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The genotoxicity of cannabis smoking was evaluated by means of the sister-chromatid exchange (SCE) test. The SCE test is considered to be a sensitive tool for the discovery of genotoxic agents in the environment. Twenty-two tobacco smokers and 22 persons smoking both tobacco and cannabis were compared. Our findings showed that smoking in itself enhanced the SCE level significantly (18.5%) compared to a group of non-smokers, but adding smoking of cannabis to tobacco smoking did not affect the SCE level further. Based on our observations cannabis smoking could not be considered genotoxic.

During the last decades several in vitro assays for measurement of genotoxic exposure have been developed. Exposure of humans to genotoxic products in their workplaces and the environment may be evaluated by means of the sister chromatid exchange test (SCE), which visualize exchange of DNA material between sister chromatids of a chromosome. This thesis deals with the development of SCE methodology and screening of confounding factors to make the method useful in population monitoring of genotoxic exposure of chemicals in vivo. Human lymphocytes are cultured under standardized conditions. The cells are prepared for chromosome analysis by means of new-developed apparatuses treating 12 samples simultaneously. By this method the preparation is speeded up and breathing of glacial acetic acid is minimized. Slides are prepared and stained. The staining procedure includes irradiation of the slides with long wave UV light. The light source has been optimized with regard to simplicity and spectral distribution to fit the absorption spectrum of the dye bisbenzimid. The irradiation time and dose to produce distinct harlequin stained chromosomes has been found. Population screening demands analysis in microscope of a great number of chromosomes. The working time at microscope is long and improvement of ergonomics and automation to speed up the procedure was obtained by development of a special microscope which projects the picture of SCEs at table level. The scanning table was motorized. These changes gave excellent ergonomic proporties as fixed positions of the eyes and hands were avoided. The system is fast and flexible and may semiautomatically produce karyotypes. By pointing out SCEs the system automatically registers SCE number, cell coordinates, mitosis quality and perform statistics. The statistical model which best describe the distributions of SCE data has been analysed. This was a negative binomial distribution, which is close to the Poisson distribution. The transformation y = (S).5 + (S + 1).5 follows a normal distribution. Variances of the transformation of the sum of SCEs in 30 cells within subjects and between subjects have been calculated, and on that basis the demands to sample size have been calculated. To avoid to make false statements about a connection between an exposure and SCE a detailed knowledge of confounding factors is essential. Of endogenous factors gender, age, race, and heredity have been considered. Of these gender and age contribute to the variation in SCE. Very high SCE level has been found in healthy members of a family and such cases have to be excluded from exposure studies.(ABSTRACT TRUNCATED AT 400 WORDS)

The potential mutagenicity of inhalation anaesthetics was investigated by the sister chromatid exchange (SCE) test system applied to lymphocytes in peripheral blood drawn from patients before and after anaesthesia. Twenty-one women, aged 39-82 years (median 57.7 years) received halothane for 75-180 min (median 125 min). Fourteen other patients, aged 45-90 years (median 67.5 years) received enflurane for 90-180 min (median 130 min). In both groups the numbers of SCEs were unchanged immediately following anaesthesia and 5 days after. It was concluded that, by this method, comprising human cells exposed in vivo, there was no indication of mutagenic effect of short-term exposure to halothane or enflurane in anaesthetic concentrations.

Sister chromatid exchange (SCE), which is considered a sensitive method in evaluation of mutagenicity and may be an indicator of carcinogenicity, was determined in lymphocytes from 8 patients with severe psoriasis who underwent treatment with oral methotrexate (MTX). During the treatment period (median 118 days, range 50-298 days) a significant increase in SCE compared to the pretreatment value was found in 1 patient only. It is concluded that no long-term damage as measured by SCE occurs in lymphocytes from psoriasis patients treated with MTX.

The mutagenicity of the chromosomes of the peripheral lymphocytes of 147 Greenlandic Eskimos living in the district of Angmagssalik, Greenland, and in Denmark, was evaluated by means of the sister chromatid exchange (SCE) test. Thirty cells from each person were examined. The purpose of the investigation was to determine if there was any relationship between mutagenic activity and diet, and hence the elements selenium, cadmium, mercury and lead. The probands were divided into three groups according to their intake of seal meat or industrially prepared food: group 1, those eating seal at least six times per week; group 2, two to five times per week; and group 3 once each week or not at all. The statistical analysis was performed by means of multiple linear regression analyses, with diet, living district, sex, age, tobacco smoking, and blood lead and mercury concentrations as variables. Forty-eight percent of the variation in SCE could be explained by differences in diet, living district, age, and tobacco consumption. Groups 1 and 2 had a 1.7 and 0.65 times higher SCE/cell, respectively, than group 3. For every additional 10 years of age of the probands, the SCE/cell increased by 0.4, and for every 10 g of tobacco smoked per day the SCE/cell was 0.7 higher compared to non-smokers. When priority was given to blood Hg concentration in the calculation, 16.3% of the total variation in SCE/cell could be explained. An increase in the blood Hg concentration of 10 micrograms l-1 corresponded to an increase of 0.3 SCE/cell. In 92 individuals blood Se and Cd concentrations were also analysed. The variables, tobacco smoking, diet, living district and Cd explained 53% of the total variation in SCE. Giving priority to the blood Hg and Cd concentrations, explained 21.4% of the total variation in SCE/cell. An increase of 10 micrograms l-1 in blood Cd and Hg corresponded to an increase in SCE/cell of 0.7 and 0.2, respectively. No influence on the SCE/cell could be attributed to the blood Pb and Se concentrations. Evaluated by the SCE test, seal diet, smoking, living district and blood Hg and Cd concentrations all contribute to mutagenicity in Greenlandic Eskimos, with seal diet as the most important of the factors examined.

Sister chromatid exchanges (SCE) and sister chromatid exchange points (SCE-points) were counted in lymphocytes in peripheral blood drawn from hospital personnel exposed to anesthetics as well as from persons not exposed. A total of 38 healthy persons were investigated, representing female nurse anaesthetists, male physicians practising anaesthesia, female nurses from the intensive care unit, and female secretaries. The mean SCE number per cell for each person was used as the variable, and the Mann-Whitney U-test was applied to test for differences between groups. The group of secretaries seemed to differ from the other three groups, which appeared identical (P less than 0.002). Correlation of cigarette smoking and number of SCE could not be demonstrated (r=0.255, n=38). It was concluded that by this method there was no indication of a mutagen effect of long-term exposure to waste anaesthetic gases such as halothane and nitrous oxide.

Small children have been found to have a lower SCE/cell than adults and in recent reports females have had higher SCEs/cell than males. We here describe the relationship between SCE/cell and age and sex in 46 girls and 39 boys with an age range of 1.4-19.2 years and 2.6-18.7 years, respectively. For the calculation a transformation y = (sum SCE)1/2 + (sum SCE + 1)1/2 was used. The best fit to our material was represented by the equation y = b0 + b1 X log age. A common slope (b1) could be used for the boys and girls. This slope was significantly different from zero (P less than 0.0005). The levels of the regression lines for the two sexes were different (P = 0.0006). The girls had a 0.55-0.7 higher SCE/cell than the boys, depending on age. The following equations were found: Girls: y = 22.49 + 6.53 X log age. Boys: y = 21.11 + 6.53 X log age. By this model 43% of the variation in y could be explained. As a consequence of the result it is absolutely essential, when planning studies of children, to use age-matched groups to decrease the variability of the test system.

Sister-chromatid exchanges in peripheral lymphocytes were examined in 115 healthy women, aged 15-43 years. 63 women were on no medication at all, and 52 women used oral contraceptives. 30 metaphases from each culture were scored for SCE. In accord with previous studies, cigarette smoking increased SCE. The use of oral contraceptives had no influence on SCE on non-smoking and in cigarette-smoking women. Thus the results did not indicate any potential mutagenic effect of oral contraceptives.

When using the SCE test for evaluation of exposure in vivo to potential mutagens/carcinogens, it is necessary to consider possible confounding factors. In studies of possible mutagenic effects of pharmacological treatment the effect of concomitant administration of other agents such as sedatives may have to be considered. In order to assess whether diazepam per se influences SCE we have examined SCE in peripheral lymphocytes in 34 persons before and after oral administration of a single large dose of diazepam. 18 men and 16 women undergoing minor surgery of the hand received diazepam 0.2 mg kg-1 body weight orally on the day of operation, and venous blood samples were drawn on the day before the operation and again 2-5 h after the administration of diazepam. Both within cigarette smokers and non-smokers there was no statistically significant change of SCE following diazepam. It was concluded that there was no indication, from the SCE test, of an immediate mutagenic effect of a single large dose of diazepam and that such medication is not a confounding factor in studies by the SCE test.

Sister chromatid exchange (SCE) rates in 10 long-term lead-exposed men increased significantly with increasing zinc protoporphyrin concentration in blood. SCE rates were also related to blood lead levels, but this correlation was not statistically significant. These results were obtained before the summer vacation. Six men were examined again shortly after the vacation; both SCE rates and lead-exposure parameters had decreased significantly. An increase was seen in one worker; however, this result could be related to a serious disease for which he was undergoing treatment. Continued examinations showed a tendency of increasing SCE rates and exposure parameters, but the follow-up was too incomplete to allow a statistical analysis. Further studies of 18 newly employed workers failed to show any increase in SCE during the first 4 months of employment despite some increases in both zinc protoporphyrin and lead levels in the blood. The results obtained suggest that a genotoxic effect due to inorganic lead may occur in long-term lead-exposed workers.

The distribution of SCEs in lymphocytes was examined for 165 healthy persons (58 non-smokers and 107 smokers with cigarette consumption ranging from 1 to greater than 20 per day), and for 1 patient treated with melphalan, a cytostatic drug. The data from the healthy persons did not follow a Poisson distribution. A mixed Poisson that allowed different lambda values for the 30 cells scored from each person and postulated a gamma distribution for the lambda s within the 30 cells fitted all the data examined including those from the melphalan-treated patient. In the latter case the 7 samples taken at various times after the treatment could all be represented satisfactorily with a common parameter, c, in the gamma distribution for the lambda s, even though the mean SCEs/cell varied from 9.8 to 36.8. Because the c parameter determines the spread of lambda values within the 30 cells, this suggested that the effect of the cytostatic drug was to increase all the lambda s by a constant amount. The sum of the SCEs taken over all 30 cells in a sample is a convenient summary statistic, and the transformation y = square root s + square root s + 1 behaves as a normal variate with a constant variance within a group.

Cytogenetic methods are used increasingly for monitoring occupational exposure to potential mutagenic agents. By one such method, the sister chromatid exchange (SCE) test, previous studies of hospital operating room personnel did not indicate any mutagenic effect from exposure to waste anesthetic gases. Dentists and their assistants are exposed to much higher levels of nitrous oxide than hospital personnel, and in studies of dentists it is possible to eliminate bias from concomitant exposure to halogenated anesthetics by including unexposed persons engaged in the same professional activities as the exposed persons. SCE was examined in lymphocytes of venous blood from 38 female dentists and 74 chairside assistants, all working in the Child Dental Service, and 30 male dentists, of whom 23 worked in private practice. From studies of the model y = bo + b1 X age + b2 X cig./day + b3 X hours of exposure to nitrous oxide/week, by multiple linear regression, there was no indication of any influence of exposure to nitrous oxide on SCE. It was concluded that, from the SCE test, there is no indication of a mutagenic effect from exposure to waste nitrous oxide, and that possible health hazards from such exposure would be induced by other effects of nitrous oxide.

When planning studies by the sister chromatid exchange (SCE) test, it is necessary to calculate the size of the test groups, taking into consideration the variance of the test result and the statistical distribution of SCE frequencies. This paper deals with these problems. Recommendations are given for the preparation of slides under standardized conditions, for the subsequent counting of SCEs/cell in a random sample of 30 cells from each slide, and for the condensation of the information contained in the sample of 30 counts into a single statistic, that may be treated as a normally distributed variable. The adequacy of this transformation is shown for the data from 170 different subjects. Of these, 165 (58 nonsmokers and 107 cigarette smokers) had mean values of SCE/cell ranging from 6.5 to 13.5, while the remaining 5 subjects were on intermittent treatment with cytostatics every fourth wk, and exhibited a mean value of SCE/cell in the range 15-23. The variance associated with the recommended statistic has been decomposed into 4 variance components: variance within slides, variance between slides prepared from the same blood sample, variance within subjects, and variance between subjects. Based on a total of 680 SCE analyses in 218 persons, estimates of these variance components are given and used to calculate the necessary number of samples for the detection of a prescribed difference in SCEs/cell for selected values of Type I and Type II errors.

To explore the influence of sex on sister chromatid exchange (SCE) level, a pair of chimeric twins was examined for differences in SCE frequency between the XX and XY cells present in each individual. By this method, the influence of possible differences in environmental exposure was eliminated. SCE levels were varied by growing the cells in media containing 0, 1.3 X 10(-7), or 6.5 X 10(-7) M melphalan. XX cells showed a higher SCE count than XY cells. This difference increased with increasing SCE level and ranged from 5.4% to 7.8% (P = 0.0003) of the SCE counts. Only about 2% of the difference could be explained by the higher amount of DNA present in the XX cells than in the XY cells. In this case XX cells seemed to be more sensitive to SCE-inducing agents than XY cells.

Information on possible chromosomal damage in humans after long-term exposure to trace concentrations of waste anaesthetic gases is scarce. We examined peripheral lymphocytes in operating room personnel for both chromosome aberrations and sister chromatid exchanges (SCE). Following a standardized procedure of cultivation and staining, 30 cells from each person were scored for SCE and 100 cells from each person were examined for chromosome aberrations. A total of 45 persons were examined, representing anaesthetists (n = 15), operating room nurses assisting the surgeon (n = 10), nurses circulating in the operating room (n = 8) and healthy, unexposed controls (n = 12). The median duration of working in the operating room was 102 months, 66 months and 66 months, respectively. Time-weighted concentration levels of 2.5-4.3 p.p.m. of halothane and 25-400 p.p.m. of nitrous oxide were measured in the breathing zones of the anaesthetists during mask anaesthesia. Examination of SCE and chromosome aberrations yielded corresponding qualitative results. With both tests, no statistically significant difference was observed between the four groups of persons. It was concluded that by examination of both SCE and chromosome aberrations in peripheral lymphocytes in operating room personnel, no indication was found of a mutagenic effect of long-term exposure to trace concentrations of waste anaesthetic gases.

Cytogenetic methods are used increasingly for monitoring exposure to potential mutagens/carcinogens in the environment. By one such method, the sister chromatid exchange (SCE) test, comparison of different groups of hospital personnel has not indicated any mutagenic effect of occupational exposure to waste anesthetic gases. Since no information is available on repeated examinations of operating room personnel during a longer period of occupational exposure, the authors examined SCE in lymphocytes in a total number of 191 venous blood samples drawn from 14 previously unexposed nurses before and during up to 32 months of training as nurse-anesthetists. The initial SCE/cell ranged from 8.03 to 13.13 SCE/cell. Individual linear regressions were performed for the transformed variable, y = (sum SCE)1/2 + (sum SCE + 1)1/2, on time; and for the first 6-month period, the weighted mean of individual slopes was b0 = -0.119 +/- 0.088, not significantly different from zero. Calculated for the whole observation period, b0 = 0.030 +/- 0.014, P = 0.034 (two-tailed t test). Converted into SCE/cell, SCE would decrease 0.10 SCE/cell for each 6-month period of exposure (95% confidence limits 0.07-0.13 SCE/cell). The reason for this apparent decrease remains unknown. The results of the present study were in accord with previous studies of operating room personnel and of patients anesthetized with inhaled anesthetics. It was concluded that there is no indication, from the SCE test, of a mutagenic action due to exposure in vivo to currently used inhalation anesthetics.

We measured sister chromatid exchanges (SCEs) in lymphocytes of eight MF patients before, and 2 h, and 24 h after treatment with topical nitrogen mustard. The mean number of SCEs/cell (+/- SEM) were 8.15 (+/- 0.62), 8.34 (+0.55) and 8.26 (+/- 0.56), respectively. The 2 h and 24 h results do not differ significantly from pretreatment levels. Our results show that concentrations of nitrogen mustard used to control MF do not induce SCEs in peripheral blood lymphocytes.

Exposure to toxins in the environment and due to personal habits, e.g., tobacco smoking, may increase the rate of spontaneous sister chromatid exchange (SCE). The SCE in lymphocytes from a group of 31 patients with multiple epidermal cancer, who in the past had been exposed to various skin carcinogens, as a whole exceeded that of a control group--matched by sex, age, and smoking habits--but the difference was not statistically significant (p = 0.08). The individual SCE in these patients was also statistically independent of the nature of the carcinogenic exposure. We were unable to detect correlations between the SCE and UVC-radiation induced DNA synthesis, UVC-radiation tolerance, or rate of X-ray damage repair. This suggests that the molecular mechanisms involved in SCE induction and in repair of radiation damage are basically independent.

The acute effect of 8-methoxypsoralen (8-MOP) and 8-MOP + long wave ultraviolet light (UVA) on sister chromatid exchange (SCE) has been examined in an in vitro experiment. The SCE count was significantly increased by 8-MOP without light, but the effect was substantially greater (50%) by 8-MOP + UVA. In addition, mitoses with banded staining of the chromosomes were seen after 8-MOP and UVA. These changes were dose dependent, and they might be responsible for the reduced cell turnover in psoriasis plaque after PUVA.

42 Seventh-Day Adventists (SDAs) and 42 controls matched for sex, age and occupation had their sister-chromatid exchange (SCE) examined in peripheral blood lymphocytes. This was done to examine if the SCE frequency was lower in this group of people, who are known to have a decreased cancer risk compared to the general population. The average SCE/cell in 30 cells from each person was 5.54 +/- 0.07 (mean +/- standard error of the mean) for the SDAs and 8.00 +/- 0.15 for the controls, the difference being statistically significant (p less than 0.00001). No difference in SCE frequency was found between SDAs eating only an ovo-lacto-vegetarian diet and those eating some fish or meat. The mitotic index (MI) was significantly higher and the replication index (RI) was significantly lower in SDAs than in controls. No correlation was found between gamma (a statistical transformation of SCEs/cell) and MI or RI within the groups of SDAs or controls. In the pooled data there was a negative correlation of gamma and MI and a positive correlation of gamma and RI. Of the interpersonal variation in gamma 8% and 14% could be explained by MI and RI. The finding of a lower SCE frequency in a group of SDAs who have a low risk of cancer might indirectly indicate a relation between SCE and cancer and encourages further studies of SCE and diet.

In a previous study of the potential mutagenic action of isoflurane using the sister chromatid exchange (SCE) test in lymphocytes of surgical patients, it appeared that SCE increased in a group of 11 cigarette smokers, there being no effect in patients who were non-smokers. In the present study, 63 cigarette smokers were examined by the SCE test before and after minor orthopaedic operations undertaken under halothane or isoflurane anaesthesia, or subarachnoid analgesia. No significant changes of SCE were observed, and the risk of having missed a "true" increase of more than 0.6 SCE per cell was less than 1%. It was concluded that, in cigarette smokers, SCE in lymphocytes were unchanged after both general anaesthesia and subarachnoid analgesia, and that there was no indication from the SCE test of a mutagenic action of halothane, or isofurane, in nitrous oxide.

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.

The potential mutagenicity of isoflurane was investigated by the sister chromatid exchange (SCE) test using peripheral blood lymphocytes from patients before and after anaesthesia. Thirty patients, aged 18-59 yr (median 29.5 yr), were anaesthetized for minor orthopaedic operations with isoflurane and nitrous oxide in oxygen for 37-90 min (median 64 min). Venous blood samples were drawn before the induction of anaesthesia, immediately after completion of anaesthesia and on the following day. SCE was examined in 30 cells from each specimen. In the 30 patients, the SCE values observed immediately after completion of anaesthesia and the day after were not different statistically from the SCE values observed before the induction of anaesthesia. Separate statistical evaluation of SCE observed among the 19 non-smoking patients also revealed unchanged SCE values. In 11 cigarette-smoking patients (average 10 cigarettes per day), SCE was increased the day after operation when compared with SCE before the induction of anaesthesia (P less than 0.02). This might reflect differences in SCE formation attributable to the patients' smoking habits, but further studies of SCE in cigarette smokers are required to elucidate this. It was concluded that there was no indication, from the SCE test, of a mutagenic effect of short-term exposure to anaesthetic concentrations of isoflurane and nitrous oxide in oxygen.