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Search Results: 1 - 10 of 212629 matches for " Udai P Singh "
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Hydrogen-bonding and π–π stacking interactions in tris(1,10-phenanthroline-κ2N,N′)nickel(II) bis{[1-tert-butylimidazole-2(3H)-thione-κS]trichloridonickelate(II)} acetonitrile disolvate
Udai P. Singh,Vaibhave Aggarwal
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808018060
Abstract: The asymmetric unit of the title complex, [Ni(C12H8N2)3][NiCl3(C7H12N2S)]2·2CH3CN, consists of one anion, one-half of a cation and one acetonitrile molecule. The NiII atom in the [Ni(phen)3]2+ cation (phen is 1,10-phenanthroline) lies on an inversion centre in an octahedral environment, whereas in the [NiCl3(tm)] anion [tm is 1-tert-butylimidazole-2(3H)-thione], the geometry is distorted tetrahedral. In the crystal structure, intermolecular C—H...Cl hydrogen bonds and π–π stacking interactions (centroid–centroid distance = 3.52 ) lead to the formation of a three-dimensional framework. One of the methyl groups of the tert-butyl group of N-tert-butyl-2-thioimidazole is disordered between two equally populated positions.
Progress in Polycrystalline Thin-Film Cu(In,Ga)Se2 Solar Cells
Udai P. Singh,Surya P. Patra
International Journal of Photoenergy , 2010, DOI: 10.1155/2010/468147
Abstract: For some time, the chalcopyrite semiconductor CuInSe2 and its alloy with Ga and/or S [Cu(InGa)Se2 or Cu(InGa)(Se,S)2], commonly referred as CIGS, have been leading thin-film material candidates for incorporation in high-efficiency photovoltaic devices. CuInSe2-based solar cells have shown long-term stability and the highest conversion efficiencies among all thin-film solar cells, reaching 20%. A variety of methods have been reported to prepare CIGS thin film. Efficiency of solar cells depends upon the various deposition methods as they control optoelectronic properties of the layers and interfaces. CIGS thin film grown on glass or flexible (metal foil, polyimide) substrates require p-type absorber layers of optimum optoelectronic properties and n-type wideband gap partner layers to form the p-n junction. Transparent conducting oxide and specific metal layers are used for front and back contacts. Progress made in the field of CIGS solar cell in recent years has been reviewed.
Progress in Polycrystalline Thin-Film Cu(In,Ga) Solar Cells
Udai P. Singh,Surya P. Patra
International Journal of Photoenergy , 2010, DOI: 10.1155/2010/468147
Abstract: For some time, the chalcopyrite semiconductor CuInSe2 and its alloy with Ga and/or S [Cu(InGa)Se2 or Cu(InGa)(Se,S)2], commonly referred as CIGS, have been leading thin-film material candidates for incorporation in high-efficiency photovoltaic devices. CuInSe2-based solar cells have shown long-term stability and the highest conversion efficiencies among all thin-film solar cells, reaching 20%. A variety of methods have been reported to prepare CIGS thin film. Efficiency of solar cells depends upon the various deposition methods as they control optoelectronic properties of the layers and interfaces. CIGS thin film grown on glass or flexible (metal foil, polyimide) substrates require p-type absorber layers of optimum optoelectronic properties and n-type wideband gap partner layers to form the p-n junction. Transparent conducting oxide and specific metal layers are used for front and back contacts. Progress made in the field of CIGS solar cell in recent years has been reviewed. 1. Introduction Current trends suggest solar energy will play an important role in future energy production [1]. Silicon has been and remains the traditional solar cell material of choice. Although silicon is a highly abundant material, it requires an energy intensive process to purify and crystallize. Furthermore, installations of silicon cells require heavy glass protection plates, which reduce residential applications [2]. Recently, commercial interest is beginning to shift towards thin-film cells [3]. Material, manufacturing time, and weight savings are driving the increase in thin-film cells. Cu(In,Ga)Se2 (CIGS) is one of the most promising semiconductors for the absorber-layer of thin-film solar cells [4]. The conversion efficiency of such cells on glass substrates is approaching 20% [5]. Chalcopyrite-based solar modules are uniquely combining advantages of thin-film technology with the efficiency and stability of conventional crystalline silicon cells. Copper indium gallium selenide (CIGS) solar cells have the highest production among thin film technologies. Advances in preparation and efficiency have allowed these cells to be produced rapidly and are approaching market values for carbon-based energy production [6]. The first report on chalcopyrite-based solar cell was published in 1974 [7]. The cell was prepared from a p-type CuInSe2 (CISe) single crystal onto which a CdS film was evaporated in vacuum. This combination of a p-type chalcopyrite absorber and a wide-gap n-type window layer still is the basic concept upon which current cell designs are based. The typical design,
Synthesis, Characterization and AntitumourActivity of Metal Complexes of 5-Carboxy-2-Thiouracil
Udai P. Singh,Sudha Singh,Sukh Mahendra Singh
Metal-Based Drugs , 1998, DOI: 10.1155/mbd.1998.35
Abstract:
International Conference on Solar Energy Photovoltaics
Udai P. Singh,Bhushan Sopori,Pratima Agarwal,B. Bhattacharya
Conference Papers in Science , 2013, DOI: 10.1155/2013/917045
Abstract:
Activation of Aryl Hydrocarbon Receptor (AhR) Leads to Reciprocal Epigenetic Regulation of FoxP3 and IL-17 Expression and Amelioration of Experimental Colitis
Narendra P. Singh, Udai P. Singh, Balwan Singh, Robert L. Price, Mitzi Nagarkatti, Prakash S. Nagarkatti
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023522
Abstract: Background Aryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family, is well characterized to regulate the biochemical and toxic effects of environmental chemicals. More recently, AhR activation has been shown to regulate the differentiation of Foxp3+ Tregs as well as Th17 cells. However, the precise mechanisms are unclear. In the current study, we investigated the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent AhR ligand, on epigenetic regulation leading to altered Treg/Th17 differentiation, and consequent suppression of colitis. Methodology/Principal Findings Dextran sodium sulphate (DSS) administration induced acute colitis in C57BL/6 mice, as shown by significant weight loss, shortening of colon, mucosal ulceration, and increased presence of CXCR3+ T cells as well as inflammatory cytokines. Interestingly, a single dose of TCDD (25 μg/kg body weight) was able to attenuate all of the clinical and inflammatory markers of colitis. Analysis of T cells in the lamina propria (LP) and mesenteric lymph nodes (MLN), during colitis, revealed decreased presence of Tregs and increased induction of Th17 cells, which was reversed following TCDD treatment. Activation of T cells from AhR+/+ but not AhR -/- mice, in the presence of TCDD, promoted increased differentiation of Tregs while inhibiting Th17 cells. Analysis of MLN or LP cells during colitis revealed increased methylation of CpG islands of Foxp3 and demethylation of IL-17 promoters, which was reversed following TCDD treatment. Conclusions/Significance These studies demonstrate for the first time that AhR activation promotes epigenetic regulation thereby influencing reciprocal differentiation of Tregs and Th17 cells, and amelioration of inflammation.
Prenatal Exposure to TCDD Triggers Significant Modulation of microRNA Expression Profile in the Thymus That Affects Consequent Gene Expression
Narendra P. Singh, Udai P. Singh, Hongbing Guan, Prakash Nagarkatti, Mitzi Nagarkatti
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0045054
Abstract: Background MicroRNAs (miRs) are a class of small RNAs that regulate gene expression. There are over 700 miRs encoded in the mouse genome and modulate most of the cellular pathways and functions by controlling gene expression. However, there is not much known about the pathophysiological role of miRs. TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), an environmental contaminant is well known to induce severe toxicity (acute and chronic) with long-term effects. Also, in utero exposure of fetus to TCDD has been shown to cause thymic atrophy and alterations in T cell differentiation. It is also relevant to understand “the fetal basis of adult disease” hypothesis, which proposes that prenatal exposure to certain forms of nutritional and environmental stress can cause increased susceptibility to clinical disorders later in life. In the current study, therefore, we investigated the effects of prenatal exposure to TCDD on miR profile in fetal thymocytes and searched for their possible role in causing thymic atrophy and alterations in the expression of apoptotic genes. Methodology/Principal Findings miR arrays of fetal thymocytes post exposure to TCDD and vehicle were performed. Of the 608 mouse miRs screened, 78 miRs were altered more than 1.5 fold and 28 miRs were changed more than 2 fold in fetal thymocytes post-TCDD exposure when compared to vehicle controls. We validated the expression of several of the miRs using RT-PCR. Furthermore, several of the miRs that were downregulated contained highly complementary sequence to the 3′-UTR region of AhR, CYP1A1, Fas and FasL. Also, the Ingenuity Pathway Analysis software and database was used to analyze the 78 miRs that exhibited significant expression changes and revealed that as many as 15 pathways may be affected. Conclusions/Significance These studies revealed that TCDD-mediated alterations in miR expression may be involved in the regulation of its toxicity including cancer, hepatic injury, apoptosis, and cellular development.
Resveratrol Prevents Endothelial Cells Injury in High-Dose Interleukin-2 Therapy against Melanoma
Hongbing Guan, Narendra P. Singh, Udai P. Singh, Prakash S. Nagarkatti, Mitzi Nagarkatti
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035650
Abstract: Immunotherapy with high-dose interleukin-2 (HDIL-2) is an effective treatment for patients with metastatic melanoma and renal cell carcinoma. However, it is accompanied by severe toxicity involving endothelial cell injury and induction of vascular leak syndrome (VLS). In this study, we found that resveratrol, a plant polyphenol with anti-inflammatory and anti-cancer properties, was able to prevent the endothelial cell injury and inhibit the development of VLS while improving the efficacy of HDIL-2 therapy in the killing of metastasized melanoma. Specifically, C57BL/6 mice were injected with B16F10 cells followed by resveratrol by gavage the next day and continued treatment with resveratrol once a day. On day 9, mice received HDIL-2. On day 12, mice were evaluated for VLS and tumor metastasis. We found that resveratrol significantly inhibited the development of VLS in lung and liver by protecting endothelial cell integrity and preventing endothelial cells from undergoing apoptosis. The metastasis and growth of the tumor in lung were significantly inhibited by HDIL-2 and HDIL-2 + resveratrol treatment. Notably, HDIL-2 + resveratrol co-treatment was more effective in inhibiting tumor metastasis and growth than HDIL-2 treatment alone. We also analyzed the immune status of Gr-1+CD11b+ myeloid-derived suppressor cells (MDSC) and FoxP3+CD4+ regulatory T cells (Treg). We found that resveratrol induced expansion and suppressive function of MDSC which inhibited the development of VLS after adoptive transfer. However, resveratrol suppressed the HDIL-2-induced expansion of Treg cells. We also found that resveratrol enhanced the susceptibility of melanoma to the cytotoxicity of IL-2-activated killer cells, and induced the expression of the tumor suppressor gene FoxO1. Our results suggested the potential use of resveratrol in HDIL-2 treatment against melanoma. We also demonstrated, for the first time, that MDSC is the dominant suppressor cell than regulatory T cell in the development of VLS.
CXCL10 blockade protects mice from cyclophosphamide-induced cystitis
Sakthivel Senthilkumar K,Singh Udai P,Singh Shailesh,Taub Dennis D
Journal of Immune Based Therapies and Vaccines , 2008, DOI: 10.1186/1476-8518-6-6
Abstract: Background Alterations in serum CXCR3 ligand levels were examined in interstitial cystitis (IC) patients; similar expression patterns in serum as well as CXCR3, CXCR3 ligands, and cytokines expressed by peripheral and local leukocyte subpopulations were characterized during cyclophosphamide (CYP)-induced acute cystitis in mice. Results Serum levels of monokine-induced by interferon-γ (IFN-γ) (MIG/CXCL9), IFN-γ-inducible protein-10 (IP-10/CXCL10), and IFN-γ-inducible T cell α chemoattractant (I-TAC/CXCL11) were elevated in patients with IC. These clinical features closely correlated with CYP-induced cystitis in mice. Serum levels of these CXCR3 ligands and local T helper type 1 (Th1) cytokines were also increased. We demonstrate that CXCR3 as well as CXCL9, CXCL10 and CXCL11 mRNA were significantly expressed by urinary bladder lymphocytes, while CXCR3 and CXCL9 transcripts were significantly expressed by iliac lymph node leukocytes following CYP treatment. We also show that the number of CD4+ T cells, mast cells, natural killer (NK) cells, and NKT cells were increased at systemic (spleen) and mucosal (urinary bladder and iliac lymph nodes) sites, following CYP-induced cystitis in mice. Importantly, CXCL10 blockade attenuated these increases caused by CYP. Conclusion Antibody (Ab)-mediated inhibition of the most abundant serum CXCR3 ligand, CXCL10, in mice decreased the local production of CXCR3 ligands as well as Th1 cytokines expressed by local leukocytes, and lowered corresponding serum levels to reduce the severity of CYP-induced cystitis. The present study is among the first to demonstrate some of the cellular and molecular mechanisms of chemokines in cystitis and may represent new drug target for this disease.
Helper T Cell Epitope-Mapping Reveals MHC-Peptide Binding Affinities That Correlate with T Helper Cell Responses to Pneumococcal Surface Protein A
Rajesh Singh,Shailesh Singh,Praveen K. Sharma,Udai P. Singh,David E. Briles,Susan K. Hollingshead,James W. Lillard Jr
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009432
Abstract: Understanding the requirements for protection against pneumococcal carriage and pneumonia will greatly benefit efforts in controlling these diseases. Several proteins and polysaccharide capsule have recently been implicated in the virulence of and protective immunity against Streptococcus pneumonia. Pneumococcal surface protein A (PspA) is highly conserved among S. pneumonia strains, inhibits complement activation, binds lactoferrin, elicits protective systemic immunity against pneumococcal infection, and is necessary for full pneumococcal virulence. Identification of PspA peptides that optimally bind human leukocyte antigen (HLA) would greatly contribute to global vaccine efforts, but this is hindered by the multitude of HLA polymorphisms. Here, we have used an experimental data set of 54 PspA peptides and in silico methods to predict peptide binding to HLA and murine major histocompatibility complex (MHC) class II. We also characterized spleen- and cervical lymph node (CLN)-derived helper T lymphocyte (HTL) cytokine responses to these peptides after S. pneumonia strain EF3030-challenge in mice. Individual, yet overlapping peptides, 15 amino acids in length revealed residues 199 to 246 of PspA (PspA199–246) consistently caused the greatest IFN-γ, IL-2, IL-5 and proliferation as well as moderate IL-10 and IL-4 responses by ex vivo stimulated splenic and CLN CD4+ T cells isolated from S. pneumonia strain EF3030-challeged F1 (B6×BALB/c) mice. IEDB, RANKPEP, SVMHC, MHCPred, and SYFPEITHI in silico analysis tools revealed peptides in PspA199–246 also interact with a broad range of HLA-DR, -DQ, and -DP allelles. These data suggest that predicted MHC class II-peptide binding affinities do not always correlate with T helper (Th) cytokine or proliferative responses to PspA peptides, but when used together with in vivo validation can be a useful tool to choose candidate pneumococcal HTL epitopes.
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