Biomedical subjects

Manju Sharma

Publications and source records attributed to Manju Sharma.

16 recordsLinked to original sources

PubMed2006

Protective effect of bezafibrate on streptozotocin-induced oxidative stress and toxicity in rats.

The present study was aimed to find out the protective effect of bezafibrate on lipid peroxidation (LPO), activities of both enzymatic and non-enzymatic antioxidants and histopathological examination of pancreas in streptozotocin (STZ)-induced diabetic rats. Experimental diabetes was induced by a single dose of STZ (60mg/kg, i.p.) injection. The oxidative stress was measured by tissue LPO level, reduced glutathione (GSH) content and by enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) in liver and pancreas. Biochemical observations were further substantiated with histological examination of pancreas. The increase in blood glucose, LPO level with reduction in GSH content and decreased enzymatic activities were the salient features observed in diabetic control rats. Administration of bezafibrate (30mg/kg day, p.o.) for 15 days caused a significant reduction in blood glucose and LPO level in STZ treated rats (group III) when compared with diabetic control rats (group II). Furthermore, bezafibrate treated diabetic rats (group III) showed significant increase in the activities of both enzymatic and non-enzymatic antioxidants when compared to diabetic control rats (group II). Degenerative changes of pancreatic beta-cells in STZ treated rats were minimized to near normal morphology by administration of bezafibrate as evident by histopathological examination. The results obtained clearly indicate the role of oxidative stress in the induction of diabetes and suggest a protective effect of bezafibrate in this animal model.

Administration, Oral↗

PubMed2006

LZTS2 is a novel beta-catenin-interacting protein and regulates the nuclear export of beta-catenin.

Beta-catenin plays multiple roles in cell-cell adhesion and Wnt signal transduction. Through the Wnt signal, the cellular level of beta-catenin is constitutively regulated by the multicomponent destruction complex containing glycogen synthase kinase 3beta, axin, and adenomatous polyposis coli. Here, we present multiple lines of evidence to demonstrate that LZTS2 (lucine zipper tumor suppressor 2) interacts with beta-catenin, represses the transactivation of beta-catenin, and affects the subcellular localization of beta-catenin. The LZTS2 gene is located at 10q24.3, which is frequently lost in a variety of human tumors. A functional nuclear export signal (NES) was identified in the C terminus of the protein (amino acids 631 to 641). Appending this motif to green fluorescent protein (GFP) induced nuclear exclusion of the GFP fusion protein. However, introducing point mutations in either one or two leucine residues of this NES sequence abolished the nuclear exclusion of the LZTS2 protein. The nuclear export of LZTS2 can be blocked by leptomycin B (LMB), an inhibitor of the CRM1/exportin-alpha pathway. Intriguingly, beta-catenin colocalizes with LZTS2 in the cytoplasm of cells in the absence of LMB but in the nuclei of cells in the presence of LMB. Increasing the LZTS2 protein in cells reduces the level of nuclear beta-catenin in SW480 cells. Taken together, these data demonstrate that LZTS2 is a beta-catenin-interacting protein that can modulate beta-catenin signaling and localization.

Active Transport, Cell Nucleus↗

PubMed2006

Breakdown of the Stokes-Einstein relationship: role of interactions in the size dependence of self-diffusivity.

Einstein and others derived the reciprocal dependence of the self-diffusivity D on the solute radius r(u) for large solutes based on kinetic theory. We examine here (a) the range of r(u) over which Stokes-Einstein (SE) dependence is valid and (b) the precise dependence for small solutes outside of the SE regime. We show through molecular dynamics simulations that there are two distinct regimes for smaller solutes: (i) the interaction or Levitation effect (LE) regime for solutes of intermediate size and (ii) the D proportional, variant 1/r(u)(2) for still smaller solutes. We show that as the solute-solvent size ratio decreases, the breakdown in the Stokes-Einstein relationship leading to the LE regime has its origin in dispersion interaction between the solute and the solvent. These results explain reports of enhanced solute diffusion in solvents existing in the literature seen for small solutes for which no explanation exists.

Journal Article↗

PubMed2006

TEX14 is essential for intercellular bridges and fertility in male mice.

Cytokinesis in somatic cells concludes with the formation of a midbody, which is abscised to form individual daughter cells. In contrast, germ cell cytokinesis results in a permanent intercellular bridge connecting the daughter cells through a large cytoplasmic channel. During spermatogenesis, proposed roles for the intercellular bridge include germ cell communication, synchronization, and chromosome dosage compensation in haploid cells. Although several essential components of the midbody have recently been identified, essential components of the vertebrate germ cell intercellular bridge have until now not been described. Herein, we show that testis-expressed gene 14 (TEX14) is a novel protein that localizes to germ cell intercellular bridges. In the absence of TEX14, intercellular bridges are not observed by using electron microscopy and other markers. Spermatogenesis in Tex14(-/-) mice progresses through the transit amplification of diploid spermatogonia and the expression of early meiotic markers but halts before the completion of the first meiotic division. Thus, TEX14 is required for intercellular bridges in vertebrate germ cells, and these studies provide evidence that the intercellular bridge is essential for spermatogenesis and fertility.

Alleles↗

PubMed2005

hZimp7, a novel PIAS-like protein, enhances androgen receptor-mediated transcription and interacts with SWI/SNF-like BAF complexes.

Members of the PIAS (protein inhibitor of activated signal transducer and activator of transcription) family are negative regulators of the Janus family of tyrosine kinase (JAK)-signal transducer and activator of transcription pathway. Recently, PIAS proteins have been shown to interact with multiple signaling pathways in various cellular processes, and it has been demonstrated that PIAS and PIAS-like proteins interact with nuclear hormone receptors. In this study, we have identified a novel human PIAS-like protein, provisionally termed hZimp7, which shares a high degree of sequence similarity with hZimp10 (human zinc finger-containing, Miz1, PIAS-like protein on chromosome 10). hZimp7 (human zinc finger-containing, Miz1, PIAS-like protein on chromosome 7) possesses a molecular mass of approximately 100 kDa and contains a conserved Miz (msx-interacting zinc finger) domain, a nuclear translocation signal sequence, and a C-terminal transactivation domain. Northern blot analysis revealed that hZimp7 is predominantly expressed in testis, heart, brain, prostate, and ovary. Moreover, immunohistochemical staining of prostate tissues revealed that endogenous hZimp7 protein localizes to the nuclei of prostate epithelial cells and costains with the androgen receptor (AR). Further analysis of hZimp7 subcellular localization revealed that hZimp7 and the AR colocalize within the nucleus and form a protein complex at replication foci. Transient transfection experiments showed that hZimp7 augments the transcriptional activity of the AR and other nuclear hormone receptors. In contrast, reduction of endogenous hZimp7 protein expression by RNA interference decreased AR-mediated transcription. Finally, we determined that hZimp7 physically associates with Brg1 and BAF57, components of the ATP-dependent mammalian SWI/SNF-like BAF chromatin-remodeling complexes. The above data illustrate a potential role for hZimp7 in modulation of AR and/or other nuclear receptor-mediated transcription, possibly through alteration of chromatin structure by SWI/SNF-like BAF complexes.

Animals↗

PubMed2005

Levitation effect: size-dependent maximum in rotational diffusion in confined systems.

Molecular dynamics of a model guest tetrahedral molecule AX(4) with differing bond lengths l(AX) for A-X bonds have been carried out in a sphere with different surface roughness. The rotational-diffusion coefficient D(R) shows a maximum for a particular value of l(AX). We show that this corresponds to the distance at which the interaction of the guest with the atoms of the host is most favorable. Although, the intensity of the maximum decreases with increase in the roughness of the confining surface, it is seen that the maximum exists even for a reasonably high degree of roughness. The observed maximum arises from the minimum in the torque on the tetrahedral molecule from its interaction with the confining medium due to mutual cancellation of forces. Activation energy for rotation is seen to be also a minimum for the bond length for which D(R) is a maximum. These results suggest that there is a maximum in the rotational-diffusion coefficient when the rotating molecule is confined to a sphere of comparable size similar to the maximum in translational diffusion coefficient seen in porous solids (the levitation effect) [Yashonath and Santikary J. Phys. Chem. 98, 6368 (1994)]. On increase in the roughness of the sphere surface, the value of l(AX) at which the maximum in D(R) is seen decreases.

Journal Article↗

PubMed2005

Growth of Geobacter sulfurreducens under nutrient-limiting conditions in continuous culture.

A system for growing Geobacter sulfurreducens under anaerobic conditions in chemostats was developed in order to study the physiology of this organism under conditions that might more closely approximate those found in the subsurface than batch cultures. Geobacter sulfurreducens could be cultured under acetate-limiting conditions with fumarate or Fe(III)-citrate as the electron acceptor at growth rates between 0.04 and 0.09 h(-1). The molar growth yield was threefold higher with fumarate as the electron acceptor than with Fe(III), despite the lower mid-point potential of the fumarate/succinate redox couple. When growth was limited by availability of fumarate, high steady-state concentrations were detected, suggesting that fumarate is unlikely to be an important electron acceptor in sedimentary environments. The half-saturation constant, Ks, for acetate in Fe(III)-grown cultures (10 microM) suggested that the growth of Geobacter species is likely to be acetate limited in most subsurface sediments, but that when millimolar quantities of acetate are added to the subsurface in order to promote the growth of Geobacter for bioremediation applications, this should be enough to overcome any acetate limitations. When the availability of electron acceptors, rather than acetate, limited growth, G. sulfurreducens was less efficient in incorporating acetate into biomass but had higher respiration rates, a desirable physiological characteristic when adding acetate to stimulate the activity of Geobacter species during in situ uranium bioremediation. These results demonstrate that the ability to study the growth of G. sulfurreducens under steady-state conditions can provide insights into its physiological characteristics that have relevance for its activity in a diversity of sedimentary environments.

Acetates↗

PubMed2004

Plzf is required in adult male germ cells for stem cell self-renewal.

Adult germline stem cells are capable of self-renewal, tissue regeneration and production of large numbers of differentiated progeny. We show here that the classical mouse mutant luxoid affects adult germline stem cell self-renewal. Young homozygous luxoid mutant mice produce limited numbers of normal spermatozoa and then progressively lose their germ line after birth. Transplantation studies showed that germ cells from mutant mice did not colonize recipient testes, suggesting that the defect is intrinsic to the stem cells. We determined that the luxoid mutant contains a nonsense mutation in the gene encoding Plzf, a transcriptional repressor that regulates the epigenetic state of undifferentiated cells, and showed that Plzf is coexpressed with Oct4 in undifferentiated spermatogonia. This is the first gene shown to be required in germ cells for stem cell self-renewal in mammals.

Animals↗

PubMed2004

An Hsp27-related, dominant-negative-acting intracellular estradiol-binding protein.

New World primates (NWPs) exhibit a compensated form of resistance to gonadal steroid hormones. We demonstrated recently that estrogen resistance in NWP cells was associated with the overexpression of two proteins, a nonreceptor-related, dominant-negative-acting estrogen response element (ERE)-binding protein (ERE-BP) and an intracellular estradiol-binding protein (IEBP). Based on the N-terminal sequences of tryptic fragments of IEBP isolated from a 17beta-estradiol (E2) affinity column we cloned a full-length cDNA for IEBP from the estrogen-resistant NWP cell line, B95-8. Subsequent sequence analysis revealed 87% sequence identity between the deduced peptide for IEBP and human Hsp27. When hormone-responsive, wild-type Old World primate (OWP) cells were transiently transfected with IEBP cDNA, E2-directed ERE reporter luciferase activity was reduced by 50% compared with vector only-transfected OWP cells (p < 0.0018). When IEBP and ERE-BP were cotransfected, ERE promoter-reporter activity was reduced by a further 60% (p < 0.0001). Electrophoresis mobility shift analyses showed that IEBP neither bound to ERE nor competed with the estrogen receptor (ER) for binding to ERE. However, there was evidence of protein-protein interaction of IEBP and ERalpha; IEBP was coimmunoprecipitated with anti-ERalpha antibody in wild-type cells stably transfected with IEBP. A specific interaction between ERalpha and IEBP was confirmed in glutathione S-transferase pull-down and yeast two-hybrid assays. Data indicate that the Hsp27-related IEBP interacts with the ligand binding domain of the ERalpha. In summary, by inhibiting the ERalpha-E2 interaction, IEBP acts to squelch ERalpha-directed ERE-regulated transactivation and promote estrogen resistance in NWP cells.

Amino Acid Sequence↗

PubMed2004

Evaluation of cholinesterase to differentiate pleural exudates and transudates.

AIMS AND OBJECTIVES: The present study was undertaken to evaluate the usefulness of pleural fluid cholinesterase (PChE) level in pleural fluid and its ratio to serum cholinesterase (P/SChE) in order to differentiate transudates and exudates and to compare their diagnostic efficacy with the Light's criteria. MATERIAL AND METHODS: A total of 110 patients of pleural effusion of diverse etiology were studied. Eighty patients were of exudative pleural effusion of tubercular, malignant or parapneumonic origin and 30 patients were of transudative effusion. Cholinesterase was estimated in the pleural fluid and serum in all the patients. RESULTS: The mean PChE and P/S ChE were significantly higher in exudates as compared to transudates (p < 0.001). P/S ChE was 0.79 +/- 0.45 and 0.14 +/- 0.11 in exudates and transudates, respectively. When a cut-off value of 469 IU/L for PChE was taken for the diagnosis, it was found that 10% of exudates and 2.5% of transudates were misclassified. However percentage of misclassification decreased to 1.25% in exudates and 3.3% in transudates when the cut-off value of 0.24 for P/S ChE ratio was used. Using Light's criteria, a sensitivity of 91.25% and specificity of 90% with positive predictive value (PPV) of 96.05% and negative predictive value (NPV) of 79.42% was observed. However using P/S ChE, the PPV was 98.75% and NPV was 96.67%. CONCLUSIONS: The estimation of PChE and P/SChE ratio had better discriminatory capacity than Light's criteria. It is cost effective and more specific, therefore its routine estimation is recommended.

Adult↗

PubMed2003

hZimp10 is an androgen receptor co-activator and forms a complex with SUMO-1 at replication foci.

The androgen receptor (AR) plays a central role in male sexual development and in normal and malignant prostate cell growth and survival. It has been shown that transcriptional activation of AR is regulated through interaction with various co-factors. Here we identify a novel PIAS-like protein, hZimp10, as an AR-interacting protein. The transactivation domain (TAD) of AR and the central region of hZimp10 were found to be responsible for the interaction. A strong intrinsic transactivation domain was identified in the C-terminal, proline-rich region of hZimp10. Endogenous AR and hZimp10 proteins were co-stained in the nuclei of prostate epithelial cells from human tissue samples. In human prostate cancer cells, hZimp10 augmented the transcriptional activity of AR. Moreover, hZimp10 co-localized with AR and SUMO-1 at replication foci throughout S phase, and it was capable of enhancing sumoylation of AR in vivo. Studies using sumoylation deficient AR mutants suggested that the augmentation of AR activity by hZimp10 is dependent on the sumoylation of the receptor. Taken together, these data demonstrate that hZimp10 is a novel AR co-regulator.

Amino Acid Sequence↗

PubMed2003

The way ahead--the new technology in an old society.

Biotechnology is one of the most important scientific and technological revolutions of the last century and has greatly benefited various aspects of human life. The potentials are enormous and many breakthroughs have already been achieved in the area of healthcare, food, agricultural products and environmental production. The developments in this important area provide immediate benefits to mankind and offer environmentally friendly technologies for sustainable development. The Department of Biotechnology, Government of India, set up in 1986, has played an important catalytic role in promoting this revolutionary field. Research and development, technology validation and demonstration, technology transfer, human resource development, setting up of Centers of Excellence and promoting industry-academia interactions have been some of the major achievements during the last 15 years. A unique feature of this Department is the strong interaction with scientists and institutes across the country to promote biotechnology research and development efforts for commercialization and also to benefit the rural population for socio-economic development. A large number of research institutes/universities and organizations across the country have been supported in the areas of agriculture, healthcare, environment and industry. In addition, basic research has also been an important thrust area. In order to ensure that the benefits of biotechnology reach the masses at large, a very stringent biosafety mechanism has been adopted. India is a country rich in biodiversity with two hot spots and has a strong base of expertise available in nearly all fields--thus biotechnology could flourish leading to a Bioindustrial Revolution. We are today poised to be the leaders in this field in the 21st Century.

Agriculture↗

PubMed2002

Phosphatidylinositol 3-kinase/Akt stimulates androgen pathway through GSK3beta inhibition and nuclear beta-catenin accumulation.

PI3K/Akt plays a critical role in prostate cancer cell growth and survival. Recent studies have shown that the effect of PI3K/Akt in prostate cells is mediated through androgen signaling. The PI3K inhibitor, LY294002, and a tumor suppressor, PTEN, negatively regulate the PI3K/Akt pathway and repress AR activity. However, the molecular mechanisms whereby PI3K/Akt and PTEN regulate the androgen pathway are currently unclear. Here, we demonstrate that blocking the PI3K/Akt pathway reduces the expression of an endogenous AR target gene. Moreover, we show that the repression of AR activity by LY294002 is mediated through phosphorylation and inactivation of GSK3beta, a downstream substrate of PI3K/Akt, which results in the nuclear accumulation of beta-catenin. Given the recent evidence that beta-catenin acts as a coactivator of AR, our findings suggest a novel mechanism by which PI3K/Akt modulates androgen signaling. In a PTEN-null prostate cancer cell line, we show that PTEN expression reduces beta-catenin-mediated augmentation of AR transactivation. Using the mutants of beta-catenin, we further demonstrate that the repressive effect of PTEN is mediated by a GSK3beta-regulated degradation of beta-catenin. Our results delineate a novel link among the PI3K, wnt, and androgen pathways and provide fresh insights into the mechanisms of prostate tumor development and progression.

Androgens↗

PubMed2002

Linking beta-catenin to androgen-signaling pathway.

The androgen-signaling pathway is important for the growth and progression of prostate cancer cells. The growth-promoting effects of androgen on prostate cells are mediated mostly through the androgen receptor (AR). There is increasing evidence that transcription activation by AR is mediated through interaction with other cofactors. beta-Catenin plays a critical role in embryonic development and tumorigenesis through its effects on E-cadherin-mediated cell adhesion and Wnt-dependent signal transduction. Here, we demonstrate that a specific protein-protein interaction occurs between beta-catenin and AR. Unlike the steroid hormone receptor coactivator 1 (SRC1), beta-catenin showed a strong interaction with AR but not with other steroid hormone receptors such as estrogen receptor alpha, progesterone receptor beta, and glucocorticoid receptor. The ligand binding domain of AR and the NH(2) terminus combined with the first six armadillo repeats of beta-catenin were shown to be necessary for the interaction. Through this specific interaction, beta-catenin augments the ligand-dependent activity of AR in prostate cancer cells. Moreover, expression of E-cadherin in E-cadherin-negative prostate cancer cells results in redistribution of the cytoplasmic beta-catenin to the cell membrane and reduction of AR-mediated transcription. These data suggest that loss of E-cadherin can elevate the cellular levels of beta-catenin in prostate cancer cells, which may directly contribute to invasiveness and a more malignant tumor phenotype by augmenting AR activity during prostate cancer progression.

Androgens↗

PubMed2002

A novel zinc finger transcription factor with two isoforms that are differentially repressed by estrogen receptor-alpha.

Estrogen receptor-alpha (ERalpha) can induce the expression of genes in response to estrogen by binding to estrogen response elements in the promoters of target genes. There is growing evidence that ERalpha can alter patterns of gene expression in response to ligand by regulating the activity of other factors through a direct protein-protein interaction. To identify other factors that are regulated by ERalpha, a yeast two-hybrid screen was performed that identified a novel Cys(2)His(2) zinc finger protein named ZER6. The ZER6 protein contains a Kruppel-associated box domain and six Cys(2)His(2) zinc fingers. Transcripts from the ZER6 gene can have alternate 5' exons and encode either a p71 or p52 isoform. The p52-ZER6 protein interacts strongly with ERalpha in the presence of 17beta-estradiol, whereas the p71-ZER6 isoform has a HUB-1 amino-terminal domain that inhibits the interaction with ERalpha. A consensus ZER6 binding element was defined using PCR-assisted binding site selection. In COS-1 cells, both the p52 and p71 isoforms can activate transcription through the ZER6 binding element; however, in the presence of ERalpha, transactivation by the p52 isoform is specifically repressed. Overexpression of the p52 isoform was able to abrogate activation by p71-ZER6. Expression of ZER6 was largely restricted to the mammary gland with a lower level of expression in the kidney. We conclude that ZER6 is a novel zinc finger transcription factor in which regulation of transcription in hormone-responsive cells can be controlled by the relative level of expression of two distinct isoforms.

Amino Acid Sequence↗

PubMed2002

A controlled trial of intermittent enteral nutrient supplementation in maintenance hemodialysis patients.

OBJECTIVE: This controlled trial was undertaken to evaluate the benefits of short-term enteral nutrient supplementation in maintenance hemodialysis (MHD) patients using a high-calorie and high-protein blend formula (low-cost home-prepared [HP] blend or a commercially available supplement) and to study its effect on selected parameters of nutritional status. The acceptability and palatability of the HP blend formula, ease of use, and cost were also assessed in comparison with the commercial nutritional supplement (CNS). DESIGN: Randomized controlled trial. SETTING: Hemodialysis (HD) unit of a tertiary referral care hospital in Southern India. PATIENTS: Nondiabetic adult MHD patients with no intercurrent illness, on regular thrice weekly MHD for at least 1 month before recruitment, with a body mass index (BMI) <20 and a serum albumin level of <4.0 g/dL. Patients were randomized into control group and experimental group, the latter in turn to recieve either CNS or HP blend. INTERVENTION: The control group received appropriate monitoring, including dietary recall and counselling for the prescribed diet (protein intake of 1.2 g/kgIBW/d and energy of 35 to 45 kcal/kgIBW/d) but no specific post-HD supplement. Patients in the supplement group received the respective supplement post-HD (providing 500 kcal and 15 g protein) for 1 month in addition to the monitored diet prescription. MAIN OUTCOME MEASURES: (1) Nutritional status parameters, BMI and serum albumin; (2) functional status on a 10-point Karnofsky scale; (3) adverse metabolic effects, hyperphosphatemia at start and end of study; and (4) subjective scoring for appetite, and acceptability of and tolerance to supplement. RESULTS: Both groups showed an improvement in dry weight and BMI. In addition, the supplement group showed a significant increase in serum albumin level and functional scoring. Mild hyperphosphatemia occurred in the supplement group. An increase in baseline food intake was seen in the control group, but not in the supplemented group. No intolerance was reported to either supplement. CONCLUSION: Enteral nutrient supplementation was shown to bring about a significant improvement in serum albumin level even in a short-term study. Use of an HP supplement was beneficial, acceptable, and inexpensive.

Adult↗