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Biomedical subjects

S Gupta

Publications and source records attributed to S Gupta.

At least 793 records · Page 44Linked to original sources
PubMed1996

Age-related changes in the ovalbumin gene of the Japanese quail.

Northern hybridization studies showed that the level of ovalbumin mRNA decreases in the oviduct of the Japanese quail after adulthood. In order to find out if this is due to changes in the conformation of the chromatin containing the promoter region of the gene, nuclei of the oviduct of young, adult and old birds were digested by DNaseI and micrococcal nuclease (MNase). Southern hybridization with the labelled promoter showed that this region is less sensitive to the two enzymes in the old birds. Both the endonucleases recognized the same hypersensitive sites. The results indicate that the chromatin containing the promoter is present in an open conformation in adult birds. Gel mobility shift assay using a 20-mer dsDNA containing the CAAT-box and nuclear extract of oviduct shows the presence of trans-acting factors that bind to this region. The levels of these factors are lower in old birds. This may be the reason for the lower expression of the gene in old birds.

Aging↗
PubMed1996

Selective interaction of JNK protein kinase isoforms with transcription factors.

The JNK protein kinase is a member of the MAP kinase group that is activated in response to dual phosphorylation on threonine and tyrosine. Ten JNK isoforms were identified in human brain by molecular cloning. These protein kinases correspond to alternatively spliced isoforms derived from the JNK1, JNK2 and JNK3 genes. The protein kinase activity of these JNK isoforms was measured using the transcription factors ATF2, Elk-1 and members of the Jun family as substrates. Treatment of cells with interleukin-1 (IL-1) caused activation of the JNK isoforms. This activation was blocked by expression of the MAP kinase phosphatase MKP-1. Comparison of the binding activity of the JNK isoforms demonstrated that the JNK proteins differ in their interaction with ATF2, Elk-1 and Jun transcription factors. Individual members of the JNK group may therefore selectively target specific transcription factors in vivo.

Activating Transcription Factor 2↗
PubMed1996

Modulation of vitellogenin II gene by estradiol and progesterone in the Japanese quail.

Estrogen and progesterone receptors are reported to functionally cooperate in gene activation if their cognate binding sites are close to one another in the gene. Our studies show that the expression of the vitellogenin (VTG) gene is induced by estradiol alone or along with progesterone. Progesterone alone inhibits the expression completely. Methylation status of the VTG gene remains unaltered by steroid hormones. Gel mobility shift assay shows that qualitative and quantitative changes occur in the trans-acting factor(s) that bind to estradiol and progesterone responsive elements (ERE and PRE) after administration of these steroid hormones. We, therefore, conclude that the interaction of trans-acting factors that bind to ERE and PRE play a role in the regulation of VTG gene expression.

Animals↗
PubMed1996

A stereospecific myo-inositol/D-chiro-inositol transporter in HepG2 liver cells. Identification with D-chiro-[3-3H]inositol.

D-chiro-Inositol is an epimer of myo-inositol that is found in certain mammalian glycosylphosphatidylinositol protein anchors and inositol phosphoglycans possessing insulin-like bioactivity. In order to generate a probe for metabolic studies, D-chiro-[3-3H]inositol was synthesized by selective reduction of D-chiro-3-inosose at pH 6.5 with sodium borotritide. D-chiro-[3-3H]Inositol was taken up by HepG2 human liver cells through a saturable and stereospecific pathway in which D-chiro-inositol and myo-inositol competed equally but L-chiro-inositol was not recognized. Dd-Glucose, but not L-glucose, competed for D-chiro-[3-3H]inositol uptake over glucose concentrations of 4-28 mM. Maximum transport capacity was 717 pmol/mg cell protein/3 h with a Km value of 348 microM. Uptake was reduced by 76% when sodium was eliminated from the medium and by 94% when the experiment was performed at 0 degrees C. The new myo/D-chiro-inositol transporter is distinct from the sodium-myo-inositol co-transporter found in many tissues and accounts for all of the saturable D-chiro-inositol uptake and for a portion of the saturable low affinity myo-inositol uptake in HepG2 cells. It may allow D-chiro-inositol to be used by cells in the presence of a relatively large amount of competing myo-inositol.

Binding, Competitive↗
PubMed1996

Expression of P-glycoprotein, encoded by MDR 1 gene, a metabolically active efflux pump in murine mast cells.

Mast cell line (MC/9) derived from normal murine liver was examined for the expression of P-glycoprotein (P-gp) at the level of protein with C-219 and JSB-1 monoclonal antibodies, using flow cytometry and Western blot, and at the level of mRNA by the reverse transcriptase-polymerase chain reaction. The function of P-gp was analyzed by the accumulation and efflux of rhodamine 123 (Rh123) in the presence or absence of cyclosporin A (CSA) and a non-immunosuppressive analog of CSA (CSA-1). P-gp both at the protein and mRNA levels was expressed in mast cells. Intracellular accumulation of Rh123, in the presence of CSA and CSA-1 was significantly greater than in their absence. Furthermore, both CSA and CSA-1 inhibited Rh123 efflux from mast cells. These data suggest the presence of a functionally active P-gp in mast cells. A possible physiologic role for P-gp in the secretion of certain mediators/cytokines from mast cells is suggested.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Phosphorylated interferon-alpha receptor 1 subunit (IFNaR1) acts as a docking site for the latent form of the 113 kDa STAT2 protein.

Interferon-alpha (IFN alpha) induces rapid tyrosine phosphorylation of its receptors, two JAK kinases and three STAT transcription factors. One kinase, p135tyk2, is complexed with the IFNaR1 receptor, and may catalyze some of these phosphorylation events. We demonstrate that, in vitro, p135tyk2 phosphorylates two tyrosines on IFNaR1. A phosphopeptide corresponding to the major phosphorylation site (Tyr466) binds STAT2, but not STAT1, in an SH-2-dependent manner. Furthermore, only latent, non-phosphorylated STAT2 interacts with this phosphopeptide. When this phosphopeptide is introduced into permeabilized cells, the IFN alpha-dependent tyrosine phosphorylation of both STATs is blocked. Finally, mutant versions of IFNaR1, in which Tyr466 is changed to phenylalanine, can act in a dominant negative manner to inhibit phosphorylation of STAT2. These observations are consistent with a model in which IFNaR1 mediates the interaction between JAK kinases and the STAT transcription factors.

Amino Acid Sequence↗
PubMed1996

The SH2 domains of Stat1 and Stat2 mediate multiple interactions in the transduction of IFN-alpha signals.

Analysis of the ability of IFN-alpha to rapidly stimulate genes has led to the identification of a new family of signal transducing factors (STFs). The STF activated by IFN-alpha consists of two members of the STAT (Signal Transducers and Activators of Transcription) family of signaling proteins, Stat1 and Stat2. Sequence comparison of these STATs has determined that they share several conserved domains, the most notable of which is an SH2 domain. Recently, studies have determined that these SH2 domains can mediate a specific association between a STAT and the cytoplasmic domain of the appropriate receptor. Once associated with the receptor, the STATs become activated by an associated tyrosine kinase, whereupon they dissociate from the receptor and dimerize to form active STFs. The SH2 domain has also been implicated in the formation of STAT dimers found in STFs, suggesting it may play multiple roles in signaling. We have carried out a detailed analysis on the role of the Stat1 and Stat2 SH2 domains in the mediation of IFN-alpha stimulated signals. These studies, which have determined that the SH2 domain of Stat1 and Stat2 can mediate homo- as well as heterodimerization, suggest that a single SH2 domain-phosphotyrosyl interaction is sufficient for dimerization. Moreover, they provide the first direct evidence that the target of the SH2 domain is the STAT tyrosine activation site. In addition, these studies implicate the SH2 domain in another step in the signaling cascade, namely mediation of the interaction between STATs and their activating kinases (i.e. the JAKs).

Animals↗
PubMed1996

Comparative evaluation of chelating agents on the mobilization of cadmium: a mechanistic approach.

A comparative evaluation of chelating agents, namely, diethyl dithiocarbamate (DDC), dimethyl dithiocarbamate (DMDC), 1,4,8,11-tetraazacyclotetradecane (CYCLAM), 1,4,8,12-tetraazacyclopentadecane (TACPD), 2,3-dimercaptosuccinic acid (DMSA), and 2,3-dimercapto-1-propane sulfonate (DMPS) was conducted to assess their efficacy against acute cadmium (Cd) toxicity. DMSA and DMPS appeared to be most effective in reducing mortality as well as Cd burden of liver, kidneys, and brain in cadmium intoxicated mice. DMDC reduced Cd levels only in liver and kidneys, while DDC significantly enhanced its level in brain. CYCLAM and TACPD significantly increased the Cd level in liver and kidneys and were ineffective in brain. The therapeutic index as well as therapeutic efficacy was highest for DMSA followed by DMPS and DMDC. A fair degree of correlation was found to exist between (1) stability constant of Cd chelates and percent survival (r = .438, (2) stability constant and percent transport (r = .479), and (3) percent survival and percent transport (r =.447). However, the lipophilicity did not show any appreciable correlation with percent survival and stability constant of Cd chelates.

Animals↗
PubMed1996

Cell type-specific mechanisms regulate hepatitis B virus transgene expression in liver and other organs.

Intracellular expression of hepatitis B virus (HBV) was analysed in transgenic HBV mouse lines designated G7 and G26, the former lacking hepatitis B surface antigen (HBsAg) promoters. HBsAg mRNA expression was greater in the G26 line than in the G7 line, although in situ hybridization showed a qualitatively similar expression pattern in specific cell types. HBsAg mRNA was most abundant in hepatocytes, followed in magnitude by proximal renal tubular epithelial cells, pancreatic acinar cells, and epithelial cells of the gastric, small intestinal, and bronchiolar mucosae. In biliary epithelial cells, brain, spleen, large intestine, testis, heart, and skeletal muscle, HBsAg mRNA was undetectable. In cell transfection assays, the HBV enhancer/preS1 promoter efficiently expressed a luciferase reporter with appropriate upregulation by HNF-3 alpha and C/EBP alpha transcription factors in hepatocyte-derived cells but not in non-parenchymal epithelial liver cells or fibroblasts. These results suggest that cell-type specificity of HBV expression is regulated by interactions between viral elements and cellular transactivators. Variable expression of G7 and G26 HBV transgenes in epithelial cells combined with differences in transgene expression in similar sets of cells suggests at least two levels of regulation: one directing cell specificity of HBV expression and the other governing quantitative expression of HBV mRNA.

Animals↗
PubMed1996

Macrophage-T cell interaction in murine salmonellosis: selective down-regulation of ICAM-1 and B7 molecules in infected macrophages and its probable role in cell-mediated immunity.

Vaccine development and understanding of cellular immune modulatory mechanisms in salmonella infections have been impeded due to the paucity of data on antigens capable of eliciting effective immune responses. The present study was done to evaluate the efficacy of five major purified salmonella antigens (porins, pili, flagella, outer membrane proteins and heat shock proteins) in modulating T cell-macrophage interactions which play a central role in resistance to and recovery from infection with several intracellular pathogens, including salmonella. The results showed that the T cells recovered 10 days post-immunization (D10 T cells) from mice immunized with porins and outer membrane proteins showed maximum proliferation in the presence of macrophages incubated with dead bacteria; however, this response was decreased when T cells were co-cultured with live Salmonella typhimurium-infected macrophages. Delayed-type hypersensitivity responses, as measured by increased footpad thickness at 24 h, though induced effectively by porins, pili and flagella, were completely abrogated when D10 T cells were pre-incubated with macrophages infected with live bacteria. The phagocytic and bactericidal ability of normal macrophages, when grown in presence of T cell supernatants, was not influenced by the immunizing agents, but T cell supernatants obtained from mice immunized with porins and heat-shock protein triggered increased bactericidal activity. Further, the expression of the co-stimulatory molecules ICAM-1 and B7 increased with increasing bacteria (dead):macrophage ratio, but this expression was down-regulated upon incubation with live bacteria.

Animals↗
PubMed1996

Studies of liver repopulation using the dipeptidyl peptidase IV-deficient rat and other rodent recipients: cell size and structure relationships regulate capacity for increased transplanted hepatocyte mass in the liver lobule.

The feasibility of liver repopulation with hepatocytes has been shown, although clinical applications demand significant hepatic replacement. To show whether portal vascular bed in large animals could accomodate a greater cell number, we analyzed liver repopulation in syngeneic Fischer 344 rats deficient in dipeptidyl peptidase IV. This system allowed localization of transplanted normal hepatocytes in liver or various ectopic sites, as well as dual studies for analysis of gene expression. Interestingly, the product of a dipeptidyl peptidase IV substrate inactivated bile canalicular adenosine triphosphatase (ATPase) activity in normal but not in dipeptidyl peptidase IV-deficient rats, which allowed localization of dipeptidyl peptidase IV-deficient hepatocytes in normal rat liver for additional reversed transplantation systems. Further studies with genetically marked cells showed that because of the size difference between hepatocytes and portal vein radicles, intrasplenically transplanted cells were distributed in periportal areas (zone 1) in mice, whereas in larger animals (rats or rabbits) cells were also distributed downstream to midlobular (zone 2) or perivenous (zone 3) areas. Transplantation of an escalating number of hepatocytes showed that adult rats tolerated intrasplenic injection of a large cell number in single sessions (up to 1 X 10(8), approximately 10% to 15% of the host hepatocyte mass). Morphometric analysis of recipient livers showed survival of a significantly greater cell number with incorporation in host liver plates. At 4 weeks, transplantation of 2 x 10(7) hepatocytes into adult rats led to a survival of 1.4 +/- 1.0 x 10(6) transplanted cells/cm3 liver, whereas after transplantation of 5 x 10(7) cells or 7.5 x 10(7) cells, the number of surviving transplanted cells in the liver significantly increased to 4.1 +/- 1.4 x 10(6) transplanted cells/cm3 liver (mean, 2.9-fold; P<.003) and 5.5 +/- 1.3 x 10(6) transplanted cells/cm3 liver (mean, 3.9-fold; P<.003), respectively. When cells were injected in greater numbers, transplanted hepatocytes retained normal function and produced more serum albumin or hepatitis B surface antigen in deficient hosts. These data indicate the feasibility in larger animals of significant liver repopulation with hepatocyte transplantation. Use of dipeptidyl peptidase IV-deficient rats should help further analysis of mechanisms in liver repopulation.

Alanine Transaminase↗
PubMed1996

Hormone replacement therapy and cardiovascular disease.

Coronary heart disease is the principal cause of death in postmenopausal women. Postmenopausal women have an elevated cardiovascular risk profile in the form of android obesity (increased waist/hip ratio), hyperinsulinemia, impaired glucose tolerance, increased insulin resistance and elevated plasma LDL, VLDL, serum triglyceride and lipoprotein (a). A significant decrease in the relative risk of cardiovascular disease is observed with estrogen replacement therapy. The addition of progestogens commonly used in hormone replacement regimes does not, based on present evidence, seem to affect cardiovascular protection adversely. The literature on this subject has been reviewed and recommendations made with implications for the future.

Cardiovascular Diseases↗
PubMed1996

Relapse in schizophrenia: is there a relationship to substance abuse?

This retrospective study evaluated relapse in 22 patients with schizophrenia, comparing substance abusers with nonabusers. Medication compliance was ensured as all subjects were treated with decanoate neuroleptics. Substance abuse was documented by multiple urine drug screens. Substance abusers had a significantly higher readmission rate to the hospital compared to nonabusers. These data suggest that in the presence of documented medication compliance substance abuse remains a major factor contributing towards relapse.

Adult↗
PubMed1996

Functional outcome measures to assess interventions for spasticity.

PURPOSE: Clinicians use functional loss as a criterion to treat spasticity, but the connection between function and severity of spasticity is not well established for monitoring spasticity treatment effect. Studies were reviewed which have implemented outcome measures to assess functional changes relative to changes in spasticity. Criteria for review included the reliability and internal validity of the functional measures used and the strengths/weaknesses of the study designs that likely affected the external validity of the measures for this application. Guidelines are provided for the use and development of functional outcome measures in futures studies of spasticity treatment based on this review. DATA IDENTIFICATION: An English-language literature search using MEDLINE and bibliographies of published articles and textbooks was conducted. RESULTS: Very few functional measures demonstrated changes concurrent to a reduction in spasticity. There were multiple potential confounding factors in study protocols, reporting of results, and data analysis that might account for the limited number of measures shown to be valid for this application. Selected standardized ordinal functional outcome scales (the PECS and PEDI) and specific functional tasks were identified as measures that show promise for assessing changes concurrent with altered spasticity level. CONCLUSION: Based on a review of previous studies, functional measures involving posture, positioning, balance, and certain mobility skills have potential, with further test development, to provide needed information regarding the impact of spasticity on functional outcome.

Disability Evaluation↗