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Biomedical subjects

S Ghosh

Publications and source records attributed to S Ghosh.

At least 901 records · Page 50Linked to original sources
PubMed1987

Kinetochores on chromosomes enclosed within the nuclear envelope.

The kinetochore plate which develops after nuclear envelope breakdown in normal cells can be seen to be formed on condensed chromosomes still enclosed in the nuclear envelope in fused multinucleate cells where some nuclei show delayed envelope breakdown caused by nuclear interaction. This suggests that neither nuclear envelope breakdown nor assembly of microtubules is directly related to the formation of the kinetochore plate. Furthermore, it can be clearly observed in these cells that the kinetochores do not have any special association with the nuclear envelope.

Chromosomes, Human↗
PubMed1987

Preliminary evaluation of cocarboxylase on myocardial protection of the rat heart.

The presence of cocarboxylase (CC) is essential for the oxidation of pyruvate to acetylcoenzyme A (acetyl-CoA) and its subsequent degradation by means of the Krebs cycle. We compared the effects of various concentrations of CC in a cardioplegic solution on the survival and hemodynamic and metabolic recovery of 23 isolated, working rat hearts subjected to 60 minutes of hypothermic (23 degrees C) ischemic arrest. Group 1 (N = 6) consisted of hearts infused with the basic cardioplegic solution (Tyers' solution with glucose), to which no CC was added. In group 2 (N = 6) CC was added at 0.1 ml/L to the cardioplegic solution. In group 3 (N = 5) CC was added at 1 ml/L, and in group 4 (N = 6) CC was added at 10 ml/L. The cardioplegic infusions were performed at a pressure of 40 mm Hg for 2 minutes just before arrest; 30 minutes later they were performed again for 1 minute. Only two hearts (33.3%) recovered in group 1 whereas five recovered in group 2, five (100%) in group 3, and five (83.3%) in group 4. The recovery of hemodynamic performance as a percentage of preischemic control values showed marked improvement in the CC groups, especially group 3, when compared with group 1. The metabolic variables in the CC groups were also markedly improved, with significantly (p less than .05) decreased levels of tissue lactate and increased levels of creatine phosphate compared with those in group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Arterial uptake indices of low density lipoproteins after fatty streak formation in Cynomolgus monkeys.

To evaluate changes in arterial wall uptake of an atherogenic lipoprotein in early atherogenesis the uptake of labelled low density lipoprotein was measured in four segments of aorta in Cynomolgus monkeys with diet induced fatty streaks. The influx rate of low density lipoprotein was estimated from a simple kinetic model. The mean influx rate, expressed as plasma equivalents of tracer, was 69 nl.cm-2 per hour in fatty streak monkeys and 28 nl.cm-2 per hour in controls (p less than 0.001). Using additional assumptions, provisional estimates of the rates of apparent efflux were calculated. In fatty streak monkeys the mean apparent efflux rate, relative to the accumulation of tracer in the wall, did not differ significantly from the efflux rate in controls (8.7% per hour vs 7.9% per hour, p greater than 0.05). Thus intimal permeability to low density lipoprotein is increased at the fatty streak stage of lesion formation but apparent efflux may not be changed. The data fit the hypothesis that relative failure of efflux is a major cause of excess low density lipoprotein accumulation in the vessel wall in hypercholesterolaemia.

Animals↗
PubMed1987

Regulation of fructose uptake and catabolism by succinate in Azospirillum brasilense.

Fructose uptake and catabolism in Azospirillum brasilense is dependent on three fructose-inducible enzymes (fru-enzymes): (i) enzyme I and (ii) enzyme II of the phosphoenolpyruvate:fructose phosphotransferase system and (iii) 1-phosphofructokinase. In minimal medium containing 3.7 mM succinate and 22 mM fructose as sources of carbon, growth of A. brasilense was diauxic, succinate being utilized in the first phase of growth and fructose in the second phase with a lag period between the two growth phases. None of the fru-enzymes could be detected in cells grown with succinate as the sole source of carbon, but they were detectable toward the end of the first phase of diauxie. All the fru-enzymes were coinduced by fructose and coordinately repressed by succinate. Studies on the effect of succinate on differential rates of syntheses of the fru-enzymes revealed that their induced syntheses in fructose minimal medium were subject to transient as well as permanent (catabolite) repression by succinate. Succinate also caused a similar pattern of transient and permanent repression of the fructose transport system in A. brasilense. However, no inducer (fructose) exclusionlike effect was observed as there was no inhibition of fructose uptake in the presence of succinate with fructose-grown cells even when they were fully induced for succinate uptake activity.

Culture Media↗
PubMed1987

Analysis of human antibody response to cholera vaccination by Epstein Barr virus transformation and human-human hybridoma production.

The response of Epstein Barr virus transformable B lymphocytes to V. cholerae serotypes Inaba and Ogawa was assessed at various periods of time after primary and secondary immunization. In both cases, 100% of cells laid down at 10(4)/well gave a very strong positive reaction with either serotype one week after immunization. Further analysis indicated that general polyclonal activation by the bacterial LPS was not a major feature since the reactivity with other bacterial antigens was weak. Human monoclonal antibodies generated from the primary wells by backfusion with the KR4 cell line had low affinity in comparison to rat monoclonal antibodies reactive with the same antigen but were serotype specific and able to fix guinea pig complement.

Animals↗
PubMed1987

Pathogenesis of experimental lipid keratopathy: corneal and plasma lipids.

Corneal and plasma lipids were studied in a rabbit model to gain insight into the pathogenesis of secondary lipid keratopathy. Rabbits were divided into four groups in which a high cholesterol diet and corneal suture placement were varied to produce lipid keratopathy. In rabbits with lipid keratopathy, quantitative thin layer chromatography revealed that cholesterol esters comprised most of the deposited lipid, with free cholesterol being deposited as well. The ratio of accumulated cholesterol ester to free cholesterol corresponded closely to the same ratio in hypercholesterolemic plasma total low and very low density lipoprotein (TLDL). Furthermore, gas chromatography showed that the cholesterol ester composition in the corneas with lipid keratopathy resembled that seen in hypercholesterolemic plasma TLDL but was different from the pattern observed in the normal cornea. These studies suggest that the direct source of the deposited cholesterol ester is primarily the plasma TLDL. Since phospholipids and triglycerides did not show a significant increase in the experimental corneas, they are presumably metabolized by the keratocytes after the uptake of TLDL. However, the amount of cholesterol ester carried by the lipoprotein exceeds the capacity of the cell for use and excretion and the lipid accumulates in the cornea.

Animals↗
PubMed1986

NADPH/NADH-dependent cold-labile glutamate dehydrogenase in Azospirillum brasilense. Purification and properties.

A cold-labile glutamate dehydrogenase (GDH, EC 1.4.1.3) has been purified to homogeneity from the crude extracts of Azospirillum brasilense. The purified enzyme shows a dual coenzyme specificity, and both the NADPH and NADH-dependent activities are equally cold-sensitive. The enzyme is highly specific for the substrates 2-oxoglutarate and glutamate. Kinetic studies with GDH indicate that the enzyme is primarily designed to catalyse the reductive amination of 2-oxoglutarate. The NADP+-linked activity of GDH showed Km values 2.5 X 10(-4) M and 1.0 X 10(-2) M for 2-oxoglutarate and glutamate respectively. NAD+-linked activity of GDH could be demonstrated only for the amination of 2-oxoglutarate but not for the deamination of glutamate. The Lineweaver-Burk plot with ammonia as substrate for NADPH-dependent activity shows a biphasic curve, indicating two apparent Km values (0.38 mM and 100 mM) for ammonia; the same plot for NADH-dependent activity shows only one apparent Km value (66 mM) for ammonia. The NADPH-dependent activity shows an optimum pH from 8.5 to 8.6 in Tris/HCl buffer, whereas in potassium phosphate buffer the activity shows a plateau from pH 8.4 to 10.0. At high pH (greater than 9.5) amino acids in general strongly inhibit the reductive amination reaction by their competition with 2-oxoglutarate for the binding site on GDH. The native enzyme has a Mr = 285000 +/- 20000 and appears to be composed of six identical subunits of Mr = 48000 +/- 2000. The GDH level in A. brasilense is strongly regulated by the nitrogen source in the growth medium.

Amino Acids↗
PubMed1986

Spin-lattice relaxation in the triplet state of the buried tryptophan residue of ribonuclease T1.

The individual spin-lattice relaxation (SLR) rate constants (Wij) between the lowest triplet sublevels of the lone tryptophan residue buried in the interior of the globular protein ribonuclease T1 have been reported in the temperature range 1.2 to 3.0 K in zero applied magnetic field. The SLR rate constants between spin sublevels exhibit marked anisotropy in their magnitudes and also show appreciable sensitivity to the glycerol content of the aqueous cryogenic matrix. The temperature dependence of SLR suggests that in the temperature range investigated a direct process contributes dominantly to the SLR in this protein.

Chymotrypsin↗
PubMed1986

Human melanocytes cultured from nevi and melanomas.

The requirements for growth factors of human melanocytes in culture may be dependent on the stage of malignant transformation. Several factors synergistically promote the viability and proliferation of human neonatal melanocytes in culture. They are TPA (12-O-tetradecanoyl-phorbol-13-acetate), isobutylmethyl xanthine, cholera toxin, and as yet unidentified factors from extracts derived from several cell lines and human placenta. Neonatal melanocytes can maintain at least 50 population doublings during a period of 6 months, whereas melanocytes from adult skin proliferate only for 1 month and at less than 1% of the proliferative rate of melanocytes derived from newborn foreskins. In contrast, melanocytes from dysplastic and congenital nevi proliferate well in the presence of mitogens during the initial 4-6 weeks of culture, but then become quiescent. Melanocytes from primary melanomas are the most difficult to grow in culture. They need the mitogens, but their rate of proliferation is slow. Most of the metastatic melanocyte strains that do not need the mitogens in order to proliferate, are strongly inhibited by TPA, and to a lesser extent by WI-38 cell extract. We conclude that the acquisition of independence from mitogens in culture is a late event in the transformation of melanocytes to melanomas.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Transcriptive and replicative activity of the X chromosome in an autosomal segmental hyperploid in Drosophila and its significance.

In the present investigation the transcription and replication patterns have been examined in different segments of the X chromosome and in certain specific segments (88B-92A) of an autosomal segmental hyperploid in which an extra segment 88B-92A (3R) is translocated to the X chromosome in addition to the normal two doses. Transcriptive activity monitored by [3H]uridine-labelling of these autosomal hyperploids reveals an enhanced hyperactivity of the male X chromosome while the female X chromosomes show no change in their activity. [3H]thymidine autoradiograms reveal that while the labelling frequencies of most replicating sites are distinctly lowered in the autosomal hyperploid males, no change within sexes is resolvable with regard to labelling-intensity profile. Furthermore, the X-autosome labelling frequency relation shows a distinct deviation from linearity, suggesting multiple events that lead to a higher template form of the X chromosome. These findings lead us to suggest that the signals emanating from autosome(s) do not interfere with the primary modulation inherent in the X chromosome, but act on a modulated organization of the same at a second step evoking higher activity in the male X chromosome. The results further reveal that the gene activity of the X chromosome remains unaffected by the pattern of pairing of the autosomal segments.

Animals↗