[en] To determine a possible effect of low dose radiation on DNA repair processes, peripheral lymphocytes of mine workers exposed to ²²²Rn in the thermal gallery of Badgastein (Austria) and employees of the Austrian Research Centre Seibersdorf, exposed to varying doses of gamma radiation, were investigated. The capacity for unscheduled DNA synthesis (UDS) induced by in vitro UV irradiation was measured by autoradiography of isolated lymphocytes of exposed persons and unexposed controls. In all ²²²Rn-exposed mine workers a significant increase of UDS above control values could be observed. Gamma irradiation < 31 mrad conferred within three months did not show any effect; exposure > 31 mrad had a significant effect on UDS, indicating a stimulation of DNA repair capability by chronic low dose exposure. (Author)

No abstract available

[en] SCEs are considered to be a sensitive indicator for the DNA damaging effects of mutagenic and carcinogenic agents. In 1986, during the Chernobyl accident, employees of an Austrian company worked at Shlobin, 150km north of Chernobyl. At their return to Austria blood as taken and spontaneously occurring and MMC induced SCEs were studied. Spontaneously occurring SCEs in lymphocytes of 'exposed' and 'unexposed' persons were only insignificantly different when results were summarized for all test persons. A significant influence of smoking could be established. When results were correlated with the time interval between the Chernobyl accident and the date of blood sampling, the increased rate of spontaneous SCEs observed soon after the accident decreased to the normal range during the following months. Irrespective of the molecular mechanism that might be the rationale for the observed decreased induction of SCEs in lymphocytes of exposed persons, the estimation of MMC induced SCEs proved to be the most sensitive test to demonstrate population exposure to low doses of ionizing radiation. 7 refs., 1 fig., 5 tabs. (Author)

[en] Workers at a building plot in Shlobin (USSR), 150 km north of Chernobyl, were examined for the occurrence of spontaneous and mitomycin C induced SCEs in pheripheral lymphocytes. Personnel being present during and after the Chernobyl accident exhibited a decreased number of inducible SCEs compared with test-persons starting work at Shlobin by 1st of June, 1986. Since effective dose equivalents were rather low (about 2 m Sv till the end of August 1986), induced SCEs proved to be a very sensitive test for the demonstration of low dose exposure. (author) 7 refs.; 5 tabs

[en] The percentage of CD2, CD4, CD8 and NK cells of peripheral blood was investigated in persons occupationally exposed to very low doses of ionizing radiation. Investigations were carried out by monoclonal antibodies and flow-cytometry. While significant effects of age and smoking habits on the relative number of CD8 cells and CD4/CD8 ratios could be established, no influence of the very low radiation exposure on the profile of lymphocytic cells in blood was found, except a very slight effect on the relative number of total T cells (= CD2 cells). 7tabs., 2figs., 16refs. (Author)

[en] The percentage of CD2⁺, CD4⁺, CD8⁺ and HNK-1⁺ cells in peripheral blood was investigated in persons occupationally exposed to very low doses of ionizing radiation. Investigations were carried out by monoclonal antibodies and flow cytometry. While significant effects of age and smoking habits on the relative number of CD8 cells and CD4/CD8 ratios could be established, no influence of the very low radiation exposure on the profile of lymphocytic T cells in blood was found, except a very slight effect on the relative number of CD2⁺ cells. (author)

[en] The present investigations proved the differential radiosensitivity of lymphocytic subpopulations: From in vivo and in vitro irradiations it may be followed that the most sensitive subset are CD8 positive suppressor T cells. CD4/CD8 ratios are increased both in peripheral blood and after mitogen stimulation of lymphocytes of exposed persons. The decrease in B cells is pronounced only at higher radiation doses. Though the rate of DNA synthesis after mitogen stimulation was reduced in some exposed persons, that was no general phenomenon. Especially after tritium exposure, the observed lymphopenia correlated with an increased stimulation by PHA and an increased rate of DNA synthesis in some probands. Thus the present investigations indicate that - despite an inhibition of some immune parameters by radioexposure - the body is able to maintain its immunological homoeostasis. (authors)

[en] The frequencies of spontaneously occurring sister chromatid exchanges (=SCE) were determined in control persons, persons exposed to very low doses of ionizing radiation and employees of a rubber factory. Besides smoking habits and the usage of oral contraceptives, background ultraviolet (=UV) radiation seems to exert the most pronounced effect on SCE levels in control persons. (Author)

[en] Unscheduled DNA synthesis was induced by UV irradiation of spleen cells obtained from C 57 Bl mice after repeated total body irradiation of 0.05 Gy ⁶⁰Co (0.00125 Gy/mice) and determined autoradiographically. An enhancement in the ability for repair of UV induced DNA lesions was observed in cells of gamma irradiated animals. While the amount of ³H-thymidine incorporated per cell was increased, the percentage of labeled cells remained unchanged. The present results are compared with previous data on low dose radiation exposure in men. (Author)

[en] DNA excision repair constitutes the most important DNA repair system. DNA modifications may be induced even during the course of DNA replication of semiconservative DNA synthesis. All repair processes occur in almost every cell; however, juvenile cells have higher enzyme activities than completely differentiated mature cells. DNA errors or defects result in chromosome aberrations, sister chromatid exchanges, mutations, transformations and in carcinogenesis. Repair processes have a special significance for persons living in areas of elevated environmental radio-activity or for those with an occupational exposure to a certain radiation level. This is why the staffs of the Gasteiner Heilstollen and of the Seibersdorf Research Centre were examined. The paper briefly reports the results obtained. (DG)