Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Mutagenesis assay”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1983

Effect of incubation and activation conditions on the hepatocyte-mediated plate incorporation and preincubation Salmonella typhimurium mutagenesis assays.

Primary cell-mediated microbial mutagenesis assays have been shown to be useful in detecting specific target organ genotoxic activity. The lack of a standard protocol for these assays, however, makes interlaboratory comparisons difficult. In order to standardize the hepatocyte-mediated Salmonella typhimurium mutagenesis assay, incubation and activation conditions for the plate incorporation and preincubation assays were examined using two aromatic amines, 2-aminofluorene (AF) and 2-acetylaminofluorene (AAF). Direct comparison of two preincubation protocols demonstrated the necessity for the hepatocytes to be present during the two- to three-day plate incubation period. An examination of various preincubation times showed relatively minor differences between 15 and 90 minutes. The preincubation and plate incorporation protocols were directly compared using both hamster and rat hepatocytes. For both preincubation and plate incorporation, the optimum concentration of hepatocytes was shown to be 1 X 10(6)/plate. Direct evaluation of various hepatocyte-mediated bacterial protocols should facilitate future interlaboratory comparisons using a more standardized procedure.

2-Acetylaminofluorene↗
PubMed1980

Definition of conditions for the detection of genotoxic chemicals in the adult rat-liver epithelial cell/hypoxanthine-guanine phosphoribosyl transferase (ARL/HGRPT) mutagenesis assay.

Conditions for the detection of genotoxic chemicals in the adult rat-liver epithelial cell/hypoxanthine-guanine phosphoribosyl transferase (ARL/HGPRT) mutagenesis assay have been defined. These included (1) a 3-day exposure to activation-dependent carcinogens; (2) a minimum of 14 days for induced mutant expression; (3) seeding density of 1 x 10(4) cells per cm2 for selection of mutants; (4) use of 6-thioguanine and (5) acceptance of genotoxicity of test chemicals if induced mutant incidence is significantly above that of the parallel run control and beyond the 98% confidence limits of the mean of the population spontaneous mutant incidence. With this protocol, the ARL/HGPRT mutagenesis assay has the capacity to activate representative members of the mycotoxin, aminoazo dye, aromatic amine and nitrosamine-types of carcinogens. This assay, offering additional metabolic parameters through intrinsic metabolic capability and providing a reliable end-point of clear biologic significance serves as a useful supplement to the Salmonella/microsome bacterial mutagenesis assay in a battery for the detection of genotoxic chemicals.

Animals↗
PubMed1987

Mutagenicity of L-azaserine for V79 cells in a pancreatic acinar cell-mediated mutagenesis assay.

The mutagenicity of azaserine was determined in a pancreatic acinar cell-mediated mutagenesis assay using V79 cells as the responder cell line. The mutation frequency of V79 cells was increased in direct culture with azaserine as well as in coculture with rat and hamster pancreatic acinar cells. Although slightly higher mutation frequencies were seen with coculture, the mutation frequency induced by azaserine in coculture was not significantly enhanced over that observed in direct culture. Thus, azaserine cannot be used as a positive control to monitor the level of acinar cell metabolism in such cell-mediated mutagenesis assays. Statistical analysis suggested that hamster acinar cell cocultures were more effective at increasing the mutation frequency of azaserine as compared to rat acinar cell cocultures. Hamster acinar cell cocultures, but not rat acinar cell cocultures, increased the mutagenicity of azaserine in a dose-response fashion. These results suggest that azaserine may be a pancreatic carcinogen for the hamster as well as the rat.

Animals↗
PubMed1995

Intralaboratory optimization and standardization of mutant screening conditions used for a lambda/lacI transgenic mouse mutagenesis assay (I).

A lambda/lacI shuttle vector transgenic mouse mutagenesis assay has been optimized and standardized for reproducible mutant detection. The mutagenic endpoints are blue lacI- phage plaques on a bacterial lawn resulting from the de-repression of beta-galactosidase activity acting on the chromogenic substrate X-gal. Non-mutant lacI phage plaques remain colorless. Factors demonstrated to affect mutant detection include X-gal concentration per assay tray, plaque density per assay tray, pH of plating agar, incubation time at 37 degrees C and the use of a red translucent screening filter over a light source to enhance mutant plaque visibility. In vivo mutant frequencies for liver in untreated animals using standard protocols and internal controls were repeatable in separate experiments using lambda/lacI B6C3F1 mice (4.3 +/- 1.2 x 10(-5) and 4.1 +/- 0.8 x 10(-5)). These studies analyze the use of internal controls to monitor the level of mutant phage plaque detection in a given experiment and evaluate the repeatability of observed mutant frequencies obtained when using standardized procedures.

Agar↗
PubMed1977

In vitro mutagenesis assays as predictors of chemical carcinogenesis in mammals.

In vitro microbial mutagenesis assays coupled with mammalian activation systems offer promising technique to screen chemicals for their potential carcinogenic activity. The correlation between mutagenic and carcinogenic properties for a large array of chemicals is approximately 0.9. The best correlation exists for those carcinogens which are themselves highly electrophilic or produce electrophilic metabolites. Correlation between mutagenicity and carcinogenicity for hormonal, metallic, or physical carcinogens has been disappointing but not unexpected based on their proposed mechanisms of action. In addition to the application of in vitro mutagenesis techniques to screening chemicals for the identification of potential carcinogens, they are useful tools for investigating genetic, biochemical, and pharmacologic properties of different animal species. Studies with the chemical carcinogen dimethylnitrosamine have been conducted and show a functional relationship between mutagenesis and carcinogenesis. The assays can also be conducted using activation systems prepared from the tissues of any mammalian species. This permits a direct assessment of phylogenic extrapolation by comparing the metabolic activation capabilities of tissues from several mammalian species, including human samples. The advantages of mutagenicity testing are the short period of time required for results, the high sensitivity of the assay (microgram of nanogram quantities of chemicals can be used), and the fact that the ultimate agent can be detected biologically without first necessitating chemical identification and isolation. It appears from current studies that in vitro mutagenesis techniques may well open new avenues of investigation into some old toxicologic problems.

Aging↗
PubMed1986

Activation of the colon carcinogen 1,2-dimethylhydrazine in a rat colon cell-mediated mutagenesis assay.

Suspensions of rat colon epithelial cells metabolized the potent colon carcinogen, 1,2-[14C]dimethylhydrazine (DMH), into 14C-labeled, alkali-soluble volatile products, presumably CO2. The colon cell suspensions, however, were less effective than rat hepatocyte suspensions. In addition, we used a cell-mediated mutagenesis assay to test rat colon epithelial cells grown from tissue explants for their ability to metabolize DMH into products mutagenic for human P3 teratoma cells. Mutagenesis in the P3 cells was indicated by an acquired resistance to 6-thioguanine. Cocultivation of the colon cells with the P3 cells in the cell-mediated assay resulted in mutagenesis, whereas in the absence of the colon cells, no mutagenesis by DMH was observed. Similar results were obtained in a hepatocyte-mediated mutagenesis assay. Colon cells were also able to activate another carcinogen, benzo(a)pyrene, into products mutagenic for the P3 cells. Individual epithelial clonal populations isolated from the colon cultures grown from tissue explants, however, expressed different capacities to activate DMH and benzo(a)pyrene into mutagens, and a high degree of DMH activation by cells from a colon clone was not necessarily associated with a similar degree of benzo(a)pyrene activation. Our results indicate that the colon itself contains epithelial cell types capable of effectively converting DMH into mutagenic (and presumably carcinogenic) products without necessarily involving intermediary metabolism by hepatocytes as previously thought.

1,2-Dimethylhydrazine↗
PubMed1988

Evaluation of the L5178Y mouse lymphoma cell mutagenesis assay: interlaboratory reproducibility and assessment.

The L5178Y mouse lymphoma cell mutagenesis assay is used to detect the mutagenic activity of chemicals in a mammalian cell system. To evaluate this assay we compared the results of assays performed independently on 63 chemicals by laboratories at SRI International and Litton Bionetics, Inc. The two laboratories used similar protocols. The solvent and positive control mutant frequencies and cloning efficiencies obtained by the two laboratories were similar, which justified the use of the same quality-control criteria and analytical procedures for analyzing the results from both laboratories. The rate of concordance between the two laboratories was 92% for tests in the absence of S9 activation and 95% for tests in its presence. The results of the assays agreed for 57 of the 63 chemicals; three chemicals could not be compared because there were questionable calls in at least one of the laboratories; the results disagreed for the three remaining chemicals. The concordance rate for these overall assay evaluations was 95%. The interlaboratory concordance rates were similar to concordance rates for replicate experiments within the laboratories (96% at LBI, 94% at SRI). The mouse lymphoma cell mutagenicity results are concordant with the rodent chronic assay results in 78% of 50 chemicals and with the Salmonella assay results in 79% of 56 chemicals. Fifteen carcinogens were examined for genotoxic effects in mouse lymphoma, Salmonella, Chinese hamster ovary (CHO) chromosomal aberration, and CHO sister chromatid exchange assay. Eight of these were positive in all four assays. Of the seven noncarcinogens that were tested in these four assays, none was negative in all four. The main conclusion to be drawn from this study is that the mouse lymphoma cell forward mutation assay, as performed and evaluated in this study, detects chemical mutagenicity in a manner that is highly consistent with other genetic endpoints as well as rodent carcinogenicity studies. Thus the assay quality control and response criteria established in this study led not only to a high degree of reproducibility but also to an apparently reliable detection of mutagenic activity.

Animals↗
PubMed1983

Keratinocyte cell-mediated mutagenesis assay: correlation with in vivo tumor studies.

A murine keratinocyte cell-mediated mutagenesis assay was characterized and examined as an in vitro model system for studying the biotransformation of promutagens/procarcinogens by mouse skin. The assay used living cultured newborn SENCAR keratinocytes for the metabolic activation of promutagens and Chinese hamster lung V-79 fibroblasts for detection of resulting mutagens. Mutations at, or affecting, the hypoxanthine-guanine phosphoribosyltransferase locus were scored by resistance to 6-thioguanine. The relative mutagenicities of several polycyclic aromatic hydrocarbons (PAHs) in the cell-mediated assay correlated with the in vivo skin tumorigenicity of the PAHs determined in a two-stage carcinogenesis protocol. Metabolic activation of the promutagenic PAHs to ultimate mutagens was dependent upon the presence of the cultured keratinocyte feeder layer. 7,8-Benzoflavone, a potent inhibitor of 7,12-dimethylbenz[a]anthracene (DMBA)-dependent initiation in mouse skin, inhibited DMBA-dependent mutagenesis in the cell-mediated assay in a concentration responsive manner. The non-PAH promutagens, dimethylnitrosamine (DMN) and sterigmatocystin (STC) were both activated by cultured keratinocytes to cytotoxic derivatives. DMN was neither mutagenic in the cell-mediated assay nor tumorigenic in mouse skin when tested in a two-stage carcinogenesis protocol. STC was weakly mutagenic and tumorigenic in mouse skin.

Animals↗
PubMed1980

Bioactivation of dimethylnitrosamine in intrasanguinous host-mediated assay and its association with in vitro mutagenesis assays.

These studies have revealed the usefulness of in vivo intrasanguine host-mediated assay (HMA) to detect point mutations. Mutations were found to occur at a significant rate in Salmonella typhimurium G-46 employed as indicator organisms recovered from liver, lung, kidney and spleen of DMN-treated animals compared to negative control animals. These differences were true for both male and female animals. The number of Salmonella typhimurium G-46 recovered from the testes was not large enough to make a valid judgment about mutations occurring in testes. The results from in vitro studies do not match with the in vivo host-mediated assay results for mutants occurring in spleen from the male and the female mice. The results also do not correlate for in vitro and in vivo studies involving female kidneys. These results suggest there may be no one-to-one correlation between the organ bioactivation in vitro and in vivo, and predictions of in vivo target organ cannot always be made from in vitro studies with isolated microsomal enzymes.

Animals↗
PubMed2006

Development of a novel site-specific mutagenesis assay using MALDI-ToF MS (SSMA-MS).

We have developed and validated a novel site-specific mutagenesis assay, termed SSMA-MS, which incorporates MALDI-ToF mass spectrometry (MALDI-MS) analysis as a means of determining the mutations induced by a single DNA adduct. The assay involves ligating an adducted deoxyoligonucleotide into supF containing pSP189 plasmid. The plasmid is transfected into human Ad293 kidney cells allowing replication and therefore repair or a mutagenic event to occur. Escherichia coli indicator bacteria are transformed with recovered plasmid and plasmids containing the insert are identified colormetrically, as they behave as frameshift mutations. The plasmid is then amplified and digested using a restriction cocktail of Mbo11 and Mnl1 to yield 12 bp deoxyoligonucleotides, which are characterized by MALDI-MS. MALDI-MS takes advantage of the difference in molecular weight between bases to identify any induced mutations. This analysis method therefore provides qualitative and quantitative information regarding the type and frequency of mutations induced. This assay was developed and validated using an O(6)-methyl-2'-deoxyguanosine adduct, which induced the expected GC-->AT substitutions, when replicated in human or bacterial cells. This approach can be applied to the study of any DNA adduct in any biologically relevant gene sequence (e.g. p53) in human cells and would be particularly amenable to high-throughput analysis.

Cell Line↗
PubMed1981

Stability of activating systems for in vitro mutagenesis assays: enzyme activity and activating ability following long-term storage at - 85 degrees C.

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 degrees 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 biphenyl-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 activating systems are used in in vitro tests to screen for mutagens.

Animals↗
PubMed1981

A "spiral test" applied to bacterial mutagenesis assays.

A new procedure (the spiral test) has been set up and validated for the distribution of chemicals in bacterial mutagenesis assays. This method involves the use of a special instrument (spiral plater), which dispenses, along a spiral track, decreasing volumes of liquid samples, from the near centre to the periphery of a rotating agar plate. A gradient of concentration of a compound up to about 1500:1 is thus formed on a single plate. The activity of 18 mutagens of various potencies and chemical classes was checked in the Salmonella/microsome test by dispensing their solutions either on the surface of top agar (method A) or of the minimal-glucose agar medium, before the addition of molten top agar incorporating bacteria and eventually S9 mix (method B). Compared with the spot test, the gradient of concentration of a compound produced by the spiral diluter was much wider and more gradual. Even nondiffusible chemicals (e.g. benzo[a]pyrene and benz[a]anthracene) were efficiently detected in the spiral test, as well as very weak (e.g. mebanazine and trimethylphosphate) or borderline (e.g. perylene, 1,1-dimethylhydrazine and procarbazine) mutagens, which were negative in the spot test. Method B was at least as sensitive as the plate-incorporation test, such a goal being achieved in a single plate instead of in serial plates. Technical problems made method A less sensitive, but it was more efficient in detecting unstable mutagens (e.g. beta-propiolactone). Like the plate test, the spiral test appeared to be suitable for a semi-quantitative assessment of mutagenicity data, and was efficient in demonstrating both the activation of promutagens and the deactivation of some directly acting mutagens. Preliminary assays were also carried out with repair-proficient (WP2) or -deficient (TM1080: lexA-/polA-/R391, and CM871: lexA-/uvrA-/recA-) trp- strains of E. coli.

Culture Media↗
PubMed1990

Assessment of the mutagenic potential of ethanol auto engine exhaust gases by the Salmonella typhimurium microsomal mutagenesis assay, using a direct exposure method.

The mutagenic activity of the new Brazilian fuel, ethanol, was determined by employing the Salmonella typhimurium microsomal mutagenesis assay (TA97, TA98, TA100, TA102, and TA104) and a direct exposure method. This methodology was first used to determine the mutagenic activity of gasoline, revealing mutagenic activity of base-pair substitution without any need for metabolic activation, indicating the presence of direct-action mutagens. Experiments with ethanol suggest an indirect mutagenic activity of the oxidant type. The exposure system was considered suitable for future studies of gaseous mixtures.

Animals↗
PubMed1996

Towards validation of the Big Blue transgenic mouse mutagenesis assay: the mutational spectrum of ex vivo pinpoint mutant plaques.

To explore further the origin of spontaneous mutations recovered with the Big Blue transgenic mouse mutagenesis assay, the spectrum of ex vivo mutations from pinpoint mutant plaques was determined and compared with the spectrum of putatively mouse-derived mutations from circular, mutant plaques. The entire lacI gene and lacZ operator region from 62 pinpoint blue plaques was sequenced. The observed mutational spectrum of pinpoint mutants differed significantly from that seen in circular mutants (p < 0.0001). Only four percent of the mutations were transitions at CpG sites whereas this type of mutation was the most common (35%) in circular mutants. Microdeletions/microinsertions were seen more frequently in pinpoint mutants relative to circular mutants. Four base pair deletion/insertion events at the E. coli hotspot tandem repeats were seen in 10 of 62 (16%) pinpoint mutants and minor hotspots of mutation were observed at bp 141 and 1110. The mutational spectrum of pinpoint mutants provides further evidence that most circular mutants originate in mouse.

Age Factors↗
PubMed1985

Mutagenesis assays of human amniotic fluid.

Extracts of amniocentesis samples from 144 women were tested for the presence of mutagenic substances using tester strain TA1538 in the Ames Salmonella/mammalian-microsome mutagenicity test. Because the volume of amniotic fluid in these samples was limited (generally less than 10 ml), we investigated modifications of this mutagenesis assay that could increase its ability to detect effects from small quantities of test material. Using mutagenicity in samples of urine from smokers as a model, it appeared that improved ability to detect small amounts of mutagen could be obtained by reducing volumes of media and reagents while keeping the amount of test sample constant. This modification resulted in a test procedure capable of readily detecting mutagenicity in volumes of urine from smokers that were smaller than the volumes of amniotic fluid available. Tests of amniotic fluid extracts by this modified procedure showed small increases in revertants, about 50% above dimethylsulfoxide solvent control values. Results of procedures to control for technical factors possibly contributing to these increases suggested that the increased values could not be readily explained by contamination of test samples with mutagens during the extraction procedure. They also were not explained by alterations in spontaneous numbers of revertants associated with changes in the density of bacterial lawn growth. The increases suggest the presence of small amounts of mutagenic material in many of the amniotic fluid samples. At the doses employed, mutagenic activity in these samples was not associated with maternal smoking.

Amniotic Fluid↗
PubMed1986

Detection of occupational and environmental exposures by bacterial mutagenesis assays of human body fluids.

Assays of human body fluids provide a means to document human exposure to mutagens in the environment. In contrast to measurements of ambient levels, these assays demonstrate absorption of mutagens and provide estimates of minimal systemic doses. For most studies reviewed here, specimens of urine were concentrated by adsorption to columns of XAD-2 resin or by liquid partition extraction prior to the mutagenesis assays. The resulting extracts most commonly were analyzed for mutagenicity using the Salmonella/mammalian microsomal plate assay. Less frequently used assays included bacterial fluctuation tests instead of the plate assay and assays for the induction of sister chromatid exchanges in cultured mammalian cells. In addition to reviewing literature reports where body fluids were tested, the advantages, disadvantages, and potential role of this approach will be briefly discussed and compared with other approaches to the identification of mutagenic hazards in the workplace.

Body Fluids↗
PubMed1979

DNA--benzo[a]pyrene adducts formed in a Salmonella typhimurium mutagenesis assay system.

The DNA adducts formed in Salmonella typhimurium when bacteria are incubated with radioactive benzo[a]pyrene and liver microsomal enzymes from several sources has been investigated. When enzyme preparations from Aroclor I254 or 3-methylcholanthrene induced C57BL/6N (B6) mice were used to mediate activation, the predominant product was an adduct between the 10 position of 7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and the N-2 position of deoxyguanosine. Similar results were obtained with human liver and with Aroclor-induced rat-liver enzyme preparations. This adduct is also the major DNA product previously found when human tissues or certain rodent cells were incubated with benzo[a]pyrene. On the other hand, when activation of benzo[a]pyrene was mediated by a phenobarbital-induced B6 mouse-liver enzyme preparation, the extent of binding was quite low and the profile of DNA adducts in S. typhimurium DNA was quite different. Thus, under appropriate conditions, the activation and DNA binding of benzo[a]pyrene inthe microsome mediated S. typhimurium mutagenesis assay generally resembles that seen in intact mammalian cells. Caution must be exercised, however, in the choice of microsome-activation systems.

Animals↗