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Biomedical subjects

D Ghosh

Publications and source records attributed to D Ghosh.

At least 235 records · Page 13Linked to original sources

Recognition of EBV plasma membrane protein expressed on murine cells after gene transfer.

The immune response to B lymphocytes infected with Epstein-Barr virus (EBV) prevents their overgrowth in normal humans. A murine model is now described for analyzing the T cell immune response to Epstein-Barr virus genes expressed in murine lymphoblasts by gene transfer. In mice, a 60,000 dalton virus-encoded protein characteristically found in the plasma membrane of latently infected human lymphocytes readily induces both proliferative and cytolytic T lymphocytes specific for both the EBV protein and murine major histocompatibility proteins. Longterm cultures of L3T4+ cells, some of which were cytolytic, were found to be restricted by H-2I-Ed and the latent membrane protein. Similarly, Lyt-2+ cells were cytolytic and were restricted by H-2Ld and the lymphocyte membrane protein gene product. The similarity in murine and human effector cell responses suggests that this is a useful experimental model, and the EBV latent infection membrane protein may be an important antigen in the immune restriction of growth transformed latently infected lymphocytes.

Animals↗

Crystals of active tetramers of 3 alpha, 20 beta-hydroxysteroid dehydrogenase.

The NADH-dependent steroid metabolizing enzyme 3 alpha, 20 beta-hydroxysteroid dehydrogenase (EC 1.1.1.53), from Streptomyces hydrogenans, has been crystallized in the active tetrameric form. Single crystals (approximately 0.75 X 0.40 X 0.40 mm) of square bipyramid shape have been grown reproducibly at room temperature in the presence of excess NADH. Diffraction experiments have been performed at the Cornell High Energy Synchrotron Source. The space group is P43212 or its enantiomorph, and the cell dimensions are a = 106.0(5) A and c = 204(1) A. The asymmetric unit is a tetramer of identical subunits of approximately 25,000 daltons each. The specific volume is 2.8 A3/dalton. A native data set at 2.5-A resolution has been collected. Two potential heavy atom derivatives, with K2Pt(CN)4 and KAu(CN)2, have been identified from the diffraction photographs.

20-Hydroxysteroid Dehydrogenases↗

The effect of lead on insecticide metabolism.

The possibility that lead could affect the metabolism of the insecticide 1,1-dichloro-2, 2-bis(p-chlorophenyl)ethane, DDD, was examined by studies of the effects of chronic oral Pb treatment on DDD conversion to 2,2-bis(p-chlorophenyl)acetic acid, DDA. Rats were given either distilled deionized water or 0.05, 0.58, 17 or 352 ppm Pb solutions as drinking water. Systolic blood pressure and body weight were measured weekly. Rats drinking 352 ppm lead chloride manifested a statistically significant increase in blood pressure. Rats drinking 352 ppm and 17 ppm lead chloride showed a significant decrease in the rate of weight gain compared to controls. All groups showed an increase in the excretion of total DDA compared to controls.

Animals↗

In vitro PGE2 synthesis by seminal vesicular microsomes: hysteretic behaviour in the presence of calcium ions.

When 4 mM Ca2+ is added gratuitiously in the reaction mixture synthesizing prostaglandin E2 (PGE2) from arachidonic acid and cofactors by membrane associated microsomal multienzyme system (MES) prepared from goat seminal vesicles, one observes an immediate lag in the production of PGE2. This Ca2+ induced lag is clearly due to the hysteretic response of MES promoted by Ca2+ ligand and not mediated through any effect of the divalent cation on the membrane, such as membrane phase separation. Preincubation studies indicated that the hysteretic response of MES is not due to Ca2+ ligand alone, but the substrate(s) also co-operate to modulate the enzyme system to demonstrate the characteristic nonlinear kinetics.

Animals↗

Sultamicillin (CP-49, 952): evaluation of two dosage schedules in urinary infection.

The results of a clinical trial of sultamicillin, a novel mutual pro-drug combination of ampicillin and the beta-lactamase inhibitor sulbactam, in ampicillin-resistant urinary tract infections are reported. The majority of infections treated occurred in elderly geriatric in-patients. Two dosage schedules were investigated, both resulting in the same total daily dosage (1500 mg sultamicillin). These were 750 mg sultamicillin, 12-hourly (series I) and 500 mg sultamicillin, 8-hourly (series II), each administered orally for seven days. Short term cure rates (after exclusion of superinfections and reinfections) of 79.5% (series I) and 82% (series II) were obtained one week after therapy, falling to 69% and 50%, respectively, at three to six week follow up. Sultamicillin was well tolerated. Pharmacokinetic studies confirmed intestinal absorption of both constituents in young volunteers and in the elderly.

Aged↗

Structure of Azotobacter vinelandii 7Fe ferredoxin. Amino acid sequence and electron density maps of residues.

The complete amino acid sequence of the 7Fe ferredoxin from Azotobacter vinelandii (Av Fd) was determined by repetitive Edman degradation of the whole protein and of peptides derived from CNBr cleavage or chymotrypsin digestion. The sequence was confirmed by the 2A electron density maps for the residues calculated with difference Fourier coefficients. The density maps for all residues are included in the paper. Av Fd has several important differences with the clostridial-type ferredoxins: (i) Av Fd is 106 residues (versus 55-60 for other bacterial ferredoxins); (ii) Av Fd has 9 cysteines, one of which (residue 24) is not homologous with the bacterial ferredoxins; (iii) Av Fd has 2 extra residues between 2 cysteines (residues 11 and 16) homologous to cysteines in the bacterial ferredoxins; and (iv) Av Fd has the unique sequence -Cys-Val-Glu-Val-Cys- (residues 16-20) which are two of the ligands of the 3Fe:3S center. These sequence features are compared to the sequences of various ferredoxin groups. Structure predictions for other suspected 7Fe ferredoxins are discussed.

Amino Acid Sequence↗

Structure of a 7Fe ferredoxin from Azotobacter vinelandii.

The structure of the 7Fe ferredoxin from Azotobacter vinelandii has been solved from a 3.0-A multiple isomorphous replacement map. The crystals belong to space group P43212 with a = 55.22, c = 95.20 A, and Z = 1. Heavy-atom derivatives were prepared with K2PtCl4,K2[OsO2(OH)4], and Na3RhCl6. Anomalous scattering data were collected for native (Fe) and Pt derivative crystals. The figure of merit for 3,322 reflections to 3.0 A is 0.74. The structure consists of an NH2-terminal core of residues 1-50 which form the Fe-S cluster sites, and a COOH-terminal chain of residues 51-107 which wraps around this core. The [3Fe-3S] cluster is ligated by cysteines 8, 11, 16, 20, and 49 and a sixth ligand which is either glutamic acid 18 or an exogenous small molecule. The [4Fe-4S] cluster is ligated by cysteines 24, 39, 42, and 45. The coordination of both Fe-S centers has been confirmed by fitting of the cluster atoms and residues 1-50 to unbiased 2Fo-Fc Fourier maps at 2.5-A resolution. The structure of the 3Fe center has also been confirmed with anomalous scattering difference Fourier maps using both isomorphous replacement and refined phases. The partially refined structure at 2.5 A (3,490 reflections, 6.0 sigma(F)) has R = 35%.

Azotobacter↗