Biological monitoring of workers in the rubber industry. I. Chromosomal aberrations and sister-chromatid exchanges in lymphocytes of vulcanizers

To evaluate the possible genetic consequences of the industrial exposure among the vulcanizers of a rubber plant we measured the in vivo levels of chromosomal aberrations and sister-chromatid exchanges in peripheral lymphocytes of 34 vulcanizers and in an adequate control population. The observed chromosomal aberration frequencies were 1.9 +/- 1.4 aberrations/100 cells in the exposed group and 2.1 +/- 1.5 aberrations/100 cells in the controls. No difference was found between the two groups for the mean value of sister-chromatid exchanges (5.2 +/- 1.3 in the exposed, 5.2 +/- 0.7 in the control group). Cigarette-smoking was clearly associated with increased sister-chromatid exchange frequencies both in the exposed and in the control groups, while chromosomal aberration frequencies were not correlated with smoking habits.     

Chromosomal aberrations and sister-chromatid exchanges in lymphocytes from coke oven workers

To test whether coke oven workers, an occupational group known to be at increased cancer risk, manifest increased peripheral blood chromosomal aberration frequencies, we obtained samples from a group of 30 steelworker volunteers, who had worked several years at coke oven jobs. Exposure estimates were made using measurements of work place atmospheric coal tar pitch volatiles and work histories. No statistically significant positive regression of chromosomal aberrations on exposure estimates was found. The data from the coke oven workers were also compared with the obtained concurrently and employing precisely the same laboratory protocol from a group of male Brookhaven National Laboratory employees. The coke oven workers as a group were found to have statistically significantly elevated frequencies of chromatid aberrations and of sister-chromatid exchanges.     

Constitutive heterochromatin polymorphism and chromosome damage in viral hepatitis

The frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) were scored in relation to constitutive heterochromatin in 100 patients with viral hepatitis B, 100 patients with viral hepatitis A and 100 age- and sex-matched normal controls. 23.4%, 15% and 4% of the cells showed chromosomal aberrations in patients with hepatitis B, hepatitis A and normal controls respectively. Non-random involvement of chromosomal aberrations were also noted in chromosome 1 of patients with hepatitis B and A as compared to normal controls. The frequencies of SCEs (mean +/- S.D.) were found to be 10.40 +/- 2.83 in hepatitis B and 8.70 +/- 2.34 in hepatitis A. These values were significantly higher than the SCE frequency (mean +/- S.D.) of 5.88 +/- 2.25 observed in normal controls (P less than 0.001). The intra-chromosomal distribution of SCEs revealed a relatively increased incidence of SCEs in chromosome 1 of patients with hepatitis B and A as compared to normal controls. Analysis of constitutive heterochromatin polymorphism showed chromosome 1 qh+ to be the most frequent variant in patients with hepatitis B and A as compared to normal controls. The increased involvement of C-band variant 1 qh+ in patients with hepatitis B and A as compared to normal controls may indicate that extra heterochromatin offers additional sites for viral integration.     

Rubber solvent: a clastogenic agent that fails to induce sister-chromatid exchanges.

Rubber solvent was tested for its ability to induce chromosome aberrations and sister-chromatid exchanges in human whole blood cultures. Following exposure to relatively low rubber solvent concentrations (0.0125% and greater) significant increases in the frequencies of chromatid gaps and breaks were observed. At higher rubber-solvent concentrations (0.05% and greater) there were also significant increases in the frequency of chromosome breaks. In contrast to the increase in chromosome aberrations following rubber-solvent exposure, rubber-solvent concentrations up to the toxic level failed to produce increases in the sister-chromatid exchange frequency.     

Effects of CCNU therapy on human chromosomes

Peripheral blood lymphocytes of 9 patients under CCNU therapy were examined for frequency of sister-chromatid exchanges (SCEs) and chromosomal aberrations (CAs). 7 out of 9 patients were treated with only CCNU, whereas the remaining 2 were treated with other chemotherapeutic agents in combination with CCNU. Compared to normal individuals, a significantly increased frequency of SCE was observed in the patients before starting anticancer therapy (P less than 0.001). Increased incidences of structural changes in chromosomes were observed in cells from all the treated patients. The most frequent aberrations were of chromatid type. After administration of a single dose of CCNU, an increase in SCE frequencies was observed which remained elevated even after 6 weeks. It was concluded that increases in SCEs and CAs in lymphocytes were caused by CCNU treatment. Further studies are needed to elucidate whether any CAs observed in the present study could participate in the induction of second neoplasm.     

Chromosomal aberrations and sister-chromatid exchanges in Chinese hamster cells treated in vitro with hexavalent chromium compounds.

Chinese hamster cells (CHO line) were treated in vitro for 30--39 h with hexavalent chromium compounds (K2Cr2O7 and Na2CrO7), at concentrations ranging from 0.1 to 1.0 microgram of Cr6+ per ml, in medium containing BUdr. Chromosomal aberrations and sister-chromatid exchanges were scored on BUdr-labelled 2nd division metaphases, collected at the end of treatment and stained with Giemsa. Treatment with mitomycin C 0.009--0.030 microgram/ml) was carried out as a control for the responsiveness of the cell system to chromosomal damage. Both chromium compounds induced marked mitotic delays. Chromosomal aberrations were increased about 10-fold by exposure to Cr6+ (1.0 microgram/ml). The principal aberrations observed were single chromatid gaps, breaks and interchanges, whose frequencies increased proportionally to the concentration of chromium. Dicentric chromosomes, isochromatid breaks, chromosome and chromatid rings were also induced. The frequenyc of sister-chromatid exchanges was hardly doubled 30 h after exposure to Cr6+ at 0.3 microgram/ml, whereas it was trebled 39 h after treatment, in the cells whose division cycle had been slowed down by chromium.     

Genotoxic effects of estradiol-17beta on human lymphocyte chromosomes

The cytogenetic effect of a hormonal steroid, estradiol-17beta, was assessed in peripheral blood human lymphocyte culture. Sister chromatid exchanges (SCE) and chromosome aberrations (CA) were scored as genetic end points. Significant induction of CA was observed at 25 microg/ml and 50 microg/ml concentrations of estradiol-17beta in the absence of microsomal activation. The drug was effective in all treatments in the presence of rat liver S(9) microsomal fraction (S(9) mix) and exhibited increased frequency of chromosomal aberrations. The drug was effective in increasing the SCE frequency which was found to be maximum at the dose of 50 microg/ml concentration (i.e., 4.34+/-1.22) both with and without metabolic activation. It was found that estradiol-17beta itself and possibly its metabolites are potent mutagens beyond a particular dose in human lymphocytes.     

Cytogenetic studies on blood lymphocytes from patients with Schistosoma mansoni

Chromosomal aberrations and sister chromatid exchange (SCE) frequencies were studied in peripheral blood lymphocytes from 10 patients with Schistosoma mansoni prior to initiation of chemotherapy. The mean frequencies of chromatid and chromosome breaks for the patients were 1.80 and 2.30%, respectively, which were significantly higher (P less than 0.01) than the means 0.35 and 0.30%, scored for 20 healthy controls. Significant increase in the mean frequency of SCEs in the patients (9.1 +/- 0.5 SCE/cell) was noticeable when compared with the controls (6.2 +/- 0.1 SCEs/cell). Reductions in the lymphocyte divisions and replications in the patients were also observed. These results indicate that infection with S. mansoni could have in vivo mutagenic effects on human chromosomes.     

Chromosomal aberrations and sister-chromatid exchanges in swine

Frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) in peripheral blood lymphocytes were investigated in 56 swine from 3 herds (I, breeding sows; II and III, fattening pigs). The mean frequencies of aberrant cells (AB.C.) were 3.58 +/- 1.59%, 2.10 +/- 1.52% and 6.20 +/- 3.21%, respectively. The mean numbers of SCEs per cell were 7.73 +/- 0.86, 6.51 +/- 0.89 and 7.06 +/- 1.47, respectively. A significant difference was found between the herds under study with regard to the number of aberrant cells but not the SCE frequency. In a parallel study, the presence of aflatoxin B1, polychlorinated biphenyls (PCB), dichlorodiphenyltrichloromethylmethane (DDT), lindane, mercury, lead and cadmium in the environment of fattening pigs was investigated. The total exposure to mutagens of pigs from herd III with a mean frequency of 6.2% AB.C., was markedly higher than that of herd II with the mean frequency of 2.1% AB.C.     

Cytogenetic effects of tobacco smoke exposure among involuntary smokers

Tobacco smoke is highly genotoxic and produces chromosomal damage in several experimental systems. Active smokers have been shown to have an increased prevalence of somatic chromosome damage in their peripheral blood lymphocytes: this is seen in most cases as an increased sister-chromatid exchange (SCE) frequency and often also as increased structural chromosome aberrations (CAs). Among passive smokers, in association with exposure to environmental tobacco smoke, no such induction of chromosomal damage has been documented. In the present paper we report negative results on induction of chromosomal damage in 2 separate groups of intensive involuntary exposure to tobacco smoke, non-smoking restaurant personnel and newborn children of smoking mothers. While significant exposure in these groups is clearly seen in biochemical intake markers, e.g. cotinine and thiocyanate values in plasma, the conventional cytogenetic parameters, structural chromosome aberrations and sister-chromatid exchanges, are unable to detect the low exposures of involuntary smokers.     

Increased risk of cancer in radon-exposed miners with elevated frequency of chromosomal aberrations

In spite of the extensive use of cytogenetic analysis of human peripheral blood lymphocytes in the biomonitoring of exposure to various mutagens and carcinogens, the long-term effects of an increased frequency of chromosomal aberrations in individuals are still uncertain. Few epidemiologic studies have addressed this issue, and a moderate risk of cancer in individuals with an elevated frequency of chromosomal aberrations has been observed.In the present study, we analyzed data on 1323 cytogenetic assays and 225 subjects examined because of occupational exposures to radon (range of exposure from 1.7 to 662.3 working level month (WLM)). Seventy-five subjects were non-smokers. We found 36 cases of cancer in this cohort.Chromatid breaks were the most frequently observed type of aberrations (mean frequency 1.2 per 100 cells), which statistically significantly correlated with radon exposure (Spearman's correlation coefficient R=0.22, P<0.001). Also, the frequency of aberrant cells (median of 2.5%) correlated with radon exposure (Spearman's correlation coefficient R=0.16, P<0.02). Smoking and silicosis were not associated with results of cytogenetic analyses.The Cox regression models, which accounted for the age at time of first cytogenetic assay, radon exposure, and smoking showed strong and statistically significant associations between cancer incidence and frequency of chromatid breaks and frequency of aberrant cells, respectively. A 1% increase in the frequency of aberrant cells was paralleled by a 62% increase in risk of cancer (P<0.000). An increase in frequency of chromatid breaks by 1 per 100 cells was followed by a 99% increase in risk of cancer (P<0.000). We obtained similar results when we analyzed the incidence of lung cancer and the incidence other than lung cancer separately.Contrary to frequency of chromatid breaks and frequency of aberrant cells, the frequency of chromatid exchanges, and chromosome-type aberrations were not predictive of cancer.     

Chromosomal aberrations in peripheral lymphocytes from healthy subjects as detected in first cell division

Baseline frequencies of chromosomal aberrations were analysed in human peripheral lymphocytes and the influence of age, sex and smoking habits was considered. From 53 healthy subjects (29 males, 24 females) 54,689 exclusively first division cells (M1) were scored. The frequencies of chromosome aberrations per 1000 cells were 1.15 +/- 0.15 dicentrics (dic), 2.6 +/- 0.3 excess acentric fragments (ace) and 7.0 +/- 0.6 chromatid breaks (crb). An age dependency could only be established for ace. Between males and females no differences in any of the aberration types were observed. For heavy smokers (> 30 cigarettes per day) a significant increase was only found for dic (2.5 +/- 0.6 per 1000 cells). Dicentric frequency was compared with background levels of other studies in which results were reported also from exclusively M1 cells. Despite cell cycle control, differences between laboratories can be observed which may be partly influenced by environmental conditions. But on the other hand the mean frequency of dic (excluding heavy smokers) of 0.95 per 1000 cells reported here is consistent for more than one decade. Since such a consistency of the mean frequency of dic is reported also from another laboratory, the conclusion is drawn that especially for the detection of low-level exposures, each laboratory should establish its own base line data, otherwise, the interpretation of the findings is dependent on the selected background level from the literature.     

Induction of chromosome damage and sister-chromatid exchanges in human lymphocyte cultures by the antitumour antibiotic Neocarzinostatin

Neocarzinostatin (NCS), a chemotherapeutic antibiotic, was investigated for the ability to induce chromosomal aberrations and sister-chromatid exchanges (SCEs) in human lymphocyte cultures. It was observed that the antibiotic causes a cell-cycle delay and reduces the mitotic index. Analysis of the induced chromosomal abnormalities showed that they are mainly chromosome and chromatid breaks; while the frequency of SCEs was increased, the magnitude indicates that NCS cannot be considered a potent inducer of SCEs.     

Increased frequency of sister-chromatid exchange and chromatid breaks in lymphocytes after treatment of human volunteers with therapeutic doses of paracetamol

Paracetamol was given to 10 healthy human volunteers in 3 doses of 1 g each during a period of 8 h. Blood samples for lymphocyte cultures were taken before and 24 h after paracetamol administration. A small but significant increase was found in the frequency of sister-chromatid exchanges (SCE) after intake of paracetamol (0.187 +/- 0.030 per chromosome before and 0.208 +/- 0.024 per chromosome after). After exposure the mean frequency of chromatid breaks per 100 cells was significantly increased (2.16 +/- 1.33 versus 0.33 +/- 0.50 before exposure). Exposure of human lymphocytes in vitro showed that concentrations of paracetamol above 0.1 mM induced inhibition of replicative DNA synthesis. Increased SCE was found in lymphocytes exposed to 1-10 mM paracetamol for 2 h. Furthermore, 0.75-1.5 mM paracetamol exposure for 24 h increased the frequency of chromatid and chromosome breaks in the lymphocytes. The paracetamol-induced SCE and chromosome aberrations may be secondary effects of paracetamol-induced inhibition of DNA synthesis or due to covalent binding of paracetamol metabolite(s) to DNA.     

Effect of chronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on sister chromatid exchange levels in peripheral lymphocytes of the Rhesus monkey

Frequencies of sister chromatid exchanges and chromosomal aberrations were examined in peripheral lymphocytes of Rhesus monkeys which had been fed a diet containing 25 parts per trillion 2,3,7,8-tetrachlorodibenzop-dioxin for a period of 4 years. When compared to non-exposed control animals, no significant differences were noted for either of these cytogenetic endpoints. In addition; there was not a significant difference in sister chromatid exchange response to a challenge dose of mitomycin C in cells from 2,3,7,8-tetrachlorodibenzop-dioxin exposed animals compared to controls. Our results confirm the lack of genotoxic effects associated with 2,3,7,8-tetrachlorodibenzop-dioxin exposure.Abbreviations MMC mitomycin C - PHAA phytohemagglutinin-p - PPT parts per trillion - SCE sister chromatid exchange - TCDD 2,3,7,8-tetrachlorodibenzo-p-dioxin     

Chromosome aberrations and sister-chromatid exchanges (SCEs) in peripheral blood lymphocytes of patients suffering from poliomyelitis

The frequencies of sister-chromatid exchanges (SCEs) and various chromosome aberrations were studied in blood lymphocyte cultures of individuals suffering from polio virus infection. The frequency of SCEs was found to be within the normal range in polio patients whereas the frequency of chromatid breaks, gaps and other chromosome aberrations showed a significant (p less than 0.001) increase when compared with that of controls. It indicates that the mechanism(s) responsible for polio virus-induced chromosomal damage may not be related to or affect the molecular process(es) that functions in SCE formation.     

Cytogenetic effect of the anticancer drug epirubicin on Chinese hamster cell line in vitro

The present study demonstrated the cytogenetic effect of the anticancer drug epirubicin on cultures of Chinese hamster cell line in vitro. The cultures were exposed to the drug for 24 h at three final concentrations; 10, 20 and 40 microg/ml. All treatments were carried out in the absence of any exogenous metabolic activation system.The different types of structural chromosomal aberrations, including gaps, breaks, deletions and fragments were increased in epirubicin-treated cultures. This increase was dose dependent where there was a positive correlation between increased drug concentration and induction of structural chromosomal aberrations. Also, the numerical chromosomal aberrations, including hypodiploidy and hyperdiploidy, were increased significantly in epirubicin-treated cultures. Like structural aberrations, the increase of numerical chromosomal aberrations was also dose-dependent.The frequency of sister chromatid exchanges in cultures treated with epirubicin increased significantly and this increase was dose-dependent. On the other hand, the epirubicin significantly decreased the mitotic index in treated cultures of Chinese hamster cell line.     

Influence of Neurospora endonuclease on trenimon-induced structural chromosomal aberrations and sister-chromatid exchanges in human peripheral lymphocytes and Chinese hamster ovary cells

Human peripheral lymphocytes and Chinese hamster ovary cells were treated in the G1 phase of the cell cycle with the trifunctional alkylating agent trenimon (TRN) and post-treated with a single-strand specific endonuclease from Neurospora crassa (NE). TRN induces chromosomal aberrations of the chromatid type (CA) and sister-chromatid exchanges (SCE). NE post-treatment leads to an elevation of the frequencies of CA but not of SCEs. This indicates that TRN induced CA are the result of DNA double-strand breaks and that the SCEs originate from other types of lesions, most probably base damage.     

Chromosome damage induced by decay of 3H and 125I incorporated into DNA of Chinese hamster cells

The present study was undertaken to compare the frequency of chromatid-type aberrations in Chinese hamster cells with previous results on accumulation of unrepaired DNA-strand breaks after incorporation of 3H-TdR or 125IUdR into DNA. A linear-quadratic function was fitted by the weighted-least-square method to the data on yield of chromatid aberrations at different dpm values. Based on a significant linear response at low doses, RBE for 125I in relation to 3H was calculated for (i) chromatid breaks (17 +/- 6), (ii) the sum of isochromatid breaks and chromatid exchanges (21 +/- 9), and (iii) the total number of chromatid aberrations (18 +/- 5). Analogously, the RBE for accumulation of DNA-strand breaks was determined (13 +/- 6). Our results are consistent with the assumption that chromosomal aberrations mainly originate from unrepaired DNA-strand breaks.     

Role of non-radiation factors in forming cytogenetic effects in evacuees from a 30-km zone of the Chernobyl Nuclear Power Plant

The time-effect relationship for chromatid type aberrations, chromosome type fragments, hyperploidy and polyploidy levels in peripheral blood lymphocytes were investigated in inhabitants of t. Pripiat' and nearby villages, who were departured from the Chernobyl NPP 30-km exclusive zone during first days after the Chernobyl catastrophe. The time-course changes of the mentioned cytogenetic indices in evacuees were displayed as a gradual decline of chromosomal rearrangements and genome abnormality frequencies from the statistically elevated level in the first 1-2 years after the accident to the subcontrol meanings at the end of the 14-years observation period. In early terms after exposure the frequency of chromatid exchanges in adult men and the polyploidy level in women aged 23-35 years were sufficiently increased comparing with other evacuee subgroups. Some peculiarities of the fragment aberration frequency dynamics were shown for persons with different terms of the departure from the Chernobyl zone. The role of the combination of mutagenic factors acted in the accidental situation at Chernobyl for inducing the elevated level of cytogenetic damage in evacuees is discussed.