bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phenotypic expression time of mutagen‐induced 6‐thioguanine resistance in Chinese hamster ovary cells (CHO/HGPRT system): Expression in division‐arrested cell cultures
Authors: O'Neill J. Patrick , Machanoff Richard , Hsie Abraham W. 
Published: February 2007

AbstractThe phenotypic expression time of ethyl methanesulfonate (EMS) induced 6‐thioguanine‐resistant mutants was studied with Chinese hamster ovary cells in culture (CHO/HGPRT system). After mutagen treatment of exponential phase cultures, the cells were maintained either in the exponential phase through subculture in medium containing 5% dialyzed fetal bovine serum (FBS) or in a nondividing viable state by use of medium containing 0–1 % dialyzed FBS. The time course of expression of the 6‐thioguanine‐resistant phenotype was similar with both exponential phase and division‐arrested cultures showing maximum expression by 9 days after mutagen treatment, and both methods of expression also yielded similar mutant frequencies over a range of EMS concentrations. This study shows that once the mutagenic event is fixed, the expression of the mutant phenotype does not require continued cell division since it occurs in division‐arrested cultures. These results also suggest that both dilution of pre‐existing hypoxanthine‐guanine phosphoribosyl transferase (HGPRT) enzyme by cell division and turnover by protein degradation are involved in the phenotypic expression. Both processes occur in exponential cultures, but only protein turnover in arrested cultures. Consistent with this was the demonstration that the rates of total cell protein turnover increased in division‐arrested cultures maintained in serum‐free medium. These results separate genetic damage and phenotypic expression in a temporal sense, and point out the need to consider the mechanisms responsible for each process involved in the induction and expression of mutations.
Studies of cytogenetic effects of sodium arsenicals on mammalian cells in vitro
Authors: Wan Bojian , Christian Robert T. , Soukup S. W. 
Published: February 2007

AbstractThe cytotoxic and cytogenetic effect of sodium arsenite and sodium arsenate on Chinese hamster ovary (CHO) cells is reported. Chromosome aberrations were induced with both arsenic compounds. Trivalent arsenic was more clastogenic than pentavalent arsenic. Sodium arsenite was also shown to produce increased sister chromatid exchange in CHO cells and increased chromosome breakage in human lymphocytes.
Detection of genotoxic carcinogens in the in vivo‐in vitro hepatocyte dna repair assay
Authors: Mirsalis Jon C. , Tyson C. Kim , Butterworth Byron E. 
Published: February 2007

AbstractThe in vivo‐in vitro hepatocyte DNA repair assay has been shown to be useful in the evaluation of the carcinogenic potential of chemicals. The purpose of this study was to apply this assay to determining the genotoxicity of compounds from a wide variety of structural classes. Male Fischer‐344 rats were treated by gavage or ip injection with compounds dissolved in either corn oil, water, or dimethyl sulfoxide (DMSO). At selected times after treatment, hepatocytes were isolated by liver perfusion and cultured with 3H‐thymidine. Unscheduled DNA synthesis (UDS) was measured by quantitative autoradiography as net grains/nucleus (NG); ≥ 5 NG was considered positive. Water, corn oil, or DMSO controls produced ‐3 to ‐6 NG with ≤ 6% of the cells in repair. All genotoxic hepatocarcinogens tested produced strong positive responses of > 15 NG including dimethylnitrosamine, 2‐acetylaminofluorene (2‐AAF), azoxymethane, 1,2‐dimethylhydrazine, benzidine, aflatoxin B1, 2,6‐dinitrotoluene, and 2,4‐diaminotoluene. The noncarcinogen, 2,6‐diaminotoluene, was negative. The mutagen and rat brain carcinogen methyl methanesulfonate (MMS) and the rat pancreatic carcinogen azaserine were also positive. The carcinogens benzo(a)pyrene and 7,12‐dimethylbenzen(a)anthracene yielded from ‐2 to ‐4 NG. This negative response is consistent with their lack of carcinogenic activity in rat liver. MMS produced the greatest amount of UDS 2 hr after treatment whereas 2‐AAF did not induce its maximum response until 12 hr post‐treatment. The potent hepatotoxin carbon tetrachloride induced a 40‐fold elevation in DNA replication 48 hr after a 400 mg/kg dose, but no UDS was observed at 2, 12, 24, or 48 hr post‐treatment. The weak hepatocarcinogen safrole induced no UDS suggesting that is is either nongenotoxic or is metabolized to an active form at an extremely slow rate following a single administration. These results demonstrate that this assay is valuable for the detection and study of a variety of genotoxic carcinogens.
Characterization of a rat lymphocyte culture system for assessing sister chromatid exchange. II. Effects of 5‐bromodeoxyuridine concentration, number of white blood cells in the inoculum, and inoculum volume
Authors: Kligerman A. D. , Wilmer J. L. , Erexson G. L. 
Published: February 2007

AbstractWe have examined the effects of variation in 5‐bromodeoxyuridine (BrdU) concentration, the number of white blood cells (WBCs) in the inoculum, and inoculum volume on sister chromatid exchange (SCE) frequency, mitotic activity, and cell cycle kinetics of phytohemagglutinin‐stimulated rat lymphocytes in whole blood culture. BrdU (1 to 5 μM) caused a dose‐dependent increase in SCEs/metaphase (7.6 to 12.0) and a dose‐dependent decrease in mitotic activity (5.3 to 3.1%). With 2 μM BrdU, as the number of cells in the inoculum increased (0.25 × 106 to 2.5 × 106), the mitotic activity decreased (7.7 to 1.8%). At all BrdU concentrations examined, changes in the number of WBCs in the inoculum caused significant changes in the SCE frequency. Thus, high concentrations of BrdU do not stabilize the SCE frequency in the rat lymphocyte culture system. However, high BrdU concentrations (⩾ 25 μM) did affect adversely the cells in culture as evidenced by increased chromosome breakage, poor chromosome spreading and morphology, and up to an 8‐fold reduction in mitotic activity. At BrdU concentrations ⩾ 33μM, the mitotic indices were depressed (2.4‐0.7%) at all WBC concentrations, and cell cycle delay was evident. Inoculum volumes ⩾ 0.4 ml, necessitated by low WBC counts in the animal, resulted in reduced mitotic activity and in some cases culture failure. Thus, we recommend the use of 2 μM BrdU and the addition of 1 × 106 WBCs/2 ml culture from animals with WBC counts ranging from 4–7 × 106/ml to ensure adequate mitotic activity and stable baseline SCE frequencies.
Experimental design and statistical analysis considerations for in vitro mammalian cell transformation assays with BALB/3T3 cells
Authors: Whorton Elbert B. , Ward Jonathan B. , Morris Debra L. 
Published: February 2007

AbstractMany mammalian cell assays testing for mutagenic activity have common features which cause statistical estimation and analysis problems. Such assays measure the number of cell alterations occurring in a plate containing an unknown number of cells at risk. The number of cells at risk can be estimated from a parallel cytotoxicity study. While the Poisson distribution has been assumed to apply to standardized frequencies, this is questioned. The failure of standardized frequencies to follow a Poisson distribution is attributed to the relatively small and dosage‐dependent number of susceptible cells per plate. A minimum number of such cells per plate or random cluster of plates has been determined for each dose so that the measured variable approximates a Poisson distribution. A transformation is suggested to achieve reasonable normality and variance equality, thereby allowing the use of parametric analysis of variance and regression methods and an estimation of required sample sizes.
Influence of caffeine on mutations induced by nitrosoguanidine in salmonella typhimurium tester strains
Authors: Levin R. E. 
Published: February 2007

AbstractStrains deficient in recombinational repair (recA−) failed to be reverted by MNNG. Caffeine was found to efficiently repress MNNG‐induced reversions with proficient and deficient (uvrB−) excision repair strains. The presence of the resistance plasmid pKM 101 had no influence on the effectiveness of caffeine.
Isolation of streptomycin‐dependent strains from salmonella typhimurium TA98 and TA100 and their use in mutagenicity tests
Authors: Kada T. , Aoki K. , Sugimura T. 
Published: February 2007

AbstractStreptomycin‐dependent (SMd) mutant strains of Salmonella typhimurium TA98 and TA 100 were isolated. A highly sensitive detection system was obtained by using these SMd derivatives for the SMd — SMind mutation. The system was available for testing the mutagenicities of samples containing histidine, such as food.
Induction and expression of mutations at multiple drug‐resistance marker loci in Chinese hamster ovary cells
Authors: Adair Gerald M. , Carver June H. 
Published: February 2007

AbstractWe have observed quantitative and qualitative differences in the mutability and mutagen‐specificity of various drug‐resistance marker loci in Chinese hamster ovary (CHO) cells, which suggest that mammalian gene loci may differ in their relative mutability by a given mutagenic agent. We have used the CHO‐AT3–2 multiple‐marker mutagenesis assay system to examine the dose‐dependent induction and kinetics of expression of mutations at four well‐characterized, drugresistance marker loci, after treatment with chemical agents which produce various types of DNA damage. The CHO‐AT3–2 subline allows simultaneous quantitation and direct comparison of induced mutation frequencies at the hgprt, oua (Na+/K+ATPase), aprt, and tk loci. The agents tested in this study included ethyl methanesulfonate, methyl methanesulfonate, mitomycin C, ICR‐191, benzo[a]pyrene, and dimethylnitrosamine. The expression kinetics and optimal expression times for each drug‐resistance marker were determined in dose‐response experiments in which cells from mutagen‐treated populations were plated at 1‐2‐day intervals over a period of 10 days following mutagenesis. Comparison of induced mutation frequencies for each drug‐resistance marker after mutagen treatments yielding equivalent cell survivals (equitoxic doses resulting in relative cell survivals of 0.37) revealed locus‐specific differences in the relative mutagenicities of the agents tested. These results indicate that the apparent mutagenicity of a particular agent at a single genetic locus may not necessarily be an accurate indicator of that agent's mutagenic potential for the genome as a whole.
Comparative mutagenicity of a coal combustion fly ash extract in salmonella typhimurium and chinese hamster ovary cells
Authors: Li A. P. , Clark C. R. , Hanson R. L. , Henderson T. R. , Hobbs C. H. 
Published: February 2007

AbstractThe dichloromethane extract of a coal combustion fly ash sample obtained from an experimental fluidized bed coal combustor was tested for mutagenicity in Salmonella typhimurium and cultured Chinese hamster ovary (CHO) cells. The extract was directly mutagenic in S typhimurium strain TA98 and the nitroreduc‐tase deficient strains TA98NR and TA98/1,8DNP6. The mutagenicity observed in TA98NR and TA98/1,8DNP6 was lower than that in TA98. Addition of exogenous Aroclor 1254‐induced rat liver supernatant (liver S9) decreased the bacterial mutagenicity of the extract. A different mutagenic response was observed in CHO cells. In the absence of liver S9, although the extract was cytotoxic to CHO cells, no significant mutagenicity was observed. Addition of exogenous liver S9 decreased the cytotoxicity and increased the mutagenicity at both Na+‐K+‐ATPase and hypoxanthine‐guanine phosphoribosyl transferase (HGPRT) gene loci in CHO cells. Using gas chromatography/mass spectrometry (GC/MS) and tandem quadruple mass spectrometry, a number of polynuclear aromatic hydrocarbons (PAHs) and nitrated PAHs (nitro‐PAHs) were tentatively identified and quantitated. A possible explanation of the difference in bacterial and mammalian mutagenicity of the extract is that the bacterial mutagenicity was induced by the nitro‐PAHs that are potent bacterial mutagens and mammalian mutagenicity was induced by both PAHs and nitro‐PAHs that are promutagens.
Chromosomal aberrations and delays in cell progression induced by X‐rays in tradescantia clone 02 meristems
Authors: Geard Charles R. 
Published: February 2007

AbstractIn root meristems of Tradescantia clone 02 (developed by Sparrow and his colleagues for mutation studies), X‐rays interfere with the progression of cells through the cell cycle and induce chromosomal aberrations in a dose‐dependent manner consistent with linear‐quadratic kinetics. Sequential mitotic cell accumulations after irradiation indicate that sensitivity to aberration induction is probably greatest in cells from late S to early G2, with chromatid interchanges the most frequent aberration type and all aberrations consistent with initiation from the interaction between two lesions. The ratio of the coefficients in the linear (α) and the quadratic (β) terms (α/β) is equal to the dose average of specific energy produced by individual particles in the site where interaction takes place. The ratio α/β for chromosomal aberrations is similar to that previously found for X‐ray‐induced mutation in Tradescantia stamen hairs, supporting the proposal that radiation‐induced mutational events are due to chromosomal aberrations with interaction distances of about 1 μm. Abrahamson and co‐workers have noted that both α/β ratios appear to be related to nuclear target size and are similar for chromosomal and mutational endpoints in the same organism. These findings support this concept; however, it is apparent that any situation which diminishes yield at high doses (eg, mitotic delay) will primarily affect the β component, resulting in low assessments of interaction site diameters.
Penetration of AF‐2 and 4NQO into multicell spheroids
Authors: Olive Peggy L. , Durand Ralph E. 
Published: February 2007

AbstractThe mutagenicity of 4NQO and AF‐2 was evaluated in a multicell system, Chinese hamster V79 spheroids, in order to determine the effects of drug delivery and metabolism on toxicity and mutagenicity. Both 4NQO and AF‐2 undergo metabolic reduction of the nitro group to produce toxic intermediates. However, 4NQO is metabolized under oxic as well as hypoxic conditions, while AF‐2 is reduced predominantly under hypoxia. This difference is apparently responsible for the observed pattern of toxicity and mutagenicity towards cells of large spheroids. Fluorescence microscopy revealed that 4NQO fluorescence localizes primarily in external (oxic) cells while AF‐2 can penetrate further into the hypoxic region of spheroids. Although 4NQO is a far more potent single cell mutagen than AF‐2 for equimolar exposures of single cells, the internal cells of spheroids exposed to 7.5 μg/ml of either agent under hypoxia were more readily mutated by AF‐2 than by 4NQO.
The kinetics of in vivo sister chromatid exchange induction in mouse bone marrow cells by alkylating agents: Cyclophosphamide
Authors: Charles James L. , Jacobson‐Kram David , Borzelleca Joseph F. , Carchman Richard A. 
Published: February 2007

AbstractAdministration of cyclophosphamide (5, 10, 20 and 25 mg/kg body weight) to male CD‐I mice 2 hr after subcutaneous implantation of a 5‐bromo‐2′‐deoxyuridine (BrdUrd) pellet (55 mg) resulted in a dose‐dependent increase in sister chromatid exchanges (SCE) in bone marrow cells. Treatment with cyclophosphamide (15 mg/kg body weight) at the time of BrdUrd implantation and 2, 6.5, and 13 hr post‐BrdUrd implantation resulted in the induction of approximately 19 SCE/cell indicating that the bone marrow SCE response was independent of the time of administration. Treatment with cyclophosphamide (15 mg/kg body weight) at 26, 19, 13, and 6 hr prior to BrdUrd implantation resulted in baseline SCE (3.3 SCE/cell) at 26 hr with an increasing number of SCE/cell with decreasing time prior to BrdUrd implantation.These results compare favorably with those obtained by Kram et al [1981] with mitomycin C (MMC) using a similar protocol. The time‐dependent induction of SCE is qualitatively similar for CP and MMC, both of which are bifunctional alkylating agents metabolically activated by oxidation and reduction, respectively, and suggests that these two compounds may induce SCE by a similar mechanism.
Comparison of rat and hamster hepatocyte primary culture/DNA repair assays
Authors: Kornbrust Douglas J. , Barfknecht Thomas R. 
Published: February 2007

AbstractPrevious studies have demonstrated marked differences in the capacity of hepatocytes from rats or hamsters to mediate the metabolic activation of chemical carcinogens to genotoxic (ie, mutagenic) products. Thus far, very few investigations of species differences in DNA repair have been performed. Therefore, a comparison of the relative extent of DNA repair elicited by various genotoxic chemicals in rat and hamster hepatocytes was conducted, using the hepatocyte primary culture/DNA repair (HPC/DR) assay. Of the 11 chemicals tested, eight were more potent in inducing DNA repair in hamster hepatocytes than in rat hepatocytes. Dimethylnitrosamine, diethylnitrosamine, 2‐acetylaminofluorene, 9‐aminoacridine, pararosaniline hydrochloride, 1‐naphthylamine, benzidine and 1,2:3,4‐diepoxybutane were all active in hamster hepatocytes at a concentration at least ten times less than the lowest effective concentration in rat hepatocytes. The direct‐acting alkylating agent, methylmethane sulfonate, was equipotent in inducing DNA repair in both rat and hamster hepatocytes, indicating that the differences in DNA repair observed for the other chemicals were probably not a result of species differences in DNA repair capacities. In contrast, 1‐nitropyrene produced a greater DNA repair response in rat hepatocytes than hamster hepatocytes, while the bacterial mutagen 3‐(chloromethyl)pyridine hydrochloride was inactive in both hepatocyte systems. These studies demonstrate the feasibility of using hamster hepatocytes in the HPC/DR assay and illustrate the utility of performing the assay with hepatocytes from more than one species.
Enhanced sensitivity of the C3H/10T1/2 cell transformation system to alkylating and chemotherapeutic agents by treatment with 12‐O‐tetradecanoylphorbol‐13‐acetate
Authors: Frazelle Janet H. , Abernethy Diane J. , Boreiko Craig J. 
Published: February 2007

AbstractThe failure of the C3H/10T1/2 cell transformation system to respond to numerous known carcinogens has limited its applications for the detection and study of cancer‐causing substances. Recent studies have found, however, that some carcinogens function as initiating agents for the process of transformation in these cells. Treatment with such agents is generally not sufficient to transform low‐density asynchronous cultures of C3H/101/2 cells, but morphologic transformation will occur if such cultures are subsequently exposed to the potent tumor promoter 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). In the present study, the ability of TPA to enhance transformation was examined in cultures treated with a variety of chemical agents. The addition of TPA after chemical treatment enhanced the transformation of these cells by methylmethanesulfonate, ethylmethanesulfonate, N‐methyl‐N′‐nitro‐N‐nitrosoguanidine, N‐nitrosomethylurea, N‐nitrosoethylurea, mitomycin C, 5‐fluorodeoxyuridine, and 5‐azacytidine. Treatment with amethopterin or benzo(e)pyrene did not produce significant numbers of foci in the presence or absence of TPA. TPA inhibited transformation by high concentrations of 3‐methylcholanthrene and benzo(a)pyrene. Thus, numerous carcinogens function as initiating agents for these cells and the presence of TPA can dramatically increase the sensitivity of this cell transformation system.
Mutagenicity testing of high performance liquid chromatography fractions from wood stove emission samples using a modified Salmonella assay requiring smaller sample volumes
Authors: Alfheim Ingrid , Becher Georg , Hongslo Jan K. , Ramdahl Thomas 
Published: February 2007

AbstractOrganic extracts of emissions from wood combustion have been fractionated by high performance liquid chromatography (HPLC) into 25–28 fractions. Each fraction was tested for mutagenic activity in a modified Ames Salmonella/microsome bioassay requiring one‐third of the test volumes needed for the ususal test. Direct mutagenic activity was noted predominantly in the most polar fractions, whereas indirect mutagenic activity was associated with the fractions containing polycyclic aromatic hydrocarbons (PAH) and with polar fractions probably consisting of aza‐arenes and aromatic amines.
Review: Putative Mutagens and Carcinogens in Foods. V. Cycad azoxyglycosides
Authors: Hoffmann George R. , Morgan Robin W. 
Published: February 2007

AbstractCycasin is a member of a family of azoxyglycosides produced by cycads. It is mutagenic and carcinogenic only when deglucosylated to release its principal metabolite, methylazoxymethanol (MAM). Methylazoxymethanol is also the aglycone of other cycad azoxyglycosides and is responsible for their toxicologic properties. The way in which people can be exposed to cycad azoxyglycosides is through the consumption of foods prepared from cycads. MAM induces genetic alterations in various test systems in bacteria, yeast, plants, Drosophila, and mammalian cells. An important aspect of the biological activities of cycasin and MAM is the intimate connection between their metabolism and their toxicologic effects. In adult mammals, the deglucosylation of cycasin is catalyzed only by enzymes of the microflora of the gut. Cycasin is therefore active when administered orally but not when administered parenterally. In contrast, MAM is active regardless of the route of exposure. Major uncertainties remain regarding the intermediates generated from MAM spontaneously and metabolically. More knowledge of these intermediates is required for a better understanding of the molecular mechanisms underlying the toxicity of cycasin, MAM, and related compounds.
Somatic mutation and recombination test in Drosophila melanogaster
Authors: Graf U. , Würgler F. E. , Katz A. J. , Frei H. , Juon H. , Hall C. B. , Kale P. G. 
Published: February 2007

AbstractA novel test system for the detection of mutagenic and recombinogenic activity of chemicals is described in detail. Drosophila melanogaster larvae trans‐heterozygous for the mutations multiple wing hairs (mwh) and flare (fir) are exposed to the test compounds for various periods of time ranging from 96 hr to 1 hr. Induced mutations are detected as single mosaic spots on the wing blade of surviving adults that show either the multiple wing hairs or flare phenotype. Induced recombination leads to mwh and fir twin spots and also to a certain extent, to mwh single spots. Recording of the frequency and the size of the different spots allows for a quantitative determination of the mutagenic and recombinogenic effects. This and earlier studies with a small set of well‐known mutagens indicate that the test detects monofunctional and polyfunctional alkylating agents (ethyl methanesulfonate, diepoxybutane, mitomycin C, Trenimon), mutagens forming large adducts (aflatoxin B1), DNA breaking agents (bleomycin), intercalating agents (5‐aminoacridine, ICR‐170), spindle poisons (vinblastine), and antimetabolites (methotrexate). In addition, the test detects mutagens unstable in aqueous solution β‐propiolactone), gaseous mutagens (1,2‐dibromoethane), as well as promutagens needing various pathways of metabolic activation (aflatoxin B1, diethylnitrosamine, dimethylnitrosamine, mitomycin C, and procarbazine). The rapidity and ease of performance as well as the low costs of the test necessitate a high priority for validation of this promising Drosophila short‐term test.