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Biomedical subjects

R Kakkar

Publications and source records attributed to R Kakkar.

At least 37 records · Page 2Linked to original sources
PubMed1997

In vitro phosphorylation of bovine cardiac muscle high molecular weight calmodulin binding protein by cyclic AMP-dependent protein kinase and dephosphorylation by calmodulin-dependent phosphatase.

High molecular weight calmodulin binding protein (HMWCaMBP) is one of the major proteins expressed in bovine cardiac muscle. In this study, we report the phosphorylation and dephosphorylation of HMWCaMBP in vitro with a view to understand the function of this protein. The HMWCaMBP was phosphorylated by cAMP-dependent protein kinase with the incorporation of 2.30 mol of phosphate/mol of protein in the presence of EGTA. When phosphorylation was carried out in the presence of Ca2+/calmodulin (CaM), the incorporation of phosphate was reduced to 1.40 mol of phosphate/mol of protein. The decrease in the stoichometry of phosphorylation by Ca2+/CaM appears to be substrate directed i.e. due to the interaction of Ca2+/CaM with HMWCaMBP. The phosphorylated HMWCaMBP was unable to compete for free CaM in a CaM-dependent cyclic nucleotide phosphodiesterase (CaMPDE) assay. These results suggest that the phosphorylation sites may reside in or in proximity to the CaM-binding domain on HMWCaMBP since phosphorylated HMWCaMBP did not inhibit CaMPDE activity. HMWCaMBP was dephosphorylated by CaM-dependent phosphatase, calcineurin.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

Tyrosine phosphorylation in contraction of opossum esophageal longitudinal muscle in response to SNP.

Sodium nitroprusside (SNP) has been shown to elicit a guanosine 3',5'-cyclic monophosphate (cGMP)-mediated, indomethacin-sensitive contraction of the opossum esophageal longitudinal muscle. We examined the role of tyrosine phosphorylation in the signal transduction pathway of contractions induced by SNP and cGMP in longitudinal muscle strips in vitro. Force of isometric contractions was expressed as the percentage of responses to KCl (73 mM). SNP (100 microM)-induced contractions were 75 +/- 5% before and 3 +/- 2% after 50 microM genistein (P < 0.005) and 86 +/- 16% before and 0 +/- 0% after 50 microM tyrphostin B46. Contractions in response to 8-bromo-cGMP (8-BrcGMP; 1 mM) were 74 +/- 15% before and 3 +/- 2% after genistein (P < 0.01) and 63 +/- 15% before and 18 +/- 4% after tyrphostin B46 (P < 0.05). In contrast, KCl-induced contractions were 82 +/- 8% and 96 +/- 9% of the control value after genistein and tyrphostin B46 treatments, respectively (P > 0.05 for both). Carbachol contractions were partially suppressed by genistein (106 +/- 8% vs. 79 +/- 8%; P < 0.05) but unaffected by tyrphostin B46 (114 +/- 10% vs. 107 +/- 12%; P > 0.05). Western blot analysis revealed a 116-kDa phosphotyrosine protein in the control muscle strips. The level of this protein was increased to 206 +/- 15% of control after SNP treatment. Both genistein and tyrphostin B46 blocked this increase. These studies show that contractions of the esophageal longitudinal muscle induced by SNP and cGMP utilize a signal transduction pathway different from that used by the depolarizing agent KCl and the muscarinic agonist carbachol. Contractions induced by SNP and cGMP involve tyrosine phosphorylation of a protein, possibly identified as a 116-kDa protein, as a key step in the signaling pathway.

Animals↗
PubMed1997

Increased longevity, reduced fecundity, and delayed development in fruitfly (Zaprionus paravittiger) fed on butylated hydroxy anisole.

Oxygen free radicals are generated as a by-product during normal metabolism, and they cause damage to proteins, lipids, and DNA in organisms. The defense system of the body counteracts these highly reactive chemical moieties and neutralizes them. However, a small fraction of free radicals escapes, which causes lipid peroxidation and hence aging of the organism. It has been hypothesized that, if the free radicals are arrested/reduced, then aging can be delayed or life span could be enhanced. To test the above hypothesis, we fed butylated hydroxy anisole (BHA) to a drosophilid insect, Zaprionus paravittiger, and observed its effect on life span, fecundity, and developmental period. The insects were reared and maintained on standard corn meal agar (CMA) medium at 26 degrees +/- 2 degrees C. Various concentrations (1, 5, 10, 25, 50, and 100 mM) of BHA were mixed with CMA medium, and the cultures were reared and maintained on these mixtures to study the life span of insects. Survivor curves showed that lower concentrations (5, 10, 25 mM) of BHA increased the life span, while higher concentrations (50, 100 mM), which were rather toxic, decreased life span. The most suitable concentration was 10 mM, which increased median (LT50) (27% and 15% in male and female) and maximum (LT100) (18% and 27% in male and female) life spans of insects maximally. Females exhibited longer life spans compared with males. The cultures were fed on the optimal concentration (10 mM) of BHA to study its effect on developmental period and egg-laying rate. The total developmental period was delayed by 7.2%, and egg-laying rate was reduced by 19.7% on BHA feeding. The extension in developmental period and reduction in egg-laying capacity could be the contributory factors to the favorable effect of BHA on life span.

Administration, Oral↗
PubMed1997

Biological significance of phosphorylation and myristoylation in the regulation of cardiac muscle proteins.

Post-translational modification has long been recognized as a way in which the properties of proteins may be subtly altered after synthesis of the polypeptide chain is complete. Amongst the moieties most commonly encountered covalently attached to proteins are oligosaccharides, phosphate, acetyl, formyl and nucleosides. Protein phosphorylation and dephosphorylation is one of the most prevalent and best understood modifications employed in cellular regulation. The bovine heart calmodulin-dependent cyclic nucleotide phosphodiesterase (CaMPEDE) can be phosphorylated by cAMP-dependent protein kinase, resulting in a decrease in the enzyme's affinity for Ca2+ and calmodulin (CaM). The phosphorylation of CaMPDE is blocked by Ca2+ and CaM and reversed by the CaM-dependent phosphatase (calcineurin). The dephosphorylation is accompanied by an increase in the affinity of the phosphodiesterase for CaM. Analysis of the complex regulatory properties of CaMPDE has led to the suggestion that fluxes of cAMP and Ca2+ during cell activations are closely coupled and that the CaMPDE play a key role in the signal coupling phenomenon. The high molecular weight calmodulin binding protein (HMWCaMBP) was phosphorylated by cAMP-dependent protein kinase. Phosphorylation of HMWCBP was higher in the absence of Ca2+/CaM then in the presence of Ca2+/CaM and reversed by the CaM-dependent phosphatase. Recently, it has become apparent that the binding of myristate to proteins is also widespread in eukaryotic cells and viruses and certainly is of great importance to the correct functioning of an organism. Myristoyl CoA:protein N-myristoyltransferase (NMT) catalyses the attachment of myristate to the amino-terminal glycine residue of various signal transduction proteins. Cardiac tissue express high levels of cAMP-dependent protein kinase whose catalytic subunit is myristoylated. The subcellular localization of bovine cardiac muscle NMT indicated a majority of the activity was localized in cytoplasm. Under native conditions the enzyme exhibited an apparent molecular mass of 50 kDa. Recovery of NMT activity, from both cytosol and particulate fractions, was found to be higher than the total activity in crude homogenates, suggesting that particulate fraction may contain an inhibitory activity towards NMT. Research in our laboratory has been focusing on the covalent modification of proteins and regulation of various signal transduction proteins. This special review is designed to summarize some aspects of the current work on co- and post-translational modification of proteins in cardiac muscle.

Acyltransferases↗
PubMed1997

A critical evaluation of anti-peroxidant effect of intravenous magnesium in acute aluminium phosphide poisoning.

The anti-peroxidant effect of intravenous magnesium was evaluated in 50 patients with acute aluminium phosphide poisoning. The patients were divided into two groups, one who received magnesium sulphate therapy (Group I) and the other who did not (Group II). The clinical and biochemical parameters in both groups were comparable. Finding of increased mean malonyl-di-aldehyde (MDA) levels in group I (3.18 +/- 0.93 micromol/L) and group II (3.15 +/- 0.78 mmol/L) combined with low blood levels of reduced glutathione (18.5 +/- 1.6 mg/dl in group I) and (17.8 +/- 1.4 mg/dl in group II) indicated oxidative stress leading to accelerated lipid peroxidation in the early phase (0-6 h) of AlP poisoning. A significant fall in MDA levels was observed after 2 h in the magnesium treated group (group I) compared to the non-treated group (group II) and levels became normal between 48-72 h. Similarly reduced glutathione started recovering between 12-24 h which became significant after 24 h and full recovery took place between 48-72 h in the magnesium treated group (group I). Both these parameters suggested an anti-peroxidant effect of magnesium. There was also a slight fall in MDA levels and a rise in reduced glutathione in the non-treated group II patients. This could be due to elimination of phosphine (PH3). We hypothesize that oxidative stress in AlP poisoning buffered the magnesium leading to a transient fall in magnesium and magnesium dependent GSH, resulting in increased susceptibility of oxygen free radical injury and accelerated lipid peroxidation. The fall in MDA and slower rise in GSH in group I than in group II suggested magnesium combated free radical stress slowly and independent of elimination of phosphine. This hypothesis was further strengthened by similar observations when both these parameters were compared in survivors in both groups. Mortality was higher in group II than in group I (44 per cent vs 20 per cent) and was probably related directly to oxidative stress.

Adolescent↗
PubMed1996

Inhibition of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase isozymes by deprenyl.

Intracellular concentrations of cyclic nucleotides is regulated by cyclic nucleotide phosphodiesterases and calmodulin-dependent cyclic nucleotide phosphodiesterases (CaMPDE), one of the most intensively studied and best characterized phosphodiesterases. In the present study, the effect of an antiparkinsonian agent, deprenyl (selegeline hydrochloride) which is believed to be a selective inhibitor of monoamine oxidase-B, on bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase (CaMPDE) isozymes have been investigated. The findings indicated that deprenyl inhibited brain 60 kDa isozyme, however the inhibition for brain 63 kDa CaMPDE was observed to a lesser extent. The inhibition of brain 60 kDa CaMPDE was overcome by increasing the concentration of calmodulin suggesting that deprenyl may be calmodulin antagonist or act specifically and reversibly on the action of calmodulin. The 60 kDa CaMPDE isozyme is predominantly expressed in brain and its inhibition can result in increased intracellular levels of cAMP. The increased intracellular levels of cAMP have a protective role for dopaminergic neurons. Therefore, deprenyl may be a valuable tool to investigate the physiological roles of brain CaMPDE isozymes in progression of Parkinson's disease and gives a new insight into the action of this drug.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Calmodulin-dependent protein kinase II from bovine cardiac muscle: purification and differential activation by calcium.

Calmodulin-dependent protein kinase II was purified to apparent homogeneity with a high yield from the total calmodulin-binding protein fraction of bovine cardiac muscle in a single step by gel filtration column chromatography. This procedure is simple and suitable for adaptation to large scale preparations. The purified calmodulin-dependent protein kinase has a specific enzymic activity of 2.4 mumol/min/mg when mixed histone was used as a substrate. The preparation of enzyme appears to be homogeneous when examined by SDS-PAGE. The molecular weight of the enzyme was determined to be 570 kDa by gel filtration. SDS-PAGE of the enzyme subunit showed a single protein band with an apparent molecular weight of 56 kDa. These results suggest that the calmodulin-dependent protein kinase II from bovine heart is composed of 10 identical subunits. Anti-peptide antibody raised against multifunctional calmodulin-dependent protein kinase II from rat brain showed a single immunoreactive band of 56 kDa on Western blot. These results suggested that bovine cardiac muscle calmodulin-dependent protein kinase could resemble the brain isozyme. Calmodulin-dependent protein kinase II undergoes autophosphorylation with a maximal incorporation of 1 mol of phosphate per mol of the subunit of the enzyme and the autophosphorylated enzyme remains active in the absence of Ca2+ and calmodulin. The concentration of Ca2+ required for the activation of calmodulin-dependent protein kinase II depends on the level of calmodulin in the reaction.

Acrylic Resins↗
PubMed1996

Time course study of oxidative stress in aorta and heart of diabetic rat.

1. Oxygen free radicals have been suggested to be a contributory factor in complications of diabetes mellitus. In the present study, we investigated the lipid peroxide level [thiobarbituric acid-reactive substances (TBARS)] and activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) in aorta, heart and blood of control and streptozotocin-induced diabetic rats at various stages of development of diabetes (0 to 6 weeks). 2. There was no change in the TBARS levels of aorta, heart and blood in the control group. A significant (P < 0.05) increase in TBARS levels of aorta, heart and blood was observed in the diabetic group. 3. There were no significant changes in the activities of superoxide dismutase, catalase and glutathione peroxidase in the aorta, heart and blood of control rats at all time intervals. In the diabetic group, there was a significant (P < 0.05) increase in the activity of superoxide dismutase and glutathione peroxidase in aorta from the fourth week onwards while the activity of catalase increased at all time intervals. In the heart of diabetic rats, the activity of total superoxide dismutase and Cu-Zn-superoxide dismutase increased significantly (P < 0.05) from the second week onwards while activity of Mn-superoxide dismutase decreased at the fourth week and increased at the sixth week. The activity of catalase and glutathione peroxidase increased significantly (P < 0.05) at all time intervals. In the blood, the activity of superoxide dismutase and glutathione peroxidase increased from the third week while catalase activity increased from the fourth week. 4. The present findings suggest that oxidative stress starts at early onset of diabetes mellitus and increases progressively.

Animals↗
PubMed1996

Gender specific alterations in antioxidant status of aging Zaprionus paravittiger fed on propyl gallate.

Zaprionus paravittiger fed on propyl gallate (PG) supplemented diet (2.5, 25 and 250 micrograms/ml) showed an increase in life span. Further increase in concentration (2500, 5000 and 7500 micrograms/ml) accelerated the mortality rate. Females exhibited longer life span as compared to males. Antioxidant enzymes (catalase, peroxidase and glutathione reductase) were measured in control and optimum concentration of PG (25 micrograms/ml) fed flies at various age intervals. Antioxidant enzyme activities showed an increase during reproductive phase. Catalase and glutathione reductase activities decreased with age however no significant change was observed in peroxidase activity. The females exhibited higher enzyme activities as compared to males in control and PG fed group at most of the age intervals. PG feeding caused a significant increase in catalase and glutathione reductase activities in both the sexes. These findings suggest the PG has dose dependent and sex specific influence on longevity of Z. paravittiger and support the view that longevity and activity of antioxidant enzymes are positively linked.

Aging↗
PubMed1996

Effect of vitamin E on life span, malondialdehyde content and antioxidant enzymes in aging Zaprionus paravittiger.

Zaprionus paravittiger fed with vitamin E supplemented diet (1, 5 and 10 micrograms/ml) showed an increase in median and maximum life spans. Further increase in concentration accelerated the mortality rate. Females exhibited longer life span as compared to males. Malondialdehyde (MDA) content and antioxidant enzymes (catalase and peroxidase) were measured in control and optimum concentration of vitamin E (5 micrograms/ml)-fed flies at various age intervals. MDA content showed an increase with age in control and vitamin E-fed group whereas catalase and proxidase activities showed a decrease with age. The females exhibited lower MDA content and higher activities of catalase and peroxidase as compared to males in control and vitamin E group. Vitamin E feeding caused a significant decrease in MDA and increase in catalase and peroxidase activities. These findings suggest that vitamin E has dose-dependent and sex-specific influence on longevity of Z. paravittiger and support the view that longevity and activity of antioxidant enzymes are positively linked.

Aging↗
PubMed1995

Lipid peroxidation and activity of antioxidant enzymes in diabetic rats.

We hypothesized that oxygen free radicals (OFRs) may be involved in pathogenesis of diabetic complications. We therefore investigated the levels of lipid peroxidation by measuring thiobarbituric acid reactive substances (TBARS) and activity of antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT)] in tissues and blood of streptozotocin (STZ)-induced diabetic rats. The animals were divided into two groups: control and diabetic. After 10 weeks (wks) of diabetes the animals were sacrificed and liver, heart, pancreas, kidney and blood were collected for measurement of various biochemical parameters. Diabetes was associated with a significant increase in TBARS in pancreas, heart and blood. The activity of CAT increased in liver, heart and blood but decreased in kidney. GSH-Px activity increased in pancreas and kidney while SOD activity increased in liver, heart and pancreas. Our findings suggest that oxidative stress occurs in diabetic state and that oxidative damage to tissues may be a contributory factor in complications associated with diabetes.

Animals↗
PubMed1995

Methionine-induced alterations in the life span, antioxidant enzymes, and peroxide levels in aging Zaprionus paravittiger (Diptera).

The median and maximum life spans of both sexes of Zaprionus paravittiger increased with methionine (100 mM) feeding. It was accompanied by higher catalase and peroxidase enzyme activities. The lipid peroxide level as measured by malondialdehyde content and the inorganic peroxides showed an increase with age and a decrease in methionine-fed insects. The reduction was, however, more pronounced in females than in males. The findings indicate that a life-prolonging effect of methionine on Z. paravittiger may be by virtue of its free radical scavenging effect.

Animals↗
PubMed1992

Survival in patients with systemic lupus erythematosus in India.

Survival in patients with systemic lupus erythematosus (SLE) in developed countries has improved considerably over the last 2 decades. In India, however, survival in patients with SLE reported 5 years ago from this tertiary referral centre was very poor. The present study was conducted to examine trends, if any, towards improvement in the survival of patients with SLE attending the same centre during the period 1981-1990. No statistically significant change in survival was noted. It appears that improvement in the survival of SLE patients would require an overall improvement in the standard of medical care in India.

Adult↗
PubMed1992

Neurological manifestations of leukemia--clinical and pathological findings.

Out of 70 cases of leukemia studied, 19 had neurological manifestations. All cases were autopsied. Leukemic infiltrates and intracranial hemorrhages produced various neurological manifestations. In autopsied cases 37.2% showed infiltrative changes. Intracranial hemorrhages contributed to 20%, the cause of which were due to thrombocytopenia and leukostasis. Leukemic nodules, demyelination and astrocytosis, gliosis were also seen on histopathology.

Adolescent↗