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Biomedical subjects

S Chaudhuri

Publications and source records attributed to S Chaudhuri.

At least 91 records · Page 5Linked to original sources
PubMed1992

Hydrogen peroxide-induced DNA damages in vitro revealed by electron microscopy.

A plasmid pSV2neo (5.6 kb) which is a recombinant SV40-based vector was subjected to hydrogen peroxide treatment in presence of iron in vitro (Fenton reaction). Transmission electron microscopy revealed that H2O2 through the Fenton reaction introduced different types of damages in DNA. Besides the expected nicked circular and linear molecules, single-stranded loops and plasmid multimers could be characterized. These observations on DNA damages might be helpful for better understanding of the effect of hydrogen peroxide on living cells in vivo.

DNA Damage↗
PubMed1992

Effects of progesterone on some brain neurotransmitters in intact rats.

Effects of progesterone on four neurotransmitters (viz, noradrenaline, 5-HT, dopamine and histamine) of brain were seen in rats with intact ovaries. It was found that progesterone lowers the noradrenaline concentration in medulla, pons, midbrain, hypothalamus, thalami and pituitary, uniformly, when the rats were killed within 4 hours of progesterone injection. At longer intervals (48 hrs) effects of progesterone were seen when progesterone in heavy dose was administered to rats pretreated with estrogen. It is likely that one of the modes of action of the oral contraceptives may be the reduction of noradrenaline content in selected areas of brain, by progesterone. It is also suggested, therapeutic usage of progesterone carries the risk of development of depression in the user.

Animals↗
PubMed1992

Effect of hydrogen peroxide on mammalian chromatin: electron microscopic studies.

Chromatins purified from rat liver as well as from cultured Chinese hamster V79 cells were treated with hydrogen peroxide in presence of iron in vitro. When examined in a transmission electron microscope, chromatins from both the sources were found to lose the native morphology. There were evidences of aggregation of the chromatin fibers. This could be due to DNA-protein and DNA interstrand crosslinking induced by Fenton reaction.

Animals↗
PubMed1991

An improved method for isolating RNA from porcine adipose tissue.

In the present study, we describe a method that we developed to isolate total RNA from porcine adipose tissue. This method entails homogenizing porcine adipose tissue in 10 ml of 4 M guanidium thiocyanate, 25 mM sodium citrate, 0.5% Sarcosyl, 0.1 M beta-mercaptoethanol, pH 7.0, and then performing two CHCl3 extractions to remove lipid before following the procedure described by P. Chomczynski and N. Sacchi (1987, Anal. Biochem. 162, 156-159). This modification improved the yield of RNA approximately threefold (yield was 88 +/- 7 micrograms total RNA/g of tissue) without affecting RNA quality.

Adipose Tissue↗
PubMed1991

Identification of the active-site lysine residues of two biosynthetic 3-dehydroquinases.

The lysine residues involved in Schiff-base formation at the active sites of both the 3-dehydroquinase component of the pentafunctional arom enzyme of Neurospora crassa and of the monofunctional 3-dehydroquinase of Escherichia coli were labelled by treatment with 3-dehydroquinate in the presence of NaB3H4. Radioactive peptides were isolated by h.p.l.c. following digestion with CNBr (and in one case after further digestion with trypsin). The sequence established for the N. crassa peptide was ALQHGDVVKLVVGAR, and that for the E. coli peptide was QSFDADIPKIA. An amended nucleotide sequence for the E. coli gene (aroD) that encode 3-dehydroquinase is also presented, along with a revised alignment of the deduced amino acid sequences for the biosynthetic enzymes.

Amino Acid Sequence↗
PubMed1991

Risk factors for injury during adolescence.

Injuries kill more American adolescents than all other diseases combined. It is unclear, however, if adolescents are able or willing to provide the information necessary to characterize their risk for injury. Our objective was to determine if adolescents hospitalized for severe injury are more likely than those hospitalized for acute illness to describe risk factors for injury such as: previous injury, family dysfunction, recent stress, or substance use. All patients completed the Offer Self-Image Questionnaire, the Life-Events Scale for Adolescents, the Adolescent Alcohol-Involvement Scale, and the NIDA Adolescent Drug Use Survey. There were no differences between injured and ill adolescents in demographics, impulse control, emotional tone, perceived family function, alcohol scores, or use of cigarettes, marijuana, or other illicit drugs. The groups differed significantly in sex, previous serious injury, previous hospitalization for injury, injury after alcohol or drug use, and life-event scores. The most common life stresses reported were parental or sibling hospitalization, death of a grandparent, school failure or suspension, getting a summer job, and breaking up with a girl/boy friend. Two variables comprised a stepwise logistic regression model designed to differentiate injured from ill adolescents: male sex and life-event score. We conclude that adolescent boys with recent stressful events may be at high risk for unintentional injury.

Adolescent↗
PubMed1991

Highly clustered zein gene sequences reveal evolutionary history of the multigene family.

We have determined the nucleotide sequences of zein cDNA clones ZG14, ZG15, and ZG35. The three clones have 95 to 98% homology to the previously published sequence of clone A20, and 84% homology to sequences of the zein subfamily A30. Comparison of all sequences of the A30 and A20 subfamilies highlights the following features: the 5' nontranslated regions are 68 and 57 nucleotides in length for the A20- and A30-like mRNAs, respectively, and contain at least three repeats of the consensus sequence ACGAACAAta/gG; the majority of these genes are highly clustered as judged from pulsed-field gel electrophoresis of high molecular weight maize DNA. Furthermore, we discuss a model for the evolution of the multigene family which stresses the special importance of unequal crossingover and gene conversion in this system.

Base Sequence↗
PubMed1991

Sheep erythrocytes provide metabolic triggers for tumour phagocytosis in polymorphonuclear neutrophils: a possible mechanism of tumour inhibition in mice.

Intraperitoneal (i.p.) injection of 7% Sheep Erythrocytes (SRBC) was found to inhibit growth of a transplanted tumour and exhibit a consequent increase in total survival compared to untreated tumour controls. In an attempt to probe into the mechanism(s) involved, functional aspects of Polymorphonuclear Neutrophils (PMNs) were investigated in terms of their 'metabolic (respiratory) burst' during tumour phagocytosis. Both NADPH-Oxidase mediated superoxide anion (O2-.) formation (NBT reduction) and Myeloperoxidase (MPO) mediated oxidisable halide incorporation (131I incorporation) were found to be highly stimulated by SRBC in normal (CS) and tumour bearing counterparts (TS). A little tumour mediated residual inhibition persists on the MPO system in PMNs of animals with tumour plus SRBC (TS) which, however, showed an obvious bonus effect over the tumour controls (TC). The results suggest a possible mechanism of tumour inhibition by SRBC in mice with the involvement of highly stimulated phagocytic metabolism in PMNs.

Animals↗
PubMed1990

Microstructure and growth of ZnTe films.

The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.

Tellurium↗
PubMed1990

Human immunodeficiency virus infection is efficiently mediated by a glycolipid-anchored form of CD4.

Two broad roles have been revealed for the CD4 molecule. It serves as a receptor for both class II major histocompatibility complex molecules and human immunodeficiency virus (HIV). Upon binding class II major histocompatibility molecules, CD4 functions to enhance T-cell activation. By binding to CD4, HIV gains entry into the cell. We have used a chimeric molecule of CD4 and lymphocyte function-associated antigen 3 (LFA-3), CD4PI, which lacks a membrane-spanning domain and is instead anchored in the membrane by linkage to glycosyl-phosphatidylinositol. To further define the structural attributes of viral receptors, and specifically those of CD4 required for HIV infection, we have expressed CD4PI and CD4 in a human T-cell line, HSB-2. We find that CD4PI is able to mediate infection of these cells by HIV with similar, if not greater efficiency, compared with wild-type CD4. Thus the membrane-spanning region of CD4 is not required for HIV infection, and a lipid-anchored protein can serve as a viral receptor.

Amino Acid Sequence↗
PubMed1990

Antitumor activity of L-asparaginase from Cylindrocarpon obtusisporum MB-10 and its effect on the immune system.

L-Asparaginase from Cylindrocarpon obtusisporum MB-10 inhibits the growth of Ascites Fibrosarcoma and Dalton's Lymphoma tumor cells in vivo and significantly increases the survival rate of tumor bearing mice. The enzyme-treated normal mice become more healthy and survive longer than their usual life span. The spleen size of normal animals treated with L-asparaginase become larger, and the number of their rosetting T-lymphocytes along with the capacity of SRBC constellation gets increased. The surface topography of splenic T-lymphocytes of enzyme-treated mice exhibits some extensions of different parts of the membrane with ruffling of surface and formation of innumerable blebs, foldings, microvilli, etc. The adherence of leukocytes of peritoneal exudate cells of these mice is also enhanced. All results suggest that C. obtusisporum MB-10 L-asparaginase is active against tumors and non-immunosuppressive, and it deserves to be an immunotherapeutic agent.

Animals↗
PubMed1989

Pineal activity during the seasonal gonadal cycle in a wild avian species, the tree pie (Dendrocitta vagabunda).

The aim of the present investigation was to study the pineal activity during the seasonal gonadal cycle in both sexes of the Indian tree pie (Dendrocitta vagabunda). The findings revealed that the nuclear diameter of the pineal parenchymal cells moderately decreased and was followed by a moderate increase in the cell population density (per microscopic field of the pineal sections) and serotonin content of the gland during the progressive phase. The values of these parameters were further altered (decreased nuclear diameter with increased cell population density and serotonin level) during breeding but were reversibly altered to some extent during the regression phase, and further altered during the nonbreeding phase in both sexes of the birds. It is suggested that the pineal activity distinctly varies with the seasonal gonadal cycle, being minimum during breeding and maximum during nonbreeding in both sexes of the tree pie.

Animals↗
PubMed1989

Serum phospholipid fractions measured by two dimensional thin layer chromatography in normal pregnancy.

Serum phospholipid fractions were quantitated by two dimensional thin layer chromatography in 85 apparently normal pregnant women at different gestational period. Fifteen healthy non-pregnant women matched for age served as controls. Normal chromatogram showed eight spots of serum phospholipid viz., phosphatidic acid (PA, 3.9 +/- 0.5%), cardiolipin (C, 7.2 +/- 0.4%), phosphatidylethanolamine (PE, 10.6 +/- 1.1%), phosphatidylglycerol (PG, 3.2 +/- 0.6%), lecithin (L, 34.5 +/- 1.8%), sphingomyelin (S, 31.0 +/- 1.4%), lysolecithin (LL, 8.6 +/- 1.2%) and phosphalidylionositol (PI, 1.0 +/- 0.2%). Serum total phospholipid which increased with gestational age, being lowest at 6 wk (220.2 +/- 4.8 mg/dl) and highest at 38 wk (290.3 +/- 4.5 mg/dl), started declining at term (275.8 +/- 5.8 mg/dl) and returned to levels in normal nonpregnant women (214.1 +/- 4.7 mg/dl) at 4 wk after delivery (217.2 +/- 3.3 mg/dl). PG was absent in both the first and second trimester and first appeared between 31-32 wk, i.e., in the third trimester of pregnancy when the mean per cent of PG was 0.7 +/- 0.4 per cent. During the first trimester when the L/S ratio was less than 1.2 the PI level was low (0.8 +/- 0.2%). Parallel to the increase in the L/S ratio to 2.0, the content of PI increased to 2.6 +/- 0.4 per cent. PG first appeared (0.7 +/- 0.4%) and PI concomitantly decreased (2.1 +/- 0.3%) when the L/S ratio exceeded 2.0 at 31-32 wk. Sequential analysis of maternal serum phospholipid fractions may be used as an additional tool in predicting gestational age of normal growing pregnancy.

Adult↗
PubMed1989

Risk factors for attempted suicide during adolescence.

It is unknown whether adolescents can provide the information necessary to identify their risk for attempted suicide. The present study was designed to determine whether data collected directly from adolescents can be used to develop a simple model for differentiating suicidal from nonsuicidal adolescents. Patients aged 13 to 19 years hospitalized for medical complications of serious suicide attempts (n = 56) or for acute illnesses unrelated to injuries or ingestions (n = 248) completed self-administered questionnaires pertaining to psychosocial function, recent stress, alcohol and drug use, and health care use. Compared with ill adolescents, suicidal adolescents had poorer mental health, impulse control, family relationships, and school performance; higher 3-month stress scores and alcohol-use scores; and more use of 7 of 12 drugs (P less than .05). Compared with ill adolescents, suicidal adolescents were more likely to report previous suicide attempts (39% vs 10%, P less than .001) and previous mental health care (27% vs 8%, P less than .001) but were less likely to identify a primary care site (61% vs 87%, P less than .001). In a logistic regression model based on previous suicide attempts, previous mental health care, poor school performance, marijuana use, and dependence on the emergency room for primary care, 84% of the suicidal and 55% of the ill adolescents were correctly identified. If validated prospectively, these five self-administered questions may constitute a helpful screen for the rapid identification of suicidal adolescents.

Adolescent↗