Biomedical subjects

A K Singh

Publications and source records attributed to A K Singh.

At least 19 recordsLinked to original sources

PubMed2025

Development and validation of a high-density 'Amahysnp' genotyping array in grain amaranth (Amaranthus hypochondriacus).

BACKGROUND: Grain amaranth has recently gained global attention as a promising crop alternative to traditional cereals due to its nutritional value and adaptability to various growing conditions. Although gene banks conserve extensive collections of amaranth germplasm, the genomic and phenotypic characterization of these resources is limited, which hinders their full utilization in breeding programs. A major challenge is the lack of high-throughput genotyping assays essential for comprehensive genomic characterization and trait mapping. High-density SNP arrays have become standard tools for genome-wide analysis across multiple loci, enabling molecular breeding across a range of crop species. RESULTS: In this study, we developed a 64 K high-throughput SNP genotyping array named "AmahySNP", using Affymetrix® Axiom® technology. The array contains 64,069 high-density SNPs distributed across both genic (55.17%) and non-genic (44.83%) regions of the Amaranthus hypochondriacus genome. The genic region includes 8,879 genes, which consist of 4,830 single-copy genes and 4,049 multi-copy genes distributed across 16 scaffolds. These genes cover various functional regions, including exons (10.5%), introns (40.1%), 5'UTRs (1.6%), and 3'UTRs (2.9%), respectively. The AmahySNP array was effectively utilized for population structure analysis, genetic diversity studies, core development, and genome wide association studies (GWAS) in amaranth germplasm. A representative core set of 112 accessions was identified, which includes two released varieties (Annapurna and Suvarna) and 100 diverse accessions from 12 different regions, representing 12% of the total 917 accessions evaluated. Phylogenetic analysis revealed three major genetic clusters, independent of their geographical origins. GWAS conducted using 22,763 polymorphic SNPs from 540 genotypes identified 13 novel loci associated days to flowering (DTF) trait, seven of which were located within annotated genes. CONCLUSIONS: The AmahySNP 64 K SNP chip a valuable genomic tool for amaranth research and breeding with a strong potential to accelerate its genetic improvement. It enables high-throughput genotyping for a wide range of applications, including GWAS and other genomic studies, and will significantly advance the exploration of natural genetic variations. Ultimately, this resource will empower amaranth breeders to develop improved amaranth cultivars with enhanced crop yield, resilience, and nutritional quality, contributing to global food security and sustainable agriculture.

Amaranthus↗

PubMed1999

Status of respiration and ATP content in arsenite resistant Leishmania mexicana amazonensis.

Cellular ATP and rate of respiration are important for the cell survival. We have analyzed both the parameters in wild type and arsenite resistant Leishmania mexicana amazonensis. There was no significant change observed in the rate of respiration and cellular ATP content between drug resistant cells (resistance to 30 microM of sodium arsenite) and wild type cells. Further, we have tested the effect of higher concentrations (i.e. 100 microM and 500 microM) of sodium arsenite on the ATP content of the cells. An elevated level of ATP was observed only in wild type cells after short term exposure (2 h) to 100 microM of the drug, whereas, drug resistant cells initially resist with higher toxic dosage of drug (i.e. 500 microM) but failed to maintain the normal ATP level. In conclusion, respiration and ATP is not a prime event associated with drug resistance in Leishmania. Resistance to metals like arsenic and antimony in Leishmania is multifactorial events.

Adenosine Triphosphatases↗

PubMed1999

Characterization by pulse-field electrophoresis of a new region of DNA amplification containing the M2 subunit of ribonucleotide reductase in hydroxyurea-resistant Leishmania.

An extrachromosomal circular DNA of of approximately 50-kb size was amplified in the hydroxyurea-resistant variant of Leishmania mexicana amazonensis. The amplicon carried the M2 gene of ribonuleotide reductase as part of the gene encoding resistance to hydroxyurea. The amplicon was unstable. It disappeared rapidly as shown in pulse-field gradient electrophoresis gels after reversion of the cells for 20-80 days. This loss of amplified DNA was accompanied by a rapid loss of resistance to hydroxyurea during the same period. The amplicon was not hybridized to specific probes from any of the four regions of DNA amplification previously reported for Leishmania. This region of amplification thus appears to be a new region of DNA amplification in Leishmania.

Animals↗

PubMed1999

Carbamylated proteins activate glomerular mesangial cells and stimulate collagen deposition.

Carbamylated proteins formed in renal insufficiency from the spontaneous decomposition of urea exert a variety of metabolic effects. Here we examined the effects of carbamylated proteins on glomerular mesangial cells to determine whether urea retention in early renal insufficiency may itself promote glomerular sclerosis and hasten the progression to kidney failure. To this effect we carbamylated fetal bovine serum proteins in vitro and tested their effect on mesangial cell proliferation (by tritiated thymidine uptake), de novo protein synthesis (by tritiated leucine uptake), collagen I and collagen IV accumulation (by avidin-biotin enzyme immunoassay), and gelatinase levels in the medium (by zymography and quantitative fluorescence assay). Carbamylated fetal bovine serum at concentrations present in uremia increased tritiated thymidine incorporation by 50% without altering tritiated leucine incorporation, and it increased collagens I and IV in the monolayer by 150% to 300%. Gelatinase activity was unchanged. We conclude that carbamylated proteins can activate mesangial cells to a profibrogenic phenotype. From a clinical perspective, the carbamylation of proteins by elevated urea levels may accelerate the progression to kidney failure and thus set up a vicious cycle in which the nitrogen retention itself would cause further progression of fibrosis and deterioration of kidney function.

Animals↗

PubMed1999

Inhaled corticosteroids for asthma: are ED visits a missed opportunity for prevention?

Inhaled corticosteroids are effective but underused. This study evaluated the outpatient management of emergency department (ED) patients presenting with acute asthma and the relation of inhaled corticosteroid use to the patient's primary care provider (PCP) status. ED patients were interviewed by the hospital's asthma education program staff about their asthma. Overall, 85% (101 of 119) of asthmatics reported having a PCP. Although patients with a PCP and patients without a PCP both were using inhaled beta-agonists (93% v 89%, respectively; P = .54), patients without a PCP were less likely to be using inhaled corticosteroids (49% v 11%, P = .003). Controlling for age, acute asthma severity, and asthma hospitalizations during the past year, PCP status remained a significant predictor of inhaled corticosteroid use (odds ratio = 5.6; 95% confidence interval 1.1 to 27). Even among ED patients with a PCP, inhaled corticosteroids appear to be underused. ED asthma visits present an opportunity to initiate preventive measures such as inhaled corticosteroid use.

Acute Disease↗

PubMed1999

Bicarbonate and chloride secretion in Calu-3 human airway epithelial cells.

Serous cells are the predominant site of cystic fibrosis transmembrane conductance regulator expression in the airways, and they make a significant contribution to the volume, composition, and consistency of the submucosal gland secretions. We have employed the human airway serous cell line Calu-3 as a model system to investigate the mechanisms of serous cell anion secretion. Forskolin-stimulated Calu-3 cells secrete HCO-3 by a Cl-offdependent, serosal Na+-dependent, serosal bumetanide-insensitive, and serosal 4,4'-dinitrostilben-2,2'-disulfonic acid (DNDS)-sensitive, electrogenic mechanism as judged by transepithelial currents, isotopic fluxes, and the results of ion substitution, pharmacology, and pH studies. Similar studies revealed that stimulation of Calu-3 cells with 1-ethyl-2-benzimidazolinone (1-EBIO), an activator of basolateral membrane Ca2+-activated K+ channels, reduced HCO-3 secretion and caused the secretion of Cl- by a bumetanide-sensitive, electrogenic mechanism. Nystatin permeabilization of Calu-3 monolayers demonstrated 1-EBIO activated a charybdotoxin- and clotrimazole- inhibited basolateral membrane K+ current. Patch-clamp studies confirmed the presence of an intermediate conductance inwardly rectified K+ channel with this pharmacological profile. We propose that hyperpolarization of the basolateral membrane voltage elicits a switch from HCO-3 secretion to Cl- secretion because the uptake of HCO-3 across the basolateral membrane is mediated by a 4,4 '-dinitrostilben-2,2'-disulfonic acid (DNDS)-sensitive Na+:HCO-3 cotransporter. Since the stoichiometry reported for Na+:HCO-3 cotransport is 1:2 or 1:3, hyperpolarization of the basolateral membrane potential by 1-EBIO would inhibit HCO-3 entry and favor the secretion of Cl-. Therefore, differential regulation of the basolateral membrane K+ conductance by secretory agonists could provide a means of stimulating HCO-3 and Cl- secretion. In this context, cystic fibrosis transmembrane conductance regulator could serve as both a HCO-3 and a Cl- channel, mediating the apical membrane exit of either anion depending on basolateral membrane anion entry mechanisms and the driving forces that prevail. If these results with Calu-3 cells accurately reflect the transport properties of native submucosal gland serous cells, then HCO-3 secretion in the human airways warrants greater attention.

Benzimidazoles↗

PubMed1999

Study of 222Rn concentrations in some dwellings of Rajasthan.

Total potential alpha energy concentrations due to radon progeny were measured in 143 dwellings of Udaipur, Bikaner, and Banswara towns of Rajasthan province of India with LR-115 type II detectors. The geometric mean values of total potential alpha energy concentrations in these three towns were found to be 1.9 x 10(-7) J m(-3), 1.2 x 10(-7) J m(-3) and 1.7 x 10(-7) J m(-3) with a geometric standard deviation of 2.2, 2.2, and 2.5, respectively. The estimated lifetime risk of lung cancer due to indoor radon exposure for a total population of study area was estimated to be 6.7 x 10(-3) or 0.67%. The mean relative loss of life expectancies were 0.20%, 0.12%, and 0.18%, respectively.

Air Pollutants, Radioactive↗

PubMed1999

Pharmacology of CFTR chloride channel activity.

Pharmacology of CFTR Chloride Channel Activity. Physiol. Rev. 79, Suppl.: S109-S144, 1999. - The pharmacology of cystic fibrosis transmembrane conductance regulator (CFTR) is at an early stage of development. Here we attempt to review the status of those compounds that modulate the Cl- channel activity of CFTR. Three classes of compounds, the sulfonylureas, the disulfonic stilbenes, and the arylaminobenzoates, have been shown to directly interact with CFTR to cause channel blockade. Kinetic analysis has revealed the sulfonylureas and arylaminobenzoates interact with the open state of CFTR to cause blockade. Suggestive evidence indicates the disulfonic stilbenes act by a similar mechanism but only from the intracellular side of CFTR. Site-directed mutagenesis studies indicate the involvement of specific amino acid residues in the proposed transmembrane segment 6 for disulfonic stilbene blockade and segments 6 and 12 for arylaminobenzoate blockade. Unfortunately, these compounds (sulfonylureas, disulfonic stilbenes, arylaminobenzoate) also act at a number of other cellular sites that can indirectly alter the activity of CFTR or the transepithelial secretion of Cl-. The nonspecificity of these compounds has complicated the interpretation of results from cellular-based experiments. Compounds that increase the activity of CFTR include the alkylxanthines, phosphodiesterase inhibitors, phosphatase inhibitors, isoflavones and flavones, benzimidazolones, and psoralens. Channel activation can arise from the stimulation of the cAMP signal transduction cascade, the inhibition of inactivating enzymes (phosphodiesterases, phosphatases), as well as the direct binding to CFTR. However, in contrast to the compounds that block CFTR, a detailed understanding of how the above compounds increase the activity of CFTR has not yet emerged.

Animals↗

PubMed1998

A novel glutathione peroxidase in bovine eye. Sequence analysis, mRNA level, and translation.

Bovine ciliary body contains a selenium-independent glutathione peroxidase (GPX) with a molecular mass of about 100 kDa that is composed of four identical subunits and exhibits no glutathione S-transferase activity. In this study, we isolated cDNA clones and determined the nucleotide sequence to deduce the primary structure of the enzyme. The cDNA contained 672 base pairs encoding a polypeptide with an estimated molecular mass of 25,064 Da. Translation of bovine ciliary mRNA produced a protein which was immunologically indistinguishable from GPX and showed high enzyme activity. The encoded amino acid sequence of the protein was 95% identical with that of a human keratinocyte gene product expressed in response to keratinocyte growth factor. It also showed sequence identity to bacterial alkyl hydroperoxide reductases and thiol specific antioxidant enzymes. GPX mRNA level was highest in the ciliary body, followed by the retina and iris. In various rat organs, the level of GPX mRNA was highest in the lung, followed by the muscle, liver, eye, heart, testis, thymus, kidney, and spleen. A very low level of mRNA was detected in the brain. Enzyme-linked immunosorbent assay with an antibody raised against the NH2-terminal sequence of GPX detected GPX protein in all rat tissues examined.

Amino Acid Sequence↗

PubMed1998

Dialysis therapy.

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Equipment Reuse↗

PubMed1998

Cytokine-mediated induction of ceramide production is redox-sensitive. Implications to proinflammatory cytokine-mediated apoptosis in demyelinating diseases.

The present study underlines the importance of reactive oxygen species in cytokine-mediated degradation of sphingomyelin (SM) to ceramide. Treatment of rat primary astrocytes with tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta led to marked alteration in cellular redox (decrease in intracellular GSH) and rapid degradation of SM to ceramide. Interestingly, pretreatment of astrocytes with N-acetylcysteine (NAC), an antioxidant and efficient thiol source for glutathione, prevented cytokine-induced decrease in GSH and degradation of sphingomyelin to ceramide, whereas treatment of astrocytes with diamide, a thiol-depleting agent, alone caused degradation of SM to ceramide. Moreover, potent activation of SM hydrolysis and ceramide generation were observed by direct addition of an oxidant like hydrogen peroxide or a prooxidant like aminotriazole. Similar to NAC, pyrrolidinedithiocarbamate, another antioxidant, was also found to be a potent inhibitor of cytokine-induced degradation of SM to ceramide indicating that cytokine-induced hydrolysis of sphingomyelin is redox-sensitive. Besides astrocytes, NAC also blocked cytokine-mediated ceramide production in rat primary oligodendrocytes, microglia, and C6 glial cells. Inhibition of TNF-alpha- and diamide-mediated depletion of GSH, elevation of ceramide level, and DNA fragmentation (apoptosis) in primary oligodendrocytes by NAC, and observed depletion of GSH, elevation of ceramide level, and apoptosis in banked human brains from patients with neuroinflammatory diseases (e.g. X-adrenoleukodystrophy and multiple sclerosis) suggest that the intracellular level of GSH may play a critical role in the regulation of cytokine-induced generation of ceramide leading to apoptosis of brain cells in these diseases.

Acetylcysteine↗

PubMed1998

Liposome encapsulated vitamin A compounds exhibit greater stability and diminished toxicity.

Absorption and fluorescence studies of retinol (vitamin A alcohol) and retinol palmitate (vitamin A palmitate) intercalated in phosphatidylcholine (PC) liposomes show that these compounds are bound to the lipid bilayer. It is further found that retinol binds liposomes with greater affinity as compared to retinol palmitate. In addition, the delivery of liposome-incorporated retinoids to the blood has also been studied and it is found that these systems reduce blood viscosity and cause less lysis of red blood cells than retinoid compounds not complexed in liposomes.

Anticarcinogenic Agents↗

PubMed1998

Quantitative analysis of polychlorinated biphenyls, organochlorine insecticides, polycyclic aromatic hydrocarbons, polychlorinated hydrocarbons and polynitrohydrocarbons in spiked samples of soil, water and plasma by selected-ion monitoring gas chromatography-mass spectrometry.

A broad range of pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated hydrocarbons (PCHs), polynitrohydrocarbons (PNHs), polychlorinated biphenyls (PCBs) and organochlorine (OCs) insecticides were simultaneously analyzed in spiked soil, water or plasma samples by using gas chromatography-mass spectrometry (GC-MS). Water and plasma samples containing the pollutants were extracted by a solid-phase extraction (SPE) method using florisil columns. The soil samples, fortified with the toxicants, were extracted with water, methanol or dichloromethane (DCM). The water extract was processed by the SPE method. The methanol and DCM samples were dried, dissolved in acetonitrile and subjected to the SPE extraction. The extracted samples were analyzed by GC-MS programmed to monitor selected ions. The deuterium labelled compounds were used as the internal standards. The chromatographic profile of total ions indicated complete separation of some compounds such as isophorone, naphthalene, all PCBs, most OC insecticides and PNHs; high Mr PAHs and some PCHs were partially or incompletely separated. The chromatographic profile of individual ion indicated good separation of each ion. The minimum detection limit ranged from 1 to 4 pg injected when 1 or 2 ions were monitored or from 20 to 200 pg injected when 20 ions were monitored. The SPE method that provided 60-105% recovery of pollutants from water samples, provided only 2-60% recovery from plasma samples. This may be due to the binding of pollutants to plasma proteins. Water recovered 1-30%, while methanol or DCM recovered 65-100% of the pollutants added to the soil samples. The use of internal standards corrected for the loss of pollutants from plasma or soil.

Environmental Pollutants↗

PubMed1998

Antibodies to pancreatic islet cell antigens in diabetes seen in Southern India with particular reference to fibrocalculous pancreatic diabetes.

Fibrocalculous pancreatic diabetes (FCPD) is a type of diabetes secondary to tropical chronic non-alcoholic pancreatitis. Little is known about the aetiopathogenesis of FCPD. We studied glutamic acid decarboxylase antibodies (GAD-Ab) and islet cell antibodies (ICA) in patients with FCPD and compared the results with Type 1 (insulin dependent) diabetes mellitus, Type 2 (non-insulin-dependent) diabetes mellitus and non-diabetic subjects in Southern India. The prevalence of GAD-Ab was 7.0% (95% Confidence Interval (CI) 1.9-17.2) in FCPD, 47.5% (CI 31.4-64.0) in Type 1 (p < 0.001 compared to FCPD), 5.6% (CI 1.5-13.9) in Type 2 (non-significant (NS) compared to FCPD) and 0% in controls. The prevalence of ICA was 6.3% (CI 1.2-17.4) in FCPD, 53.8% (CI 37.1-70.0) in Type 1 (p < 0.001 compared to FCPD), 9.9% (CI 4.0-19.4) in Type 2 (NS compared to FCPD) and 4.7% (CI 0.4-16.1) in controls. The data suggest that in FCPD, the frequency of auto-antibodies is low and its aetiology is probably not linked to autoimmunity in the majority of the patients.

Adult↗

PubMed1998