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Biomedical subjects

A Mishra

Publications and source records attributed to A Mishra.

At least 127 records · Page 7Linked to original sources
PubMed1993

Human T-helper cell responses to a synthetic peptide derived from the hepatitis B surface antigen.

Hepatitis B virus surface antigen peptide OS (aa124-147) self oligomerizes to form conformational B-cell immunogen with several properties of a candidate peptide vaccine. It gives a T-cell blastogenic response in vaccinated as well as naturally infected individuals. To study the nature and localization of the T-helper cell epitopes, the T-lymphocyte proliferative responses in humans exposed to hepatitis B surface antigen (HBsAg) were examined with a synthetic peptide representing residues 124-147 of this antigen [peptide OS (aa24-147)]. Positive responses were obtained in most cases regardless of whether HBsAg exposure was due to vaccination or a hepatitis B viral infection. Epitope localization studies with truncated peptides indicated the presence of more than two HBsAg-relevant T-helper cell epitopes. This was also corroborated by our fine mapping studies which revealed that the amino acid residues crucial for eventual T-helper cell activation were diverse amongst the various individuals. Together these studies suggest that immunization with peptide OS (aa124-147) may result in an HBsAg cross-reactive T-helper cell response in a broad spectrum of the human population.

Amino Acid Sequence↗
PubMed1992

Mechanism of enhanced phagocytic response in protein a treated rat macrophages.

Protein A of S. aureus Cowan I has been shown to stimulate macrophage mediated phagocytosis. The present study was undertaken to understand the mechanism involved in the enhancement of phagocytosis of peritoneal macrophages by protein A. The lucigenin and luminol-dependent chemiluminescence (CL) of rat peritoneal macrophages, after incubation with various concentrations of protein A, flow-cytometric studies using DCFH-DA as a fluorescent compound and phagocytosis of sheep red blood cells (SRBCs) by rat peritoneal macrophages were studied. A significant increase in lucigenin dependent CL due to formation of superoxide anions (O2-.) and in luminol dependent CL due to formation of hydrogen peroxide (H2O2) was observed in protein A treated macrophages. A significant increase in intracellular hydrogen peroxide (H2O2) was also observed along with an increase in phagocytosis of SRBCs by protein A treated macrophages. The present findings indicate that protein A helps to increase phagocytosis and triggers respiratory burst of macrophages. Thus, both increased phagocytic response and respiratory burst of macrophages in protein A treated animals may be contributing to the antitumor property of protein A reported earlier.

Acridines↗
PubMed1992

Immune response to hepatitis B virus surface antigen peptides during HBV infection.

Antibody responses of patients with acute (n = 73), fulminant (n = 30) and chronic (n = 51) hepatitis B virus (HBV) infection as well as recovered individuals (n = 7) were studied against three synthetic peptides, Pre-S1 amino acids (aa. 12-32), Pre-S2 amino acids (aa. 120-145), and S amino acids (aa. 124-147) of the envelope region (HBsAg). T cell blastogenic response was investigated in a proportion of the patients (27 acute, nine fulminant, 13 chronic hepatitis and seven recovered individuals) along with seven HBV vaccinated and three normal individuals. The presence of T cell response against S peptide was observed in all the cases (9/9, 100%) during early acute hepatitis. This was suppressed during late stages (8/18, 44%) followed by partial reversal during recovery (5/7, 71%). T cell response and antibodies to Pre-S1 and Pre-S2 peptides were present only in one-third of the patients throughout these periods. The T cell blastogenic response as well as antibody reactivity against these peptides were absent and minimal in chronic hepatitis. Immune response against envelope protein appears to play a major role in acute hepatic injury due to HBV infection and help in virus clearance.

Acute Disease↗
PubMed1991

Characterization of a set of variable number of tandem repeat markers conserved in bovidae.

Screening purpose-built libraries with minisatellite probes, we have isolated 36 bovine variable number of tandem repeat markers (VNTRs) characterized by a mean heterozygosity of 59.3 within the American Holstein breed. Matching probabilities and exclusion powers were estimated by Monte-Carlo simulation, showing that the top 5 to 10 markers could be used as a very efficient DNA-based system for individual identification and paternity diagnosis. The isolated VNTR systems should contribute significantly to the establishment of a bovine primary DNA marker map. Linkage analysis, use of somatic cell hybrids, and in situ hybridization demonstrate that these bovine VNTRs are scattered throughout the bovine genome, without evidence for proterminal confinement as in the human, and that at least some of them are organized as clusters. Moreover, Southern blot analysis and in situ hybridization demonstrate conservation of sequence and map location of minisatellites within Bovidae.

Animals↗
PubMed1991

Idiopathic oedema--a missed entity.

Twenty nine patients were diagnosed to have idiopathic oedema; 27 (93.1%) of these were females. Associated psychological symptoms were observed in 86.2% of patients. The most common associated symptoms were related to autonomic dysfunction. Obesity and diuretic abuse were found in 48.3% and 41.4% of patients respectively. The association of bizarre symptoms with idiopathic oedema is a common feature.

Adult↗
PubMed1991

Human natural antibodies to Culex quinquefasciatus: age-dependent occurrence.

The titer of anti-Culex quinquefasciatus antibodies which were mostly of IgG and IgE isotypes was determined in humans living in Wuchereria bancrofti endemic regions. A progressive increase in the titer of antibodies was observed with age. In contrast, sera from people living in regions where the Cx. quinquefasciatus is of low prevalence were found to have markedly reduced IgG and almost zero IgE levels.

Adolescent↗
PubMed1990

Reactivity of Cryptococcus neoformans & Candida species with concanavalin A & blood grouping sera.

Forty strains of Cryptococcus neoformans, 30 of Candida albicans, 24 of C. parapsilosis and 10 strains each of C. tropicalis and C. (Torulopsis) glabrata were examined. A 0.2 per cent solution of concanavalin A (Con A) in phosphate buffered saline and commercial anti-A and anti-B blood grouping sera were used in the whole cell slide agglutination test. All the isolates of Candida species strongly reacted with Con A and over 90 per cent were agglutinated by anti-A and -B blood grouping sera. In contrast, except for one strain, Cryptococcus neoformans did not agglutinate with Con A or blood grouping sera. These findings suggest, on one hand, a fundamental difference in the sugar mosaic of the cell surface components of Cryptococcus neoformans and Candida species, and on the other, presence of similar antigenic determinant(s)/receptors on the cell surface of Candida species and human erythrocytes.

Agglutination Tests↗
PubMed1989

Antithrombotic effect of thiopurinol.

Antithrombotic activity of ten pyrazolo pyrimidine derivatives was tested in mouse pulmonary thromboembolism model. Out of these compounds, Thiopurinol (C5H4N4S) showed dose-dependent protection in mice from death/paralysis induced by collagen + adrenaline. It also caused dose-dependent inhibition of thrombus formation in the cat. Thiopurinol inhibited aggregation of platelets induced by ADP and arachidonic acid but did not inhibit superoxide generation. It had no antiinflammatory activity nor any effect on cardiovascular system. The results indicate that the antithrombotic activity of the compound is mediated via inhibition of platelet aggregation.

Allopurinol↗