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Biomedical subjects

S Chakrabarty

Publications and source records attributed to S Chakrabarty.

103 records · Page 6Linked to original sources
PubMed1979

Antifertility effects of the steroid 5 alpha-stigmastane-3 beta, 5, 6 beta-triol 3-monobenzoate on mice.

The steroid 5 alpha-stigmastane-3 beta, 5, 6 beta-triol 3-monobenzoate at a dose of 40 mg/kg of body weight has 100% interceptive activity when administered orally in a single dose during 6-7 days of gestation but it has no action on pregnancy if treated on 10th, 13th or 16th day of pregnancy. The interceptive activity of the steroid is lost by simultaneous injection of prolactin, progesterone or LH.

Abortifacient Agents↗
PubMed1976

Histomorphological study of adrenal gland in three ophidian species.

Adrenal gland is studied histologically in the common krait, the cobra and the viper. It is comprised largely of cortical tissue with medulla. Chromaffin tissue is spatially distributed on dorsal surface and in the intercortical area of the adrenal gland. Percentage of dorsal chromaffin is higher in the viper and cobra than that of the krait, while that of intercoritcal chromaffin is higher in the krait than that of others. Chromaffin cells are irregular, smaller with densely granulated cytoplasm and larger nuclei than those of interenal gland. Medullary cells are larger in the cobra than those of other snakes. Cytomorphological difference between the dorsal and intercortical chromaffin is marked only in the cobra. Occurrence of larger granules in the dorsal and smaller type in the intercortical chromaffin may be related with noradrenaline and adrenaline secretion respectively. Cortical percent is higher in the krait than that of other snakes. Adrenocortical zonation is found only in the common krait and cobra. Subcapsular zone shows regular cords with radial disposition of columner cells in contrast to the irregular orientation of polygonal cells noted in the central cortex. Differences observed in general morphology and histology of adrenal gland, are possibly due to species difference.

Adrenal Cortex↗
PubMed1975

Methylated basic amino acid composition of histones from the various organs from the rat.

Newborn rats received 5 muCi each of [3H]lysine and [methyl-14C]methionine/g body weight. They were killed 10 days later and the nuclei prepared from the kidneys, liver, cerebrum, cerebellum, and thymus. The five major histones were extracted from these nuclei by the method of Johns and further purified on Bio-Gel P-10. The histones were hydrolyzed and the basic amino acids fractionated on Beckman PA-35 resin. Only the F3 and Fia1 histones contained any significant amounts of methylated amino acid residues as measured by chemical or radiological assay. The product of methylation of F2a1 was predominantly dimethyllysine with trace quantities of monomethyllysine detectable in rapidly proliferating tissue. The products of methylation of F3 were mono-, di-, and trimethyllysine in an approximate molar ratio of 0.55:1.0:0.35. This ratio did not vary significantly in the F3 histones prepared from the different organs. No methylarginine or methylhistidine was detected in any of the histones prepared from the five organs. The total amount of dimethyllysine in F2a1 from the different organs of adult rats was approximately 2.0 mol/mol of polypeptide. It appears that the distribution of methyl groups on the lysyl residues in the F3 and F2a1 histones from the different organs is similar and does not contribute to tissue heterogeneity.

Amino Acids↗
PubMed1975

l-amino acid oxidases of Proteus rettgeri.

Proteus rettgeri has been found to contain two separable 1-amino acid oxidases. Both enzymes are particulate in nature, neither being ribosomal bound. One of these enzymes appears to have broad specificity, being active toward monoaminomonocarboxylic, imino, aromatic, sulfur-containing, and beta-hydroxyamino acids. The other enzyme has more limited specificity, catalyzing the oxidative deamination of the basic amino acids and citrulline. The affinity of this oxidase for the various substrates at pH 7.6 in decreasing order is arginine, histidine, ornithine, citrulline, and lysine. This enzyme has a particularly high affinity for arginine (Km equal to 0.27 mM), and anomalous kinetics are observed with increasing substrate concentrations. When concentrations of arginine greater than 1.0mM were added to the reaction containing histidine, imidazole pyruvate formation was completely inhibited.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Epidermal growth factor receptor (EGFR) antisense transfection reduces the expression of EGFR and suppresses the malignant phenotype of a human ovarian cancer cell line.

An EGFR-expressing clone of the human ovarian cancer line 2774 was transfected with an antisense construct of EGFR to test how suppression of this gene modulates the malignant phenotype. Transfected clones were screened for EGFR expression by Western blot and FACS analysis. Anchorage-independent growth was used to assess the effect of reduced EGFR on the malignant behavior of the cells. Several transfected clones with decreased EGFR (40-50% reduction) were identified. A correlation was noted between reduced EGFR and decreased anchorage-independent growth, with the transfected clones losing the ability to grow in agarose and responsiveness to exogenous EGF. These results suggest that EGFR may be an important factor in the malignant behavior of this ovarian cancer cell line.

Cell Division↗
PubMedDate not supplied

Modulation of differentiation-related responses in human colon carcinoma cells by protein kinase inhibitor H-7.

1-(isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), a potent inhibitor of protein kinases, has been used as a tool to examine the role of protein kinases in a variety of cellular functions. Contingent on the cell type, H-7 has been reported either to inhibit or to promote differentiation. The biological effects of H-7 on human colon adenocarcinoma cells have not been reported. In this study we investigated the effects of H-7 on differentiation - related parameters such as cellular morphology, proliferation, the expression of carcinoembryonic antigen (CEA), fibronectin and cytokeratins in human adenocarcinoma cell lines HCT116 and SW480. H-7 induced pronounced morphological alterations in both cell lines. It induced fibronectin expression and down-modulated CEA expression and secretion in the SW480 cells, but not in the HCT116 cells. Expression of acidic keratins was not affected by H-7 treatment in both cell lines. However, the expression of basic keratins were down-modulated in the HCT116 cells and enhanced in the SW480 cells. These studies showed that the protein kinase inhibitor, H-7, modulated phenotypic properties in human colon adenocarcinoma cells. Alterations in phenotypic properties and their significance in regard to the induction of differentiation are discussed.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMedDate not supplied

Differentiation-related alterations in the plasma membranes of chemically transformed murine fibroblasts.

One of the pathways of action of the differentiation-inducing agent DMF, in chemically transformed AKR-MCA fibroblastic cells, is through the concurrent restoration of the synthesis of the cell-surface adhesion molecule fibronectin and receptors for fibronectin. In order to identify plasma membrane components that are intimately associated with the induction of differentiation by DMF in the AKR-MCA cells, we have purified, characterized and compared the plasma membranes prepared from DMF treated and untreated AKR-MCA cells and from DMF treated and untreated AKR-2B cells (untransformed control cells). While DMF was found to have a non-discernible effect on the plasma membranes of the untransformed AKR-2B control cells, it restored the expression of several major AKR-2B associated plasma membrane proteins to the transformed AKR-MCA cells. These included major plasma membrane proteins of molecular weight 46 and 38 kilodaltons which were identified by one-dimensional SDS-PAGE, and two other major silver staining proteins identified by two-dimensional gel electrophoresis. Plasma membrane carbohydrate moieties were also analyzed by 125I-lectin probes following SDS-PAGE fractionation and electrophoretic transfer of plasma membranes to nitrocellulose. Differences in the radiolabeled Con A and RCA 1 binding profiles were observed between the untransformed and transformed cells. DMF induced an overall restoration of the untransformed AKR-2B associated lectin binding profiles to the differentiated AKR-MCA cells. This study identified several plasma membrane proteins and lectin binding carbohydrate moieties, the qualitative or quantitative alterations of which were intimately associated with chemical transformation and differentiation induction of the transformed cells.

Animals↗
PubMedDate not supplied

Inhibition of human colon cancer malignant cell behavior and growth by antisense epidermal growth factor receptor expression vector.

Human colon cancer cells utilize the epidermal growth factor (EGF) family of growth factors and the receptor for these growth factors (EGFR) in sustaining their malignant phenotype. Disrupting EGFR expression by expressing antisense EGFR RNA (through transfection with an appropriate antisense EGFR expression vector under metallothionein promoter control) downregulated the malignant behavior of human colon cancer Moser cells and blocked the ability of exogenous EGF in stimulating malignant cell behavior. The antiproliferative effect of antisense EGFR expression vector was determined in three human colon cancer cell lines (Moser, HCT116 and HT29 possessing different biological properties and rate of proliferation) in an in vitro therapeutic setting using an antisense EGFR expression vector under the control of a viral promoter. Different degree of inhibition was achieved for each cell line after one dose of antisense treatment. The differences in the antiproliferative effect observed may be due to differences in the rate of proliferation and/or recovery from antisense effect, and the differences in transfection efficiency among the cell lines.

Cell Division↗