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S Kumar

Publications and source records attributed to S Kumar.

At least 1,099 records · Page 61Linked to original sources
PubMed1996

Reduction-oxidation (redox) state regulation of extracellular matrix metalloproteinases and tissue inhibitors in cardiac normal and transformed fibroblast cells.

Latent matrix metalloproteinases (MMPs) in normal myocardium are activated in end-stage heart failure. In vitro oxidized glutathione (GSSG) activates myocardial MMPs which contains a cysteine residue. In vivo GSSG induce the collagen lysis and cardiac dilatation. To assess whether thiol and non-thiol reducing agents have direct effect on the interstitial human heart fibroblast (HHF) proliferation and MMP expression, HHF and polyoma virus transformed fibroblast cells were cultured with or without the thiol-containing reduced (GSH) or oxidized (GSSG) glutathiones, pyrrolidine dithiocarbamate (PDTC) and N-acetylcysteine (NAC), and non-thiol ascorbic acid. After 100 micrograms/ml (approximately 0.3 mM) GSH or PDTC treatment the proliferative (synthetic) phenotype of transformed fibroblast cells was changed to quiescent (contractile) phenotype. Also, after GSH, PDTC, and ascorbic acid treatment the medium was then analyzed for MMP activity by zymography. The results indicate reduction in MMP expression in transformed fibroblast cells after GSH and PDTC treatments and no effect after ascorbic acid treatment. Based on reverse zymography, we observed the level of tissue inhibitor of metalloproteinase (TIMP) at a decreased level in transformed cells. The effect of the reducing agent at the gene transcription was measured by estimating mRNA (Northern blot analysis) of MMP and of TIMP in the cells that were cultured in medium in the presence and absence of GSH. These results indicate that GSH induces MMP-2 and MMP-1 expression in normal HHF and that GSH reduces MMP-2 and MMP-1 in transformed fibroblast cells. After the treatment, the TIMP-2 level was repressed in normal HHF and TIMP-2 level increased in transformed fibroblast cells. These events are dependent on the nuclear transcription factor activity on the collagenase promoter in normal HHF cells. On the other hand, in polyoma transform fibroblast cells these events are not dependent on this collagenase promoter. These results suggest that oxidative environment induces normal HHF cell proliferation, and the reducing agent decreases normal HHF cell proliferation by inducing MMP and repressing TIMP gene transcription. In transformed cells reducing agents inhibit MMP expression and increase TIMP levels, which suggests a role of antioxidants in preventing tumorigenesis.

Antineoplastic Agents↗
PubMed1996

Disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran by rainbow trout (Oncorhynchus mykiss).

The disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran (TCDF) was investigated in rainbow trout (Oncorhynchus mykiss) in order to better understand the metabolic and physiological factors that modulate the fate of this extremely toxic compound in rainbow trout compared to other species. The fish were dosed orally with [3H]TCDF (1 microgram/kg); fish were terminated at 1-19 days for the determination of whole body half-life or at 0.3-28 days for determination of tissue distribution. Unassimilated TCDF (51.5% of the dose) was eliminated with a half-life of 0.84 days. The assimilated body burden of TCDF equivalents decreased with a half-life of 14.8 days (determined between 3 and 19 days). Trout muscle showed a relatively high capacity to accumulate and retain (unmetabolized) TCDF, accounting, at 3 days, for 32% of the body burden of TCDF equivalents (half-life in muscle, 15.2 days). Trout liver, on the other hand, showed a relatively low capacity to accumulate and metabolize TCDF. At 3 days, the concentrations of TCDF equivalents in liver and bile were, respectively, 0.37 ng/g liver (0.88% of the body burden) and 4.8 ng/ml bile. The data suggest that the relatively high affinity of lipid-rich trout muscle for TCDF limits the ability of the liver to accumulate and metabolize TCDF. The major TCDF metabolites found in trout liver and bile were, respectively, 4-OH-TCDF and TCDF-4-O-glucuronide.

Animals↗
PubMed1996

Disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran by channel catfish (Ictalurus punctatus).

The disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran (TCDF) was was investigated in channel catfish (Ictalurus punctatus) in order to better understand the metabolic and physiological factors that modulate the fate of this extremely toxic compound in channel catfish compared to other species. The fish were dosed orally with [3H]TCDF (1 microgram/kg); tissue were harvested at 3, 7, and 14 days for radioassay. The body burden of TCDF equivalents in catfish at 3 days was 0.36 microgram/kg, which was decreasing with a half-life of 3.6 days. Catfish muscle showed a relatively low capacity to accumulate and retain TCDF, accounting, at 3 days, for only 19.0% of the body burden of TCDF equivalents (half-life in muscle, 5.0 days). Catfish liver, on the other hand, showed a high capacity to accumulate and metabolize TCDF and to secrete TCDF metabolites into the bile. At 3 days, the concentrations of TCDF equivalents in liver and bile were, respectively, 5.7 ng/g liver (19% of the body burden) and 129 ng/ml bile. However, the concentration of TCDF equivalents in liver decreased with a half-life of 1.8 days to 0.04 ng/g (2.0% of the body burden) at 14 days. Thus, the capacity of catfish liver to retain TCDF decreased dramatically as the body burden decreased. The data suggest that the low affinity of lipid poor catfish muscle for TCDF may allow catfish liver to accumulate a concentration of TCDF sufficient to induce the metabolism of this compound by liver monooxygenases. The major TCDF metabolites found in catfish liver and bile were, respectively, 4-OH-TCDF and TCDF-4-O-glucuronide.

Animals↗
PubMed1996

Application of modified differential display technique for cloning and sequencing of the 3' region from three putative members of wheat HSP70 gene family.

We have modified the differential display technique to isolate 3' regions from different members of the wheat HSP70 gene family. An HSP70 gene family-specific degenerate primer was used as a 5' primer in place of the arbitrary primer used in the original technique. We cloned and sequenced three cDNA fragments that were differentially expressed in heat stressed wheat seedlings. Based on the high similarity between predicted translation products of these three sequences and known members of the HSP70 family from plants, these cDNAs were identified as members of the HSP70 gene family. Two of these members appeared distinct in the 3' non-coding region with only 48% identity. Therefore differential display could successfully be used to isolate 3' regions of different members of a multigene family in a relatively short period, even if the members had highly similar protein-coding regions.

Amino Acid Sequence↗
PubMed1996

Examination of two genetic polymorphisms within the renin-angiotensin system: no evidence for an association with nephropathy in IDDM.

Premature cardiovascular disease is common in insulin-dependent diabetic (IDDM) patients who develop diabetic nephropathy. Genetic polymorphism within the renin-angiotensin system has been implicated in the aetiology of a number of cardiovascular disorders; these loci are therefore candidate genes for susceptibility to diabetic renal disease. We have examined the angiotensin converting enzyme insertion/deletion polymorphism and angiotensinogen methionine 235 threonine polymorphism in a large cohort of Caucasian patients with IDDM and diabetic nephropathy. Patients were classified as having nephropathy by the presence of persistent dipstick positive proteinuria (in the absence of other causes), retinopathy and hypertension (n = 242). Three groups were examined for comparison: ethnically matched non-diabetic subjects (n = 187); a geographically defined cohort of newly diagnosed diabetic patients (n = 341); and IDDM patients with long duration of disease (> 15 years) and no evidence of overt nephropathy (n = 166). No significant difference was seen in distribution of angiotensin converting enzyme or angiotensinogen genotypes between IDDM patients with nephropathy and recently diagnosed diabetic subjects (p = 0.282 and 0.584, respectively), nor the long-duration non-nephropathy diabetic subjects (p = 0.701 and 0.190, respectively). We conclude that these genetic loci are unlikely to influence susceptibility to diabetic nephropathy in IDDM in the United Kingdom.

Adult↗
PubMed1996

Troglitazone, an insulin action enhancer, improves metabolic control in NIDDM patients. Troglitazone Study Group.

The effects of troglitazone, a novel thiazolidinedione, in non-insulin-dependent diabetic (NIDDM) patients were studied in a double-blind, parallel-group, placebo-controlled, dose-ranging trial. A total of 330 patients (63% male), mean age 57 years (range 39-72), with two fasting capillary blood glucose values > or = 7 and < or = 15 mmol/l (within 2.5 mmol/l of each other) were randomised to treatment with placebo or troglitazone at doses of 200, 400, 600 or 800 mg once daily, or 200 or 400 mg twice daily, for 12 weeks. Prior to the study, treatment had been with diet alone (38% patients) or with oral hypoglycaemic agents which were stopped 3-4 weeks before study treatment started. During treatment, HbA1c tended to rise in patients taking placebo (7.2-8.0%), but remained unchanged with all doses of troglitazone. After 12 weeks of treatment, HbA1c was significantly lower in the troglitazone-treated (mean 7.0-7.4%) compared to the placebo-treated (8.0%) patients (p = 0.055 to < 0.001), as was fasting serum glucose concentration (troglitazone, 9.3-11.0 mmol/l vs placebo, 12.9 mmol/l, p < 0.001). All doses of troglitazone were equally effective. Troglitazone also lowered fasting plasma insulin concentration, by 12-26% compared to placebo (p = 0.074 to < 0.001). Insulin sensitivity assessed by homeostasis model assessment (HOMA) was greater after 12 weeks of treatment in troglitazone-treated patients (troglitazone, 34.3-42.8% vs placebo, 29.9%, p < 0.05). In addition, serum triglyceride and non-esterified fatty acid concentrations were significantly lower and HDL cholesterol higher at troglitazone doses of 600 and 800 mg/day. LDL cholesterol increased at 400 and 600 mg doses only (from 4.3 and 3.9 mmol/l at baseline to 4.8 and 4.5 mmol/l, respectively at 12 weeks, p < 0.05), but not at doses of 800 mg once daily or 400 mg twice daily. LDL/HDL ratio did not change during treatment. All doses were well tolerated; incidence of adverse events in troglitazone-treated patients was no higher than in those treated with placebo. However, a tendency to reduced neutrophil counts was observed in patients taking the highest doses of troglitazone. We conclude that troglitazone is effective and well-tolerated and shows potential as a new therapeutic agent for the treatment of NIDDM.

Adult↗
PubMed1996

Compressive myelopathy in fluorosis: MRI.

We examined four patients with fluorosis, presenting with compressive myelopathy, by MRI, using spin-echo and fast low-angle shot sequences. Cord compression due to ossification of the posterior longitudinal ligament (PLL) and ligamentum flavum (LF) was demonstrated in one and ossification of only the LF in one. Marrow signal was observed in the PLL and LF in all the patients on all pulse sequences. In patients with compressive myelopathy secondary to ossification of PLL and/or LF, fluorosis should be considered as a possible cause, especially in endemic regions.

Adult↗
PubMed1996

Psychiatric sequelae of low birth weight at 6 years of age.

The study examined the association between low birth weight (LBW) (< or = 2,500 g) and attention deficit hyperactivity disorder (ADHD) in two socioeconomically disparate populations. LBW and normal birth weight (NBW) children from the 1983 to 1985 newborn lists of an urban and a suburban hospital in Southeast Michigan were randomly selected. A total of 823 children, 473 LBW and 350 NBW, participated. Data were gathered in 1990 to 1992, when the children were 6 to 7 years of age. The National Institute of Mental Health Diagnostic Interview Schedule for children-Parent version (DISC-P) was used to elicit information on DSM-III-R diagnoses of simple phobia, overanxious, separation anxiety, oppositional defiant, and ADHD. Teachers' ratings of behavior problems were obtained. LBW was associated with ADHD but not with childhood anxiety disorders or oppositional defiant disorder. The association was stronger in the urban than in the suburban population. Data from teachers' ratings revealed an association between LBW and attention problems. The prognostic significance of the observed psychopathology at 6 years of age requires follow-up assessment as the children mature.

Attention Deficit Disorder with Hyperactivity↗
PubMed1996

Evolutionary relationships of eukaryotic kingdoms.

The evolutionary relationships of four eukaryotic kingdoms--Animalia, Plantae, Fungi, and Protista--remain unclear. In particular, statistical support for the closeness of animals to fungi rather than to plants is lacking, and a preferred branching order of these and other eukaryotic lineages is still controversial even though molecular sequences from diverse eukaryotic taxa have been analyzed. We report a statistical analysis of 214 sequences of nuclear small-subunit ribosomal RNA (srRNA) gene undertaken to clarify these evolutionary relationships. We have considered the variability of substitution rates and the nonindependence of nucleotide substitution across sites in the srRNA gene in testing alternative hypotheses regarding the branching patterns of eukaryote phylogeny. We find that the rates of evolution among sites in the srRNA sequences vary substantially and are approximately gamma distributed with size and shape parameter equal to 0.76. Our results suggest that (1) the animals and true fungi are indeed closer to each other than to any other "crown" group in the eukaryote tree, (2) red algae are the closest relatives of animals, true fungi, and green plants, and (3) the heterokonts and alveolates probably evolved prior to the divergence of red algae and animal-fungus-green-plant lineages. Furthermore, our analyses indicate that the branching order of the eukaryotic lineages that diverged prior to the evolution of alveolates may be generally difficult to resolve with the srRNA sequence data.

Animals↗
PubMed1996

Problems in distinguishing spinal tuberculosis from neoplasia on MRI.

We reviewed MRI studies of 60 patients presenting with extradural compressive myeloradiculopathy secondary to vertebral disease to assess the imaging features which may help in differentiating tuberculous from neoplastic disease. Spin-echo T1-, proton density-and T2-weighted images were available for all patients and fast low-angle shot images with a low flip angle for 21 patients. Contrast-enhanced images were available for 28 patients. There were 41 patients with tuberculosis and 19 patients with neoplastic disease (metastases 11, lymphoma 6, plasmacytoma 1, and giant cell tumour 1). Discovertebral disease with or without involvement of the posterior arch was a feature not only of tuberculous spondylitis (30 patients) but also of metastases (6). The remaining 11 patients with tuberculosis had "atypical" involvement (vertebral body with or without posterior arch in 8 and posterior arch alone in 3) described as typical of neoplasms. This "typical" involvement was seen in metastases (5), lymphoma (6) and the 2 primary bone tumours. The presence of an abscess helped in differentiating tuberculosis from neoplasia in 22 of the 41 patients with tuberculosis and was absent in all with neoplasms. The presence of bone fragments in 16 patients (8 with and 8 without an abscess) was found to be specific for tuberculosis. In the absence of an abscess or bone fragments, image-guided biopsy is essential to establish the diagnosis.

Adenocarcinoma↗
PubMed1996

Characterization and transplantation of two neuronal cell lines with dopaminergic properties.

Immortalized rat mesencephalic cells (1RB3AN27) produced dopamine (DA) at a level that was higher than produced by undifferentiated or differentiated murine neuroblastoma cells (NBP2) in culture. Treatment of 1RB3AN27 and NBP2 cells with a cAMP stimulating agent increased tyrosine hydroxylase (TH) activity and the intensity of immunostaining for the DA transporter protein (DAT). 1RB3AN27 cells were labelled with primary antibodies to neuron specific enolase (NSE) and nestin and exhibited very little or no labeling with anti-glial fibrillary acidic protein (GFAP). 1RB3AN27 cells exhibited beta- and alpha-adrenoreceptors, and prostaglandin E1 receptors, all of which were linked to adenylate cyclase (AC). Dopamine receptor (D1) and cholinergic muscarinic receptors linked to AC were not detectable. The levels of PKC alpha and PKC beta isoforms were higher than those of PKC gamma and PKC delta in 1RB3AN27 cells. The 1RB3AN27 cells were more effective in reducing the rate of methamphetamine-induced turning in rats with unilateral 6-OHDA lesion of the nigrostriatal system than differentiated NBP2 cells. The grafted 1RB3AN27 were viable as determined by DiI labelling, but they did not divide and did not produce T-antigen protein; however, when these grafted cells were cultured in vitro, they resumed production of T-antigen and proliferated after the primary glia cells and neurons of host brain died due to maturation and subsequent degeneration. Examination of H&E stained sections of the grafted sites revealed no evidence of infiltration of inflammatory cells in the grafted area suggesting that these cells were not immunogenic. They also did not form tumors.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Transfection alters ion transport in MDCK cells.

In the course of an investigation into the effect of Tamm-Horsfall protein (THP) on ion transport, we performed stable transfection of THP into MDCK cells using the SV40 or the cytomegalovirus (CMV) promoter. As controls, we transfected MDCK cells with an "empty" plasmid containing SV40 or CMV promoter but without THP cDNA. In another set of controls, we subjected cells to transfection procedures without DNA (mock transfection). K influx was not altered in cells subjected to mock transfection procedures without DNA, but both ouabain sensitive (OS) and ouabain resistant (OR) components of K influx were diminished in cells transfected with THP cDNA using either SV40 or CMV promoter. However, K influx was also reduced in cells transfected with a control plasmid containing either the SV40 promoter alone, or the CMV promoter alone, without the THP cDNA. Thus, the transport alterations were caused by transfection and not by THP. The reduction in ouabain-sensitive K influx was accompanied by a proportional reduction in the abundance of Na-K pump units as assessed by [3H] ouabain binding. [3H] bumetanide binding, a measure of the number of functioning NaK2Cl cotransporter sites, was reduced pari passu with the reduction in bumetanide-sensitive K influx. These results highlight the possibility that alterations in properties of transfected cells may not be solely due to the presence of transfected protein, but the result of some process associated with transfection itself. Without appropriate controls to evaluate this possibility, results of transfection studies are subject to potentially faulty and misleading interpretation.

Cell Line↗
PubMed1996

Spinal segmental maldevelopment with a dermal sinus.

Segmental spinal dysgenesis is a rare form of spinal dysraphism. We report a case of segmental hypoplasia of the spinal cord extending from T6 to L1 vertebral levels, with a dorsal dermal sinus, diagnosed by spinal sonography and MRI and confirmed at surgery. The probable pathogenesis is suggested.

Diagnosis, Differential↗
PubMed1996

Serum levels of the TGF-beta receptor are increased in atherosclerosis.

Murine monoclonal antibody E9 recognises a transforming growth factor (TGF) beta receptor, which is expressed in increased amounts by activated endothelial cells. In order to examine the biological role of this molecule in atherosclerosis, we have measured levels of the TGF-beta receptor alongside those of two other endothelial cell products (von Willebrand factor and soluble E-selectin) in the serum of 55 patients with atherosclerosis (29 with ischaemic heart disease and 26 with peripheral vascular disease), and in a cohort of 26 age- and sex-matched asymptomatic controls. There were increased levels of the TGF-beta receptor (P = 0.0079) and von Willebrand factor (P = 0.0001), but not soluble E-selection in patients' serum relative to the controls. In multivariate analysis of the endothelial cell products against total cholesterol, high density lipoprotein cholesterol and low density lipoprotein cholesterol, triglycerides, systolic and diastolic blood pressures, age, sex and smoking, both the TGF-beta receptor and von Willebrand factor correlated with total cholesterol (Spearman's r = 0.37 and r = 0.35, respectively, both P < 0.001). Lack of a correlation with a coarse endothelial damage marker von Willebrand factor or soluble E-selectin (produced by immunologically stimulated endothelial cells) implies other mechanisms are responsible for increased levels of the TGF-beta receptor in serum of patients with atherosclerosis.

Aged↗
PubMed1996

A clinical, MRI and neurophysiological study of acute transverse myelitis.

There is paucity of studies correlating the MRI and evoked potential changes in acute transverse myelitis (ATM). We studied ten patients with ATM (age range 14-57 years; 8 men, 2 women) who were subjected to clinical, MRI and neurophysiological evaluation. The latter included median and tibial somatosensory evoked potentials (SEP), motor evoked potentials (MEP) to upper and lower limbs and concentric needle EMG. The outcome was defined on the basis of three month Barthel Index score. All the patients had pronounced lower limb and three had upper limb weakness. Magnetic resonance imaging scans revealed diffuse to hypointense lesions in T1, which became hyperintense in T2 in all except one patient, who had patchy hyperintense lesions in both T1 and T2 sequences suggesting haemorrhage. The signal changes extended at least three segments above the sensory level. Tibial SEP and central motor conduction time to tibialis anterior (CMCT-TA) were abnormal in nine patients each. Median SEP was normal in all, but CMCT to abductor digiti minimi (CMCT-ADM) was abnormal in four patients. The extent of MRI signal alterations and CMCT-TA correlated with the outcome. Seven patients had a poor outcome, in them MRI changes extended 10 spinal segments or more. In these patients, MEP on lumbar stimulation was either unrecordable or of low amplitude and extensive fibrillations were present in the lower limb muscles. From this study, we conclude that in ATM, extensive MRI changes, unrecordable MEP to lower limbs especially on lumbar stimulation and evidence of denervation in leg muscles seem to predict a poor outcome.

Acute Disease↗
PubMed1996

Effects of Mg2+ and denaturants on the unfolding pattern of DNA-T--a replication protein of E. coli.

Escherichia coli-DNA-T protein is a key component of a multiprotein complex called the primosome which is involved in the initiation of DNA replication. The thermal and urea induced unfolding transition of this protein in the presence and absence of Mg2+ was studied using circular dichroism (CD) and fluorescence spectroscopy as probes. Quenching of the intrinsic fluorescence of DNA-T was observed in the thermal unfolding while formation of a hyperfluorescent form of the protein was found in the urea induced unfolding process. The CD studies showed a monophasic transition curve for thermal unfolding in the presence and absence of Mg2+. Biphasic curves indicative of the formation of intermediates was observed in the urea induced unfolding. The results suggest that the pathways of unfolding of thermal- and urea-induced transitions are different. MgCl2, which affects the conformation of the protein and stabilises the secondary structure, also affects the unfolding pattern.

Bacterial Proteins↗
PubMed1996

Solution conformation of tuftsin.

Conformation of chemically synthesized tetrapeptide tuftsin, an important immunomodulator, with the sequence Thr-Lys-Pro-Arg-OH has been studied in aqueous solution as well as in a number of organic solvents viz. trifluoroethanol (TFE), methanol and dioxane by circular dichroism (CD) spectroscopy which reveals preferential occurrence of mixture of random coil and beta-turns, that has already been predicted as bioactive conformation of this peptide.

Circular Dichroism↗