bluuebunny/crossref_metadata_2025 huggingface dataset:
Sister chromatid exchange response of human diploid fibroblasts and chinese hamster ovary cells to dimethylnitrosamine and benzo(a)pyrene
Authors: Tomkins Darrell J. , Kwok S. Emily , Douglas George R. , Biggs David
Published: February 2007

In the search for relevant assays for mutagenicity testing, considerable attention has been given to the use of mammalian cells in vitro and the incorporation of metabolic activation in the protocol. Chinese hamster ovary (CHO) cells are commonly chosen as the target cells for cytogenetic tests because of their excellent growth characteristics and long lifespan in culture. However, there may be cellular factors affecting the uptake, metabolism, and repair of damage which are not the same in all cell lines. The response of CHO cells and three human diploid fibroblast strains (IMR‐90, WI‐38, S‐3299) to benzo(a)pyrene (BP) and dimethylnitrosamine (DMN) were compared using sister chromatid exchange (SCE) analysis as a measure of genetic damage. For both BP and DMN the human cells and the CHO cells showed dose‐response slopes that were significantly different from zero, except CHO cells treated with BP for 1 hr and S‐3299 cells treated with DMN. Whereas human and CHO cells showed similar dose‐responses to BP and the three human cell strains had similar dose‐responses to BP and DMN, the dose‐response of the human cells to DMN was statistically less significant than that of CHO cells. Reducing the duration of chemical treatment in CHO cells had no effect on the slope of the dose‐response curves for BP or DMN. The observed differences between human and CHO cells may reflect differences in the fate of metabolic intermediates of DMN.
Restitution of chromatid and isochromatid breaks induced in the G2 phase by actinomycin D
Authors: Cherry Lorraine M. , Hsu T. C.
Published: February 2007

Although actinomycin D (AMD) appears to cause chromatid breakage, it has been suggested that it merely weakens the chromosomal proteins, causing breaks to occur during the stress of fixation. To determine if this was true, we examined lymphocytes treated with AMD (3.5 μg/ml) for 90 min prior to harvesting for evidence of DNA repair. Besides single chromatid breaks, we observed a high frequency of chromatid exchange figures (translocations, inversions, rings) and closed isochromatid breaks, indicating that a type of DNA repair leading to chromosome aberrations had occurred prior to cell fixation. Therefore, at least some of the breaks observed after AMD treatment in G2 represented true DNA damage and were not merely artifacts of fixation.
Sister chromatid exchange induction in two cell lines
Authors: Mitchell Gillian A. , Meher‐Homji K. M. , Baker R. S. U.
Published: February 2007

Sister chromatid exchange (SCE) induction by the procarcinogen benzo (a)‐pyrene (BP) was studied using two established cell lines. Chinese hamster ovary (CHO) and Chinese hamster lung (Don) cells were exposed to varying concentrations of BP in the presence and absence of a rat liver metabolizing system. Results showed a significant difference in the abilities of the two cell lines to induce SCE in the absence of liver homogenate. These experiments demonstrate that Don cells are capable of generating active metabolites from biologically inactive procarcinogens presumably due to an inherent metabolizing system which is deficient or absent in CHO cells.
Mutagenicity of (R) and (S) styrene 7,8‐oxide and the intermediary mercapturic acid metabolites formed from styrene 7,8‐oxide
Authors: Pagano Dennis A. , Yagen Boris , Hernandez Oscar , Bend John R. , Zeiger Errol
Published: February 2007

We have tested the two enantiomers of styrene 7,8‐oxide and various thioether metabolites of racemic styrene 7,8‐oxide for their direct mutagenicity in Salmonella typhimurium TA100. The mutagenicity data suggests that the (R) enantiomer is more mutagenic than the (S) enantiomer, with the racemic mixture intermediate between the two. The thioether metabolites were not mutagenic. The difference in the mutagenicities of enantiomers probably resulted from a stereoselective process in the Salmonella tester strain. At the present time it is not clear whether the rate‐limiting reaction is the interaction of the enantiomers with DNA or some other cellular component.
In vivo and in vitro genotoxicity of three antihypertensive hydrazine derivatives (hydralazine, dihydralazine, and endralazine)
Authors: De Flora S. , Zanacchi P. , Bennicelli C. , Camoirano A. , Cavanna M. , Sciabà L. , Cajelli E. , Faggin P. , Brambilla G.
Published: February 2007

Three antihypertensive hydrazine derivatives (hydralazine, dihydralazine, and endralazine) were found to be genotoxic in four in vivo or in vitro short‐term test systems, a) In mice, a single ip administration of the LD50 of the three drugs caused a small but statistically significant increase over controls in DNA elution rate, ie, a modest amount of DNA fragmentation, in three of the four organs (liver, lung, kidney, and spleen) tested, DNA damage being absent in lung for hydralazine and endralazine and in liver for dihydralazine. Only for hydralazine DNA lesions were always repaired within 12 hr, in agreement with the constant lack of cumulative effects in mice given five successive daily doses. The rank of potencies was hydralazine< dihydralazine<endralazine. b) In mice bone marrow cells, all three hydrazine derivatives induced a modest but statistically significant increase over controls in the frequency of sister chromatid exchanges, the rank of potencies being in this case dihydralazine < endralazine < hydralazine. c) In the Ames reversion test all three drugs behaved as direct‐acting mutagens of low potency, whose activity was not influenced by rat liver nor by mouse liver or lung S‐9 fractions. Hydralazine and dihydralazine elicited mixed genetic mechanisms of mutations, while endralazine exclusively induced frameshift errors in Salmonella DNA. The recently developed strain TA97 was the most efficient in revealing frameshift errors with all three drugs. d) The selective lethality assays in a battery of two S typhimurium and five E coli strains confirmed the direct genotoxicity of hydralazine, dihydralazine, and endralazine, in order of potency. Potency was evaluated by means of a sensitive and reliable micromethod procedure. Among those investigated, the recA recombination repair and the lexA post‐replication repair (“SOS functions”) and, to a lesser extent, also the polymerase I mechanism, appeared to contribute to the specific DNA repair with all three drugs, while excision repair systems (uvrA and uvrB) did not appear to be involved.
Cytogenetic effects of shale‐derived oils in murine bone marrow
Authors: Meyne Julianne , Deaven L. L.
Published: February 2007

The cytogenetic effects of exposure of mice to shale‐derived oils by either skin painting or intraperitoneal injection were examined. Skin painting with 40 mg crude oil every other day for five weeks had no effect on the frequency of chromosomal aberrations observed in the bone marrow. Three daily intraperitoneal injections of 0.5–2.0 ml/kg per day of a crude shale oil from an aboveground retort induced a dose‐related increase in the frequency of aberrations observed. A hydrotreated sample of this oil produced a similar pattern of aberration induction, but at lower frequencies. Crude shale oil from a modified in situ retort induced the highest frequency of chromosomal aberrations at the 0.5 ml/kg dose; lower frequencies were induced at the 1.0 ml and 2.0 ml/kg doses. Of the three shale oils tested, only the crude oil from the aboveground retort induced increased frequencies of sister chromatid exchanges and only at doses that also induced structural aberrations. These studies indicate that structural aberration analysis is a more sensitive test than sister chromatid exchange analysis for the type of DNA damage induced by shale‐derived oils in murine bone marrow cells.
Genetic effects of deoxyribonucleotide pool imbalances
Authors: Kunz Bernard A.
Published: February 2007

In vivo DNA precursor imbalances can have profound genetic consequences in prokaryotes and eukaryotes. In vitro studies have demonstrated that DNA replication fidelity is dependent on correct balances of deoxyribonucleoside triphosphates during DNA synthesis. These findings suggest that intracellular concentrations of DNA precursors may be regulated in order to minimize the frequency of genetic change. In addition, they indicate the existence of important nonDNA targets for the induction of mutation, recombination, chromosome aberrations, etc. In this article, the genetic effects of deoxyribonueleotide pool imbalances are reviewed.
The hepatocyte primary culture/DNA repair assay using mouse or hamster hepatocytes
Authors: McQueen Charlene A , Kreiser Dawn M , Williams Gary M.
Published: February 2007

The hepatocyte primary culture (HPC)/DNA repair assay using rat hepatocytes was developed to identify genotoxic chemicals. Since there are species differences in susceptibility to chemical carcinogens, it was desirable to extend the assay to other species. Carcinogens and noncarcinogens from six structural classes were tested with hepatocytes from B6C3F1 mice or Syrian hamsters. In hepatocytes from both species, DNA repair was elicited by the carcinogens methyl methanesulfonate, aflatoxin B1, 2‐acetylaminofluorene, benzo(a)pyrene, dimethylnitrosamine, nitrosopyrrolidine, 3'‐methyl‐4‐dimethylaminoazobenzene, and p‐dimethylaminoazobenzene. With aflatoxin B1, mouse hepatocytes required a dose of 10−4 M for a maximum response while only 10‐6 was needed for hamster hepatocytes. All the presumed noncarcinogens, except 4‐dimethylaminoazoben‐zene‐4'‐sulfonyl chloride, were negative in mouse hepatocytes. This chemical, as well as aflatoxin G2 and pyrene, which have not been tested for carcinogenicity in the hamster, were positive in hamster hepatocytes. These findings demonstrate that genotoxic chemicals can be identified by the HPC/DNA repair assay using hamster or mouse hepatocytes. Furthermore, in vivo differences in susceptibility to chemical carcinogens such as aflatoxin B are reflected in the in vitro assay.
5‐nitroacenaphthene: A newly recognized role for the nitro function in mutagenicity
Authors: McCoy Elena C. , de Marco George , Rosenkranz E. Joshua , Anders Monika , Rosenkranz Herbert S. , Mermeistein Robert
Published: February 2007

The direct‐acting mutagenicity of 5‐nitroacenaphthene for Salmonella typhimurium is dependent upon the reduction of the nitro function as evidenced by the significant decrease in mutagenicity seen with nitroreductase‐deficient Salmonella strains. Addition of microsomal preparations results in a significant increase in mutagenicity and a by‐passing of the block in nitroreductase‐deficient and arylhy‐droxylamine esterifying‐deficient enzyme strains. The results are taken to indicate that the microsome‐induced mutagenicity is due primarily to oxidation of the acenaphthene moiety. The results are consistent with recent studies which indicate that the nitro function exercises a directing effect on ring oxidation.
Induction of ouabain‐resistant mutants by chemical carcinogens in rat prostate epithelial cells
Authors: Link Karl H. , Heidelberger Charles , Landolph Joseph R.
Published: February 2007

We determined optimal conditions to quantitatively select ouabain‐resistant (Ouar) mutants induced by chemical carcinogens in a rat prostate epithelial cell line (RPYK). These conditions included selection of Ouar mutants in 3 mM ouabain, an expression time of two days following a two‐day treatment with carcinogens, and a reseeding density of 2 × 105 mutagenized cells per 100 mm dish to select mutants in ouabain. Ouar mutants induced by N‐methyl‐N'‐nitro‐N'‐nitrosoguanidine (MNNG) remained stably Ouar when passaged in nonselective medium. Hemicyst formation, a characteristic of epithelial cells, was reversibly inhibited by ouabain in wild‐type cells and was resistant to ouabain in Ouar cells. The direct‐acting carcinogens MNNG and methylazoxymethanol‐acetate (MAMA) and the environmentally widespread procarcinogens aflatoxin B1 and benzo(a)pyrene increased the frequency of Ouar mutants in RPYK cells. The procedures developed here now make it possible to detect some environmental carcinogens likely to cause prostate cancer by virtue of their ability to mutate cultured prostate epithelial RPYK cells. The sensitivity of the RPYK cell line to aflatoxin‐induced cytotoxicity and mutagenesis also makes it a useful cell system in which to study enzymes governing the conversion of aflatoxin to genotoxic metabolites.
Synergism in the transformation of hamster embryo cells treated with formaldehyde and adenovirus
Authors: Hatch George G. , Conklin Patricia M. , Christensen Carla C. , Casto Bruce C. , Nesnow Stephen
Published: February 2007

Formaldehyde is a large production volume chemical widely distributed in research laboratories, industrial workplaces, and home and personal environments. Inhalation studies with formaldehyde have documented its ability to produce squamous cell carcinomas in rats. When primary hamster embryo cells were treated by gaseous exposure to formaldehyde or by incorporation into the medium, a dose‐related increase in the frequency of SA7 virus transformation was produced. The length of chemical treatment and the time interval before subsequent addition of transforming virus was critical, with two‐hr treatment times as the most efficient. Treatment by gaseous exposure permitted utilization of lower treatment concentrations. Determination of formaldehyde concentrations in culture media of bioassay dishes treated by this method documented that 2.2 fig/ml produced significantly enhanced viral transformation. Exposure of hamster embryo cells to formaldehyde by these methods produces reproducible and quantitative genotoxic effects.
Effects of antimutagens on prophage induction in E coli lysogenic for lambda
Authors: Persons Diane L. , Shankel Delbert M.
Published: February 2007

The effects of caffeine, acriflavine, spermine, quinacrine, and adenosine on spontaneous and UV‐induced prophage induction in repair‐proficient and ‐deficient strains of lysogenic Escherichia coli were examined. Caffeine caused a coinducing effect on UV induction in KMBL 160 (repair proficient) and KMBL 163 (uvrA), an anti‐inducing effect in KMBL 161 (uvrE), and had no detectable effect in KMBL 164 (uvrC). Acriflavine increased UV induction in KMBL 160 and decreased it in all three repair‐deficient mutant strains. Spontaneous induction was reduced by acriflavine in all four strains. Spermine caused a decrease in UV induction in KMBL 160 and KMBL 164, while it had limited effect in KMBL 161 and KMBL 163. For spontaneous induction spermine caused an increase in KMBL 160 and KMBL 163, a decrease in KMBL 164 and no detectable effect in KMBL 161. Quinacrine had no significant effect on spontaneous induction in KMBL 160 and KMBL 164, but caused a decrease in spontaneous induction in KMBL 161 and KMBL 163. Quinacrine produced no effect on UV induction in KMBL 160; however, it decreased UV induction in the three repair‐deficient strains to some extent. A significant increase in spontaneous induction in KMBL 160 was caused by adenosine, while it had little effect in the repair‐deficient strains. UV induction was not affected by adenosine.
Mutagenic activity from nitrosation of oligoamines
Authors: Murphey‐Corb Michael , Kong Hay‐Long , Murray Michael L.
Published: February 2007

To determine structural features necessary for the production of direct mutagenic activity from oligoamine‐nitrate reaction mixtures, we systematically tested a group of aliphatic amine substrates for comutagenic action with nitrite. The ability to react with nitrite and form direct‐acting mutagenic derivatives was common to a reasonably well defined class of aliphatic polyamines. In general, primary‐secondary diamino compounds were mutagenic in the Ames Salmonella tester system when reacted with nitrite, whereas primary and secondary amines produced no direct mutagenic activity when tested separately. In combination with teritary amino groups, primary amines were inactive; one secondary‐tertiary amine was tested, and this substrate produced mutagenic activity.
Review: Putative mutagens and carcinogens in foods. I. Nitrate/nitrite ingestion and gastric cancer mortality
Authors: Hartman Philip E.
Published: February 2007

Published figures for per capita daily levels of nitrate ingestion in the 1970s are compared with gastric cancer mortality estimates for the same period. A strong positive correlation is observed in 12 countries, not only when the data are analyzed as a linear—linear function, as illustrated in this paper, but also when the relationship is analyzed as a function of (nitrate)2. This correlation supports the concept that important components of gastric cancer induction are the in vivo bacterial reduction of nitrate to nitrite and the intragastric formation of mutagenic/ carcinogenic nitroso, and possibly nitro compounds. Data are summarized from a recent National Academy of Sciences [1981] study that enumerates by individual dietary sources the mean ingestion of nitrate and nitrite by the United States population at the present time. The ingestion figures are used to calculate the probable current gastric nitrite load in US adults with normal gastric acidity. Similar calculations are provided for past years (1925, 1936–1937, and 1971–1972). Since 1925, there has been an approximately threefold decrease in gastric cancer mortality in the US, and this decline is paralleled by an approximately fourfold decrease in average gastric nitrite load. The excessive ingestion of nitrate/ nitrite in the US in past years is attributed to the very high content of nitrate and nitrite in cured meats. Several ways compatible with current US farming and marketing practices that are capable of reducing the gastric nitrite load even further are pointed out.
The induction of chromosome aberrations by cis‐platinum(II) diamminodichloride in drosophila melanogaster
Authors: Brodberg R. K. , Lyman R. F. , Woodruff R. C.
Published: February 2007

We have determined the in vivo effects of cis‐platinum(II)diarnminodichloride (cis‐PDD) treatment on the induction of chromosome aberrations in Drosophila melanogaster germ cells. cis‐PDD treatment induces significant increases in chromosome breakage in all stages of spermatogenesis in a battery of test systems using ring or rod‐X males and repair‐proficient or deficient females. Since no increase in nondisjunction was induced by cis‐PDD in either male or female germ cells, any aneuploidy inducing effects of this compound should result from its clastogenic action. We also find that mei‐9 excision repair function is involved in the repair of cis‐PDD‐induced DNA lesions in a manner that provides additional evidence that partial and ring chromosome losses are not completely homologous.
Rat nasal tissue activation of benzo(a)pyrene and 2‐aminoanthracene to mutagens in salmonella typhimurium
Authors: Bond James A. , Li Albert P.
Published: February 2007

Cytochrome P‐450‐dependent monooxygenase activity has been measured in the nasal turbinates of dogs and rats. The capacity of male Fischer‐344 rat nasal tissue to bioactivate benzo(a)pyrene (BaP) and 2‐aminoanthracene (2‐AA) to mutagens in Salmonella typhimurium was investigated. 2‐AA was mutagenic in strains TA98 and TA 100 when nasal tissue S‐9 was utilized as the activating enzyme system and BaP was mutagenic in strain TA 100. At all doses and protein concentrations tested, 2‐AA displayed nearly 500–1000 times greater bacterial mutagenicity than BaP. In strain TA‐100, nasal tissue S‐9 was approximately twice as active toward 2‐AA as lung S‐9 and 75% as active as liver S‐9. Aryl hydrocarbon hydroxylase activity was detected in rat nasal tissue when 14C‐BaP was used as a substrate. Rat nasal tissue metabolized BaP to several oxidized metabolites which included dihydrodiols, quinones, and phenols. 3‐Hydroxybenzo(a)pyrene and BaP‐3,6‐quinone were the major metabolites detected (150 pmoles/mg protein/30 min). These results indicate that rat nasal tissue can metabolize promutagens to reactive species which may play an important role in xenobiotic‐induced nasal tumors.
Review: Putative mutagens and carcinogens in foods III. Butylated hydroxytoluene (BHT)
Authors: Malkinson Alvin M.
Published: February 2007

Although the average American's daily consumption of BHT can be measured in milligrams, there are numerous reports that BHT causes organ damage in laboratory animals. Only a few genotoxic effects of BHT have been reported, however, including mutagenicity in the abnormal sperm assay and ambiguous results regarding its teratogenicity. More dramatic are the modulatory effects of BHT on the actions of established mutagens and carcinogens. BHT can either enhance or inhibit mutagenic potency, depending on the substance tested. For example, in the Ames test, BHT is antimutagenic towards benzo(a)pyrene, but increases the number of Salmonella revenants induced by aflatoxin B1. BHT is one of the few compounds to have both tumor prophylactic and tumor promoting capacities. It is the temporal sequence in which BHT and carcinogens are administered to test animals which determines how BHT affects the response to these carcinogens. In common with other antioxidants, BHT inhibits the ability of carcinogens to induce tumors in various rodent organs when the animal is given BHT prior to carcinogen treatment. Unlike other antioxidants, however, the number of tumors increase when BHT is administered after carcinogen exposure. The comutagenic and cocarcinogenic properties of BHT have been demonstrated in tests ranging from the Ames test to cell transformation procedures to in vivo assays. These effects are probably mediated by metabolites of BHT, rather than by BHT itself.
Inhibitors of poly(ADP‐ribose) polymerase enhance DNA strand breaks, excision repair, and sister chromatid exchanges induced by alkylating agents
Authors: Park Sang Dai , Kim Chul Geun , Kim Moon Gyo
Published: February 2007

Benzamide and 3‐aminobenzamide, inhibitors of poly(ADP‐ribose) polymerase, synergistically enhanced the frequencies of unscheduled DNA synthesis and sister chromatid exchanges in Chinese hamster ovary (CHO) cells treated with N‐methyl‐N'‐nitro‐N‐nitrosoguanidine (MNNG). These inhibitors also increased methyl methanesulfonate (MMS)‐ or MNNG‐induced DNA strand breaks and significantly retarded the rejoining of strand breaks in CHO and HeLa S3 cells. These results suggest that poly(ADP‐ribose) is important in the repair of DNA damage after exposure to alkylating agents and exercises a regulatory role in stabilizing chromatin structure whenever strand breaks occur in DNA.
Mutagenicity evaluation of amino‐oxazoline derivatives using in vitro and in vivo short‐term tests
Authors: Suter W. , Jaeger I. , Racine R. R. , Donatsch P. , Neumann P. , Matter B. E.
Published: February 2007

During routine investigation of potential drugs it was found that 1‐methyl‐4‐(2‐oxazoline‐2‐ylamino)‐indazole (<1) compound 1 was mutagenic for Salmonella typhimurium TA 1535 and TA 100. The genotoxicity of compound 1 was confirmed by the following in vitro test systems: V79 Chinese hamster cells (HGPRT‐locus), Saccharomyces cerevisiae D7 (mitotic gene conversion, mutations, aberrations), and Escherichia coli (rec‐assay). On the other hand, when compound 1 was tested in vivo (micronucleus test in mice and sister chromatid exchange in Chinese hamsters) it did not show evidence of genotoxic activity. In order to study structure/activity relationships, different analogues of compound 1 were tested in Salmonella typhimurium TA 1535. The tests showed that (1) most 2‐amino‐oxazolines were mutagenic for the test organism; (2) the 2‐amino‐imidazoline and 2‐amino‐thiazolidine derivatives tested were not mutagenic; (3) substituents bound to the extranuclear nitrogen of the 2‐aminooxazoline ring had only a weak influence on the mutagenic potential; and (4) methylation of the oxazoline ring, most conspicuously at the carbon in position 5, strongly reduced the mutagenic effect. From these observations it is concluded that the reaction of nucleophilic DNA sites with the most electrophilic site of the oxazoline ring, ie, the carbon in position 5, is responsible for the genotoxicity of amino‐oxazoline compounds. Due to the genotoxicity observed in these in vitro tests this class of compounds was no longer developed, but dropped, even without performing a long‐term carcinogenicity study or considering the negative in vivo findings.
The effect of culture conditions and toxicity on the ames salmonella/microsome agar incorporation mutagenicity assay
Authors: Kazmer Sonja , Katz Marion , Weinstein David
Published: February 2007

Various methods were used to reconstruct an environment similar to a chemically bactericidal or bacteriostatic effect in the Ames mutagenicity assay in order to determine whether a false‐positive result could occur. Neither population reduction, sonication, nor increased histidine produced an increase of spurious revertant colonies.
Evaluation of the release of mutagens and 1‐nitropyrene from diesel particles in the presence of lung macrophages in culture
Authors: King Leon C. , Loud Kenneth , Tejada Silvestre B. , Kohan Mike J. , Lewtas Joellen
Published: February 2007

The release and recovery of mutagenic activity and 1‐nitropyrene from diesel particles phagocytized and cultured with lung macrophages were studied. The Ames Salmonella typhimurium plate incorporation assay was used to measure mutagenic activity. Quantitative analysis of 1‐nitropyrene was performed with liquid chromatography/fluorescence analysis. The cytotoxicity and phagocytosis of diesel particles with and without fetal calf serum were evaluated to select exposure concentrations that resulted in minimal toxicity and maximal engulfment of particles by the macrophages. The diesel‐particle exposure concentrations for the mutagenicity studies were 200 μg/ml in the absence of serum and 375 μg/ml in the presence of serum. Engulfment and incubation of diesel particles with lung macrophages resulted in the loss of considerable mutagenic activity (97–98%) and significantly less 1‐nitropyrene (10–25%). These studies suggest that lung macrophages have the capability to metabolize mutagenic nitroaromatics found in diesel particles.
Effect of BrdUrd and low doses of gamma radiation on sister chromatid exchange, chromosome breaks, and mitotic delay in mouse bone marrow cells in vivo
Authors: Morales‐Ramírez Pedro , Vallarino‐Kelly Teresita , Rodriguez‐Reyes Regina
Published: February 2007

We have measured, in mouse bone marrow cells in vivo, the ability of low doses of gamma radiation to induce sister chromatid exchanges (SCEs) in unifilarly 5‐bromodeoxyuridine (BrdUrd)‐substituted DNA. Also examined was the effect of BrdUrd incorporation on SCE induction by radiation, the comparative frequency of SCE and chromosome breaks induced by gamma radiation, the ability of ionizing radiation to interfere with normal cellular proliferation, and the relationship between proliferative inhibition and SCE and chromosome break frequency. A direct relationship between the number of SCEs and gamma radiation dose was observed, an effect which was dependent on BrdUrd incorporation. The frequency of SCE was 80 times higher than that of chromosome aberrations in cells with BrdUrd‐substituted DNA, and there was no difference between the frequency of SCE in cells with or without chromosome breaks. The mitotic delay increased with the time between irradiation and harvesting. There was no relationship between the extent of mitotic delay and the number of SCEs.
Characterization of automotive emissions by bacterial mutagenesis bioassay: A review
Authors: Claxton Larry D.
Published: February 2007

Due to the growing numbers of diesel passenger automobiles in the United States, there has been an expanded effort to understand the health effects of airborne pollutants arising from increased automotive emissions. Bacterial mutagenicity testing has played an important role in the characterization of genotoxic effects and components arising from these combustion products. This review examines published material concerning the bacterial mutagenicity of automotive emissions. In addition, the paper explores factors that modify the mutagenicity of mobile‐source emissions, the use of bacterial tests for the comparison of various mobile source emissions, and the use of bacterial tests to examine the phenomena of mammalian uptake and metabolism.
Sequestration and release of polycyclic aromatic hydrocarbons by vertebrate cells in vitro
Authors: Kocan R. M. , Chi E. Y. , Eriksen N. , Benditt E. P. , Landolt M. L.
Published: February 2007

Vertebrate fibroblasts grown in vitro and exposed to various concentrations of the mutagen/carcinogen benzo(a)pyrene (B(a)P) internalized the compound and re‐crystallized it in lysosomes by 6–18 h postexposure. This phenomenon occurred when B(a)P at or above 10 μg/ml was introduced to the culture medium in a solvent such as DMSO or acetone but not when introduced dissolved in serum. Likewise, high fetal bovine serum concentrations in the culture medium (>20%) as well as human serum (10%) inhibited crystal formation, presumably owing to lipid competition for the compound. Electron‐microscopic observations of the cells during the uptake and crystal forming periods revealed that the cell membrane became altered within 3 h of exposure to B(a)P. This was followed by a return to normal of the membrane and the appearance of vesicles within the cell by 6–8 h. The vesicles then became filled with crystals which continued to grow while in the presence of B(a)P and disappeared when the cells were exposed to B(a)P‐free culture medium or serum lipids. Introduction of B(a)P into culture medium containing delipidated serum resulted in crystal formation indistinguishable from that which occurred when whole serum was present. Crystals were not formed when total lipoprotein and the lipoprotein components VLDL, LDL, HDL2, and HDL3 were used as solvents for B(a)P. The process of crystal formation was inhibited by the addition of 10−3 M KCN, and removal of the crystals was dependent on the concentration of lipoprotein in the culture medium.
The mutagenic activity of 5‐bromo‐2′‐deoxyuridine (BrdU) in vivo in rats
Authors: Maier P. , Weibel B. , Zbinden G.
Published: February 2007

BrdU tablets were implanted subcutaneously in rats, and BrdU concentrations were determined in the serum. Within 5 hr peak concentrations of 10 μg BrdU/ml blood were reached. The influence of BrdU in vivo on cell cycling, DNA synthesis, spontaneous sister chromatid exchange (SCE) frequencies, and gene‐mutation frequencies (6‐TGr) was determined in freshly isolated cells from a subcutaneous granulation tissue. The most significant effect of BrdU in vivo was a doubling of the spontaneous 6‐TGr frequency.

In reconstruction experiments in vitro the mutagenic activity of BrdU applied in concentrations found in vivo was 2.5–6‐fold higher.

With the use of agar‐coated tablets, BrdU concentrations in the blood were reduced by half, and no peak concentration was found. The differential staining of chromatids was still sufficient. Since the mutagenic effect of BrdU in vitro was found to be strongly concentration dependent, the use of agar‐coated tablets is recommended in experiments in which the compound is used to demonstrate SCE in vivo.
Evaluation of an exposure system using cells grown on collagen gels for detecting highly volatile mutagens in the CHO/HGPRT mutation assay
Authors: Zamora P. O. , Benson J. M. , Li A. P. , Brooks A. L.
Published: February 2007

Chinese hamster ovary (CHO) cells were grown on hydrated collagen gels, the overlaying medium removed leaving the cells at an air/collagen interface, and the cells exposed to a dynamic flow of ethylene oxide. Increases in CHO cell mutant frequency and decreases in cell viability were observed. To establish if the exposure system could be simplified, cells were exposed in sealed bottles (static system) to ethylene oxide. No substantial changes in cytotoxicity, mutant frequency, or effective concentration were noted when comparing static versus dynamic exposure systems. The general usefulness of the exposure system using cells grown on collagen gels was evaluated in a static system using propylene oxide and 1,2‐dichloroethane, both of which were found to be mutagenic and cytotoxic. Comparatively, the exposure of cells by the collagen gel method was as effective in detecting genotoxic damage as were conventional methods (cells covered with medium) using cells grown on glass substrates. The exposure of CHO cells on collagen gels to highly volatile mutagens was simple and inexpensive, and may be generally useful in the detection of gaseous or volatile mutagens.
The induction of bacterial mutation and hepatocyte unscheduled DNA synthesis by monosubstituted anilines
Authors: Thompson Christina Z. , Hill Leo E. , Epp Janet K. , Probst Gregory S.
Published: February 2007

A group of 45 monosubstituted aniline compounds was tested for the induction of point mutations in Salmonella typhimurium and Escherichia coli as well as for unscheduled DNA synthesis (UDS) in rat hepatocyte culture. Eleven compounds were bacterial mutagens, and five compounds induced UDS. Among these a correspondence between mutagenicity and UDS occurred for only two compounds (o‐phenylenediamine and 4‐aminobiphenyl), and these were also reported to be carcinogenic in rodents. Bacterial mutation was observed for one compound (p‐phenylenediamine) not carcinogenic in rodents, and six suspect carcinogens were not detected in either test. In addition, eight compounds of unknown carcinogenic potential induced either bacterial mutation or UDS.
Sister chromatid exchange distributions in rabbit lymphocytes treated with streptonigrin
Authors: DuFrain Russell J.
Published: February 2007

Streptonigrin (NSC‐45383), a direct‐acting clastogen which induces SCEs in vivo and chromosome aberrations both in vivo and in vitro, was evaluated for SCE induction in both G0 and stimulated rabbit lymphocytes. Determinations were made for 16 cultures from seven female rabbits. These included controls as well as cells exposed to 90 μg/kg in vivo, cells pulse‐treated with 50 ng/ml in vitro, and a culture continuously exposed to 5 ng/ml in vitro. For all cultures the SCE/ cell frequency was determined from 20 complete (44 chromosome) metaphases and, in selected cultures, SCEs on individual chromosomes (880 per culture from 20 cells) were enumerated to determine SCE/chromosome frequency and the chromosomal distribution of SCEs. Analysis of variance and least significant difference tests of the √x transformed SCE/cell data show that cells exposed to Streptonigrin while dividing have significantly higher (P<0.01) frequencies (over double the control 5.3 SCE/cell value) whereas treated G0 cells were not significantly different from the controls. Dispersion analysis of both SCE/cell and SCE/ chromosome data confirms the adequacy of the Poisson distribution for spontaneous or baseline but not streptonigrin‐induced SCEs.
Further study on the cytogenetic effects of combined chemotherapy with isoniazid and para‐aminosalicylic acid on human lymphocytes in vivo: Sister chromatid exchanges, chromosome aberrations in first‐division metaphases, cell growth kinetics, and mitotic index
Authors: Jaju Madhuri , Jaju Manjula , Ahuja Y. R.
Published: February 2007

Tuberculosis patients under therapy with the drug combination isoniazid (INH) and para‐aminosalicylic acid (PAS) were screened to investigate the cytogenetic effects. Results were compared with those from the patient controls (ie, tuberculosis patients before starting drug therapy) and general controls (individuals from the general population). The induction of chromosome aberrations was homogeneous and increased significantly in all the drug‐exposed patients, whereas the frequency of sister chromatid exchanges (SCEs) was increased only in one of them. These results indicated differences in the two processes: chromosome aberrations and SCEs. Patients under therapy exhibited no change in cell growth kinetics, but the mitotic index was slightly enhanced compared to patient controls. It is concluded that the drug combination of INH+PAS induces damage in lymphocyte chromosomes in vivo. Further studies should be carried out on germ cells.
Evaluation of the genotoxic and embryotoxic potential of chlorpyrifos and its metabolites in vivo and in vitro
Authors: Muscarella Donna E. , Keown Jeffrey F. , Bloom Stephen E.
Published: February 2007

The genotoxicity and embryotoxicity of chlorpyrifos (CPF) and two metabolites were evaluated using the chick embryo, Chinese hamster ovary cells, and by examing blastocysts from superovulated cows crossed to chlorpyrifos‐treated bulls. Chlorpyrifos and metabolites were dissolved in acetone and administered to 3‐day embryos by the air cell method. The LD50 was 1,500 μg/embryo when mortality was checked through and including 17 days of development. The metabolites were more embryotoxic than the parent compound, CPF. Chlorpyrifos and metabolites did not increase the sister chromatid exchange (SCE) frequency above background at any dosage in the 3‐day chick embryo assay. Similarly, none of these compounds increased SCE frequencies in three‐point dosage tests (1, 10, 100 μg/ml) using Chinese hamster ovary cells. Controls in these assays consisted of the solvent carrier acetone (7.0 ± 2.5 SCE/cell) and 8.6 μg/ml methyl methane sulfonate (30.5 ± 7.4 SCE/cell). Studies of bovine blastocysts obtained from superovulated cows crossed with Dursban 44 treated bulls did not reveal evidence of chromosome aberrations or developmental anomalies associated with pesticide application. However, reproductive performance of breeders may be subnormal as a result of severe poisoning. This underscores the limitations of short‐term assays and emphasizes the need to perform thorough toxicological assays of a chemical according to actual usage patterns in the species of concern.
Effects of temperature on the frequency of sister chromatid exchanges (SCEs) in peripheral blood lymphocytes of man and muntjac
Authors: Das B. C. , Sharma T.
Published: February 2007

The incidence of sister chromatid exchanges (SCEs) and cell proliferation kinetics have been studied in peripheral blood lymphocytes of man and muntjac grown at 33 to 44 °C to gain insight into SCE formation. The frequency of SCEs increased as a function of growth temperature. At a given temperature, however, the frequency of SCEs varied with the sampling times; the early sampled cells showed fewer SCEs than did those harvested late. At 33 °C the frequency of SCEs was lowest and there was a marked delay in cell‐cycle progression. The number of SCEs was maximum at 40 °C in human and 42 °C in muntjac. Cell proliferation was markedly affected at higher temperature and 44 °C was found to be intolerable for lymphocytes of both the species. It is proposed that certain temperature‐dependent enzyme(s) associated with DNA replication kinetics may be involved in the formation of SCEs.
Induction of persistent hypersensitivity to lung tumorigenesis by in utero X‐radiation in mice
Authors: Nomura Taisei
Published: February 2007

A single dose (36 rad) of X rays was given to mouse embryos and neonates that were then treated with urethane at 21 days of age. Although in utero X‐radiation to mice was not tumorigenic, it significantly increased lung tumor susceptibility to a postnataliy‐given carcinogen, urethane. X‐ray induction of persistent hyper‐sensitivity to lung tumorigenesis was apparent at all stages during days 0 to 14 of gestation (except on day 6), but was not observed at late fetal and neonatal stages.
Influence of strong magnetic fields on genetic endpoints in Tradescantia tetrads and stamen hairs
Authors: Baum John W. , Nauman Charles H.
Published: February 2007

Inflorescences from Tradescantia clones 4430 and 02 were subjected to mean magnetic field intensiteis of 0.16 or 0.76 to 0.78 tesla for 6 to 11 days. Following exposures to both intensities, damage to pollen mother cell chromosomes at early prophase was determined by scoring the frequency of micronuclei in early tetrads. Pink mutations in stamen hair cells of clone 4430 were scored for 15 days after a 6‐day exposure to the higher intensity level while clone 02 was scored during and for 6 days after an 11‐day exposure to the 0.16 tesla field. Comparison of micronuclei results from exposed groups to those for control groups that were scored concurrently showed that there was no significant difference in frequency for either clone or either field intensity (P values in contingency table analyses were between 0.42 and 0.6); similarly, pink mutation frequencies for clone 4430 exposed and control groups did not differ significantly (a contingency test yielded χ2 = 1.4 and P = 0.26). Comparisons of pink mutation frequencies during the first 6 days of clone 02 exposure to those in the period when an effect should be greatest (days 7 through 17 revealed no significant difference (χ2 = 2.6 and P = 0.1) between the two scoring periods, through frequencies were higher during the early scoring period.
Mutagenicity in a modified Salmonella assay of fabric‐protecting products containing 1,1,1‐trichloroethane
Authors: Nestmann Earle R. , Otson Rein , Kowbel David J. , Bothwell Peter D. , Harrington Tina R.
Published: February 2007

Methyl chloroform (1,1,1‐trichloroethane) was identified as a major component in two fabric‐protector spray products. Mutagenic effects were determined at several dosage levels for the two products and some of the identified components. Levels of organics in the air of sealed desiccators, used as exposure chambers in modified Salmonella reversion assays, were measured by a gas chromatographic technique. Both fabric protectors and two samples of trichloroethane were mutagenic in strain TA 1535 and one of each was mutagenic in strain TA 100. Other constituents, such as petroleum distillate and p‐dioxane, were nonmutagenic at the tested exposure levels.
Stem‐Spermatogonial Survival and Incidence of Reciprocal Translocations in the γ‐Irradiated Boar
Authors: Erickson B. H. , Martin P. G.
Published: February 2007

To assess the effects of γ‐radiation on stem‐cell survival and incidence of reciprocal translocations, boar testes were irradiated with 100, 200, or 400 rad. Stem‐cell survival was markedly affected by 100 rad (51 % of control) and reduced to 34% of control by 400 rad. Production of differentiating spermatogonia was all but completely interrupted by 200 rad and spermatogonial renewal was incomplete at 12 weeks. From the state of the seminiferous epithelium at 12 weeks, estimates of the percentage of permanent impairment of sperm‐producing capacity ranged from 20 ± 6 (100 rad) to 67 ± 10 (400 rad). Incidence of translocations peaked at 200 rad and the number occurring at 100 and 400 rad was similar. Kinetics of porcine spermatogonial renewal differs considerably from those of the rodent and, relative to the rodent, this may account for the boar's higher sensitivity to stem‐cell killing and lower sensitivity to translocations.
An assay to detect chemically induced DNA repair in rat spermatocytes
Authors: Working Peter K. , Butterworth Byron E.
Published: February 2007

An in vivo/in vitro DNA repair assay has been developed to quantitate chemically induced unscheduled DNA synthesis (UDS) in rat spermatocytes utilizing autoradiography. Male Fischer‐344 rats were treated by i.p. injection or gavage with a variety of genotoxic agents dissolved in dimethyl sulfoxide, corn oil, or water. At selected times after treatment, spermatocytes were isolated by trypsin digestion of testes and cultured for 24 hr in the presence of 3H‐thymidine. The direct‐acting genotoxicants methyl methanesulfonate (MMS) and ethyl methanesulfonate and the chemotherapeutic agent cyclophosphamide (CPA) produced positive UDS responses in spermatocytes isolated 1 hr after i.p. injection. The UDS response evoked by either CPA or MMS was maximal within 1 hr after injection and declined rapidly thereafter to control levels. Other known genotoxicants—including dimethylnitrosamine, aflatoxin B1, 2‐acetylaminofluorene, 2,6‐dinitrotoluene, and 1,6‐dinitropyrene—failed to induce UDS, even with routes of administration and at times of exposure known to produce a positive response in hepatocytes. This negative response is consistent with these genotoxicants lack of mutagenic effect in rodent germ cells. These results demonstrate that the in vivo/in vitro spermatocyte DNA repair assay may be useful as a predictive screen for germ cell mutagens. Moreover, by its compatibility with similar assays which utilize other tissues from the same treated animal, this assay permits assessment of the organ specificity of the genotoxic response.
Anaphase‐telophase analysis of chromosomal damage induced by chemicals
Authors: Dulout Fernando N. , Olivero Ofelia A.
Published: February 2007

Three main aspects involved in the chemical induction of anaphase‐telophase aberrations in the first mitosis after treatment were analyzed: 1) the relationship between the frequency of anaphase‐telophase aberrations and the time of fixation after treatment; 2) the dose‐response relationships; and 3) the proliferative rate of cells exposed to chemicals which interact with DNA by different mechanisms. Experiments were carried out using Chinese hamster ovary (CHO) cells. The compounds examined were adriamycin (ADR) and mitomycin C (MMC). The frequency of cells with chromatin bridges or with lagging chromosomes as well as the mitotic index was determined in each experiment. The results obtained showed that 1) chromatin bridges and lagging chromosomes are apparently induced during the S period of the previous interphase; 2) the increase in the cytotoxicity index (inferred from the mitotic index) and the frequency of cells with chromatin bridges and lagging chromosomes were proportional to the treatment lapse and to the dose employed; and 3) the effect of ADR on cell growth differs from the effect of MMC. While ADR decreased the mitotic activity of cells in logarithmic growth phase, MMC induced mitotic delay. In accordance with these results, the occurrence of chromatin bridges in anaphase‐telophase could be explained by the induction of chromosome stickiness and, to a lesser extent, by the induction of exchange‐type aberrations. On the other hand, lagging chromosomes seem to be the result of chromatid or chromosome breaks because the lagging chromosomes observed were primarily, if not all, fragments and not whole chromosomes. Our evaluation of the anaphase‐telophase test indicates that it is very sensitive method for the detection of chemical clastogens, but other factors, such as mitotic depression, must be taken into account to avoid false‐negative results.
Chromium (VI) Potentiates Mutagenesis by Sodium Azide But Not Ethyl Methanesulfonate
Authors: Lavelle James M. , Witmer Charlotte M.
Published: February 2007

A fluctuation test using Salmonella typhimurium strain 1535 has been used in an experimental protocol to assess biological effects of interactions between chromium (VI), such as K2CrO4, and two DNA‐damaging agents, ethyl methanesulfonate (EMS), and sodium azide. Mutagenicity, expressed as the average number of mutations induced over a parallel control, was determined for the compounds alone and in combination. The significance of the differences between the “expected” response, calculated by simple addition of the responses from the individual tests, and the observed response when the combination was tested, were estimated by chi square. For the combination of K2CrO4 and NaN3, the response was significantly greater than expected suggesting a possible potentiation of mutagenesis. The opposite (a less‐than‐additive response) was found for the K2CrO4/EMS combination. Both effects were found to be dose related to the concentration of potassium chromate used. Toxicity of the compounds or their combinations to the bacteria could not explain the results.