bluuebunny/crossref_metadata_2025 huggingface dataset:
Prostaglandin H synthase‐dependent genotoxicity of 2,4‐Diaminotoluene
Authors: Pan Y. H. Laurie , Reddy G. Ramachandra , Reed Gregory A.
Published: February 2007

2,4‐Diaminotoluene (2,4‐DAT), a high volume synthetic compound, is moderately carcinogenic to rodents. We report here that 2,4‐DAT is a substrate for the peroxidase activity of prostaglandin H synthase (PHS). In contrast to many aromatic amines which are activated as mutagens by PHS, we find that 2,4‐DAT is not mutagenic to six S. typhimurium strains with this activation system. The strains tested include YG1006, YG1024, and YG1029, which are far more sensitive to the mutagenicity of aromatic amines and nitroarenes than are the standard tester strains. Although not mutagenic itself, 2,4‐DAT does enhance the mutagenicity of 2‐aminofluorene (2‐AF) in the PHS‐catalyzed system in strains TA98, YG1006, and YG1024, with maximal enhancement of 140%, 1831%, and 1216%, respectively. Half‐maximal enhancement of 2‐AF mutagenicity is observed at 15–20 μM 2,4‐DAT for strains YG1006 and YG1024, and about 80 μM for TA98. Studies with compounds structurally related to 2,4‐DAT revealed enhancement of 2‐AF mutagenicity with 2,5‐DAT and o‐phenylenediamine (o‐PD) but not for other DAT isomers, toluidines, and phenylenediamines. Maximal enhancement of 2‐AF mutagenicity observed in TA98 with PHS‐catalyzed activation was 110% for o‐PD and 60% for 2,5‐DAT. This comutagenic effect of 2,4‐DAT appears quite specific for 2‐AF, as it fails to enhance either the PHS‐dependent mutagenicity of the aromatic amines benzidine and 2‐naphthyl‐amine, or the direct mutagenicity of N‐acetoxyacetylaminofluorene,2‐nitrofluorene,4‐nitroquinoline‐N‐oxide and 1,1,1‐trichloropropene‐2,3‐oxide. Enhancement of 2‐AF mutagenicity by 2,4‐DAT is also observed with cytochrome P‐450‐dependent activation, however the half‐maximal 2,4‐DAT concentration was 400 μM, and the maximal enhancement was only 50%. The ability of 2,4‐DAT, under conditions where it is not itself mutagenic, to enhance the genotoxicity of the potent carcinogen 2‐AF comprises an intriguing toxicological interaction, and underscores the inherent difficulties in assessing the genotoxic risks posed by mixtures of compounds.
Evaluation of genotoxicity, pathological lesions, and cell proliferation in livers of rats and mice treated with furan
Authors: Wilson Daniel M. , Goldsworthy Thomas L. , Popp James A. , Butterworth Byron E.
Published: February 2007

Preliminary results from the National Toxicology Program (NTP) bioassays of furan given by gavage indicate the induction of hepatocellular carcinomas in male F‐344 rats and in both sexes of B6C3F1 mice, and cholangiocarcinomas in both sexes of rats. To assess the genotoxicity of furan, chemically induced unscheduled DNA synthesis was evaluated in the in vivo hepatocyte DNA repair assay. Furan did not induce unscheduled DNA synthesis in hepatocytes isolated after single gavage treatment of male F‐344 rats (5, 30, and 100 mg/kg) or male B6C3F1 mice (10, 50, 100, and 200 mg/kg). Furan induced cytotoxicity and enhanced cell proliferation were evaluated in livers of rats and mice as events that also might give rise to mutations and/or drive tumor formation. The labeling index (Ll, percentage of hepatocyte nuclei in S‐phase) was measured histoautoradiographically following a single gavage administration of furan (30 mg/kg, male rats; 50 mg/kg, male mice) followed by an injection of 3H‐thymidine 2 hr prior to sacrifice. Hepatocellular necrosis and a sharp increase in Ll (23.9 for mice and 17.8 for rats vs. less than 0.5 for controls) was observed 48 hr after treatment with furan, indicative of restorative cell proliferation secondary to cytotoxicity. Hepatocyte proliferation was evaluated also at the highest NTP bioassay dose (15 mg/kg/day for mice and 8 mg/kg/day for rats, 5 days/week) by labeling with 3H‐thymidine administered via a 6 day osmotic pump implanted subcutaneously. Necrosis and inflammation were observed along the subcapsular visceral surface of the left or caudate liver lobes, likely due to diffusion of furan directly through the stomach to the liver. After 6 weeks of furan administration, male and female rats, but not mice, exhibited bile duct hyperplasia as well as metaplasia in the areas of fibrosis along the subcapsular visceral surface of the left or caudate liver lobes. The fold increase in hepatocyte Ll in treated animals relative to the combined controls measured at weeks 1, 3, and 6 ranged from 39 to 5 for male mice, 18 to 51 for male rats, and 12 to 19 for female rats. Taken together, these data suggest that mechanisms other than direct DNA‐reactivity might explain the profile of oncogene mutations observed in the mouse liver tumors, including selective promotion of different subpopulations of preneoplastic cells and/or mutational events secondary to sustained cell proliferation or inflammation. The extensive amount of furan‐induced cell proliferation subsequent to cytotoxicity likely had a significant impact on tumor development, and such data should be considered in risk evaluations for this compound.
Mutagenicity of benzo(a)pyrenyl‐1‐sulfate in the Ames test
Authors: Irwin Susan E. , Kwei Gloria Y. , Blackburn Gary R. , Thurman Ronald , Kauffman Fredrick C.
Published: February 2007

Comparison of the mutagenicity of nine isomeric benzo(a)pyrenyl [B(a)P] phenols conjugated with either sulfate or glucuronide was carried out using strain Salmonella typhimurium TA98. Of the nine conjugates tested, only B(a)P‐1‐sulfate was mutagenic. Accordingly, the mutagenicity of B(a)P‐1‐sulfate was compared with that of B(a)P and 1‐hydroxybenzo(a)pyrene [B(a)P‐1‐OH] in the presence and absence of rat lung S9 and Aroclor‐induced liver S9 with and with out an NADPH‐generating system. B(a)P‐1‐sulfate was slightly mutagenic, whereas B(a)P and the 1‐hydroxy derivative were nonmutagenic when S9 fractions and NADPH were omitted. Addition of induced liver S9 with NADPH caused mutagenicity with B(a) ‐1‐OH>B(a)P>B(a)P‐1‐sulfate. B(a)P‐1‐sulfate was the only mutagenic species when lung S9 was added. This mutagenicity did not require NADPH. Sodium sulfite, an inhibitor of arylsulfatase, decreased the mutagenicity of B(a)P‐1‐sulfate. These data suggest that a unique mutagenic species is generated from B(a)P‐1‐sulfate via arylsulfatase in rat lung.
Genotoxicity of chryseno[4,5‐bcd]thiophene and its sulfone derivative
Authors: Sinsheimer J. E. , Hooberman B. H. , Das S. K. , Savla P. M. , Ashe A. J.
Published: February 2007

Our recent syntheses of chryseno[4,5‐bcd]thiophene together with its potential sulfone metabolite, chryseno[4,5‐bcd]thiophene‐4,4‐dioxide, have made these compounds available for genotoxicity testing. Such toxicity testing is of interest as this thiophene is an isoster of the established carcinogen benzo[a]pyrene and is one of the thiaarenes which are potential environmental contaminants found in fossil fuels. Although the thiophene was less mutagenic than benzo[a]pyrene in Salmonella strains TA98 and TA100 after S9 activation, it exhibited in vivo chromosomal aberration activity equal to that of benzo[a]pyrene in the bone‐marrow cells of mice. A reduced activity with Salmonella as well as in the bone‐marrow cell assay for the sulfone does not support its role as the key active metabolic intermediate for the genotoxicity of the thiophene. Our molecular orbital calculations would be consistent with the concept of activation through a diol‐epoxide mechanism and of fers an explanation for the reduced genotoxicity of the sulfone via this mechanism. These genotoxicity studies support the concern that sulfur isosters of established carcinogenic polycyclic aromatic hydrocarbons could themselves be toxic.
Detection of direct‐acting mutagens in ambient air: A comparison of two highly sensitive mutagenicity assays
Authors: Houk Virginia S. , Goto Sumio , Endo Osamu , Claxton Larry D. , Lewtas Joellen , Matsushita Hidetsuru
Published: February 2007

Ambient air has been shown to contain numerous hazardous pollutants, many of which are known or suspected carcinogens and mutagens. Bioassays play a prominent role in the characterization of these genotoxic pollutants, and as new test methods are developed, it is incumbent upon researchers to evaluate assay performance and report relative merits. In this study, two Salmonella test methods (the spiral and pre‐incubation assays) were assessed to determine their usefulness as screening methods for monitoring direct‐acting mutagens in ambient air. The spiral assay automates the conventional plate‐incorporation assay and has been shown to reduce the labor, materials, and sample mass required to perform mutagenicity testing. The preincubation assay has been shown to enhance test sensitivity for certain classes of compound, thereby reducing the amount of sample required for dose‐response analysis. Both assays were used to test organic extracts of airborne particulate matter collected in Tokyo during the winters of 1988 and 1990. In addition to the conventional tester strains TA98 and TA100, two newly developed YG strains were evaluated. Strains YG1024 and YG1029—derived from TA98 and TA100, respectively—contain an acetyltrans‐ferase plasmid that confers upon the strains greater sensitivity towards nitroarenes. Results from this study indicated that both assays were able to detect direct‐acting mutagens in the Tokyo air samples. The mutagenic activity associated with the samples was directly related to the particle mass present in a given volume of air. Mutagenic response was greater in the spiral assay relative to the preincubation assay, especially when YG tester strains were used. The YG strains were significantly more sensitive to mutation than the TA strains in both assays, which suggests that nitroaromatics are an important class of genotoxic contaminant present in Tokyo air. © 1992 Wiley‐Liss, Inc.
Assessment of the in vivo aneuploidy/micronucleus assay in mouse bone marrow cells with 16 chemicals
Authors: Gudi Ramadevi , Xu Jing , Thilagar Arul
Published: February 2007

Assessment of the in vivo aneuploidy/micronucleus Assay in bone marrow cells with 16 chemicals is described. This assay is based on the detection of kinetochores (KC) in micronuclei (MN) by antikinetochore‐specific (CREST) antibodies. Among sixteen chemicals tested, six were known clastogens, three were known aneuploidy‐inducers, and the other seven were suspected spindle poisons. These chemicals were tested for their ability to induce micronuclei with kinetochore(s) in bone marrow cells of CD‐1 mice. The majority of MN formed in bone marrow cells treated with aneuploidy‐inducing agents contained kinetochore(s) which are considered to be formed from whole chromosomes or centric fragments, while in clastogen treated bone marrow cells, majority of them contained no kinetochore(s) which are considered to be formed from acentric chromosomal fragments. Classification of chemicals into either aneuploidy inducing agents or clastogens is based on the relative frequency of MN with and without KC, respectively. These results suggest that the in vivo aneuploidy/micronucleus assay has a great potential to identify aneuploidy‐inducing agents. © 1992 Wiley‐Liss, Inc.
Cytogenetic effects of vincristine sulfate and ethylene dibromide in human peripheral lymphocytes:Micronucleus Analysis
Authors: Channarayappa  , Ong T. , Nath J.
Published: February 2007

Microncuclei kinetics and persistence in mononucleated and binucleated human peripheral lymphocytes following short‐term (4 hr) and continuous (until harvest) in vitro exposure to vincristine sulfate (VS) and ethlylene dibrode (EDB) were studied. Lymphocytes were exposed to chemicals for various doses and harvested at different culture times. Micronucleus frequenvies were scored in both mononucleated and biucleated cells on the same slide. VS‐treated cells showed a significantly higher incidence of micronucleus in both ononucleated and binucleated cells than controls (p<0.01). The cells treated continuously with VS produced comparatively higher frequencies of micronucleated cells than those treated for 4 hr. Highest micronuclei frequencies were observed 24 hr after chemical treatment in both mononucleated and binucleated cells and decreased later with time. However, the micronucleus frequencies remained significantly higher than the controls even in the cells harvested at 144 hr. VS induced a large number of micronucleated cells with multiple micronuclei. VS also caused a severe decrease in nuclear division due to cytotoxic effect. Lymphoctes treated with EDB for 4 hr and continuously showed a statistically higher incidence of micronuclei in binucleated cells compared to the controls (p<0.05), whereas in mononucleated cells higher micronucleus frequencies were observed only in cultures treated continuously. Continuous presence of EDB induced both dose‐and time‐dependent increase of micronuclei in both mono‐ and binucleated cells(p<0.05). EDB induced relatively few multiple micronucleated cells in comparison with VS. EDB did not affect nuclear divisions even with continuous treatment. HIgh micronucleus frequencies observed at 144 hr harvest following 4 hr treatment of both EDB and VS suggest the persistence of DNA damage in cells. These studies suggest that micronuclei kinetics in human periphearl lymphocytes depends on the genotoxic potentially and cytotoxicity of a geno toxicant. © 1992 Wiley‐Liss, Inc.
Mechanisms for dominance: Adh Heterodimer formation in heterozygotes between ENU or X‐ray induced null alleles and normal alleles in Drosophila melanogaster
Authors: Jiang James C. , Lee William R. , Chang S. H. , Silverman Harold
Published: February 2007

Mechanisms for Dominance: Adh Heterodimer Formation in Heterozygotes Between ENU or X‐ray Induced Null Alleles and Normal Alleles in Drosophila melanogaster

To study mechanisms for dominance of phenotype, eight ENU‐ and four X‐ray‐induced mutations at the alcohol dehydrogenase (Adh) locus were analyzed for partial dominance in their interaction with normal alleles. All ENU and one of the X‐ray mutations were single base substitutions; the other three X‐ray mutations were 9–21 base deletions. All but one of the 12 mutant alleles were selected for this study because they produced detectable mutant polypeptides, but seven of the 11 producing a peptide could not form dimers with the normal peptide and the enzyme activity of heterozygotes was about half that of normal homozygotes. Four mutations formed dimers with a decreased catalytic efficiency and two of these were near the limit of detectability; these two also inhibited the formation of normal homodimers. The mutant alleles therefore show multiple mechanisms leading to partial enzyme expression in heterozygotes and a wide range of dominance ranging from almost complete recessive to nearly dominant. All amino acid changes in mutant peptides that form dimers are located between amino acids 182 and 194, so this region is not critical for dimerization. It may, however, be an important surface domain for catalyzation. © 1992 Wiley‐Liss, Inc.
Investigation of the mutagenic specificity of x‐rays using a retroviral shuttle vector in cho cells
Authors: Skandalis A. , Grosovsky A. J. , Drobetsky E. A. , Glickman B. W.
Published: February 2007

In some biological systems ionizing radiation appears to induce large deletions and rearrangements, while in others point mutations predominate the mutational spectrum. Moreover, while the point mutations are often randomly distributed, some systems exhibit “hot spots.” Retroviral shuttle vectors are particularly useful for investigating the basis of these differences since the genetic target can be conveniently analyzed in a variety of host backgrounds and genomic locations. We have studied the mutational specificity of X‐rays in a Chinese hamster ovary cell line (CHO) containing a stably integrated retroviral shuttle vector, carrying the CHO aprt cDNA as the genetic target. Cells were irradiated with 7 Gy using a 180 kVp X‐ray source. The predominant mutation (87% of all APRT mutants), as determined by Southern analysis, was the complete deletion of the shuttle vector construct. In addition, 23 APRT mutants, carrying an apparently intact shuttle vector, were characterized at the sequence level: 5 were transitions, 9 were transversions, 3 were small deletions or insertions, 4 were frameshifts, and 2 were small rearrangements. Although the type and the location of the point mutations character ized appeared largely random, small deletions, insertions, and frameshifts were frequently associated with direct sequence repeats. © 1992 Wiley‐Liss, Inc.
DNA adduct formation in mice following dermal application of smoke condensates from cigarettes that burn or heat tobacco
Authors: Lee C. K. , Brown B. C. , Reed E. A. , Hejtmancik M. , Mosberg A. T. , Doolittle D. J. , Hayes A. W.
Published: February 2007

A prototype cigarette that heats tobacco (test cigarette), developed by R.J. Reynolds Tobacco Company, has yielded consistently negative results in several in vivo and in vitro genetic toxicology tests. The objective of the present study was to evaluate the potential of cigarette smoke condensate (CSC) from the test cigarette to induce DNA adducts in mouse tissues and compare the results with those obtained with CSC from a reference tobacco‐burning cigarette (1R4F). CD‐I mice were skin‐painted with CSC from reference and test cigarettes three times a week for 4 weeks. The highest mass of CSC applied was 180 mg “tar” per week per animal for both reference and test cigarette. DNA adducts were analyzed in skin and lung tissues using the 32P‐postlabeling method with the P1, nuclease modification. Distinct diagonal radioactive zones (DRZ) were observed in the DNA from both skin and lung tissues of animals dosed with reference CSC, whereas no corresponding DRZ were observed from the DNA of animals closed with either test CSC or acetone (solvent control). The relative adduct labeling (RAL) values of skin and lung DNA from reference CSC‐treated animals were significantly greater than those of the test CSC‐treated animals. The RAL values of the test CSC‐treated animals were no greater than those of solvent controls. The negative results in DNA adduct assays with test CSC are consistent with all previous results of in vivo and in vitro genetic toxicology testing on this cigarette and provide additional evidence that smoke condensate from the test cigarette is not genotoxic. © 1992 Wiley‐Liss, Inc.
Structural basis of the mutagenicity of heterocyclic amines formed during the cooking processes
Authors: Zhang Ying Ping , Klopman Gilles , Rosenkranz Herbert S.
Published: February 2007

A data base consisting of 61 heterocyclic amines formed during food preparation and their desamino analogs were subjected to structure‐activity analysis using the CASE method, a structural activity relational expert system. The program identified the major structural determinants associated with mutagenic activity or lack thereof. The structures identified as contributing to the probability of activity as well as those associated with mutagenic potency were highly predictive of molecules not in the learning set. The major structural determinant, the aromatic amino moiety, and quantum mechanical calculations revealed that the mutagenic potency associated with this functionality derived from their contribution to the energy of the Lowest Unoccupied Molecular Orbital (LUMO.) © 1993 Wiley‐Liss, Inc.
Insertional mutagenesis by transposable elements in the mammalian genome
Authors: Amariglio N. , Rechavi G.
Published: February 2007

Several mammalian repetitive transposable genetic elements were characterized in recent years, and their role in mutagenesis is delineated in this review. Two main groups have been described: elements with symmetrical termini such as the murine IAP sequences and the human THE 1 elements and elements characterized by a poly‐A rich tail at the 3′ end such as the SINE and LINE sequences. The characteristic property of such mobile elements to spread and integrate in the host genome leads to insertional mutagenesis. Both germline and somatic mutations have been documented resulting from the insertion of the various types of mammalian repetitive transposable genetic elements. As foreseen by Barbara McClintock, such genetic events can cause either the activation or the inactivation of specific genes, resulting in their identification via an altered phenotype. Several disease states, such as hemophilia and cancer, are the result of this apparent aspect of genome instability. © 1993 Wiley‐Liss, Inc.
Formation and characterization of bacterial mutagens from reaction of the alternative disinfectant monochloramine with model aqueous solutions of fulvic acid
Authors: Cozzie D. A. , Kanniganti R. , Charles M. J. , Johnson J. D. , Ball L. M.
Published: February 2007

Monochloramine has been suggested as an alternative disinfectant to chlorine to reduce levels of trihalomethanes in treated drinking water, but little is known of the toxicological properties and potential health implications of by‐products specific to the chloramination process. Model aqueous fulvic acid solutions (200–400 mg C/liter), serving as surrogates for humic surface waters, were chloraminated over a range of molar Cl:C ratios from 1:40 to 1:2. The resulting by‐products were extracted into diethyl ether at pH 2 and investigated with the Ames plate incorporation assay. Extractable mutagenicity increased with increasing chlorine and carbon dose up to about 30,000 revertants/liter at Cl:C ratios of 1:2. Mutagenicity was higher in Salmonella typhimurium strain TA100 than in strain TA98, and was decreased in the presence of S9, indicating that the mutagens formed were direct‐acting and induced predominantly base‐pair substitutions. Bovine serum albumin decreased slightly, and glutathione reduced greatly, the mutagenic activity detected in extracts. HPLC fractionation of the by‐products indicated that most of the mutagenic activity was found in the earliest‐eluting (most polar) fraction. The mutagenic by‐products appeared to be qualitatively similar to 3‐chloro‐4‐dichlorome‐thyl‐5‐hydroxy‐2‐(5H)‐furanone (MX) in their chromatographic behavior and responses to glutathione and bovine serum albumin, but were less readily detoxified by S9 than was MX. © 1993 Wiley‐Liss, Inc.
Mutagenicity of iso‐butyl nitrite vapor in the ames test and some relevant chemical properties, including the reaction of iso‐butyl nitrite with phosphate
Authors: Mirvish Sidney S. , Williamson Jan , Babcook David , Chen Sheng‐Chong
Published: February 2007

We examined the mutagenicity of iso‐butyl nitrite (IBM) vapor and aqueous IBN solution in the Ames test to help evaluate the hazard of sniffing this vapor, a habit which might play a role in the induction of Kaposi's sarcoma associated with acquired immune deficiency syndrome. Chemical analysis showed that the saturated vapor contained 190 μg IBM/ml at 25°C, and saturated aqueous solution, 2.6 mg IBN/ml at 2J‐23°C When agar plates containing Salmonella typhimurium TA‐1535 and rat liver S‐9 were exposed to IBN vapor, the number of mutants reached a maximum after 40 min. A mean of 307 mutants/plate (22 × background) was observed when the plates were exposed to IBN vapor for 30 min. Addition of 0.2 ml saturated IBN solution in water to similar plates gave a mean of 179 mutants/plate (7.9 × background) in the absence of S‐9, confirming published results. The S‐9 did not affect the results. Based on the IBN level in medium exposed to IBN vapor, the vapor was apparently 11 times more mutagenic than IBN solution. This was attributed to continuous replenishment of unstable IBN in the medium by the vapor. The half‐life of IBN at 21–23°C was >1 hr for solutions in water and <3 min for solutions in the assay medium. This instability was traced to a reaction with phosphate, presumably hydrolysis to nitrite and iso‐butanol. IBN in solution was 2.8 times more mutagenic than sodium nitrite, suggesting that IBN was not mutagenic because of its conversion to nitrite, Iso‐butanol was not mutagenic. The results demonstrate the potential hazard of sniffing IBN vapor. © 1993 Wiley‐Liss, Inc.
Evaluation of the potential of riddelliine to induce unscheduled DNA synthesis, S‐phase synthesis, or micronuclei following in vivo treatment with multiple doses
Authors: Mirsalis Jon C. , Steinmetz Karen L. , Blazak William F. , Spalding Judson W.
Published: February 2007

Riddelliine (RID) is a pyrrolizidine alkaloid found in plants of the genera Crotalaria, Amsinckia, and Senecio in the United States. RID has been extensively studied in a wide variety of in vitro short‐term genotoxicity tests and has yielded positive responses in most test systems; however, there are fewer data available on the effects of RID in in vivo assays and no data under repeat‐dose regimens. We have evaluated the ability of RID to induce unscheduled DNA synthesis (UDS) in hepatocytes, S‐phase synthesis (SPS) in hepatocytes, and micronuclel in bone marrow from animals dosed for 5 or 30 days in conjunction with prechronic toxicity testing conducted for the National Toxicology Program. Results of this study indicate that RID did not induce an increase in micronucleated polychromatic erythrocytes (PCE) in bone marrow of mice after 5 days of dosing or in PCE from rats or mice after 30 days of dosing. RID did not induce an increase in UDS in rat hepatocytes after 5 or 30 days of dosing, but it did induce an equivocal UDS response in male mice after both time points and a positive response in female mice after 30 days of dosing. RID induced significant elevations in SPS in rat hepatocytes after both 5 and 30 days of dosing, even at low doses. An increase in SPS was observed in male and female mouse hepatocytes, but only after 30 days of dosing. Rats and mice of both sexes showed a depression in SPS at higher doses. This effect may be a result of toxicity, which compromises the ability of the liver to regenerate. These results demonstrate that repeated administration of test chemicals may alter the genotoxic response to chemicals. © 1993 Wiley‐Liss, Inc.
Analysis of restriction enzyme‐induced chromosomal aberrations by fluorescence in situ hybridization
Authors: Columna Elma Abella , Giaccia Amato J. , Evans James W. , Yates Barbara L. , Morgan William F.
Published: February 2007

Fluorescence in situ hybridization and Giemsa staining of metaphase chromosomes were used to determine the relative frequencies of symmetric exchange aberrations (translocations) and asymmetric exchange aberrations (rings, dicentrics, and polycentrics) after exposure of human lymphoblastoid cells to restriction enzymes or X‐rays. The yield of symmetric exchanges was determined with the use of chromosome‐specific probes for human chromosomes 2 or 4, which were hybridized to metaphase chromosomes from cells exposed to the enzymes Pvull, Sacl, or Xbal or 3 or 5 Gy of X‐rays. The yield of asymmetric exchanges was determined in Giemsastained metaphase chromosomes from the same enzyme‐treated or irradiated cell population. About 1.5‐ to 3‐fold more symmetric than asymmetric exchanges were induced after restriction enzyme treatment. However, after X‐ray treatment the yield of dicentrics relative to the yield of reciprocal translocations was close to the expected 1:1 ratio.
Effect of temperature on frequencies of spots in drosophila wing‐spot assay
Authors: Katz Alan J. , Foley Teresa A.
Published: February 2007

The effect of temperature on spontaneous mutation frequencies was studied in the Drosophila somatic mutation and recombination test. Transdihybrid mwh +/+ flr3 larvae were grown at various temperatures (15, 18, 20, 22, 25, 27, and 29°C) in the absence of any chemical mutagen. Wings of surviving adults were removed and scored for presence of small single spots, large single spots, and twin spots. No significant effect of temperature was found on mean frequency per wing of twin spots. Similarly, no significant effect of temperature was found for large singles within the temperature range of 18–29°C; however, at 15èC, the mean frequency per wing of large spots was significantly elevated. A significant quadratic relationship was found between mean frequency of small spots and temperature. Frequency of small spots per wing was minimized within the temperature range of 20‐27°C and increased at higher and lower temperatures. Maximum frequency of small spots per wing was observed at 15°C. The qualitative nature of the small single spots induced at high and low temperatures is unclear; they may represent slow‐growing segmentally aneuploid (deleted) cells or possibly even monosomic cells. Both heat and cold were found to be mutagenic in the Drosophila wing‐spot assay. However, the mutagenic potency associated with temperature was much less than that of most chemical mutagens, and no significant effect of temperature was observed in the range of 20–27°C. © 1993 Wiley‐Liss, Inc.
Molecular analysis of hypoxanthine phosphoribosyl transferase mutants induced by glycidyl 1‐naphthyl ether in mouse spleen cells in vivo
Authors: Tan R. S. , Chu E. H. Y. , Sinsheimer J. E.
Published: February 2007

Treatment of C57BL/6J mice with an epoxide, glycidyl 1‐naphthyl ether (GNE), resulted in an average of a 3.4‐fold increase in frequency of 6‐thioguanine‐resistant mutants of mouse spleen T‐lymphocytes. In similar experiments with the epoxide trichloropropylene oxide, no increase in mutant frequency was found. To determine the kind and location of mutations in the coding region of the hypoxanthine phosphoribosyl transferase (HPRT) gene, 26 GNE‐induced mutants and 17 spontaneous mutants were analyzed by direct sequencing of polymerase chain reaction amplified cDNA. Among the GNE‐induced mutants, HPRT cDNA was present in 22, while that from 4 could not be detected. Among the spontaneous mutants, HPRT cDNA was present in 15 and absent in 2. Among GNE‐induced mutants, base substitution in HPRT occurred in 15 of 22 mutants analyzed. Nine of 15 base substitutions involved TA base pairs, primarily TA→CG transitions. Base substitutions were found throughout exons 3–7 but 46% of substitutions were located in exon 3 and one frameshift mutation involving a GC base pair in exon 3 was also observed. Among the spontaneous mutants, base substitutions of HPRT occurred in 7 of 15 mutants analyzed with 6 of 7 base substitutions involving a TA base pair and another 2 of the 15 mutants showed a 4 base pair deletion. The base substitution spectrum in GNE‐induced mutants was different from that of the spontaneous mutants. © 1993 Wiley‐Liss, Inc.
Amesfit: A microcomputer program for fitting linear‐exponential dose‐response models in the ames salmonella assay
Authors: Leroux Brian G. , Krewski Daniel
Published: February 2007

The Ames Salmonella/microsome assay remains the most widely used microbial test for genotoxicity. In this article, we describe a microcomputer program developed to fit a linear‐exponential dose‐response model to Ames assay data for established mutagens. The model includes a linear term to describe the mutagenic effects of the test agent at low to moderate doses and an exponential attenuation factor to accommodate downturns at high doses due to cytotoxicity. Quasi‐likelihood methods are used to obtain estimates of the unknown model parameters, thereby avoiding the need to fully specify the distribution of the experimental data. This method of estimation also allows for extra‐Poisson variation that is characteristic of counts of mutant colonies of bacteria observed in the Ames assay. The particular linear‐exponential model used here was developed for use in the analysis of a recent large‐scale collaborative trial using the Ames assay sponsored by the International Programme on Chemical Safety. The use of our program is illustrated using sample data sets taken from that collaborative study. © 1993 Wiley‐Liss, Inc.
Investigation of aneuploidy induction in mouse oocytes following exposure to vinblastine‐sulfate, pyrimethamine, diethylstilbestrol diphosphate, or chloral hydrate
Authors: Mailhes John B. , Aardema Marilyn J. , Marchetti Francesco
Published: February 2007

The various causative and mechanistic phenomena associated with aneuploidy induction require considerable investigation to better understand the etiology of chromosome missegregation. We investigated the potential of vinblastine sulfate, pyrimethamine, diethylstilbestrol diphosphate, and chloral hydrate to induce numerical and structural chromosome changes in female mouse germ cells. Superovulated ICR mice were administered the compounds either by intraperitoneal injection or oral gavage, and oocytes were collected and processed for cytogenetic analysis 17 hr later. Vinblastine sulfate, administered i.p., induced a significant increase in the frequency of ovulated Ml oocytes and of hyperploid Mll oocytes compared to controls, but did not increase the frequency of structural aberrations. Pyrimethamine, diethylstilbestrol diphosphate, and chloral hydrate did not increase the frequency of numerical or structural chromosome changes in female mouse germ cells. © 1993 Wiley‐Liss, Inc.
Modulation of the H2O2‐induced SOS response in escherichia coli PQ300 by amino acids, metal chelators, antioxidants, and scavengers of reactive oxygen species
Authors: Müller Jürgen , Janz Siegfried
Published: February 2007

The SOS chromotest is a simple colorimetric genotoxicity assay that monitors DNA repair by measuring the induction of the gene sfiA in Escherichia coli K‐12. E. coli PQ300, a diagnostic SOS tester strain for the detection of oxidative genotoxins, carries a mutation in a key gene for antioxidative defense, oxyR. This mutation renders PQ300 more sensitive to oxidative genotoxins, particularly to H2O2. We found that induction of the SOS response by H2O2 in E. coli PQ300 is dependent on the composition of the incubation medium; a substantially reduced response was obtained in minimal phosphate buffered saline (PBS) as opposed to complex Luria broth (LB) medium. Supplementation of PBS with histidine or cysteine stimulated H2O2‐induced SOS induction to levels exceeding those found in LB medium. Low concentrations of glutathione (20–70 μM) also enhanced the H2O2‐induced SOS response in E. coli PQ300, whereas higher concentrations (>150 μM) were protective. Preincubation of tester cells with the chelators o‐phenanthroline, 2,2‐dipyridyl, and ethylenediaminetetraacetic acid (EDTA) protected cells from the effects of H2O2, although EDTA was only partially effective. Pretreatment of PQ300 with the antioxidant ascorbic acid or the hydroxyl radical scavenger dimethyl sulfoxide also diminished the SOS response, whereas mannitol and glucose were ineffective. The results show that the net effect of H2O2‐induced DNA damage is influenced by the balance of oxidative and antioxidative factors and, furthermore, can be modulated by constituents of the extracellular milieu. © 1993 Wiley‐Liss, Inc.
Screening of Azo dyes for mutagenicity with ames/salmonella assay
Authors: Kaur Anupam , Sandhu R. S. , Grover I. S.
Published: February 2007

Azo dyes, the largest portion of manufactured dyestuffs, are primarily used as colouring substances in food, textiles, and the plastic industry. It has been estimated that 128 tonnes per annum of dyes are released into the environment worldwide [Anliker, 1977]. Certain azo compounds are known to be mutagenic in bacterial tests [Yahagi et al., 1975; Venitt and Bushell, 1976; Brown et al., 1978]. Watersoluble dyes are biotransformed by intestinal micro‐organisms in the gastro intestinal tract, and the toxicity, mutagenicity, and carcinogenicity of these dyes in the gut or liver may be attributed to their metabolites. Since it is desirable to have a genotoxic evaluation of a chemical being released into the environment in order to check their indiscriminate use, a project has been initiated to determine the mutagenicity of the azo dyes being used commercially. The present report deals with the results of 13 dyes tested in Salmonella typhimurium with and without metabolic activation. © 1993 Wiley‐Liss, Inc.
G2 chromatid aberrations: Kinetics and possible mechanisms
Authors: Bryant Peter E. , Slijepcevic Predrag
Published: February 2007

Chromatid breaks and exchanges are induced by radiation in G2 mammalian cells. Breaks are at a maximum number at about 30 min after irradiation and decrease apparently exponentially with time between irradiation and sampling. Few breaks are observed immediately following exposure, probably as a result of selection of mitotic cells where chromosomes are condensed and there is consequently a lack of time for expression of damage. The change in frequency of breaks with time, from 30 min after radiation exposure and onwards, can be interpreted in two possible ways: either in terms of a repair process or in terms of a change in radiosensitivity through G2. However, our results with an inhibitor of repair of DNA double‐strand breaks (ara A) and with “transient hypothermia” which extends the G2 phase, argue for an interpretation based on rejoining of chromatid breaks, possibly reflecting the repair of a subclass of dsb. Data from experiments with irradiated and restriction endonuclease treated radiosensitive mutant rodent lines indicate that enhanced levels of conversion of dsb into chromosomal aberrations may be largely independent of repair rates of bulk dsb. In CHO cells and in human lymphocytes exchanges initially increase rapidly with time and then remain at a constant frequency, supporting the notion of a uniform chromosomal radiosensitivity throughout most of G2 and providing further evidence that the mechanism for mis‐joining broken chromatids (leading to exchanges) is different from that for rejoining of chromatid breaks. Ratios of breaks to exchanges were found to vary in different cell lines and at different times during treatment with inhibitors or at altered temperatures, possibly (in different cell lines) indicating different levels of enzymes involved in misjoining, but suggesting that the mechanisms of chromosomal rejoining and misjoining are independent, at least to some degree. © 1993 Wiley‐Liss, Inc.
Molecular mechanisms for the induction of chromosomal aberrations in CHO cells heated in S phase
Authors: Wong Rosemary S. L. , Dewey William C.
Published: February 2007

Chromosomal aberrations are induced by heat only when Chinese hamster ovary cells are heated in S phase of the cell cycle. Studies on the hyperthermic inhibition of cellular DNA replication have indicated that four molecular aspects of DNA replication are affected after heating. New replicon initiation and DNA chain elongation are inhibited; the fork displacement rate is very sensitive to heat‐inactivation; and finally, there is almost a two‐fold increase in single‐stranded regions in the replicating DNA after heating. From a comparison of these altered processes between S phase cells and heated G1 cells, which do not die from chromosomal aberrations, our current hypothesis involves 3 steps for the chromosomal aberration induction process. The first critical step is the persistent increase of single‐stranded regions in the replicating DNA. Then, we hypothesize that the second step is the creation of transient double strand breaks (DSBs) induced at sites opposite these regions by endogenous endonucleases. Finally, the third step requires that improper repair of these DSBs occurs from either nonrepair or misrepair which then leads to the final chromosomal aberrations seen in the first mitosis after treatment. We believe that this 3 step induction process is common for any cytotoxic agent that induces chromosomal aberrations after DNA replication has been inhibited. © 1993 Wiley‐Liss, Inc.
Mechanism of induction of chromosomal aberrations by inhibitors of DNA topoisomerases
Authors: Palitti F.
Published: February 2007

Evidence is provided that antitopoisomerase drugs induce chromosomal aberrations via the formation of DNA double strand breaks. Camptothecin, an inhibitor of DNA topoisomerase I, produced only chromatid‐type aberrations, and in order to be effective it has to be present during the DNA replication. The fact that it induces chromosomal aberrations also in the G2 phase of the cell cycle suggests the presence of a residual DNA synthesis in this phase. A pretreatment with aphidicolin, an inhibitor of DNA polymerases, reduces the camptothecin induced aberrations in the G2 phase, confirming the need of DNA synthesis for the induction of aberrations by the inhibitor of DNA topoisomerase I. © 1993 Wiley‐Liss, Inc.
Detection of opiate‐enhanced increases in DNA damage, HPRT mutants, and the mutation frequency in human HUT‐78 cells
Authors: Shafer David A. , Xie Yiping , Falek Arthur
Published: February 2007

In previous studies we have shown highly significant increases in chromosome damage and sister chromatid exchanges in heroin addicts, particularly when caffeine and metabolic inhibitors are added to the medium. Using human HUT‐78 T‐cell cultures, we now find direct in vitro evidence of opiate‐induced or opiate‐promoted mutagenesis via several assay systems. First, with microgel electrophoresis (MGE), we observed graded, dose‐dependent, significant increases (P < .0001) in the frequency of comet tails of fragmented DNA when cells were treated with morphine alone (5 × 10−9M up to 10−7M) or when co‐treated with the more potent mutagen, ethylmethanesulfonate (EMS). There were also dose‐dependent increases in the lengths and densities of the comet tails observed. These findings were confirmed by a series of MGE experiments in which several days of morphine exposure preceded a 2‐hr pulse of EMS. Second, mutant frequency (MF) assays also indicated significant opiate effects. These studies required separate assessment of cloning efficiencies and the frequencies of TG‐resistant, HPRT‐deficient mutant clones under four test conditions: no treatment, morphine alone for 4 days, morphine plus EMS, and EMS alone. Prior to the treatment phase, aminopterin was used to eliminate background HPRT mutations. The medium was changed after the treatment phase, the cells were allowed to express mutant pheno‐types, and then TG was added and resistant mutant clones counted after 16 days. The background MF level for controls and for cells treated with EMS alone were negligible at 5.12 × 10−8 and 7.25 × 10−8, respectively. In the cells treated with morphine alone or morphine plus EMS, MF levels increased very significantly (P < .001) by >100‐fold to 5.1 × 10−6 and 7.0 × 10−6, respectively. Cloning efficiency also decreased significantly with both morphine‐exposed conditions. Preliminary analysis with the single strand conformational polymorphism (SSCP) procedure following 6‐thioguanine (TG) selection, also confirmed the occurrence of Exon 3 mutants of the HPRT gene in cells exposed to morphine plus EMS. It appears that brief EMS exposure can be repaired, whereas, if morphine exposure persists through one or more cell cycles, direct or indirect mutagenesis is initiated. © 1994 Wiley‐Liss, Inc.
Comparative mutagenicity of plant‐activated aromatic amines using salmonella strains with different acetyltransferase activities
Authors: Wagner Elizabeth D. , Smith Shannon R. , Xin Hua , Plewa Michael J.
Published: February 2007

Plant systems can activate aromatic amines into mutagens. In the plant cell/microbe coincubation assay, we earlier demonstrated that 2‐aminofluorene and m‐phenylenediamine were activated by plant cells into mutagens with reversion at the hisD3052 allele in Salmonella typhimurium strain TA98 as the genetic endpoint. New derivatives have been developed which possess elevated levels of acetyl‐CoA:N‐hydroxyarylamine O‐acetyltransferase which are very sensitive to N‐hydroxylated amines [Watanabe et al., 1990: Mutat Res 234:337‐348]. The objectives of this research were to examine Salmonella strains with different acetyltransferase activities in the plant cell/microbe coincubation assay with a series of structurally related aromatic amines. The hypothesis tested was whether and to what degree a plant‐activated metabolite of these aromatic amines could serve as a substrate for bacterial O‐acetyltransferase and induce mutation in Salmonella. Every aromatic amine examined was activated by plant cells with YG1024 (the strain with elevated O‐acetyltransferase activity) as the genetic indicator organism. The rank order of the mutagenic responses of YG1024 to the plant‐activated aromatic amines was 2‐aminofluorene >benzidine > m‐phenylenediamine > 4‐aminobiphenyl > 2,4‐diaminotoluene > 2‐naphthylamine. This rank order was expressed by TA98 but to a much lower degree. There was a very slight mutagenic response observed in TA98/1,8‐DNP6 (a strain lacking O‐acetyltransferase activity) with the plant‐activated metabolites of benzidine and 4‐aminobiphenyl. We conclude that the plant‐activated aromatic amines are substrates for bacterial O‐acetyltransferases. © 1994 Wiley‐Liss, Inc.
Assay by inhibition of repair to measure O6‐methylguanine in DNA
Authors: Mironov Nikolai M. , Martel‐Planche Ghyslaine , Wild Christopher P.
Published: February 2007

A procedure for measuring the level of O6‐me‐thylguanine (O6‐meG) in DNA is described. Repair of 32P‐oligodeoxynucleotides containing O6‐meG adducts by O6‐alkylguanine alkyltransferase (AGT) was performed in the presence of different quantities of DNA containing unknown concentrations of O6‐meG. Each methylated DNA sample inhibited the repair of oli‐godeoxynucleotide substrate to an extent dependent upon O6‐meG concentration. Each DNA sample tested at different concentrations in the assay therefore had a characteristic inhibition curve and could be compared to the curves generated using reference DNA samples of known O6‐meG concentration. We report the method of calculation of the O6‐meG level in a given DNA sample by comparison of its inhibition curve with that of reference DNAs. This method of calculation does not require a knowledge of the exact quantity of the labelled substrate or AGT used. The method requires only 0.1‐10 μg of DNA, with a limit of detection of 0.8 fmol of O6‐meG per μg of DNA. © 1994 Wiley‐Liss, Inc.
Studies on cytotoxic and genotoxic effects of cadmium nitrate and lead nitrate in chinese hamster ovary cells
Authors: Lin Ruey H. , Lee Ching H. , Chen Wen K. , Lin‐Shiau Shoei Y.
Published: February 2007

Cadmium nitrate decreased the viability of Chinese hamster ovary (CHO) cells in a concentration‐dependent manner; 50% inhibition (IC50) was achieved at 0.015 mM. In contrast, lead nitrate appeared to be less toxic. Neither cadmium nitrate nor lead nitrate significantly increased frequencies of binucleated CHO cells with micronuclei (MN). However, both cadmium nitrate and lead nitrate could augment sister chromatid exchanges (SCEs). Cadmium nitrate induced SCEs with a potency approximately equal to that of mitomycin C and more than 10 times higher than lead nitrate. Cadmium nitrate also increased chromosome aberrations (CAs), which included breaks, acentrics, interchanges, and dicentrics of chromosomes. In addition, cadmium nitrate induced a decrease in the mitotic index (MI), but lead nitrate increased it. In summary, it appears that both of these two heavy metal salts have cytogenetic toxicities with different degrees of effects on the cytotoxicity, MN, CAs, and SCEs in CHO cells. However, SCE was the most sensitive endpoint for indicating mutagenetic effects of cadmium and lead in the present study.