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Biomedical subjects

S Sarkar

Publications and source records attributed to S Sarkar.

At least 361 records · Page 20Linked to original sources
PubMed1981

A proteinless mutant of tobacco mosaic virus: evidence against the role of a viral coat protein for interference.

A coat-protein-free mutant of tobacco mosaic virus as well as mutants with a non-functional coat protein were found to interfere with the establishment and spread of challenging strains of TMV. The results do not support an earlier concept, according to which the genome of a related challenging virus could be captured by the coat protein of the virus introduced in advance. The presence of a viral coat protein is obviously not essential and a competition among the viral genomes for some specific site seems to be a more likely mechanism of cross protection.

Mutation↗
PubMed1981

Enhancement of human amniotic cell growth by Ficoll-Paque gradient fractionation.

Ficoll-Paque isopycnic centrifugation was used as a preparative procedure for amniotic fluid (AF) cells prior to tissue culture. This technique serves to reduce contaminating erythrocytes and also enhances cell growth or mitotic indices. The technique described in this report yields three subfractions designated as a turbid interphase layer (F-2), a middle cell layer (F-3), and a bottom pellet (F-4). The middle cell layer (F-3) demonstrated better cell growth and higher mitotic index than any of the other fractions or control unfractionated amniotic fluid cells. The use of Ficoll-Paque isopycnic preparative centrifugation of amniotic fluid cells is a valuable adjunct in cell culture for cytogenetic analysis. This may be especially true when amniotic fluid contains large numbers of erythrocytes.

Amniotic Fluid↗
PubMed1981

Inhibitory effect of human urinary extract on the growth of DMBA-induced mammary tumors in Holtzman rat.

The effect of a crude protein fraction from human urine having gonadotropin inhibitory activity (GGIM) was observed on the growth of 7,12-dimethylbenz(a)anthracene induced mammary tumors in Holtzman rat. Results show that while in 12 out 13 tumors, tumor growth was retarded/regressed following 2--4 weeks of CGIM treatment, tumor growth in control rats was unabated. However, no positive correlation with hormone dependency and tumor regression could be established. Further, this crude anti LH material was found to be non-toxic to tumor cells in vitro.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Neural origin of cells in amniotic fluid.

Cells from the amniotic fluid of fetuses with open neural tube defects (NTDs) have several abnormal characteristics of potential diagnostic value. The cell number in a unit volume of fluid is 10 to 100 times the normal range of cell count. The majority of cells adhere to tissue culture dishes within 24 hours of inoculation, instead of the 4 or 5 days required by normal amniotic fluid cells. The rapidly adhering cells morphologically resemble glial cells. Their Coulter volume is about twice the average seen in normal amniotic fluid--derived cells. This larger number of oversized, rapidly adhering cells is likely due to the continuous accumulation of neural cells in the amniotic fluid. We have detected the presence of the glial protein S-100 and the absence of the neuronal protein 14-3-2 by using a specific immunofluorescence assay. We conclude that fetuses with NTDs shed large numbers of glialike cells into the amniotic fluid where their detection may have diagnostic importance.

Amniotic Fluid↗
PubMed1980

A radiological study of the movements of the two components of the Monk prosthesis (hard-top 'duo-pleet') in patients.

Following replacement of the femoral head with the Monk hard-top 'duo-pleet' prosthesis, radiological studies show that movement of the replaced hip takes place between the acetabulum and the metal shell and between the high density polyethylene cup and metal ball. Movements improve with the passage of time. The two sites of movement may contribute to a greater range of hip movement, a better safeguard against loosening and possibly less medial migration of the prosthesis than solid metal prostheses like the Thompson and Austin Moore types.

Aged↗
PubMed1980

Cell cycle and the differential expression of HLA-A,B and HLA-DR antigens on human B lymphoid cells.

Monoclonal antibodies specific to HLA antigens and the fluorescence-activated cell sorter were used to analyze the changes in the density of human histocompatibility antigens HLA-A,B and HLA-DR on the surface of synchronously growing WI-L2 cells (a human B cell line) progressing through the cell cycle. The WI-L2 cells were synchronized by density-dependent arrest in G1, and samples from G0, G1, late S and late G2 phases were used to determine the frequency distribution of cell volume, DNA content, and the relative amounts of cell surface HLA antigens; the observed density changes were calculated from these values. The HLA-A,B density remained nearly constant throughout the cell cycle, whereas the HLA-DR density increased sharply at the G2-M stage. These results suggest a cell cycle-dependent differential control of the expression of these two sets of histocompatibility antigens on B cells.

B-Lymphocytes↗
PubMed1980

Socio-economic status and mental morbidity in certain tribes and castes in India--a cross-cultural study.

The authors made a field-survey of mental morbidity in all the tribal and caste groups residing in a cluster of villages in West Bengal, India, and found that, in each group, higher socio-economic classes had higher rates of mental morbidity. Different groups having a similar cultural pattern showed no significant difference in their rates of morbidity. Groups having different cultural patterns differed significantly in their rates of morbidity. In the tribal groups some neurotic disorders were absent.

Cross-Cultural Comparison↗
PubMed1980

Enhanced Growth of amniotic fluid cells in presence of fibroblast growth factor.

A shorter period of time between amniocentesis and cytogenetic diagnosis is of considerable clinical usefulness. Fibroblast growth factor (FGF), a potent mitogen for cells of mesodermal origin, was used to enhance the growth rate of primary cultures of amniotic fluid-derived cells. At the initial harvest and at 5 scored metaphases, culture dishes incubated with FGF showed a 9-day advantage as a group when compared with their untreated, paired controls. In addition, less variability was encountered in the growth time of the FGF-treated dishes; 97% of these treated dishes were harvested initially between 10 and 20 days, while only 48% of the control dishes were harvested initially during this time period. Success was also noted in the recovery of failing cultures. The addition of FGF to the standard enriched medium used in amniotic fluid cell cultures has shortened the processing time and provided a more uniform growth rate in the majority of cultures studied.

Amniocentesis↗
PubMed1979

A model of translational control involving mRNA-associated proteins in chick embryonic muscles.

Highly purified poly(A)-containing free and polysomal mRNP particles have been isolated by chromatography of subcellular fractions of chick embryonic muscles on oligo-dT-cellulose and elution with low salt buffer at 45 degrees. The free and polysomal mRNP represent two distinct classes of macromolecules, the free particles having a more complex nucleoprotein organization than the polysomal particles. Comparison of the protein moieties of three classes of poly(A)-containing cytoplasmic mRNP -- those released from nuclei after in vitro transcription and processing (transported mRNP), the free, and polysomal mRNP -- strongly suggests that the majority of the mRNA-associated proteins are exchanged in the cytoplasm during the various functional states of mRNA. A model of translational control involving the participation of mRNA-associated proteins in chick embryonic muscles and by analogy in other differentiated eukaryotic cells is proposed.

Animals↗
PubMed1979

Nitrosoguanidine-induced mutations in Streptomyces indicus.

The mutagenic activities of five 1-alkyl derivatives of 3-nitro-1-nitrosoguanidine, viz. methyl, ethyl, propyl, isopentyl and octyl, were tested on Streptomyces indicus. All the compounds were found to be mutagenic. The methyl and ethyl derivatives were most effective regarding mutational frequency. The effectiveness decreased with increasing number of C-atoms in the alkyl group of the mutagens. The compounds tested had a much higher mutagenic efficiency that UV-rays. A marked variation existed in antibiotic activity among the biochemical mutants: increase, decrease or complete absence of such activity were seen.

Mutagens↗
PubMed1979

Release of in vitro-synthesized poly(A)-containing RNA from isolated rat liver nuclei: characterization of the ribonucleoprotein particles involved.

Nuclei isolated from rat liver were incubated under conditions in which RNA continued to be labeled with precursors for long periods. After 1 hr, during which the rate of RNA synthesis was constant, 25-30% of the newly synthesized RNA was recovered in the postnuclear supernatant. About 3-5% of this fraction was characterized as poly(A)-containing ribonucleoproteins by the following criteria: (i) characteristic elution profile in oligo(dT)-cellulose chromatography; (ii) size distribution of the molecules and their deproteinized RNAs; (iii) buoyant densities in CsCl gradients; (iv) presence of RNaseresistant fragments resembling poly(A)-protein complexes; and (v) identification of the protein components by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The sensitivity of labeling of the RNA synthesized and released from the nuclei to low doses of alpha-amanitin suggests the presence of polymerase II products in the particles. Comparison of the sizes of proteins in these particles with those of free and polysomal messenger ribonucleoproteins as well as with heterogenous nuclear ribonucleoproteins indicates that the released particles contain a protein of 78,000 daltons, which is also present in the other three classes of ribonucleoproteins, presumably at the 3'-poly(A) segments. In addition, a few other proteins, similar in size to those found in the cytoplasmic ribonucleoproteins, were also present in the released particles. It is suggested that proteins associated with heterogenous nuclear RNA are mostly exchanged before or at the time of release of mRNA from the nucleus; the remaining mRNA-associated proteins are added in the cytoplasm, possibly in relation to cytoskeleton attachment, followed by the removal of most of these proteins during polysome formation.

Amanitins↗