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Biomedical subjects

S K Sarkar

Publications and source records attributed to S K Sarkar.

At least 19 recordsLinked to original sources
PubMed1992

Hepatoprotective activity of Azadirachta indica leaves on paracetamol induced hepatic damage in rats.

Effect of A. indica leaf extract on serum enzyme levels (glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, acid phosphatase and alkaline phosphatase) elevated by paracetamol in rats was studied with a view to observe any possible hepatoprotective effect of this plant. It was interesting to observe that serum enzyme levels were much elevated in paracetamol induced animals than in those receiving a combination of paracetamol and lead extract. It is stipulated that the extract treated group was protected from hepatic cell damage caused by paracetamol induction. The findings were further confirmed by histopathological study of liver.

Acetaminophen↗
PubMed1992

Ontogenetic and comparative analysis of LDH isozymes in the three species of Indian major carp.

Expression patterns of lactate dehydrogenase (LDH) isozyme were investigated in embryonic and post embryonic stages of Labeo rohita, Cirrhinus mrigala and Catla catla using starch gel electrophoresis. Species specific and differential enzyme locus (gene) expression patterns were found in LDH up to 18th hr of study. The isozyme up to 36th hr after fertilization seemed to be completely active and showed electrophoretic patterns very similar to those of the adults. Comparative analysis of the isozyme of the three species permitted species identification even during the embryonic stages when it is impossible to identify on morphological characters only. Also, the genetic studies indicated different taxonomical and evolutionary histories of the species.

Animals↗
PubMed1991

Enzymatic properties of mutant Escherichia coli tryptophan synthase alpha-subunits.

Thirty-nine mutant tryptophan synthase alpha subunits have been purified and analyzed (in the presence of the beta 2-subunit) for their enzymatic (kcat, Km) behavior in the reactions catalyzed by the alpha 2.beta 2 complex, the fully constituted form of this enzyme. The mutant alpha subunits, obtained by in vitro random, saturation mutagenesis of the encoding trpA gene, contain single amino acid substitutions at sites within the first 121 residues of the alpha polypeptide. Four categories of altered residues have been tentatively assigned roles in the catalytic functions of this enzyme: 1) catalytic residues (Glu49 and Asp60); 2) residues involved in substrate binding or orientation (Phe22, Thr63, Gln65, Tyr102, and Leu105); 3) residues involved in alpha.beta subunit interactions (Gly51, Pro53, Asp56, Asp60, Pro62, Ala67, Phe72, Thr77, Pro78, Tyr102, Asn104, Leu105, and Asn108); and 4) residues with no apparent catalytic roles. Catalytic residue alterations result in no detectable activity in the alpha-subunit specific reactions. Substrate binding/orientation roles are detected enzymatically primarily as rate defects; alterations only at Tyr102 result in apparent Km effects. alpha.beta interaction roles are detected as rate defects in all tryptophan synthase reactions plus Km increases for the alpha-subunit substrate, indole-3-glycerol phosphate, only when L-serine is present at the beta 2-subunit active site. A substitution at only one site, Asn104, appears to be unique in its potential effect on intersubunit channeling of indole, the product of the alpha-subunit specific reaction, to the beta 2-subunit active site.

Catalysis↗
PubMed1991

Yb-DTPA, a novel contrast agent in magnetic resonance imaging: application to rat kidney.

We have developed a novel contrast agent, ytterbium-diethylenetriamine pentaacetic acid (Yb-DTPA), for magnetic resonance imaging (MRI) and its mechanism of action is predominantly by the susceptibility mechanism. We have applied this contrast agent for renal MRI studies. We also demonstrate that Yb-DTPA has a renal clearance similar to that of inulin in rats and may therefore be useful for the estimation of glomerular filtration rate.

Animals↗
PubMed1991

Analysis of immunocompetent cells in the bat, Pteropus giganteus: isolation and scanning electron microscopic characterization.

Immunocompetent cells of the Indian fruit bat (P. giganteus) were characterized by differential surface adhesiveness and surface topography. We observed three cell types: (1) plastic adherent with pseudopodia; (2) nylon wool adherent with small microvilli and pits; and (3) a nylon wool nonadherent with comparatively smooth surfaces. These cell types resemble, respectively, macrophages, B cells and T cells of other mammals, including mice and humans. The disposition of microvilli on the B-type cell surface changes significantly after immunization, which suggests modulation of the molecular organization of the cell membrane and its fluidity. The proportions of these three cell types are not much different from those found in mice. Follicular dendritic cells, capable of retaining antigen for long periods in mice, have also been detected in bats. Further characterization of immunocompetent cells wil help in understanding the mechanism of immune responses in bats.

Animals↗
PubMed1991

Quantitative comparison of magnetic resonance imaging (MRI) and histologic analyses of focal ischemic damage in the rat.

Hemispheric swelling and area of infarction, two parameters of cerebral focal ischemic damage, were identified and quantified from T2-weighted magnetic resonance imaging (MRI) two days after occlusion of the middle cerebral artery (MCAO) in spontaneously hypertensive rat (SHR) brains. Results were compared with these measures quantified from 2,3,5-triphenyltetrazolium hydrochloride (TTC)- and hematoxylin and eosin (H&E)-stained histologic sections in the same brains. The degree of hemispheric swelling and infarct size determined by MRI were highly correlated to the measurements as determined in the TTC- and H&E-stained tissues. These results demonstrate that the focal ischemic damaged area and associated tissue swelling identified by MRI is quantitatively similar to, and thus, is representative of actual tissue damage/changes that can be identified by gross or histologic examination.

Animals↗
PubMed1991

Serovars of multi-antibiotic resistant Escherichia coli from the freshwater environs of Calcutta, India.

For a period of one year (March 1987 to February 1988), the incidence of Escherichia coli was determined in water, sediment and plankton collected from two sampling sites in a freshwater lake extensively used by humans and animals. Densities of E. coli associated with plankton was the lowest while sediments, especially at site 2, harbored high densities of the organism. Correlation coefficients revealed that the density of E. coli in water samples was linearly correlated to temperature, pH of water, sediment and humidity. Stepwise multiple regression analysis, however, showed that sediment temperature was the dominant variable which could explain 27% of the observed variation in the numbers of E. coli in the overlying waters (p = less than 0.001). Of the 150 environmental E. coli strains which were characterized, 31 (20.7%) were found to belong to the classic enteropathogenic E. coli (EPEC) serogroups. Seven of the serogroups among the environmental EPEC strains were also encountered from EPEC strains isolated from human cases during a concurrent clinical study. None of the 150 environmental strains were enterotoxigenic or enteroinvasive but 4 strains possessed HEp-2 cell adhesive factor. With the exception of one, all the EPEC strains isolated were multi-drug resistant. From this study, it was evident that the lake is an important source of infection of EPEC and other related diarrheagenic E. coli.

Diarrhea, Infantile↗
PubMed1991

Hypoglycemic and antihyperglycemic effect of leaves of Vinca rosea linn.

Oral administration of water fraction of alcoholic extract of leaves of Vinca rosea (fam. apocynaeceae) led to marked lowering of blood glucose level in normal and streptozotocin induced diabetic rats. The hypoglycemic effect of the fraction was comparable with that of tolbutamide.

Administration, Oral↗
PubMed1989

9.4-T NMR microimaging studies of hepatic metastases of human colorectal tumors in nude mice.

We have applied NMR microimaging at 9.4 T to detect metastatic deposits in the liver of nude mice noninvasively, using an animal model for metastatic colon cancer that mimics several aspects of the human disease. Images were obtained with a resolution of 100 x 100 x 900 microns and the tumor deposits were clearly distinguished from the normal liver tissue with excellent contrast. Comparison of NMR images with corresponding histologic sections indicates that lesions as small as 900 microns were detected.

Adenocarcinoma↗
PubMed1988

Renal imaging studies at 1.5 and 9.4 T: effects of diuretics.

We have studied the effects of two diuretics, selective for renal cortical (furosemide) and inner medullary (vasopressin antagonist) water handling, in rat kidney at 1.5 T and find that furosemide completely dissipates the cortical-inner medullary T2 gradient whereas the vasopressin antagonist has little effect. This phenomenon appears to be related to changes in luminal water content. We also demonstrate the feasibility of obtaining live mouse kidney images with a resolution of 100 x 100 x 700 micrometers at 9.4 T.

Animals↗
PubMed1988

9.4 T imaging studies of human tumor xenografts in nude mice.

To evaluate the potential of 9.4 T imaging in distinguishing normal and neoplastic tissues, we examined the progressive growth of human colon and prostate adenocarcinoma xenografts in nude mice. Images were obtained with a resolution of 100 X 100 X 650 micron, and tumors were clearly distinguished from normal tissue with high contrast. These results demonstrate the feasibility of detecting small human tumors in live nude mice with microscopic resolution at 9.4 T.

Adenocarcinoma↗
PubMed1987

Molecular dynamics of collagen side chains in hard and soft tissues. A multinuclear magnetic resonance study.

We have prepared samples of (a) intact calvaria collagen (cross-linked and mineralized), (b) intact tendon collagen (cross-linked but not mineralized), and (c) reconstituted chick calvaria collagen (not cross-linked and not mineralized) containing [methyl-2H3]methionyl, [4,4-2H2]pyrrolidinyl, (4-fluorophenyl)alanyl, and [6-15N]lysyl residues. Using multinuclear magnetic resonance spectroscopy, we have investigated the molecular dynamics of the labeled amino acids. Guided by model compound studies, we reached the following conclusions regarding collagen side chain dynamics from our analysis of line shapes and relaxation rates. At 22 degrees C, imino residues in all samples have flexible rings with root mean square angular fluctuations in the 11-30 degree range. Nearly all labeled amino acid side chains reorient about at least two side chain single bonds. At temperatures below -30 degrees C, most of these side chain motions are absent in all the samples. Surprisingly, in contrast with results obtained for backbone motions, side chain motions are only marginally more hindered in mineralized samples as compared with nonmineralized samples, a result we discuss with reference to collagen-mineral interactions. We also discuss the possible relationship between collagen dynamics and function.

Achilles Tendon↗
PubMed1987

Stridor due to drug-induced hypokalaemic alkalosis.

A 76-year-old on long-term Lasix and Pyrogastrone presented with stridor. This became worse with local irritation, e.g. on coughing or during indirect laryngoscopy. Indirect laryngoscopy showed a narrow glottis with an otherwise normal larynx. Blood investigation showed a low serum potassium with a raised bicarbonate level, and a serum calcium level just within the acceptable normal range. A diagnosis of laryngospasm secondary to drug-induced hypokalaemic alkalosis was made. This was treated with the withdrawal of the above drugs and supplementing potassium orally.

Aged↗