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Biomedical subjects

A Chakraborty

Publications and source records attributed to A Chakraborty.

At least 109 records · Page 6Linked to original sources
PubMed1993

Temporal variation in the distribution of rotavirus electropherotypes in Delhi, India.

The present study was carried out to investigate the varying pattern of rotavirus electropherotypes in Delhi, India. During a 25-month study period, rotavirus was detected in 104 of 990 (10.5%) samples collected from children with acute gastroenteritis, except in the months of June 1988, June 1989, October 1989, January 1990 and March 1990. Viral RNA migration was studied by PAGE in 83 rotavirus positive samples, and 69 (83.1%) of them gave a discernible RNA pattern. A "long" RNA pattern was observed in 58 (84%) and a "short" RNA pattern in 11 (16%) samples. There were three major electropherotypes among the "long" RNA types and two major electropherotypes among the "short" RNA RNA types. Sequential appearance of electropherotypes was seen with every seasonal peak of infection.

Acute Disease↗
PubMed1992

The eukaryotic initiation factor 2-associated 67-kDa polypeptide (p67) plays a critical role in regulation of protein synthesis initiation in animal cells.

The eukaryotic initiation factor 2 (eIF-2)-associated 67-kDa polypeptide (p67) isolated from reticulocyte lysate protects the eIF-2 alpha subunit from eIF-2 kinase-catalyzed phosphorylation and promotes protein synthesis in the presence of active eIF-2 kinases. We have now studied the roles of p67 and eIF-2 kinases in regulation of protein synthesis using several animal cell lysates and an animal cell line (KRC-7) in culture under various growth conditions. The results are as follows. (i) Both p67 and eIF-2 kinase(s) are present in active forms in all animal cells under normal growth conditions and p67 protects the eIF-2 alpha subunit from eIF-2 kinase-catalyzed phosphorylation, thus promoting protein synthesis in the presence of active eIF-2 kinases. (ii) In heme-deficient reticulocyte lysates and in serum-starved KRC-7 cells in culture, p67 is deglycosylated and subsequently degraded. This leads to eIF-2 kinase-catalyzed eIF-2 alpha-subunit phosphorylation and thus to protein synthesis inhibition. (iii) Addition of a mitogen (namely, phorbol 12-myristate 13-acetate) to serum-starved KRC-7 cells in culture induces an increase of p67 and thus increases protein synthesis. These results suggest the following conclusions. (i) Protein synthesis inhibition in a heme-deficient reticulocyte lysate is not due to the activation of an eIF-2 kinase (heme-regulated inhibitor), as is generally believed, but is due to degradation of p67. The heme-regulated inhibitor is present in an active form and possibly in equal amounts in both heme-deficient and heme-supplemented reticulocyte lysates but cannot phosphorylate eIF-2 alpha subunit because of the presence of p67. (ii) p67 is essential for protein synthesis as it protects the eIF-2 alpha subunit from eIF-2 kinase-catalyzed phosphorylation and promotes protein synthesis in the presence of one or more active eIF-2 kinases present in all animal cells. (iii) p67 is both degradable and inducible. Only the p67 level correlates directly with the protein synthesis activity of the cell, indicating that p67 is a critical factor in protein synthesis regulation in animal cells.

Animals↗
PubMed1992

Effects of plant extract Centella asiatica (Linn.) on cold restraint stress ulcer in rats.

Extract of C. asiatica (Linn.) inhibited significantly gastric ulceration induced by cold and restraint stress (CRS) in Charles-Foster rats, Antiulcer activity of plant extract was compared with famotidine (H2-antagonist) and sodium valproate (anti-epileptic). Plant extract, formotidine and sodium valproate showed a dose dependent reduction of gastric ulceration. Plant extract increased brain GABA level which was also dose dependent. Pretreatment with bicuculline methiodide (specific GABAA-antagonist) at the dose level of 0.5 mg/kg im, reversed the antiulcerogenic activity of both plant extract and sodium valproate. Bicuculline as such did not induce gastric ulceration in normal rat.

Animals↗
PubMed1991

An immunoassay for qualitative estimation of collagenase activity in mammalian tissues.

Collagen, the most abundant protein of the mammalian body, is specifically degraded by collagenase. Collagenase activity and subsequent collagen degradation are the main aspects of essential biological processes such as bone remodeling, tissue repair and wound healing. Measurement of collagenase activity is of interest to a wide variety of investigations using mammalian tissues, including clinical specimens. Most assays for collagenase activity are based on chemical modification of the substrate collagen. A unique feature of the present method is that it allows the rapid, qualitative measurement of collagenase activity without the requirement of substrate modification. It is based upon both substrate digestion by collagenase and reaction of undigested collagen with its antibody. Collagenase activity is measured by quantitation of immunoreactivity of undigested collagen using an enzyme-linked immunosorbent assay (ELISA). The assay is performed in 96-well microtiter plates used for ELISA. The advantages of this method are several: (a) a highly specific reaction between substrate collagen and its antibody that rules out the possibility of nonspecific quantitation; (b) the use of a nonmodified substrate; (c) the ease and rapidity of performance of a microassay. Application of the microassay to mammalian tissue homogenates was demonstrated in rat uterus tissue and ventricular myocardium of normal and hypertensive rats.

Animals↗
PubMed1989

Collagenase activity in the normal rat myocardium. An immunohistochemical method.

Fibrillar collagen in the myocardium provides a supportive framework for myocytes and capillaries. Disruption of this organized framework has been observed in certain pathological states. Collagen degradation is primarily mediated by the specific enzyme collagenase, which has been found to exist in various tissues including the myocardium. In this report we describe a method that detects collagenase activity in sections of cardiac tissue. This method is on the basis of degradation of collagen by collagenase on one hand and the visualization of disrupted collagen fibers by immunofluorescence on the other. Frozen rat heart sections were incubated under optimal conditions for collagenase activity (37 degrees C in the presence of 0.1 M calcium at pH 7.4) for 24 h and 48 h. Subsequently, immunofluorescence staining with antibody to type I collagen was performed and the collagenous structures were visualized by immunofluorescence light microscopy. As control, untreated rat heart sections and sections incubated in the absence of calcium were similarly treated with antibody. After the 24 h of incubation, we found no change in the structural integrity of collagen fibers. Marked disruption of the type I collagen fibers was observed 48 h after incubation. No evidence of collagen fiber disruption was found in control sections. Experiments with exogenous collagenase resulted in similar collagen fiber disruption in the frozen rat heart sections. We conclude that the disruption of collagen type I fibers after 48 h of incubation, under optimal conditions for collagenolytic digestion, is the result of collagen degradation by intrinsic collagenase of the myocardium.

Animals↗
PubMed1984

Studies on concanavalin A receptor sites of tumour cells following ultraviolet exposure.

Alteration of surface receptor of Ehrlich tumour cells by concanavalin A (Con A), shortwave UV and UV plus Con A have been studied. DNA of nuclear chromatins is highly sensitive to UV but receptor glycoprotein sites are UV resistant as evidenced by their retention of agglutination properties after radiation. Con A and UV plus Con A treatments of tumour cells delay the in vivo growth of solid tumour which may be due to some immunological mechanism.

Agglutination Tests↗