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Biomedical subjects

S Dey

Publications and source records attributed to S Dey.

At least 19 recordsLinked to original sources
PubMed1992

Construction of a chimeric ArsA-ArsB protein for overexpression of the oxyanion-translocating ATPase.

Resistance to toxic oxyanions of arsenic and antimony in Escherichia coli is conferred by the conjugative R-factor R773, which encodes an ATP-driven anion extrusion pump. The ars operon is composed of three structural genes, arsA, arsB, and arsC. Although transcribed as a single unit, the three genes are differentially expressed as a result of translational differences, such that the ArsA and ArsC proteins are produced in high amounts relative to the amount of ArsB protein made. Consequently, biochemical characterization of the ArsB protein, which is an integral membrane protein containing the anion-conducting pathway, has been limited, precluding studies of the mechanism of this oxyanion pump. To overexpress the arsB gene, a series of changes were made. First, the second codon, an infrequently used leucine codon, was changed to a more frequently utilized codon. Second, a GC-rich stem-loop (delta G = -17 kcal/mol) between the third and twelfth codons was destabilized by changing several of the bases of the base-paired region. Third, the re-engineered arsB gene was fused 3' in frame to the first 1458 base pairs of the arsA gene to encode a 914-residue chimeric protein (486 residues of the ArsA protein plus 428 residues of the mutated ArsB protein) containing the entire re-engineered ArsB sequence except for the initiating methionine. The ArsA-ArsB chimera has been overexpressed at approximately 15-20% of the total membrane proteins. Cells producing the chimeric ArsA-ArsB protein with an arsA gene in trans excluded 73AsO2- from cells, demonstrating that the chimera can function as a component of the oxyanion-translocating ATPase.

Adenosine Triphosphatases↗
PubMed1992

Design of peptides: synthesis, crystal structure, molecular conformation, and conformational calculations of N-Boc-L-Phe-Dehydro-Ala-OCH3.

It is noteworthy that the dehydro-Ala residue adopts an extended conformation that is different than those observed in dehydro-Phe, dehydro-Leu, and dehydro-Abu. The peptide N-Boc-L-Phe-dehydro-Ala-OCH3 (C18H24N2O5) was synthesized by the usual workup procedure and finally by converting N-Boc-L-Phe-L-Ser-OCH3 to N-Boc-L-Phe-dehydro-Ala- OCH3. It was crystallized from its solution in a methanol-water mixture at room temperature. The crystals belong to the monoclonic space group P2(1), with a = 9.577(1) A, b = 5.195(3) A, c = 19.563(3) A, beta = 94.67(5) degrees, V = 970.1(6) A3, Z = 2, dm = 1.201(5) Mg m-3, dc = 1.197(5) Mg m-3. The structure was determined using direct method procedures. It was refined by a full-matrix least-squares procedure to an R value of 0.048 for 1370 observed reflections. The C2 alpha-C2 beta distance is 1.327(8) A, while the bond angles N2-C2 alpha-C2' and C1'-N2-C2 alpha are 109.8(5) degrees and 127.8(5) degrees, respectively. The backbone adopts a nonspecific conformation with dehydro-Ala in a fully extended conformation with the following torsion angles: theta 1 = 175.2(4) degrees, omega 0 = 170.2(4) degrees, phi 1 = 135.8(5) degrees, psi 1 = -22.6(6) degrees, omega 1 = 168.5(5) degrees, phi 2 = -170.3(5) degrees, psi 2T = -178.6(5) degrees, theta T = 178.4(7) degrees. The rigid planar and trans conformation of dehydro-Ala forces Phe to adopt a strained conformation. The Boc group has a trans-trans conformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Dipeptides↗
PubMed1992

Exercise training: significance of regional alterations in serotonin metabolism of rat brain in relation to antidepressant effect of exercise.

Alterations of 5HT and its chief metabolite 5HIAA were studied in four regions of the rat brain following acute 1-h swim exercise and 4 week chronic swim exercise (30 min/day, 6 days per week). Acute exercise significantly increased the synthesis and metabolism of 5HT in brain stem. Hypothalamus also showed increased levels of 5HT. However, no changes were observed in the cerebral cortex and hippocampus. Chronic exercise activated not only the synthesis but also the metabolism of 5HT in the cerebral cortex; this neuronal adaptation was sustained even 1 week after the termination of training. In brain stem, increased 5HT turnover was observed immediately after training. In hypothalamus, decrease in 5HT and 5HIAA levels occurred immediately after training, followed by a rebound increase in their levels after 1 week posttraining rest. In hippocampus, a delayed effect was observed, because 5HT level was unaltered immediately after the training, but its turnover decreased after 1 week rest. These findings have been discussed in an attempt to explain the antidepressant effect of exercise based on the 5HT deficiency theory of endogenous depression.

Animals↗
PubMed1992

Modification of apomorphine-induced behaviour following chronic swim exercise in rats.

Four week swim exercise schedule (45 min day-1, 6 days each week) in rats led to a significant adaptive change in functional responsiveness of dopamine receptors (auto-receptors) in the nigrostriatal and mesolimbic system that was evident from the modification of behavioural responses elicited by a low dose of apomorphine, a direct acting dopamine receptor agonist. Thus, a remarkable increase in yawning response, development of full blown stereotypy, as well as profound attenuation of locomotory and hypothermic response was observed in exercise-trained rats as compared with the non-exercise group (control), following intraperitoneal administration of 0.3 mg kg-1 of apomorphine.

Analysis of Variance↗
PubMed1992

Age-specific development of malate-aspartate shuttle in the liver and kidney of mice.

The activities of malate-aspartate shuttle enzymes were measured in the liver and kidney of 15-, 30-, and 60-day old mice. The results indicate that the activities (U/mg protein) of both isoenzymes (cytosolic and mitochondrial) of both malate dehydrogenase and aspartate aminotransferase are significantly higher in the liver of 15-day old mice than in the liver of 30- and 60-day old animals. However, the shuttle enzymes showed a peak value in the kidney of 30-day old mice. In vitro reconstitution of malate-aspartate shuttle showed a similar pattern of activity in the tissues studied. These findings suggest that the activity of malate-aspartate shuttle is expressed differentially in these tissues of mice at different postnatal ages.

Aging↗
PubMed1991

Synthesis, crystal structure and molecular conformation of N-Ac-dehydro-Phe-L-Val-OH.

The peptide N-Ac-dehydro-Phe-L-Val-OH (C16H20N2O4) was synthesized by the usual workup procedure. The peptide crystallizes from its solution in acetonitrile at 4 degrees in hexagonal space group P6(5) with a = b = 11.874(2)A, c = 21.856(9) A, V = 2668(1) A3, Z = 6, dm = 1.151(3) g cm-3, dc = 1.136(4) g cm-3, CuK alpha = 1.5418 A, mu = 0.641 mm-1, F(000) = 972, T = 293 K. The structure was solved by direct methods and refined by least-squares procedure to an R value of 0.074 for 1922 observed reflections. In the dehydro-residue, the C1 alpha-C1 beta distance is 1.35(1) A while the bond angle C1 alpha-C1 beta-C1 gamma is 131.2(9) degrees. The backbone torsion angles are: omega 0 = 172(1) degrees, phi 1 = -60(2) degrees, psi 1 = -31(2) degrees, omega 1 = -179(1) degrees, phi 2 = 59(2) degrees. These values suggest that the peptide tends to adopt an alternating right-handed and left-handed helical conformation. The side chain torsion angles are: chi 1(1) = -6(2) degrees, chi 1(2.1) = -1(2) degrees, chi 1(2.2) = -178(2) degrees, chi 2(1.1) = 63(2) degrees and chi 2(1.2) = -173(1) degrees. These values show that the side chain of dehydro-Phe is planar whereas the valyl side chain adopts a sterically most preferred conformation. The molecules, linked by intermolecular hydrogen bonds and van der Waals forces, are arranged in helices along the c-axis. The helices are held side-by-side by van der Waals contacts.

Crystallography↗
PubMed1989

Ovarian damage to Channa punctatus after chronic exposure to low concentrations of Elsan, mercury, and ammonia.

Histopathological changes were induced in the ovary by chronic nonlethal levels of Elsan (211 ppb), mercury (16.7 ppb), and ammonia (15.64 ppm). In the breeding season, treated Channa punctatus revealed a significant decrease in ovarian weight throughout the duration of the experiment. Acute changes were noted in the diameter and percentage occurrence of the different stages of oocytes. In all cases, stage I oocytes revealed no difference in diameter with respect to control although they demonstrated an increase in the percentage occurrence. For stages II and III, a remarkable decrease occurred in both the number and the diameter of these mature oocytes. The preponderance of stage I and destruction of stage II and stage III oocytes in all three treatments indicate that chemically diverse xenobiotics have equal reproductive toxicity in fish, interfering with their breeding.

Ammonia↗
PubMed1989

Influence of industrial pollutants on thyroid function in Channa punctatus (Bloch).

A 30 day exposure of C. punctatus to sublethal levels of phenol, ammonia, mercuric chloride, cadmium chloride and a mixture of the four resulted in an overall activation of guaiacol peroxidase and depression of iodide peroxidase (IPOD) activity and blood T4 titre. Interestingly enough, in case of 15 day ammonia and 1 day mercury exposures, an increase of IPOD activity was accompanied by a decrease in T4 titre. In general, phenol, mercury, cadmium and the mixture of pollutants were found to inhibit LP activity by 56% to 85% while ammonia inhibited lysosomal protease (LP) activity by 70%. Alterations in acid phosphatase (AP) activity indicate changes in the lysosomal membrane characteristics caused by these toxicants. Considering the concomitant alterations in IPOD, T4, LP and AP it is surmised that thyroid function in C. punctatus is influenced by the pollutants by two pathways, one via IPOD pathway affecting T4 synthesis and the other via lysosomal pathway affecting T4 release.

Ammonia↗
PubMed1989

Choledochal cyst.

Explore the source record for details and available documents.

Adolescent↗
PubMed1989

Hysteria in children and adolescents.

Thirty eight cases of childhood hysteria admitted to a rural medical college hospital, were studied for epidemiological characteristics, clinical presentation, precipitating factors and psychosocial environment and behaviour. Hysteria was commonly seen during adolescence (73.2%) and in males (63.2%). It was more common in the lower socio-economic status (60.5%) and in children for nuclear (94.7%) and large size families (81.6%). Eldest or youngest siblings of the families were found to be more prone to develop hysteria. Motor symptoms were most frequently observed (71.1%) and 55.3% cases had more than one symptom at the time of presentation. In a majority of cases hysteria was acute in onset. Precipitating psychological event was identified in 81.6% cases; scolding (26.3%) being the commonest followed by school avoidance (13.2%), examination fear (10.5%) and quarrel with peers (10.5%). Past history of 52.6% of patients of hysteria and 18.4% of their parents revealed subtle behavioural abnormalities. All patients improved with psychotherapy and modification of the psychosocial environment.

Adolescent↗
PubMed1987

Outbreak of febrile illness due to dengue virus type 3 in Calcutta during 1983.

An epidemic of dengue fever broke out in Calcutta between July and August 1983. Persons of all age groups were affected with a preponderance of young adults. Haemorrhagic manifestations and shock were not observed. Virus was isolated from 4 acute phase sera and identified as dengue type 3 (DEN-3), the first isolation of DEN-3 virus in Calcutta. Serotesting with 9 paired blood samples established dengue infection in 7 and a flavivirus group reaction in 2. Examination of 36 single sera revealed presumptive dengue infection in 15 and a flavivirus group reaction in 17, while the remaining 4 were negative to all flavivirus antigens.

Adolescent↗
PubMed1987

The effect of torso geometry on magnetocardiographic isofield maps.

Using a computer model of a realistically shaped human torso with lungs and intraventricular blood masses, we have assessed how torso geometry and composition affect the extracorporal magnetic field produced by a current dipole in the centre of the ventricular mass. The magnetic induction vector B arising from the dipole has been calculated at points of a precordial measuring grid and the influence of boundaries has been assessed qualitatively, by comparing contour maps of the B component normal to the torso's frontal plane. We found that the maps reflected relatively faithfully the underlying dipolar source for the homogeneous torso and even for the torso with lungs. However, the intraventricular blood masses caused a noticeable rotation of the maps' extrema. Both lungs and blood masses tended to swing the distribution towards the distribution that would have been caused by a dipole oriented along the anatomical axis of the heart.

Computer Simulation↗