Search PubMed⌕ Search

Biomedical subjects

S Dogra

Publications and source records attributed to S Dogra.

53 records · Page 3Linked to original sources
PubMed1991

Stable expression of rat cytochrome P450IA2 cDNA and hydroxylation of 17 beta-estradiol and 2-aminofluorene in V79 Chinese hamster cells.

In continuation of our work toward the establishment of a working cell bank for metabolic and toxicological studies, V79 Chinese hamster cells were genetically engineered for stable expression of rat cytochrome P450IA2. Full-length cDNA encoding rat P450IA2 was obtained by searching a cDNA library made from Aroclor 1254-induced rat liver mRNA and by joining a small 5'-end fragment to a fragment containing the rest of the cDNA. The sequence of the cDNA was confirmed by DNA sequencing and comparison to a previously published cDNA sequence. The reconstructed full-length cDNA was inserted into a simian virus 40 early promoter-containing eukaryotic expression vector and cotransferred with the neomycin phosphotransferase gene as a selective marker into V79 cells by the calcium/phosphate-coprecipitation technique. G418-resistant V79 cell clones were checked for chromosomal integration of the cDNA by Southern blotting, for expression of authentic mRNA and protein by northern and western blotting, and for P450IA2-specific enzymatic activities such as hydroxylation of 17 beta-estradiol and 2-aminofluorene.

Amino Acid Sequence↗
PubMed1991

The use of genetically engineered V79 Chinese hamster cultures expressing rat liver CYP1A1, 1A2 and 2B1 cDNAs in micronucleus assays.

We have undertaken a comparative study of the bioactivation of a panel of promutagens by V79 Chinese hamster cells genetically engineered to metabolic competence. In vitro micronucleus assays of the test agents in V79 cultures in the presence of an Aroclor induced rat S9 yielded positive results. In the genetically engineered cell lines, benzo[a]pyrene was metabolized specifically by the 3-methylcholanthrene inducible rat liver CYP1A1 (cell line XEM2) whereas cyclophosphamide increased the micronucleus frequency only in cultures expressing the phenobarbital inducible CYP2B1 (SD1). Following exposure to the mycotoxin sterigmatocystin, elevated frequencies of micronucleated cells were recorded in XEM2, SD1 and XEMd-MZ (expresses the isosafrole inducible CYP1A2) cells. The aromatic amine 2-amino-anthracene elicited a weak response in the cell line XEMd-MZ which expressed CYP1A2. This response was enhanced when this cDNA was expressed in a V79 variant cell strain which also possessed endogenous acetyltransferase activity. Upon exposure to tobacco particulate matter, a greater induction of micronuclei was observed in the XEM2 cell line compared to V79 cultures, implicating polycyclic aromatic hydrocarbons in addition to direct-acting compounds as causal agents in the genotoxicity of tobacco particulate matter. The cytokinesis blocked in vitro micronucleus assay provides a faster, simpler alternative to metaphase analysis, and kinetochore labelling techniques enable the discernment of both structural and numerical chromosome changes. The inclusion of metabolically competent test strains in the in vitro micronucleus assay therefore creates a powerful system for detecting genotoxins and may be extended to elucidate both mechanisms of bioactivation and modes of genotoxic insult.

Animals↗
PubMed1990

Successful difficult intubation. Tracheal tube placement over a gum-elastic bougie.

A randomised study was carried out to assess the effect of tracheal tube rotation on the passage of a tube over a gum-elastic bougie into the trachea in 100 patients. The effect of the presence or absence of a laryngoscope on successful tube placement was also assessed. A grade 3 difficult intubation was simulated in patients with a laryngoscope. There was a significant difference in the rates for successful first-time intubation in those patients with tube orientation of -90 degrees (with the bevel facing posteriorly) as compared with a tube orientation of 0 degrees (the normal orientation with the bevel facing left). The unsuccessful first-time intubations with a 0 degree orientation were frequently converted to successful intubations with the -90 degrees position at a second attempt. The presence of a laryngoscope in the mouth while rail-roading a tube over the bougie also made a significant difference to the rate of successful first-time intubations. The most successful method was to leave the laryngoscope in the mouth and rotate the tube to -90 degrees.

Adolescent↗
PubMed1990

Stable expression of rat cytochrome P-450IA1 cDNA in V79 Chinese hamster cells and their use in mutagenicity testing.

V79 Chinese hamster cells genetically engineered to express cytochrome P-450IA1 are reported. A full length cDNA encoding rat cytochrome P-450IA1 was obtained from a cDNA library prepared from rat liver mRNA. The cDNA was recombined with the SV40 early promoter and expressed in V79 cells. Three V79-derived P-450IA1-expressing cell lines (XEM1, XEM2, and XEM3) were established. The presence of the rat cytochrome P-450IA1 cDNA in these hamster cells was confirmed by Southern blotting. The transcription of the cDNA into mRNA and translation into the desired cytochrome P-450 protein was detected by Northern and Western blotting. The enzymatic activity was determined by the cytochrome P-450IA1-dependent oxidation of benzo[a]pyrene and 7-ethoxycoumarin. After exposure to benzo[a]pyrene, the mutant frequency increased in XEM1 and XEM2 cells and was higher than in V79 cells in the presence of an exogenous activating system. The mutant frequency was even more increased when XEM1 and XEM2 cells were exposed to the proximate mutagen (trans)-7,8-dihydroxy-7,8-dihydro-benzo[a]pyrene.

Animals↗
PubMed1990

Alterations in in vitro functional activities of alveolar macrophages exposed in vivo to mineral dusts.

To determine whether macrophages exposed to mineral dusts are altered, rats were exposed intratracheally to one of several mineral dusts, held 8 days, their lungs washed and the cellular composition of the fluid characterized morphologically and functionally. The number of cells recovered from lung washings of exposed rats increased 2 to 5 times relative to control rats; however, the percentage of such cells that were macrophages, or were capable of phagocytosis, adherence to glass or metabolism of carbohydrates via the hexose monophosphate shunt as indicated by reduction of nitroblue tetrazolium, were reduced. Silica dust produced the greatest effect, corresponding qualitatively to earlier in vivo studies.

Aluminum Oxide↗
PubMed1989

Genetically engineered V79 Chinese hamster cell expression of purified cytochrome P-450IIB1 monooxygenase activity.

Chinese hamster V79 fibroblasts, frequently used as target cells in short-term tests for mutagenicity, do not possess measurable monooxygenase activity; in particular, enzymatic oxidation of testosterone (T) cannot be demonstrated. If these V79 cells, however, had been transfected with the cDNA-encoding rat liver cytochrome P-450IIB1 under control of the SV40 early promoter, they stably expressed monooxygenase activity. These so-called SD1 cells then oxidatively metabolized T at a rate of 27 pmol/mg protein/min, converting it to 16 alpha- and 16 beta-hydroxy-T as well as 4-androsten-3,17-dione as sole metabolites in a ratio of 1.1:1.0:1.6. The regio- and stereoselective conversion of T by SD1 cells, as well as the quantitative distribution of the metabolites, corresponds well with the results reported for pure cytochrome P-450IIB1 in a reconstituted system.

Animals↗
PubMed1989

Genotoxicity of 1,4-benzoquinone and 1,4-naphthoquinone in relation to effects on glutathione and NAD(P)H levels in V79 cells.

1,4-Benzoquinone is cytotoxic in V79 Chinese hamster cells and induces gene mutations and micronuclei. The cell-damaging effects of quinones are usually attributed to thiol depletion, oxidation of NAD(P)H, and redox-cycling involving the formation of semiquinone radicals and reactive oxygen species. To elucidate the role of these mechanisms in the genotoxicity of 1,4-benzoquinone, we measured various genotoxic effects, cytotoxicity, and the levels of glutathione, NADPH, NADH, and their oxidized forms all in the same experiment. 1,4-Naphthoquinone, which does not induce gene mutations in V79 cells, was investigated for comparative reasons. The quinones had a similar effect on the levels of cofactors. Total glutathione was depleted, but levels of oxidized glutathione were slightly increased. The levels of NADPH and NADH were reduced at high concentrations of the quinones with a simultaneous increase in the levels of NADP+ and NAD+. Both compounds induced micronuclei, but neither increased the frequency of sister chromatid exchange. Only 1,4-benzoquinone induced gene mutations. This effect was observed at low concentrations, where none of the other parameters studied was affected. When the cells were depleted of glutathione prior to treatment with the quinones, the induction of gene mutations and micronuclei remained virtually unchanged. We conclude that a) induction of micronuclei and glutathione depletion by the two quinones are not linked causally, b) 1,4-benzoquinone induces gene mutations by a mechanism different from oxidative stress and glutathione depletion, and c) glutathione does not fully protect the cells against the genotoxicity of quinones.

Animals↗
PubMed1988

Changes in some histochemically demonstrable enzymes in macrophages exposed to quartz dust in vitro.

Cytochemical studies were carried out on rat alveolar and peritoneal macrophage cultures following exposure to quartz and corundum dusts. Quartz increased the number of ATPase positive cells and brought about an enhancement in the peroxidase and diffusion of the acid phosphatase activity of the exposed cells. In unexposed cell cultures, acid phosphatase activity was higher in alveolar than in peritoneal macrophages and was dependent upon the duration of incubation. Corundum produced no significant effect on the enzyme activity. Quartz treatment did not alter esterase activity whereas corundum exposed cultures showed a decline. A significant increase in mitochondrial succinic dehydrogenase activity was observed in peritoneal macrophages after quartz treatment. The results demonstrate alteration in the marker enzymes of plasma membranes, mitochondria and lysosomes during phagocytosis of quartz dust as the key event of dust cell interaction in vitro.

Acid Phosphatase↗
PubMed1988

Long-term effects of commercial and congeneric polychlorinated biphenyls on ethane production and malondialdehyde levels, indicators of in vivo lipid peroxidation.

Ethane exhalation was increased in male Sprague-Dawley rats following a single intraperitoneal (IP) injection of Aroclor 1254 (500 mg/kg). In the first 2 weeks following Aroclor 1254 treatment, the increase in ethane exhalation was due to an inhibition of metabolism of endogenous ethane rather than to an increase in ethane production. In weeks 3 and 4 following Aroclor 1254 administration, metabolic clearance of ethane returned to and exceeded control levels, while ethane production increased to approximately twice the control rates (day 30). The HPLC determination of in situ hepatic malondialdehyde levels revealed a 2-fold increase in malondialdehyde content on day 30 following the Aroclor 1254 injection. Further, parallel increases in in situ malondialdehyde levels and ethane production rates were also found 30 days following a single IP injection of 3,3',4,4'-tetrachlorobiphenyl, 2,3,4,4',5-pentachlorobiphenyl and 2,2',4,4',5,5'-hexachlorobiphenyl (300 mumol/kg). These effects were not reflected in increased diene conjugation. Redox state of the liver was largely unaffected, as evidenced by the relative concentrations of reduced and oxidized NADPH. However, minor changes in reduced and oxidized glutathione were noted.

Animals↗
PubMed1988

Stable expression of rat cytochrome P-450IIB1 cDNA in Chinese hamster cells (V79) and metabolic activation of aflatoxin B1.

V79 Chinese hamster fibroblasts are widely used for mutagenicity testing but have the serious limitation that they do not express cytochromes P-450, which are needed for the activation of many promutagens to mutagenic metabolites. A full-length cDNA clone encoding the monooxygenase cytochrome P-450IIB1 under control of the simian virus 40 early promoter was constructed and cointroduced with the selection marker neomycin phosphotransferase (conferring resistance to G418) into V79 Chinese hamster cells. G418-resistant cells were selected, established as cell lines, and tested for cytochrome P-450IIB1 expression and enzymatic activity. Two cell lines (SD1 and SD3) were found that stably produce cytochrome P-450IIB1. Although purified cytochromes P-450 possess monooxygenase activity only after reconstitution with cytochrome P-450 reductase and phospholipid, the gene product of the construct exhibited this activity. This implies that the gene product is intracellularly localized in a way that allows access to the required components. If compared with V79 cells, the mutation rate for the hypoxanthine phosphoribosyltransferase (HPRT) locus in SD1 cells is markedly increased when exposed to aflatoxin B1, which is activated by this enzyme.

Aflatoxin B1↗
PubMed1986

Atracurium infusion in the intensive care unit.

An open study of 38 infusions of atracurium in 33 patients requiring neuromuscular blockade for ventilation was carried out. Consecutive patients requiring ventilation were studied and there were no exclusions. The initial rate of infusion was 0.4 mg kg-1 h-1 and this was adjusted according to clinical observation and the results of neuromuscular stimulation. The average infusion rate in the series was 0.59 mg kg-1 h-1. Patients were sedated using a morphine infusion at a rate of 2-4 mg kg-1 h-1. Satisfactory blockade was achieved in all cases. Time for spontaneous recovery following termination of infusion was recorded, the average recovery time being 39.2 min. Emphasis was placed on recording any possible serious toxic effects attributable to long-term atracurium infusions, possible toxic effects were considered and a satisfactory explanation of such effects was found in all cases.

Adolescent↗
PubMedDate not supplied

Toxicity of trichloroethylene following inhalation and drinking contaminated water.

The neurobehavioural effects of trichloroethylene (TCE) were studied in rats following administration of the solvent orally (350, 700 and 1400 ppm in drinking water for 90 days) and through inhalation (376 ppm for 4 h a day, 5 days per week for 180 days). Various aspects of spontaneous locomotor activity were assessed at different periods after exposure through either of the routes. Oral exposure to TCE had no significant effect on spontaneous locomotor activity or cognitive ability, whereas inhalation to the solvent resulted in an increase in the distance travelled and horizontal activity counts at day 30 but a decrease at day 60 of exposure. The time spent in ambulatory and stereotypic movements as well as the number of stereotypic movements were enhanced significantly only at day 30. The resting time was decreased at day 30 but enhanced at day 60 of exposure. The learning ability was not affected significantly up to day 180. The results highlight the neurotoxic potential of inhalation exposure to TCE.

Administration, Oral↗
PubMedDate not supplied

Applications of stable V79-derived cell lines expressing rat cytochromes P4501A1, 1A2, and 2B1.

1. Chinese hamster V79-derived cell lines, stably expressing cytochromes P4501A1, 1A2, and 2B1 activities, were constructed by genetic engineering in continuation of our work to establish a battery of V79 derived cell lines designed to study the metabolism of xenobiotics. 2. Cell lines XEM1 and XEM2, expressing cytochrome P4501A1, were capable of the O-dealkylation of 7-ethoxycoumarin and the hydroxylation of benzo[a]pyrene. 3. Cell lines XEMd.MZ and XEMd.NH, expressing P4501A2, were shown to hydroxylate 17 beta-estradiol and 2-aminofluorene. 4. Cell line SD1, expressing cytochrome P4502B1, was able to hydroxylate testosterone stereo- and regio-specifically at the 16 alpha and 16 beta positions. 5. Cell lines were validated in mutagenicity, cytotoxicity, and metabolism studies employing benzo[a]pyrene, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, cyclophosphamide, ifosfamide, and picene. 6. Construction of metabolically-competent V79-derived cell lines be recombinant DNA technology will be a fundamental improvement for the evaluation of the cytotoxic, genotoxic and pharmacological properties of a chemical.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMedDate not supplied

Leprosy and herpes zoster; an association or dissociation?

Nerve involvement is common to the pathogenesis of both leprosy and herpes zoster. We report two cases of borderline leprosy in which the skin lesions characteristically spared the healed zoster scar. Possible mechanisms and relationship are discussed.

Herpes Zoster↗