X-radiation-induced chromosome breakage in retinoblastoma lymphocytes

We have examined the spontaneous and X-radiation-induced chromosomal damage in normal humans and in patients with retinoblastoma using the BudR-Giemsa technique in lymphocytes cultured for 48 h. 9 sporadic unilateral non-hereditary cases, 11 hereditary cases (8 bilateral sporadic and 3 unilateral hereditary cases) and 20 healthy individuals were studied simultaneously. No difference in the spontaneous frequency of chromatid and chromosome aberrations was observed between patients and controls. After treatment with 150 rad the frequency of chromosome exchange aberrations was higher in unilateral hereditary cases than the controls (42.0% +/- 5.3 and 22.3% +/- 2.6 respectively; p = 0.05). In bilateral sporadic retinoblastoma 2 different groups were observed. A hypersensitive group showed a significant increment in radiation-induced chromosomal exchange aberrations over the control group (46.2% +/- 5.4 and 24.2% +/- 2.1 respectively; p = 0.01). The other group had a chromosomal exchange frequency similar to normal individuals (26.5% +/- 2.0 and 24.2% +/- 0.4 respectively; p = 0.10). Sporadic unilateral non-hereditary retinoblastoma had an exchange chromosomal aberration frequency similar to control individuals (26.1% +/- 2.8 and 24.6% +/- 2.7 respectively; p greater than 0.10). These results suggest that: There is no relationship between spontaneous chromosome fragility and retinoblastoma. Sporadic unilateral non-hereditary retinoblastoma has normal chromosome sensitivity to X-irradiation. Some hereditary cases of retinoblastoma are sensitive to X-rays while others behave like normals. A mutation or a submicroscopic deletion at a DNA repair locus which is independent of the retinoblastoma gene may cause this radiosensitivity.     

Bimodal distribution of sensitivity to SCE induction by diepoxybutane in human lymphocytes. I. Correlation with chromosomal aberrations

We carried out a cross-sectional analysis of sister-chromatid exchanges (SCEs) and chromosomal aberrations induced by diepoxybutane (DEB) in lymphocyte cultures from 58 normal blood donors. DEB-induced SCE frequencies were measured in all subjects and chromosomal aberrations in 18. Analysis of variance was used to assess the contributions of exposure to organic solvents, age, smoking history, alcohol and coffee consumption, and red and white blood cell counts to variations in DEB-induced SCEs. In 10 individuals, the epoxide-detoxifying enzyme, glutathione (GSH)-S-transferase mu, was also measured. We observed a bimodal distribution of DEB-induced SCEs in the study population. Approx. 24% of the individuals were twice as sensitive to the induction of SCEs by DEB as the remaining 76%. Lymphocytes from persons sensitive to SCE induction by DEB contained a 4.4-fold increase in the number of DEB-induced chromatid deletions and exchanges. Within sensitive and resistant groups, significant interindividual variations in DEB-induced SCE frequencies were noted. Cigarette smoking was weakly associated with lower SCE frequencies within each group. Genetic deficiency in GSH-S-transferase mu was not correlated with increased sensitivity to SCE induction by DEB. Sensitivity to induction of SCEs by DEB can be rapidly determined and may be a marker of sensitivity to the induction of genotoxicity by certain classes of mutagens.     

Cytogenetic study of persons occupationally exposed to ethylene oxide.

Ten persons occupationally exposed to ethylene oxide (EO), used in the sterilization of medical instruments, were studied at a hospital. The estimated concentration to which they were exposed was 60-69 ppm, TWA. Peripheral blood samples from 10 workers and 10 controls of the same age and sex were taken to determine the frequency of sister-chromatid exchanges (SCE) and chromosomal aberrations (CA). The mean frequencies of SCE/cell (X = S) were 13.27 for the exposed workers and 6.05 for controls. Chromosome aberration frequencies in exposed individuals were significantly increased compared with controls. A significant relationship between the frequencies of SCE and CA and EO exposure was demonstrated. Blood chemistry parameters such as urea, creatinine, uric acid, lactic dehydrogenase, glutamic oxaloacetic and pyruvic transaminases, luteinizing gonadotropin and follicle stimulating gonadotropin and thyrotropin were also measured and found to be within the normal range.     

Cytogenetic study of persons occupationally exposed to ethylene oxide

Ten persons occupationally exposed to ethylene oxide (EO), used in the sterilization of medical instruments, were studied at a hospital. The estimated concentration to which they were exposed was 60–69 ppm, TWA. Peripheral blood samples from 10 workers and 10 controls of the same age and sex were taken to determine the frequency of sister-chromatid exchanges (SCE) and chromosomal aberrations (CA). The mean frequencies of SCE/cell (X = S) were 13.27 for the exposed workers and 6.05 for controls. Chromosome aberration frequencies in exposed individuals were significantly increased compared with controls. A significant relationship between the frequencies of SCE and CA and EO exposure was demonstrated. Blood chemistry parameters such as urea, creatinine, uric acid, lactic dehydrogenase, glutamic oxaloacetic and pyruvic transaminases, luteinizing gonadotropin and follicle stimulating gonadotropin and thyrotropin were also measured and found to be within the normal range.     

Cytogenetic effects of methyl isocyanate exposure in Bhopal

Summary Among human survivors following the methyl isocyanate (MIC) gas tragedy the major complaints have been related to deep-seated suffocation, terrible pain in breathing, and severe ocular irritations. In order to assess the possible genetic effects we have used lymphocyte cultures and screened chromosomes by two techniques; one by looking for chromosomal aberrations and the other by estimating sister-chromatid exchange (SCE) frequencies. Both these paramaters are good indicators of genetic damage in chromosomal DNA. SCE frequencies in lymphocytes have been increased more than three times in MIC-exposed persons. The results were compared to two groups of controls (one group comprising persons present in the same house; the second group of persons were chosen from distant places, 20–50 km away from the incident). Chromosomal breaks have been observed in 10 out of 14 MIC-affected people (71.4%) studied while only 6 out of 28 (21.4%) controls had chromosomal breaks. Some MIC-exposed persons had chromatin bodies in addition to the normal 46 chromosomes. These observations suggest that chromosomal DNA has been damaged.     

Differential sensitivity of peripheral blood lymphocytes of untreated leprosy patients to mitomycin C

The effects of a bifunctional alkylating agent mitomycin C (MMC), an effective inducer of chromosome aberrations and sister-chromatid exchanges (SCEs), have been studied in untreated leprosy patients. This was done to study the mutagen sensitivity of the leprosy patients. The frequency of chromosomal aberrations induced by MMC (conc. 0.01 microgram/ml) was 2.5% in controls, 3.6% in paucibacillary (PB), and 6.8% in multibacillary (MB) patients. The difference in the frequency of MMC-induced chromosome aberrations between the 3 groups studied was highly significant (p less than 0.01). Cultures grown with MMC showed the frequency of SCEs/cell to be 12.70 +/- 1.19 in controls, 19.97 +/- 3.51 in PB, and 29.66 +/- 5.92 in MB patients. The differences in the frequency of MMC-induced SCEs between the 3 groups were found to be highly significant (p less than 0.01). The enhanced frequencies of spontaneous and MMC-induced chromosome aberrations and SCEs observed in PB and MB patients indicate a clear differential mutagen sensitivity between PB and MB patients who are known to have different immunological status and thereby differ in the severity of the disease.     

Biomonitoring of genotoxic exposure among stainless steel welders.

A biosurvey in the Danish metal industry measured the genotoxic exposure from stainless steel welding. The study comprised measurements of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), unscheduled DNA synthesis (UDS) in peripheral lymphocytes and serum immunoglobulin G. Environmental monitoring of welding fumes and selected metal oxides, biomonitoring of chromium and nickel in serum and urine and mutagenic activity in urine, and evaluation of semen quality were also done. Manual metal arc (MMA) welding and tungsten inert gas (TIG) welding were the dominant welding processes. A higher frequency of chromosomal aberrations, classified as translocations, double minutes, exchanges and rings, was observed in stainless steel welders than in non-welders. SCE was lower in welders working with both MMA and TIG welding than in reference persons. N-Acetoxy-N-acetylaminofluorene (NA-AAF)-induced UDS was lower in 23 never-smoking welders than in 19 unexposed never-smokers. Smoking was a confounding factor resulting in significantly higher CA, SCE, NA-AAF binding to DNA and mutagenic activity in urine. Age was also a confounder: CA, SCE, NA-AAF binding to DNA and UDS increased significantly with age. No significant correlation between SCE and CA or between CA and UDS was found. UDS decreased significantly with increasing lymphocyte count and a higher lymphocyte count was seen in MMA welders than in reference persons and in smokers than in non-smokers. Differences in the composition among lymphocytes in exposed persons compared with non-exposed are suggested. MMA welding gave the highest exposure to chromium, an increased number of chromosomal aberrations and a decrease in SCE when compared with TIG welding. Consequently improvements in the occupational practice of stainless steel welding with MMA is recommended.     

Chromosome aberrations in individuals occupationally exposed to ethylene oxide, and in a large control population

Chromosome aberration frequencies in 61 employees potentially exposed to ethylene oxide (ETO) were compared with those in unexposed control groups. We studied 3 worksites with differing historical ambient levels of ETO. Within worksites, groups were classified as high potential exposed, low potential exposed, or controls. Further control groups including an off-site community control group were added to give a total of 304 control individuals. Blood samples were drawn several times over a 24-month period. Aberrations were analyzed in 100 cells per sample after culture for 48-51 h. Worksites I, II and III respectively represented increasing levels of potential ETO exposure. At worksites I and II, no consistent differences in aberration frequencies were found among groups. At worksite III aberration frequencies in potentially exposed individuals were significantly increased compared with controls. The frequencies of cells with aberrations were 5.6% for the 2 individuals in the high potential exposure category and 2.6% for 23 persons in the low potential exposure group. The overall frequency of cells with aberrations in the matched control individuals was 1.4%. In the total control group of 304 individuals we found significant increases in aberrations associated with smoking and with increasing age. We have also reported previously an association between sister-chromatid exchange (SCE) frequency and ETO exposure (Stolley et al., 1984). When aberration frequencies were compared with levels of SCEs there was only a weak overall association. The correlation was found in potentially exposed but not in control groups, and for any individual, one observation could not be used to predict the other.     

A cytogenetic study of men environmentally and occupationally exposed to airborne pollutants.

The level of sister-chromatid exchanges (SCE), high-frequency cells (HFC), chromosomal aberrations (CA) as well as the proliferation rate index (PRI) were measured in peripheral blood lymphocytes from three groups of volunteers. The environmentally exposed donors were residents from the vicinity of a coke factory; the occupationally exposed persons were cokery workers, while rural region inhabitants served as a control group. Compared with the control group, statistically significant increases of SCE and HFC, as well as decreased cell kinetics (PRI) were observed for both occupationally and environmentally exposed groups. The effect was especially pronounced when only smokers were taken into account. A statistically significant increase of CA was observed in the environmentally exposed group when CA including gaps (CA + G) were evaluated. The proportion of HFC was found to be the most sensitive method to detect genetic effects on the tested human population. This study demonstrates the usefulness of all 4 biomarkers (SCE, HFC, CA and PRI) in monitoring populations exposed to ambient pollution and clearly indicates effects from residential as well as occupational exposure to industrial air pollutants.     

Cytogenetic damage in workers exposed to ethylene oxide

Sister-chromatid exchanges (SECs) and chromosomal aberrations (CAs) were detected in the peripheral lymphocytes of 41 sanitary workers exposed to ethylene oxide (EO) in the sterilizing units of 8 hospitals in the Venice Region. The first group (19 workers) was exposed to 10.7 +/- 4.9 ppm EO, expressed as the time-weighted average concentration for an 8-h working day (TWA/8 h conc.), and the second group (22 workers) to 0.35 +/- 0.12 ppm. Each exposed worker was paired with a control of similar age and smoking habits. A highly significant (P less than 0.001) increase in the mean frequency of SCEs was found in the higher exposure group, 14 (74%) exposed subjects having significantly increased levels of SCEs compared to their matched controls. In the lower exposure group, the increase in mean frequency of SCEs was lower, though still significant (P less than 0.05): 7 (33%) exposed subjects had higher and 1 (5%) had a lower SCE level than the matched controls. From the first group, 10 subjects, 7 of whom had increased SCE levels, were reanalysed 12-18 months after their exposure had been lowered or interrupted: in only 2 of them the SCE level was significantly decreased. A statistically significant correlation between SCE frequency and level of EO exposure (TWA/8 h conc.), as well as a multiple correlation between SCE level and EO exposure, smoking and age were found. However, no interaction could be detected between EO exposure and smoking in the induction of SCEs. In controls, SCE frequency was correlated with smoking and age. In the higher exposure group, the number of both chromatid- and chromosome-type aberrations, independent of gaps, was significantly increased, whereas in the lower exposure group only the frequency of chromosome-type aberrations, excluding gaps, was statistically higher than in controls. The level of CAs remained to a great extent unchanged in the 10 subjects re-examined at a later stage after lowering or halting exposure. Taking the group as a whole, the frequency of cells with total CAs was found to be weakly (P = 0.05) correlated with EO exposure, and was not correlated with smoking, age or SCE frequency.     

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.     

Incidence of chromosome aberrations in hothouse workers and the in vitro sensitivity of their lymphocytes to the cytogenetic action of dimatif

The cytogenetical survey of eight persons working in greenhouse and occupationally contacting with a complex of pesticides has shown a significant increase of chromosomal aberration level in comparison with the control group. It is determined that the cytogenetic effect of the greenhouse's workers differed significantly from that of the control group when lymphocytes of the examined persons were treated by the potent mutagen dimatyph in vitro. The occupational group on the whole was more sensitive than control persons to the clastogenic action of dimatyph (43.0 +/- 2.2 and 28.7 +/- 2.4%, respectively). An assumption is advanced on the modifying influence of the pesticide complex on the frequency of induced chromosomal aberrations in vitro.     

Chromosome and SCE analysis in peripheral lymphocytes of persons occupationally exposed to cytostatic drugs handled with and without use of safety covers

The frequency of structural chromosome aberrations and sister-chromatid exchanges in peripheral blood lymphocytes of nurses handling cytostatic drugs without a safety cover is compared with that of individuals doing this work exclusively under a safety cover and with that of nurses working under similar conditions but not handling cytostatics. The mean yield of dicentric chromosomes, (4.3 +/- 0.7)/1000 cells, and acentric fragments, (15.4 +/- 1.4)/1000 cells, in the occupationally exposed group is significantly increased in comparison to individuals working with protection (dic: (1.1 +/- 0.4)/1000 cells, ace: (11.2 +/- 1.2)/1000 cells) and nurses not handling cytostatics (dic: (2.1 +/- 0.5)/1000 cells, ace: (9.9 +/- 1.1)/1000 cells). The frequency of chromatid breaks and SCE is not significantly different between these groups (p greater than 0.05).     

Clastogenic effect of pesticides in peripheral lymphocytes of cotton-field workers.

We studied clastogenic effects in peripheral lymphocytes of cotton-field workers who were exposed to different pesticides. All the cells were grown in RPMI 1640 medium for 48 and 72 h. The type of aberrations observed in the exposed group are gaps, breaks, dicentrics, exchanges, rings and polyploidy. The frequency of total chromosomal aberrations increased significantly in male pesticide applicators when compared to controls. A significant decrease in mitotic index was observed in the exposed group as compared to the control group. The 48-h cultures showed high incidence of chromosomal aberrations and low mitotic index when compared to 72-h cultures. The difference in chromosomal aberrations between 48- and 72-h cultures was not significant. 24 out of 26 individuals showed ill health effects such as severe giddiness and nervous disorders.     

The effect of valproic acid on SCE and chromosome aberrations in epileptic children

Sister-chromatid exchange (SCE) and chromosome aberrations have been studied in peripheral lymphocytes of 20 epileptic children treated in monotherapy with valproic acid (VPA) for 6-52 months and in 2 matched control groups. The frequencies of SCE in the VPA-treated epileptic children were significantly higher than in the 2 control groups (p less than 0.01); rates of chromosome aberrations were slightly higher but not significantly different from the 2 control groups. We also examined SCE in 10 epileptic children before and after they took sodium valproate for 6-7 months; there was a statistically significant change in SCE following VPA. 9 normal children whose lymphocytes were exposed in vitro to sodium valproate (5-20 micrograms/ml) showed a significant increase in SCE.     

Genetic aspects of nonchromaffin paraganglioma

Summary Sister chromatid exchanges (SCE) and structural chromosome aberrations were analyzed in peripheral blood lymphocytes of 100 individuals, and correlated to age and sex. No correlation was found between the frequency of SCE and age, but older individuals had significantly more structural aberrations than younger. Females had significantly more SCE as well as structural chromosome aberrations than males. The positive correlations of SCE and structural aberrations to age and sex were also significant when these factors, as well as smoking habits, were taken into consideration in an analysis of covariance.     

Chromosomal aberrations in humans as genetic endpoints to assess the impact of pollution

The chromosomal aberration assay with peripheral blood lymphocytes has been used routinely during the last three decades to survey exposure of humans to various genotoxic agents. A large number of biomonitoring studies are based on this genetic endpoint. A great deal of data exists on occupational, life-style or medical exposure situations but less evidence of the validity of the assay is available with regards to environmental exposure. In the present paper we report our investigations on the impact of pollution in two different populations using chromosomal aberrations in human peripheral blood lymphocytes as a biomarker of chronic exposure to heavy metals and dioxins/furans for a long period and as a biomarker of acute exposure to accidentally released vinyl chloride in the air. In order to study genotoxic effects (chromosomal aberrations) of heavy metals and dioxins/furans, 52 exposed individuals from a polluted area were compared to 51 matched controls from a distant non-industrialized area. A statistically significant increase was observed in the frequency of chromosomal aberrations in peripheral blood lymphocytes from the exposed population (1.90% aberrant cells vs. 1.11% for the controls). In the case of the vinyl chloride accident, chromosomal aberrations were analyzed in peripheral blood lymphocytes from 29 potentially exposed and 29 non-exposed individuals (matched controls). The exposed group showed a statistically significant increase in the frequency of aberrant cells (1.47% vs. 1.07% for the controls).     

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.     

Sister-chromatid exchange frequencies in postmenopausal hormone replacement patients

Our objective was to evaluate the frequency of sister-chromatid exchange (SCE) during hormone replacement therapy in postmenopausal women. Thirty-four asymptomatic postmenopausal women with a minimum 12 months since last menstrual period and surgical menopausal women were included in the study. Seventeen patients who were in spontaneous menopause were administered conjugated estrogen and medroxyprogesterone acetate (group A), and the others who were in surgical menopause were given 17beta-estradiol only (group B). Peripheral lymphocytes were obtained at the beginning and at the end of the third month of therapy. The mean age of the patients was 50. 67+/-4.79. There were statistically significant differences in terms of SCE frequencies between pre- and posttreatment levels of both groups (p<0.001 and p=0.003, respectively). It is likely that estrogens with or without progesterone have an effect in increased SCE frequency and this issue may be an evidence for the increased potential for malignancies.     

Cytogenetic analysis in workers occupationally exposed to nickel carbonyl

Chromosomal aberration and sister-chromatid exchange (SCE) base-line frequencies and SCE frequencies induced by 10 ng/ml mitomycin C (MMC) were analysed in cultured peripheral lymphocytes of 65 workers occupationally exposed to nickel carbonyl Ni(CO)4. The subjects were divided into 4 groups: (1) control; (2) exposed to nickel carbonyl (= exposed); (3) cigarette smokers; (4) smoking-exposed. The results show that there are no significant differences in chromosomal aberration frequencies, breaks or gaps, between the various groups. However, the SCE base-line frequency of the smoking-exposed group, with an average of 7.7/cell, was significantly higher than that of the control group, with an average of 6.5/cell (P less than 0.01), and also than that of the exposed group with an average of 5.9/cell (P less than 0.01). Similarly, the SCE frequency induced by 10 ng/ml MMC in the smoking-exposed group which averaged 15.5/cell was significantly higher than that of the control group (average of 13.2/cell (P less than 0.05], and also than that of the exposed group with an average of 12.3/cell (P less than 0.01). Under our experimental conditions, it may be that the level of exposure was not high enough to elicit an increase in chromosomal aberrations and SCE frequencies in the non-smoker exposed group. The fact that an increase in SCE frequencies was only found in the smoking-exposed group implies that the two factors, smoking and exposure to nickel carbonyl, are jointly responsible for the result.