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Biomedical subjects

N Singh

Publications and source records attributed to N Singh.

At least 91 records · Page 5Linked to original sources
PubMed2001

Effect of defects on thermal denaturation of DNA oligomers.

Effect of defects on the melting profile of short heterogeneous DNA chains is calculated using the Peyrard-Bishop Hamiltonian. On-site potential on a defect site is represented by a potential that has only a short-range repulsion and a flat part without well of the Morse potential. Stacking energy between two neigbouring pairs involving a defect site is also modified. The results are found to be in good agreement with the experiments.

DNA↗
PubMed2001

Efficient presentation of both cytosolic and endogenous transmembrane protein antigens on MHC class II is dependent on cytoplasmic proteolysis.

Peptides from extracellular proteins presented on MHC class II are mostly generated and loaded in endolysosomal compartments, but the major pathways responsible for loading peptides from APC-endogenous sources on MHC class II are as yet unclear. In this study, we show that MHC class II molecules present peptides from proteins such as OVA or conalbumin introduced into the cytoplasm by hyperosmotic pinosome lysis, with efficiencies comparable to their presentation via extracellular fluid-phase endocytosis. This cytosolic presentation pathway is sensitive to proteasomal inhibitors, whereas the presentation of exogenous Ags taken up by endocytosis is not. Inhibitors of nonproteasomal cytosolic proteases can also inhibit MHC class II-restricted presentation of cytosolically delivered protein, without inhibiting MHC class I-restricted presentation from the same protein. Cytosolic processing of a soluble fusion protein containing the peptide epitope I-Ealpha(52-68) yields an epitope that is similar to the one generated during constitutive presentation of I-Ealpha as an endogenous transmembrane protein, but is subtly different from the one generated in the exogenous pathway. Constitutive MHC class II-mediated presentation of the endogenous transmembrane protein I-Ealpha is also specifically inhibited over time by inhibitors of cytosolic proteolysis. Thus, Ag processing in the cytoplasm appears to be essential for the efficient presentation of endogenous proteins, even transmembrane ones, on MHC class II, and the proteolytic pathways involved may differ from those used for MHC class I-mediated presentation.

Acetylcysteine↗
PubMed2001

An assessment of the usefulness of a rapid immuno-chromatographic test, "Determine trade mark malaria pf" in evaluation of intervention measures in forest villages of central India.

BACKGROUND: Plasmodium falciparum malaria, is a major health problem in forested tribal belt of central India. Rapid and accurate methods are needed for the diagnosis of P. falciparum. We performed a blinded evaluation of the recently introduced Determine trade mark malaria pf test (Abbott, Laboratories, Japan) compared with microscopy and splenomegaly in children in epidemic prone areas of district Mandla to assess the impact of intervention measures. METHODS: Children aged 2-10 yrs with and without fever were examined for spleen enlargement by medical specialist by establishing a mobile field clinic. From these children thick blood smears were prepared from finger prick and read by a technician. Simultaneously, rapid tests were performed by a field lab attendant. The figures for specificity, sensitivity and predictive values were calculated using microscopy as gold standard. RESULTS: In all 349 children were examined. The sensitivity and specificity for Determine rapid diagnostic test were 91 and 80% respectively. The positive predictive values (PPV), negative predictive values (NPV) and accuracy of the test were respectively 79, 91 and 85%. On the contrary, the sensitivity and specificity of spleen in detecting malaria infection were 57 and 74 % respectively with PPV of 73%, NPV 59 % and an accuracy of 65%. CONCLUSIONS: Determine trade mark malaria rapid diagnostic test is easier and quicker to perform and has other advantages over microscopy in not requiring prior training of personnel or quality control. Thus, highlighting the usefulness of a rapid antigen test in assessing prevailing malaria situation in remote areas.

Animals↗
PubMed2001

Control of an outbreak of infection due to extended-spectrum beta-lactamase--producing Escherichia coli in a liver transplantation unit.

We report an outbreak of infection due to genotypically identical extended-spectrum beta-lactamase--producing Escherichia coli among patients in a liver transplantation unit. Control of the outbreak was achieved by a combination of contact isolation, feedback on hand hygiene, and gut decontamination with an orally administered fluoroquinolone. These interventions led to abrupt curtailment of the outbreak.

Disease Outbreaks↗
PubMed2001

Preemptive prophylaxis with a lipid preparation of amphotericin B for invasive fungal infections in liver transplant recipients requiring renal replacement therapy.

BACKGROUND: Posttransplant renal replacement therapy has been shown to be an independently significant risk factor for invasive fungal infections after liver transplantation. We assessed the efficacy of a lipid preparation of amphotericin B as prophylaxis for invasive fungal infections, directed toward liver transplant recipients requiring renal replacement therapy. METHODS: A total of 148 patients transplanted between 1990 and 1997 received no antifungal prophylaxis. Since 1997, 38 patients underwent liver transplantation; antifungal prophylaxis with a lipid preparation of amphotericin B was used in patients requiring renal replacement therapy. RESULTS: Fifteen percent (22 of 148) of the patients transplanted before 1997 required renal replacement therapy. In this cohort, the incidence of invasive fungal infections (36% vs. 7%, P=0.0007) and invasive aspergillosis (14% vs. 2%, P=0.02) was significantly higher in patients who required renal replacement therapy compared with those who did not. Since 1997, 29% (11 of 38) of the patients required renal replacement therapy and received antifungal prophylaxis. Invasive fungal infections occurred in 36% (8 of 22) of the patients who received no prophylaxis (patients before 1997), and 0% (0 of 11, P=0.03) in those who received antifungal prophylaxis (since 1997). Antifungal prophylaxis was independently associated with protection from fungal infection (P=0.017). No reduction in mortality with antifungal prophylaxis was documented. CONCLUSION: Prophylaxis with a lipid preparation of amphotericin B was associated with a significant reduction in invasive fungal infections in high-risk liver transplant recipients, i.e., those requiring renal replacement therapy. However, no beneficial effect on survival could be documented.

Adult↗
PubMed2001

Vitamin C augments chemotherapeutic response of cervical carcinoma HeLa cells by stabilizing P53.

Human Papilloma Virus (HPV) is associated in most instances with cervical cancer. The HPV oncoproteins target P53 protein for degradation, leading to deregulation of cell cycle. We investigated whether stabilization of P53 in cervical cancer cells, by downregulating HPV transcription would restore the apoptotic ability of these cells. Our findings show that vitamin C downregulates the redox sensitive transcription factor AP-1 and decreases one of its transcription targets HPV E6, and stabilizes P53. This was associated with an increase in Bax and decrease in Bcl-2 and telomerase activity. Accumulation of P53 and its target gene bax then sensitized HeLa cells to cell-cycle arrest, cell death/apoptosis induced by cisplatin, and etoposide. Increasing drug sensitivity of cervical carcinoma cells by stabilizing P53 using vitamin C is a novel approach and has potential clinical relevance.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Differential sensitivity of murine myeloid FDC-P1 cells and apoptosis resistant mutant(s) to anticancer drugs.

There is growing evidence which suggests that dysregulation of apoptosis may lead to several disease states including cancer. To investigate the mechanism controlling the induction of cell death, apoptosis defective/resistant (Apt-) mutants were isolated and characterized in this study. FDC-P1, a mouse myeloid cell line that depends upon IL-3 for survival and growth but undergoes apoptosis when deprived of growth factor, was mutagenized by treatment with ethyl methane sulfonate. We selected cells that survived the growth factor deprivation but did not grow without the factor. Surviving cells were cloned by limiting dilution and four clones that showed the least morphological characteristics and biochemical changes of apoptosis were chosen. Unlike the parent FDC-P1, these mutants were cross resistant to apoptosis induced by a variety of antitumor drugs such as Adriamycin, Dexamethasone, VP-16, as well as reactive oxygen species (ROS) generated by xanthine/xanthine oxidase (X/XO). We used one of these Apt- mutant to test candidate death genes. Our findings suggest that the preferential increase in Bax/Bcl-2 ratio, p53, c-Myc, Caspase-3 and decrease in AP-1 on treatment with various anticancer drugs may contribute to the preferential apoptotic response in FDC-P1 cells but to varying degrees. Whereas, the higher constitutive level of antioxidant enzymes superoxide dismutase and catalase in the Apt- mutant may contribute at least in part to its resistance.

Animals↗
PubMed2001

Preemptive therapy versus universal prophylaxis with ganciclovir for cytomegalovirus in solid organ transplant recipients.

Whether preemptive therapy or universal prophylaxis with ganciclovir is the optimal approach against cytomegalovirus (CMV) remains unresolved. Controversy abounds with respect to the efficacy of preemptive therapy, the reliability of preemptive therapy tools, the logistical difficulties in conducting surveillance monitoring for CMV, the cost of prophylaxis, the effect of prophylaxis on indirect sequelae of CMV and epidemiology of CMV, and the potential for emergence of ganciclovir-resistant CMV. Although neither approach is wholly adequate, a discussion of the relative merits and limitations of the 2 approaches may guide the selection of a rational approach toward prevention of CMV infection in organ transplant recipients.

Antiviral Agents↗
PubMed2001

The role of Alzheimer's disease-related presenilin 1 in intercellular adhesion.

Most cases of familial early-onset Alzheimer's disease are caused by mutations in the presenilin 1 (PS1) gene. However, the cellular functions of PS1 are unknown. We showed predominant localization of PS1 to cell-cell contacts of the plasma membrane in human prostate epithelial tissue and in a human epithelial cell line HEp2 stably transfected with an inducible PS1 construct. PS1 co-immunoprecipitated with beta-catenin from cell lysates of stable transfectants. Conversely, PS1 lacking the PS1-beta-catenin interaction site did not co-immunoprecipitate with beta-catenin and was not recruited to the cell-cell contacts. L cells, which do not form tight intercellular contacts, formed clusters of adhered cells after stable transfection with GFP-PS1 cDNA and demonstrated a clear preference for independent aggregation in the mixed cultures. However, L cells transfected with mutant GFP-PS1 constructs, which had a truncated N-terminus of PS1 or deleted PS1-beta-catenin interaction site, failed to form intercellular contacts. In addition, in primary cultures of mouse cortical neurons PS1 was highly concentrated on the surface of extended growth cones. Taken together, our results suggest an important role of PS1 in intercellular adhesion in epithelial cells and neurons.

Alzheimer Disease↗
PubMed2001

Chemopreventive activity of Withania somnifera in experimentally induced fibrosarcoma tumours in Swiss albino mice.

The current experimental work deals with the chemopreventive studies of a hydroalcoholic extract of Withania somnifera roots, against 20-methylcholanthrene induced fibrosarcoma tumours in Swiss albino mice. A single subcutaneous injection of 200 microg 20-methylcholanthrene in 0.1 mL of dimethylsulphoxide into the thigh region of mice produced a high incidence (96%) of tumours. Oral treatment of animals with 400 mg/kg body weight of Withania somnifera extract (one week before injecting 20-methylcholanthrene and continued until 15 weeks thereafter) significantly reduced the tumour incidence, tumour volume and enhanced the survival of the mice, compared with 20-methylcholanthrene injected mice. The tumour incidence was also delayed in the treatment group when compared with 20-methylcholanthrene injected mice. Liver biochemical parameters revealed a significant modulation of reduced glutathione, lipid peroxides, glutathione-S-transferase, catalase and superoxide dismutase in extract treated mice compared with 20-methylcholanthrene injected mice. The mechanism of chemopreventive activity of Withania somnifera extract may be due to its antioxidant and detoxifying properties.

Administration, Oral↗
PubMed2001

Nested polymerase chain reaction in the diagnosis of congenital cytomegalovirus infection.

OBJECTIVE: Human cytomegalovirus infection is highly prevalent in Indian population. It is the commonest congenitally acquired infection causing various anomalies. The diagnosis of infection in neonates is difficult as IgM may not be detected in all cases. The polymerase chain reaction is reported as alternative and better option in these patients. However, there is lack of data to substantiate this preference in a resource poor country like India. METHODS: Blood samples from 930 neonates/fetuses were first tested for specific anti-CMV IgM antibodies using mu-capture enzyme linked immunosorbent assay, Mac-ELISA. Nested PCR was first standardised on clinically and therapeutically confirmed cases of CMV disease. In the second phase blood samples randomly from 20 babies suspected of CMV infection were collected for serology and PCR and both tests were run independently. Twenty healthy controls were also included. IgM ELISA and PCR were performed on these samples and results of these 20 samples were compared to evaluate the sensitivity and specificity of each method. RESULTS: Out of 930 serum samples of suspected congenital CMV infection 188 (20.2%) were found positive for CMV specific IgM antibodies. While comparing the results of 40 paired samples, PCR was found to be highly specific (100%) but less sensitive than Mac-ELISA (95%) with negative predictive value of 100% and positive predictive value of 95%. Thus in congenital CMV infection Mac-ELISA was less costly, less cumbersome and more user friendly. CONCLUSION: The Mac-ELISA seem to have parallel sensitivity and specificity as PCR for diagnosing congenital CMV infection.

Case-Control Studies↗
PubMed2001

Epidemiological study of congenital heart disease.

A community based survey of congenital heart disease was carried out on a random sample of 11,833 children below 15 years in Delhi, India. Congenital heart disease was diagnosed on clinical history and/or clinical examination. Out of the examined sample, 50 were found suffering from congenital heart disease, giving an overall prevalence of 4.2/1000 (4.6/1000 in boys and 3.7/1000 in girls). The prevalence rate was slightly higher than other studies carried out in the country. The reason is obvious. The present study is community based while other studies were hospital or school based. The type of lesions were similar to those reported from other studies. The lesions in order of frequency were ventricular septal defect (46%), atrial septal defect (18%), patent ductus arteriosus (14%), Fallot's tetrology (10%), aortic stenosis (4%), and pulmonary stenosis (4%). Like other studies ventricular septal defect was the commonest lesion. The prevalence rate was higher in the age group 0-4 years and 5-9 years in boys whereas it was higher in adolescent age group (10-14 years) in girls.

Adolescent↗
PubMed2001

Complete vaginal prolapse: an unusual presentation of anovestibular fistula.

An adolescent girl with an anovestibular fistula presenting as a complete vaginal prolapse and large-bowel obstruction is reported. The prolapse was reduced manually after repeated bowel washouts and a divided high sigmoid colostomy. The patient is awaiting posterior sagittal anorectoplasty. Possible etiopathologic factors of the prolapse are discussed. A vaginal prolapse in a patient with an anorectal malformation has not been reported previously in the English literature.

Adolescent↗
PubMed2001

A comparative study of telomerase activity in sputum, bronchial washing and biopsy specimens of lung cancer.

The potential of telomerase, the ribonucleoprotein enzyme, as a non-invasive screening marker was studied in pre-bronchoscopy sputum (S), bronchial washings (W) and bronchoscopic biopsy (B) samples from individuals under evaluation for lung cancer. Out of the 52 cases studied, 42 were clinically suspected primary lung cancer patients and 10 had pulmonary disorders but had no clinical evidence of lung cancer. Fifteen (39.5%) S samples, 24 (63.1%) W samples and 32 (84.2%) B samples, which were cytologically/histopathologically positive were also positive for telomerase activity. Interestingly, 16 (42%) S samples, 20 (52.6%) W samples and 20 (52.6%) B samples, initially reported cytologically/histopathologically negative, showed detectable telomerase activity. Lung cancer was finally confirmed in these cases by repeat cytology/histopathology. However, telomerase activity was detected in 31 (81.6%) S, 26 (68.4%) W and 33 (86.8%) B samples of suspected lung cancer patients. Telomerase activity was negative in S, W, and B of four of the suspected cases, which ultimately turned out to be negative for lung cancer. Cytopathology/histopathology alone (including repeat attempts) identified 15 (39.5%) cases of sputum, 24 (63.1%) cases of bronchial washings and 32 (84.2%) bronchoscopic biopsy samples. Out of 10 controls, low telomerase activity was detected in only one (10%) of the bronchial washings, which later turned out to be due to large number of inflammatory cells. Telomerase activity assay of sputum carried sensitivity, specificity and diagnostic accuracy of 81.6, 100 and 86.5%, respectively, while that for bronchial washing was 68.4, 100 and 76.9%, respectively, and for bronchoscopic biopsy samples was 86.8, 100 and 88.1%, respectively. A positive correlation (P<0.01) was seen between age and telomerase activity in sputum, bronchial washing and biopsy samples but no significant correlation was seen between sex and telomerase activity or duration of smoking and telomerase activity. A significant positive correlation was observed between staging and telomerase activity in sputum (P<0.01), bronchial washing (P<0.01) and biopsy samples (P<0.01). Our findings indicate that telomerase is a specific marker for malignant lung disease and can complement cytology/histopathology in the diagnosis of lung cancer. Sputum telomerase assay holds the potential for early and non-invasive diagnosis of lung cancer.

Adult↗
PubMed2001

Prognostic value of serum cardiac troponin I in ambulatory patients with chronic renal failure undergoing long-term hemodialysis: a two-year outcome analysis.

OBJECTIVES: We sought to evaluate the prognostic value of cardiac troponin I (cTnI) in asymptomatic, ambulatory patients with chronic renal failure treated with long-term hemodialysis. BACKGROUND: Smaller, short-term follow-up studies on this subject have given conflicting results. METHODS: A total of 126 ambulatory patients with chronic renal failure treated with long-term hemodialysis were followed for two years for all-cause mortality, cardiac mortality, all-cause hospital admissions and cardiac hospital admissions. Serum cTnI was measured before dialysis at the time of study entry. RESULTS: One hundred two patients had normal serum levels of cTnI (< or =0.03 ng/ml) and 24 patients had elevated levels (0.015 +/- 0.007 vs. 0.053 +/- 0.029 ng/ml, p < 0.0001). No significant difference in all-cause mortality (20 vs. 4 deaths), cardiac mortality (4 vs. 1 death), all-cause hospital admissions (1.74 +/- 1.72 vs. 1.25 +/- 1.19 admissions/patient) or cardiac admissions (0.52 +/- 0.89 vs. 0.33 +/- 0.76 admissions/patient) was present between the patients with normal cTnI levels and those with elevated cTnI levels. Serum cTnI was not significantly different between patients who died versus those who survived (0.022 +/- 0.019 vs. 0.022 +/- 0.021 ng/ml). Serum cTnI was not an independent predictor of all-cause mortality, cardiac mortality, all-cause admissions or cardiac admissions. Age (older) and serum albumin (lower) were independent predictors of all-cause mortality, whereas a history of myocardial infarction was an independent predictor of cardiac mortality. Serum sodium (lower) was an independent predictor of all-cause hospital admissions, whereas hypertension and previous myocardial infarction were independent predictors of cardiac admissions. The best predictors of the time to death were age (older) and serum sodium level (lower), irrespective of the serum cTnI levels. CONCLUSIONS: Cardiac troponin I has a limited role in predicting mortality and hospital admissions in asymptomatic patients with chronic renal failure treated with long-term hemodialysis.

Aged↗
PubMed2001

The natural killer T-cell ligand alpha-galactosylceramide prevents autoimmune diabetes in non-obese diabetic mice.

Diabetes in non-obese diabetic (NOD) mice is mediated by pathogenic T-helper type 1 (Th1) cells that arise because of a deficiency in regulatory or suppressor T cells. V alpha 14-J alpha 15 natural killer T (NKT) cells recognize lipid antigens presented by the major histocompatibility complex class I-like protein CD1d (refs. 3,4). We have previously shown that in vivo activation of V alpha 14 NKT cells by alpha-galactosylceramide (alpha-GalCer) and CD1d potentiates Th2-mediated adaptive immune responses. Here we show that alpha-GalCer prevents development of diabetes in wild-type but not CD1d-deficient NOD mice. Disease prevention correlated with the ability of alpha-GalCer to suppress interferon-gamma but not interleukin-4 production by NKT cells, to increase serum immunoglobulin E levels, and to promote the generation of islet autoantigen-specific Th2 cells. Because alpha-GalCer recognition by NKT cells is conserved among mice and humans, these findings indicate that alpha-GalCer might be useful for therapeutic intervention in human diseases characterized by Th1-mediated pathology such as Type 1 diabetes.

Animals↗
PubMed2001

Adenocarcinoma of the uterine cervix compared with squamous cell carcinoma: a 12-year study in Southampton and South-west Hampshire.

In a 12-year study of the population of Southampton and South-west Hampshire (SSWH), there was no rise or fall in the incidence of adenocarcinoma of the uterine cervix, although the incidence of squamous cell carcinoma fell from 14 to 7.2 per 100000 women years and the overall fall in age-adjusted incidence of cervical carcinoma was commensurate with that of England and Wales. The majority (59%) of adenocarcinomas were seen in women aged less than 50, supporting the concept of a higher risk in young women. Screen-detected carcinomas accounted for 50% of adenocarcinomas and 41% of squamous cell carcinomas in women aged 20-64 (the difference was not significant). There were more screen-detected adenocarcinomas of less than 3 mm depth of invasion and 7 mm lateral extension during the third period of the study (1991-1993). The results are consistent with reports of an increased risk of cervical cancer in women born since 1940, and lesser effectiveness of screening in preventing adenocarcinoma compared with squamous cell carcinoma. High prevalence of early screen-detected carcinomas may have been a factor in recent reports of increased incidence of adenocarcinoma.

Adenocarcinoma↗