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PubMed1976

Ten model mutagens evaluated by the micronucleus test.

The following ten mutagenic compounds were subjected to the micronucleus bone marrow test (MNT) in the mouse: cyclophosphamide (CTX), thiotepa (TT), vincristin (VCR), colcemid (COLC), adriamycin (AM), bleomycin (BM), cytosin arabinoside (ARA C), 6-mercaptopurine (6-MP), methotrexate (MTX) and 5-fluorouracil (5-FU). Dose-effect curves were established for all compounds. With the exception of CTX, COLC and AM, the drugs also were subjected to chromosome analyses on Chinese hamster fibroblasts in vitro. The MNT revealed loss of chromatin due to chromosome breakage and rearrangements by CTX, TT and AM, to breakage by ARA C, 6-MP, MTX and 5-FU, as well as loss of entire chromosomes caused by impairment of the spindle by VCR and COLC. With the exception of BM, the effects were demonstrable in the therapeutic dose range. The MNT, provided it is carried out by the methodology of the authors, not only reveals chromatin loss but permits important conclusions in regard to the proliferative state of the bone marrow and the specific time of action of the mutagens in the cell cycle. If arrest of the cell cycle occurs, as in the case of anti-metabolites MTX and 5-FU particularly, the routine scheme of investigation needs to be modified since micronucleated cells appear only after release of the metabolic block, i.e. after a delay of 24 h. The negative bone marrow results obtained with BM emphasize the importance of combining in vivo and in vitro tests.

Animals↗
PubMedDate not supplied

Micronucleus test on quinacrine dihydrochloride in mice: a comparison of dosage regimens.

Micronucleus induction by quinacrine dihydrochloride (Q) was tested in CD-1 male mice by single, double, and triple oral treatment(s) with 50 or 250 mg/kg. The mice were killed 24 h after the last treatment. Femoral marrow cells were analyzed on slides stained with Giemsa and acridine orange. Both staining methods gave similar results. The frequencies of micronucleated polychromatic erythrocytes (MPE) were marginally increased, in comparison with a concurrent negative control group, only in the triple treatment group of 250 mg/kg. There were, however, no big differences in MPE frequencies among the treatment regimens.

Animals↗
PubMed2000

Comparative evaluation of the in vitro micronucleus test and the comet assay for the detection of genotoxic effects of X-ray radiation.

The genotoxic effects of X-ray radiation on human lymphocytes were measured using the single cell gel electrophoresis (SCGE) assay (comet assay) and the cytokinesis-blocked micronucleus (CBMN) test; both were carried out in vitro on isolated human lymphocytes in order to compare the relationship and sensitivity of these two detecting methods. The radiation-doses were 0.00, 0.02, 0.05, 0.10, 0.25, 0.50, 1.00 and 2.00 Gy. In the comet assay, the average comet length (38.6+/-0.8 microm) of 0.05 Gy was significantly longer than that (29.4+/-1.1 microm) of 0 Gy (P<0.01), moreover, the average comet length increased with the dose of X-ray radiation. In the CBMN, both the average micronucleus rate (MN) and micronucleated cell rate (MNC) of 0.05 Gy were 11.5+/-4.5 per thousand, which showed no difference with that (7.5+/-0.5 per thousand) of 0 Gy (P>0.05). The lowest dose, which induced significant increase of average MN and MNC, was 0.25 Gy. The average MN and MNC rates increased with radiation-dose. The results showed that there was correlation between SCGE and CBMN, and the sensitivity of SCGE was significantly higher than that of CBMN.

Adult↗
PubMed2004

Fish as bioindicators to assess the effects of pollution in two southern Brazilian rivers using the Comet assay and micronucleus test.

Industrial effluents, agricultural runoff, and municipal wastewaters contain unknown substances and complex mixtures that are released into the environment and can lead to contamination of surface and subsurface waters. In the present report, we have used the alkaline Comet assay and the micronucleus (MN) test to detect the genotoxicity due to multiple sources of pollution in the peripheral blood of two native estuarine fish (mullet and sea catfish) and evaluated possible interactive genotoxic effects from multiple contaminants and the seasonal variation of the genotoxicity. Mullet and sea catfish were captured in the Tramandai and Mampituba Rivers in the southern Brazilian state of Rio Grande do Sul. Reference animals were obtained from the Armazem lagoon. Fish captured in the two estuaries during the four seasons over a period of 2 years had increased levels of DNA damage and MN frequencies relative to the reference fish. In general, the alkaline Comet assay was more sensitive to the genotoxicity of the river contaminants than the MN test. The Comet assay demonstrated significant differences in fish captured at different seasons and at the two river sites, while the MN test showed significant differences only for the annual average for mullet from both sites and fish from the control site. The increases in DNA damage appear to be related to the increase in the number of people in the towns close to the study areas during the warm spring and summer seasons. Although no specific cause-effect relationships were established, comparison of the chemical contaminants and physical variations in the rivers with the genotoxicity data indicate that there may be some association between hydrocarbons, metals, pH, and water temperature and the level of damaged cells observed in mullet and sea catfish from the Tramandai and Mampituba estuaries.

Animals↗
PubMed1996

Micronucleus test in erythrocytes of Barbus plebejus (Teleostei, Pisces) from two natural environments: a bioassay for the in situ detection of mutagens in freshwater.

Erythrocyte micronucleus frequencies in wild fish from two riverine environments and in fish reproduced and reared under controlled conditions (control group) were compared, with the aim to evaluate the suitability of the MN test for the in situ detection of mutagens in freshwaters. Fish were caught in different months in two rivers of central Italy which have different pollution levels. As indicator species, the barbel (Barbus plebejus) was chosen because of its ecological significance. Blood samplings were performed on wild fish immediately after capture and repeated at different time intervals on the same individuals, which were maintained in controlled conditions after capture. A total of 10,000 erythrocytes per specimen were scored. No significant differences in micronucleus frequencies were observed between the control group and fish from the unpolluted river (Mignone). A significantly higher frequency of micronuclei was observed in fish caught in the polluted river (Tiber), in comparison to both the controls and the Mignone river fish. No significant seasonal differences were observed. Barbels examined 50 and 100 days after capture presented a remarkable decrease in micronucleus frequency in comparison with the frequency observed in barbels at capture. The micronucleus test in fish erythrocytes was shown to be a sensitive bioassay for detecting mutagenic pollution in fresh water environments.

Animals↗
PubMed2002

Study of low-intensity 2450-MHz microwave exposure enhancing the genotoxic effects of mitomycin C using micronucleus test and comet assay in vitro.

OBJECTIVE: To determine the interaction between 2450-MHz microwaves (MW) radiation and mitomycin C (MMC). METHODS: The synergistic genotoxic effects of low-intensity 2450-MHz microwave and MMC on human lymphocytes were studied using single cell gel electrophoresis (SCGE) assay (comet assay) and cytokinesis-blocked micronucleus (CBMN) test in vitro. The whole blood cells from a male donor and a female donor were either only exposed to 2450-MHz microwaves (5.0 mW/cm2) for 2 h or only exposed to MMC (0.0125 microgram/mL, 0.025 microgram/mL and 0.1 microgram/mL) for 24 h; and the samples were exposed to MMC for 24 h after exposure to MW for 2 h. RESULTS: In the comet assay, the comet lengths (29.1 microns and 25.9 microns) of MW were not significantly longer than those (26.3 microns and 24.1 microns) of controls (P > 0.05). The comet lengths (57.4 microns, 68.9 microns, 91.4 microns, 150.6 microns, 71.7 microns, 100.1 microns, 145.1 microns) of 4 MMC groups were significantly longer than those of controls (P < 0.01). The comet lengths (59.1 microns, 92.3 microns, 124.5 microns, 182.7 microns and 57.4 microns, 85.5 microns, 137.5 microns, 178.3 microns) of 4 MW plus MMC groups were significantly longer than those of controls too (P < 0.01). The comet lengths of MW plus MMC groups were significantly longer than those of the corresponding MMC doses (P < 0.05 or P < 0.01) when the doses of MMC were > or = 0.025 microgram/mL. In the CBMN, the micronucleated cell (MNC) rates of MW were 5@1000 and 6@1000, which showed no difference compared with those (4@1000 and 4@1000) of controls (P > 0.05). The MNC rates of 4 MMC groups were 8@1000, 9@1000, 14@1000, 23@1000 and 8@1000, 8@1000, 16@1000, 30@1000 respectively. When the doses of MMC were > or = 0.05 microgram/mL, MNC rates of MMC were higher than those of controls (P < 0.05). MNC rates of 4 MW plus MMC groups were 12@1000, 13@1000, 20@1000, 32@1000 and 8@1000, 9@1000, 23@1000, 40@1000. When the doses of MMC were > or = 0.05 microgram/mL, MNC rates of MW plus MMC groups were much higher than those of controls (P < 0.01). MNC rates of 4 MW plus MMC groups were not significantly higher than those of the corresponding MMC doses. CONCLUSION: The low-intensity 2450-MHz microwave radiation can not induce DNA and chromosome damage, but can increase DNA damage effect induced by MMC in comet assay.

Antibiotics, Antineoplastic↗
PubMed1995

Genotoxicity of the herbicide fluchloralin on human lymphocytes in vitro: chromosomal aberration and micronucleus tests.

Cultured human lymphocytes were exposed to three different concentrations (2.5, 5.0 and 10.0 micrograms/ml) of fluchloralin for 24 and 48 h to assess chromosomal aberrations. A significant dose-dependent increase of chromatid type aberration was observed in these cells. Multiple aberrations (MA) were scored at all concentrations after 48 h treatment. To support these results we did micronucleus (MN) test using cytochalasin B to block cytokinesis. At lower concentrations (2.5 to 10.0 micrograms/ml) the frequency of MN induction was not significantly different. Higher concentrations of fluchloralin (20, 40 and 50 micrograms/ml) resulted in a significant dose dependent increase in number of micronucleated cells. This is the first report on genotoxic effects of fluchloralin in human cells.

Aniline Compounds↗
PubMed2005

Evaluation of liver and peripheral blood micronucleus assays with 9 chemicals using young rats. A study by the Collaborative Study Group for the Micronucleus Test (CSGMT)/Japanese Environmental Mutagen Society (JEMS)-Mammalian Mutagenicity Study Group (MMS).

We conducted simultaneous liver and peripheral blood micronucleus assays in young rats with seven rodent hepatocarcinogens-4,4'-methylenedianiline (MDA), quinoline, o-toluidine, 4-chloro-o-phenylenediamine (CPDA), dimethylnitrosamine (DMN), p-dimethylaminoazobenzene (DAB), and di(2-ethylhexyl)phthalate (DEHP)-and two mutagenic chemicals-kojic acid and methylmethanesulfonate (MMS). Quinoline, DMN, and DAB were positive in the liver assay, while o-toluidine, kojic acid, DAB, and MMS were positive in the peripheral blood assay. o-Toluidine, kojic acid, and DAB are reportedly negative in mouse bone marrow micronucleus assays, indicating a species difference. Our results revealed a correlation between micronucleus induction in hepatocytes and hepatocarcinogenicity. This technique can be useful for the detection of micronucleus-inducing chemicals that require metabolic activation, and it enables simultaneous comparison of the micronucleus-inducing potential of chemicals in the liver and peripheral blood in the same individual.

Aniline Compounds↗
PubMed1999

Genotoxicity studies on the azo dye Direct Red 2 using the in vivo mouse bone marrow micronucleus test.

The clastogenicity of the azo dye Direct Red 2 (DR2) has been investigated using the murine bone marrow micronucleus assay. A potent dose-dependent response was observed following oral gavage of DR2 up to 4 mg/kg, after which significant toxicity to the erythroid compartment was observed. The route of administration had a significant effect on the frequency of micronucleus formation: intraperitoneal injection was approximately two-fold less clastogenic than the equivalent dose delivered orally (p<0.05). The requirement for activation of DR2 by intestinal microflora was indicated by the fact that mice given acid-treated water prior to administration of DR2 showed a significant reduction (40%; p<0.001) in micronucleated polychromatic erythrocyte formation. The implications of these findings for the health and safety of occupationally exposed workers are discussed.

Animals↗
PubMedDate not supplied

[The micronucleus test in human exfoliative cells as a method for studying the action of mutagens/carcinogens].

The data concerning the application of micronucleus assay in human exfoliated cells have been analyzed in the review. These data have shown that the study of micronuclei in human exfoliated cells is very promising, sensitive and rapid method for detection of action of mutagens/carcinogens as well as antimutagens/anticarcinogens on human organism in vivo.

Carcinogens↗
PubMed2006

Increased cytogenetic damage in a zone in transition from agricultural to industrial use: Comprehensive analysis of the micronucleus test in peripheral blood lymphocytes.

A complex situation of chemical exposure has been described in México in a zone that is in transition from rural activities towards intensive industrialization, which has brought environmental pollution: chloroform, methylene chloride, indigo and toluene are some of the pollutants found in the Atoyac and Xochiac rivers. A biomonitoring study was planned in order to establish whether there was a biological effect due to the environmental situation. Communities where leukaemia and thrombocytopenic purpura cases have been reported were included in the study, as well as other communities where such cases have not been described. Three occupations were distinguished, according to chemical exposure: industrial workers, agricultural workers and workers in households, education and commerce. A comprehensive analysis in the micronucleus (MN) test was used to study genotoxicity biomarkers. Two metabolic polymorphisms were determined, namely, glutathione transferase mu1 (GSTM1) and theta1 (GSTT1), which are relevant when oxidative responses are involved. Increased genotoxic damage was found, including cells with >1 MN, >1 chromatin bud, and nucleoplasmic bridges. The genotoxic damage was differentially distributed in the regions studied, being more affected those that are closer to the Atoyac and Xochiac rivers, indicating an effect due to environmental exposure to the contaminants present in the rivers. Further characterization of the exposure regimes in these communities will be done in order to contribute to the alleviation of the health risks that environmental pollution is posing on the inhabitants of this area.

Adult↗
PubMed2006

SFTG international collaborative study on in vitro micronucleus test II. Using human lymphocytes.

This study on the in vitro micronucleus assay, comprising 11 laboratories using human lymphocytes, was coordinated by an organizing committee supported by the SFTG (the French branch of the European Environmental Mutagen Society). Nine coded substances were assessed for their ability to induce micronuclei in human lymphocytes in vitro, mitomycin C being used as a positive control. Cultures were exposed to the test substances for a short (early or late) time or for a long time, followed by a short or long recovery period, in the presence of cytochalasin B. Each chemical was evaluated, generally in two laboratories, using three treatment schedules at least twice. The data were assessed for acceptability, and then classified as negative, positive or equivocal. Two of seven genotoxic compounds, namely colchicine and bleomycin, clearly induced micronuclei. Reproducible results were difficult to obtain for some substances, which tended to be those acting at specific stages of the cell cycle. Cytosine arabinoside, diethylstilboestrol and 5-fluorouracil were classified as equivocal. Urethane and thiabendazole were classified as negative. The two presumed non-genotoxic compounds, mannitol and clofibrate, did not induce micronuclei. Repeat testing, exposing cells at both an early and late time after mitogenic stimulation, was needed to detect substances classified as equivocal. These results show the importance of achieving sufficient inhibition of nuclear division to avoid the possibility of missing an effect. The evaluation of micronuclei in mononucleated as well as binucleated cells was particularly useful to detect aneugens. There were no false positive results using lymphocytes, indicating a high specificity. It is concluded that the clastogenic or aneugenic potential in vitro of the substances tested was correctly identified in this study, but that refining the protocol to take into account factors such as the stages of the cell cycle exposed to the compound, or the duration of recovery would be likely to improve the sensitivity of detection using lymphocytes.

Adult↗
PubMed2005

Genotoxic potential of quinolone antimicrobials in the in vitro comet assay and micronucleus test.

The purpose of this study was to examine the genotoxicity of quinolone antimicrobials. We investigated the genotoxic potential of eight quinolones, namely nalidixic acid (NA), pipemidic acid (PPA), oxolinic acid (OA), piromidic acid (PA), enoxacin (ENX), ofloxacin (OFLX), norfloxacin (NFLX) and ciprofloxacin (CPFX), by the in vitro alkaline single-cell gel electrophoresis (comet) assay at pH>13. WTK-1 cells (mutant p53) were treated with each of the eight quinolones at 62.5-1000 microg/mL for 2, 4 and 20 h. NFLX and CPFX significantly induced DNA damage concentration-dependently after 4 and 20 h treatment, but this damage was recoverable. On the other hand, DNA was not damaged in the cells treated with six other quinolones. In the cells treated with NFLX and CPFX for 20 h, DNA migration was compared by the comet assay at pH 10, 12.1 and >13. The comet assay both at pH 12.1 and >13 showed increased DNA migration, but there was no positive response in the comet assay at pH 10. In the in vitro micronucleus (MN) test, WTK-1 cells were treated with each of four quinolones (NA, PPA, NFLX and CPFX) at 15.63-125 microg/mL for 20 h. NFLX significantly increased MNs in the cells, but no changes were noted in the cells treated with three other quinolones. These results suggest that NFLX and CPFX induced DNA single strand breaks (SSBs), and that NFLX-induced SSBs resulted in chromosome aberrations.

Anti-Infective Agents↗
PubMed1999

Cytogenetic damage after 131-iodine treatment for hyperthyroidism and thyroid cancer. A study using the micronucleus test.

To detect the incidence and persistence of potential chromosome damage induced by iodine-131 therapy, we applied the cytokinesis-block micronucleus assay to peripheral blood lymphocytes from hyperthyroidism and thyroid cancer patients treated with 131I. Two groups of patients were evaluated in a longitudinal study; one group was composed of 47 hyperthyroid patients and the other of 39 thyroid cancer patients. In the hyperthyroidism group, the micronuclei frequency was determined before 131I therapy and 1 week, 1 month and 3 months after it. Furthermore, an additional sample was taken from a subgroup of 17 hyperthyroidism patients 6 months after treatment. In the thyroid cancer group, the analysis was also conducted over time, and four samples were studied: before treatment and 1 week, 6 months and 1 year later. Simultaneously, a cross-sectional study was performed with 70 control subjects and 54 thyroid cancer patients who had received the last therapeutic dose 1-6 years before the present study. In the hyperthyroidism group a significant increase in the micronuclei average was found over time. In the sample obtained 6 months after therapy, the micronuclei mean frequency was practically the same as in the sample taken 3 months before. In the thyroid cancer group a twofold increase in the frequency of micronuclei was seen 1 week after therapy. Although this value decreased across time, the micronuclei frequency obtained 1 year after 131I therapy remained higher than the value found before it. Concerning the data from the cross-sectional study, a significant increase in the frequency of micronuclei was detected in the subgroup of thyroid cancer patients treated between 1 and 3 years before the current study. These results indicate that exposure to 131I therapy induces chromosome damage in peripheral lymphocytes and that the cytokinesis-block micronucleus assay is sensitive enough to detect the genetic damage by exposure to sufficiently high levels of radiation from internal radioactive sources.

Adolescent↗