Comparison of spontaneous structural chromosome aberration frequency in 48 h-cultured human lymphocytes mitotically arrested by different colcemid treatments

Alterations in mitotic index and cell cycle kinetics are reported to be dependent on both the culture conditions and the ability of the lymphocytes of each individual to respond to phytohaemagglutinin stimulus. Thus, the frequency of structural chromosome aberrations (CA) could prove to be affected to some degree by these parameters. CA frequency and cell proliferation index (PI) were assessed in a group of healthy subjects after adding colcemid to cultured lymphocytes 3 h (standard) and 22 h (modified) before cell fixation at 48 h. All control cultures treated with colcemid for 22 h consisted exclusively of first metaphases, whereas the proportion of second-division lymphocytes in standard cultures (3 h colcemid) ranged from 4% to 49%. In addition, CA frequencies with and without gaps were always elevated in modified cultures as compared to the standard ones, and the difference between CA percentages obtained with the two methods was found to be significantly related with increasing PI values.

Synthesis and biological activity of a series of isoindolone derivatives related to cytochalasins

A series of hydrogenated isoindolone derivatives structurally related to cytochalasin B has been synthesized and their ability to induce binucleation in the human lymphocytes were tested. All compounds were found able to inhibit cell cytokinesis at different extent in the range (3.12-25 mumol/l) respect to the negative control; however the highest percentage of binucleated cells is induced by Cyt B.

Detection of the centromere in micronuclei by fluorescence in situ hybridization: its application to the human lymphocyte micronucleus assay after treatment with four suspected aneugens

The human lymphocyte micronucleus (MN) test combined with fluorescence in situ hybridization (FISH) of a centromeric probe is considered a useful screening assay to distinguish between clastogenic and aneugenic agents. Four suspected aneuploidy-inducing chemicals, acetaldehyde (AA), diethylstilbestrol (DES), diethylstilbestrol dipropionate (DESdp) and griseofulvin (GF), have been evaluated with the assay. All compounds induced a significant increase of MN at all doses tested. After the application of the FISH technique with a pancentromeric DNA sequence, DES, DESdp and GF showed a statistically significant increase in the percentage of positive signals compared with the control culture. GF induced the highest percentage of centromere-positive MN observed to date (>90% on average). AA did not show a significant difference in the percentage of centromere-positive MN. The results indicate that in human lymphocytes DES, DESdp and GF act primarily as aneugens, while AA seems capable of causing both chromosome breakage and aneuploidy.

Cytogenetic monitoring of a group of Italian floriculturists: no evidence of DNA damage related to pesticide exposure

The induction of sister chromatid exchanges (SCE), structural chromosome aberrations (CA) or micronuclei (MN) was investigated in peripheral lymphocytes of a group of Italian floriculturists exposed to a mixture of pesticides. No statistically significant difference in the frequencies of cytogenetic damage was detected between exposed and control subjects. Assessment of the effect of confounding factors indicated that smoking affected both SCE and CA frequencies. Multiple regression analysis showed that in heavy smokers (> or = 20 cigarettes/day), SCE and CA levels increased significantly by 17% and 54%, respectively, as compared to non-smokers.

Cytogenetic monitoring of occupational exposure to pesticides: characterization of GSTM1, GSTT1, and NAT2 genotypes

Occupational exposure of floriculturists is characterized by alternating periods of intense pesticide spraying and reduced or no activity. Induction of sister chromatid exchanges (SCE), structural chromosome aberrations (CA) and micronuclei (MN) was investigated in peripheral lymphocytes of a group of 23 Italian floriculturists and 22 matched controls. Blood sampling was performed during and one month after the end of intensive pesticide treatments, in order to cover a period of high and low exposure, respectively. Each donor was genotyped for glutathione S-transferase M1 (GSTM1), T1 (GSTT1), and N-acetyltransferase 2 (NAT2), three polymorphic genes involved in xenobiotic metabolism, to assess their potential role in individual genotoxic response to the pesticide exposure. No effect of the pesticide exposure on the cytogenetic parameters were detected. Smoking, however, was found to increase SCE levels. The only significant influence of phenotype composition on cytogenetic response was an increase in SCE levels in the GSTT1 positive individuals compared with the GSTT1 nulls (P=0.02). This finding was, however, based on only four GSTT1 null donors (n=41 for GSTT1 positive donors). In addition, a possible interaction was observed between smoking and GSTM1 genotype in the CA assay, GSTM1 null smokers, earlier reported to have an elevated risk for lung cancer, showing higher CA frequencies than GSTM1 positive smokers.

Vanadium salts induce cytogenetic effects in in vivo treated mice

Three vanadium salts, vanadyl sulfate (SVO5), sodium orthovanadate (Na3VO4) and ammonium metavanadate (NH4VO3), were tested for induction of genotoxic effects in bone marrow of mice following intragastric treatment. Micronucleus (MN) induction in polychromatic erythrocytes (PCEs), structural (sCA) and numerical (nCA) chromosome aberrations in bone marrow cells were evaluated. The micronucleus test, performed at different harvesting times (0-72 h), was found to be positive for all compounds tested. In contrast, except for vanadyl sulfate, no difference was found between controls and treated animals in the sCA test performed 24 and 36 h after treatment. At the same sampling intervals, second metaphases (M II) were positively scored for nCA induction for all three vanadium salts. In addition, the frequency of hypoploid and hyperploid cells was shown to be statistically different from the control value. Polyploid cells were also induced by all compounds, but their frequency was not statistically significant. The positive results obtained by nCA analysis support the finding of a significant presence of types of micronuclei that are probably aneuploidy-related. This finding was further supported by the successful classification of such micronuclei on the basis of shape and size according to Tinwell and Ashby (1991) during microscope analysis.

The use of fluorescence in situ hybridization with a beta-satellite DNA probe for the detection of acrocentric chromosomes in vanadium-induced micronuclei

Vanadium salts have been shown to be aneuploidogenic in human lymphocyte cultures. In particular, increases in the frequency of chromosome satellite associations and a high proportion of induced micronuclei with centromeric signals seem to be connected with chromosome malsegregation mechanisms in which acrocentric chromosomes may be involved. Our aim was to assess the contribution of these chromosomes to the formation of vanadium-induced micronuclei by applying the fluorescence in situ hybridization technique to the human lymphocyte micronucleus assay. Whole blood cultures were treated after 24 h with 0, 10, 40, and 80 microM sodium orthovanadate or vanadyl sulfate and harvested at 72 h; vinblastine, 20 ng/ml, was used as a reference compound. The slides were then hybridized with biotin-labeled beta-satellite DNA probes specific for all human acrocentric chromosomes. After chemical treatment, the percentage of micronuclei with fluorescent signals was found to be statistically higher than that in control cultures, whereas vinblastine induced only a slight increase in micronuclei.

Induction of binucleation in human lymphocytes by 14 synthetic isoindolone derivatives related to cytochalasins

Fourteen hydrogenated isoindolone derivatives with affinity to cytochalasin B were synthesized and tested for the induction of binucleation in the human lymphocyte micronucleus (MN) assay. The experimental procedure was the one commonly used for the human lymphocyte MN assay. Compounds like cyt-B were added to cultures at 44 h and tested at increasing concentrations, up to 200 mumol/l, in the range commonly used for cyt-B in the MN assay (3 micrograms/ml = 6.25 mumol/l). Induction of cytokinesis-blocked binucleated cells was found for all compounds but, at the same molarity, cyt-B induced a higher percentage of binucleation. Only one of the compounds tested was found to induce micronuclei significantly: MN were induced across the dose range of 25-100 mumol/l.

Cytogenetic monitoring of fishermen with environmental mercury exposure

Due to high mercury levels in many Mediterranean aquatic organisms, people who live in this area and consume large amounts of seafood are exposed to a toxicological hazard. A group of 51 fishermen exposed to mercury through eating contaminated seafood from the northern Tyrrhenian Sea underwent cytogenetic monitoring. This work is part of a research project consisting of the evaluation of micronuclei (MN), chromosomal aberrations (CA) and sister-chromatid exchanges (SCE) in peripheral blood lymphocytes. Here we present data on mercury levels in blood and on micronucleus frequencies in peripheral blood lymphocytes of fishermen. The range of mercury concentrations in blood was 10.08-304.11 ng/g fresh weight, the average was 88.97 +/- 54.09 ng/g. Micronucleus frequency was defined with at least 2000 binucleated cells scored for each person; the average was 8.74 +/- 2.56 expressed on 1000 binucleated cells. A statistical correlation was found between MN frequency and total mercury concentration in blood (p = 0.00041, r = 0.674), as well as between MN frequency and age (p = 0.017). No other parameters taken into account correlated with MN frequency.

Cytogenetic damage induced in human lymphocytes by four vanadium compounds and micronucleus analysis by fluorescence in situ hybridization with a centromeric probe

The genotoxicity of four vanadium compounds, sodium metavanadate (NaVO3), ammonium metavanadate (NH4VO3), sodium ortovanadate (Na3VO4) and vanadyl sulfate (SVO5), was evaluated in human lymphocyte cultures using structural and numerical chromosome aberrations, micronuclei, sister-chromatid exchanges and satellite chromosome associations as endpoints. These compounds were not found to increase the frequency of structural chromosome aberrations whereas a significant increase in numerical aberrations, micronuclei and satellite associations was found. Since these results could have been related to a possible mechanism of the action of vanadium as a mitotic spindle poison, the fluorescence in situ hybridization (FISH) technique was applied to the human lymphocyte micronucleus assay, by means of an alphoid centromere-specific DNA probe. The four vanadium salts showed a micronucleus percentage with positive signal (presence of centromere and thus of whole chromosome(s)) that was always higher than 68% at all doses tested. That confirmed the aneuploidogenic potentiality of vanadium.

Effect of bacitracin on erythroid differentiation of MEL cells

Bacitracin, an antibiotic widely utilized in clinical and veterinary use, was tested on murine erythroleukemia (MEL) cells. Tests were performed to evaluate the capacity of the drug to interfere with erythroid differentiation. Cells were exposed to a single treatment in S phase at sublethal doses of bacitracin. Two responses were found depending on the drug concentration. At higher concentrations (25 micrograms/ml and 250 ng/ml) a reduction in number of differentiating cells was observed but the kinetics of the process remained unchanged. At lower concentrations (from 2.5 ng/ml to 2.5 fg/ml) a dramatic alteration of the dynamic of differentiation was found. These two responses are related to different activities of the DNA repair mechanisms. Higher doses of bacitracin stimulate repair while lower concentrations are not able to active repair, as demonstrated by tests with hydroxyurea. The bacitracin-induced damage can be considered a stable genetic and/or epigenetic alteration, as demonstrated by the high frequency of mutant clones isolated from low-dose treated cells. The suitability of MEL cells system in evaluating genotoxicity of drugs for veterinary use is underlined.

Monitoring human exposure to urban air pollutants

A multidisciplinary study on a general population exposed to vehicle exhaust was undertaken in Pisa in 1991. Environmental factors such as air pollution and those associated with lifestyle were studied. Meanwhile, biological and medical indicators of health condition were investigated. Chromosomal aberrations, sister chromatid exchanges (SCEs), and micronuclei in lymphocytes were included for the assessment of the genotoxic risk. Because of the large number (3800) of subjects being investigated, standardization of protocols was compulsory. The results on data reproducibility are reported. To assess the reliability of the protocol on a large scale, the population of Porto Tolle, a village located in northeast Italy, was studied and compared to a subset of the Pisa population. Preliminary results showed that probable differences between the two populations and individuals were present in terms of SCE frequencies. The study was potentially able to detect the effects of several factors such as age, smoking, genetics, and environment. The in vitro treatment of lymphocytes with diepoxybutane confirmed the presence of more responsive individuals and permitted us to investigate the genetic predisposition to genetic damage. The possible influence of environmental factors was studied by correlation analyses with external exposure to air pollutants as well as with several lifestyle factors.

Micronuclei in lymphocytes of young patients under antileukemic therapy

The micronucleus test in peripheral blood lymphocytes was employed in the cytogenetic monitoring of children with acute lymphocytic leukemia (ALL), who had undergone chemotherapy and radiotherapy. Patients were treated with a variety of drugs, which included vincristine, methotrexate, daunomycin and prednisone; they also underwent cranial irradiation at the end of the first intensive phase of therapy. The first group under study consisted of 15 subjects on therapy, who showed a marked increase in micronucleated lymphocytes (mean: 19.96 +/- 12.96%) as a consequence of treatment compared with the control group (mean: 3.67 +/- 1.55%), while lower average values were obtained from 15 other subjects at the end of treatment (mean: 13.16 +/- 8.44%). A group of 6 patients was monitored during the entire period of therapy, namely at diagnosis, after 3 months of therapy, throughout maintenance therapy and at the end of it. The whole treatment lasted about 2 years. The results revealed a marked increase in basal micronucleus frequency, due to therapy: the micronucleated lymphocyte frequency remained significantly high throughout the treatment for almost all patients. These data clearly suggest the validity of the methodology in pointing out the role played by antileukemic agents in inducing somatic genetic damage.

Micronucleated lymphocytes in people occupationally exposed to potential environmental contaminants: the age effect

This work is part of a research project on 2 groups of tannery workers (i.e., workers employed in the tanning process and those employed in the finishing department), and 2 control groups consisting of individuals paired with each exposed person according to sex, age and smoking habit. The whole study included the evaluation of micronuclei as well as of chromosomal aberrations and sister-chromatid exchanges in peripheral blood lymphocytes. Data on micronucleus analysis in both controls and exposed persons are shown in this paper. There was no statistically significant difference between MN frequencies in the 2 groups of exposed and controls, nor any positive correlation with smoking habit. The effect of age on basal frequency of micronucleated cells clearly emerges in the present study: both controls and exposed show an increase in MN frequency due to age. This could be correlated with a higher sensitivity to breaks, rearrangements or aneuploidogenic events of circulating lymphocytes in aged people.

The micronucleus assay in Anodonta cygnea for the detection of drinking water mutagenicity

A micronucleus test in gill cells of the freshwater mussel Anodonta cygnea has been proposed for the detection of drinking water genotoxicity. Animals were exposed for 28 days to a drinking water sample and collected every week. Highly significant increases in spontaneous MN frequency were observed at each sampling, especially after 13 days of exposure. As positive control 2 doses of mytomicin C (MMC) were used (10(-8) and 10(-7) M). A second experiment was performed at a municipal waterworks in order to assess the role of water treatment processes in the production of mutagenic compounds. The most prevalent genotoxic effects were detected after chlorination (mean: 10.47% +/- 3.05, p less than 0.001).

Genotoxicity of methylglyoxal: cytogenetic damage in human lymphocytes in vitro and in intestinal cells of mice

The mutagenic activity of methylglyoxal (MG) was assayed in vitro in human lymphocytes [induction of chromosomal aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei] both in the presence and in the absence of metabolic activation (S9 mix). The Ames/microsome test was performed with the Salmonella typhimurium strains considered more responsive (TA102 and TA104). Positive results were obtained for all the genetic endpoints analysed. In human lymphocytes the activity of MG is decreased by the presence of S9 mix. In the in vivo studies, the metaphase analysis in the ileum and duodenum cells of mice treated per os with MG (400 and 600 mg/kg body wt) gave negative results for CA induction, while only a weak increase of SCE in duodenum cells at the higher dose was obtained. Dimethylhydrazine (25 mg/kg body wt), as positive control, was clearly active in inducing both CAs and SCEs in the same intestinal tissues.

The human lymphocyte micronucleus assay: a comparison between whole-blood and separated-lymphocyte cultures

The induction of micronuclei (MN) by vincristine, mitomycin C and cyclophosphamide was compared in purified lymphocytes and in whole-blood cultures. With both assays, cytokinesis was blocked by cytochalasin B and MN were only scored in binucleate cells. The data suggest that whole-blood cultures may be considered a better experimental condition for the detection of MN induced by chemicals in vitro.

Micronuclei and nuclear anomalies induced in the gastro-intestinal epithelium of rats treated with formaldehyde

The induction of micronuclei and nuclear anomalies in cells of the gastro-intestinal epithelium of rats treated per os with formaldehyde (200 mg/kg) was assessed in comparison with N-methyl-N'-nitro-N-nitrosoguanidine as a positive standard. Formaldehyde and N-methyl-N'-nitro-N-nitrosoguanidine both increased micronuclei and nuclear anomalies in almost all tissues analysed (stomach, duodenum, ileum and colon) though with different patterns and to different extents, reflecting different potency and specificity of target. In the case of formaldehyde these effects were observed in conjunction with signs of severe local irritation. This assay can be employed to detect the genotoxic potential of chemicals in vivo directly on target cells in the proximity of the administration site, thus reducing the likelihood of false-negative results.

Experimental model for evaluating the effects of genetic and exogenous factors on transplacental mutagenesis

Cyclophosphamide (CP)-induced micronuclei were evaluated in females of two strains of mice (C57BL and CD1), in F1 hybrid females and in fetuses (day 13 of gestation) obtained from different crosses. F1 adult hybrids from a cross between the strain with a high level of induced micronuclei (C57BL) and the strain with a low response (CD1) exhibited micronuclei values closer to the latter. CD1/CD1 fetuses showed a higher susceptibility than C57BL/C57BL ones. Heterozygous fetuses from reciprocal crosses, whatever the maternal genotype, showed the same sensitivity, which is very close to that of C57BL/C57BL fetuses. Phenobarbital (PB) pre-treatment modified the mutagenic response to CP depending on the genotype of the treated animal. These results demonstrate that the response to a pro-mutagen requiring metabolic activation depends to a large extent on the genetic background of the target animals, and that mother-fetus interactions in transplacental mutagenesis seem to depend more on the fetal than on the maternal genotype.