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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↗
PubMed1992

Phytanic acid alpha-oxidation in human cultured skin fibroblasts.

We studied the oxidation of [1-14C]phytanic acid, 3-methyl substituted fatty acid, to pristanic acid and 14CO2 in human skin fibroblasts. The specific activity for alpha-oxidation of phytanic acid in peroxisomes was 29- and 124-fold higher than mitochondria and endoplasmic reticulum. This finding demonstrates for the first time the presence of fatty acid alpha-oxidation enzyme system in peroxisomes.

Cell Fractionation↗
PubMed1992

Quantitative analysis of inositol lipids and inositol phosphates in synaptosomes and microvessels by column chromatography: comparison of the mass analysis and the radiolabelling methods.

Chromatographic methods that measure both the mass and the radiolabelling of various inositol lipids and inositol phosphates in tissues have been developed. The mass of phosphatidylinositol (PtdIns), phosphatidylinositol-4-monophosphate [PtdIns(4)P] and phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] was quantitated by measuring the inorganic phosphate, whereas inositol monophosphate (IP), inositol bisphosphate (IP2), inositol trisphosphate (IP3) and inositol tetrakisphosphate (IP4) were quantitated by using an enzymic method. The radiolabelling of various inositol lipids and inositol phosphates was determined by incubating the tissue samples with [3H]myo-inositol, separating individual inositol lipids and inositol phosphates, and measuring the radioactivity in each compound. Although the mass analysis method was sensitive enough to measure low levels of inositol lipids or inositol phosphates, the method was laborious and time-consuming. Compared with the enzymic method, the radiolabelling method was simple and fast, but it gave variable results. This study demonstrated differences in inositol lipid and inositol phosphate levels by radiolabelling and mass measurements, and agonist-stimulated phosphatidylinositol turnover of synaptosomes versus the blood-brain barrier as represented by microvessels. Although the mass of PtdIns, PtdIns(4)P and PtdIns(4,5)P2 was comparable in synaptosomes and microvessels, the incorporation of [3H]myo-inositol into phosphorylated PtdIns in microvessels was less than that in synaptosomes.

Animals↗
PubMed1992

Proteolytic machinery of glomerular epithelial cells against IgG.

Accumulation of immune complexes in the subepithelial region of the glomerular basement membrane results in the lesion of membranous nephropathy. The inefficient handling of immune complexes by the glomerular epithelial cell was investigated by studying the mechanism of IgG proteolysis by the intracellular proteases of cultured epithelial cells. Radiolabelled IgG was incubated with extracts of cells and the digestion of IgG was monitored by SDS-PAGE analysis. Prolonged incubation of IgG with the cell extracts resulted in only partial degradation of the IgG. The enzyme responsible for the breakdown was determined to be the lysosomal cathepsin D based on the pH optimum and the presence of aspartate in the active site of the enzyme. SDS-PAGE analysis of the digestion fragments revealed that a large proportion of the incompletely degraded IgG was the (Fab)2 fragment, which was resistant to further proteolysis. This could be one of the possible explanations for the slow removal of IgG from the subepithelial location of the basement membrane.

Animals↗
PubMed1992

Ischemia-reperfusion injury: biochemical alterations in peroxisomes of rat kidney.

Exogenously supplied catalase, a peroxisomal enzyme, has been found to be of therapeutic value in ischemic injury. Therefore, we examined the effect of ischemic-reperfusion injury on the structure and function of kidney peroxisomes. Ischemic injury changed the density of peroxisomes from 1.21 g/cm3 (peak I) to a lighter density of 1.14 g/cm3 (peak II). The number of peroxisomes moving from the normal density population (peak I) to a lower density population (peak II) increased with an increase in ischemic injury. Latency experiments indicated both populations of peroxisomes to be of intact peroxisomes. Immunoblot analysis with antibodies against peroxisomal matrix and membrane proteins demonstrated that after 90 min of ischemia a significant number of matrix proteins were lost in the peak II population, suggesting that functions of these peroxisomes may be severally affected. Reperfusion following ischemic injury resulted in loss of peroxisomal matrix proteins in both peaks I and II, suggesting that peroxisomal functions may be drastically compromised. This change in peroxisomal functions is reflected by a significant decrease in peroxisomal catalase activity (35%) and beta-oxidation of lignoceric acid (43%) observed following 90 min of ischemia. The decrease in catalase activity was more pronounced in reperfused kidneys even after a shorter term of ischemic injury. Reperfusion restored the normal peroxisomal beta-oxidation in kidneys exposed up to 60 min of ischemia. However, 90 min of ischemia was irreversible as there was a further decrease in beta-oxidation upon reperfusion. The decrease in catalase activity during ischemia alone was due to the formation of an inactive complex, whereas during reperfusion, following 90 min of ischemia, inactivation and proteolysis or decreased synthesis of catalase contributed equally toward the injury. The observed changes in the structure and function of peroxisomes as a result of ischemic-reperfusion injury and the ubiquitous distribution of peroxisomes underlines the importance of this organelle in the pathophysiology of vascular injury in general.

Animals↗
PubMed1992

Interaction of polycations with cell-surface negative charges of epithelial cells.

The interaction between various polycations and cultured glomerular epithelial cells was studied by cell electrophoresis. It was shown that the glomerular epithelial cell presents a negatively charged surface which imparts a zeta potential of -29.0 +/- 1.5 mV at the peripheral layer of the plasma membrane. The pH at which the GEC charge became 50% reduced (pKa) was determined to be 3.0. A variety of polycations of various sizes and fixed and flexible geometries were tested for their capacity to neutralize the cell charge. All the polycations except cytochrome c and lysozyme were capable of completely neutralizing the cell. Cytochrome c could maximally neutralize only 50% of charge and lysozyme only 72% of charge. However, reduced and 'relaxed' molecules of cytochrome c and lysozyme efficiently neutralized the cell surface, as did larger sized 'flexible' polylysines. On the basis of these findings, we conclude that all polycations are not equal in their capacity to neutralize the cell surface. Flexible molecules in contrast to molecules with rigid structures were more effective in neutralizing the cell. This may likely be due to the exposure and availability of more cationic groups in a flexible molecule which results in stabilization of interaction with cells.

Animals↗
PubMed1992

Demonstration of Cu-Zn superoxide dismutase in rat liver peroxisomes. Biochemical and immunochemical evidence.

In this study, by using highly purified rat liver peroxisomes, we provide evidence from analytical cell fractionation, Western blot, and immunocytochemical analysis that Cu-Zn superoxide dismutase is present in animal peroxisomes. Treatment with ciprofibrate, a peroxisome proliferator, increased the peroxisomal superoxide dismutase activity by 3-fold with no effect on mitochondrial activity but a marked decrease in cytosolic superoxide dismutase activity, further supporting that besides cytosolic and mitochondrial localization, Cu-Zn superoxide dismutase is present in peroxisomes also. Demonstration of superoxide dismutase in peroxisomes suggests a new role for this organelle in pathophysiological conditions, such as ischemia-reperfusion injury.

Animals↗
PubMed1992

Long-term results of St. Jude Medical valve in the tricuspid position.

Little is known of the St. Jude Medical heart valve's long-term clinical performance in the tricuspid position. Fourteen patients underwent tricuspid valve replacement between 1981 and 1984. Ages of the patients ranged from 32 to 81 years. Eight patients (68%) were in New York Heart Association class IV preoperatively. Twelve patients had other concomitant cardiac operations. One patient (8%) died within 30 days after operation, due to cerebrovascular accident. Postoperatively, all patients were anticoagulated with warfarin sodium and showed improvement in functional class. There were no mechanical valve failures or thromboses in patients on the anticoagulation regimen. Follow-up in all patients extended over 7 to 10 years with a mean of 8 years. There were six late deaths unrelated to valve function. The actuarial survival curve with these patients is 50% over 10 years. In conclusion, the St. Jude Medical valve is a good mechanical substitute in the tricuspid position, and we recommend its use when reconstruction is not possible and there is no contraindication for anticoagulation.

Adult↗
PubMed1992

Impact on the management and delivery of primary health care by a computer-based information system.

Timely and accurate information forms the basis for management to plan and for care providers to take appropriate action. We report from a developing country a research project aimed to strengthen the information infrastructure with a computer at a Primary Health Centre. The software (MCHS) was designed to assist the care providers in the information management for the Maternal and Child Health (MCH) programme activities. In Phase I, a baseline survey was conducted to identify the needs and target groups. In Phase II, the MCHS was integrated into routine delivery of MCH to monitor the target population and help in evaluation. The research project's impact is reflected in enhanced utilization of services and quality in care, as seen by reduction of dropouts from the immunization program. In economic terms, we see that the costs for a fully immunised child are reduced with reduction of dropouts; thus, the computer system contributes to quality assurance and cost effectiveness in delivery of care.

Adolescent↗
PubMed1992

A rare presentation of posterior communicating artery aneurysm.

This is a report of a successfully treated case of a 55-year-old woman with posterior communicating artery aneurysm who had a partial 3rd nerve palsy with pupillary sparing, temporal lobe intracerebral hematoma and a subdural hematoma. Such an association has not been reported earlier.

Carotid Artery Diseases↗
PubMed1992

Cytokines play a central role in the pathogenesis of systemic lupus erythematosus.

Excessive production of pathogenic autoantibodies is one of the hallmarks of systemic lupus erythematosus (SLE). The mechanisms that underlie this excessive production are still unclear. Although there is considerable evidence to suggest that both T cells and B cells play an important role in the etiology of SLE, convincing abnormalities at the T cell receptor or immunoglobulin gene loci have not been demonstrated. In this regard, because cytokines play such a pivotal role in the inflammatory response, a defect in the immunoregulation of B cells by cytokines should be considered as possible contender in disease etiology. The hypothesis that is proposed here is that multiple defects mediated by cytokines are present in individuals with lupus and that both cytokine production and the response of B cells to cytokines may be defective. These abnormalities could then be a central factor in the etiology of systemic lupus erythematosus.

Animals↗
PubMed1992

Screening and confirmation of drugs in urine: interference of hordenine with the immunoassays and thin layer chromatography methods.

Hordenine cross-reacted with various enzyme linked immunosorbent assay (ELISA) or radioimmunoassay (RIA) kits used for the screening of urine samples. Morphine-ELISA kit was most sensitive, whereas etorphine- and buprenorphine-ELISA kits were least sensitive to hordenine cross-reactivity. Hordenine also interfered with the thin layer chromatography of oxymorphone, hydromorphone and apomorphine. The major source of hordenine in humans is beer brewed from barley, whereas the major source of hordenine in horses is canary grass or barley. Therefore, the presence of hordenine in the urine of humans consuming beer or in the urine of horses consuming canary grass may give false positive values when the immunoassay and TLC methods are used for the screening of the urine sample. In order to distinguish hordenine from the opiate drugs, simple and sensitive gas chromatographic/mass spectrometric (GC/MS) and high performance liquid chromatographic (HPLC) methods have been developed in this study.

Alkaloids↗
PubMed1992

Aortic valve replacement (AVR): influence of age on operative morbidity and mortality.

Retrospective analysis of 306 patients following aortic valve replacement (AVR) was carried out between 1985-89. Patients were divided into two groups: group 1 patients were less than 70 years of age and group 2 were greater than 70 years of age. The multivariant analysis of risk factors showed the only increased risk for surgery was the NYHA class IV in either group. There was no overall difference in morbidity and mortality. The actuarial survival rate for group 2 patients was 95% at 1 year and 75% at 5 years. This was not different when compared for death in age- and sex-matched controls from the general population. AVR in the elderly is safe, the long-term result is good and it remains the treatment of choice unless there is an absolute contraindication.

Age Factors↗
PubMed1992

Cord compression: a rare complication of chronic lymphocytic leukaemia.

Two years after the diagnosis, while the disease was under good control, a patient with chronic lymphocytic leukaemia (CLL) developed spinal cord compression from an extradural solid tumour composed of leukaemic cells. He was treated successfully with resection of the tumour followed by local radiotherapy and systemic chemotherapy.

Acute Disease↗
PubMed1992

Bone marrow necrosis at transformation of chronic granulocytic leukaemia treated with interferon.

A patient with chronic myeloid leukaemia was treated with interferon without using conventional cytotoxic agents. Bone marrow necrosis developed at the onset of blast transformation. It is suggested that cytotoxic drugs should be given before treatment with interferon for chronic myeloid leukaemia. Cytotoxic drugs may also be needed to prevent rapid bone marrow growth once interferon has been withdrawn.

Antineoplastic Agents↗
PubMed1992

The occurrence of long chain polyprenols in leaves of plants of Rosaceae family and their isolation by time-extended liquid chromatography.

The long chain polyprenols composed of 30 and more isoprene units from leaves of plants belonging to the genera Potentilla and Rosa have been described. They occur in the form of fatty acid esters. The composition of polyprenol mixture was species dependent and its content reached ca. 0.5% wet weight. Large scale preparation of individual polyprenols from a natural polyprenol mixture was performed using time-extended liquid chromatography on the hydrophobic gel Lipidex-5000.

Chromatography, Liquid↗
PubMed1992

Complementation in Zellweger syndrome: biochemical analysis of newly generated peroxisomes.

The Zellweger syndrome is characterized by a defect which results in the abnormal biogenesis of peroxisomes. As a consequence, metabolic activities associated with peroxisomes such as the oxidation of very long chain fatty acids, the synthesis of plasmalogens, and the catabolism of phytanic and pipecolic acids are impaired. Since this disorder is genetically heterogeneous and several complementation groups are known, we were able to study the normalization of peroxisomal activity during the process of complementation. The restoration of catalase and dihydroxyacetone phosphate acyltransferase activities peaked within 3-4 days postfusion while the oxidation of lignoceric acid was much delayed (7-8 days). Electron microscopy indicated that by 6 days following hybridization, peroxisome structure and density in heterokaryons was comparable to normal control cells. The heterogenous biochemical response during peroxisome normalization could be due to several factors including a possible requirement for restoration of peroxisomal structural integrity for maximum activation of certain metabolic pathways.

Acyltransferases↗