bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro cytotoxic and cell transforming activities exerted by the pesticides cyanazine, dithianon, diflubenzuron, procymidone, and vinclozolin on BALB/c 3T3 cells
Authors: Perocco Paolo , Colacci Annamaria , Grilli Sandro
Published: February 2007

Cytotoxic and cell transforming activities of the pesticides cyanazine, diflubenzuron, dithianon, procymidone, and vinclozolin were investigated in vitro by utilizing the BALB/c 3T3 cell transformation test performed in the presence or in the absence of S‐9 mix as an exogenous bioactivation system for the chemicals. All the assayed pesticides were cytotoxic in the absence of S‐9 mix, whereas only dithianon exerted cytotoxic effects in the presence of metabolic activation. All the chemicals tested did induce BALB/c 3T3 cell transformation, to a various extent, in the absence of S‐9 mix. Cell transforming ability of cyanazine and diflubenzuron was not detectable in the presence of S‐9. © 1993 Wiley‐Liss, Inc.
Selective aflatoxin B1‐induced sister chromatid exchanges and cytotoxicity in differentiating B and T lymphocytes in vivo
Authors: Potchinsky Merle B. , Bloom Stephen E.
Published: February 2007

The purpose of this study was to assess the genotoxic and cytotoxic effects of the fungal metabolite aflatoxin B1 (AfB1) on the developing immune system of the chick embryo, a model in vivo system. Of particular interest was the assessment of AfB1 ‐mediated selective toxicity toward developing B lymphocytes as compared to T lymphocytes. In vivo bromodeoxyuridine (BrdU) labelling of DNA was used to detect the induction of sister chromatid exchanges (SCE) in lymphocytes and to assess the progression of these cells through successive cell cycles. Cytotoxicity was also assessed by studying the entrance and maintenance of cells in mitosis (mitotic index). Graded doses of AfB1 (1.09–17.4 μ/g embryo) were applied to chick embryos of 18 days of incubation (Dl). Embryos also received two doses of BrdU at 3 mg/200 μ (3 hr apart) to provide continuous labelling of B and T lymphocyte replicating DNA. B and T lymphocytes were harvested 20 hr post‐AfB1/BrdU exposure from the bursa and thymus, respectively, and were processed for cytogenetic analyses. AfB1 induced dose‐related increases in SCE in B lymphocytes; this induction was 6‐ to 8‐fold that of controls at the higher doses tested, AfB1 ‐mediated induction of SCE in T cells was just 2‐fold that of controls at the highest dose tested. AfB1 reduced the progression of B cells and to a lesser extent T ceels through successive rounds of replication. Furthermore, AfB1 dramatically reduced the mitotic index of B cells but not of T cells. These data indicate both selective genotoxicity and cytotoxicity of AfB1 toward B cells in the late stage embryo. © 1993 Wiley‐Liss, Inc.
How much do we know about spontaneous human mutation rates?
Authors: Crow James F.
Published: February 2007

The much larger number of cell divisions between zygote and sperm than between zygote and egg, the increased age of fathers of children with new dominant mutations, and the greater evolution rate of pseudogenes on the Y chromosome than of those on autosomes all point to a much higher mutation rate in human males than in females, as first pointed out by Haldane [Ann Eugen 13:262–271, 1947] in his classical study of X‐linked hemophilia. The age of the father is the main factor determining the human spontaneous mutation rate, and probably the total mutation rate.

The total mutation rate in Drosophila males of genes causing minor reduction in viability is at least 0.4 per sperm, and may be considerably higher. The great mutation load implied by a rate of ≈ 1 per zygote can be greatly ameliorated by quasi‐truncation selection.

Corresponding data are not available for the human population. The evolution rate of pseudogenes in primates suggests some 102 new mutations per zygote. Presumably the overwhelming majority of these are neutral, but even the approximate fraction is not known.

Statistical evidence in Drosophila shows that mutations with minor effects cause about the same heterozygous impairment of fitness as those that are lethal when homozygous. The magnitude of heterozygous effect is such that almost all mutant genes are eliminated as heterozygotes before ever becoming homozygous. Although quantitative data in the human species are lacking, anecdotal information supports the conclusion that partial dominance is the rule here as well. This suggests that if the human mutation rate were increased or decreased, the effects would be spread over a period of 50–100 generations. © 1993 Wiley‐Liss, Inc.
Induction of micronuclei by bleomycin in G0 human lymphocytes: I. Dose‐response and distribution
Authors: Hoffmann George R. , Colyer Shirley P. , Littlefield L. Gayle
Published: February 2007

The cytokinesis‐block micronucleus assay was used to investigate the induction of chromosomal damage by bleomycin in G0 human lymphocytes. A dose‐dependent increase in the frequency of micronuclei was observed in binucleate cells, and the frequency approached 0.5 micronuclei per cell at the highest dosage tested. The distribution of micronuclei among cells was overdispersed, rather than fitting a Poisson distribution. Even at the highest dosage, more than two‐thirds of the cells did not contain micronuclei, while some cells were highly damaged, containing more than 4 micronuclei percell. © 1993 Wiley‐Liss, Inc.
Evaluation of a three‐exposure mouse bone marrow micronucleus protocol: Results with 49 chemicals
Authors: Shelby M. D. , Erexson G. L. , Hook G. J. , Tice R. R.
Published: February 2007

Forty‐nine chemicals were tested in a mouse bone marrow micronucleus test that employed three daily exposures by intraperitoneal injection. Bone marrow samples were obtained 24 hr following the final exposure. Twenty‐five rodent carcinogens and 24 noncarcinogens were selected randomly from the 44 carcinogens and 29 noncarcinogens used by Tennant et al. (Science 236:933–941, 1987) to evaluate the performance of four in vitro genetic toxicity tests. As in that study of in vitro tests, the micronucleus tests were conducted with coded chemicals and test results (positive or negative) were determined prior to decoding. This study was conducted as part of an effort to assess the ability of the micronucleus test to discriminate between rodent carcinogens and noncarcinogens and to determine its potential role, in combination with other short‐term tests, in identifying genotoxic chemicals that present a carcinogenic hazard.

Nine chemicals were judged to be positive in the micronucleus test. This relatively low number of positive results, along with published and unpublished results from rodent micronucleus and chromosome aberration assays on several of these 49 chemicals, contributed to the conclusion that a single micronucleus test protocol is not adequate to detect all chemicals capable of inducing chromosomal damage in the bone marrow. However, a combination of two relatively simple assays such as the Salmonella and micronucleus tests can provide important information on the genetic toxicity of test chemicals and may provide guidance on the need for and the nature and extent of further toxicity studies. © 1993 Wiley‐Liss, Inc.
Structural relationships between mutagenicity, maximum tolerated dose, and carcinogenicity in rodents
Authors: Rosenkranz Herbert S. , Klopman Gilles
Published: February 2007

The CASE structure‐activity relational system was applied to a study of the structural bases of toxicity as expressed in the maximum tolerated dose (MTD) of a group of chemicals for which rodent carcinogenicity and mutagenicity data were also available. All of the results were obtained under the aegis of the U.S. National Toxicology Program. The analyses revealed that there was a structural basis for the MTD in mice and in rats and that these overlapped considerably. There was also some overlap between structural determinants of the MTD and of carcinogenicity in rodents but there was also a significant “antagonism” between such fragments; i.e., fragments associated with high toxicity (low MTD) were associated with lack of carcinogenicity and vice versa. The highest overlaps observed were between the structural determinant for a low MTD (i.e., high toxicity) and mutagenicity in Salmonella. © 1993 Wiley‐Liss, Inc.
DNA response to bleomycin in mammalian cells with variable degrees of chromatin condensation
Authors: Lopez‐Larraza Daniel M. , Bianchi Nestor O.
Published: February 2007

BLM induces DNA degradation in living cells. We used CHO cells with maximal chromatin compactness (cells synchronized in metaphase), cells with chromatin decondensed by Na butyrate treatments, and control cells with normal chromatin condensation in order to analyze the correlation between chromatin compactness, DNA sensitivity to BLM, efficiency of repair of BLM‐induced DNA lesions, and cell viability. We found that the DNA sensitivity to BLM and the efficiency of DNA repair is inversely correlated with the degree of chromatin coiling. Cells with decondensed chromatin are those showing higher DNA sensitivity to BLM but also those having the best efficiency to mend the damage. Accordingly, these cells show an amount of residual DNA lesions and a curve of growth similar to that of control cells. The situation is just the opposite for metaphase cells. The DNA of these cells is more resistant to BLM, but the damage is poorly repaired. The final result is that BLM induces a higher concentration of residual DNA lesions and a lower viability in metaphase than in control cells. Our results suggest that chromatin structure influences the quantity and repairability of the BLM‐induced lesions, producing a higher incidence of double strand break in the DNA of cells with marked chromatin condensation. © 1993 Wiley‐Liss, Inc.
Studies for a genotoxic potential of some endogenous and exogenous sex steroids. I. Communication: Examination for the induction of gene mutations using the ames salmonella/microsome test and the HGPRT test in V79 cells
Authors: Lang Rainer , Reimann Roland
Published: February 2007

The mutagenicity results and data of nine progestins (cyproterone acetate, dehydrospirorenone, gestodene, gestonorone caproate, levonorgestrel, norethisterone, norethisterone acetate, norethisterone enanthate, norethynodrel), one hypothetical metabolite (6,7‐epoxycyproterone acetate), four estrogens (estradiol, ethinylestradiol, cyclotriol, cyclotriol), and four other sex steroids (atamestane, lilopristone, onapristone, propylmesterolone) are reported. All 17 sex steroids were investigated using the Ames salmonella/microsome direct plate incorporation protocol, and seven were additionally tested using the preincubation modification. Seven sex steroids were also studied in the HG‐PRT test with V79 cells for the induction of gene mutations in mammalian cells. The metabolite was examined in the Ames salmonella/microsome assay using the standard protocol and the preincubation modification. In all assays the test compounds were investigated up to concentration levels where cytotoxicity and/or visible precipitation occurred or at least the solubility limit of the test compound was reached. For all assays, evaluation of the data indicates that neither any of the sex steroids nor the hypothetical metabolite was able to induce gene mutations whether in the absence or the presence of an extrinsic metabolizing system (S9 mix). © 1993 Wiley‐Liss, Inc.
Mutagenic activity of the 4,5‐ and 9,10‐dihydrodiols of benzo[J]fluoranthene and their syn‐ and anti‐dihydrodiol epoxides in salmonella typhimurium
Authors: Marshall Milton V. , He Zhen‐Min , Weyand Eric H. , Rice Joseph E. , Lavoie Edmond J.
Published: February 2007

The objective of this study was to determine the relative mutagenic activities of the major dihydrodiol metabolites of benzo[j]fluoranthene (B[j]F) and their corresponding syn‐ and anti‐dihydrodiol epoxides. Salmonella typhimurium tester strains TA97a, TA98, and TA100 were used to evaluate the mutagenic potencies of the parent hydrocarbon and these suspect proximate and ultimate mutagenic metabolites. B[j]F and the trans‐dihydrodiol metabolites were active only in the presence of an external metabolic activation system (S9) with the exception of the B[j]F‐4,5‐diol, which was weakly active in TA98 and TA100 in the absence of S9. The B[j]F‐4,5‐diol was more mutagenic than the B[j]F‐9,10‐diol in tester strains TA98 and TA100, whereas the opposite effect was observed in TA97a. In the absence of S9, the anti‐B[j]F‐4,5‐diol epoxide was more mutagenic than the syn‐B[j]F‐4,5‐diol epoxide and the syn‐ and anti‐B[j]F‐9,10‐diol epoxides in tester strains TA97a and TA100. The exceptional mutagenic potency of the anti‐B[j]F‐4,5‐diol epoxide in TA100 resembles that observed by epoxides located within a fjord, or by the anti‐diol epoxides of bay region methylated polycyclic aromatic hydrocarbons. In contrast, the mutagenicity of the pseudo bay region dihydrodiol epoxides arising from the B[j]F‐9,10‐diol more closely resembles that observed with the classical bay region dihydrodiol epoxides of chrysene. In summary, both dihydrodiol metabolites of B[j]F are mutagenic in S. typhimurium, and the relative potency varies among the tester strains. The highest mutagenic response was achieved in tester strain TA100, which detects base‐pair substitutions. The most potent direct‐acting dihydrodiol epoxide in this tester strain was the anti‐B[j]F‐4,5‐diol epoxide, which agrees with the results of mouse skin painting studies that indicate that the B[j]F‐4,5‐diol is more tumorigenic that the parent hydrocarbon or the B[j]F‐9,10‐diol. A cova‐lent DNA adduct formed between the anti‐B[j]F‐4,5‐diol epoxide and deoxyguanosine was the major species of DNA adduct formed in S. typhimurium. This adduct corresponds to the major DNA adduct formed in mouse skin following application B[j]F.
Micronucleus test and erythropoiesis: Effect of cobalt on the induction of micronuclei by mutagens
Authors: Suzuki Yuji , Shimizu Hidesuke , Nagae Yusuke , Fukumoto Masakatsu , Okonogi Hideo , Kadokura Makoto
Published: February 2007

The micronucleus test is used widely as an in vivo short‐term assay for potential carcinogens. In the present study, results of the micronucleus test were affected by cobalt dichloride pretreatment. Cobalt dichloride was used to induce erythropoietin, a growth factor for erythropoiesis. The increase in mutagen‐induced micronucleus response following cobalt pretreatment, therefore, may have been due to a change in the rate of erythropoiesis. The greatest interaction between cobalt pretreatment and mutagen treatment for the induction of micronucleated polychromatic erythrocytes (MPCE) occurred when mice were injected with 1,1‐dimethylhydrazine (DMH) 12–24 hr after pretreatment with cobalt dichloride and killed 30 hr later. Increased sensitivity of the micronucleus test was attributable to the administration of mutagen during the differentiation and multiplication of erythroblast, which is presumed to have been accelerated by pretreatment with cobalt dichloride. An increased induction of MPCE in the bone marrow by two chemicals—benzo(a)pyrene, 2‐naphthylamine—was also observed following pretreatment with cobalt dichloride. © 1993 Wiley‐Liss, Inc.
Comparative studies on cytotoxic and genotoxic effects of two organic mercury compounds in lymphocytes and gastric mucosa cells of sprague‐dawley rats
Authors: Betti C. , Barale R. , Pool‐Zobel B. L.
Published: February 2007

Human lymphocytes (HL) as well as lymphocytes (RL), hepatocytes (RH), and gastric mucosa cells (GM) of Sprague‐Dawley rats were treated in vitro for 1 h with methylmercury chloride (MMC, 0.5–4 μg/ml) and dimethylmercury (DMM, 5–40 μg/ml). The cytotoxicity of the two organic mercury compounds was assessed by dye exclusion, and the extent of induced DNA fragmentation was measured with a single‐cell microgel electrophoresis assay. Both MMC and DMM induced DNA damage and cytotoxicity in a dose‐related manner in HL, RL, and GM. MMC was more effective in causing a significant increase in median DNA migration than DMM at doses yielding approximately the same degree of cytotoxicity. In rat hepatocytes the MMC‐induced DNA damage was, however, lower than in the other cells. An analysis of repair kinetics following exposure to 2 μg/ml MMC was carried out in human lymphocytes obtained from an adult male donor. The bulk of DNA repair occurred 90 min after in vitro exposure, and it was about complete by 120 min following cessation of exposure. Finally, in order to have a basis for extrapolating to the human situation, in vivo studies were performed with Sprague‐Dawley rats, also assessing the DNA damage and cytotoxicity in the lymphocytes and gastric mucosa cells. These in vivo results after oral exposure may be directly compared to the in vitro data obtained in the same cells. © 1993 Wiley‐Liss, Inc.
Update on target theory as applied to chromosomal aberrations
Authors: Savage John R. K.
Published: February 2007

The early radiobiologists, who developed target theory to explain their results, considered the chromosome “target” as a visible thread that could be physically broken by ionizing radiation. Most of the broken ends restituted, but those that did not were free to wander about and, within limits, could rejoin with any other broken end they happened to contact to form structural aberrations. Failing this, they could remain to be seen as “open” breaks at the subsequent metaphase.

These ideas, and their inevitable consequences, still form the basis for much modern thinking, even though we now know that the structure of the chromosome, and of the interphase nucleus, are very much more complicated than the originators of the theory envisaged. Current understanding of chromosomes of the molecular level and the varied responses a cell can mobilize when damage is introduced, raise again the question, Can we still think in terms of simple targets?

Some of the experimental observations and suggestions made since those early days are reviewed, and the application of target theory to the three theories of aberration origins (Classic, Exchange, Recombination) is briefly discussed. © 1993 Wiley‐Liss, Inc.
Mechanism of hyperoxia‐induced chromosomal breakage in chinese hamster cells
Authors: Gille Johan J. P. , Van Berkel Carola G. M. , Joenje Hans
Published: February 2007

Exposure of cell cultures to hyperoxia, i.e., an atmosphere containing more than 20% O2, results in various genotoxic effects. The most prominent effect of hyperoxia is its clastogenicity. In this paper, earlier published data, obtained from research devoted to the mechanism of hyperoxia‐induced clastogenesis, are reviewed. In addition, new data are presented concerning the hyperoxia‐sensitivity of the DNA‐repair deficient Chinese hamster cell lines xrs1, irs1, and EM9. None of these ionizing radiation‐sensitive mutants showed hypersensitivity to hyperoxia, as measured by chromosomal aberration induction and loss of clonogenic cell survival. From the normal hyperoxia‐sensitivity of xrs1, it may be concluded that DNA double strand breaks, of the type that are induced by ionizing radiation, do not play a role in chromosomal aberration formation by hyperoxia. In addition, since xrs1 is hypersensitive to drugs that inhibit topoisomerase II, it seems rather unlikely that exposure to hyperoxia affects topoisomerase II activity. Based on circumstantial evidence we hypothesize that perturbation of poly(ADP‐ribose) metabolism may play a critical role in the mechanism of hyperoxia‐induced clastogenesis. © 1993 Wiley‐Liss, Inc.
Mutagenicity of methyl methanesulfonate (MMS) in vivo at the Dlb‐1 native locus and a lacl transgene
Authors: Tao K. S. , Urlando Cesare , Heddle John A.
Published: February 2007

Methyl methanesulfonate (MMS) is an extraordinarily poor mutagen compared to ethylnitrosourea (ENU) or even X‐rays. In lung fibroblasts in vivo, MMS has been shown to induce many micronuclei but few, if any, mutations at the hpt locus. We wondered if the lack of mutations might be due to the lack of division and DNA synthesis in fibroblasts in vivo, which would permit substantial time for differential repair of DNA lesions. This idea was tested in the small intestine, a tissue in which the cells are actively dividing. Two loci were examined: a native locus (Dlb‐1) which determines the presence or absence of a lectin binding site on the surface of the epithelial cells, and a lacl transgene which controls β‐galactosidase synthesis. Lacl mutations were detected after in vitro packaging of DNA isolated from the intestinal epithelium into lambda phage and expression in suitable bacteria.

Although the epithelial cells are proliferating, acute treatments produced no significant increase in mutations at either locus. Subacute treatments produced low but significant increases in mutation frequency at both loci. The results confirm that MMS is a far more potent clastogen than it is a mutagen and should be regarded as a super‐clastogen in the same manner as ENU is a super‐mutagen. The carcinogenicity of MMS is probably the result of its potent clastogenicity rather than its weak activity as a point mutagen.
Transcription by T7 RNA polymerase of DNA containing abasic sites
Authors: Sanchez Giselle , Mamet‐Bratley Margaret D.
Published: February 2007

The effects of abasic (AP) sites on RNA synthesis were studied in vitro, using T7 RNA polymerase and a plasmid template containing a T7 promoter. The presence of increasing numbers of AP sites caused a progressive decline in RNA synthesis. The average RNA chain length, calculated from the ratio of initiation to chain elongation, decreased with increasing numbers of AP sites, revealing that complete blocks must occur during synthesis. The probability that RNA polymerase would be blocked at an AP site in the DNA template strand was estimated to be 0.3 in our experimental conditions. These results demonstrate that RNA synthesis by T7 RNA polymerase is inhibited by AP sites and that readthrough of the lesion occurs more frequently than premature chain termination. Chemical reduction of AP sites in the template did not change the block/bypass pattern. © 1994 Wiley‐Liss, Inc.
Mutant alleles of tRNAThr genes suppress the hisG46 missense mutation in Salmonella typhimurium
Authors: Kupchella Eugene , Koch Walter H. , Cebula Thomas A.
Published: February 2007

Extragenic suppressors of the hisG46 missense mutation were mapped to the 71 and 88 min regions of the Salmonella typhimurium chromosome, positions that in Escherichia coli contain the thrV (tRNAThr1) and thrT (tRNAThr3) genes, respectively. The suppressor loci were identified as mutant alleles of thrV and thrT, using allelespecific colony hybridization. An oligomer, based on the conserved 5′ sequence of the thrT and thrV genes in E. coli and designed to contain the putative mutant anticodon, discriminated between suppressor‐containing and wild‐type strains. Similarly, probes specific for the thrV‐[SuGGG] and thrT[SuGGG] were used to differentiate the two suppressors. To date, all extragenic suppressors of hisG46 have been identified as either thrV[SuGGG] or thrT[SuGGG]. A near equal distribution of thrV[SuGGG] and thrT[SuGGG] suppressors was found among 29 spontaneous and 43 mutagen‐induced hisG46 extragenic suppressor revertants. It was concluded, therefore, that mutant alleles of thrV and thrT are predominantly, if not solely, responsible for intergenic suppression of the hisG46 mutation. © 1994 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Multiplex PCR analysis of in vivo‐arising deletion mutations in the hprt gene of human T‐lymphocytes
Authors: Fuscoe James C. , Zimmerman Lisa J. , Harrington‐Brock Karen , Moore Martha M.
Published: February 2007

A multiplex polymerase chain reaction (PCR) procedure was adapted for the rapid and efficient evaluation of deletions of the hypoxanthine guanine phosphoribosyltransferase (hprt) gene in human T‐lymphocytes. The hprt clonal assay was used to isolate in vivo‐arising hprt‐deficient T‐cells from six healthy males. Mutant frequencies ranged from 9‐27 × 10−6. Simple crude cellular extracts from 223 mutants were analyzed for hprt gene deletion. Sixteen (7.2%) were found to be due to total gene deletion and 22 (9.9%) were due to partial gene deletion. The relatively high frequency of total gene deletions was caused by replicate isolates of a single mutational event as shown by single‐strand conformation polymorphism (SSCP) analysis of rearranged T‐cell receptor (TCR)‐γ genes. Eighteen of the 22 partial hprt gene deletion mutants were determined to be of independent origin based on a unique hprt mutation or SSCP‐TCR‐γ pattern. One‐half (9/18) of the partial deletion mutants involved all or part of exon 4 alone, suggesting that this region of the hprt gene is prone to deletion. The small deletions effecting exon 1 (1 mutant), exon 2 (2 mutants), and exon 4 (6 mutants) would not have been detected by conventional Southern blot analysis and may represent a new, previously unrecognized class of mutations. The ready isolation of such intragenic deletions will allow the characterization of breakpoint junctions and may provide insights into the important processes of DNA breakage and rejoining. © 1994 Wiley‐Liss, Inc.
Lack of chloroform‐induced DNA repair in vitro and in vivo in hepatocytes of female B6C3F1 mice
Authors: Larson Jeffrey L. , Sprankle Catherine S. , Butterworth Byron E.
Published: February 2007

Chloroform has been shown to induce hepatocellular carcinomas in female B6C3F1 mice when administered by gavage, but not when given in drinking water. When administered in corn oil at the carcinogenic doses of 238 and 477 mg/kg, chloroform induced necrosis and sustained regenerative cell proliferation in the liver. To investigate the mode of action of tumor induction in the target cells, the ability of chloroform to induce unscheduled DNA synthesis (UDS) was examined in the in vitro and in vivo hepatocyte DNA repair assays. In the in vitro assay, primary hepatocyte cultures from female B6C3F1 mice were incubated with concentrations from 0.01 to 10 mM chloroform in the presence of 3H‐thymidine. UDS was assessed by quantitative autoradiography. No induction of DNA repair was observed at any concentration. In the in vivo assay, animals were treated by gavage with 238 and 477 mg/kg chloroform in corn oil. Primary hepatocyte cultures were prepared 2 and 12 hr later, incubated with 3H‐thymidine, and assessed for induction of UDS as above. No DNA repair activity was seen at either dose or at either timepoint. These negative results in the target organ are consistent with the concept that neither chloroform nor its metabolites are directly DNA reactive and that the carcinogenicity of chloroform is secondary to induced cytolethality and regenerative cell proliferation. © 1994 Wiley‐Liss, Inc.
Relationship between benzo(a)pyrene‐DNA adducts and somatic mutation and recombination in drosophila melanogaster
Authors: Zordan M. , Osti M. , Pavanello S. , Costa R. , Levis A. G.
Published: February 2007

The evaluation of the relationship between the dose to DNA of a mutagen/carcinogen and in vivo somatic cell mutagenesis may provide information on the mechanisms leading to induced mutational events. This can be achieved, for example, by coupling test systems that permit the detection of somatic mutation and recombination on the basis of phenotypic changes in cuticular structures of Drosophila melanogaster, with methods for the quantitation of carcinogen‐DNA adducts such as the 32P‐postlabeling technique. In this article, we evaluate the quantitative relationship between BaP‐DNA adduct formation, determined by 32P‐postlabeling, and the induction of mutant cells in the wing marker version of the somatic mutation and recombination test (SMART) in Drosophila melanogaster. The total single clones in the trans‐heterozygous mwh/flr3 flies show a linear relationship with the BaP‐DNA adduct levels, suggesting a single hit mechanism for the genetic damage giving rise to this type of clones. In contrast, the twin clones (which are of recombinational origin) display a linear‐quadratic relationship with the adduct levels, suggesting that multiple hits may be involved in generating these clones. The total single clones in the mwh/TM3, Ser flies (in which mitotic recombination is suppressed) show a logarithmic relationship with the adduct levels. The discussion of these data in terms of the pathways that may be involved in the repair of the BaP‐DNA adducts leads to the suggestion that in Drosophila melanogaster the repair of Bap metabolite‐DNA adducts in somatic cells may proceed, in large part, via post‐replicative recombinational repair. © 1994 Wiley‐Liss, Inc.
Cytogenetic effects of phosphine inhalation by rodents. I: Acute 6‐hour exposure of mice
Authors: Kligerman A. D. , Bryant M. F. , Doerr C. L. , Erexson G. L. , Kwanyuen P. , McGee J. K.
Published: February 2007

Phosphine (PH3) is a highly toxic grain fumigant that can be produced from the reaction of metal phosphides with water. To determine the in vivo cytogenetic effects of inhalation of PH3, male CD‐1 mice were exposed to either 0, 5, 10, or 15 ppm target concentrations of PH3 for 6 hr. Twenty hours after the termination of exposure, the spleens of the mice were removed, macerated, and the splenocytes cultured for analyses of sister chromatid exchanges, chromosome aberrations, and micronuclei in cytochalasin B‐in‐duced binucleated cells. In addition, bone marrow smears were made for the analysis of micronuclei in polychromatic erythrocytes. No increase in any of the cytogenetic endpoints was found at any of the concentrations examined. The only statistically significant response was a concentration‐related slowing of the cell cycle in the splenocytes. © 1994 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Chemical mutagenesis testing in Drosophila. X. Results of 70 coded chemicals tested for the national toxicology‐program
Authors: Foureman P. , Mason J. M. , Valencia R. , Zimmering S.
Published: February 2007

Seventy chemicals were tested for the ability to induce sex‐linked recessive lethal (SLRL) mutations in postmeiotic and meiotic germ cells of male Drosophila melanogaster. As in the previous studies in this series, adult feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. Two chemicals, n‐butane and propylene, were gaseous and therefore tested only by inhalation. One chemical (dimethylcar‐bamoyl chloride) was tested only by injection. Those chemicals that were mutagenic in the SLRL assay were further tested for the ability to induce reciprocal translocations.

Sixteen of the 70 chemicals tested were mutagenic in the SLRL assay: 3‐chloro‐2‐methylpropene, 3‐(chloromethyl)pyridine HCI, dimethyl‐carbamoyl chloride, HC blue 1,3‐iodo‐1,2‐propanediol, malaoxon, N,N′‐methylene‐bisacrylamide, 4,4′‐methylenedianiline 2HCI, ziram, cis‐dichlorodiaminoplatinum II, 1,2‐dibromo‐ethane, dibromomannitol, 1,2‐epoxypropane, glycidol, myleran, and toluene diisocyanate. The last seven also induced reciprocal translocations. A comparison of the results from the SLRL assay with other assays for mutagens and carcinogens suggests that the SLRL assay is highly specific, but poorly sensitive, both for mutagens and potential carcinogens. © 1994 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Genetic toxicology testing of Di(2‐ethylhexyl) terephthalate
Authors: Barber Eugene D.
Published: February 2007

Di(2‐ethylhexyl) terephthalate (DEHT) is a commercially produced chemical (Kodaflex® DOTP) that is used as a general purpose, low‐volatility plasticizer for polyvinyl chloride and other polymeric materials. Less than 30 million kilograms of DEHT are produced annually. DEHT is isomeric with di(2‐ethylhexyl) phthalate (DEHP), a nongenotoxic rodent carcinogen whose mode of action has been suggested to derive from its ability to produce hepatocellular proliferation and/or hepatic peroxisome proliferation. Thus it is important to know the behavior of DEHT in genotoxicity assays in order to compare it with that of DEHP and other phthalate ester plasticizers. It is known from previously published studies that rats fed DEHT in the diet at 2,000 mg/kg produce urine that is negative in the Ames Salmonella bacterial mutagenicity assay in the presence and absence of induced rat liver S‐9 and in the presence and obsence of β‐glucuronidase/aryl sulfatase. Reported here are the results of direct testing of DEHT in the Ames plate incorporation assay, the Chinese hamster ovary/hypoxanthine guanine phosphoribosyl transferase (CHO/HGPRT) in vitro mammalian cell mutagenicity assay, and an in vitro chromosome aberrations assay using CHO cells. The results for mono(ethylhexyl) terephthalate (MEHT), a metabolite of DEHT, in the Ames Salmonella bacterial mutagenicity assay are also presented. All test results for both DEHT and MEHT were found to be negative, and it is therefore concluded that DEHT, like its isomeric relative DEHP, is not genotoxic. © 1994 Wiley‐Liss, Inc.
Propylene oxide mutagenesis at template cytosine residues
Authors: Snow Elizabeth T. , Singh Jatinder , Koenig Karen L. , Solomon Jerome J.
Published: February 2007

Propylene oxide (PO) is a widely used industrial reagent which is mutagenic and carcinogenic. We have recently shown that a variety of aliphatic epoxides, including propylene oxide, can react with DNA to form hydroxyalkyl adducts at N‐3 of cytosine which rapidly undergo hydrolytic deamination to produce uracil adducts. These 3‐hydroxyalkyl uracil adducts are stable in DNA and are postulated to be an important class of potentially mutagenic lesions. Mutagenesis at cytosine residues due to PO modification of single‐stranded M13mp2/C141 DNA was studied by transfection of modified DNA into SOS and non‐SOS induced E. coli host cells. Mutations of the proline (CCC) codon at C141 which result in reversion of the lacZ phenotype (blue plaques) were scored. It was found that PO treatment of single‐stranded DNA results in dose‐dependent mutagenesis that is highly SOS dependent. The spectrum of base‐substitution mutations found at this site differed when PO‐modified DNA was transfected into E. coli with different DNA repair backgrounds. These results indicate that propylene oxide induced DNA adducts at template cytosine residues are mutagenic in E. coli and that this mutagenesis is greatly increased by SOS processing. They also show that these lesions may be repaired by one or more mechanisms.
Activity of aromatic amines in the eye: w/w+ somatic assay of drosophila melanogaster
Authors: Rodriguez‐Arnaiz Rosario , Aranda Judith Hernández
Published: February 2007

Aromatic amines represent a category of classical environmental hazards which require biotransformation in order to exert their mutagenic and carcinogenic effects. The mutagenic activity of several aromatic amines was tested by means of the w/w+ somatic assay of Drosophila melanogaster employing a wild‐type strain Leiden Standard (LS) and an insecticide‐resistant stock Hikone‐R (HK‐R). Four monocyclicortho‐anisidine (O‐AN), ortho‐toluidine (O‐TO), 2, 4‐diaminoanisole (2, 4‐DAA) and 4‐nitro‐o‐phenylenediamine (4‐N‐o‐PDA), and one bicyclic‐ 4, 4′‐oxidianiline (4, 4′‐ODA) aromatic amines were tested by chronic exposure. Two separate experiments were run, and concurrent controls were treated with the solvent mixture. Results show that the ortho‐anilines (O‐AN and O‐TO) were active in the assay, while the diamines containing a methoxy (2, 4‐DAA) or a nitro group (4‐N‐o‐PDA) were inactive. The bicyclic aromatic amine, 4, 4′‐ODA, was the most potent. The genotoxic responsiveness of both strains was very similar. © 1994 Wiley‐Liss, Inc.
Determination of genotoxic and other effects in mice following short term repeated‐dose and subchronic inhalation exposure to phosphine
Authors: Barbosa A. , Rosinova E. , Dempsey J. , Bonin A. M.
Published: February 2007

Phosphine is an important fumigant in the grain industry and has been reported to be genotoxic in occupationally exposed fumigators. This study reports on the effects of phosphine inhalation exposure at up to, and exceeding, occupational relevant levels in a subchronic (0.3, 1.0 and 4.5 ppm, 13 weeks) and a short term repeated‐dose (5.5 ppm, 2 weeks) study in both sexes of Balb‐c mice. The following end‐points were examined: micronucleus induction in bone marrow, peripheral blood, spleen lymphocytes and skin keratinocytes, muat the hypox‐anthine‐guanine phosphoribosyl transferase locus in lymphocytes, and weight gain and relative organ weights (kidneys, lungs, liver, heart, brain and spleen). After subchronic exposure, there was a highly significant negative linear correlation between proportional weight gain and exposure in both sexes (multiple linear regression, r = −0.56, P < 0.0001), with female mice showing a greater effect. Females also showed an increase in relative organ weights at the highest test dose, in contrast to males where there was a slight decrease. A statistically significant increase in micronucleus frequency was seen in the bone marrow and spleen lymphocytes of both sexes, but only at the highest concentration. The short term repeated‐dose study revealed a slight decrease in weight gain in both sexes, with a greater effect in females.

It is concluded that phosphine is weakly genotoxic in both sexes of mice, and has an effect on weight gain. However, the weak genotoxic effect may not be biologically significant as it was seen only in the subchronic study and only at the highest test concentration of 4.5 ± 0.8 ppm (approaching the LD50). Although such exposure conditions are unlikely to be encountered in an occupational environment, caution should continue to be exercised in the use of phosphine until more data become available. © 1994 Wiley‐Liss, Inc.
Centromere analysis of micronuclei induced by 2‐aminoanthraquinone in cultured mouse splenocytes using both a gamma‐satellite DNA probe and anti‐kinetochore antibody
Authors: Afshari Arash J. , McGregor Pamela W. , Allen James W. , Fuscoe James C.
Published: February 2007

We have tested 2‐aminoanthraquinone (2‐AAQ) as a potential aneugen in a cytokinesis‐blocked mouse splenocyte micronucleus (MN) assay. Bi‐nucleated cells (BNC) were evaluated for MN, and the MN were further probed with two indicators of centromere presence: an anti‐kineto‐chore autoantibody and a DNA probe for the mouse gamma‐satellite locus. A dose‐dependent increase in the frequency of BNC with MN was observed. At the highest 2‐AAQ concentration (10 μg/ml), the frequency of BNC containing MN was increased greater than 10‐fold over background. Both centromere‐positive and centromere‐negative MN were significantly increased. At least 62% of MN at all 2‐AAQ doses were positive for the gamma‐satellite DNA probe, while 30–53% were labeled with the anti‐kinetochore antibody. In contrast with the 2‐AAQ results, after treatment with the aneugen demecolcine (positive control), greater than 80% of MN labelled positive with both probes. This discordance in the results with the two probes after 2‐AAQ exposure suggests that the mode of action of this chemical may be as an aneugen by disruption of the kinetochore proteins, as a clastogen with a preferential cleavage site at or near the gamma‐satellite locus, or both. Our results also suggest that the use of either of these probes individually may not be an adequate measure of centromere presence. Nevertheless, positive results for both markers provides strong evidence that 2‐AAQ is aneugenic. © 1994 Wiley‐Liss, Inc.
Mutagenicity of trans, trans‐muconaldehyde and its metabolites in V79 cells
Authors: Chang R. L. , Wong C. Q. , Kline S. A. , Conney A. H. , Goldstein B. D. , Witz G.
Published: February 2007

Trans, trans‐Muconaldehyde (MUC), a six‐car‐bon‐diene‐dialdehyde, is a microsomal, hema‐totoxic ring‐opened metabolite of benzene. MUC is metabolized to a variety of compounds which are formed by oxidation and/or reduction of the aldehyde group(s). In the present studies, MUC and its metabolites were examined for mutagenic activity at the hypoxanthine guanine phosphoribosyltransferase (HGPRT) locus in Chinese hamster V79 cells. Mutagenicity was scored by counting 8‐azaguanine‐resistant colonies. Of the 6 compounds tested, MUC and its aldehydic metabolites 6‐hydroxy‐trans, trans 2, 4‐hexadienal and 6‐oxo‐trans, trans‐hexadi‐enoic acid were mutagenic in that order of potency. The other MUC metabolites tested (1, 6‐dihydroxy‐trans, trans‐2, 4‐hexadiene, trans, trans‐muconic acid, and 6‐hydroxy‐trans, trans‐2, 4‐hexadienoic acid) had little or no activity in this system. The order of mutagenic activity of MUC and its aldehydic metabolites correlates with their reactivity towards glutathione, suggesting that alkylating potential is important in the genotoxicity of these compounds. © 1994 Wiley‐Liss, Inc.
Rapid DNA degradation in primary rat hepatocytes treated with diverse cytotoxic chemicals: Analysis by pulsed field gel electrophoresis and implications for alkaline elution assays
Authors: Elia Michael C. , Storer Richard D. , McKelvey Troy W. , Kraynak Andrew R. , Barnum John E. , Harmon Lori S. , Deluca John G. , Nichols Warren W.
Published: February 2007

The use of genetic toxicology tests for hazard identification is complicated by the fact that some in vitro tests using cultured mammalian cells are subject to potential artifacts that can make it difficult to distinguish between direct, chemically‐induced genotoxicity, and DNA damage that occurs secondary to chemically‐induced cytotoxicity (e.g., mediated by endogenous nucleases). Recently, we demonstrated that cytotoxicity‐induced DNA double strand breaks (dsb) can produce artifacts in the in vitro alkaline elution/rat hepatocyte assay [Elia et al., 1993]. To explore this further, we used pulsed field gel/DNA dsb assays to characterize the relationship between chemically‐induced cytotoxicity and the degradation of genomic DNA to high molecular weight fragments. Two sets of compounds were tested: 17 cytotoxic agents judged to be neither genotoxic nor carcinogenic, and 10 known genotoxic carcinogens. We found a close correlation between chemically‐induced cytotoxicity and the rapid degradation of DNA to high molecular weight, double‐stranded fragments. In contrast, the classic genotoxic chemicals tested generally did not trigger DNA dsb fragmentation at doses that were genotoxic but not immediately cytotoxic. These data indicate that pulsed field gel/DNA dsb assays can be used with in vitro genetic toxicology assays to help distinguish between genotoxic and cytotoxic mechanisms of DNA damage. © 1994 Wiley‐Liss, Inc.
Etoposide (VP‐16) is a potent inducer of micronuclei in male rat meiosis: Spermatid micronucleus test and DNA flow cytometry after etoposide treatment
Authors: Lähdetie J. , Keiski A. , Suutari A. , Toppari J.
Published: February 2007

The genotoxic and cytotoxic effects of etoposide (VP‐16), a topoisomerase II inhibitor, on male rat spermatogenic cells were studied by analysing induction of micronuclei during meiosis. Micronuclei (MN) were scored in early spermatids offer different time intervals corresponding to exposure of different stages of meiotic prophase. Etoposide had a strong effect on diplotene‐diakinesis I cells harvested 1 day after exposure, and a significant effect also on late pachytene cells harvested 3 days after exposure. The effect at 18 days corresponding to exposure of preleptotene stage of meiosis (S‐phase) was weaker but also statistically significant. Adriamycin was used as a positive control in this study. The results indicate a different mechanism of action of etoposide compared with adriamycin and other chemicals studied previously with the spermatid micronucleus test.

DMA flow cytometry was carried out to assess cytotoxic damage at the same time intervals (1, 3, and 18 days after treatment) at stages I and VII of the seminiferous epithelial cycle allowing a study of cytotoxicity to different spermatogenic cell stages. Damage of differentiating sper‐matogonia was observed by a decrease in the cell numbers of the 2C peak 1 and 3 days after treatment and by a reduction of the number of 4C cells (primary spermatocytes) 18 d after etoposide treatment. Adriamycin also killed differentiating spermatogonia. Since the cell population which showed a high induction of MN by etoposide was not reduced in number, the genotoxic effect is remarkable. We conclude that etoposide is a potent inducer of genotoxicity and patients treated with this agent during cancer chemotherapy are at a risk of genetic damage. © 1994 Wiley‐Liss, Inc.
QSAR models for both mutagenic potency and activity: Application to nitroarenes and aromatic amines
Authors: Benigni R. , Andreoli C. , Giuliani A.
Published: February 2007

We studied the molecular determinants that discriminate between mutagenic and inactive compounds for: a) aromatic and heteroaromatic amines; b) nitroarenes. Mutagenic activity (data from literature) had been previously assessed in Salmonella typhimurium and Escherichia coli (SOS repair). The Quantitative Structure‐Activity Relationships (QSAR) found were compared with those obtained in the laboratory of Professor C. Hansch for the mutagenic potency of the same compounds. It appears that there is a dramatic difference between the QSARs for potency, and those for yes/no activity: hydrophobicity played a major role in determining the potency of the active compounds, whereas mainly electronic factors differentiated the actives from the inactives. The electronic factors were those expected on the basis of the hypothesized metabolic pathways of the chemicals. Our interpretation is that the electronic factors (together with size/shape, possibly) determine the minimum requirement for the chemicals to be metabolized, whereas the hydrophobicity determines the extent of activity of chemicals that can be metabolized (actives). Moreover, the different QSARs found for the Salmonella strains TA98 and TA100 were discussed in the light of recent progress in the understanding of the molecular mechanisms of mutagenicity in these organisms. It is concluded that the nonlinear relationship observed for these chemicals between the two types of QSAR should be taken into account both when planning QSAR studies, and when using mutagenicity data for risk assessment. © 1994 Wiley‐Liss, Inc.
Metabolic activation of carcinogenic aromatic amines by fish exposed to environmental pollutants
Authors: Rodríguez‐Ariza A. , Diaz‐Méndez F. M. , Navas J. I. , Pueyo C. , López‐Barea J.
Published: February 2007

Activation of arylamines to mutagenic metabolites by hepatic S9 fractions has been evaluated as a biomaker of fish exposure to pollutants, using gilthead seabream (Sparus aurata), a valuable fish species from the Spanish South Atlantic littoral, as model organism. To obtain maximal sensitivity to the mutagenic action of aromatic amines, a strain of Salmonella typhimurium overproducing O‐acetyltransferase was used. Fish were treated with Aroclor 1254, pesticides (malathion and dieldrin), or cop‐per(ll), and compared to Aroclor 1254–treated rats. The promutagen activation capabilities of the S9 fractions were further characterized by studying the effect of two monooxygenase inhibitors, α‐naphthoflavone, a well known inhibitor of aromatic hydrocarbon‐inducible forms of cytochrome P450, and methimazole, a substrate for the flavin monooxygenase (FMO) system. This study shows that 2–aminoanthracene (2–AA) and 2–acetylaminofluorene (AAF) activation by gilthead liver is enhanced by treatment of fish with different xenobiotics. The catalyst responsible for this enhanced activation appears to be different for each promutagen and, at least for 2–AA, dependent on the type of xenobiotic. The data presented indicate further that treatment of gilthead with some compounds, such as malathion and dieldrin, enhances the activation of aromatic amines in liver, without inducing ethoxyresorufin‐O‐deethylase activity. The use of acetyltransferase‐overproducing bacteria appears to be a useful tool in the study of aryl‐amine activation by fish liver, where biotransformation capability is lower than in mammals. © 1995 Wiley‐Liss, Inc.