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R Srivastava

Publications and source records attributed to R Srivastava.

At least 37 records · Page 2Linked to original sources
PubMed2002

Selective identification of new therapeutic targets of Mycobacterium tuberculosis by IVIAT approach.

The in vivo induced antigen technology (IVIAT)(1) has been used for the identification of open reading frames (ORFs) which could be possible therapeutic targets. A recombinant lambdagt11:: Mycobacterium tuberculosis H37Rv expression library was screened with pooled TB patient sera preabsorbed with in vitro grown M. tuberculosis H37Rv. Preabsorption of pooled TB patient sera allowed identification of antigens specifically expressed or upregulated during infection and growth in vivo. Six ORFs were identified, of which four (rv0287, rv2402, rv3878 and rv1045) were of hypothetical functions. Rv0287 is a probable regulatory protein. Rv3878 is present uniquely in M. tuberculosis H37Rv and is a part of RDI deletion region of M. bovis BCG, which includes esat 6 region. This could be exploited as a tool for diagnosis. Two ORFs were assigned function solely on the basis of homology, dnaQ (rv3711c) and lpdA (rv3303c). dnaQ codes for the epsilon subunit of DNA polymerase III, which is responsible for the proofreading activity of the complex. lpdA codes for dihydrolipoamide dehydrogenase, which is a part of many multienzyme complexes such as pyruvate dehydrogenase, keto-acid dehydrogenase and alpha-ketoglutarate dehydrogenase. These two enzymes appear to be potential targets for drug development.

Antigens, Bacterial↗
PubMed2002

Measurement of alpha particle energy using windowless electret ion chambers.

Electret ion chambers are inexpensive, lightweight, robust, commercially available, passive, charge-integrating devices for accurate measurement of different ionizing radiations. In an earlier work a chamber of dimensions larger than the range of alpha particles having aluminized Mylar windows of different thickness was used for measurement of alpha radiation. Correlation between electret mid-point voltage, alpha particle energy, and response was developed and it was shown that this chamber could be used for estimating the effective energy of an unknown alpha source. In the present study, the electret ion chamber is used in the windowless mode so that the alpha particles dissipate their entire energy inside the volume, and the alpha particle energy is determined from the first principles. This requires that alpha disintegration rate be accurately known or measured by an alternate method. The measured energies were within 1 to 4% of the true values for different sources (230Th, 237Np, 239Pu, 241Am, and 224Cm). This method finds application in quantitative determination of alpha energy absorbed in thin membrane and, hence, the absorbed dose.

Americium↗
PubMed2002

Relationships of maternal blood lead and disorders of pregnancy to neonatal birthweight.

Transient complications of pregnancy (anemia, toxemia, proteinuria, arterial hypertension and hyperemesis) were studied in pregnant women from the general population reporting to local hospitals. Comparison of blood lead levels (PbB) was made between women with normal pregnancies and those with complications. Significantly higher PbB were found in women with pregnancy complications as compared to those with normal pregnancies. Increments in the PbB levels were accompanied by statistically significant decrements in neonate birthweights. Complications of pregnancy may be induced by higher PbB and may also compound the adverse effects of decrements of neonate birthweights

Adolescent↗
PubMed2001

Stochastic kinetic analysis of the Escherichia coli stress circuit using sigma(32)-targeted antisense.

A stochastic Petri net model was developed for simulating the sigma(32) stress circuit in E. coli. Transcription factor sigma(32) is the principal regulator of the response of E. coli to heat shock. Stochastic Petri net (SPN) models are well suited for kinetics characterization of fluxes in biochemical pathways. Notably, there exists a one-to-one mapping of model tokens and places to molecules of particular species. Our model was validated against experiments in which ethanol (inducer of heat shock response) and sigma(32)-targeted antisense (downward regulator) were used to perturb the sigma(32) regulatory pathway. The model was also extended to simulate the effects of recombinant protein production. Results show that the stress response depends heavily on the partitioning of sigma(32) within the cell; that is, sigma(32) becomes immediately available to mediate a stress response because it exists primarily in a sequestered, inactive form, complexed with chaperones DnaK, DnaJ, and GrpE. Recombinant proteins, however, also compete for chaperone proteins, particularly when folded improperly. Our simulations indicate that when the expression of recombinant protein has a low requirement for DnaK, DnaJ, and GrpE, the overall sigma(32) levels may drop, but the level of heat shock proteins will increase. Conversely, when the overexpressed recombinant protein has a strong requirement for the chaperones, a severe response is predicted. Interestingly, both cases were observed experimentally.

Antisense Elements (Genetics)↗
PubMed2001

Two animal models of retinal degeneration are rescued by recombinant adeno-associated virus-mediated production of FGF-5 and FGF-18.

The goal of these experiments was to evaluate the potential of the fibroblast growth factor family members FGF-5 and FGF-18 to rescue photoreceptors from cell death in retinal degenerative disease. Two strains of transgenic rats, expressing either a P23H or an S334ter rhodopsin mutation, were used as model systems. The neurotrophic growth factors were delivered by subretinal injection of adeno-associated virus vectors, driving expression of the genes with a constitutive CMV promoter. Morphological and functional analyses were performed to determine whether FGF-5 or FGF-18 overexpression could ameliorate cell death in the retina. Immunocytochemistry was used to determine the cellular sites of expression of the factors and to test for up-regulation of FGF receptors due to injection. Significant rescue from photoreceptor cell death was found after injections of vectors expressing either FGF-5 or FGF-18 in the animal models. Increased survival of photoreceptors did not produce a significant increase in electroretinographic responses, however, reflecting either trauma due to the surgery or a suppression of signaling due to expression of proteins. Three weeks after injections, both growth factors were localized to the inner and outer segments of photoreceptors, and the receptors FGFR1 and FGFR2 were also found to be up-regulated in these regions. No visible pathological changes were seen in the FGF-5- or FGF-18-treated eyes. These results indicate that the delivery of either FGF-5 or FGF-18 with adeno-associated virus protects photoreceptors from apoptosis in transgenic rat models of retinitis pigmentosa and that the rescue is probably mediated by conventional receptor tyrosine kinase pathways in photoreceptors.

Animals↗
PubMed2001

QSAR studies on some antimalarial sulfonamides.

Antimalarial activity of a series of sulfonamide derivatives (2,4-diamino-6-quinazoline sulfonamides) was modeled topologically using Wiener (W)-, and Szeged (Sz)-indices. The regression analysis of the data has shown that better results are obtained in multiparametric regressions upon introduction of indicator parameters. Predicting ability of the models was tested by r(2)(cv) values. It was observed that models based on W index gave slightly better results than those in which Sz is involved.

Animals↗
PubMed2000

Bioluminescent Mycobacterium aurum expressing firefly luciferase for rapid and high throughput screening of antimycobacterial drugs in vitro and in infected macrophages.

The slow growth and highly infectious nature of Mycobacterium tuberculosis is a limiting factor in its use as test organism in high throughput screening for inhibitory compounds. To overcome these problems, use of surrogate strains and reporter genes have been considered. In this study, we have investigated the application of a fast growing nonpathogenic M. aurum expressing firefly luciferase in rapid screening of antituberculosis compounds in vitro and in infected macrophages using bioluminescence assay. The assay is based on luminescence determination using luciferin as substrate. Inhibition of bioluminescence was obtained with frontline antimycobacterial drugs like streptomycin, rifampicin, isoniazid, ethambutol, ofloxacin, and sparfloxacin at their reported MICs. Inhibition could be observed as early as 2 h in vitro and within 24 h in infected macrophages. The system can reliably be used in high throughput screening.

Animals↗
PubMed2000

The results of cardiac retransplantation: an analysis of the Joint International Society for Heart and Lung Transplantation/United Network for Organ Sharing Thoracic Registry.

BACKGROUND: It is well established that repeat heart transplantation has a significantly worse outcome when compared with primary (first time) transplantation. Defining the risk factors for mortality within this group has been difficult due to small numbers of patients at individual centers. METHODS: All cardiac retransplants performed in the United States and registered in the Joint International Society for Heart and Lung Transplantation (ISHLT)/United Network for Organ Sharing (UNOS) Thoracic Registry were analyzed for demographics, morbidity posttransplantation, immunosuppression, and risk factors for mortality. RESULTS: The study cohort included 514 patients of which 81% were male with a mean age of 47+/-12 years. Time from primary transplant to retransplantation ranged from 1 day to 15.5 years and more than 50% of the patients underwent retransplantation for chronic rejection. More than 60% of patients were in the intensive care unit at the time of retransplantation and more than 40% of the patients were reported to be on some form of life support (ventricular assist device, ventilator, and/or inotropic therapy). Survival for the entire retransplant cohort was 65, 59, and 55% for 1, 2, and 3 years, respectively, but was substantially lower when the intertransplant interval was short. Conversely, when the interval between primary and retransplantation was more than 2 years, 1 year survival postretransplantation approached that of primary transplantation. Additional independent risk factors for mortality for the retransplant cohort included overall cardiac transplant center volume, the use of a ventricular assist device or ventilator, the patient being in the intensive care unit, and recipient age. The four most common causes of death were infection, primary/nonspecific graft failure, chronic rejection (allograft vasculopathy), and acute rejection. CONCLUSIONS: The data confirm that repeat heart transplantation is a higher risk procedure than primary transplantation, especially early after the primary heart transplant.

Adult↗
PubMed2000

Dose response to a single intramuscular injection of recombinant adeno-associated virus-erythropoietin in monkeys.

BACKGROUND: Anemia is a significant problem in many disease states. Erythropoietin (Epo) has been used in the treatment of anemia associated with numerous chronic diseases. This study investigates the dose-response profiles of a single intramuscular (im) injection of a recombinant adeno-associated virus vector (rAAV) containing the Epo gene with the goal of achieving a sustained elevation of hematocrit (Hct). METHODS: Cynomolgus (cm) monkeys were given single injections of different doses of rAAV-cm-Epo. The biological effect of Epo gene expression was monitored by determining the Hct levels and circulating hormone levels by ELISA. Antibody to the rAAV capsid protein was also measured over the 41-week period of the experiment. RESULTS: Epo expression was noted only when 2 x 10(11) or more particles were injected. Epo was noted to be increased as soon as 1 week postinjection and was maximum in 6 to 8 weeks. This level of expression remained constant for nearly 20 weeks. Animals given the highest dose of rAAV developed a higher Hct over the first 8 weeks postinjection than those given an intermediate dose. However, the maximum levels of hemoglobin were the same. There was a weak correlation between amount of rAAV injected and capsid antibody response. CONCLUSIONS: AAV vectors are able to transduce skeletal muscle and are capable of achieving sustained expression and systemic delivery of a therapeutic protein following a single im administration. Dose responses to rAAV-Epo are achievable, although a threshold inoculum of virus is necessary to produce an effect and the therapeutic window is narrow.

Anemia↗
PubMed2000

Association of smoking with abnormal exercise heart rate responses and long-term prognosis in a healthy, population-based cohort.

BACKGROUND: Cigarette smoking is associated with chronotropic incompetence, defined as an attenuated heart rate response to exercise. The long-term prognostic implications of this association have not been well explored. SUBJECTS AND METHODS: Adults enrolled in the Lipid Research Clinics' Prevalence Study who had no history of cardiovascular disease and who were not taking beta-blockers were observed for 12 years. Chronotropic incompetence was assessed as the failure to achieve 90% of an age-predicted target heart rate during an exercise test or as a low chronotropic index, a measure of exercise heart rate response adjusted for age, resting heart rate, and physical fitness. RESULTS: Of the 5,354 eligible participants (mean [+/- SD] age of 44 +/- 10 years; 61% male), 1,931 (36%) smoked cigarettes. Smokers were more likely to have a low chronotropic index (26% versus 16%, odds ratio = 1.8, 95% confidence interval [CI] 1.6 to 2.1) and fail to achieve an age-predicted target heart rate (32% versus 22%, odds ratio = 1.7, 95% CI 1.5 to 2.0). Adjustment for standard cardiac risk factors and physical fitness did not affect these associations. During follow-up, there were 327 deaths. Among subjects without chronotropic incompetence, the relative risk of mortality associated with smoking was moderately increased (hazard ratio = 1.8, 95% CI 1.3 to 2.3); among smokers with chronotropic incompetence, the relative risk of mortality was markedly increased (hazard ratio = 2.7, 95% CI 2.0 to 3.7, P for interaction = 0.02). CONCLUSIONS: In this large, middle-aged population-based cohort, smoking was associated with chronotropic incompetence, which in turn identified smokers with a particularly high mortality rate.

Adult↗
PubMed2000

Antisense downregulation of sigma(32) as a transient metabolic controller in Escherichia coli: effects on yield of active organophosphorus hydrolase.

Plasmids containing an antisense fragment of the sigma(32) gene were constructed and introduced into Escherichia coli cells. Downregulation of the sigma(32)-mediated stress response was evaluated under heat shock and ethanol stress and during the production of organophosphorus hydrolase (OPH). Northern blot analyses revealed that sigma(32) sense mRNA was virtually undetected in antisense-producing cultures from 5 to 20 min after antisense induction. However, lower-molecular-weight bands were found, presumably due to partial degradation of sigma(32) mRNA. While a >10-fold increase in sigma(32) protein level was found under ethanol stress in the control cultures, antisense producing cultures resulted in a <3-fold increase, indicating downregulation of sigma(32). Correspondingly, antisense synthesis resulted in a decreased level of a sigma(32) regulated chaperone (GroEL) for the first 2 h after induction relative to control cultures without sigma(32) antisense mRNA. The total yield of OPH in the presence of sigma(32) antisense was, on average, 62% of the yield without antisense. However, during sigma(32) antisense production, a sixfold-higher specific OPH activity was observed compared to non-antisense-producing cultures.

Aryldialkylphosphatase↗
PubMed2000

Identification of human lung and skin proteins conjugated with hexamethylene diisocyanate in vitro and in vivo.

Diisocyanates are asthma-causing chemicals used in the commercial production of polyurethane. We have previously shown that human lung epithelial cell proteins can become conjugated with hexamethylene diisocyanate (HDI) and may be biologically important in diisocyanate-induced asthma. The objective of this study was to identify specific human lung and skin proteins that become conjugated with diisocyanate after in vitro and in vivo exposure. Following in vitro exposure of human airway epithelial cells (A549), keratin 18, the 78-kD glucose-regulated protein, trans-1, 2-dihyrobenzene-1,2-diol dehydrogenase, and actin were identified as prominent diisocyanate-conjugated proteins through use of a combination of immunocytochemical and mass spectrometric techniques. Following in vivo inhalation of an HDI aerosol, keratin 18 was also identified as the predominant diisocyanate-conjugated protein in human endobronchial biopsy samples, whereas albumin was the predominant diisocyanate-conjugated protein in bronchoalveolar lavage fluid. Keratin was also identified as a predominant diisocyanate-conjugated protein in human skin biopsy samples after epicutaneous exposure to liquid-phase HDI, although the major skin diisocyanate-conjugated protein (56-kD) differed from the predominant lung diisocyanate-conjugated keratin (47-kD). The data from this study identify keratin and other proteins as potential "carriers" for diisocyanates in vivo, and suggest that HDI conjugation of these proteins may play a role in the pathogenesis of diisocyanate-induced asthma.

Adult↗
PubMed1999

Strain specific effects of cytomegalovirus on endothelial cells: implications for investigating the relationship between CMV and cardiac allograft vasculopathy.

BACKGROUND: Cytomegalovirus (CMV) has been associated with the development of chronic allograft rejection. Attempts to delineate pathogenetic mechanisms for this association have characteristically used well-established laboratory strains for in vitro investigation and rodent strains for in vivo studies. There is substantial genetic heterogeneity not only among different laboratory strains, but also between laboratory strains and clinical isolates, and genetic differences between human and animal strains are profound. Given these genetic differences, one would anticipate differences in biological activity between strains. METHODS: Vascular endothelial cells were infected with two laboratory strains of CMV (Towne and AD-169) as well as two individual clinical CMV isolates, after genetic typing with six segments of the genome (including early and late genes). mRNA expression coding for a panel of mesenchymal growth factors was studied using quantitative reverse transcription, polymerase chain reaction. Major histocompatibility complex (MHC) expression was investigated using flow cytometry. RESULTS: There was substantial genetic variability between clinical and laboratory isolates. There did not appear to be differences in overall infectivity by the different strains as determined by expression of immediate-early antigen at 24 hours (5-10% of endothelial cells positive for immediate-early. Two growth factors, platelet-derived growth factor-A and basic fibroblast growth factor were augmented by one of the two clinical strains of CMV (Clin 2) (P=0.0091 and P=0.0018, respectively). Transforming growth factor -alpha and insulin-like growth factor expression were significantly reduced by both clinical strains and AD-169. Two other growth factors, heparin-binding epidermal growth factor and transforming growth factor-beta were not altered by infection with any strain. No strain altered MHC class II expression. MHC class I expression was increased with one of the two clinical strains (Clin 1, P=0.0006) and decreased by AD-169 (P=0.0016). Clin 2 and Towne had no effect on MHC class I expression. CONCLUSIONS: These data demonstrate that the genetic heterogeneity of CMV is associated with differences in transplant-relevant biologic activity even among clinical isolates. The relationship between CMV and chronic rejection may be difficult to determine given the heterogeneous nature of this complex virus.

Antigens, Viral↗
PubMed1999

Cell surface expression of HLA-E: interaction with human beta2-microglobulin and allelic differences.

The formation of a trimeric complex composed of MHC class I heavy chain, beta2-microglobulin (beta2m) and peptide ligand is a prerequisite for its efficient transport to the cell surface. We have previously demonstrated impaired intracellular transport of the human class Ib molecule HLA-E in mouse myeloma X63 cells cotransfected with the genes for HLA-E and human beta2m (hbeta2m), which is most likely attributable to inefficient intracellular peptide loading of the HLA-E molecule. Here we demonstrate that cell surface expression of HLA-E in mouse cells strictly depends on the coexpression of hbeta2m and that soluble empty complexes of HLA-E and hbeta2m display a low degree of thermostability. Both observations imply that low affinity interaction of HLA-E with beta2m accounts to a considerable extent for the observed low degree of peptide uptake in the endoplasmic reticulum. Moreover, we show that the only allelic variation present in the caucasoid population located at amino acid position 107 (Gly or Arg) greatly affects intracellular transport and cell surface expression upon transfection of the respective alleles into mouse cells. No obvious difference was found with regard to the sequence of the peptide ligand.

Alleles↗
PubMed1999

Vitamin A administered with measles vaccine to nine-month-old infants does not reduce vaccine immunogenicity.

After a report of reduced seroconversion to measles in infants, aged 6 mo, given vitamin A with their measles vaccination, serious concerns were raised regarding the safety of the WHO's recommendation that infants be supplemented with vitamin A at the time of measles immunization. To determine the impact of coadministered vitamin A on the antibody response to measles vaccine given to infants aged 9 mo, the more common age for immunization in developing countries, we conducted a randomized, double-blind, placebo-controlled trial in an urban slum community in Delhi. Infants (618) were randomly allocated to receive 30 mg vitamin A or a placebo with the measles immunization. Antibodies to measles were measured by ELISA in serum samples obtained at before (baseline) and 12 wk after immunization. Overall, the seroconversion rates did not differ between vitamin A (89.5%) and placebo (87.6%) groups. There were no significant differences in the geometric mean titers in the two groups (ratio of geometric means, 1.19; 95% confidence interval, 0.97-1.46). Among malnourished infants, the geometric mean titer was significantly greater in the vitamin A group compared to the placebo group (ratio of geometric means, 1.57; 95% confidence interval, 1. 18-2.0), but seroconversion rates did not differ. There were no differences in seroconversion rates and geometric mean titers in the two study groups among the well-nourished children. These results indicate that 30 mg vitamin A does not reduce the immune response to the coadministered vaccine and, therefore, can be continued to be given safely in public health programs.

Antibody Formation↗