Biomedical subjects

Nidhi Sharma

Publications and source records attributed to Nidhi Sharma.

13 recordsLinked to original sources

PubMed2007

E2f1, E2f2, and E2f3 control E2F target expression and cellular proliferation via a p53-dependent negative feedback loop.

E2F-mediated control of gene expression is believed to have an essential role in the control of cellular proliferation. Using a conditional gene-targeting approach, we show that the targeted disruption of the entire E2F activator subclass composed of E2f1, E2f2, and E2f3 in mouse embryonic fibroblasts leads to the activation of p53 and the induction of p53 target genes, including p21(CIP1). Consequently, cyclin-dependent kinase activity and retinoblastoma (Rb) phosphorylation are dramatically inhibited, leading to Rb/E2F-mediated repression of E2F target gene expression and a severe block in cellular proliferation. Inactivation of p53 in E2f1-, E2f2-, and E2f3-deficient cells, either by spontaneous mutation or by conditional gene ablation, prevented the induction of p21(CIP1) and many other p53 target genes. As a result, cyclin-dependent kinase activity, Rb phosphorylation, and E2F target gene expression were restored to nearly normal levels, rendering cells responsive to normal growth signals. These findings suggest that a critical function of the E2F1, E2F2, and E2F3 activators is in the control of a p53-dependent axis that indirectly regulates E2F-mediated transcriptional repression and cellular proliferation.

Animals↗

PubMed2006

Control of the p53-p21CIP1 Axis by E2f1, E2f2, and E2f3 is essential for G1/S progression and cellular transformation.

The E2F family of transcription factors is believed to have an essential role in the control of cellular proliferation by regulating the transcription of genes involved in cell cycle progression. Previous work has demonstrated that the targeted inactivation of E2f1, E2f2, and E2f3 results in elevated p21(CIP1) protein levels, loss of E2F target gene expression, and cell cycle arrest at G1/S and G2/M, suggesting a strict requirement for these E2Fs in the control of normal cellular proliferation. We now demonstrate that E2f1, E2f2, and E2f3 are also required for oncogene-mediated transformation of mouse embryonic fibroblasts. Analysis of synchronized populations of mouse embryonic fibroblasts revealed that the inactivation of p21(CIP1) restores the ability of E2f1-3-deficient cells to enter and transit through G1/S (but not G2/M). In contrast, loss of p53 restored the ability of these cells to progress through both G1/S and mitosis, leading to their continued proliferation. The inactivation of p53 (but not p21(CIP1)) rendered E2f1-3-deficient cells sensitive to transformation and tumorigenesis. These results suggest that the negative regulation of the p53-p21(CIP1) axis by the E2F1-3 factors is critical for cell cycle progression and cellular transformation.

Animals↗

PubMed2006

Lifestyle associated risk factors in adolescents.

OBJECTIVE: The data on these risk factors in school age population is deficient in India. The present study was conducted to evaluate the prevalence of lifestyle associated risk factors for non-communicable diseases in apparently healthy school children in an urban school in Delhi using standard criteria. METHODS: The study was carried out among 510 students of classes 9th-12th of a school in New Delhi and in the age group of 12 to 18 years. The students were surveyed through an age appropriate modified GSHS (Global School Based Student Health Survey) self administered questionnaire. Height and Weight were measured using standardized equipment and procedure. The blood pressure was measured using OMRON electronic B.P apparatus which were standardized daily against a mercury sphygmomanometer. The statistical analysis was done using Epinfo ver.3.3 and SPSS ver11.5. RESULTS: The study documents the inappropriate dietary practices (fast food consumption, low fruit consumption), low physical activity, higher level of experimentation with alcohol and to a lesser extent smoking, high prevalence of obesity and hypertension in the school children. The study also showed an association between BMI, systolic and diastolic blood pressures amongst children and other lifestyle factors. CONCLUSION: School based interventions are required to reduce the morbidity associated with non-communicable diseases.

Adolescent↗

PubMed2006

Rapid detection of enterotoxigenic Bacteroides fragilis in diarrhoeal faecal samples.

BACKGROUND & OBJECTIVES: Enterotoxigenic Bacteroides fragilis (ETBF) is an important aetiological agent of acute diarrhoeal illness in humans. It is a fastidious anaerobe and takes 3-5 days when grown in culture, and test for enterotoxin detection requires additional time conventionally. The present study was aimed to standardize a rapid and sensitive diagnostic assay and to screen the presence of ETBF isolates directly in faecal samples using polymerase chain reaction (PCR) technique. METHODS: A total of 85 faecal samples were processed for both aerobic and anaerobic bacterial isolation by culture technique and also subjected to PCR, for amplification of neuraminidase and enterotoxin genes of B. fragilis using specific primers. RESULTS: PCR was found to be positive for neuraminidase gene in 14/65 (21.5%) and for both neuraminidase and enterotoxin genes in 4/65 (6.1%) faecal samples within 48 h in study group. B. fragilis did not grow in any of the faecal samples when cultured anaerobically. However, the delay in transport and processing of faecal samples for anaerobic culture may be responsible for culture negativity. INTERPRETATION & CONCLUSION: PCR assay can be used as a rapid and sensitive diagnostic tool for the identification of ETBF in culture as well as directly from diarrhoeal faecal samples instead of using conventional technique. The association of ETBF in diarrhoeal diseases is unclear and importance of ETBF as a causal agent will require more studies in Indian population.

Adult↗

PubMed2005

2Apro is a multifunctional protein that regulates the stability, translation and replication of poliovirus RNA.

Poliovirus 2A(pro) is required for the inhibition of host cell protein synthesis and efficient viral replication. We investigated the role of 2A(pro) in regulating viral RNA stability, translation and replication in HeLa S10 reactions. The protease activity of 2A(pro) or its polyprotein precursors, 2AB or P2, was required to increase the stability of viral RNA and prolong translation. Since other viral proteins were not required for the observed effects of 2A(pro), it is likely that a cellular protein(s) modified by 2A(pro) mediated these effects on stability and translation. In addition, the protease activity of 2A(pro) stimulated negative-strand initiation by approximately five-fold but had no effect on positive-strand initiation. The 2A(pro) stimulation of negative-strand synthesis was independent of its effect on stability and translation. These findings further extend the previously known functions of protein 2A(pro) to include its role in increasing RNA stability, prolonging translation and stimulating negative-strand synthesis.

Cysteine Endopeptidases↗

PubMed2005

The molecular biology of the low-temperature response in plants.

Plants growing in temperate regions are able to survive freezing temperatures from -5 degrees to -30 degrees C, depending on the species, through a process known as cold acclimation. In the last decade much work has been done on the molecular mechanisms of low temperature (LT) signal transduction and cold acclimation. Mutant studies and microarray analyses have revealed C-Repeat binding factor (CBF) -dependent and -independent signaling pathways in plants. Experimental evidence suggests the existence of 'potential LT sensors' but as yet there is no direct proof. A number of signal transducers such as various kinases/phosphatases have been demonstrated but the signal transduction pathways have not been elucidated. An understanding of the molecular basis of the signaling process, however, is of potential practical application. Designing new strategies to improve cold tolerance in crop varieties could increase the plant productivity and also expand the area under cultivation.

Acclimatization↗

PubMed2005

3'-Terminal sequence in poliovirus negative-strand templates is the primary cis-acting element required for VPgpUpU-primed positive-strand initiation.

The 5' cloverleaf in poliovirus RNA has a direct role in regulating the stability, translation, and replication of viral RNA. In this study, we investigated the role of stem a in the 5' cloverleaf in regulating the stability and replication of poliovirus RNA in HeLa S10 translation-replication reactions. Our results showed that disrupting the duplex structure of stem a destabilized viral RNA and inhibited efficient negative-strand synthesis. Surprisingly, the duplex structure of stem a was not required for positive-strand synthesis. In contrast, altering the primary sequence at the 5'-terminal end of stem a had little or no effect on negative-strand synthesis but dramatically reduced positive-strand initiation and the formation of infectious virus. The inhibition of positive-strand synthesis observed in these reactions was most likely a consequence of nucleotide alterations in the conserved sequence at the 3' ends of negative-strand RNA templates. Previous studies suggested that VPgpUpU synthesized on the cre(2C) hairpin was required for positive-strand synthesis. Therefore, these results are consistent with a model in which preformed VPgpUpU serves as the primer for positive-strand initiation on the 3'AAUUUUGUC5' sequence at the 3' ends of negative-strand templates. Our results suggest that this sequence is the primary cis-acting element that is required for efficient VPgpUpU-primed positive-strand initiation.

DNA Primers↗

PubMed2003

Oxygen sensing by primary cardiac fibroblasts: a key role of p21(Waf1/Cip1/Sdi1).

In mammalian organs under normoxic conditions, O2 concentration ranges from 12% to <0.5%, with O2 approximately 14% in arterial blood and <10% in the myocardium. During mild hypoxia, myocardial O2 drops to approximately 1% to 3% or lower. In response to chronic moderate hypoxia, cells adjust their normoxia set point such that reoxygenation-dependent relative elevation of PO2 results in perceived hyperoxia. We hypothesized that O2, even in marginal relative excess of the PO2 to which cardiac cells are adjusted, results in activation of specific signal transduction pathways that alter the phenotype and function of these cells. To test this hypothesis, cardiac fibroblasts (CFs) isolated from adult murine ventricle were cultured in 10% or 21% O2 (hyperoxia relative to the PO2 to which cells are adjusted in vivo) and were compared with those cultured in 3% O2 (mild hypoxia). Compared with cells cultured in 3% O2, cells that were cultured in 10% or 21% O2 demonstrated remarkable reversible G2/M arrest and a phenotype indicative of differentiation to myofibroblasts. These effects were independent of NADPH oxidase function. CFs exposed to high O2 exhibited higher levels of reactive oxygen species production. The molecular signature response to perceived hyperoxia included (1) induction of p21, cyclin D1, cyclin D2, cyclin G1, Fos-related antigen-2, and transforming growth factor-beta1, (2) lowered telomerase activity, and (3) activation of transforming growth factor-beta1 and p38 mitogen-activated protein kinase. CFs deficient in p21 were resistant to such O2 sensitivity. This study raises the vital broad-based issue of controlling ambient O2 during the culture of primary cells isolated from organs.

Animals↗

PubMed2003

Effects of oral Lactobacillus GG on enteric microflora in low-birth-weight neonates.

BACKGROUND: Colonization patterns, especially by anaerobic flora, may play an important role in neonatal gut function. Probiotics could affect disease risk either directly through colonization or indirectly by promoting changes in gut microbial ecology. METHODS: To study the ability of Lactobacillus GG(LGG) to colonize the neonatal gut and modify its microbial ecology, a prospective, randomized study was performed in 71 preterm infants of less than 2000 g birth weight. Infants less than 1500 g (24 treated, 15 control) received 10(9) LGG orally twice daily for 21 days. Those infants weighing 1500 to 1999 g (23 treated, 9 control) were treated for 8 days. Stools were collected before treatment and on day 7 to 8 (and day 14 and 21, in the infants weighing less than 1500 g) for quantitative aerobic and anaerobic cultures. RESULTS: Colonization with LGG occurred in 5 of 24 (21%) infants who weighed less than 1500 g versus 11 of 23 (47%) in larger infants. Colonization was limited to infants who were not on antibiotics within 7 days of treatment with LGG. There was a paucity of bacterial species at baseline, although larger infants had more bacterial species (1.59 +/- 0.13 (SEM) vs 1.11 +/- 0.12; P < 0.03) and higher mean log colony forming units (CFU) (8.79 +/- 0.43 vs 7.22 +/- 0.63; P < 0.05) compared with infants weighing less than 1500 g LGG. Treatment in infants weighing less than 1500 g resulted in a significant increase in species number by day 7, with further increases by day 21. This increase was mainly the result of increased Gram (+) and anaerobic species. No difference in species number was noted in controls. Mean log CFU of Gram (-) bacteria did not change in treated infants weighing less than 1500 g. However, Gram (+) mean log CFU showed a significant increase on day 21 (6.1 +/- 0.9) compared with day 0 (3.5 +/- 0.9) (P < 0.05). No significant changes in species number or quantitative counts were noted after LGG treatment in the infants weighing 1500 to 1999 g LGG was well tolerated in all infants. CONCLUSION: The neonatal response to a probiotic preparation is dependent on gestational and post-natal age and prior antibiotic exposure. Although LGG is a relatively poor colonizer in infants, especially those infants weighing less than 1500 g at birth, it does appear to affect neonatal intestinal colonization patterns.

Administration, Oral↗

PubMed2003

Poliovirus cre(2C)-dependent synthesis of VPgpUpU is required for positive- but not negative-strand RNA synthesis.

The cre(2C) hairpin is a cis-acting replication element in poliovirus RNA and serves as a template for the synthesis of VPgpUpU. We investigated the role of the cre(2C) hairpin on VPgpUpU synthesis and viral RNA replication in preinitiation RNA replication complexes isolated from HeLa S10 translation-RNA replication reactions. cre(2C) hairpin mutations that block VPgpUpU synthesis in reconstituted assays with purified VPg and poliovirus polymerase were also found to completely inhibit VPgpUpU synthesis in preinitiation replication complexes. Surprisingly, blocking VPgpUpU synthesis by mutating the cre(2C) hairpin had no significant effect on negative-strand synthesis but completely inhibited positive-strand synthesis. Negative-strand RNA synthesized in these reactions immunoprecipitated with anti-VPg antibody and demonstrated that it was covalently linked to VPg. This indicated that VPg was used to initiate negative-strand RNA synthesis, although the cre(2C)-dependent synthesis of VPgpUpU was inhibited. Based on these results, we concluded that the cre(2C)-dependent synthesis of VPgpUpU was required for positive- but not negative-strand RNA synthesis. These findings suggest a replication model in which negative-strand synthesis initiates with VPg uridylylated in the 3' poly(A) tail in virion RNA and positive-strand synthesis initiates with VPgpUpU synthesized on the cre(2C) hairpin. The pool of excess VPgpUpU synthesized on the cre(2C) hairpin should support high levels of positive-strand synthesis and thereby promote the asymmetric replication of poliovirus RNA.

Carrier Proteins↗

PubMed2002

Dermal wound healing properties of redox-active grape seed proanthocyanidins.

Angiogenesis plays a central role in wound healing. Among many known growth factors, vascular endothelial growth factor (VEGF) is believed to be the most prevalent, efficacious, and long-term signal that is known to stimulate angiogenesis in wounds. The wound site is rich in oxidants, such as hydrogen peroxide, mostly contributed by neutrophils and macrophages. We proposed that oxidants in the wound microenvironment support the repair process. Proanthocyanidins or condensed tannins are a group of biologically active polyphenolic bioflavonoids that are synthesized by many plants. Previously we have reported that a grape seed proanthycyanidin extract containing 5000 ppm resveratrol (GSPE) potently upregulates oxidant and tumor necrosis factor-alpha inducible VEGF expression in human keratinocytes (Free Radic. Biol. Med. 31:38-42, 2001). Our current objective was to follow up on that finding and test whether GSPE influences dermal wound healing in vivo. First, using a VEGF promoter-driven luciferase reporter construct we observed that the potentiating effect of GSPE on inducible VEGF expression is at the transcriptional level. The reporter assay showed that GSPE alone is able to drive VEGF transcription. Next, two dermal excisional wounds were inflicted on the back of mice and the wounds were left to heal by secondary intention. Topical application of GSPE accelerated wound contraction and closure. GSPE treatment was associated with a more well-defined hyperproliferative epithelial region, higher cell density, enhanced deposition of connective tissue, and improved histological architecture. GSPE treatment also increased VEGF and tenascin expression in the wound edge tissue. Tissue glutathione oxidation and 4-hydroxynonenal immunostaining results supported that GSPE application enhanced the oxidizing environment at the wound site. Oxidants are known to promote both VEGF as well as tenascin expression. In summary, our current study provides firm evidence to support that topical application of GSPE represents a feasible and productive approach to support dermal wound healing.

Animals↗

PubMed2002

Assessment of reversible contraceptive efficacy of methanol extract of Mentha arvensis L. leaves in male albino mice.

The present study was undertaken to assess the reversible contraceptive efficacy of methanolic extract of Mentha arvensis leaves. Aqueous solution of the extract (10 mg per day per mouse) when administered orally to male mice of proven fertility for 20, 40 and 60 days caused inhibition of fertility while maintaining their normal sexual behaviour. With the increase in treatment duration, there occurred a corresponding decrease in the mean weight of testis and accessory organs of reproduction. Sperm concentration, motility and viability in the cauda epididymis were also decreased. Spermatozoa with coiled tails also appeared in the epididymal smear. However, all the induced effects returned to normalcy within 30 days following withdrawal of 60-day treatment. Oral administration of the extract also did not affect the body weight of the mice and their blood cells count, packed cell volume, haemoglobin and blood/serum biochemistry.

Administration, Oral↗

PubMedDate not supplied

Guillain-Barré syndrome: association with Campylobacter jejuni and Mycoplasma pneumoniae infections in India.

BACKGROUND: Guillain-Barré syndrome is the most common cause of acute neuromuscular paralysis and is considered a post-infectious disease. METHODS: Twenty patients with Guillain-Barré syndrome admitted to the Neurosciences Centre at the All India Institute of Medical Sciences from November 1997 to August 1998 were investigated for evidence of antecedent infections. This case-control study included 2 controls for each patient, one a household control and the other an age- and sex-matched hospital control suffering from a neurological illness other than Guillain-Barré syndrome. Evidence of recent Campylobacter jejuni infection was investigated by culture and serology, and for Mycoplasma pneumoniae by serology. RESULTS: There was evidence of recent C. jejuni infection in 35% of the patients compared with 25% of household controls and none of the hospital controls. M. pneumoniae infection was seen in 50% of patients compared with 25% of household controls and 15% of hospital controls. About one-third of the patients (30%) had evidence of both infections. The association of both infections in patients was found to be statistically significant as compared to hospital controls. CONCLUSION: C. jejuni and M. pneumoniae may be important antecedent illnesses in patients with Guillain-Barré syndrome in India.

Adolescent↗