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Biomedical subjects

B Singh

Publications and source records attributed to B Singh.

At least 847 records · Page 47Linked to original sources
PubMed1980

T-wave changes with intermittent left bundle branch block.

A 70-year-old woman was found to have an intermittent left bundle branch block. When her electrocardiogram showed normal conduction, T-wave inversions in leads V1-V3 appeared. These alterations suggested an anteroseptal infarction. However, the patient was asymptomatic, and the serum enzymes, technetium 99m pyrophosphate scan, and the thalium 201 scan were all negative. Thus the LBBB itself can produce T-wave in versions in the right precordial leads during the normal conduction phase which may simulate an acute myocardial infarction.

Aged↗
PubMed1980

Radioconglutinin-binding azssay for circulating immune complexes: a new method.

A new method for the detection of circulating immune complexes using radiolabelled conglutinin as a marker for complement-bound complexes precipitated in low concentrations (3.5%) of polyethylene glycol is described. The optimal laboratory conditions for the test have been defined and certain limitations studied. The technique is simple with good reproducibility and high degree of specificity. In a double-blind study of eighty-seven samples of sera from normals, patients with glomerulonephritis, post-renal transplantation, rheumatic diseases, breast tumours, multiple sclerosis and infections the method was compared and correlated to the Clq-binding assay and the Raji cell test. The radioconglutinin-binding assay was most discriminative for cases of glomerulonephritis, renel transplantation, breast carcinoma and multiple sclerosis and least for rheumatoid arthritis.

Antigen-Antibody Complex↗
PubMed1979

Regulation of N-acetylglucosamine uptake in yeast.

Various yeasts have been investigated for their ability to grow on N-acetylglucosamine as the sole carbon source and only those which are associated with the disease, candidiasis, gave positive results. The yeasts unable to grow on N-acetylglucosamine lacked the capacity to transport the aminosugar across the cell membrane. In pathogenic yeasts, two systems of different affinity for substrate were found to operate in the uptake of N-acetylglucosamine. In glucose-grown cells a constitutive, low affinity uptake system was present, but upon addition of inducer, a specific high affinity uptake system was synthesized. Experiments with the inhibitors of macromolecule synthesis suggested that the synthesis of RNA and protein is necessary for induction whereas the synthesis of DNA is not. In glucose-grown Candida albicans cells which are devoid of N-acetylglucosamine enters into the cells as phosphorylated form using a constitutive uptake system. Uranyl acetate (0.01 mM) which binds to cell membrane-associated polyphosphates, inhibited completely the inducible uptake of N-acetylglucosamine. Labelling experiments, designed to determine the temporal sequence of appearance of N-acetylglucosamine in intracellular free sugar and sugar-phosphate pools, indicated that N-acetylglucosamine first appeared in the cells as pohosphorylated form. Similar results were obtained with Saccharomyces phosphorylated form. Similar results were obtained with Saccharomyces cerevisiae 3059 and some other yeasts which are devoid of N-acetylglucosamine kinase in both uninduced and induced conditions. These results are consistent with the model of van Steveninck that involves phosphorylation during transpost. Furthermore, inhibitors of energy metabolism (arsenate, azide and cyanide), proton conductor (m-chlorocarbonylcyanide phenylhydrazine) and dibenzyl diammonium ion (membrane permeable cation) inhibited the inducible N-acetylglucosamine uptake in C. albicans.

Acetylglucosamine↗
PubMed1979

Induction of N-acetylmannosamine catabolic pathway in yeast.

N-Acetylmannosamine kinase activity is absent from yeast cells grown on N-acetylmannosamine. However, other enzymes of the catabolic pathway, namely, N-acetylmannosamine-2-epimerase, N-acetylglucosamine kinase and glucosamine-6-phosphate deaminase are induced. In addition, a high affinity uptake system (permease) for the uptake of N-acetylglucosamine is synthesized under these conditions. The presence of either N-acetylmannosamine or N-acetylglucosamine as inducer is essential for the induced synthesis of these enzymes. The enzyme synthesis stops and their concentration in the cells declines rapidly as soon as inducer is removed from the medium. N-Acetyl-D-galactosamine can also induce all these enzymes except for N-acetylmannosamine-2-epimerase, suggesting the convergence of catabolic pathways for both the aminosugars at N-acetyl-D-glycosamine. Experiments with inhibitors of macromolecule synthesis suggest that the snythesis of RNA and protein is necessary for the induction of these cyzymes whereas the synthesis of DNA is not.

Acetylgalactosamine↗
PubMed1979

Regulation of glucosamine-6-phosphate deaminase synthesis in yeast.

A basal level of glucosamine-6-phosphate deaminase is detected in yeast cells grown on glucose. However, a burst of enzyme production occurs in the presence of N-acetylglucosamine in pathogenic Candida albicans and non-pathogenic Saccharomyces cervisiae. The enzyme synthesis stops and its concentration in the cells declines rapidly as soon as N-acetylglucosamine is removed from the medium. Experiments with RNA- and protein-synthesis inhibitors indicate that the appearance of new enzyme activity is dependent on concomitant new protein synthesis and the inducer operates at a transcriptional level. However, inhibition of DNA synthesis either by hydroxyurea or by mitomycin-C does not impair the synthesis of glucosamine-6-phosphate deaminase.

Acetylglucosamine↗
PubMed1979

Induction of N-acetylglucosamine-catabolic pathway in spheroplasts of Candida albicans.

Synthesis of N-acetylglucosamine-catabolic enzymes, namely permease (high-affinity uptake system), kinase and deaminase was studied in the spheroplasts of the yeast Candida albicans. The presence of N-acetylglucosamine as inducer is essential for the induced synthesis of these enzymes in the spheroplasts, which were active for at least 8--9 h. However, some of the newly synthesized kinase and deaminase leaked out from the spheroplasts into the medium during induction. Experiments with inhibitors of RNA and protein synthesis indicate that the appearance of new enzyme activities is dependent on concomitant new protein synthesis and the inducer operates at a transcriptional level. However, inhibitors of DNA synthesis, e.g. mitomycin-C and hydroxyurea, had no effect on the synthesis of these enzymes.

Acetylglucosamine↗
PubMed1979

A simple reliable system for studying antigen-specific murine T cell proliferation.

Antigen-specific T cell proliferation can be readily elicited from the popliteal lymph node cells of mice which have received immunizations of antigen in the hind footpads. The advantages of our system over other published methods are (i) simplicity in method and materials, (ii) much improved reproducibility, (iii) negligible concomitant B cell proliferation, (iv) large degrees of antigen specific proliferation with very low background, and (v) complete dependence of the response on accessory cells or macrophages. These results were brought about by proper immunization procedures for mice and judicious choice of culture conditions. Our data show that the system is very suitable for the study of macrophage-T cell interaction in the induction of T cell proliferation as well as the genetic basis of responsiveness or non-responsiveness to protein and polypeptide antigens.

Animals↗