The cytogenetic damage, radiosensitivity and adaptive response in children living in the different districts of Moscow

The spontaneous level of blood lymphocytes with micronuclei (MN), the sensitivity to 1.0 Gy irradiation and adaptive response (AR) after adaptive irradiation with a dose of 0.05 Gy 5 hr later have been studied in children population living in different districts of Moscow. It was shown that spontaneous frequency of cells with MN, the sensitivity to 1.0 Gy acute irradiation and the AR manifestation have significant differences in samples taken from children living in different districts. The individual variability is significant also. In each group of children the individuals with the enhanced radiosensitivity after adaptive irradiation have been observed. In conformance with the data of radioecological inspection the radiation situation in different Moscow districts is quite safe on overage but in some districts the spontaneous level of lymphocytes with MN, and radiosensitivity after 0.05 Gy irradiation were enhanced, the AR was not found.     

Cytogenetic results of irradiation of Southern Ural residents

The paper summarizes the results of studies of 85 individuals exposed in the Southern Ural region. The spontaneous frequency of the cells with micronuclei (MN) in a population of human blood lymphocytes after PHA stimulation and cytokinetic block with cytochalasin B has been determined. The sensitivity of lymphocytes to the irradiation at the dose of 1.0 Gy and the adaptive response (AR) after the irradiation at the low adaptive dose of 0.05 Gy, and the challenge dose of 1.0 Gy 5 h later have been studied too. It was shown that the peculiarity of the Urals population consists in a higher individual variability of the frequency of cells with MN in all groups have been investigated (spontaneous, after acute irradiation in the dose 1.0 Gy) in comparison with Moscow people. The proportion of persons with a significant AR in the Urals groups was considerably lower than that identified among Moscow residents, and the number of persons with enhanced radiosensitivity increased following low-dose irradiation. We can suppose that prolonged action of low level radiation with another ecological factors, living in the contaminated regions result in the enhancement of the sensitivity to the genotoxic agents in the separate individuals.     

Inherited susceptibility to bleomycin-induced micronuclei: correlating polymorphisms in GSTT1, GSTM1 and DNA repair genes with mutagen sensitivity

Susceptibility to DNA damage varies among individuals and sensitivity to bleomycin (BLM) may reflect the inter-individual differences. BLM sensitivity in part may be explained by inherited differences in DNA repair genes. We investigated the association between genetic polymorphisms in the GSTT1, GSTM1, XPD, XRCC1 and XRCC3 genes and the levels of spontaneous and BLM-induced DNA damage in peripheral blood lymphocytes from 200 healthy, unexposed individuals. The investigation of BLM sensitivity on cancer- or disease-free subjects and not occupationally exposed to known mutagen represents the strengths of the present study, as the detection of genetic damage is not biased by any disease- and occupational-related factor. The micronucleus (MN) assay was used to detect the spontaneous and BLM-induced genetic damage whereas, genotype analysis was carried out using methods based on polymerase chain reaction. Poisson regression analysis showed that subject's age, gender and smoking status had no effect on the spontaneous and BLM-induced MN frequencies. Genotype analysis revealed a clear association between GSTT1-null and XPD polymorphisms and both spontaneous and BLM-induced MN frequencies, whereas the effect of the XRCC1 polymorphism was marginally significant only with regard to spontaneous MN frequency. Genotype analysis did not reveal a clear association between the other studied SNPs (GSTM1 and XRCC3) and MN frequencies. Poisson regression analysis revealed no association between the score of protective alleles and the frequency of spontaneous MN. However, an increased number of protective alleles was significantly associated with a lower frequency of BLM-induced MN (P=0.0003). This finding highlights the genetic basis for BLM sensitivity, which could be a valid and useful surrogate for identifying genotypes that might increase susceptibility in population exposed to carcinogens. Further investigations in a large sample size and including more SNPs, reflecting the complexity of DNA repair machinery, might lead to the identification of a genetic profile responsible for the susceptibility to genotoxicants, with a far-reaching long-term impact on primary prevention and early detection of disease associated genes.     

Micronuclei and ageing in a sample of Yugoslavian population

OBJECTIVE: Instability in the organization and expression of the genetic material has been hypothesized as the basic mechanism of ageing. Aim of this study was to quantify the effect of ageing on spontaneous micronuclei (MN) frequency in peripheral blood lymphocytes. METHOD: Analysis of Yugoslavian population sample (164 tested individuals, age 0-62 years) has performed by application of cytokinesis-block technique (CB). RESULTS: There was an increase of MN frequency with age, from newborns to 40-year-old persons. The total average of MN frequency per 1000 analyzed binuclear cells amounts to 8.03 +/- 0.42, with variation from 0 to 26 MNs. In a sample of 29 newborns the recorded average MN frequency was 6.91 +/- 0.81, while among 69 persons 25-39 years old, the MN frequency was 9.16 +/- 1.00. The lowest average MN frequency, however, was noted in the sample of 34 tested individuals 40 to 62 years of age. CONCLUSION: An increase with age in MN frequency has been observed in samples of studied individuals from newborns to 40-year-old persons. A decrease of MN frequency in older groups could be explained by a gradual decrease of proliferative cell capacities.     

Biomarkers of DNA damage in marine mammals.

Certain environmental contaminants found in marine mammals have been shown to cause DNA damage and cancer. The micronuclei (MN), sister chromatid exchange (SCE) and/or chromosome aberration (CA) assays were used to assess baseline (spontaneous) levels of DNA damage in blood lymphocytes of individuals of the relatively healthy and lightly contaminated Arctic beluga whale (Delphinapterus leucas), Sarasota Bay, FL, bottlenose dolphin (Tursiops truncatus) and Northwestern Atlantic grey (Halichoerus grypus) and harp (Phoca groenlandicus) seal populations. MN cell (MNC) frequencies ranged between 2 and 14/1000 binucleated (BN) cells and were statistically similar between species. In bottlenose dolphins, MNC frequency was correlated with age and was significantly higher in females than in males. No intraspecific variation in MNC frequency was found in beluga whales. Intraspecific variation was not tested in seals due to the small sample size. Frequencies of SCEs and total CAs, excluding gaps, ranged, respectively, between 1 and 15 SCE(s)/per cell and 4-6 CAs/100 cells in beluga whales. SCE and CA frequencies did not vary with age or sex in beluga whales. The MN, SCE and CA assays were found to be practical tools for the detection of DNA damage in marine mammals and could be used in the future to compare DNA damage between relatively lightly and highly contaminated populations.     

Micronuclei and Ageing in a Sample of Yugoslavian Population

Objective: instability in the organization and expression of the genetic material has been hypothesized as the basic mechanism of ageing. Aim of this study was to quantify the effect of ageing on spontaneous micronuclei (MN) frequency in peripheral blood lymphocytes. Method: analysis of Yugoslavian population sample (164 tested individuals, age 0–62 years) has performed by application of cytokinesis-block technique (CB). Results: there was an increase of MN frequency with age, from newborns to 40-year-old persons. The total average of MN frequency per 1000 analyzed binuclear cells amounts to 8.03 ± 0.42, with variation from 0 to 26 MNs. In a sample of 29 newborns the recorded average MN frequency was 6.91 ± 0.81, while among 69 persons 25–39 years old, the MN frequency was 9.16 ± 1.00. The lowest average MN frequency, however, was noted in the sample of 34 tested individuals 40 to 62 years of age. Conclusion: an increase with age in MN frequency has been observed in samples of studied individuals from newborns to 40-year-old persons. A decrease of MN frequency in older groups could be explained by a gradual decrease of proliferative cell capacities.     

Adaptive response of blood lymphocytes of the inhabitants of the South Ural chronically exposed to radiation

The inhabitants of Techa river villages exposed to injured radiation action and inhabitants of uncontaminated regions were examined by micronuclei (MN) assay. The initial damage of blood lymphocytes, the role of radiation in the induction of sensitivity to the acute irradiation and the ability to form the adaptive response were evaluated. It was shown that the initial level of damaged lymphocytes in the inhabitants of the contaminated area did not differ significantly from the spontaneous level. But in these people the sensitivity to acute irradiation was decreased. The ability to develop the adaptive response was decreased too. It was suggested that the radiation plays the main role in the development of radiosensitivity and adaptive response in chronically irradiated people.     

The connection between molecular-cellular parameters and immune status of liquidators after Chernobyl accident

The genome damage (the frequencies of cells with micronuclei (MN), chromosome aberrations, the level of DNA double-strand breaks (DSB DNA), the concentration of reactive oxygen species (ROS) and 28 immunological parameters have been studied on the blood lymphocytes of Chernobyl accident liquidators. The purpose of this article was the investigation of cytogenetic, molecular changes of blood lymphocytes of irradiated individuals 24 years after accident, examination it there are correlation between genome damage and immunological parameters. It was shown that in lymphocytes of liquidators the frequencies of cells with MN and with all type of chromosome aberrations didn't differ from the lymphocytes of nonirradiated individuals, but the frequency of chromosome aberration type was increased, the level of DSB DNA was increased too. The concentration of ROS is decreased. The percent of cytotoxic CD8(+)-T-lymphocytes, natural killer cells (CD16(+)-lymphocytes), CD3+ CD16+ CD56+ (NK-T-cells), that posses antivirus and antitumor activity--HLA-DR+, regulatory T-lymphocytes (CD4+ CD25+high) in liquidators significantly increases. The level of serum immunoglobulin (Ig A) significantly increases too. The index of immune regulation, meaning of phagocyte neutrophil (FAN) and macrophage activity decreases. In liquidators there are significant correlation between the frequencies of cells with MN and the content of regulatory T-lymphocytes (p < 0.05), between the concentrations of ROS and activated T-lymphocytes. More connection is on the tendency level (p < 0.10): the frequency of chromosome aberrations, the DSB DNA level with natural killer cells and regulatory T-lymphocytes; the frequency of cells with MN and DSB DNA and FAM. We can suppose that genomic instability induced by the liquidators of Chernobyl accident consequences 24 years ago manifests now as increased genome damage and oxidative status decrease that can result in imbalance of cells and humoral immune status, disturbancies of health.     

On the new mechanism of adaptive response

The role of changes in cell composition of population of human blood lymphocytes in the forming of an adaptive response (AR) has been studied. By micronuclei assay and cytokinetic block with cytohalasin B the frequency of mono-, bi- and multinuclear cells with micronuclei (MN) and without MN were determined in the initial population. The same parameters have been studied after exposure of the population to the adaptive (0.05 Gy), challenge (1.0 Gy) doses and to doses 0.05 + 1.0 Gy 5 hours after. 13 from 23 investigated individuals manifested the AR: the decreasing of the ratio of damaged binuclear cells to the all binuclear cells after the adaptive and challenge exposure. It was shown that the ways of an AR forming are different: in 7 of 13 individuals with AR the number of binuclear cells with MN did not decrease but the amount of binuclear undamaged cells increased. The ratio of these parameters enhances but not for the account of cells with MN decreasing. There is the linear correlation between the frequency of cells with MN and the frequency of binuclear cells in population (spontaneous, after irradiation with doses of 0.05, 1.0 and 0.05 + 1.0 Gy) with the coefficient of correlation about -1. These results show the presence of new mechanism of AR forming, which is not connect with the induction of damage repair and rather with the stimulation of cell division. In the another group of individuals the decrease in damaged cells number after irradiation with doses of 0.05 + 1.0 Gy have been observed. Probably the stimulation of repair system occurred to the moment of 1.0 Gy irradiation. Thus, the mechanism of an AR forming depends on the individual properties of organism. The work was suppoted by RFBR grant 03-04-48325a.     

Micronuclei in peripheral blood lymphocytes and buccal epithelial cells of Polish farmers exposed to pesticides.

In this biomonitoring study, we investigated whether an occupational exposure to a complex mixture of chemical pesticides produced a significant increase of micronuclei (MN) in both peripheral blood lymphocytes and buccal cells. Forty-nine male workers exposed to pesticides, from an agricultural area of Malopolska Region in Southern Poland, together with 50 men from the same area without indication of exposure to pesticides that served as controls, were used in this investigation.No statistically significant differences in the frequencies of cytogenetic damage were detected between exposed and control individuals, for either type of cells. The multiple linear regression analysis in the case of lymphocytes indicated that the studied cytogenetic endpoints were inversely influenced by alcohol; whilst a negative binomial regression, in the case of buccal cells, indicated that the MN values were directly influenced by the ingestion of red meat. An inverse negative relationship between the cytokinesis-block proliferation index and age, and a significant increase of miscarriages due to the exposure to pesticides were also observed.     

Molecular-cellular characteristic of blood lymphocytes in Hodgkin lymphoma

The molecular-cellular parameters complex has been studied on the blood lymphocytes of malignant Hodgkin's lymphoma (HL) patients: the frequency of cells with micronuclei (MN) and chromosome aberrations; the level of DNA single and double strand breaks - OR and DR DNA (DNA comet assay), oxidative status--the content of reactive oxygen species (ROS) by using nonfluorescent dye that is oxygenated in the cells to fluorescent reagent and detection of fluorescence intensity after there. It was shown that the patients with LH had the increased level of DR and OR DNA, the increased frequency of cells with chromosome aberrations and the number of aberrations per cell was increased too. The concentration of ROS is increased too for the most individuals with intoxication. In the process of the chemical and radiation therapy the increase of OR DNA level, the frequency of the cell with MN has been registered. The ROS concentration correlates with the level of DNA-strand breaks. So the blood lymphocytes of HL patients before treatment differ from the lymphocytes of healthy donors. The damage of genome and the change of oxidative status have been observed that can be additive markers for the HL diagnosis, their sensitivity to the treatment and the characteristic of lymphocytes changes by this disease.     

Micronuclei frequency induced by bleomycin in human peripheral lymphocytes: correlating BLHX polymorphism with mutagen sensitivity

Mutagen sensitivity assay, by measuring chromosome damage induced by an in vitro treatment of peripheral lymphocytes with bleomycin, has been proposed as a biomarker for assessing cancer susceptibility. Recently, a single nucleotide polymorphism (SNP A1450G) of the gene for bleomycin hydrolase (BLHX), a specific neutral cysteine protease able to metabolise bleomycin, was proposed as a plausible candidate to variation in mutagen sensitivity. To shed more light on the effect of BLHX genotype on the expression of chromosome damage induced in vitro by bleomycin, we determined mutagen sensitivity for 45 non-smoker healthy volunteers. The level of bleomycin-induced chromosome damage was assessed as frequencies of micronuclei (MN) in cytokinesis-blocked lymphocytes. The subjects were genotyped for the BLHX gene, to determine the possible effect of this polymorphism on mutagen sensitivity. No difference in the spontaneous value of MN was detected between the homozygotes wild-type (A/A) and the carriers of variant alleles A/G heterozygotes or G/G homozygotes (MN/1000 binucleated (BN) cells: 6.69+/-2.53 and 6.37+/-4.87, respectively). A substantial effect of BLHX polymorphism in predetermining individual mutagen sensitivity status was observed: subjects with the BLHX A/A genotype displayed significantly lower mean levels of bleomycin-induced MN frequency than the carriers of A/G or G/G variant alleles combined (12.00+/-3.76 MN/1000 BN vs. 16.37+/-8.86 MN/1000 BN, respectively; P=0.029). The multiple regression analysis, including BLHX genotype and age, confirmed the significant effect of BLHX variant alleles (A/G, G/G) on the chromosome damage induced by bleomycin (P=0.01), whereas age correlated only with the spontaneous MN frequency.     

The adaptive response of first generation offsprings irradiated parents

In offspring's of first generation irradiated inhabitants of Techa river (fathers, mothers and both parents) the spontaneous level of damaged blood lymphocytes, sensitivity of lymphocytes to the additional acute irradiation in dose 1.0 Gy and radioinduced adaptive response after adaptive (5 cGy) and challenge (1.0 Gy) irradiation 5 h after was studied. The micronuclei test with cytochalasin B as a criteria of the effect have been used. It was shown, that descendents of irradiated parents differ from the control group. The main difference is the significant decrease of the adaptive response frequency in the progeny. In the offspring's of the irradiated fathers and mothers there is no one individuals with the adaptive response; in the offspring's of both irradiated parents the frequency of individuals with adaptive response decreases in control from 19.5% to 6.8%. The distribution of descendents according to response on adaptive irradiation differ significantly from the control distribution and from the each other. And the tendency to the radiosensitivity increase after adaptive irradiation was observed. In the whole joint group of progeny the mean spontaneous cell frequency with micronuclei decreased, but the sensitivity of lymphocytes to the additional acute irradiation doesn't differ from the control. The results of the paper permit to suppose that transgenerational genome instability in human can be determined. Earlier discovered decrease of the adaptive response frequency in the Techa river livings is observed in the offspring's of irradiated fathers, mothers and both parents.     

Investigating the effects of dietary folic acid on sperm count, DNA damage and mutation in Balb/c mice

The cytokinesis-block micronucleus cytome (CBMN-Cyt) assay was originally developed as an ideal system for measuring DNA damage, cytostasis and cytotoxicity. The objective of the present study is to simultaneously evaluate the background levels of micronuclei (MN), nucleoplasmic bridges (NPBs), nuclear buds (NBUDs), cell death (necrosis or apoptosis) and nuclear division index (NDI) in the peripheral blood lymphocytes of non-occupationally exposed, healthy subjects living in the city of Kayseri in Turkey. We used the CBMN-Cyt assay, taking into account factors - age, gender, and smoking habits - that might affect MN frequency and also other CBMN-Cyt assay parameters. Ninety-six healthy subjects (48 female and 48 male) were selected with ages varying between 21 and 60 years. The parameters, except for the number of binucleated (BN) cells with NPBs, showed no statistically significant difference between smokers and non-smokers. There were significant differences between female and male groups in MN frequency (higher in females) and in the number of NPBs (lower in females), while the other parameters were not significantly different between genders. The correlations between years of age and MN frequency, number of NPBs and the frequency of necrotic cells were statistically significant, while the correlations between the years of age and the other parameters were not. The results of the correlation analysis between years of smoking and MN frequency were positive, although no statistically significant correlation was found between the years of smoking and the other parameters. Among the smokers, no correlation was found either between the pack-years of smoking and the parameters assessed in this group. The results of the present study provide evidence of increasing MN frequency, number of NPBs and frequency of necrotic cells with increasing age in the peripheral blood lymphocytes of healthy individuals and influencing MN frequency and number of NPBs by gender.     

Formation of micronuclei and of clastogenic factor(s) in patients receiving therapeutic doses of iodine-131

The micronucleus (MN) assay in peripheral blood lymphocytes was applied to assess the genotoxic potential of a single dose of iodine-131 (131I) given to six patients for ablation of thyroid remnants after total thyroidectomy. Lymphocytes were taken at various times after 131I therapy (from 2 to 180 days), and evaluated for the presence of MN in the binucleated cells identified after blocking cytokynesis with cytochalasin B. The presence of ultrafiltered, low-molecular weight, clastogenic factor(s) (CFs) in the plasma of 11 patient undergoing 131I therapy was also sequentially assessed.A significantly increased MN frequency was observed in lymphocytes of patients as soon as the first sampling time (2 days after 131I therapy), multifactor analysis of variance (MANOVA): P<0.0001, peaking at day 7 at almost four-fold the spontaneous frequency observed in the pre-therapy samples. MN frequency slowly declined thereafter, reaching the baseline levels at the 180-day time point. When tested against peripheral blood lymphocytes from a healthy donor, the ultrafiltered CFs obtained from 11 patient's plasma induced a significant increase of the MN frequency peaking at day 15. Thereafter, a slow MN frequency decline was observed and the baseline frequency was reached after 180 days. A significant relationship was found between the MN frequency observed in lymphocytes of patients after 131I therapy and the genotoxic CFs activity present in their plasma (P=0.019).These findings suggest that 131I induces a significant increase in the MN frequency of peripheral blood lymphocytes, as well as the formation of transferable CFs which persist for at least 60 days after administration of the radionuclide. The presence of these CFs might be responsible of chromosome aberrations often observed in cultured lymphocytes following X-ray exposure. The possibility of reducing the genotoxic activity of radionuclide therapy by chemoprevention of CFs with antioxidant drugs remains to be explored.     

Spontaneous and induced aneuploidy in peripheral blood lymphocytes of patients with Alzheimer’s disease

This study was aimed at assessing whether peripheral blood lymphocytes of patients with Alzheimer’s disease (AD) show significant levels of aneuploidy and high percentages of cytogenetic events in vitro, indicating a predisposition to aneuploidy spontaneously, or after chemical treatment in vitro. A group of affected individuals and a group of unaffected, age-, sex- and smoking-habit-matched controls were identified. Lymphocytes were cultured for analysis of the following cytogenetic parameters: premature centromere division (PCD), satellite associations of acrocentric chromosomes (SA) and micronuclei (MN). In a subset of subjects, the fluorescence in situ hybridization (FISH) technique was combined with the MN assay, by means of a pancentromeric DNA probe for the detection of the presence of centric material. To evaluate the sensitivity to aneuploidogenic agents, in vitro treatment of lymphocytes of affected individuals was performed by adding griseofulvin, a chemical whose supposed target is microtubule-associated protein(s). Both the spontaneous frequency of MN and the frequency of PCD was significantly higher in patient cells than in controls. Furthermore, after application of the FISH technique, we found that the majority of MN were composed of whole chromosomes (because of the phenomenon of chromosome loss). Metaphase analysis for the detection of associative events between satellite regions of acrocentric chromosomes showed no differences between the two groups under study. Analysis of sensitivity to the aneuploidogen griseofulvin showed that the patient group was characterized by lower levels of MN induction compared with controls. Our data confirm that peripheral blood lymphocytes of AD patients are prone to undergo aneuploidy spontaneously in vitro and support the hypothesis that microtubule impairment might be associated with the disease. Received: 13 January 1997 / Accepted: 30 July 1997     

Enhanced frequency of micronuclei in individuals exposed to arsenic through drinking water in West Bengal, India

In West Bengal, India arsenic in ground water has been found to be above the maximum permissible limit in seven districts covering an area of 37,493km2. In the present study, evaluation of the micronuclei (MN) formation in oral mucosa cells, urothelial cells and peripheral blood lymphocytes was carried out in the symptomatic individuals exposed to arsenic through drinking water. Forty five individuals with cutaneous signs of arsenicism from four affected districts (368.11 microg/l of As in drinking water) were considered as the exposed group and 21 healthy individuals with no symptoms of arsenic poisoning and residing in two unaffected districts (5.49 microg/l of As) were considered as controls. The exposed and control groups had similar age distribution and socioeconomic status. Standardised questionnaires were utilised and medical examination was conducted to ascertain exposure history, sociodemographic characteristics, diet, health, medication, addiction and chief symptoms in the study participants. Arsenic exposure was confirmed by measuring the arsenic content in the drinking water, nails, hair and urine samples from the volunteers. Arsenic contents in the urine, nail and hair in the exposed group were 24.45 microg/l, 12.58 and 6.97 microg/g, respectively which were significantly high in comparison to corresponding control group values of 4.88 microg/l, 0.51 and 0.34 microg/g, respectively. Exposed individuals showed a statistically significant increase in the frequency of MN in oral mucosa, urothelial cells and lymphocytes (5.15, 5.74 and 6.39/1000 cells, respectively) when compared with the controls (0.77, 0.56 and 0.53/1000 cells, respectively). Thus, the above results indicate that the symptomatic individuals exposed to arsenic through drinking water in this region have significant cytogenetic damage.     

Validation of micronuclei frequency in peripheral blood lymphocytes as early cancer risk biomarker in a nested case-control study

Aim of this work was to assess the predictive value of micronuclei (MN) frequency in peripheral blood lymphocytes (PBL) for the risk of cancer death in disease-free individuals. Blood samples from 1650 subjects selected from the general population of Pisa, Italy, were collected between June 1991 and November 1993. The follow-up until January 2005 recorded a total of 111 deaths (52 for cancer). MN frequency was assessed for 49 cancer cases and 101 matched controls. A significantly higher MN frequency was found in cancer cases (4.7+/-3.4 MN/1000 BN cells) versus controls (1.5+/-1.7; p<0.0001). Donors were stratified in two classes and multivariate logistic regression analysis confirmed that individuals with high MN frequency (>2.5 MN/1000 BN cells) had a significantly increased risk of cancer death (OR=10.7; 95% CI=4.6-24.9; p<0.0001) when compared to individuals with low MN frequency (相似文献   

A combination of the micronucleus assay and a FISH technique for evaluation of the genotoxicity of 1,2,4-benzenetriol

The cytokinesis-block micronucleus (CBMN) assay has emerged as one of the preferred methods for assessing chromosome damage. Micronuclei (MN) are small, extranuclear bodies that are formed in mitosis from acentric chromosomal fragments or chromosomes that are not included in each daughter nucleus. Thus, MN contain either chromosomal fragments or whole chromosomes. The CBMN assay, together with a fluorescence in situ hybridization (FISH) technique using specific centromeric probes for chromosomes 7 and 8, were employed in mitogen-stimulated human lymphocytes pretreated with the benzene metabolite, 1,2,4-benzenetriol (BT). Treatment of human lymphocytes resulted in the induction of MN in a dose-dependent manner. The frequency of MN in control lymphocytes was 4.5 per 1000 binucleated (BN) cells and this increased to 9.5, 14, 28 and 40 per 1000 BN cells at 10, 25, 50 and 100 microM BT, respectively. The frequency of aneuploidy 7 and 8 in BN cells also increased at each concentration. Aneuploidy 8 was more frequent than aneuploidy 7, suggesting that chromosome 8 is more sensitive to aneuploidy induction by BT. The frequency of MN containing centromere positive signals for chromosomes 7 and 8 increased with the concentration of BT. The frequency of MN with centromere positive signals was higher for chromosome 8 than for chromosome 7, also suggesting a greater sensitivity of chromosome 8 to this agent. These results suggest that combined application of the CBMN assay with a FISH technique, using chromosome-specific centromeric probes, would allow the detection of aneuploidy in human lymphocytes and identify the mechanistic origin of MN induced by a clastogen or aneugen.     

Micronucleus frequency in human umbilical cord lymphocytes

The human fetus is exposed to a variety of environmental agents and drugs which cross the placenta and can induce DNA damage. Micronucleus (MN) determination is a suitable and sensitive method for measuring DNA damage and since umbilical cord blood is obtained without any risk for the newborn, we measured the frequency of MN in cells from cord blood in four groups of healthy newborns (NB): 35 NB whose mothers lived in two urban cities (groups I and II); 16 NB from an agricultural area (group III); and 15 NB of mothers with high-risk pregnancy (group IV). MN were also evaluated in the mothers of NB from group I (n=17) and group III (n=14). Acetylcholinesterase (AChE) concentration was measured in groups I and III. The average frequency of binucleated cells with MN was 3.7+/-1.4 in 1000 cells in mothers and 1+/-0.9 in 1000 cells in NB from urban areas; and 4.5+/-2.4 in 1000 cells in mothers and 2+/-1.5 in 1000 cells in NB from the agricultural area. The correlation between the frequency of MN in mothers and NB was significant (r=0.61, p<0.01). AChE levels of samples obtained both from group III mothers and from newborns were similar to those of group I. The Wilcoxon's rank-sum test was applied to measure differences in MN frequency; NB of group I were used as control group. A significant (p<0.01) higher frequency of MN (4+/-2) was found only in lymphocytes from NB from high-risk pregnancies. Data indicate that MN evaluation in umbilical cord samples might be useful in the identification of transplacental mutagens.