake (p less than 0.05). We have also provided evidence for a direct relationship of neutrophil OFR production with the extent of myocardial ischemia in patients of myocardial infarction. Our data provides evidence for implication of OFR in myocardial injury and the pivotal role played by modulators like calcium, ECGF and prostaglandins in potentiating damage to the myocardium.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Calcium transport and Ca(++)-ATPase activity in spermatozoal plasma membrane vesicles of nifedipine-administered guinea pigs.

Spermatozoal plasma membrane vesicles isolated from distal portion of the epididymis and vas deferens were found to contain Ca(++)-activated ATPase and calcium transport activities. Nifedipine was administered at two different doses (1.0 and 2.5 mg/kg b.w./day) and the effect was observed for both short- (4 week) and long-term (12 week) period. The cellular ionic calcium content and Ca(++)-ATPase activity were observed to be enhanced in the drug-treated animals. The recovery studies carried out after 4 and 6 weeks of withdrawal of the drug treatment exhibited partial to complete restoration of observed changes. The stimulatory rather than inhibitory effect of Nifedipine, a specific calcium channel blocker, on calcium uptake may suggest that voltage-sensitive calcium channels may be lacking in guinea pig spermatozoa. The stimulatory effect of the drug is speculated to be either by inhibition of Na(+)-Ca++ antiporter or G-protein activated agonistic effect or probably due to altered physicochemical properties of the drug-treated sperm plasma membranes.

5'-Nucleotidase↗
PubMed1992

Effect of indomethacin on serum lipids, lipoproteins, prostaglandins and the extent and severity of atherosclerosis in rhesus monkeys.

The present study evaluated indomethacin therapy--a nonsteroidal anti-inflammatory drug--on experimental hyperlipidemia and atherosclerosis in Rhesus monkeys. Twenty-four monkeys were divided randomly into four groups of six. Two groups received stock pellet diet and two were given an atherogenic diet for six months. After this period, one stock diet-fed group and one atherogenic diet-fed group were treated with oral indomethacin (2.5 mg) on alternate days for a further six months. Serum lipids and lipoproteins were markedly elevated in atherogenic diet-fed monkeys. Generally, indomethacin did not exert a hypocholesterolemic effect; however, liver cholesterol was decreased (P less than 0.05) in atherogenic diet-fed monkeys treated with indomethacin. High density lipoprotein cholesterol was increased in stock diet-fed, indomethacin-treated monkeys but not in atherogenic diet-fed, indomethacin-treated monkeys. Apoprotein A-I was not affected by indomethacin in either stock or atherogenic diet-fed monkeys; however, the drug produced a significant (P less than 0.01) reduction of serum thromboxane B2 in stock diet-fed monkeys, without restoring the 6-keto-prostaglandin F1 alpha to pretreatment levels. A protective role of the drug was noted on both the extent and severity of aortic and coronary atherosclerosis.

Animals↗
PubMed1992

Aortic lysosomal hydrolases and pathological alterations in hypertensive and/or atherogenic diet fed rhesus monkeys.

Aortic lysosomal enzyme activities have been evaluated in relation to the extent and severity of aortic atherosclerosis in rhesus monkeys to see the biochemical and pathological effects of renal hypertension in experimental atherogenesis. The frequency and size of atherosclerotic plaques in aortas of atherogenic diet fed and/or hypertensive monkeys were calculated and an overall score of aortic atherosclerosis was computed on the basis of the gamut of pathological findings in relation to the biochemical alterations. This overall score of atherosclerosis was found to be significantly (p less than 0.01) greater in animals of all experimental groups as compared to the controls.

Animals↗
PubMed1990

Verapamil stimulates Ca(++)-uptake and Ca(++)-ATPase in plasma membrane vesicles of guinea pig spermatozoa.

Verapamil, a potent calcium channel blocker, was administered orally at three different doses to guinea pigs for both short- (4 weeks) and long-term (12 weeks) effects. The drug treatment stimulated Ca(++)-transport and Ca(++)-activated ATPase in isolated plasma membrane vesicles of guinea pig spermatozoa. Ca(++)-uptake studies exhibited partial to complete restoration of stimulated Ca(++)-transport during recovery period, whereas the CA(++)-activated ATPase system remained stimulated even after 4 and 6 weeks of withdrawal of the drug treatment. The lack of inhibitory effect of verapamil on Ca(++)-uptake ruled out the involvement of calcium channels in spermatozoal calcium uptake in guinea pigs. The stimulatory effect of the drug on CA(++)-uptake, on the other hand, might indicate the possible capability of this lipophilic compound to induce favourable changes in the lipid microenvironment of the membrane, wherein the integral membrane proteins operate.

Animals↗
PubMed1990

Effect of verapamil on different spermatozoal functions in guinea pigs--a preliminary study.

Verapamil, a calcium channel blocker, was administered orally using three different doses to guinea pigs. Both short-term (4 weeks) and long-term (12 weeks) effects of the drug were observed. The drug administration resulted in a marked decrease in sperm density, sperm motility and cellular energy content (ATP). Zona pellucida penetration by the sperm obtained from drug-treated animals was significantly lower when compared with sperm from normal animals. Histopathological findings exhibited partial arrest of spermatogenesis. Partial to complete recovery was observed after 4 and 6 weeks of withdrawal of the drug treatment.

Adenosine Triphosphate↗
PubMed1990

Distribution of apolipoproteins in normal individuals of various age groups.

The study comprised normal controls with 10 males and 10 females in each decade of age starting from birth till greater than 70 years of age and also 20 cord blood samples (10 males and 10 females). In normal controls there was a progressive increase in the levels of total cholesterol and triglycerides in both men and women with age. Women had significantly lower levels of Tc and TG as compared to men until 40 years of age. Beyond this age levels of Tc were similar to those in men. HDL-c was lower in girls below 10 years of age compared to boys. Above 10 years of age women had significantly higher levels of HDL-c. Apo A-I and A-II levels were also significantly higher in women compared to men.

Adolescent↗
PubMed1990

Short-term therapy of atherosclerosis with low dose indomethacin: an experimental study.

The effects of low dose indomethacin therapy in primary prevention of diet-induced atherosclerosis of rhesus monkeys was studied. The parameters studied were serum cholesterol concentration, thromboxane A2 (T x B2), prostacyclin (6-keto-PGF1 alpha) in serum/plasma, and the extent and intensity of coronary atherosclerosis. Although indomethacin did not affect serum cholesterol, it reduced serum T x B2 significantly (P less than 0.01). Plasma 6-keto-PGF1 alpha was not restored to the pretreatment level. A significant protective role of the drug was noted as far as coronary atherosclerosis is concerned (P less than 0.01).

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Effects on intestinal nutrient uptake and brush border membrane enzymes in response to atherogenic diet in rhesus monkeys.

Transport of nutrients and kinetic parameters (Vmax and Km) of brush border membrane (BBM) enzymes were studied in duodenum, jejunum, and ileum from atherogenic diet-fed monkeys. The Km remained unaltered while feeding of atherogenic diet resulted in higher Vmax of sucrase, maltase, and alkaline phosphatase and lower Vmax of gamma-glutamyltranspeptidase and leucine-aminopeptidase compared to controls. Na+-dependent D-glucose transport was higher in duodenum and jejunum and unaltered in ileum. In contrast to D-glucose transport, the transport of amino acids was decreased in all three intestinal segments from atherogenic diet-fed monkeys.

Alkaline Phosphatase↗
PubMed1989

Enzyme immunoassay (ELISA) for the detection of anticarbohydrate antibodies in rheumatic fever and rheumatic heart disease.

Antibodies to group A streptococcal polysaccharide were estimated in the following groups of patients: (I) Patients with uncomplicated streptococcal pharyngitis: 10 patients, followed up for 3 months. (II) Patients with acute rheumatic fever: 8 patients with first attack followed up for one year. (III) Patients with reactivated rheumatic heart disease: 10 patients, followed up for one year. (IV) Patients with chronic rheumatic heart disease: followed up for one year. (V) normal controls without any history of sore throat/fever/vaccination/rheumatic disease: 10 patients followed up for one year. Group (I) patients did not show any significant elevation in anticarbohydrate antibodies by both ELISA and RIA. In the case of (III) and (IV), antibody levels were significantly higher as compared to group (V) and remained so till one year of follow up. In group (II) patients there was no significant rise in antibody levels. There was a good correlation between the ELISA and RIA used to detect the antibody levels. These findings suggest that the use of ELISA to detect anticarbohydrate antibody can be of help in diagnosing cases of rheumatic heart disease (both acute and chronic RHD).

Enzyme-Linked Immunosorbent Assay↗
PubMed1989

Effect of vasectomy on serum lipids, platelet aggregability and development of ischaemic heart disease in rhesus monkeys.

In this study the long term effects of vasectomy on serum lipid profile, in vitro platelet aggregability and the risk of developing acute myocardial infarction have been elucidated in a monkey model. Four groups were made viz. (I) atherogenic diet fed vasectomised, (II) atherogenic diet fed control, (III) stock diet fed vasectomised and (IV) stock diet fed control. The respective diets were fed for first 6 months and then half of the atherogenic and stock diet fed monkeys were bilaterally vasectomised. The remaining monkeys were sham-vasectomised. At the end of one year, norepinephrine infusion was given to all the monkeys each day for 2 hrs, for 3 consecutive days and animals sacrificed after 96 hrs. Although serum lipids were not altered following vasectomy, platelet aggregation response was significantly enhanced in atherogenic diet fed animals. ECG changes were suggestive of acute myocardial ischaemia in 4 monkeys, 2 each from gp. I and II. Histopathology of heart revealed patchy myocardial necrosis and haemorrhage only in one monkey of gp. I, while others had fuchsinorrhagia indicating ischaemic change. These findings are in contrast to those seen in vasectomised human subjects.

Animals↗
PubMed1988

Physiological and histopathological changes in the intestines of mice challenged with S. typhi.

Transport of Na+, Cl-, Ca2+ and 3-0-methyl-D-glucose (a non-metabolizable analogue of D-glucose) was worked out in control, infected and immunized-infected animals along with histopathological studies of the intestines in these groups. There was significant decrease (p less than 0.01) in net absorption of Na+ and Cl- in the infected group as compared to that in the control group. There was also a significant decrease (p less than 0.01) in 3-0-methyl-D-glucose uptake in the infected group. However, no change was found in the immunized group in any of the electrolytes and non-metabolizable analogue of D-glucose. These findings correlated well with the histopathological studies as the infected intestines showed complete disorganization of mucosal tissues with loss of epithelial cells from the villi whereas the mucosal lining and epithelial cells from the intestines of immunized mice were normal looking.

3-O-Methylglucose↗
PubMed1988

Towards the mechanism of protection against indomethacin induced gastro-intestinal ulceration by naloxone.

Activities of lysosomal hydrolases have been evaluated in relation to indomethacin and naloxone, using purified lysosomal fractions from rat intestinal mucosa. Indomethacin treatment significantly decreased (p less than 0.001) lysosomal enzyme activities in purified lysosomes, while an increase in the activities was observed in intestinal homogenates. However, indomethacin could not affect lysosomal system in animals pretreated with naloxone, thereby establishing that naloxone neutralises the effect of indomethacin.

Animals↗
PubMed1987

Effect of vasectomy on humoral and cell-mediated immunity in monkeys with experimentally induced atherosclerosis.

The development of humoral and cell-mediated immune responses and circulating immune complexes following vasectomy were studied in rhesus monkeys fed a high cholesterol (atherogenic) diet. Four groups of monkeys were studied: (i) sham-vasectomized males fed a normal stock diet, (ii) sham-vasectomized males fed an atherogenic diet, (iii) vasectomized males fed a normal stock diet, and (iv) vasectomized males fed an atherogenic diet. Monkeys were observed for a period of 1.5 years. Sperm agglutinins and immobilizins in serum were detected in 100 and 60%, respectively, of vasectomized monkeys fed stock diet. In contrast, 60% of vasectomized monkeys fed an atherogenic diet showed agglutinins in their sera and only 20% exhibited immobilizins. The sensitization of lymphocytes by seminal plasma antigens was of a lower order in vasectomized monkeys fed an atherogenic diet as compared to those maintained on a stock diet. Circulating immune complexes (CIC) were present in both the groups of vasectomized monkeys but the level was higher in animals fed an atherogenic diet. The aortic atherosclerosis score was increased significantly in vasectomized monkeys fed an atherogenic diet, whereas the coronary atherosclerosis score was increased both in vasectomized males and in animals fed an atherogenic diet.

Animals↗
PubMed1987

Isolation of monkey aortic lysosomes using Percoll density gradient.

A novel technique involving the Percoll density gradient and 0.01M phosphate buffer has been employed for the first time on aortic tissue for isolation of lysosomes. The purity of the lysosomes has been established by marker-enzymes, acid phosphatase and N-acetyl-beta-D-glucosaminidase and latent activities of lysosomal hydrolases. The heavier fraction (density 1.08) obtained after Percoll density gradient centrifugation showed high specific activities of lysosomal hydrolases and these enzymes were markedly latent. Moreover this heavier (lysosome rich) fraction has been noted to be free of other sub-cellular contaminants.

Acetylglucosaminidase↗