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Biomedical subjects

S Kumar

Publications and source records attributed to S Kumar.

At least 595 records · Page 33Linked to original sources
PubMed2000

Plasma levels of soluble CD105 correlate with metastasis in patients with breast cancer.

CD105 (endoglin), a receptor for transforming growth factor (TGF) beta1 and beta3 in vascular endothelial cells, is highly up-regulated in blood vessels of tissues where neovascularisation occurs. It modulates endothelial-mesenchymal signalling and is essential for angiogenesis. Indeed, CD105 knock-out mice die from malvascularisation by 11.5 day p.c. In the present study CD105, TGFbeta1 and CD105/TGFbeta1 complexes were quantified in plasma samples from 77 healthy individuals and 92 patients with early stage breast cancer prior to any treatment. When compared with normal controls, both CD105 and CD105/TGFbeta1 complex levels were significantly elevated in breast cancer patients, whereas TGFbeta1 levels were lower in cancer patients. The most important finding to emerge was that CD105 levels were significantly increased in patients who developed distant metastasis compared with disease-free patients. While there was no significant difference between CD105 levels in controls compared to disease-free patients, it was significantly higher in patients with metastatic disease. Thus patients who had died following local relapse or distant metastases possessed the highest levels of CD105. Neither CD105/TGFbeta1 complex nor TGFbeta1 levels correlated with tumour progression. Our data indicate that CD105 might be a valuable novel angiogenic marker for identifying breast cancer patients who are at high risk of developing metastasis.

Adult↗
PubMed2000

Safety, tolerability and humoral immune responses after intramuscular administration of a malaria DNA vaccine to healthy adult volunteers.

DNA-based vaccines are considered to be potentially revolutionary due to their ease of production, low cost, long shelf life, lack of requirement for a cold chain and ability to induce good T-cell responses. Twenty healthy adult volunteers were enrolled in a Phase I safety and tolerability clinical study of a DNA vaccine encoding a malaria antigen. Volunteers received 3 intramuscular injections of one of four different dosages (20, 100, 500 and 2500 microg) of the Plasmodium falciparum circumsporozoite protein (PfCSP) plasmid DNA at monthly intervals and were followed for up to twelve months. Local reactogenicity and systemic symptoms were few and mild. There were no severe or serious adverse events, clinically significant biochemical or hematologic changes, or detectable anti-dsDNA antibodies. Despite induction of excellent CTL responses, intramuscular DNA vaccination via needle injection failed to induce detectable antigen-specific antibodies in any of the volunteers.

Adult↗
PubMed2000

Metabolic fate of glutamate and evaluation of flux through the 4-aminobutyrate (GABA) shunt in Aspergillus niger.

Accumulation of GABA and a concurrent block in the Krebs cycle suggest a functional GABA bypass in the acidogenic Aspergillus niger. Apart from the demonstration of enzyme machinery required, a direct measurement of flux through this glutamate decarboxylation loop was attempted. The distribution of carbon from glucose and glutamate was studied using A. niger mycelia grown on different media. The uptake and incorporation of (14)C label into organic acids and amino acids was followed by paper chromatography. Flow of label from glucose into citrate, glutamate and GABA increased in cells harvested at later stages of acidogenic growth. Very little citrate was derived from glutamate while ten times more label reached GABA from labeled glutamate. Radioactivity from L-[U-(14)C]glutamate and not from L-[1-(14)C]glutamate was recovered in GABA. This demonstrated that alpha-decarboxylation of L-glutamate was the source of GABA. Unless grown on GABA, A. niger mycelia did not take up externally supplied GABA. A direct measure of GABA shunt flux was thus not feasible. Therefore a combination of metabolite balance technique and the kinetic approach was applied to evaluate flux from glutamate to succinate in normal and acidogenic A. niger. The flux relative to TCA cycle was estimated by using uptake rate for radiolabeled glutamate, rate of accumulation of certain metabolites and the reactions of GABA metabolism. The analysis indicated that GABA shunt is operative in A. niger and its operation is enhanced during acidogenic growth of the fungus. This is the first report of an estimation of the flux through GABA shunt in a fungus.

Aspergillus niger↗
PubMed2000

Electrostatic strengths of salt bridges in thermophilic and mesophilic glutamate dehydrogenase monomers.

Here we seek to understand the higher frequency of occurrence of salt bridges in proteins from thermophiles as compared to their mesophile homologs. We focus on glutamate dehydrogenase, owing to the availability of high resolution thermophilic (from Pyrococcus furiosus) and mesophilic (from Clostridium symbiosum) protein structures, the large protein size and the large difference in melting temperatures. We investigate the location, statistics and electrostatic strengths of salt bridges and of their networks within corresponding monomers of the thermophilic and mesophilic enzymes. We find that many of the extra salt bridges which are present in the thermophilic glutamate dehydrogenase monomer but absent in the mesophilic enzyme, form around the active site of the protein. Furthermore, salt bridges in the thermostable glutamate dehydrogenase cluster within the hydrophobic folding units of the monomer, rather than between them. Computation of the electrostatic contribution of salt bridge energies by solving the Poisson equation in a continuum solvent medium, shows that the salt bridges in Pyrococcus furiosus glutamate dehydrogenase are highly stabilizing. In contrast, the salt bridges in the mesophilic Clostridium symbiosum glutamate dehydrogenase are only marginally stabilizing. This is largely the outcome of the difference in the protein environment around the salt bridges in the two proteins. The presence of a larger number of charges, and hence, of salt bridges contributes to an electrostatically more favorable protein energy term. Our results indicate that salt bridges and their networks may have an important role in resisting deformation/unfolding of the protein structure at high temperatures, particularly in critical regions such as around the active site.

Clostridium↗
PubMed2000

Rapid assessment and response to injecting drug use in Madras, south India.

HIV infection among injecting drug users (IDUs) is preventable, and in order to develop appropriate interventions, an assessment was carried out at Madras, South India using the Rapid Assessment and Response Guide on Injecting Drug Use developed by WHO. Data were collected with multiple methods from multiple sources using the principles of triangulation and induction. A total of 100 IDUs were interviewed. These interviews were complemented by focus groups and observations. A community advisory board ensured community ownership and participation. Findings showed that heroin, buprenorphine, diazepam and avil were the drugs most commonly injected. The use of pharmaceutical preparations as a 'cocktail' was also prevalent. Drug injectors interviewed were males, and most (81%) were from low-income groups living in slums. Direct (69%) as well as indirect sharing (94%) was common. Such unhygienic injecting practices, and the lack of access to sterile water, contribute to the high incidence of adverse health consequences. Compared with the buprenorphine injectors, heroin injectors were more likely to share injecting equipment (P=0.0022), inject more frequently (P=0.0013), have more drug using network members (P=0.0104), frequent 'shooting' locations (P=0.002), use the dealer's place to inject (P=0.0317), and face threats of arrest (P=0.0023). Many buprenorphine injectors managed their life without serious crises, and seemed to adopt a 'natural' harm reduction response. Sexual risk behaviour was prevalent among opioid users, and a history of commercial sex was associated with daily alcohol use (P=0.0221). The assessment led to an action plan which was presented and endorsed in an advocacy meeting by key stake-holders and decision-makers. The critical importance of implementing quality, accessible, community-oriented, and effective HIV interventions with the capacity to reach the majority of IDUs is discussed. Public health responses to injecting drug use must target changes among individuals at-risk, as well as in the community and risk environment.

Journal Article↗
PubMed2000

Photoalignment of liquid crystals by liquid crystals

We observed light-induced alignment of the nematic liquid crystal, 4, 4(')-n-pentylcyanobiphenyl (5CB), on a fused quartz. Irradiation of the adsorbed layer with polarized ultraviolet light produced homogeneous alignment in a 5CB-filled liquid crystal cell with the easy orientation axis perpendicular to the polarization direction. The measured anchoring energy increases with illumination up to 10(-4) erg/cm (2). Phase retardation and pretilt measurements confirmed near homogeneous alignment of the LC in a cell, while the polarization dependence of second harmonic generation suggested a near normal alignment of the adsorbed layer. We believe that light-induced rearrangement or phototransformation of the adsorbed layer causes the observed phenomenon.

Journal Article↗
PubMed2000

Debcl, a proapoptotic Bcl-2 homologue, is a component of the Drosophila melanogaster cell death machinery.

Bcl-2 family of proteins are key regulators of apoptosis. Both proapoptotic and antiapoptotic members of this family are found in mammalian cells, but no such proteins have been described in insects. Here, we report the identification and characterization of Debcl, the first Bcl-2 homologue in Drosophila melanogaster. Structurally, Debcl is similar to Bax-like proapoptotic Bcl-2 family members. Ectopic expression of Debcl in cultured cells and in transgenic flies causes apoptosis, which is inhibited by coexpression of the baculovirus caspase inhibitor P35, indicating that Debcl is a proapoptotic protein that functions in a caspase-dependent manner. debcl expression correlates with developmental cell death in specific Drosophila tissues. We also show that debcl genetically interacts with diap1 and dark, and that debcl-mediated apoptosis is not affected by gene dosage of rpr, hid, and grim. Biochemically, Debcl can interact with several mammalian and viral prosurvival Bcl-2 family members, but not with the proapoptotic members, suggesting that it may regulate apoptosis by antagonizing prosurvival Bcl-2 proteins. RNA interference studies indicate that Debcl is required for developmental apoptosis in Drosophila embryos. These results suggest that the main components of the mammalian apoptosis machinery are conserved in insects.

Amino Acid Sequence↗
PubMed2000

Tumour necrosis factor-alpha exerts dual effects on human adipose leptin synthesis and release.

The acute and chronic effects of tumour necrosis factor-alpha (TNF-alpha) on leptin production by human preadipocytes, differentiated preadipocytes, and mature adipocytes have been examined by competitive RT-PCR of leptin mRNA and by western blotting. In preadipocytes, secreted leptin was detectable after 5-day incubation in differentiation medium and this increased 4-fold by day 20. TNF-alpha blocked leptin synthesis during differentiation. In differentiated preadipocytes and mature adipocytes, TNF-alpha treatment resulted in time-dependent decreases in mRNA for leptin and glycerol-3-phosphate dehydrogenase (G3PD). In contrast, TNF-alpha (4-8-h treatment) resulted in a 4-fold increase in leptin release. This effect was lost at 24 h and leptin accumulation in culture medium was decreased 24-48 h after TNF-alpha addition. We conclude that TNF-alpha stimulates the release of preformed leptin from human mature adipocytes and existing differentiated preadipocytes, which may contribute to obesity/infection-linked hyperleptinemia, and that TNF-alpha inhibits leptin synthesis via inhibition of preadipocyte differentiation and induction of adipocyte dedifferentiation.

Adipocytes↗
PubMed2000

A family with autosomal dominant inherited dysmorphic small auricles, lip pits, and congenital conductive hearing impairment.

DESIGN: We examined 3 generations in a family for congenital conductive hearing impairment, dysmorphic small auricles, and lip pits. SETTING: Department of Otorhinolaryngology, University Hospital Nijmegen, Nijmegen, the Netherlands. RESULTS: Seven members of the family had bilateral dysmorphic auricles. Three subjects had either a pit or dimple in the lip. Two subjects had congenital conductive hearing impairment. CONCLUSION: Using gene linkage, we confirmed that these autosomal dominant inherited branchial anomalies present a new separate branchial arch syndrome.

Adolescent↗
PubMed2000

[8-(Diethylamino)octyl-3,4,5-trimethoxybenzoate, HCl], the inhibitor of intracellular calcium mobilization, blocked mitogen-induced T cell proliferation by interfering with the sustained phase of protein kinase C activation.

The physiological role of IP(3)-dependent Ca(2+) release in T cell activation was in question due to the contradictory findings that [8-(Diethylamino)octyl-3,4,5-trimethoxybenzoate, HCl] (TMB-8), an inhibitor of intracellular Ca(2+) mobilization, blocked T cell proliferation, curtailing specifically the level of released Ca(2+) did not affect T cell activation and T cell line lacking IP(3) receptor was defective in IL-2 production in response to TCR/CD3 ligand. In the present study we found that TMB-8 inhibited Concanavalin A (Con A)- but not PMA/Ionomycin-induced T cell proliferation in a reversible and dose-dependent manner. The kinetic study revealed that TMB-8 exerted the inhibitory effect at a very early step of T cell activation. The Ca(2+) ionophore ionomycin augmented instead of overcoming the inhibitory effect of TMB-8, although the same doses of ionomycin alone had no effect on Con A-induced T cell proliferation. PMA the metabolically stable, but not diacylglycerol (DAG) the metabolically labile, activator of protein Kinase C (PKC) completely overcome the antiproliferative effect of TMB-8. A specific DAG lipase inhibitor RHC80267 also overcome the effect of TMB-8. Taken together, these results showed that the process of Ca(2+) release through IP(3) receptor, not the released Ca(2+), is essential for the sustained phase of PKC activation during T cell proliferation.

Animals↗
PubMed2000

Stimulant-free preculture in heterologous serum-supplemented medium induces unresponsiveness of T cells to subsequent mitogenic stimulation.

Quite often freshly isolated lymphocytes are kept in culture before experimentation for 1 or more days without any stimulus. Most of the time, culture is supplemented with fetal bovine serum (FBS) which is heterologous to all species except bovine. In the present study, we found that freshly isolated murine T cells show a good proliferative response to concanavalin A (Con A) and phorbol ester (PMA)/ionomycin in FBS medium, without any detectable background proliferation. However, the cells kept in the same culture without any stimulus for prolonged period of time (referred to as preculture in this report) showed reduced response to Con A and PMA/ionomycin in a time-dependent manner. Almost a complete loss of response to Con A was observed within 1 day of preculture. However, loss of response to PMA/ionomycin was observed only after 2 days of preculture. Interestingly, similar preculture in autologous mouse serum-supplemented media did not cause any loss of the response to these mitogens. The loss of responsiveness of T cells during preculture in heterologous serum was irreversible. The heterologous serum-induced unresponsiveness of T cells to these mitogens was also prevented by adding Calphostin C, a specific protein kinase C (PKC) inhibitor, during preculture in heterologous serum. These results showed that prolonged stimulant-free preculture in heterologous serum induces irreversible unresponsiveness of T cells to mitogens through the down regulation of T cell receptor signaling pathway, which can be prevented by autologous serum or a PKC inhibitor.

Animals↗
PubMed2000

CKbeta-8 [CCL23], a novel CC chemokine, is chemotactic for human osteoclast precursors and is expressed in bone tissues.

We have previously demonstrated that a tartrate-resistant acid phosphatase (TRAP)-positive subpopulation of mononuclear cells isolated from collagenase digests of human osteoclastoma tissue exhibits an osteoclast phenotype and can be induced to resorb bone. Using these osteoclast precursors as a model system, we have assessed the chemotactic potential of 16 chemokines. Three CC chemokines, the recently described CKbeta-8, RANTES, and MIP-1alpha elicited significant chemotactic responses. In contrast, 10 other CC chemokines (MIP-1beta, MCP-1, MCP-2, MCP-3, MCP-4, HCC-1, eotaxin-2, PARC, SLC, ELC) and 3 CXC chemokines (IL-8, GROalpha, SDF-1) were inactive. None of these chemokines showed any chemotactic activity for either primary osteoblasts derived from human bone explants or the osteoblastic MG-63 cell line. The identity of the osteoclast receptor that mediates the chemotactic response remains to be established. However, all three active chemokines have been reported to bind to CCR1 and cross-desensitization studies demonstrate that RANTES and MIP-1alpha can partially inhibit the chemotactic response elicited by CKbeta-8. CKbeta-8, the most potent of the active CC chemokines (EC(max) 0.1-0.3 nM), was further characterized with regard to expression in human bone and cartilage. Although expression is not restricted to these tissues, CKbeta-8 mRNA was shown to be highly expressed in osteoblasts and chondrocytes in human fetal bone by in situ hybridization. In addition, CKbeta-8 protein was shown to be present in human osteophytic tissue by immunolocalization. These observations suggest that CKbeta-8, and perhaps other chemokines, may play a role in the recruitment of osteoclast precursors to sites of bone resorption.

Bone Neoplasms↗
PubMed2000

Villoglandular papillary adenocarcinoma of the cervix: case report.

The incidence of cervical adenocarcinoma is on the rise over the last several decades. It generally carries a worse prognosis than squamous carcinoma. Villoglandular papillary adenocarcinoma (VGA) of the cervix has been identified as a distinct subset of cervical adenocarcinoma that occurs in young women and supposedly carries an excellent prognosis. We report a case of adenocarcinoma of the cervix in a young woman that had classical histological features of VGA but at operation showed presence of tumor cells in the peritoneal wash. A review of world literature on the 56 cases reported so far is presented where occasional cases showing disease spread have been reported, suggesting caution in the management and follow-up of this clinicopathologic entity.

Adenocarcinoma, Papillary↗
PubMed2000

A simple microbiological assay for the stereospecific differentiation of alpha and beta isomers of arteether.

A new rapid bioassay has been developed which can precisely differentiate between stereospecific alpha and beta isomers of the antimalarial drug arteether. This method was developed through the disc diffusion bioactivity tests wherein semisynthetically produced alpha arteether was able to inhibit the growth of E. coli strains which are defective in DNA gyrase enzyme. The wild type E. coli with intact DNA gyrase did not show this sensitivity to alpha arteether. The beta isomer of arteether was, however, ineffective against both the mutant and wild type strains. Direct experimental proof of gyrase involvement was obtained through mobilization of gyr genes by transformation of E. coli gyr- mutant strains with wild type gyrA clone pMK90 (carried on the thermo-inducible lambda Col E1 vector). This resulted in alpha arteether resistant and nalidixic acid sensitive phenotype clearly demonstrating the use of gyrA mutant strains in differentiating alpha and beta isomers of arteether by this simple bioassay.

Antimalarials↗
PubMed2000

Pharmacokinetics and renal excretion of diphenhydramine and its metabolites, diphenylmethoxyacetic acid and diphenhydramine-N-oxide, in developing lambs.

The developmental disposition of diphenhydramine (DPHM) and its metabolites, diphenylmethoxyacetic acid (DPMA) and DPHM-N-oxide (DPHMNO), was investigated in postnatal lambs. Lambs received a DPHM intravenous (iv) bolus 15 days (Group A; n = 5) or 2 months (Group B; n = 6) after birth. Total body clearance of DPHM in postnatal lambs (Group A = 138.7 +/- 80.5 mL/min/kg; Group B = 165.7 +/- 51.3 mL/min/kg) was similar to the nonplacental clearance values (i.e., the component of fetal total body clearance that is not due to elimination via the placenta) estimated for fetal lamb (116.3 +/- 49. 6 mL/min/kg), and significantly greater than estimates in adult sheep (38.5 +/- 12.3 mL/min/kg). In addition, Group A DPHM renal clearance (CL(r), >1.80 +/- 1.24 mL/min/kg) was similar to that of the fetus (2.06 +/- 0.24 mL/min/kg), and significantly greater than that for Group B (0.26 +/- 0.17 mL/min/kg) and the adult (0.012 +/- 0.005 mL/min/kg). In contrast, similar to the fetal situation, postnatal DPMA CL(r) (Group A = 0.02 +/- 0.02 mL/min/kg; Group B = 0.05 +/- 0.01 mL/min/kg) was significantly less than adult values (0. 53 +/- 0.19 mL/min/kg). Because DPMA is not sequentially metabolized in sheep, the lower CL(r) in postnatal lambs results in longer apparent elimination half-lives of this metabolite (Group A = 90.4 +/- 32.2 h; Group B = 13.13 +/- 11.0 h) compared with that in the adult (2.9 +/- 1.6 h). No age-related difference in DPHMNO CL(R) was observed. Alterations in the CL(r) of DPHM and DPMA are likely related to differences in the rate of development of mechanisms (i.e. , tubular secretion and reabsorption and glomerular filtration rate) involved in the urinary drug excretion of organic acids and bases.

Acetates↗
PubMed2000

Human bone marrow stromal cell: coexpression of markers specific for multiple mesenchymal cell lineages.

The role of hematopoietic stem cells in blood cell development is reasonably understood, whereas the identity and the function of bone marrow stromal cells are much less clear. Using stromal cells in bone marrow cultures of the Dexter type, a favorite medium for the study of hematopoiesis, we show that stromal cells actually represent a unique cell type. Conventional wisdom has held that stromal cells in Dexter cultures comprise a mixture of macrophages, hematopoietic cells, adipocytes, osteoblasts, fibroblasts, muscle cells, and endothelial cells. Our findings demonstrate that Dexter cultures consist of three cell types: macrophages ( approximately 35%), hematopoietic cells ( approximately 5%), and nonhematopoietic cells ( approximately 60%). We have purified the nonhematopoietic cells free of macrophages and hematopoietic cells to produce compelling evidence that they in fact represent a single cell type (multidifferentiated mesenchymal progenitor cell, MPC) which coexpresses genes specific for various mesenchymal cell lineages including adipocytes, osteoblasts, fibroblasts, and muscle cells. We further show that these multi- or pluridifferentiated MPCs are capable of supporting hematopoiesis by demonstrating the expression of several hematopoietic growth factors and extracellular matrix receptors including G-CSF, SCF, VCAM-1, ICAM-1, and ALCAM. Since the MPCs can be easily purified to near homogeneity (95%), they can be of value in enhancing engraftment of hematopoietic stem cells. Also, this new understanding of bone marrow stromal cells as "one cell with many different faces" promises to advance our knowledge of regulatory cellular interactions within bone marrow.

Bone Marrow Cells↗
PubMed2000

Positive correlation between menthol content and in vitro menthol tolerance in Mentha arvensis L. cultivars.

Menthol is a highly valued monoterpene produced by Japanese mint (Mentha arvensis) as a natural product with wide applications in cosmetics, confectionery, flavours, beverages and therapeutics. Selection of high menthol yielding genotypes is therefore the ultimate objective of all genetic improvement programmes in Mentha arvensis. A positive correlation was observed in the present study between menthol content in oils of evaluated genotypes and the level of tolerance to externally supplied menthol of explants of these genotypes in culture medium. The easy use of this relationship as a selectable biochemical marker opens the practical applicability of large scale in vitro screening of the germplasm, clones and breeders' material for selection of elite genotypes.

Drug Resistance↗