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Damage from occupational or accidental exposure to ionising radiation is often assessed by monitoring chromosome aberrations in peripheral blood lymphocytes, and these procedures have, in several cases, assisted physicians in the management of irradiated persons. Thereby, circulating lymphocytes, which are in the G0 stage of the cell cycle are stimulated with a mitogenic agent, usually phytohaemagglutinin, to replicate in vitro their DNA and enter cell division, and are then observed for abnormalities. Comparison with dose-response relationships obtained in vitro allows an estimate of exposure based on scoring: Unstable aberrations by the conventional, well-established analysis of metaphases for chromosome abnormalities or for micronuclei; So-called stable aberrations by the classical G-banding (Giemsa-Stain-banding) technique or by the more recently developed fluorescent in situ hybridisation (FISH) method using fluorescent-labelled probes for centromeres and chromosomes. Three factors need to be considered in applying such biological dosimetry: (1) Radiation doses in the body are often inhomogeneous. A comparison of the distribution of the observed aberrations among cells with that expected from a normal poisson distribution can allow conclusions to be made with regard to the inhomogeneity of exposure by means of the so-called contaminated poisson distribution method; however, its application requires a sufficiently large number of aberrations, i.e. an exposure to a rather large dose at a high dose rate. (2) Exposure can occur at a low dose rate (e.g. from spread or lost radioactive sources) rendering a comparison with in vitro exposure hazardous. Dose-effect relationships of most aberrations that were scored, such as translocations, follow a square law. Repair intervening during exposure reduces the quadratic component with decreasing dose rate as exposure is spread over a longer period of time. No valid solution for this problem has yet been developed, although, in theory, both deterministic damage and aberrations might be repaired to a similar degree; a comparison of aberrations following a linear dose relationship might also help when the doses have been sufficiently large. (3) Investigations might have been possible only a certain time after the exposure. The relatively rapid disappearance of lymphocytes carrying unstable aberrations limits their use in retrospective dosimetry, years after exposure. Scoring stable aberrations, thought to persist in the circulating lymphocytes, might appear more appropriate in such situations. However, the examination of a representative number of cells by G-banding is extremely laborious, and the FISH method is not only expensive but has not yet been fully validated in different laboratories. In conclusion, biological dosimetry has serious limitations exactly for situations where the need for information is most urgent. It renders its most useful results when an individual has been exposed to a rather homogeneous high-level radiation over a short time interval, i.e. accidents at high-intensity radiation devices. On the other hand, it yielded less satisfactory information even when the most recent techniques were used for situations, where a low level, low dose rate exposure has occurred at some time in the past, for example for persons living in areas contaminated from the Chernobyl accident. Such negative experiences should be kept in mind in order to avoid futile and expensive investigations in the case of populations exposed from radioactivity and, notably, also from potentially clastogenic chemical agents.

Experiments were performed with human plasma irradiated in vitro or in vivo in order to evaluate the extent to which clastogenic factors might disturb the adaptive response to DNA-damaging factors currently studied in our laboratory. The studies were carried out with plasma isolated from whole blood given 4 Gy of X-rays in vitro and with plasma from people receiving local radiotherapy at a total dose of about 60 Gy gamma rays. Addition of irradiated plasma to culture medium did not result in a statistically significant increase in structural aberrations in chromosomes of non-irradiated normal blood., (Copyright 1998 Elsevier Science B.V.)

Observations have been performed on peripheral blood lymphocytes from a patient having ingested 200 mg thallium sulfate, in order to evaluate the ability of the compound to produce cytogenetic damage in vivo in humans. Our results demonstrate that neither the yield of structural chromosome aberrations nor sister chromatid exchanges were significantly modified. The drastic increase of binucleated cells with micronuclei indicates that thallium sulfate has in common with many metallic compounds the ability to interfere with chromosome distribution.

Few data are available concerning the genotoxic effects of antimonial salts therapy in humans. A patient suffering from visceral leishmaniasis was treated for 15 days with a cumulative dose meglumine antimoniate 42.5 g. Peripheral blood lymphocytes sampled before treatment, 7 days later, and at the end of therapy (day 15) were examined for the presence of structural chromosome aberrations, sister chromatid exchanges (SCEs), and micronuclei in binucleated cells. The treatment resulted in an increase of binucleated cells carrying micronuclei, with no changes in chromosome structural aberrations or in mean SCE frequency. On the basis of these observations and of experimental results reported in the literature, we conclude that therapy with meglumine antimoniate apparently does not represent a mutagenic or carcinogenic risk to humans.

The ability of paracetamol to induce structural chromosome aberrations in human peripheral blood lymphocytes in vivo was evaluated in volunteers who had been administered a single oral dose of 3 g paracetamol, in patients who had received 2 g of propacetamol by intravenous infusion every 6 h for at least 7 days, and in self-poisoned patients who, for suicidal reasons, had ingested more than 15 g paracetamol. In addition to the in vivo observations, the effectiveness of paracetamol to interfere with fusorial microtubule polymerisation was assayed in vitro in order to detect a possible effect of paracetamol on the distribution of chromosomes during cell division. The negative results obtained in all those assays strongly suggest that paracetamol has no mutagenic properties in human. There was, indeed, no significant difference in the percentage of abnormal cells before and after application of paracetamol in volunteers (0.2% before ingestion of 3 g paracetamol, 0.12% after 24 h, 0.04% after 72 h and 0.04% after 168 h) and in patients (0.5% of abnormal cells before treatment versus 0.44% after intravenous infusion of a total of 28 g paracetamol). Moreover, the yield of abnormal cells was not modified in self-poisoned persons (0.24%), in spite of an important decrease in the mitotic index of the PHA stimulated lymphocytes. In the in vitro assay, no inhibition of microtubule polymerisation was detected with concentrations of 2.5, 5 and 10 mM paracetamol.

The dose-effect relationship for dicentric chromosome aberrations and centric rings was studied in a female patient exposed to whole-body gamma irradiation for myeloid leukaemia. Samples were taken before and at different times during the exposure. The dose-effect relationship is on the linear-quadratic type and practically identical with those found earlier when the blood from adults and children was irradiated in vitro and only slightly above that of children irradiated in vivo.

Chromosome aberrations induced in vivo were studied in nine children 5-12 years old treated with total-body high-energy photon irradiation (pulsed exposure from a LINAC) for different types of malignant diseases. Dose-effect relationships were obtained for each child by taking blood at different times during exposure. In vitro dose-effect relationships for chromosome aberrations in children and adults were obtained by exposing blood under the same conditions as the children. Exposure in vivo and in vitro yielded similar linear-quadratic dose-effect relationships for dicentric aberrations. The response in vitro was slightly greater than in vivo, but the difference was not very large. It is concluded that the dose-effect relationship for dicentric chromosome aberrations obtained in vitro for adults can be used for biological dosimetry in irradiated children. Some of the children displayed a high number of "rogue cells" before exposure; this may be due to the malignant disease as it was not found in the healthy controls.

The dose effect relationship after homogeneous irradiation and the effect on the Poisson distribution of adding non-irradiated blood and thereby simulating non homogenous accidental exposure were studied for dicentric aberrations and micronuclei in lymphocytes exposed in vitro to 60Co gamma irradiation. The dose effect relationship for both parameters was of the linear quadratic type with the micronuclei responding slightly less to radiation than the dicentrics but a greater number of cells can easily be screened for micronuclei than for dicentrics. Except for one dose level in micronuclei, no deviations from the Poisson distribution were observed, after homogeneous tradition, but such a deviation was evident when non-irradiated blood was added to the irradiated one. With the help of the method of the "contaminated Poisson distribution" the proportion as well as the dose of the exposed blood could be approximately estimated. In order to test the suitability of the micronucleus test in vivo, both dicentrics and micronuclei were determined in patients treated for seminoma to an abdominal field. The data showed a consistent increase in both parameters without a significant difference between patients. The increase of both types of anomalies corresponded about to that expected from the size of the field exposed. The data from micronuclei appear, therefore, about as reliable for biological dosimetry as those from dicentrics for biological dosimetry after homogeneous and non-homogeneous exposure to ionizing radiations.

The study aimed to investigate whether the determination of chromosome aberrations in circulating blood lymphocytes could be useful to assess whole-body exposure from radioactive iodine released accidentally. Ten patients treated with two doses of 1850 MBq of 131I given 24 h apart for thyroid cancer were studied for chromosome aberrations (dicentrics) in blood samples taken before and at various times after exposure. The increase in the yield of aberrations caused by the exposure to iodine was small but statistically significant. Compared to published values for whole-body doses after such treatment, this increase appears to be somewhat smaller than expected from dose-effect relationships obtained for an acute exposure of lymphocytes in vitro or in vivo, a fact which could be explained by the low dose rate of the 131I exposure. Thus, in situations where a population was exposed as a result of the release of radioactive iodine, a determination of chromosome aberrations in blood lymphocytes would not appear to be very useful to determine exposure from iodine.

In a cooperative study, four laboratories evaluated the micronucleus test in irradiated and non-irradiated lymphocytes with respect to time of storage, the difference between X-ray and gamma exposure and inter-observer variance. The results were compared with parallel studies on dicentric aberrations. No significant differences between laboratories, with respect to storage time or between gamma and X-irradiation were observed for micronuclei and dicentrics using analysis of variance. However, micronuclei are not suitable for an assessment of exposure inhomogeneity because of a significant overdispersion already in controls and homogeneously irradiated samples.

A thorough cytogenetic analysis using G-banding was performed on 100 peripheral blood lymphocytes from an individual who had been accidentally exposed to radiation more than 25 years previously. More than 60% of the analysed cells were found to possess one or more stable chromosome aberrations (e.g. reciprocal translocations). Chromosomes 1 and 11 were more involved in these aberrations than would be expected from the relative chromosome lengths. No identical stable aberrations were found, suggesting that, 25 years after near-lethal exposure, haemopoietic stem cells display substantial diversity.

The present experiments were carried out on mixtures of male irradiated and female non-irradiated lymphocytes, using the Y chromosome as a marker. The results demonstrate that in vitro synchronisation of cells by a thymidine block which generally improves the preparation does not interfere with the estimate of the averaged whole body dose after homogeneous exposure or the fraction of the blood irradiated and the dose after inhomogeneous exposure.

The study aimed to investigate whether "mixed lymphocyte reactions" could interfere with the results of experiments in which irradiated blood from one person is mixed with non-irradiated blood from another. This experimental model had been designed to simulate, in vitro, non-homogeneous in vivo exposure such as could occur after accidents with ionizing radiation. The results show that the experimental models gives valid results for donors with related blood characteristics.

The situation in which inhomogeneous radiation exposure is likely to occur with accidental overexposure was simulated by studying chromosome aberrations in mixtures of male irradiated and female nonirradiated lymphocytes. The data were evaluated by means of the contaminated Poisson method. For X-ray doses from 1 to 10 Gy and ratios of irradiated to nonirradiated blood from 1:1 to 1:19, a good agreement was found between calculated and applied radiation doses and fractions exposed.

Addition of thymidine to culture medium commonly used by laboratories performing medical cytogenetics followed by a release of the block by 2-deoxycitidine increases greatly the mitotic index and the proportion of metaphases suitable for chromosome analysis. The benefit is, however, less evident when the method is applied to culture medium used in laboratories specialized in chromosome aberration dosimetry.

The yield of dicentric chromosomes has been recorded in peripheral blood lymphocytes of patients undergoing telecobalt therapy for glioblastoma. Blood samples were taken by venipuncture, prior to the first radiotherapy session and 24 h after 10, 20 and 30 Gy to the tumor volume. On the basis of the maximum likelihood method, the yield of chromosome aberrations was best fitted by a linear quadratic dose-response relationship. According to this relationship, the dose inducing ten dicentrics at the target volume is 58 Gy, a value considerably higher than those found after radiotherapy for mammary carcinoma (15 Gy) or for pelvic tumors (5.62 Gy). Our results indicate that, in the case of fractionated exposures, confined to a small volume of the body, it is not possible to estimate the total dose administered and that the method only provides an estimate of the proportion of the lymphocytes irradiated.

The consequence of exposure to the effluents of power plants that elicits the most concern is probably the induction of cancers. Due mainly to the high uncertainty of epidemiological surveys on exposure to low doses of mutagens, observations performed up to now on man have provided contradictory and inconclusive results. Since a high correlation exists between the mutagenicity of environmental agents and their carcinogenic properties, an attempt has been made to evaluate the carcinogenic potential of the different forms of energy production on the basis of the results of short term tests performed on the effluents of several power plants. Any energy source is associated with such risks and, in spite of the fact that real comparative studies were not available, coal as a source of energy presents obviously higher mutagenic potential than nuclear power. Renewable forms of energy are cleaner but are, however, not entirely devoid of health impacts.

Male mice from the C57Bl strain were given 150 mg/kg of hycanthone, an antischistosomial drug. Spermatocytes derived from the treated spermatogonia as well as the spermatocytes from the F1 male offspring sired the first three weeks after treatment were examined for the presence of chromosome rearrangements. Since no reciprocal translocation was recorded, it is concluded that treatment with hycanthone is not susceptible to produce transmissible chromosome anomalies in male mammalian germ cells.

Male rabbits (Oryctolagus cuniculus) were maintained for a 28-month period on the floor of the hut built at a site in southwestern France where the dose rate from natural radioactivity amounts to about 8 mrad/h. Male and female BALB/c mice (Mus musculus) were also placed in the hut during the summer period. The observations performed on those animals demonstrate that exposure to high natural radiation can increase the frequency of chromosome aberrations in somatic cells and indicate also the fertility in males and females is affected in an inverse manner. Model experiments with radon exposure of laboratory rabbits under controlled conditions have shown that the chromosome aberrations observed in somatic cels cella are not due to the radon exposure but essentially to gamma irradiation.

The induction of reciprocal translocations by an exposure of rat spermatids to X-irradiation has been studied by cytological examination of dividing spermatocytes of F1 sons. The incidence of F1 translocated males was found to vary from 7.89% after exposure to 125 R to 22.44% after exposure to 500 R.

Male mice of the BALB/c strain were placed on the floor of a hut built at a site of Southwest France where the dose rate of gamma radiation amounts to about 10 mrad/h. Controls were kept near the radioactive site under comparable conditions. The doses of gamma rays received during a seven month period ranged from 0.1275 rad for the controls to 45 rad and 63 rad for the exposed animals. Due, possibly, to an effect on the libido exposure to 45 rad increased the fertility whereas the animals given 63 rad produced less offspring than the controls.

Peripheral blood lymphocytes of patients undergoing radiation therapy for pelvic tumours have been examined for the presence of dicentric and centric ring chromosomes. Blood samples were taken, by venipuncture, prior to the first radiotherapy session and 24 h after radiotherapy sessions to allow the mixing of the irradiated lymphocytes in the circulating blood. The yield of dicentrics and centric rings was best fitted by a straight line which, according the maximum likelihood method, corresponds to Y = 1.77 +/- 0.0003 10(-2) D. On this basis the dose inducing ten dicentrics or rings is 5.62 Gy at the target volume and, thus, is intermediate between the doses at the target volumes displaying the same effects in patients treated for mammary carcinoma (15 Gy) or for ankylosing spondylitis (2 Gy).

The ability of saccharin to induce chromosome aberrations in mammals was tested in male mice injected i.p. with 1, 2, or 4 g saccharin per kg body weight or receiving during a 100 day period 20 g of saccharin per liter of drinking water. Two tests on somatic cells, induction of chromosomal aberrations in bone marrow cells and of micronuclei in polychromatic erythrocytes, and two tests on germ cells, the spermatocyte test on treated males and the dominant lethality test, yielded all negative results. It is concluded that the positive findings reported in the literature were probably due to the mutagenic activity of saccharin impurities.

Chromosome aberrations were scored in 59 persons from fossil-fueled plants, in 89 persons from nuclear-power plants and in 23 controls. A significant increase in acentric chromosome fragments and dicentric chromosomes compared to the control group was observed in both types of workers. Moreover, the number of abnormal cells was significantly greater in workers of conventional plants than in those of nuclear-power plants. When adjusted for loss of lymphocytes according to a half-life of 3 years, this difference was also significant for the number of dicentric chromosomes observed. A significant effect of length of exposure or of frequency of radiological examinations could be discerned only in the group of workers from conventional plants.

Human whole blood samples were exposed to different doses (1, 2, 4, 6 or 10 Gy) of gamma-radiation and mixed with different volumes of non-irradiated blood before culturing to simulate partial body irradiations. Chromosome aberrations were analysed and the frequency of dicentrics was found to be lower than expected, particularly when irradiated blood was mixed with large volumes of non-irradiated blood and after exposure to high radiation doses. For the mixtures of irradiated and unirradiated blood the deviation from the Poisson distribution depends on the respective proportions and on the doses. The results can be correlated to in vivo aberration frequencies in case of therapeutical treatments, but the yields of aberrations are generally underestimated in vitro.

Dicentrics were induced in human and rabbit lymphocytes in vitro by exposure to X-irradiation. The yields were compared with data reported in the literature. To elucidate the reasons for the different findings we have evaluated the parameters for the different models by maximum likelihood methods. From this analysis it can be concluded that the earlier claim of Bajerska and Liniecki [1] that both species have the same radiosensitivity must be discounted, and that their similarity was due to the abnormally low values these investigators observed in irradiated human lymphocytes.

Eleven male workers from the polymerization department of a vinyl chloride factory, seven people employed in the laboratory of another vinyl chloride plant, and ten controls from outside the factory environment were examined for the presence of chromosome aberrations in blood lymphocytes. Chromosome anomalies such as fragments, rings, translocations, and dicentrics were observed in most of the workers from the polymerization department. However, the medical history of these workers shows that they received frequent radiographs of the hands, feet, vertebral column, and digestive tract. It is therefore impossible to determine whether these chromosome anomalies result from vinyl chloride exposure.

The cytogenetic effects of Myleran were examined in bone-marrow cells from male mice. To study the dose--response relationship the male mice were injected with 5, 10, 20 or 40 mg of Myleran/kg. Bone-marrow samples were prepared 24 h later. The time response was investigated by examining bone-marrow samples 1, 2, 4 or 10 days after i.p. injection of 40 mg of Myleran. Most of the structural aberrations were of the chromatid type and the dose--response relationship was linear. The chromatid and chromosomal aberrations were maximal at 2 days and decreased sharply after longer intervals of time.