Sister-chromatid exchanges in human lymphocytes after a non-S-phase incubation period to allow excision DNA repair-in vitro exposure to N-acetoxy-2-acetylaminofluorene and ethylene oxide

Sister-chromatid exchanges (SCE) were analyzed in human peripheral blood lymphocytes at the baseline level, after induction of DNA damage by N-acetoxy-2-acetylaminofluorene (NA-AAF) and ethylene oxide (EO), and after a subsequent 18-h DNA-repair incubation period. There was a significant difference between the baseline SCE frequencies as compared to those after 1 h of NA-AAF or EO treatment. There was no significant difference between the SCE frequencies after 1 h of NA-AAF treatment and those after 18 h of DNA-repair incubation, suggesting that only a low level of NA-AAF damage to DNA had been removed. However, there was a significant difference between the SCE frequencies after 1 h of EO treatment and those after 18 h of DNA-repair incubation, indicating that a significant level of EO induced DNA lesions had been repaired. Thus, it seems likely that the EO induced DNA damage is more easily recognized, and hence more rapidly repaired than the NA-AAF induced damage. The reason for this may be the different chemical nature of the DNA lesions induced, which, in turn, leads to different kinetics of DNA repair.     

Sister-chromatid exchanges in mouse embryos after exposure to ultrasound in utero

Mouse embryos at 2 stages of development were exposed to ultrasound. The bone-marrow cells of the mother, the whole embryo, and the embryonic liver cells were analyzed. There was no consistent increase of sister-chromatid exchanges. Furthermore, the thermal effect of ultrasound did not appear to influence the frequency. Thus, ultrasound doses much higher than those used in clinical diagnosis do not induce cytogenetic damage as assayed by sister-chromatid exchanges.     

The metabolism of ethylene to ethylene oxide in cultivars of Vicia faba: Relationship with waterlogging resistance

The ability of cultivars of Vicia faba L. to metabolize ethylene and the resistance of such cultivars to waterlogging was assessed. Those cultivars showing the highest resistance to waterlogging also had the ability to rapidly metabolize ethylene. It is suggested that a causal relationship may exist between the two processes.     

Biological and chemical monitoring of occupational exposure to ethylene oxide

Studies were carried out on two populations occupationally exposed to ethylene oxide (EtO) using different physical and biological parameters. Blood samples were collected from 9 hospital workers (EI) and 15 factory workers (EII) engaged in sterilization of medical equipment with EtO and from matched controls (CI and CII). Average exposure levels during 4 months (the lifespan of erythrocytes) prior to blood sampling were estimated from levels of N-(2-hydroxyethyl)valine adducts in hemoglobin. They were significantly enhanced in EI and EII and corresponded to a 40-h time-weighted average of 0.025 ppm in EI and 5 ppm in EII. Exposures were usually received in bursts with EtO concentrations in air ranging from 22 to 72 ppm in EI and 14 to 400 ppm in EII. All samples were analyzed for HPRT mutants (MFs), chromosomal aberrations (CAs), micronuclei (MN) and SCEs. MFs were significantly enhanced by 60% in EII but not in EI. These results are the first demonstration of mutation induction in man by ethylene oxide. CAs were significantly enhanced in EI and EII by 130% and 260% respectively. MN were not enhanced in EI but significantly in EII(217%). The mean frequency of SCEs was significantly elevated by 20% in EI and by almost 100% in EII. SCE was the only parameter that allowed distinction between daily and occasionally exposed workers in EII. An interesting finding in exposed workers was the large increase of the percentage of cells with high frequencies of SCE (3–4 times in EI and 17-fold in EII).

The relative sensitivity of endpoints for detection of EtO exposure in the present investigation was in the following order: HOEtVal adducts > SCEs > chromosomal aberrations > micronuclei > HPRT mutants.     

Sister-chromatid exchanges in lymphocytes from patients with Schistosoma hematobium

Sister-chromatid exchange (SCE) frequencies were studied in peripheral blood lymphocytes from 19 patients (13 males and 6 females) with Schistosoma hematobium, prior to the initiation of chemotherapy. The mean frequency of SCE per metaphase for the patients (both sexes) was 10.4 +/- 4.2 which was significantly higher (P less than 0.01) than the mean SCE (6.4 +/- 1.1) score for 35 healthy controls. A highly significant reduction in lymphocyte division and delay in cell-cycle progression as a result of infection were also noticed. These data indicate that infection with S. hematobium could increase SCEs in the host somatic cells.     

Toxicity potential of residual ethylene oxide on fresh or frozen embryos maintained in plastic straws

The toxic effects of residual ethylene oxide (EtO), a frequently used gas-sterilant, on embryos either frozen for long-term purposes or stored acutely for 30 min to 9 hr in a fresh condition in 0.25-ml straw containers were evaluated. In Experiment 1, fresh embryos were frozen (using conventional technology) in straws previously aerated for 0 hr to 8 mo after EtO sterilization. With the exception of the 8-mo group in which survival and quality ratings were depressed, embryo viability was not affected significantly by short-term prefreeze and post-thaw exposure to EtO residues. Experiment 2 was conducted to analyze the influence of prefreeze exposure to EtO residues on embryo development in vitro for embryos temporarily stored in previously sterilized straws aerated for different intervals. Compared to non-EtO-sterilized control straws, the development, quality, and viability of embryos exposed to EtO-treated straws were compromised (p < 0.05) as the aeration interval decreased and the exposure interval increased. The combined results of both experiments indicate that EtO-treated straws can be used to cryopreserve gametes efficiently, but only if the aeration interval is ≥72 hr and the prefreeze duration of exposure is ?3 hr.     

Sister-chromatid exchanges in lymphocytes of workers exposed to trichloroethylene

To detect mutagenic effects of trichloroethylene (TCE) on humans, sister-chromatid exchanges (SCEs) were analyzed in lymphocytes of 22 workers occupationally exposed to TCE and 22 matched controls. Although urinalysis in the workers revealed their obvious exposure to TCE, no increase in SCE frequencies was found in lymphocytes of the workers. SCE analysis in lymphocytes could not detect mutagenic effects by occupational exposure to TCE on humans.     

Sister-chromatid exchanges in lymphocytes from infants with Down's syndrome

Sister-chromatid exchange (SCE) frequencies were studied in blood lymphocytes from 12 patients (3 females and 9 males) with Down's syndrome (DS). The mean frequency of SCE per metaphase for the patients (both sexes) was 9.2 +/- 0.8 which was significantly higher (P less than 0.01) than the mean SCE value (5.1 +/- 0.2) scored for 16 healthy infants (8 females and 8 males). A significant increase in the mean frequency of SCE in 12 parents of infants with DS (8.7 +/- 0.9 SCE/cell) was noticeable when compared with 20 parents of normal infants (6.3 +/- 0.1 SCE/cell). Increases in cellular division with reduction in their replication were also observed in patients with DS. Treatment with mitomycin C (0.05 micrograms/ml), hycanthone (0.1 micrograms/ml) and gamma-radiation (0.1 Gy) revealed a significant (P less than 0.01) increase in frequencies of SCE in DS lymphocytes and in those of their parents as compared to controls. These data may reveal a familial hypersensitivity reaction to these agents. The results indicate a genomic instability and deranged DNA-repair mechanisms which are accentuated by exposure to mutagenic agents, the underlying causal factor for which might be genetic.     

Effects of ethylene oxide on soil microbial content and some soil chemical characteristics

The effects of ethylene oxide (EtO) on survival of soil microflora and on selected chemical properties of a sandy-loam soil were examined. Soil sterilization was achieved after 8 hours exposure to EtO. Ethylene oxide treatment increased soil pH and organic matter content. Extractable Mn and Fe slightly increased whereas P content decreased. Total N was not affected by the treatment.     

Sister-chromatid exchanges and chromosomal aberrations in a population exposed to pesticides

Sister-chromatid exchanges (SCE) and chromosomal aberrations were studied in a population of floriculturists occupationally exposed to organophosphorus, carbamate and organochlorine pesticides. Blood samples from 36 individuals from a community of 154 persons of asiatic origin were obtained. Among the group sampled, 21 individuals exhibited at least one symptom of chronic intoxication. SCE analysis was performed in 14 symptomatic and 13 asymptomatic persons. The asymptomatic group showed a SCE frequency of 5.47 +/- 1.03 and the symptomatic group a frequency of 6.45 +/- 1.19. Comparison between both groups with the Mann-Whitney 'U' test revealed a significant difference (p 0.0409). Case-control analysis of 9 pairs matched by sex and age also showed significant differences between both groups (p 0.0104). In contrast, the frequencies of chromosomal aberrations were not correlated with intoxication symptomatology, though a significant increment of exchange-type aberrations in relation to a group of non floriculturists was observed in the population studied.     

Effectiveness and efficiency of ethyl methanesulphonate and ethylene oxide for the induction of mutations in rice

A comparison of the mutagenic efficiency and effectiveness of ethyl methanesulphonate (EMS) and ethylene oxide (EO) on two different genotypes of rice showed that the mutagenic efficiency sharply decreased with increase in the concentration of EO whereas the efficiency of EMS increased with an increase in the concentration. The effectiveness was inversely proportional to dose of EO whereas it varied little with an increased dose of EMS.     

Sister-chromatid exchanges in human lymphocytes exposed in vitro to therapeutic ultrasound

Human lymphocytes were exposed in vitro to therapeutic levels of ultrasound (1 W/cm2, CW, 0.87 MHz, durations of 80 and 160 sec). There were no significant differences in sister-chromatid exchange frequencies between controls and ultrasound-exposed cells. Exposure of lymphocytes to the positive control (mitomycin C) resulted in a significant increase in sister-chromatid exchanges. The data do not verify a report by Stella et al. (Mutation Res., 138 (1984) 75-85) that such exposures result in increased frequencies of SCEs.     

Sister-chromatid exchanges in lymphocytes in women with cancer of the breast

Examination of sister-chromatid exchanges (SCE) in lymphocytes may be useful for the evaluation of exposure to mutagens/carcinogens. Information of a possible association between SCE and cancer is scarce. We therefore examined SCE in peripheral lymphocytes in 131 women, aged 17–90 years (median 51.8 years), coming to operation because of a tumor of the breast. Venous blood samples were cultivated during PHA stimulation in the presence of BrdU. After treatment with colcemid^(R), fixation, treatment with bisbenzimide and staining with Giemsa, 30 metaphases were scored in each specimen. 52 patients with peroperatively demonstrated carcinoma of the breast had 9.39 ± 0.17 SCE/cell and the remaining 79 women with non-malignant fibroadenomatosis had 9.88 ± 0.18 SCE/cell.By multiple regression analysis it appeared that the character of the tumor, the patient's age, hormone treatment and preoperative examination by mammography all were without significant influence on the SCE rate. A statistically significant correlation was found between SCE and cigarette smoking. The 45 cigarette-smoking patients had 10.49 ± 0.23 SCE/cell compared with 9.26 ± 0.13 SCE/cell in the 86 non-smokers. It was concluded that spontaneous SCE in lymphocytes is not an indicator of carcinoma of the breast.     

Involvement of ethylene and nitric oxide in cell death in mastoparan‐treated unicellular alga Chlamydomonas reinhardtii

This work demonstrates a contribution of ethylene and NO (nitric oxide) in MP (mastoparan)‐induced cell death in the green algae Chlamydomonas reinhardtii. Following MP treatment, C. reinhardtii showed massive cell death, expressing morphological features of PCD (programmed cell death). A pharmacological approach involving combined treatments with MP and ethylene‐ and NO‐interacting compounds indicated the requirement of trace amounts of both ethylene and NO in MP‐induced cell death. By employing a carbon dioxide laser‐based photoacoustic detector to measure ethylene and a QCL (quantum cascade laser)‐based spectrometer for NO detection, simultaneous increases in the production of both ethylene and NO were observed following MP application. Our results show a tight regulation of the levels of both signalling molecules in which ethylene stimulates NO production and NO stimulates ethylene production. This suggests that, in conjunction with the elicitor, NO and ethylene cooperate and act synchronously in the mediation of MP‐induced PCD in C. reinhardtii. To the best of our knowledge, this is the first report on the functional significance of ethylene and NO in MP‐induced cell death.     

Sister-chromatid exchanges and chromosal breakage in patients treated with cytostatics.

The frequency of structural chromosomal rearrangements and sister-chromatid exchanges (SCEs) was investigated in short-term phytohemagglutininstimulated lymphocyte cultures by means of bromodeoxyuridine substitution and fluorescence plus Giemsa (FPG) staining technique. Both these parameters were significantly increased in patients treated with comparatively low doses of cyclophosphamide, busulphan and adriamycin. The increased SCE rate was proportional to the number of chromosome breaks, the ratio of SCE to breaks being about 100:1. The increase in the SCE number was maintained for several months after the termination of cytostatic therapy, when the conventional analysis of chromosome breaks yielded normal results. Normal SCE values were obtained in two patients treated with low doses of fluorouracil.     

In vivo and in vitro ethylene oxide exposure of human lymphocytes assessed by chemical stimulation of unscheduled DNA synthesis

Factory workers exposed to ethylene oxide (EO), 0.5–1.0 ppm in factory air, together with matched controls from the same factory, were examined for evidence of toxic exposure by measurement of unscheduled DNA synthesis (UDS) induced by N-acetoxy-2-acetylaminofluorene (NA-AAF) and of chromosome aberrations in peripheral lymphocytes.The total chromatid gaps plus breaks were significantly elevated and NA-AAF-induced UDS was significantly reduced in the EO-exposed group as compared with the unexposed control group. The NA-AAF-induced UDS values negatively correlated to the duration (yr) of EO exposure (r = ?0.45, p < 0.02) and the number of chromosome breaks (r = ?0.61, p < 0.05), indicating an inhibition in vivo of DNA-repair capacity by EO. These data were verified in vitro by biochemical and autoradiographic studies of EO-induced UDS in human blood cells. Above 2 mM EO, UDS was inhibited in lymphocytes whether they were cultured for 24 or 122 h after alkylation with EO. Even at the subtoxic EO dose of 0.1 mM, lymphocytes were sensitized to additional exposures of NA-AAF, so that cytotoxicity was increased to 40% compared with 5% for the controls even though UDS was unaffected.It is concluded that EO was toxic to lymphocytes, even when they were sensitized at non-toxic EO doses to the cytotoxic action of other mutagens (e.g. NA-AAF), and the cells that did survive above 2 mM EO were inhibited in their DNA-repair capacity as judged by reduced UDS.