Search PubMed⌕ Search

Biomedical subjects

S Sarkar

Publications and source records attributed to S Sarkar.

At least 109 records · Page 6Linked to original sources
PubMed2000

HIV-1 subtypes in injecting drug users & their non-injecting wives in Manipur, India.

The presence of HIV-1 antibodies was determined among the injecting drug users (IDUs) and their non-injecting wives. A total of 233 (72%) were found to be HIV-1 seropositive among the 322 subjects recruited in this study between August, 1996 and September, 1997. The distribution of HIV-1 subtypes among the injecting drug users (IDUs) and their wives was determined using peptide enzyme immunoassay (EIA). Sexual transmission of HIV-1 occurred frequently (45%) from HIV-1 infected IDUs to their spouses. The majority of the subjects (167/233) were infected with subtype C followed by subtype Thai B (29/233). Subtype C was the most common among both IDUs (78%) and their wives (57%), followed by subtype Thai B (12% and 13% respectively). The distribution of subtypes was significantly different between IDUs and their wives with a lower percentage of subtype C and higher percentage of subtype D in the infected wives (P < 0.03). Discordance for subtypes transmitted from IDUs to their wives suggests the occurrence of dual and/or recombinant infection in the IDUs.

Female↗
PubMed2000

Surveillance for polio eradication: current status and lessons learnt--India, 1999.

With the launch of the Universal Immunisation Programme in India in 1985, childhood immunisation was provided to children in all districts of the country in a phased manner by 1990. Surveillance for vaccine preventable diseases (VPD) including polio was started at the same time with monthly reporting from the districts to the Ministry of Health and Family Welfare (MOHFW), Government of India (GOI). In 1995, the Pulse Polio Immunisation (PPI) campaign was launched with the objective of polio eradication. Prior to 1997, surveillance for polio was directed at finding clinical polio cases by passive reporting from health facilities. There was no active surveillance for all cases of acute flaccid paralysis (AFP). In 1996, a scheme for the surveillance of AFP was drawn up. With the support of the Danish and US governments and Rotary International, 59 surveillance medical officers (SMOs) were hired, trained, and posted throughout the country in October 1997 to establish active surveillance of AFP. The number of SMOs was increased to 108 in August 1999. The SMOs along with their government counterparts established 10,069 reporting units nationwide by the end of November 1999 reporting weekly the occurrence of AFP cases to the district, state, and national levels; timely case investigation and collection of stool specimens from AFP cases; linkages to support the polio laboratory network; and extensive training of government counterparts. Data reported to the national level is analysed and put on an internet website which is updated every two weeks. Annualised rates of reported non-polio AFP have increased from 0.22 per 100,000 children aged < 15 years in 1997 to 1.57 in 1999. The number of polio cases associated with isolation of wild poliovirus decreased from 1404 in the third trimester of 1998 to 664 in the third trimester of 1999, yet widespread transmission of wild polioviruses persists throughout the country.

Adolescent↗
PubMed2000

Effect of black tea on teeth.

Dental caries is the prime cause of premature loss of teeth in children. Tea contains high percentage of fluoride along with polyphenolic constituents which act on GTF of S. mutans in plaque synthesis. Combination of fluoride and polyphenolic constituents inhibit caries activity.

Adsorption↗
PubMed1999

Nuclear tRNA aminoacylation and its role in nuclear export of endogenous tRNAs in Saccharomyces cerevisiae.

Nuclear tRNA aminoacylation was proposed to provide a proofreading step in Xenopus oocytes, ensuring nuclear export of functional tRNAs [Lund, E. & Dahlberg, J. E. (1998) Science 282, 2082-2085]. Herein, it is documented that tRNA aminoacylation also occurs in yeast nuclei and is important for tRNA export. We propose that tRNA aminoacylation functions in one of at least two parallel paths of tRNA export in yeast. Alteration of one aminoacyl-tRNA synthetase affects export of only cognate tRNA, whereas alterations of two other aminoacyl-tRNA synthetases affect export of both cognate and noncognate tRNAs. Saturation of tRNA export pathway is a possible explanation of this phenomenon.

Amino Acyl-tRNA Synthetases↗
PubMed1999

Archimedean Synthesis and Magic Numbers: "Sizing" Giant Molybdenum-Oxide-Based Molecular Spheres of the Keplerate Type.

Pythagorean harmony can be found in the spherical polyoxometalate clusters described here (see illustration for an example of a structure), since there are interesting relationships between the so-called magic numbers (12, 32, 42, 72, 132) relevant for spherical viruses and the number of the building blocks in the cluster. The size of these Keplerate clusters can be tailored by varying the type of connections between the pentagons by means of different spacers.

Journal Article↗
PubMed1999

Role of estradiol receptor-alpha in differential expression of 2,3,7, 8-tetrachlorodibenzo-p-dioxin-inducible genes in the RL95-2 and KLE human endometrial cancer cell lines.

The present study was conducted to investigate the mechanism of the response of human uterine endometrial carcinoma cells, RL95-2 and KLE, to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). RL95-2 cells were highly responsive to TCDD in terms of cytochrome P4501A1 (CYP1A1), cytochrome P4501B1 (CYP1B1), and plasminogen activator inhibitor-2 (PAI-2), whereas KLE cells showed little stimulatory effects only at high doses. Neither showed any growth inhibition upon exposure to TCDD. KLE cells expressed higher levels of aryl hydrocarbon receptor (AhR) than RL95-2 and gel mobility shift assay also identified more liganded AhR-ARNT complex bound to xenobiotic response elements (XRE). TCDD had no downregulatory effects on the expression of either AhR or the estradiol receptor (ER). Though both cell types expressed ER-alpha almost equally, immunofluorescence demonstrated a defect in its nuclear translocation in KLE cells where ER-alpha was mainly cytoplasmic and estradiol-17beta (E(2)) was unable to translocate it to the nucleus. However, both cells were nonresponsive to E(2) in terms of transcriptional activation and transient expression of normal ER-alpha restored the E(2) responsiveness. Transient expression of ER-alpha in KLE cells also restored its responsiveness to TCDD on transcriptional activation. Collectively, these results indicate that ER-alpha acts as a positive modulator in regulation of the TCDD-inducible genes.

Base Sequence↗
PubMed1999

Focal adhesions.

Explore the source record for details and available documents.

Animals↗
PubMed1999

p16/pRb pathway alterations are required for bypassing senescence in human prostate epithelial cells.

The cell cycle regulatory genes p16/CDKN2 and RB are frequently deleted in prostate cancers. In this study, we examined the role of alterations in p16 and pRb during growth, senescence, and immortalization in vitro of human prostate epithelial cells (HPECs). HPECs are established from normal prostate tissues and cultured on collagen-coated dishes. Our results show that p16 is reproducibly elevated at senescence in HPECs. HPECs are immortalized using human papilloma virus 16 E6 and/or E7 as molecular tools to inactivate p53 and/or pRb, respectively. Immortalization occurs infrequently in this system and only after a latent period during which additional genetic/epigenetic changes are thought to occur. Notably, all of the E6-immortalized HPEC lines but none of the E7 lines show inactivation of p16/CDKN2 (by deletion, methylation, or mutation) in association with immortalization. In contrast, E7 lines, in which pRb function is abrogated by E7 binding, retain the high levels of p16 observed at senescence. Thus, all lines show either a p16 or pRb inactivation. Analysis of six independent lines from metastatic prostate cancers reveals a similar loss of either p16 or pRb. Comparative genomic hybridization of HPECs shows that gains of chromosomes 5q, 8q, and 20 are nonrandomly associated with bypassing senescence (probability = 0.95). These results suggest that high levels of the cyclin-dependent kinase inhibitor p16 mediate senescence G1 arrest in HPECs and that bypassing this block by a p16/pRb pathway alteration is required for immortalization in vitro and possibly tumorigenesis in vivo. Our results further indicate that inactivation of the p16/pRb pathway alone is not sufficient to immortalize HPECs and that additional genetic alterations are required for this process.

Aged↗
PubMed1999

Description of a versatile peroxidase involved in the natural degradation of lignin that has both manganese peroxidase and lignin peroxidase substrate interaction sites.

Two major peroxidases are secreted by the fungus Pleurotus eryngii in lignocellulose cultures. One is similar to Phanerochaete chrysosporium manganese-dependent peroxidase. The second protein (PS1), although catalyzing the oxidation of Mn2+ to Mn3+ by H2O2, differs from the above enzymes by its manganese-independent activity enabling it to oxidize substituted phenols and synthetic dyes, as well as the lignin peroxidase (LiP) substrate veratryl alcohol. This is by a mechanism similar to that reported for LiP, as evidenced by p-dimethoxybenzene oxidation yielding benzoquinone. The apparent kinetic constants showed high activity on Mn2+, but methoxyhydroquinone was the natural substrate with the highest enzyme affinity (this and other phenolic substrates are not efficiently oxidized by the P. chrysosporium peroxidases). A three-dimensional model was built using crystal models from four fungal peroxidase as templates. The model suggests high structural affinity of this versatile peroxidase with LiP but shows a putative Mn2+ binding site near the internal heme propionate, involving Glu36, Glu40, and Asp181. A specific substrate interaction site for Mn2+ is supported by kinetic data showing noncompetitive inhibition with other peroxidase substrates. Moreover, residues reported as involved in LiP interaction with veratryl alcohol and other aromatic substrates are present in peroxidase PS1 such as His82 at the heme-channel opening, which is remarkably similar to that of P. chrysosporium LiP, and Trp170 at the protein surface. These residues could be involved in two different hypothetical long range electron transfer pathways from substrate (His82-Ala83-Asn84-His47-heme and Trp170-Leu171-heme) similar to those postulated for LiP.

Amino Acid Sequence↗
PubMed1999

Protein kinase A linked phosphorylation mediates triiodothyronine induced actin gene expression in developing brain.

In the developing rat cerebra, triiodothyronine (T3) stimulates actin mRNA by acting predominantly at the level of transcription whereas tubulin mRNA is enhanced primarily by post-transcriptional regulation. We report here that in primary cultures of rat cerebra, the T3-induced actin gene expression is mediated by phosphorylation events. Inhibition of protein kinase A (PKA), but not of protein kinase C (PKC) or tyrosine kinase, totally blocked the induction of actin mRNA by T3. Under identical conditions, induction of tubulin mRNA by T3 was virtually unaffected by all the inhibitors. Activators of PKA, but not of PKC, potentiated the T3-induced actin gene expression, both at mRNA and protein level, by about 2-fold. In the absence of T3, neither the inhibitor nor the activator of PKA had any significant effect on this induction. The involvement of PKA in mediating the induction of actin mRNA by T3 was confirmed by transfecting primary cultures of rat cerebra with an expression vector encoding the protein kinase A inhibitor which totally abolished the induction. T3 is shown to enhance the phosphorylation of the thyroid hormone receptor, TRalpha, by about 2-fold but the level of phosphorylation of TRbeta remained virtually unaffected.

Actins↗
PubMed1999

Cross-talk between 2,3,7,8-tetrachlorodibenzo-p-dioxin and testosterone signal transduction pathways in LNCaP prostate cancer cells.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related compounds modulate various endocrine functions by enhancing ligand metabolism, altering hormone synthesis, down regulating receptor levels, and interfering with gene transcription. In the present study, we investigated the effects of TCDD on testosterone signal transduction pathways and vice versa in the androgen receptor (AR) positive LNCaP prostate cancer cell line. TCDD induced CYP1A1 mRNA and related enzyme activity in these cells, with dose and time-dependence. Both normal and testosterone-stimulated cell growth was inhibited by TCDD. The expression levels of the aryl hydrocarbon receptor (AhR), the aryl hydrocarbon receptor nuclear translocator (ARNT), and AR were not affected by exposure to TCDD at a dose of 10 nM for a 24 hr time period. Testosterone treatment dose-dependently inhibited the TCDD-induced CYP1A1 mRNA accumulation and related enzyme activity. Reciprocally, TCDD also dose-dependently inhibited testosterone-dependent transcriptional activity and testosterone-regulated prostate specific antigen (PSA) expression. Taken together, these results demonstrate antiandrogenic functions of TCDD and a specific ligand-induced bilateral transcriptional interference between TCDD and testosterone mediated signal transduction pathways.

Aryl Hydrocarbon Receptor Nuclear Translocator↗
PubMed1999

Activation of integrin-beta3-associated syk in platelets.

Published data suggest that the tyrosine kinase syk participates in platelet signalling through the integrin alphaIIbbeta3. Our data show an association of syk and integrin beta3 in immunoprecipitates from unstimulated and stimulated platelets. We detected syk in anti-beta3 precipitates and, conversely, beta3 in anti-syk precipitates. In vitro kinase assays with anti-beta3 precipitates demonstrated that syk activity was enhanced in ADP-stimulated platelets.

Antigens, CD↗
PubMed1999

Applications of high-resolution echoplanar spectroscopic imaging for structural imaging.

Echoplanar spectroscopic imaging (EPSI) was introduced as a fast alternative for spectroscopic imaging and has been recently implemented on clinical scanners. With further advances in gradient hardware and processing strategies, EPSI can be used to obtain spectroscopic images whose spatial resolution parallels that of conventional anatomic images within clinically acceptable acquisition time. The present work demonstrates that high-resolution EPSI can be used to derive structural images for applications in which spectroscopic information is beneficial. These applications are chemical shift (fat-water) imaging, narrow bandwidth imaging, and T2* mapping. In this paper, the EPSI sequence design and processing strategies are detailed and experimental results in normal volunteers are presented to illustrate the potential of using EPSI in imaging anatomic structures.

Adipose Tissue↗
PubMed1999

Beta-endorphin-like immunoreactivity in the forebrain and pituitary of the teleost Clarias batrachus (Linn.).

The organization of beta-endorphin-like immunoreactivity in the olfactory system, forebrain, and pituitary of the teleost Clarias batrachus was investigated. Immunoreactivity was prominently seen in the sensory neurons and basal cells in the olfactory epithelium and in some cells in the periphery and center (granule cells) of the olfactory bulb. Immunoreactive fibers in the olfactory nerve enter the olfactory nerve layer of the olfactory bulb and branch profusely to form tufts organized as spherical neuropils in the glomerular layer. While fascicles of immunoreactive fibers were seen in the medial olfactory tracts, the lateral olfactory tracts showed individual immunoreactive fibers. Immunoreactive fibers in the medial olfactory tract extend into the telencephalon and form terminal fields in discrete telencephalic and preoptic areas; some immunoreactive fibers decussate in the anterior commissure, while others pass into the thalamus. While neurons of the nucleus lateralis tuberis revealed weak immunoreactivity, densely staining somata were seen at discrete sites along the wall of the third ventricle. Although a large population of immunoreactive cells was seen in the pars intermedia of the pituitary gland, few were seen in the rostral pars distalis and proximal pars distalis; immunoreactive fibers were seen throughout the pituitary gland.

Animals↗
PubMed1999

Treatment of postmenopausal women with osteoporosis or low bone density with raloxifene. Raloxifene Study Group.

Raloxifene, a selective estrogen receptor modulator (SERM), has been shown to improved bone mineral density (BMD) and serum lipid profiles in healthy postmenopausal women. The objective of this study was to examine the effects of raloxifene on BMD, biochemical markers of bone metabolism and serum lipids in postmenopausal women with low bone density or osteoporosis. This Phase II, multicenter, 24-month, double-masked study assessed the efficacy and safety of raloxifene in 129 postmenopausal women (mean age +/- SD: 60.2 +/- 6.7 years) with osteoporosis or low bone density (baseline mean lumbar spine BMD T-score: -2.8). Women were randomly assigned to one of three treatment groups: placebo, 60 mg/day raloxifene-HCl (RLX 60) or 150 mg/day raloxifene-HCL (RLX 150) and concomitantly received 1000 mg/day calcium and 300 U/day vitamin D3. At 24 months, BMD was significantly increased in the lumbar spine (+3.2%), femoral neck (+2.1%), trochanter (+2.7%) and total hip (+1.6%) in the RLX 60 group compared with the placebo group (p < 0.05). The RLX 150 group had increases in BMD similar to those observed with RLX 60. A greater percentage of raloxifene-treated patients, compared with those receiving placebo, had increased BMD (p < 0.05). Serum bone-specific alkaline phosphatase activity, serum osteocalcin, and urinary type I collagen:creatinine ratio were significantly decreased in the RLX-treated groups, compared with the placebo group (p < 0.01). RLX 60 treatment significantly decreased serum levels of triglycerides, and total- and LDL-cholesterol levels (p < 0.01). The rates of patient discontinuation and adverse events were not significantly different among groups. In this study, raloxifene increased bone density, decreased bone turnover, and improved the serum lipid profile with minimal adverse events, and may be a safe and effective treatment for postmenopausal women with osteoporosis or low bone density.

Aged↗
PubMed1999

Tolerance of large exchange volumes by peritoneal dialysis patients.

Improving clearances on peritoneal dialysis involves either more exchanges, greater fill volume, or both. An increase in the number of exchanges is inconvenient, resulting in noncompliance. Therefore, the best option is to increase the exchange volumes; however, patients are often reluctant for fear of discomfort. We tested the tolerance of 20 patients blinded to randomly sequenced volumes of 2, 2.5, and 3 L, performed incenter by the dialysis nurse. Each patient underwent one to three exchanges with each volume. At the end of a 4-hour dwell, the patient scored discomfort and estimated the infused volume. Only one study exchange was performed each day; the rest of the time, the patient continued his or her usual prescription. Fifteen of the patients (75%) were not able to identify the exchange volumes. Four of the five patients who determined the correct exchange volume for 67% to 78% of the exchanges (P < 0.04 compared with 33% expected by chance) had a body surface area greater than 1.75 m2. Of 123 exchanges, 84% were associated with no discomfort, 10% with mild discomfort, and 6% with moderate discomfort. Patients were not more likely to have discomfort with 3-L compared with lower fill volumes. Peritoneal clearances of creatinine (6.1 v 6.6 v 7.7 mL/min/1.73 m2) and urea nitrogen (7.3 v 8.6 v 9.5 mL/min) were progressively greater with increasing exchange volumes (P < 0.001). We conclude that the majority of small as well as large patients will tolerate 2.5- and 3-L exchange volumes. If encouraged to do so, many patients could tolerate greater exchange volumes than they are presently using. Exchange volumes should be readily increased as residual renal function declines.

Adult↗