摘要:

AbstractThe relationship between the cell density utilized in the selection for 6‐thioguaninine‐resistant mutants induced by ethyl methanesulfonate and the recovery of mutant colonies was determined in Chinese hamster ovary cells. After an adequate phenotypic expression time of 9 days post mutagen treatment, cultures were plated in selection medium at cell densities ranging from 5 × 104to 2 × 106cells/100 mm dish (0.9 to 36.0 × 103cells/cm2). A decline in the frequency of mutant colonies was observed with increasing cell density, and analysis of the data showed that the loss was independent of the frequency of mutants in the cell population. This loss occurred in an exponential fashion, consistent with a random‐target effect. Regression analysis of the data points yielded a best‐fit line defined by the equation log(y) = 2.01 ‐ 0.26(10−6) x, where y = percentage recovery and × = selection cell density (cells per 100 mm dish). This study defines the cell densitydependent loss of mutants under selection conditions, and provides a basis for further study of the influence of agents on cell contact‐mediated crossfeeding and possible effects on mutation induction determinations. These results also demonstrate the importance of the use of appropriate cell densities in

ISSN:0192-2521    

DOI:10.1002/em.2860040602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe cytogenetic effects of exposure of mice to shale‐derived oils by either skin painting or intraperitoneal injection were examined. Skin painting with 40 mg crude oil every other day for five weeks had no effect on the frequency of chromosomal aberrations observed in the bone marrow. Three daily intraperitoneal injections of 0.5–2.0 ml/kg per day of a crude shale oil from an aboveground retort induced a dose‐related increase in the frequency of aberrations observed. A hydrotreated sample of this oil produced a similar pattern of aberration induction, but at lower frequencies. Crude shale oil from a modified in situ retort induced the highest frequency of chromosomal aberrations at the 0.5 ml/kg dose; lower frequencies were induced at the 1.0 ml and 2.0 ml/kg doses. Of the three shale oils tested, only the crude oil from the aboveground retort induced increased frequencies of sister chromatid exchanges and only at doses that also induced structural aberrations. These studies indicate that structural aberration analysis is a more sensitive test than sister chromatid exchange analysis for the type of DNA damage induced by shale‐derived oils in murine bone marro

ISSN:0192-2521    

DOI:10.1002/em.2860040603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe persistence of the lesions leading to sister chromatid exchanges (SCEs) following acute exposure of Chinese hamster ovary (CHO) cells to direct‐acting chemical mutagens was measured. The results revealed that these lesions (and consequently SCEs) are rapidly eliminated from cells. SCE levels fell to near control values by the third or fourth day (six and eight cell cycles, respectively) following exposure of CHO cells to quinacrine mustard (QM) and mitomycin C (MMC). In contrast, cells exposed to methyl methanesulfonate (MMS) showed a small but significant increase in SCE level over control up to and including the fifth day following exposure (approximately ten cell cycles), suggesting that the behavior of these lesions in cells is influenced, at least in part, by the mechanism by which a specific agent interacts with DNA. The possibility that the decline in SCE level was due to the loss of cell populations with high numbers of exchanges was eliminated by the assessment of cloning efficiencies of treated and control culture

ISSN:0192-2521    

DOI:10.1002/em.2860040604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractOzone, a highly reactive three‐atom allotrope of oxygen, is formed in high concentrations in various kinds of microenvironments, including electron microscopes, office copy machines, and X‐ray devices. Mutagenicity and action modus operandi of ozone suggest its radiomimetic property. In order to test for ozone‐induced dominant lethals in Drosophila virilis, we determined that four‐hr and longer exposures to 30 ± 2 ppm ozone were lethal on or before day 25 postexpo‐sure. Accordingly, we used a three‐hr ozone exposure to investigate dominant lethals induced at specific spermatogenic stages. Ozone increased the percentage of dominant lethals in the stages of spermatogenesis which were investigated. Under the conditions of this experiment, the sperm‐sperm bundle stage showed the greatest percentage of dominant lethals induced by ozone. Meiotic cells were the least sensitive to ozone mutagenicity. The induction of dominant lethals is discussed on the basis of chemical reactions from the molecular decomposition of water by radiations and/or ozone. Alternative explanations are presented due to the definition of induced dominant lethals and to associated modifications from

ISSN:0192-2521    

DOI:10.1002/em.2860040605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractA simplified method for the quantitation of DNA damage in nonlabeled hepatocytes, using a fluorometric technique for the quantitation of DNA in conjunction with a modification of the alkaline elution technique of Kohn et al [1976], following chemical treatment in vitro and in vivo, is described. Freshly isolated hepatocytes were treated in vitro with 2‐acetylaminofluorene, aflatoxin B1, and dimethylnitrosamine, then examined for DNA damage. Exposure to each of these compounds resulted in DNA damage. Hepatocytes isolated from rats treated with the hepatocarcinogens 2‐acetylaminofluorene, benzidine, azoxymethane, dimethylhydrazine, dimethylnitrosamine, and diethylnitrosamine sustained DNA damage as evidenced by increased alkaline elution. DNA damage in hepatocytes was also observed as a result of treatment with methylmethanesulfonate and azaserine. The hepatotoxin carbon tetrachloride did not induce DNA damage in hepatocytes isolated from treated animals. A comparison of the induction of DNA damage and of unscheduled DNA synthesis in hepatocytes from the same animals revealed that in most cases the extent of elution of DNA from filters was proportional to the induction of DNA rep

ISSN:0192-2521    

DOI:10.1002/em.2860040606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractInduction of sex‐linked recessive lethal mutations, heritable translocations and genetic crossing‐over were studied in Drosophila melanogaster males treated as adults and as embryos with different concentrations of gaseous DBCP. Adults exposed to 30 ppm/hr of the compound did not produce a significant number of sex‐linked recessive lethal mutations in treated spermatozoa, spermatids, or spermato‐cytes. However, at an exposure of 17.7 ppm/hr, a weak mutagenic effect was observed in embryonic spermatogonia. No translocation was scored in 4032 tested chromosomes from adults treated with 150 ppm/hr. However, a significant number of spermatocytial crossovers were induced after an exposure of 120

ISSN:0192-2521    

DOI:10.1002/em.2860040607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractStrains deficient in recombinational repair (recA−) failed to be reverted by MNNG. Caffeine was found to efficiently repress MNNG‐induced reversions with proficient and deficient (uvrB−) excision repair strains. The presence of the resistance plasmid pKM 101 had no influence on the effectiveness of caf

ISSN:0192-2521    

DOI:10.1002/em.2860040608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractIn vivo DNA precursor imbalances can have profound genetic consequences in prokaryotes and eukaryotes. In vitro studies have demonstrated that DNA replication fidelity is dependent on correct balances of deoxyribonucleoside triphosphates during DNA synthesis. These findings suggest that intracellular concentrations of DNA precursors may be regulated in order to minimize the frequency of genetic change. In addition, they indicate the existence of important nonDNA targets for the induction of mutation, recombination, chromosome aberrations, etc. In this article, the genetic effects of deoxyribonueleotide pool imbalances are reviewed.

ISSN:0192-2521    

DOI:10.1002/em.2860040609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

ISSN:0192-2521    

DOI:10.1002/em.2860040610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

ISSN:0192-2521    

DOI:10.1002/em.2860040601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY