bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the co‐carcinogen benzo[e] pyrene on microsome‐mediated chemical mutagenesis in salmonella typhimurium
Authors: Kameswar Rao T. , Young J. A. , Weeks C. E. , Slaga T. J. , Epler J. L.
Published: February 2007

Chemical agents that possess the ability to alter tumorigenicity of carcinogens (administered at subthreshold dose) constitute a major health hazard. We have employed the Ames Salmonella assay to examine the effect of co‐carcinogenic benzo[e] pyrene (B[e]P) on microsome‐mediated chemical mutagenesis. B[e]P enhanced the mutagenic activity induced by 2‐acetylaminofluorene (2‐AAF) and benzo[a] pyrene (B[a]P) in strains TA1538 and TA98. Enhancement was also noted with N‐hydroxy‐2‐AAF (the proximal metabolite of 2‐AAF) but not with an ultimate carcinogenic form (N‐acetoxy‐2‐AAF). These results suggest the use of this approach to detect chemical agents that possess the ability to alter the activity of mutagenic or carcinogenic chemicals.
Problems associated with the application of short‐term tests for mutagenicity in mass‐screening programs
Authors: De Serres Frederick J.
Published: February 2007

During the past ten years we have made a great deal of progress toward the general acceptance of the need for mass‐screening programs to identify environmental chemicals with mutagenic activity. At every meeting of this society new examples are given of mutagens to which substantial portions of the population are exposed. But as a group we are still wrestling with the problem of the development of an effective mechanism for such testing on a still larger scale. It is the problems associated with the development of these mass‐screening programs that I want to bring to your attention this afternoon.
Mutagenicity of nitrosocarbaryl and other methylating nitrosamides as related to uptake in haemophilus influenzae
Authors: Elespuru R. K.
Published: February 2007

Differences greater than 6,000‐fold in the mutagenic potency of three nitro‐samides that are methylating agents [N‐methyl‐N‐nitrosourea (MNU), N‐methyl‐N′‐nitro‐N‐nitrosoguanidine (MNNG) and N‐nitrosocarbaryl (NC)] could be accounted for in part by differences in their uptake into the Haemophilus influenzae cells. Uptake was roughly correlated with the octanol/water partition coefficient. The most potent mutagen, NC, was concentrated by the cells. The least potent, MNU, was essentially excluded from the bacteria. Uptake was a linear function of concentration, whereas induction of novobiocin‐resistant mutations followed higher‐order kinetics. The effective dose of chemical to the bacteria (number of molecules taken up) under conditions of mutagenesis could be calculated.
Bile as a source of mutagenic metabolites produced in vivo and detected by salmonella typhimurium
Authors: Connor T. H. , Cantelli Forti G. , Sitra P. , Legator M. S.
Published: February 2007

The in vivo metabolic activation of several mutagenic compounds was assayed in the bile of rats, with Salmonella typhimurium as the indicator organism. It was determined that for some compounds, particularly the aromatic amines, a substantial percentage of the compound was excreted into the bile as either a nonmutagenic glucuronide conjugate or a mutagenic metabolite of the compound. Relatively low doses of the chemical were detected, and it was possible to follow the excretion pattern of the compounds over the collection period.
Mutagenicity detection of in vivo nitrosation of dimethylamine by nitrite
Authors: Whong Wen‐Zong , Speciner Norman D. , Edwards Gordon S.
Published: February 2007

In vivo nitrosation of dimethylamine by nitrite was measured with an intrahepatic host‐mediated mutagenicity assay using Salmonella typhimurium as the detecting organism. It was possible to detect the product, N‐nitrosodimethylamine, at much lower doses with this system than with previously reported in vivo systems. This and other improvements made it possible to detect the formation of nitrosodimethylamine from relatively low levels of gavaged precursors.
Mutagenicity of organic extracts from canadian drinking water in the salmonella/mammalian‐microsome assay
Authors: Nestmann Earle R. , Lebel Guy L. , Williams David T. , Kowbel David J.
Published: February 2007

Organic extracts of chlorinated Ontario drinking water samples have been found to induce mutation and lethality in the Salmonella/mammalian‐microsome histadine reversion assay. Collections of water were made at water treatment plants in five municipalities in June 1978. To determine the reproducibility of the positive mutagenic effects found, a second sampling at the same plants was performed in September 1978. Preparation of extracts involved passing 200 liter samples through XAD‐2 resin columns which were eluted with a mixture of hexane and acetone, and the eluent was evaporated to dryness. For those extracts with sufficient organic matter, dose‐related increases in mutagenicity were observed. Extracts of untreated water from a river and a well were weakly mutagenic.
Prevention of the mutagenic activation of an antischistosomal isothiocyanate in primates by an antibiotic
Authors: Batzinger Robert P. , Bueding Ernest , Crawford Karen , Bruce John
Published: February 2007

Administration of 4 nitro‐4′ isothiocyano‐diphenylamine (CGP 4540, amoscanate) to two nonhuman primates, Macaca mulatta and Cebus apella, resulted in the appearance of mutagenic material in the urines of these animals. Mutagenic metabolites of this drug could also be detected in the urines when the drug was administered to primates infected with Schistosoma mansoni and Schistosoma japonicum. As observed previously in mice, the mutagenic activation of amoscanate can be prevented in primates by coadministration of a single oral dose of erythromycin with no concomitant reduction in antischistosomal activity. The protective effect of erythromycin was confirmed in several crossover experiments. This dissociation of mutagenic from chemotherapeutic effects provides an opportunity to reduce serious potential long‐term risks of this anti‐schistosomal drug.
Genetic effects of strong magnetic fields in drosophila melanogaster: I. Homogeneous fields ranging from 13,000 to 37,000 gauss
Authors: Kale P. G. , Baum J. W.
Published: February 2007

Drosophila melanogaster males were exposed to homogeneous magnetic fields of intensities of 13,000 to 37,000 Gauss as eggs, larvae, pupae and as adults. Sex linked recessive lethals were scored in chromosomes exposed as spermatozoa, spermatids and as spermatocytes. There was no indication of enhanced mutation induction by the magnetic fields.
In vitro mutagenicity and cell transformation screening of caprolactam
Authors: Greene Elliott J. , Friedman Marvin A. , Sherrod Julie A.
Published: February 2007

Caprolactam was tested for genetic activity in bacterial and mammalian screens. It was inactive in the following tests: a) Salmonella/microsome mutagenicity; b) Chinese hamster ovary cell mutagenicity (induction of 6‐thioguanine mutants); c) Enhancement of SA7 virus transformation of primary hamster embryo cells, when administered before or after virus, and; d) Chemical transformation of secondary hamster embryo cells.
Tissue‐specific induction of sister chromatid exchanges by ethyl carbamate in mice
Authors: Roberts Gladwin T. , Allen James W.
Published: February 2007

Sister chromatid exchange (SCE) techniques were used to analyze the genetic effects of ethyl carbamate (urethane) in cultured mouse‐bone marrow cells, and in several different mouse tissues in vivo. Ethyl carbamate concentrations up to 5.0 mg/ml were ineffective in causing a significant elevation of SCE in vitro. After in vivo drug administration, bone marrow, liver and spermatogonial cells all revealed significant dose‐related increases in SCE. Baseline and relative incremental levels of SCE were somatic vs germ tissue‐specific. Regenerating liver cells exhibited significantly greater absolute SCE values than all other tissues examined. Marrow cells revealed intermediate values, while germ cells were the least sensitive in SCE responsiveness. Spermatogonia required a fourfold higher dose, over that effective in somatic tissues, to promote an approximate doubling of the baseline SCE level.

In vivo SCE analysis affords sensitive risk assessments for different tissues. Thus, this approach should be generally useful for studying compounds with questionable mutagenic potential, and/or those exerting target organ specificities of related biological activity (eg, toxicity, carcinogenesis).
Sister chromatid exchange in vivo in mice: I. The influence of increasing doses of bromodeoxyuridine
Authors: Wilmer James L. , Soares E. R.
Published: February 2007

Bromodeoxyuridine (BrdUrd) pellets weighing either 20, 25, 30, 35, 40, 45, or 53 mg were implanted subcutaneously in strain DBA/2J male mice. Femoral bone marrow cells were analyzed for sister chromatid exchange (SCE) and chromosome aberration frequencies, mitotic indices, and cellular replication kinetics. Small but statistically significant BrdUrd dose‐dependent increases of SCEs were observed, whereas chromosome aberrations were induced at low frequencies and occurred independently of BrdUrd dose. The mitotic index remained relatively constant for all doses. A slight inhibition of cellular replication, as manifested by a reduction in third division cells at the 40‐ and 45‐mg doses, was observed. The use of an intense fluorescent light source in the fluorescence‐plus‐Giemsa technique provided consistently good sister chromatid differentiation at pellet doses substantially lower than those previously used by other investigators.
Lack of an indication of mutagenic effects of dinitrotoluenes and diaminotoluenes in mice
Authors: Soares E. R. , Lock L. F.
Published: February 2007

The mutagenic effects of 2,4‐dinitrotoluene (2,4‐DNT), purified and technical grades, 3,5‐DNT, 2,4‐diaminotoluene (2,4‐DAT), and 2,5‐DAT were tested in mice using one or more of the following: the dominant lethal assay, the sperm morphology test and/or the recessive spot test. Compounds were administered by both intraperitoneal (IP) injection and gavage, and comparisons were made between controls and treated groups as well as between routes of administration. None of the five compounds tested produced a significant response in any of the systems employed. Treatment with purified 2,4‐DNT and 3,5‐DNT resulted in marked reductions in the percent of fertile matings. These data indicate a lack of mutagenicity of these compounds in the test systems employed here. The observed fertility effects are consistent with previously published data on DNT‐induced testicular damage.
The mutagenic effect of platinum compounds in drosophila melanogaster
Authors: Woodruff R. C. , Valencia R. , Lyman R. F. , Earle B. A. , Boyce J. T.
Published: February 2007

The platinum compounds cis‐platinum (II) diamminodichloride (cis‐PDD) (an anti‐tumor agent) and platinum tetrachloride (Pt Cl4) induce a significant increase in recessive sex‐linked lethal mutations in Drosophila melanogaster male germ cells in different developmental stages.
Enzyme mutants induced by low‐dose‐rate γ‐irradiation in drosophila: Frequency and characterization
Authors: Racine Robert R. , Langley Charles H. , Voelker Robert A.
Published: February 2007

One thousand lines of a balanced lethal strain of Drosophila melanogaster heterozygous at seven allozyme loci were subjected to chronic (0.15 rad/min) γ‐irradiation (137 Cs). After 15 generations of exposure they were screened by gel electrophoresis for newly arisen null mutants and/or mobility variants. Seven independent nulls were recovered. 1) None were associated with a cyto‐genetically detectable aberration; 2) one of six analyzed was associated with recessive lethality, suggesting association with a submicroscopic interlocus deficiency; 3) three of five which could be analyzed for cross‐reacting material (CRM) production were CRM‐positive; and 4) two of six produced an active heterodimer with an active normal allele. The results taken together suggest that most of the mutations are point mutations rather than small deficiencies.
Evidence that the repair deficient mei‐9a female in drosophila melanogaster is a strong potentiator of chromosome loss induced in the paternal genome by dimethyinitrosamine
Authors: Zimmering S. , Hartmann A. W. , Cooper S. F.
Published: February 2007

From matings of Xc2/BsYy+ males treated or not with 2.5 mM DMN (dimethylnitrosamine) with repair‐deficient mei‐9a females or with ordinary females, induced frequencies of observed (recovered) chromosome loss were 3.69% and 0.65% and inferred (non‐recovered) ring‐X loss based on shifts in sex ratio (♀♀/♂♂) was 47.9% and 9.4%, respectively. Results indicate that the mei‐9a female is a strong potentiator of DMN‐induced chromosome damage in sperm and suggest that DMN‐induced chromosome lesions are produced in substantially higher frequency in treated sperm than deducible after crosses with repair‐efficient females.
The action of three anticlastogens on the induction of sister chromatid exchange by trenimon and 8‐hydroxyquinoline sulfate in human lymphocyte cultures
Authors: Gebhart E. , Kappauf H.
Published: February 2007

The influence of the anticlastogens β‐aminoethylisothiouronium (AET), d,1‐homocysteinethiolactone (HCT), and 1‐cysteine (CYS) on the frequency of sister chromatid exchanges (SCEs) induced by the chromosome damaging chemicals Trenimon and 8‐hydroxyquinoline sulfate (8‐HQS), was investigated in human lymphocyte cultures. None of the anticlastogens significantly influenced the SCE rate, whereas in the same or previous experiments the chromosome‐breaking effect of these clastogens was distinctly reduced by the anticlastogens. These results suggest that the sites of anticlastogenic activity do not coincide with the sites of SCE formation. SCE analysis, although it yields interesting and important information about the action of chemicals on genetic material, cannot replace classical aberration analysis, because the two parameters apparently reflect different patterns of molecular and cytogenetic activity of mutagens.
Variation in the baseline sister chromatid exchange frequency in human lymphocytes
Authors: Carrano A. V. , Minkler J. L. , Stetka D. G. , Moore D. H.
Published: February 2007

The utility of the sister chromatid exchange (SCE) assay for human population studies is potentially limited by the variability associated with individual baseline SCE frequencies. This investigation identifies and quantifies the major sources of preparative and biological variation associated with the determination of baseline SCE frequencies in cultured human lymphocytes. Much of the variation in lymphocyte SCE frequencies is attributable to the amount of bromodeoxyuridine (BrdUrd) available per lymphocyte; the pooled coefficient of variation (CV) over the dose range of 10 to 160 μM is about 18%. Other variations in the baseline frequency result from culture‐to‐culture and slide‐to‐slide differences. The pooled coefficient of variation among donors is about 10%. The effect of cell‐to‐cell differences in baseline SCE frequency among donors can be minimized by increasing the number of cells scored per donor. When 20 cells are analyzed per individual the pooled cell‐to‐cell variation is 9% but when 40 or 80 cells are analyzed it is reduced to 6 and 4% respectively. For a single individual the cell‐to‐cell coefficient of variation at 100 μM BrdUrd is 40.8%. Under our experimental conditions, a 30% increase in SCE frequency between two cohort populations can be detected with a 95% probability at a 5% level of significance when 11 individuals per cohort are studied. For a longitudinal or in vitro dose response study of a single individual, a 50% increase in SCE frequency can be detected with a 95% probability at a 5% level of significance when 25 cells per sample are analyzed. These results indicate the feasibility of applying the SCE bioassay to humans as a measure of environmental stress.
The anaerobe‐mediated mutagenicity of 2‐nitrofluorene and 2‐aminofluorene for salmonella typhimurium
Authors: Karpinsky George E. , Rosenkranz Herbert S.
Published: February 2007

Anaerobic bacteria (Bacteroides fragilis, B vulgatus, and B thetaiotaomicron) possess the enzymic ability to convert 2‐nitrofluorene and 2‐aminofluorene to substances mutagenic for Salmonella typhimurium. If it be assumed that the active intermediate for both chemicals is 2‐hydroxylaminofluorene, then these bacteria possess reductive as well as oxidative capabilities.
Differential induction of sister chromatid exchanges by indirect‐acting mutagen‐carcinogens at early and late stages of embryonic development
Authors: Todd Lori A. , Bloom Stephen E.
Published: February 2007

To examine the development of drug‐metabolizing enzyme systems in the early chick embryo, the procarcinogens, aflatoxin B1 (AF‐B1) and 2‐acetylamino‐fluorene (2‐AAF), and the direct‐acting carcinogen, ethyl methanesulfonate (EMS) (positive control), were given to embryos; the sister‐chromatid‐exchange (SCE) technique was used as an indicator of conversion to active mutagenic metabolities. Chick embryos at two stages of incubation (3‐day and 6‐day) were exposed to the same graded series of dosages of the compounds for a period of 22 hours. All three mutagens increased the frequency of SCE above the control rate of 1.8 SCEs/cell. While a dose‐dependent increase in SCE was obtained for both procarcinogens at each age, the mean SCE frequency was significantly higher in the 6‐day embryos for each dosage given. In contrast, the direct‐acting mutagen, EMS, gave a reduced level of SCEs at the older age. These results suggest that the ability of early chick embryos to activate promutagens to forms capable of inducing SCE increases as development advances from three to six days of incubation (DI). In the 6‐day embryo, the metabolic conversion is enhanced, resulting in a significant increase in the mutagenicity of the test chemicals.
How many loci on the X‐chromosome of drosophila melanogaster can mutate to recessive lethals?
Authors: Abrahamson S. , Würgler F. E. , Dejongh C. , Meyer H. Unger
Published: February 2007

The sensitivity of the sex‐linked recessive lethal test is due to the fact that a very large number of loci are included in the mutation study. From extensive studies on the spontaneous sex‐linked recessive lethal frequency and spontaneous specific locus mutation rates, it is possible to derive an estimate of the number of loci included in the recessive lethal test. The average number derived from three estimates on male and female germ cells is 563 loci. A second independent approach derives from published data which analyzed short regions of the genome and the proportion of loci within these regions which mutate to lethality. This analysis suggests that 830 loci are potentially lethal mutables. We describe the reasons for concluding that 600 to 800 loci of the approximately 1,000 loci on the X‐chromosome are involved in the X‐linked recessive lethal test.
Short‐term cytogenetic assays of nine cancer chemotherapeutic drugs with metabolic activation
Authors: Au William W. , Johnston Dennis A. , Collie‐Bruyere Cheryl , Hsu T. C.
Published: February 2007

Nine anticancer drugs were analyzed in cell cultures with respect to their cytogenetic effects with or without the addition of liver fraction S9 as an in vitro metabolic system. Among them, vincristine was the only drug which induced a significant accumulation of mitosis with or without S9. Adriamycin and neocarzinostatin were most potent in induction of chromosome breakage, but their clastogenic activities were reduced after metabolic conversion. On the other hand, cyclophosphamide had a dose‐dependent activation of clastogenic effect by S9. The activity of bleomycin was enhanced by S9. S9 had no effect on the activities of actinomycin D, cytosine arabinoside, mitomycin C, and methotrexate. Vincristine showed no clastogenic property in our short‐term assay system with or without S9.

The activities of these anticancer drugs observed from our assay were compatible with those from other assay systems. The incorporation of S9 or other metabolic systems in routine clastogen assays should allow us to improve our understanding of the genetic toxicity of chemical agents.
The relative contributions of B and T lymphocytes in the human peripheral blood mutagen test system as determined by cell survival, mitogenic stimulation, and induction of chromosome aberrations by radiation
Authors: Schwartz Jeffrey L. , Gautden Mary Esther
Published: February 2007

Ficoll‐Hypaque‐separated subpopulations of human peripheral blood T and B lymphocytes were exposed to 0, 0.5, 1.0, 2.5, or 5.0 Gy of γ rays. Three parameters were examined: Survival, as measured by trypan blue dye exclusion in unstimulated cultures five days after irradiation; mitotic index, measured in phytohemagglutinin (PHA)‐stimulated cultures 48 and 72 hours after irradiation; and chromosome aberration frequency, measured 48 or 60 hours after irradiation.

Survival curves of T, B, and null cells are biphasic; the D0 values for the radiosensitive populations of all three cell types are close to 0.6 Gy but are different for the radioresistant populations: 2.7 Gy for B cells, 4.77 Gy for T cells, and 6.03 Gy for null cells. B cells, as well as T cells, are stimulated to divide by PHA, and B cells comprise at least 10% of the mitotic figures seen in unirradiated cultures at 48 hours. The proportion of B lymphocytes in mitosis at any particular time after PHA stimulation decreases with increasing radiation dose, which reflects a higher mitotic radiosensitivity of B than of T cells. No significant difference, however, in chromosome aberration frequency was found between T and B cells.
Potentiation of chromosome loss induced in the paternal genome by methyl methanesulfonate and procarbazine following matings with repair deficient mei‐9a females of drosophila
Authors: Zimmering S. , Kammermeyer K. L.
Published: February 2007

Drosophila melanogaster males carrying a ring‐X (Xc2) and a doubly‐marked Y chromosome (BSYy+) were treated with methylmethane sulfonate (MMS) and procarbazine, and mated with repair‐deficient mei‐9a females or ordinary repair‐proficient females. Observed (recovered) chromosome loss were scored and nonrecovered inferred. Ring‐X loss based on shifts in sex ratio were noted. Results indicate that the mei‐9a female is a strong potentiator of chromosome loss induced by MMS and procarbazine in line with the effect recently shown for dimethylnitrosamine (DMN)‐induced chromosome lesions (Zimmering, et al 1980.
A maternal effect in homozygous mei‐9amei‐41D5 repair deficient drosophila melanogaster females influencing the recovery rate of progeny bearing a Y chromosome
Authors: Zimmering S. , Cooper S. F.
Published: February 2007

Evidence is presented supporting the suggestion that homozygosity for the repair‐deficient mutants mei‐9a mei‐41D5 is associated with a maternal effect which affects detrimentally the recovery rate of Y chromosome‐bearing offspring.
Sensitivity of drosophila melanogaster to low concentrations of gaseous mutagens: III. Dose‐rate effects
Authors: Kale P. G. , Baum J. W.
Published: February 2007

Sex‐linked recessive lethal mutations were induced in D melanogaster males by chronic as well as acute treatments of gaseous 1, 2‐dibromoethane ranging from 2.3 to 31 ppm.hr. Acute treatments corresponding to each chronic treatment were made by increasing chemical concentration approximately 30 times with a concomittant decrease in exposure period. Germ cell stages sampled, in order of decreasing sensitivity, were spermatocytes, spermatids, and spermatozoa. The most significant finding is that no consistent pattern of difference is observed between acute and chronic exposure for three of the four exposure levels. Only at the highest exposure level (30–31 ppm.hr) was any consistent difference observed between chronic and acute exposure levels. At the higher exposure level in all three germ cell stages the acute exposure showed a significant increase in mutation frequency over the chronic exposure. The greater acute vs chronic mutation frequency for spermatozoa, a metabolically inactive cell stage, leads to the conclusion that the exposure rate effect at high exposure levels is due to systemic factors such as metabolic deactivation or elimination rather than repair of premutational damage in the target cells. The significance of these observations in risk assessment for environmental pollutants is discussed.
Metabolic activation of carcinogens in the salmonella mutagenicity assay by hamster and rat liver S‐9 preparations
Authors: Raineri Ronald , Poiley Judith A. , Pienta Roman J. , Andrews A. W.
Published: February 2007

Before exerting a carcinogenic or mutagenic effect, many carcinogens must undergo metabolic activation. Liver S‐9 preparations from rats treated with Aroclor 1254 (AC) have been widely used to extend the ability of the Salmonella mutagenicity assay to detect such nondirect‐acting agents. We compared the mutagen‐activating capabilities of liver S‐9 preparations from both Syrian golden hamsters and Sprague‐Dawley rats. The comparison was made between S‐9 fractions from untreated, and phenobarbital (PB)‐ and AC‐treated animals of both sexes. Also compared was the effect of varying the amount of S‐9 protein. The preparations from hamster liver were consistently more effective than preparations from rat liver for the activation of 2‐acetylaminofluorene (AAF), 2‐aminoanthracene (AA) (except for AC‐induced preparations), 3‐methylcholanthrene (MCA), and diethylnitrosamine (DEN) to their mutagenic forms. Induced preparations from rats were more active than those from hamsters when using benzo(a)pyrene (BP), while with uninduced preparations, the opposite was true.

There was also a relationship between the amount of S‐9 protein and the number of revertant colonies obtained. With the aromatic amines (AAF and AA), a partial inhibition of mutagenicity occurred at the highest protein concentrations tested. With BP, an inverse relationship was observed between protein concentration and the number of revertants occurring in the presence of the preparation from PB‐ and AC‐induced male and female rats.

The relative order of activities of aryl hydrocarbon hydroxylase (AHH) and BP‐4,5‐epoxide hydrase (EH) in the preparations was AC‐induced > PB‐.
A standardized procedure for quantification of the ames salmonella/mammalian‐microsome mutagenicity test
Authors: Belser William L. , Shaffer Steven D. , Bliss Richard D. , Hynds Paul M. , Yamamoto Lynn , Pitts James N. , Winer Judy A.
Published: February 2007

Factors determining the precision and variability of the Ames Salmonella test for mutagenicity were investigated. The most important source of variability in the agar‐overlay method was nonuniformity in the soft‐agar layer thickness. Solution of this problem resulted from application of an agar‐leveling table described in this paper. Several other procedural elements also contribute to improved precision, including temperature uniformity during incubation, incubation interval, consistency of plate agar volume, completeness of mixing the soft‐agar overlay, peculiarities in the interaction of mutagens and mammalian liver microsomal extract (S9), and methods of storage and controls for tester strains. When these and other effects were well‐controlled, variability of the test results was reduced from 200 or 300% to only ± 10% or less. The significance of the factors affecting precision are discussed and an improved experimental protocol is presented.
Stability of activating systems for in vitro mutagenesis assays: Enzyme activity and activating ability following long‐term storage at ‐ 85°c
Authors: Dent John G. , Schnell Stephanie , Graichen M. Elizabeth , Allen Paula , Abernethy Diane , Couch David B.
Published: February 2007

Activating systems for in vitro mutagenesis assays are commonly prepared and stored at low temperature until required. The objective of the studies reported here was to determine the long‐term stability of activating systems stored at ‐ 85°C. A broad range of microsomal enzymes in the postmitochondrial supernatant (PMS) and the microsomal fraction of livers from Aroclor 1254 treated rats were studied in conjunction with the ability of these fractions to catalyse the conversion of dimethylnitrosamine (DMN) and benzo(a)pyrene (B(a)P) to products mutagenic to Chinese hamster ovary (CHO) cells and Salmonella typhimurium TM677. Biphenyl‐2‐ and biphyeny 1‐4‐hydroxylase showed a rapid decline in activity on storage, epoxide hydratase activity increased with storage and other enzyme activities studied were relatively stable for up to 32 weeks. No consistent trends in the ability of either the microsomes or the PMS to catalyze DMN or B(a)P induced mutation were observed for up to 12 weeks with CHO cells and 24 weeks with bacteria. It is concluded that low temperature storage of activating systems is an acceptable procedure. However, the results also indicate that certain enzyme activities change during storage, suggesting that aberrant results may be obtained when stored activiating systems are used in in vitro tests to screen for mutagens.
Mutagenicities of 61 flavonoids and 11 related compounds
Authors: Nagao Minako , Morita Naokata , Yahagi Takie , Shimizu Mineo , Kuroyanagi Masanori , Fukuoka Masamichi , Yoshihira Kunitoshi , Natori Shinsaku , Fujino Tadahiko , Sugimura Takashi
Published: February 2007

The mutagenicities of 61 flavonoids (naturally occurring flavonoid aglycones and flavonal glycosides and synthetic flavonoids) and those of 11 compounds structurally related to flavonoids were tested with Salmonella typhimurium strains TA100 and TA98. Among the 22 flavone derivatives tested, only wogonin was strongly mutagenic, while five derivatives, apigenin triacetate, acacetin, chrysoeriol, pedalitin, and pedalitin tetraacetate, were only weakly mutagenic. Two bisflavonyl derivatives, neither of which has a 3‐hydroxyl group, were not mutagenic. Of the 16 flavonol derivatives tested, all except 3‐hydroxyflavone and the tetra‐ and penta‐methyl ethers of quercetin were mutagenic. Of the five flavanone derivatives tested, only 7,4‐dihydroxyflavanone was mutagenic, showing weak activity. Of the four flavanonol derivatives tested, hydrorobinetin and taxifolin were weakly mutagenic. Of the six isoflavone derivatives tested, tectorigenin was weakly mutagenic. Of the 11 compounds in the miscellaneous group structurally related to flavonoids, only iso‐liquiritigenin was mutagenic, showing weak activity. For the emergence of strong mutagenicity, the double bond between positions 2 and 3 and the hydroxyl group at position 3 are required, except in wogonin, which does not have a hydroxyl group at position 3 but is strongly mutagenic to TA100. The 3‐O‐acetyl ester of flavonol, quercetin, was mutagenic with S9 mix, but 3‐O‐methyl ethers were not. Six flavonol glycosides, three quercetin glycosides and three kaempferol glycosides were mutagenic after preincubation with “hesperidinase,” a crude extract of Aspergillus niger. Of 66 flavonoid agylcones and compounds structurally related to flavonoids, quercetin was the strongest mutagen. The carcinogenicity of this compound should be clarified because it is ubiquitously found in vegetables.
Evidence for the existence of a family of bacterial nitroreductases capable of activating nitrated polycyclics to mutagens
Authors: McCoy Elena C. , Rosenkranz Herbert S. , Mermelstein Robert
Published: February 2007

A derivative of Salmonella typhimurium TA98 which does not respond to the potent mutagenicity of 1,8‐dinitropyrene is described. This novel strain also shows a lack of response to the mutagenic action of 1,3‐dinitropyrene and a greatly reduced response to 1,6‐dinitropyrene and 1‐nitropyrene. The responses to 1,3,6‐trinitropyrene and 1,3,6,8‐tetranitropyrene are affected to a much lesser extent. This strain (TA98/1,8DNP6) is fully sensitive to the mutagenicity of 4‐nitroquinoline‐1‐oxide, niridazole, nitroacridine, and nonnitrated frameshift mutagens. This strain appears to be deficient in a nitroreductase which reduces nitrated pyrenes and possibly other nitrated polycyclic aromatic hydrocarbons to corresponding hydroxylamines, the penultimate mutagens.
An E coli microsuspension assay for the detection of DNA damage induced by direct‐acting agents and promutagens
Authors: McCarroll N. E. , Piper C. E. , Keech B. H.
Published: February 2007

We have devised a microsuspension assay utilizing E coli indicator strains WP2, WP2 uvrA, WP67, CM611, WP100, W3110 polA+, and p3478 pola‐ for the detection of chemically‐induced preferential kill of repair‐deficient strains. Data are presented from tests of 77 compounds representing a wide range of chemical classes which demonstrate the efficiency of the E coli microsuspension assay as both a qualitative and quantitative screen of DNA‐modifying activity. Furthermore, the use of a battery of indicator strains lacking different repair systems offers the advantage of providing preliminary information concerning the mechanism of DNA damage induction by a test agent.
An examination of the quantitative suspension assay for mutagenesis with strains of salmonella typhimurium
Authors: Thompson E. D. , Melampy P. J.
Published: February 2007

The effects of cell toxicity on the mutagenic response obtained in a quantitative suspension assay using the strains of Salmonella typhimurium developed by Ames et al [Mutat Res 31:347–364, 1975] were examined. Cell toxicity was shown to produce false‐positive results when the cells were plated immediately with trace amounts of histidine in the overlay agar. Replacement of the overlay agar with one lacking histidine produced false‐negative results when the cells were plated immediately after exposure to a frame‐shift‐type mutagen. The inclusion of an overnight growth period in brain‐heart infusion broth before plating the cells on minimal medium permitted incorporation of mutations into the genome and also yielded constant titers. The addition of the regrowth period is shown to be necessary for obtaining valid results in a suspension assay.
Structural basis of the mutagenicity in bacteria of nitrated naphthalene and derivatives
Authors: McCoy Elena C. , Rosenkranz E. Joshua , Petrullo Lynn A. , Rosenkranz Herbert S. , Mermelstein Robert
Published: February 2007

While 2‐nitronaphthalene was a weak direct‐acting base‐substitution mutagen (1.4 revertants/nanomole) for Salmonella typhimurium, the analogous nitronaphthalic acid anhydride and imides were moderate frameshift mutagens (∼20 rev/nanomole in strain TA98). Although imide derivatives are efficient DNA intercalators, mutagenicity data indicate that the bulk of the frameshift activity is derived from adduct formation between hydroxylamine intermediates and DNA. The low level of frameshift activity (∼8% of total) resulting from simple intercalation (measured in strain TA1537) is not dependent upon reduction of the nitro function.

Evidence is presented that suggests that the reduction of the nitro function to the corresponding hydroylamine might not involve a free nitroso intermediate.

The introduction of a second nitrofunction into nitronaphthalenes results in great positional effects of the various isomers on mutagenic activity and specificity.
Chromosome changes in human lymphocytes after separate and combined treatment with divalent salts of lead, cadmium, and zinc
Authors: Gasiorek K. , Bauchinger M.
Published: February 2007

Unstimulated human lymphocytes in whole blood were treated for three hours with lead, cadmium, and zinc acetate separately and in combinations of two or three metal salts with different concentrations of between 10−3 and 10−8 moles, respectively. Untreated cultures and sodium acetate‐treated samples served as controls. Chromosome analysis from 48 cultures revealed higher incidences of chromatid‐type aberrations and gaps only for cultures exclusively treated with cadmium. The results are discussed under the aspect of heavy metal metabolism in human lymphocytes.
Mutagenicity of municipal water obtained from an agricultural area
Authors: Heartlein M. W. , Demarini D. M. , Katz A. J. , Brockman H. E. , Means J. C. , Plewa M. J.
Published: February 2007

We have studied the mutagenicity of the water from Lake Bloomington and of the tap water that is made from the lake water. The lake, which is the source of drinking water for Bloomington, Illinois (pop. 44,000), is surrounded by land that is farmed intensively ‐ being mainly in maize and soybeans. Samples were collected monthly from May through October 1979 and concentrated 3,000× with XAD‐2 resin. Nearly all of the lake and tap water concentrates were mutagenic in Salmonella typhimurium TA98 and TA100 in the presence of S‐9 mix, and the May tap water concentrate was highly mutagenic. In addition, many of the concentrates were toxic to the bacteria in the absence of S‐9 mix. Chemical analysis of the highly mutagenic tap water concentrate from May revealed the presence of a number of organic contaminants that were absent from control concentrates prepared from deionized and distilled treated well water. In addition, unconcentrated lake and tap water were tested in a reverse‐mutation test in maize (Zea mays); no mutagenicity was detected. This study indicates that the contamination of drinking water with agricultural and/or industrial chemicals may result in a potential health hazard.
Characterization of a rat lymphocyte culture system for assessing sister chromatid exchange after in vivo exposure to genotoxic agents
Authors: Kligerman A. D. , Wilmer J. L. , Erexson G. L.
Published: February 2007

Lymphocyte culture systems have the major advantage of permitting the analyssis of in vivo cytogenetic damage with minimal injury to the animal under study. This paper describes a rat lymphocyte culture system designed for the study of sister chromatid exchange (SCE) induced by in vivo exposure to genotoxic agents. A standard protocol was established in which 1 to 2 ml of blood are removed from rats by cardiac puncture, washed three times with phosphate‐buffered saline (pH 7.4), and grown in RPMI 1640. 5‐Bromodeoxyuridine (BrdU) (1.0 μM) is added after 24 hr, and cells are harvested after 56 hr of culture. Critical steps for successful blast transformation include washing the blood in buffered saline and the adding of 2.0 to 4.0 μg phytohemagglutinin/ml to the culture medium. The use of low concentrations of BrdU (≤5.0 μM) is recommended to maintain low baseline SCE levels and to avoid cytotoxicity. The mutagenic carcinogen, ethyl methanesulfonate (EMS), was used as a positive control agent and at a dose of 300 mg/kg caused a fourfold increase in SCE frequency. Twenty‐eight days after EMS administration (30, 100, 300 mg/kg), lymphocytes from treated animals still displayed SCE levels at least 50% above baseline. This system provides a reliable means of investigating chemically induced SCE in the rat.
Radiosterilization of rat liver microsome containing postmitochondrial supernatant for mutation assays
Authors: Barfknecht Thomas R. , Andon Barbara M. , Bishop Walter W. , Thilly William G.
Published: February 2007

Gamma‐irradiation was effectively employed to sterilize rat liver postmito‐chondrial supernant (PMS), which is required for the metabolic activation of soots and soot‐derived polycyclic aromatic hydrocarbons to mutagens. When a known number of Bacillus subtilis spores were added to the PMS and gammairradiated at −80° C, a 2‐Mrad dose resulted in a 7.5 log kill of the spores. A dose of 3 Mrads was selected as a sufficient effective sterilizing dose and had no significant effect upon the ability of gamma‐irradiated PMS to metabolically activate diesel soot and two diesel soot components, benzo(a)pyrene and fluoranthene to mutagens in a Salmonella typhimurium 8‐azaguanine resistance forward mutation assay. Three Mrads of gamma‐irradiation also had no effect upon the ability of PMS to activate benzo[a]pyrene to a mutagen for the human lymphoblasts. However, gamma‐irradiation did reduce the ability of PMS to activate dimethylnitrosamine to a mutagen for S typhimurium.
Regression analysis of ames test data
Authors: Myers Lawrence E. , Sexton Nancy H. , Southerland Leslie I. , Wolff Thomas J.
Published: February 2007

Weighted least squares estimation is used for fitting nonlinear models to Ames test data. The models are biologically plausible, incorporating mutagenicity, toxicity, and/or saturation. Regressions are weighted to compensate for variance that changes with mean and to attain outlier resistance.
Comparison of the genetic activity of AF‐2 and nitrofurantoin in log and stationary phase cells of saccharomyces cerevisiae
Authors: Callen D. F.
Published: February 2007

The effects of nitrofurantoin and AF‐2 in stationary phase cells were compared with the effects in log phase cells. The Saccharomyces cerevisiae diploid strain D7 was used. This strain can be used to monitor lethality, gene conversion, mitotic gene recombination, and reversion. Stationary phase cells were not sensitive to nitrofurantoin, but treatment of log phase cells did result in the induction of lethality and gene conversion. Log phase cells were approximately 10 times more sensitive to the lethal effects of AF‐2 than were stationary phase cells. The AF‐2 induced increase in frequencies of gene conversion and mitotic recombination per surviving cell were similar in both log and stationary phase cells. Gene reversion was induced by AF‐2 in stationary cells, but no revertants were induced in log cells. Measurement of nitroreductase activity gave values for log phase cells which were five to sixfold greater than for stationary phase cells. The increased sensitivity of log phase cells to nitrofurans could therefore be in part due to an increased activation of these compounds. It is concluded that the use of log phase cells is optimal for the detection of induced gene conversion and recombination by nitro compounds.
Uptake and mutagenicity of AF‐2 in chinese hamster V‐79 spheroids under aerobic and hypoxic conditions
Authors: Olive Peggy L. , Durand Ralph E.
Published: February 2007

Chinese hamster V‐79 cells, when grown in suspension culture as multicell spheroids, display many of the features of organized tissue. AF‐2, a known mutagen, was used to examine the influence of some of these factors on mutagenesis. Since AF‐2 is fluorescent, FCM quantitation of intracellular drug content was performed after incubation of spheroids under either aerobic or hypoxic conditions. For the same level of toxicity, hypoxic spheroids accumulated twice as much AF‐2 as aerobic spheroids, but showed less than half the number of mutants resistant to 6‐thioguanine. Using velocity sedimentation techniques, a selective increase in the toxic and mutagenic effects of AF‐2 was found for internal vs external cells of the spheroids. However, in mutagenicity experiments using all the cells from spheroids, the response of the external cycling cells predominated over the response of the internal cells. Thus, in addition to the demonstration that cellular environment can modify mutagenesis, these results also suggest that the growth fraction of the target cells can be an important consideration in mutation experiments.
Mutagenicity and toxicity of aflatoxin precursors
Authors: Dunn J. J. , Lee L. S. , Ciegler A.
Published: February 2007

The Salmonella/microsome test and the chick embryo test were used to determine the mutagenicity and toxicity of five aflatoxin B1 precursors. A definite pattern emerges: the nearer to B1 an intermediate appears in the biosynthetic pathway, the more potent is its mutagenicity and toxicity.
The effect of bleomycin on DNA synthesis in ataxia telangiectasia lymphoid cells
Authors: Cohen Maimon M. , Simpson Stacy J.
Published: February 2007

Bleomycin, a radiomimetic glycopeptide, inhibits de novo DNA synthesis in ataxia telangiectasia lymphoblastoid B cells to a markedly lesser extent than in normal and xeroderma pigmentosum lymphoid cells. This observaton is similar to that following ionizing radiation; however, the effect is slower following the chemical treatment. Recovery of the normal cells occurs 15–18 hours after treatment, whereas the ataxia telangiectasia lines do not attain normal levels of DNA synthesis during the entire 24‐hour observation period. Similar differences were not observed following treatment with mitomycin C, a bifunctional alkylating agent, indicating a specific effect of bleomycin on DNA synthesis in ataxia telangiectasia cells. Following bleomycin treatment and preincubation with hydroxyurea, residual DNA synthesis in ataxia telangiectasia cells was similar to that in both normal and xeroderma pigmentosum lymphoid lines, suggesting that the capacity to repair the induced DNA lesion is present.
The use of primary rat hepatocytes to achieve metabolic activation of promutagens in the chinese hamster ovary/hypoxanthine‐guanine phosphoribosyl transferase mutational assay
Authors: Bermudez Edilberto , Couch David B. , Tillery Deborah
Published: February 2007

A method is described in which primary rat hepatocytes have been cocultured with Chinese hamster ovary (CHO) cells to provide metabolic activation of promutagens in the Chinese hamster ovary/hypoxanthine‐guanine phosphoribosyl transferase (CHO/HGPRT) mutational assay. Single cell hepatocyte suspensions were prepared from male Fischer‐344 rats using the in situ collagenase perfusion technique. Hepatocytes were allowed to attach for 1.5 hours in tissue culture dishes containing an approximately equal number of CHO cells in log growth. The cocultures were exposed to promutagens for up to 20 hours in serum‐free medium. The survival and 6‐thioguanine‐resistant fraction of treated CHO cells were then determined as in the standard CHO/HGPRT assay. Aflatoxin B1 (AFB1) 7,12‐dimethylbenz(a)anthracene (DMBA) and benzo(a)pyrene (B(a)P) were found to produce increases in the mutant fractions of treated CHO cells as a function of concentration. The time required for optimum expression of the mutant phenotype following exposure to DMBA and AFB1 was approximately 8 days. Primary cell‐mediated mutagenesis may be useful in elucidating metabolic pathways important in the production and detoxification of genotoxic products in vivo.
Mutagenic activity of sterilization indicators
Authors: Atherholt Thomas B. , McGarrity Gerard J. , Louis Judith
Published: February 2007

Using the Ames Salmonella/microsomal assay, mutagens were detected in acetone‐methylene chloride extracts of black threads on glass tube‐type sterilization indicators used in hospitals and research laboratories. Extracts of samples of commercially available black thread also contained mutagenic substances. Fluids autoclaved with these sterilization indicators may alter the results in mutagenicity and other studies.
Morphological transformation of C3H/10T1/2 CL8 cells by procarcinogens
Authors: Oshiro Y. , Balwierz P. S.
Published: February 2007

In order to increase the sensitivity of the C3H/10T1/2 CL8 (10T1/2) cell transformation system, we increased the chemical exposure period to a total of 6 days (two consecutive 3‐day exposures). Using this modified procedure, we transformed 10T1/2 cells with procarcinogens such as aflatoxin B1, benz(a)anthracene, and 4‐nitroquinoline‐1‐oxide which have been negative in the standard 10T1/2 cell transformation assay. However, β‐naphthylamine was inconclusive and 2‐acetylamino‐fluorine was negative in this modified assay system. Our results demonstrate that a simple modification of the 10T1/2 cell transformation method can increase the sensitivity to some procarcinogens that require metabolic activation.