bluuebunny/crossref_metadata_2025 huggingface dataset:
Conversion of excision‐repairable DNA lesions to micronuclei within one cell cycle in human lymphocytes
Authors: Fenech M. , Neville S.
Published: February 2007

The human lymphocyte micronucleus (MN) assay is relatively insensitive to genotoxic agents that predominantly induce excision‐repairable lesions such as adducts and abasic sites. In this study we have explored the possibility of using cytosine arabinoside (ARA) to convert excision‐repairable DNA lesions to micronuclei (MN) within one cell cycle. The system consisted of human lymphocytes as target cells, the cytokinesis‐block (CB) method for identifying cells that had completed one nuclear division only, and X‐rays, methylnitrosourea (MNU), and ultraviolet light (UV) as mutagens. With each mutagen we have observed significant increments in induced MN in the cultures that had also been treated with ARA during G1. The slope of the dose‐response curves for induction of MN was increased by a factor of approximately 1.8 for X‐rays and 10.3 for UV and significant MNU induction of MN was only achieved in the cultures treated with ARA. Furthermore, a 24‐hr gap between mutagen exposure and the start of the assay did not abolish the increased sensitivity in the cultures treated with ARA. These observations suggested that the combined ARA and cytokinesis‐block micronucleus (CBMN) method may enhance the detection of exposure to genotoxic agents that predominantly induce excision‐repairable lesions.
Quantitative structure‐activity relationship investigation of the role of hydrophobicity in regulating mutagenicity in the Ames test: 2. Mutagenicity of aromatic and heteroaromatic nitro compounds in Salmonella typhimurium TA100
Authors: Debnath Asim Kumar , Lopez Compadre Rosa L. , Shusterman Alan J. , Hansch Corwin
Published: February 2007

A quantitative structure‐activity relationship (QSAR) has been derived for the mutagenic activity of 117 aromatic and heteroaromatic nitro compounds acting on Salmonella typhimurium TA100. Relative mutagenic activity is bilinearly dependent on hydrophobicity, with an optimal log P of 5.44, and is linearly dependent on the energy of the lowest unoccupied molecular orbital of the nitro compound. The dependence of mutagenic activity on hydrophobicity and electronic effects is very similar for TA98 and TA100. Mutagenic activity in TA100 does not depend on the size of the aromatic ring system, as its does in TA98. The effect of the choice of assay organism, TA98 versus TA100, on nitroarene QSAR is seen to be similar to the effect previously found for aminoarenes. Lateral verification of QSARs is presented as a tool for establishing the significance of a new QSAR.
Metal, mutagenicity, and biochemical studies on bivalve molluscs from Spanish coasts
Authors: Rodriguez‐Ariza Antonio , Abril Nieves , Navas José I. , Dorado Gabriel , López‐Barea‐Ariza Juan , Pueyo Carmen
Published: February 2007

Three species of marine bivalve molluscs (Chamelea gallina, Ruditapes decussatus, and Crassostrea gigas) have been studied in order to evaluate the levels of pollution on the South Atlantic Spanish littoral. Several transition metals (Cu, As, Cd, Sn, Hg, Pb) were determined as a general index of total contamination. Animals from putative contaminated areas exhibited higher metal contents than those from cleaner waters. C. gigas showed 5–20‐fold higher total metal content than the other two species. The mutagenicity of ethanolic extracts was assayed by using both the His reversion and the Ara forward mutation tests. Mollusc tissues from the three species did not contain genotoxins active on TA98 (frameshift mutations) or TA100 (mainly G:C base‐pair substitutions), but did contain direct‐acting genotoxins of a polar nature and oxidative type. This was based on the following observations: 1) mammalian metabolic activation was not required for mutagenicity, 2) mutagens were eluted with the polar fraction from XAD‐2 columns, and 3) mutagenic responses were observed with Salmonella typhimurium TA102 (A:T base‐pair substitutions; sensitive to oxidative damages) and Escherichia coli catalase‐deficient (AraR forward mutations) strains. No relevant differences were found in the mutagenicity of mollusc extracts from areas with different pollution levels. Otherwise, our data suggest that, in general, animals living in contaminated environments had fewer genotoxins of oxidative type than those from less polluted areas. Such a result might be explained by the observation of increased levels of a number of detoxifying and antioxidant enzymes, such as glutathione‐S‐transferase, glutathione‐peroxidase, catalase, and superoxide dismutase. Thus, contaminated animals seem to be better protected against the oxidative damages induced by metals, in agreement with their lower malondialdehyde levels. To what extent the responsible mutagenic compounds are of endogenous origins, or “Nature's pesticides” (the major toxic chemicals ingested by phytoplankton filterfeeders), and/or the result of human activities remains to be determined.
Conditions for detecting the mutagenicity of divalent metals in Salmonella typhimurium
Authors: Pagano Dennis A. , Zeiger Errol
Published: February 2007

The mutagenesis of metals in bacteria, as reported in the literature, can best be described as inconsistent. We report that cobalt chloride (Co++), ferrous sulfate (Fe++), manganese sulfate (Mn++), cadmium chloride (Cd++), and zinc chloride (Zn++) could be reproducibly detected as mutagens in Salmonella strain TA97 when preincubation exposures were made in sterile, distilled, deionized water, or in Hepes buffer in NaCl2/KCl2, rather than the standard sodium phosphate buffer. Co++ was also mutagenic under standard preincubation conditions. The individual components of Vogel‐Bonner medium, i.e., potassium and ammonium phosphates, citrate, and magnesium sulfate, inhibit mutagenesis by these metals. The phosphates and the citrate probably inhibit by chelating the metals, while data are presented to suggest that Mg++ inhibition of metal mutagenesis is due to competitive inhibition for active transport via the magnesium active transport system in Salmonella. The chelator, diethyldithiocarbamate, inhibited the mutagenicity of Co++, Fe++, Zn++, and Mn++, but enhanced the mutagenicity of Cd++. The results presented show that divalent metals can be detected as mutagens in Salmonella, and that their lack of detection as mutagens is not due to an inherent insensitivity of Salmonella but to their interaction with media components and/or passive and active transport processes.
Phenobarbital: Does the positive result in TA1535 indicate genotoxic properties?
Authors: Albertini S. , Gocke E.
Published: February 2007

The liver carcinogen phenobarbital (PB) causes a weak but reproducible increase of the mutant frequency in the Ames test, strain TA1535, without S9. Since there is no obvious chemical basis for a “DNA reactivity” of this compound experiments were performed to obtain information about possible indirect mechanisms of enhancing the number of spontaneous mutant colonies. In the course of the study strong synergistic and comutagenic effects of PB when given in combination with Na‐azide or 2‐aminoanthracene (2AA) were observed. Not only TA1535 but the complete set of tester strains was responsive. However, PB did not enhance the effects of other mutagens such as 4‐nitroquinoline N‐oxide or 2‐nitrofluorene. It is argued that in strain TA1535 the fixation and expression of spontaneously occurring DNA lesions is amenable to modulation by PB similar to that of Na‐azide or 2AA induced lesions. Thus in the usual sense, PB is not genotoxic in the Ames test. Methapyrilene, another liver carcinogen with an assumed non‐genotoxic mode of action, showed almost identical properties in these experiments.
Evaluation of the mutagenic and genotoxic activities of 48 nitroimidazoles and related imidazole derivatives by the Ames test and the SOS Chromotest
Authors: De Méo M. , Vanelle P. , Bernadini E. , Laget M. , Maldonado J. , Jentzer O. , Crozet M. P. , Duménil G.
Published: February 2007

The mutagenic and genotoxic activities of 48 nitroimidazoles and related imidazole derivatives have been evaluated by using modified versions of the Ames test and the SOS Chromotest. Salmonella typhimurium tester strain TA 100 was used with and without metabolic activation in the Ames test and Escherichia coli tester Strain PQ 37 was used with and without metabolic activation in the SOS Chromotest. Including metronidazole and dimetridazole, 45 derivatives were mutagenic and genotoxic. The mutagenic potencies (MP) ranged from 0.127 to 53,717 revertants/nmol while the SOS induction powers (SOSIP) ranged from 0.00131 to 107 IF/nmol. The overall correlation between MP and SOSIP was r = 0.845 (n = 84) as calculated by linear regression analysis. A higher correlation was observed between MP and SOSIP without the S9 mix than with it. Among the imidazole derivatives, the 5‐nitroimidazoles with a lactam ring at the 2‐position showed the highest MP and SOSIP. The presence of a nitro group at the 5‐position was critical for the mutagenicity and the genotoxicity of the derivatives. Substituents at the 1‐ and 2‐positions were also found to modulate these activities.
Chemical mutagenesis testing in Drosophila: VIII. Reexamination of equivocai results
Authors: Mason J. M. , Valencia R. , Zimmering S.
Published: February 2007

Twelve percent of the chemicals tested for mutagenicity by the National Toxicology Program (NTP) using the Drosophila sex‐linked recessive lethal assay have been classified as producing equivocal results. We have reexamined the published data and the criteria used to determine mutagenicity in light of the historical distribution of the concurrent negative controls for this project. Many of the chemicals that originally produced equivocal results have been retested under code. As a result of changes to incorporate a comparison with the historical control in the algorithm used to determine mutagenicity and as a result of new data accumulated, 4 of the 25 chemicals that gave equivocal results are judged to be mutagenic, and 11 others are judged to be nonmutagenic under our test conditions.
Effects of plate preparation on results in microbial mutation assays
Authors: Majeska Jenness B. , McGregor Douglas B.
Published: February 2007

Glucose autoclaved in an alkaline phosphate solution (heated glucose + salts, HGS) results in the production of a moiety that is nonmutagenic but can interact with a series of 4‐[2‐(aryl)ethenyl]‐2,6‐dimethylphenols to result in an increase in bacterial revertants that is dependent on the amount of HGS in the minimal agar plates. The reaction between the HGS and the chemical to form a mutagen is independent of the presence of bacteria, does not result in a nutritive analog to enhance growth of the auxotrophic bacteria, and is effective only in Salmonella typhimurium and Escherichia coll strains that contain the plasmid pKM101. A sufficient amount of this glucose product may be formed in normal plate preparation to produce apparent mutagenic activity of these chemicals.
Genetic and environmental influences on baseline SCE
Authors: Hirsch Betsy A. , Sentz Karen K. , McGue Matt
Published: February 2007

Previous population‐based studies have identified subject characteristics that, when combined, can account for ∼20% of the observed interindividual variation in baseline SCE rates. In the present investigation, a classic twin study design was used to address the issue of the relevance of genetic factors to baseline SCE rates and to identify other demographic, hematologic, and exposure variables predictive of SCE rate. Questionnaire data and peripheral blood samples from 136 monozygotic and 88 dizygotic twins (age range: 25–81 years) were obtained. Among the large number of variables examined, univariate analyses (including ANOVA tests for the categorical variables and Pearson‐product moment correlations for the quantitative variables) revealed smoking status, coffee drinking status, sex, white blood cell count, and absolute numbers of lymphocytes and neutrophils to have significant effects on SCE rates. A stepwise multiple regression analysis showed that together, smoking and coffee drinking status entered at the first step accounted for 21% of the observed variance in SCE, with a further 6% being contributed by the demographic and hematologic variables added in subsequent steps. Finally, the twin analyses showed that after adjustment of the data set for smoking and other significant predictors, genetic factors accounted for ∼30% of the variation in SCE rates. Thus these data support the hypothesis of a significant genetic influence on baseline SCE. © 1992 Wiley‐Liss, Inc.
Molecular analysis of mutations induced by the intercalating agent ellipticine at the hisd3052 allele of salmonella typhimurium TA98
Authors: Demarini David M. , Abu‐Shakra Amal , Gupta Ranjan , Hendee Linda J. , Levine Jessie G.
Published: February 2007

We have used DNA colony hybridization, the polymerase chain reaction (PCR), and direct DNA sequencing to determine the mutations induced by the intercalating agent ellipticine in Salmonella typhimurium TA98 in the presence of S9. Of 400 ellipticine‐induced revertants that were selected at a mutant yield that was ninefold over the background, 85.5% contained a GC or CG deletion within a common CGCGCGCG hotspot; this deletion occurred among 47% of the spontaneous revertants. In addition to this hotspot, the ellipticine spectrum contained two deletion warmspots that reside opposite each other in looped‐out regions of a possible DNA secondary structure. Ellipticine and its metabolites likely revert Salmonella strain TA98 by forming DNA adducts that promote slippage‐mismatches and by stabilizing these slipped mismatched sequences via intercalation. The involvement of these mechanisms, along with a likely role for DNA secondary structures and a possible role for DNA gyrase, may account for the site specificity exhibited by ellipticine in strain TA98. © 1992 Wiley‐Liss, Inc.
Mitogenic activity of quinoline to the rat, mouse, and guinea pig liver: Empirical correlations with hepatic carcinogenicity
Authors: Lefevre P. , Ashby J.
Published: February 2007

Previous studies have shown that the rat liver carcinogen quinoline is essentially nongenotoxic to the rat liver in vivo. Those studies also established it as a potent mitogen to rat liver. The present experiments have established quinoline as a mitogen to the mouse liver, a tissue in which it is also reported to be carcinogenic. In contrast, quinoline is reported to be noncarcinogenic to the guinea pig liver, and the present data establish it to be essentially nonmitogenic to the guinea pig liver. It is concluded that the mitogenicity of quinoline correlates better with its hepatocarcinogenic properties than does its genotoxicity in vivo. © 1992 Wiley‐Liss, Inc.
Mutations causing defective splicing in the human hprt gene
Authors: Andersson Björn , Hou Sai‐Mei , Lambert Bo
Published: February 2007

Ten intron mutations and one exon mutation giving rise to defective splicing in the human gene for hypoxanthine phosporibosyl transferase (hprt) in T‐lymphocytes have been characterized. the splicing mutants were detected by PCR amplification of hprt cDNA and direct sequencing. Nine of the mutants showed skipping of whole exons or parts of exons in the cDNA, one mutant had an inclusion of an intron sequence into the cDNA, and one mutant showed both inclusion of an intron sequence and skipping of exons as well as a normal cDNA. Genomic PCR and direct sequencing of the splice sites involved showed one deletion of three base pairs and 10 different single base alterations to be responsible for these splice alterations. One mutation in the last base pair of exon 6 causing skipping of the entire exon 6 was found, whereas an identical mutation in the last base pair of exon 2 caused no aberrant splicing. It was also found that a deletion mutation in the pyrimidine rich stretch of the acceptor site of intron 7 caused skipping of the entire exon 8, whereas a base substitution in the last base of intron 7 caused exclusion of only the first 21 base pairs of exon 8 as a result of the activation of a cryptic acceptor site in exon 8. The results show that many different types of mutations at several different sites can cause splicing errors in the hprt gene and that the sequence differences between the splice sites influence the possible spectrum of mutations in each site. © 1992 Wiley‐Liss, Inc.
Effects of captan on dna and dna metabolic processes in human diploid fibroblasts
Authors: Snyder Ronald D.
Published: February 2007

The fungicide Captan has been examined for its effects on DNA and DNA processing in order to better understand the genotoxicity associated with this agent. Captan treatment resulted in production of DNA single strand breaks and DNA‐protein cross‐links and elicited an excision repair response in human diploid fibroblasts. Captan was also shown to inhibit cellular DNA synthesis and to form stable adducts in herring sperm and human cellular DNA. Misincorporation of nucleotides into Captan‐treated synthetic DNA templates was significantly elevated in an in vitro assay using E. coli DNA polymerase I, suggesting that DNA adduct formation by Captan could have mutagenic consequences. In sum, these studies demonstrate that Captan is capable of interacting with DNA at a number of levels and that these interactions could provide the basis for Captan's genotoxicity. The extreme cytotoxicity of this fungicide, however, could be due to other cellular effects since at the IC50 for cell killing, approximately 0.8 μM, none of the above genotoxic events could be detected by the methods employed. © 1992 Wiley‐Liss, Inc.
Posttreatment with sodium arsenite alters the mutational spectrum induced by ultraviolet light irradiation in chinese hamster ovary cells
Authors: Yang Jia‐Ling , Chen Mei‐Fang , Wu Cheng‐Wen , Lee Te‐Chang
Published: February 2007

Arsenic, a potent carcinogen, fails to induce gene mutations in mammalian cells. However, posttreatment of ultraviolet light (UV) irradiated cells with sodium arsenite synergistically enhances the mutation frequency on the hypoxanthine (guanine) phosphoribosyltransferase locus. To investigate the molecular mechanism of the comutagenic effects of sodium arsenite, we characterized the alterations of nucleotide sequences in 30 UV‐induced and 39 sodium arsenite enhanced hprt mutants from Chinese hamster ovary K1 cells by direct sequencing of mRNA‐PCR amplified cDNA. The majority of sequence alterations derived from UV irradiation (80%) and from sodium arsenite posttreatment (70%) were single base substitutions. UV irradiation induced all types of base substitutions. Among them, 57% were transversions. The frequency of transversions increased to 70% in sodium arsenite enhanced mutants. While base substitutions observed in UV‐induced mutants were evenly distributed along with the whole coding region, exons 3 and 8 were most frequently mutated in sodium arsenite enhanced mutants. Sodium arsenite posttreatment did not alter the strand bias for mutation induction, i.e., 73% and 78%, of the mutations were located on the non‐transcribed strand in UV‐induced and sodium arsenite enhanced mutants, respectively. In contrast to UV‐induced mutations, bases at the 5' position of TT and the 3' position of CT sequences were the most frequent mutation sites observed in sodium arsenite enhanced mutants. We hypothesize that sodium arsenite may interfere with the process of mutation fixation of TT and CT dimers during DNA replication. © 1992 Wiley‐Liss, Inc.
Optimization of the concurrent assay for gene mutations and chromosomal aberrations in vivo: Expression time in rats
Authors: Khan Mohammed A. , Heddle John A.
Published: February 2007

Ethylnitrosourea was used as a model mutagen to determine the time at which the most mutants and chromosomal aberrations could be detected. Primary fibroblasts derived from Fischer (F344) rats that had been mutagenized by ethylnitrosourea in vivo, were grown in culture and sampled at increasing intervals to analyze, quantitatively, gene mutations and chromosomal aberrations. Since ethylnitrosourea reacts very quickly and the cells were isolated five hours after treatment, expression time represents the intracellular processes involved, not the pharmacokinetics of the mutagen. A thioguanine selection procedure was used to quantify gene mutations. A cytochalasin B technique for micronuclei was used to quantify chromosomal aberrations. A significant increase in the number of mutations was observed on the ninth day in an experiment wherein sampling was done at increasing intervals of three days. One of two experiments wherein sampling was done at increasing intervals of five days showed maximum number of mutations in dishes plated with cells, exposed to maximum dose (200 mg/ kg), on the tenth day for selection. Cells that received dose 100 mg/kg on the contrary produced maximum number of mutant colonies in dishes that were plated on the 20th day for selection. A repeat of the 5‐day interval experiment showed maximum number of mutant colonies in dishes selected on the tenth day, irrespective of the dose used. The number of micronuclei reached a maximum on the third day. © 1992 Wiley‐Liss, Inc.
Chlorophyllin‐enhanced excretion of urinary and fecal mutagens in rats given 2‐amino‐3‐methylimidazo[4, 5‐f]quinoline
Authors: Dashwood Roderick , Liew Christina
Published: February 2007

Sodium/copper chlorophyllin (CHL) is a water‐soluble derivative of chlorophyll that exhibits antimutagenic activity in several short‐term genotoxicity assays and inhibits carcinogen‐DNA binding in vivo. The effect of CHL pretreatment on the excretion of mutagens in the urine and feces of male Sprague‐Dawley rats has been studied using the Salmonella mutagenicity assay. Animals were given 1 percent CHL in the drinking water for 2 days before administering a single dose of 2‐amino‐3‐methylimidazo‐[4, 5‐f]quinoline (IQ) by oral gavage. Rats pre‐treated with CHL had higher levels of mutagens in the urine and feces compared with animals given IQ alone; 48 hr after IQ administration, the total mutagenic dose excreted was <4% in controls vs. 18% in rats given CHL. Mutagenicity required the presence of an activation system, was unaffected by treatment with β‐glucuronidase or arylsulfatase, and in both the urine and feces was accounted for by increased elimination of unmetabolized parent compound. The results support the view that CHL may operate in vivo as a “desmutagen” or interceptor molecule, interacting with IQ in the gut and tissues, and reducing carcinogen bioavailability. © 1992 Wiley‐Liss, Inc.
Characteristics of spontaneous and induced specific‐locus mutation in the ad‐3 region of neurospora crassa: Utilization in genetic risk assessment
Authors: De Serres Frederick J.
Published: February 2007

Data from experiments on the induction of specific‐locus mutations in model systems are utilized in genetic risk assessment to estimate potential adverse effects in the human population. In such assessments with radiation or chemical mutagens, the following information is required: (1) spontaneous and induced forward‐mutation frequencies, (2) dose‐response curves for the overall induction of specific‐locus mutations, (3) genetic characterization of spontaneous and induced mutations, and (4) dose‐response curves for the different genotypic classes. Specific‐locus assays in most eukaryote assay systems provide only portions of the information required for genetic risk assessment. In recognition of the need for a more comprehensive data base, a model system was developed for specific‐locus studies in Neurospora crassa. The adenine‐3 (ad‐3) specific‐locus assay was modeled after the 2 gene, morphological specific‐locus assay in the dilute‐short‐ear region of the mouse, and it detects forward‐mutations at two closely linked loci: ad‐3A and ad‐3B. The ad‐3 assay system has provided precise dose‐response curves not only for inactivation, but also the overall induction of ad‐3 mutations. The utilization of this assay in experiments with radiation or chemical mutagens has provided a data base on the induction and genetic characterization of specific‐locus mutations that is unique among eukaryotic organisms. In this assay, gene/point mutations, multilocus deletion mutations, and 3 different classes of multiple‐locus mutations can be identified. The latter consist of specific‐locus mutations associated with recessive lethal mutations located either closely linked to the ad‐3 region or elsewhere in the genome. The overall data base on the heterozygous effects of X‐ray‐induced ad‐3 mutations demonstrates that such effects are allele specific, genotype specific, and locus specific. There are probably a variety of mechanisms by which the heterozygous effects of individual allelic mutations at different genetic loci can be affected. In conclusion, unless the frequencies of all of the different classes of induced specific‐locus mutations are determined, and utilized in genetic risk assessment exercises, the risk of human exposure to environmental mutagens may be grossly underestimated. © 1992 Wiley‐Liss, Inc.
Analysis of DNA strand breaks induced in rodent liver in vivo, hepatocytes in primary culture, and a human cell line by chlorinated acetic acids and chlorinated acetaldehydes
Authors: Chang Lina W. , Daniel F. B. , Deangelo Anthony B.
Published: February 2007

An alkaline unwinding assay was used to quantitate the induction of DNA strand breaks (DNA SB) in the livers of rats and mice treated in vivo, in rodent hepatocytes in primary culture, and in CCRF‐CEM cells, a human lymphoblastic leukemia cell line, following treatment with tri‐ (TCA), di‐ (DCA), and mono‐ (MCA) chloroacetic acid and their corresponding aldehydes, tri‐ (chloral hydrate, CH), di‐ (DCAA) and mono‐ (CAA) chloroacetaldehyde. None of the chloroacetic acids induced DNA SB in the livers of rats at 4 hr following a single administration of 1–10 mmole/kg. TCA (10 mmole/kg) and DCA (5 and 10 mmole/kg) did produce a small amount of strand breakage in mice (7% at 4 hr) but not at 1 hr. N‐nitrosodiethylamine (DENA), an established alkylating agent and a rodent hepatocarcinogen, produced DNA SB in the livers of both species. TCA, DCA, and MCA also failed to induce DNA strand breaks in splenocytes and epithelial cells derived from the stomach and duodenum of mice treated in vivo. None of the three chloroacetaldehydes induced DNA SB in either mouse or rat liver. The continuous exposure of mice to 5 g/L DCA in the drinking water for 7 and 14 days did not induce appreciable hepatic DNA SB (< 10% at 14 days), although peroxisome proliferation, as evidenced by an increased cyanide‐insensitive palmitoyl CoA oxi‐dase (PCO) activity, was stimulated to 490% (7 days) and 652% (14 days) of control. Under this protocol, DENA (0.1 g/L) produced DNA damage after both 7 days (73% of control) and 14 days (57% of control). Similarly, long‐term exposure of rats (30 weeks) to 2 g/L DCA in the drinking water, a level that increased PCO activity to 364% of the control value, exhibited no DNA damage. Both the chloroacetic acids and the chloroacetaldehydes were ineffective in inducing DNA SB in cultured rat and mouse hepatocytes at concentrations below those that yielded cytotoxicity. The chloroacetic acids were also ineffective in the CCRF‐CEM cells. However, two of the chloroaldehydes, DCAA and CAA, did induce DNA SB in the CCRF‐CEM cells at concentrations that did not decrease the cell viability after 2 hr of treatment. Prior incubation of DCAA and CAA with a rat S9 liver homogenate eliminated much of the DNA damaging activity. These studies provide further evidence that the chloroacetic acids lack genotoxic activity not only in rodent liver, a tissue in that they induce tumors, but in a variety of other roden tissues and cultured cell types. Two of the chloroacetaldehydes, DCAA and CAA, are direct acting DNA damaging agents in CCRF‐CEM cells, but not in liver or splenocytes in vivo or in cultured hepatocytes. CH showed no activity in any system investigated. © 1992 Wiley‐Liss, Inc.
Induction of micronuclei by bleomycin in G0 human lymphocytes: II. Potentiation by radioprotectors
Authors: Hoffmann George R. , Colyer Shirley P. , Littlefield L. Gayle
Published: February 2007

Dimethylsulfoxide (DMSO) and WR‐1065 are radioprotectors, in that they reduce the effectiveness with which ionizing radiation causes genetic damage. Unlike their protective effects with radiation, these agents potentiate the induction of micronuclei by bleomycin in the cytokinesis‐block assay in G0 human lymphocytes. High concentrations of DMSO (1 M) are required to cause potentiation. In contrast, WR‐1065 causes dose‐dependent potentiation at relatively low concentrations (1.25 to 10 mM). Cytogenetic analysis supports the results from the micronucleus assay, showing higher levels of genetic damage induced by the combination of bleomycin with DMSO or WR‐1065 than by bleomycin alone. Possible mechanisms of potentiation are proposed. © 1993 Wiley‐Liss, Inc.
Effects of methyl methanesulfonate on mouse sperm chromatin structure and testicular cell kinetics
Authors: Evenson Donald P. , Jost Lorna K. , Baer Rebecca K.
Published: February 2007

Effects of methyl methanesulfonate (MMS) on mouse testicular cell kinetics and sperm chromatin structure were determined flow cytometrically. Mice were exposed to a single ip injection of saline containing 0 or 150 mg/kg MMS, Relative ratios of 1N, 2N and 4N testicular cells were not affected until 22 days postexposure. Ratios of 1N cell types were altered from 13 to 22 days and were near normal by 25 days. This study revealed an MMS induced alteration of chromatin structure in testicular, elongated spermatids by the sperm chromatin structure assay (SCSA), a flow cytometric measure of the susceptibility of acridine orange stained sperm DNA to denaturation in situ. The SCSA also detected alterations in cauda sperm chromatin structure at 3 days, which was 8 days prior to alterations in sperm head morphology, indicating the increased sensitivity of the SCSA. SCSA data were practically similar whether measuring either fresh or frozen/thawed sperm, or whether measured by two different types of flow cytometers: a) laser driven, orthogonal optical axis; or b) low cost mercury arc lamp system with epiillumination. The data support the model of Sega and Owens [Mutat Res 111:227–244:1983] that MMS alkylates cysteine ‐SH groups in sperm protamines, thereby destabilizing sperm chromatin structure and leading to broken chromosomes and mutations. © 1993 Wiley‐Liss, Inc.
Quantitative relationship between ethylated DNA bases and gene mutation at two loci in CHO cells
Authors: Fortini P. , Calcagnile A. , di Muccio A. , Bignami M. , Dogliotti E.
Published: February 2007

In a previous study we showed that the formation of O6‐ethylguanine (O6‐EtGua) in the DNA of CHO cells in culture correlated with mutations induced by ethylnitrosourea (ENU) and diethylsulfate (DES) at the hypoxanthine‐guanine‐phosphoribosyltransferase (hprt) locus but not at the Na, K‐ATPase locus. This study was extended to another ethylating agent, ethyl methanesulfonate (EMS). DNA adduct formation and induction of mutation at the two gene loci were determined simultaneously in CHO cells after EMS exposure. The extent of ethylation at the N7 and O6 positions of guanine and at the N3 site of adenine were measured and the possible correlations with 6‐thioguanine resistance (6‐TGr) and ouabain resistance (ouar) mutations were investigated. A good correlation between the levels of ethylation at O6 guanine and mutation frequency at hprt gene by all three ethylating agents was observed. In the case of the ouar locus, the frequency of O6‐EtGua adducts correlated with mutation induction by EMS and ENU but not by DES. Although both EMS and DES have similar reaction mechanisms, these results highlight differences in their mutational specificity. The comparison of this type of analysis with mutational spectra revealed that correlation studies may be inadequate to analyse multi‐component phenomena like mutation formation. © 1993 Wiley‐Liss, Inc.
Genotoxicity of volatile and secondary reactive oxygen species generated by photosensitization
Authors: Camoirano A. , de Flora S. , Dahl T. A.
Published: February 2007

Reactive oxygen species were generated in the gas phase by photosensitization involving illumination of Rose Bengal. Depending on whether the chromophore is dry or solubilized, this system produces either energy‐transfer reactions leading to generation of singlet oxygen specifically, or a combination of energy‐transfer and electron‐transfer reactions, providing both singlet oxygen and reduced forms of oxygen, such as superoxide anion and hydrogen peroxide. In neither case were the reactive species mutagenic in strain TA104 of Salmonella typhimurium, which had been previously shown to be reverted by oxygen species generated by the hypoxanthine‐xanthine oxidase system in aqueous medium. However, mixed oxygen species induced an increased lethality in a variety of DNA repair‐deficient Escherichia coli strains. This genotoxic effect, mainly reparable by the uvrA and recA mechanisms, was efficiently prevented by the thiol N‐acetyl‐L‐cysteine. Singlet oxygen itself failed to exert direct genotoxic effects, although secondary reactants produced by its reaction with cell components enhanced lethality in some repair‐deficient bacteria. Distance‐dependence analyses provided measurements of the lifetimes of the oxygen species generated in the gas phase. © 1993 Wiley‐Liss, Inc.
Relative efficiency of Phyllanthus emblica fruit extract and ascorbic acid in modifying lead and aluminium‐induced sister‐chromatid exchanges in mouse bone marrow
Authors: Dhir Haimanti , Roy Ajoy Kumar , Sharma Archana
Published: February 2007

The identification of desmutagens and bioantimutagens in plants has prompted the search for additional plant extracts capable of modifying adverse cellular effects of environmental toxicants. The protective action of crude extracts of Phyllanthus emblica fruits (PFE) against lead (Pb) and aluminium (Al)‐induced sister chromatid exchanges (SCEs) was studied in bone marrow cells of Mus musculus. The modifying effect of the crude extract was compared with that of comparable amounts of synthetic ascorbic acid (AA), a major component of the fruits. Oral administration of PFE or AA for 7 consecutive days before exposure of mice to the metals by intraperitoneal injections reduced the frequencies of SCEs induced by both metals. PFE afforded a more pronounced protective effect than AA in counteracting the genotoxicity induced by both Al and Pb: This difference was significant with Pb. The higher protection afforded by PFE may be attributed to the interaction of AA with other natural ingredients present in the crude fruit extract. ©1993 Wiley‐Liss, Inc.
Base‐pair mutations caused by six aliphatic epoxides in salmonella typhimurium TA100, TA104, TA4001, and TA4006
Authors: Einistö P. , Hooberman B. H. , Sinsheimer J. E.
Published: February 2007

Salmonella typhimurium strains TA100, TA104, TA4001, and TA4006 were used to detect the base‐pair mutations caused by six aliphatic epoxides: chloropropylene oxide, glycidyl 1‐naphthyl ether, glycidyl 4‐nitrophenyl ether, 1‐naphthyl‐propylene oxide, styrene oxide, and trichloropropylene oxide. Dose‐mutagenicity relationships could be established for all six epoxides in strains TA100 and TA104 but not in strains TA4001 and TA4006. These results, together with the lack of sensitivity of the TA100 revertants to DL‐1,2,4‐triazole‐3‐alanine, indicate CG→TA transitions and/or CG→AT transversions are of major importance for mutations induced by these epoxides in Salmonella TA100 and possibly TA104. In addition, since the reproducibility of the effect of the triazole on TA104 reversions was poor, TA→AT transversions were not eliminated as also contributing to the mutagenicity of these epoxides in this Salmonella strain. © 1993 Wiley‐Liss, Inc.
Highly sensitive umu test system for the detection of mutagenic nitroarenes in Salmonella typhimurium NM3009 having high O‐acetyltransferase and nitroreductase activities
Authors: Oda Yoshimitsu , Yamazaki Hiroshi , Watanabe Mosahiko , Nohmi Takehiko , Shimada Tsutomu
Published: February 2007

A highly sensitive umu test system for the detection of genotoxic activities of a variety of mutagenic nitroarenes has been developed using a new tester strain, Salmonella typhimurium NM3009 having high O‐acetyltransferase (O‐AT) and nitroreductase (NR) activities. The NM3009 was constructed by subcloning both the O‐AT and NR genes into plasmid vector pACYC184, and the resulting plasmid was introduced into the parent tester strain S. typhimurium TA1535/pSK1002 harboring an umuC‘‐’lacZ fusion gene. The induction of umuC gene expression could be monitored by measuring the cellular β‐galoctosidase activity produced by fusion gene. The purpose of the study was to evaluate whether the newly developed strain NM3009 is highly sensitive toward nitroarene compounds. The sensitivity of the strain NM3009 was compared with those of the parent TA1535/pSK1002 strain, the NR‐overexpressing strain NM1011, the NR‐deficient strain NM1000, the O‐AT‐over‐expressing strain NM2009, and the O‐AT‐defective strain NM2000. The newly developed NM3009 strain had about 13‐fold and 3‐fold higher activities for N‐AT and NR, respectively, than the original S. typhimurium TA1535/pS1002 strain. Among six strains tested, NM3009 showed the highest sensitivity toward such chemicals as 1‐nitronaphthalene, 2‐nitrofluorene, 3,7‐dinitro‐fluoranthene, 3‐nitrofluoranthene, 5‐nitroacenaphthene, 2‐nitronaphthalene, 1‐nitropyrene, 1,6‐dinitropyrene, 3,9‐dinitrofluoranthene, 4,4′‐dinitrobiphenyl, 1,8‐dinitropyrene, m‐dinitrobenzene, 2,4‐dinitrotoluene, and 1,3‐dinitropyrene. We have also found that the order of sensitivities to induce umuC gene expression toward a variety of nitroarenes was NM3009 > NM2009 > NM1011 > TA1535/pSK1002 > NM2000 > NM1000. These results suggest that the newly developed tester strain NM3009 is of great use for the detection of genotoxic activities of numerous carcinogenic and mutagenic chemicals including nitroarenes, which require NR and/or O‐AT for the activation. © 1993 Wiley‐Liss, Inc.
Modification of clastogenicity of three known clastogens by garlic extract in mice in vivo
Authors: Das Tandra , Roychoudhury Arati , Sharma Archana , Talukder Geeta
Published: February 2007

The anticlastogenic activity of crude extract of garlic (Allium sativum L.) was studied in bone marrow cells of mice. Male laboratory‐bred Swiss albino mice were given one of three concentrations of the freshly prepared extract (100 mg, 50 mg, and 25 mg/kg body weight) as a dietary supplement by gavage for 6 consecutive days. On the seventh day the mice were administered a single acute dose of two known clastogens, mitomycin C(1.5 mg/kg) and cyclophosphamide (25 mg/kg) or sodium arsenite (2.5 mg/kg), simultaneously with garlic extract. After 24 hr, chromosome preparations were made from the bone marrow cells. The endpoint studied were chromosomal aberrations and damaged cells. Garlic extract alone induced a low level of chromosomal damage. The clastogenicity of all three mutagens were reduced significantly in the animals which had been given garlic extract as dietary supplement. The extent of reduction was different for the three clastogens and may be attributed to the interaction with the different components of the extract. © 1993 Wiley‐Liss, Inc.
Correlation of frameshift mutagenicity with dna intercalation by CGS 20928A using an in vitro DNA unwinding assay
Authors: Mattes W. B. , Kapeghian J. C. , Lasinski E. R. , O'Lone S. D. , Puri E. C. , Matheson D. W.
Published: February 2007

A compound's mutagenicity in different Salmonella tester strains can suggest its mechanism of reaction with DNA. Clear confirmation of such a mechanism, however, requires a direct test of the compound's reaction with DNA, often relying on specific in vitro studies. We report the use of a rapid in vitro test designed to measure DNA unwinding, a characteristic of DNA intercalators and many frameshift mutagens. CGS 20928A, an adenosine antagonist, produced a significant (<2‐fold) increase in revertants only for Salmonella tester strain TA1537, and only without metabolic activation. These data indicated that the compound was a direct acting frameshift mutagen and possibly intercalated into DNA. Our DNA unwinding assay indicated that at concentrations of <0.1 mM CGS 20928A behaved like known intercalating compounds in that it unwound DNA. These concentrations of compound are comparable to those found mutagenic to TA1537. By comparison, the frameshift mutagen and known intercalating compound 9‐aminoacridine unwound DNA in this assay in a concentration dependent fashion between 6–12 μM. ICR‐191, another acridine frameshift mutagen, also unwound DNA. A compound structurally related to CGS 20928A, which was not mutagenic in Salmonella tester strains, did not produce any DNA unwinding even at 10 mM. Because the assay uses microgram quantities of material, it should be ideal for screening small amounts of congeneric series suspected of frameshift mutagenicity. © 1993 Wiley‐Liss, Inc.
Chemico/biological investigation of contaminated sediment from the hamilton harbour area of Western Lake Ontario
Authors: Marvin C. H. , Allan L. , McCarry B. E. , Bryant D. W.
Published: February 2007

Highly contaminated sediment from the Hamilton Harbour area of western Lake Ontario was examined using a bioassay‐directed fractionation methodology. A sediment sample was extracted using a Soxhlet apparatus and the resulting extract was fractionated into compound classes using an alumina clean‐up step and high performance liquid chromatographic techniques. The resulting fractions were subjected to bioassays using TA98‐ and TA100‐like strains modified by the inclusion of genes for the activating enzymes nitroreductase and O‐acetyl‐transferase. The majority of the mutagenic activity displayed by the sample extract was found to be present in the fraction containing the polycyclic aromatic hydrocarbons (PAH). Extracts of the PAH‐containing fraction displayed dramatically higher responses with the TA100 type strains with metabolic activation. Further separation of the PAH‐containing fraction showed the majority of the biological activity coeluted with PAH having molecular masses of 276, 278, and 302 amu. © 1993 Wiley‐Liss, Inc.
Genotoxic activity detected in soils from a hazardous waste site by the ames test and an SOS colorimetric test
Authors: McDaniels Audrey E. , Reyes Antolin L. , Wymer Larry J. , Rankin Clifford C. , Stelma Gerard N.
Published: February 2007

Ten soil samples from a hazardous waste site were compared for their genotoxic activity by the Ames test (Salmonella reverse mutation assay) and a modified SOS colorimetric test. Polynuclear aromatic hydrocarbons known to produce frameshift mutations were found in high levels in the soils. Salmonella typhimurium TA98, sensitive to frameshift mutations, was selected as the Ames tester strain. Escherichia coli K12 PQ37 (sulA::lacZ) was the SOS tester strain. Organic extracts were prepared from the soil samples by Soxhlet extraction. One set of the soil samples was extracted with methylene chloride and a second set with cyclohexane. Two criteria from reproducible dose‐related increases in response to the soil were used to compare the positive responses: 1) the concentrations required for doubling responses and 2) a minimum concentration required to produce statistically significant increases from background controls. Analysis of variance indicated that with S9 mix, Ames and SOS results were similar for the same soils and solvent extractions. However, without S9 mix, the SOS test was significantly more sensitive than the Ames test to the genotoxins extracted from the soils. Both the Ames and SOS tests detected lower concentrations of genotoxins in methylene chloride than in cyclohexane extracts. The simplicity of the method, reduction in expenses, and results within 1 working day all contribute to the advantages of the SOS test. © 1993 Wiley‐Liss, Inc.
Classification of mutations at the HLA‐A locus by use of the polymerase chain reaction
Authors: Joseph Grant , Grist Scott , Firgaira Frank , Turner David , Morley Alec
Published: February 2007

We investigated whether the polymerase chain reaction (PCR) could be used to determine the mechanism of mutation in lymphocyte clones mutated at the HLA‐A locus. Three polymorphisms, at Factor XIIIA, D6S109, and intron 3 of the HLA‐A gene, were used to study a series of clones previously characterised by Southern blotting (SB) at multiple loci on chromosome 6. For detection of loss of heterozygosity, the results of PCR and SB were concordant in 140 of 141 clones when polymorphism in the Factor XIIIA region was studied and in 144 of 145 clones when polymorphism in the HLA‐A gene was studied. For classification of the mechanism of mutation, PCR and SB gave the same result in 88 of 92 clones (96%) when a combination of the HLA‐A and Factor XIIIA polymorphisms was used and in 46 of 47 clones (98%) when a combination of the HLA‐A and D6S109 polymorphisms was used. The results indicate that PCR provides a simple and reliable method for categorising mutations at the HLA‐A locus as arising from mitotic recombination, deletion, or from presumptive minor changes within the gene. Rare events such as gene conversion, nondisjunction, or large deletions extending to the telomere will be misclassified. However, such events are rare for mutations at this locus. © 1993 Wiley‐Liss, Inc.
Time sequence of events leading to chromosomal aberration formation
Authors: Moore Ruth C. , Bender M. A
Published: February 2007

Investigations have been carried out which have measured the influence of the repair polymerases on the yield of different types of chromosomal aberrations. The studies were mainly concerned with the effect of inhibiting the polymerases on the yield of aberrations. The polymerases fill in single strand regions, and the fact that their inhibition affects the yield of aberrations suggests that single strand lesions are influential in aberration formation.

The results indicate that—

1. There are two actions of polymerases in clastogenesis. One is in their involvement in a G2 repair system, in which the pair of chromatids is concerned, and which does not yield aberrations unless the inhibition is still operating when the cells enter mitosis. The second also operates in G1 and S, and is such that when repair is inhibited, further damage accrues.

2. The second action is affected by inhibiting polymerase but operates even when the repair enzymes are active.

3. The production of chromosomal exchanges involves a series of reactions, some of which are reversible.

4. The time span over which the reactions occur is much longer than has been envisaged previously (e.g., most of a cell cycle). © 1993 Wiley‐Liss, Inc.