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  • 1
    Electronic Resource
    Electronic Resource
    Alterations in the prooxidant and antioxidant status of human leukemic T-lymphocyte MOLT4 cells treated with potassium chromate (1995)
    Springer
    Molecular and cellular biochemistry 142 (1995), S. 61-70 
    Details
    ISSN: 1573-4919
    Keywords: chromium ; antioxidants ; free radical ; hydrogen peroxide ; superoxide dismutase ; catalase ; glutathione peroxidase ; glutathione reductase ; glucose-6-phosphate dehydrogenase ; ascorbate ; glutathione ; isoenzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The involvement of reactive oxygen species in chromate-induced genotoxicity has been postulated. Because intracellular antioxidants help in eliminating the reactive species of oxygen, we have investigated both the prooxidant and antioxidant status of human leukemic T-lymphocyte MOLT4 cells exposed to nontoxic levels of chromium(VI) in culture. The cells treated with 0 →200 μM potassium chromate in a salts/glucose medium for 2 h were found to contain significantly lower levels of both small molecular weight and macromolecular antioxidants. In particular, the levels of glutathione and ascorbate were found to decrease with increased doses of chromate exposure in a dose-dependent manner. As little as 10 μM chromate was found to decrease these small molecular weight antioxidants significantly (p〈0.01). The macromolecular antioxidants, such as glutathione peroxidase, catalase, glutathione reductase, glucose-6-phosphate dehydrogenase and superoxide dismutase were also significantly (p〈0.01) decreased by exposing the cells to as little as 10 μM chromate. Concomitantly there was a dose-dependent increase in intracellular H2O2 accumulation in cells exposed to chromium(VI). These results indicate that chromate-induced genotoxicity may be due, at least in part, to decreased levels of intracellular antioxidants in conjunction with an increased production of the reactive oxygen species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928914
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of EDTA-chelatable proteins from DNA-protein crosslinks induced by a carcinogenic chromium(VI) in cultured intact human cells (1999)
    Springer
    Molecular and cellular biochemistry 199 (1999), S. 149-162 
    Details
    ISSN: 1573-4919
    Keywords: chromium ; metal carcinogenesis ; DNA-protein crosslink ; two-dimensional gel electrophoresis ; nuclear matrix ; nuclear proteins ; NEPHGE ; X-rays ; oxidant ; MOLT4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract DNA-protein crosslinks (DPCs) were induced in intact human leukemic T-lymphocyte MOLT4 cells or isolated nuclei by treatment with potassium chromate, chromium(III) chloride hexahydrate or x-rays. The proteins complexed to DNA were analyzed by two-dimensional SDS-polyacrylamide gel electrophoresis (PAGE). A group of identical non-histone proteins was crosslinked to DNA by any of the three treatments, except that a 51 kDa basic protein was additionally complexed to DNA when either potassium chromate or chromium(III) chloride hexahydrate was the crosslinking agent. Treatment of chromate-induced DNA-protein crosslinks with EDTA or thiourea followed by ultracentifugation dissociated the major proteins from the complex indicating that these proteins were crosslinked to DNA by direct participation of a EDTA-chelatable form of chromium such as Cr(III) through sulfur containing amino acid residues. The 51 kDa protein was not seen in the post-EDTA pellet but was present in the post-thiourea pellet, indicating that it was also crosslinked to DNA by Cr(III) through non-sulfur-containing amino acids. Digestion of x-rays-induced DPCs by DNase I also revealed this protein on two-dimensional gels indicating that the same protein was also crosslinked by oxidative mechanisms. The involvement of oxidative mechanisms in the crosslinking process was indicated as the majority of the proteins in chromate-induced DPCs were resistant to EDTA and thiourea treatment, and were found to crosslink to DNA when x-rays were used as the crosslinking agent. These results suggest that the chromate-induced DPCs are formed by the generation of reactive oxygen species during the intracellular chromate reduction as well as by the biologically generated Cr(III). About 19% of DNA-protein crosslinks actually involve Cr(III) crosslinking DNA to proteins, about 14% involve Cr(III) crosslinking DNA to proteins through non-sulfhydryl containing moieties and about 5% involve Cr(III) crosslinking DNA to sulfhydryl groups on proteins. The remaining 81% of DNA-protein crosslinks appear to be oxidatively crosslinked out of which about 45% appear to be through sulfhydryl groups and another 36% appear to be through non-sulfhydryl groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006910732307
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    Paper (German National Licenses)
    Fulltext
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