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The mutagenic potential of white spirit, a typical mixture of primarily aliphatic hydrocarbons used as a solvent, was investigated using a battery of test systems. The ability of this compound to induce gene mutations was assayed by the Ames' test with different strains of Salmonella typhimurium; its potential clastogenicity was tested in vivo on mouse bone marrow cells; in vitro induction of sister chromatid exchanges was studied in human lymphocytes. Negative results were obtained in all test systems. It is concluded that, in spite of its evident toxicity, white spirit does not display mutagenic properties.

The use of the BudR-Giemsa technique has shown that the peripheral blood lymphocytes of Cercopithecus aethiops sabaceus display a very fast answer to PHA-stimulation. At 32 h culture time numerous mitoses are already present and at 48 h more than 30% of the dividing cells are in second mitosis. Exposure to X-irradiation results in a higher incidence of unstable aberrations than in human lymphocytes.

The ability of NiCl2 and Ni(NO3)2 to induce chromosome aberrations in vivo in male mouse has been tested by the micronucleus test and the dominant lethality test. NiCl2 as well as Ni(NO3)2 failed to produce micronuclei in polychromatic erythrocytes whereas cyclophosphamide, used as positive control, raised their incidence markedly. In contrast to the results obtained with cyclophosphamide, NiCl2 and Ni(NO3)2 did not increase the rate of post-implantation death. These compounds decreased significantly, however, the rate of pregnancy as well as the amount of pre-implantation loss. Taking into account also the data in the literature, it is concluded that nickel probably has no clastogenic properties in mammals.

Frequencies of sister-chromatid exchanges (SCE) were determined in second-division metaphases of human lymphocytes, exposed for 1 h during the G0 phase to mitomycin C (MMC) alone or to cyclophosphamide (CP) in the presence of S9 mix. The cells were then cultured for 72 h in the presence of phytohemagglutinin (PHA), concanavalin A (Con A), Wistaria floribunda (WFA) or Lens culinaris (LcH-A) extracts. Large differences in mitotic indices (MI) and cell-cycle kinetics were observed among cells subjected to the various treatments. However, in the controls as well as in the cultures submitted to a G0 mutagenic exposure, the yield of SCE was not influenced by the mitogenic agent and was, therefore, independent of the proliferation properties of the cultured lymphocyte population.

The dose-response for radiation-induced chromosome aberrations in human lymphocytes is usually fitted to the quadratic model. This assumes that the slope is essentially linear at low doses. Empirical observations of linearity at less than 200 mGy are, however, sparse. Some data have been published indicating a non-linear (threshold) response and these are reviewed. In particular one study with X-rays showed a plateau in response up to 50 mGy and with a significant dip below the control level at 4 mGy. The mechanism proposed to explain non-linearity is that low doses stimulate the enzymic repair capability of lymphocytes. Preliminary data are presented from a large experiment by six laboratories in which the low dose-response for X-rays has been re-examined. The plateau in the dose-response relationship, if it exists, does not extend to doses above approximately 10 mGy. No irradiated cells yielded aberration levels significantly below the control. Over the range 0-300 mGy the response can be fitted to a linear regression. There are, however, variations in sensitivity between cells from different donors. An unexpected finding was that some lymphocytes contained greater than 1 exchange aberrations. This may indicate a small subset of cells that are especially susceptible to the induction of aberrations by low doses.

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.

The fluorochrome-plus-Giemsa (FPG) method of Perry and Wolff was used to compare the frequencies of sister-chromatid exchanges (SCEs) induced by cyclophosphamide (CP) or mitomycin C (MMC) in human lymphocytes stimulated by phytohaemagglutinin (PHA), concanavalin A (Con A), Wistaria floribunda (WFA), or lentil lectin (LcH-A) extracts. These 4 mitogens, differing in lectin valency and/or sugar specificity, are considered as activating primarily thymus-derived (T) lymphocytes. Regardless of the mitogen used, control cultures displayed a mean yield of about 8 SCEs/cell. A contact, of 1 h, with mitomycin alone or with cyclophosphamide and enzymatic activation, resulted in a significant augmentation of SCEs dependent on the mitogen used. An approximately 2-fold, 4-fold, or 6-fold increase in SCEs was observed for the cultures stimulated by PHA, Con A, and WFA or LcH-A respectively. Furthermore, there were mitogen-dependent differences in mitotic indices and cell-cycle kinetics in human lymphocytes harvested 72 h after stimulation.

Mice kept on a normal (1.1% calcium) or low-calcium (0.03%) diet were exposed for one month to zinc chloride (0.5% Zn), lead acetate (0.5% Pb) or cadmium chloride (0.06% Cd) or to a mixture of these salts at half the above concentrations. These concentrations, given in a poor calcium diet, represent an LD 50/30 days. After the mice were killed bone-marrow cells were assayed for chromosomal aberrations, and serum calcium was determined. Chromosomal aberrations were detected in the mice maintained on a low-calcium diet and exposed to lead, zinc or a mixture of lead, zinc and cadmium. The possible mechanism for the synergistic action on genetic effects of the lack of calcium and intoxication by heavy metals are discussed, and it is recommended that routine attention be given to the state of calcium metabolism in heavy-metal intoxication.

Dose-effect curves for X-irradiation in vitro were determined on cultured blood lymphocytes of four mammalian species-cow, goat, sheep and pig-having approximately the same number of chromosome arms, the same nuclear volume and the same DNA content. The data from cow, but not those from the other species, exhibited significant inhomogeneity between the experiments. On inspection the numerical yields appear not to differ greatly in the lower dose range. Evaluation of the parameters according to the quadratic law and the power law, however, demonstrate significant differences. Pig differs from the other species regardless of which presentation is chosen. For the power law a significant difference is also found between goat and sheep.

Chromosome analysis has been performed on workers from a cadmium plant who were exposed to fumes and dust of cadmium and lead. The 35 workers were classified, according to the type and duration of exposure, into a group (cadmium service) exposed to high levels of lead and cadmium in the absence of zinc (23 people) and a group of rolling-mill workers subjected mostly to zinc but also to lower levels of lead and cadmium (12 people). A higher yield of severe chromosome anomalies (chromatid exchange, disturbance of spiralization, chromosome translocation, ring and dicentric chromosomes) together with a total lower number of structural aberrations was observed in the cadmium workers when compared with the rolling-mill group.

The toxic concentration of different heavy metal salts was determined in normal stimulated human lymphocyte cultures and was found to be 3 X 10(-3), 1 X 10(-2) and 5 X 10(-4) for zinc chloride, lead acetate and cadmium chloride respectively. Furthermore 3 subtoxic doses of each salt (2, 10 and 100 times less than the toxic dose) were added to 48- and 72-h cultures at 0 h and 24 h after initiation. Chromosome preparations were made and 100 well spread metaphases from each culture were analysed for the presence of numerical and structural aberrations. The most common aberration found for all tested metal salts was the occurrence of chromosome fragments. Dicentric chromosomes were only recorded in lymphocyte cultures treated with the lowest concentration of zinc chloride (3 X 10(-5) M) added at time 0, regardless whether the cultures were fixed after 48 or 72 h.

The ability of ruthenium red to induce chromosome aberrations in vivo in mammalian somatic cells has been evaluated by the micronucleus test on mouse bone marrow cells. Our results show that this compound, when administered i.p. at a sublethal level, can be considered as a weak clastogen.

The ability of sodium meta-arsenite (NaAsO2) to produce genetic damage in vivo has been evaluated in mice by the micronucleus test on bone marrow cells and the dominant lethality and sperm abnormality assays on male germ cells. The dose-related linear increase of micronuclei observed in somatic cells together with the negative results obtained in reproductive cells suggest that NaAsO2, under the conditions of the present experiments, displays clastogenic properties in vivo in laboratory animals, but is unable to produce heritable damage.

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.

Cynomolgus monkeys (Macaca irus) were given 0, 1.5, 6 or 15 mg of lead acetate 6 days a week for 16 months. Another group, also receiving 6 mg, was kept on a low-calcium diet. Each experimental group consisted of 2 monkeys. Chromosome analysis on cultured lymphocytes was carried out after 3, 10 and 16 months of lead treatment. The frequency of severe abnormalities (dicentrics, rings, translocations and exchanges) was significantly increased only in the group on a low calcium diet, whereas "light" abnormalities (gaps and fragments) increased with time in all groups receiving lead irrespective of the diet. The blood lead data indicate the severity of the lead poisoning.

Effects of single exposures to 125 or 250 R and those of fractionated irradiations of 2.125 R on human lymphocytes were studied upon the chromosome aberration yields in blood maintained in a refrigerator at 5 degrees C for the intervals between the irradiations. Single irradiations succeeded venepuncture; the same holds for the first dose from the fractionated one, while he second was delivered at one of the following intervals: 2.8 or 24 hours. Immediately after completion of irradiation, blood was cultured to obtain metaphase slides for cytogenetic analysis. No repair processes were observed in the hereditary cell structures of fractionatedly irradiated blood if it was maintained at 5 degrees C for the intervals between irradiations. More chromosomes fragments, interstitial deletions, aberrant cells, and breakage of cells were scored, on the opposite, in fractionatedly irradiated blood, which was stored for 24 hours. These were even with high statistically significant differences when compared with singly exposed cells to the same doses. This effect was likely to be due to blood stirage.

A treatment by cytosine arabinoside (ara-C), an inhibitor of repair, and by deoxycytidine, which reverse the inhibition activity of ara-C, has been used to study the duration of repair in X-irradiated mammalian lymphocytes. In human the repair requires at least three hours but is already completed within two hours for rabbit lymphocytes. The results appear rather surprising for pig lymphocytes because addition of ara-C to culture medium does not modify apparently the yield of aberrations.

Proliferation of lymphocytes from donors belonging to 4 age groups (2, 25, 45 and 80 years) and exposed, in vitro, to 0 or 2 Gy of X-rays was studied in cultures stimulated by 3 different mitogens. Our results show that these 3 factors (age, irradiation and mitogen) play a role in the frequencies of cells observed in first, second, third or subsequent cell division in 48 or 72 h cultures.

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.

In this study, we analyzed the cell cycle kinetics, the radiosensitivity, the repair process and the induction of sister chromatid exchanges in lymphocytes from the Werner's syndrome. When compared to a normal population, no statistical significant differences were observed for the cell cycle kinetics and the radiosensitivity. However, differences exist with respect to the repair process and lymphocytes from the Werner's syndrome are much more sensitive to the induction of SCE's.

Inherited anophthalmia was observed in the progeny of a female rat irradiated with 50 R of X-irradiation at 17 days of age. Observations on the inheritance of the condition indicated that this anophthalmia can be considered as the result of polygenic factors with incomplete penetrance.

Chromosomes in cultured lymphocytes from the following groups were analyzed: 16 workers from a smelting plant for storage batteriers in Lyon, France; 7 workers from a factory where tin dishes are made at Nerem, Belgium; and 20 controls. The choice of the workers was made on the basis of either elevated blood lead (Lyon) or elevated urinary delta-aminolevulinic acid (Nerem). An increased number of severe aberrations--rings and dicentrics--were detected in the persons from Lyon, whereas no such aberrations but an increased number of fragments were seen in those from Nerem.

Cyclophosphamide was given i.p. to male and female mice in order to study the dose--and the time--response relationship for structural chromosome aberrations induced in bone marrow cells. The results were compared to previous observations made with busulfan. After injection of cyclophosphamide the frequency of abnormal cells is maximal after 24 hours and decreases rapidly at longer intervals At comparable doses, the percentage of damaged cells is higher after treatment with busulfan and, due probably to the low solubility of the compound, reaches a maximum only after 48 hours. These results confirm that the most obvious potential drawback of this short term test is the transient nature of such anomalies.