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[en] The risk to human health of exposure to low-level radiation is not precisely known yet. One way of studying this is to carry out in vitro biological experiments with cell cultures and to extend the conclusions to biological models. To relate the macroscopically determinable 'low dose' to the damage of cells caused by a certain type of ionising particle is nearly impossible, therefore the number of hits and the imparted energy are the significant quantities. They can be estimated by particle transport calculations and by direct measurements. The effect of low dose was investigated in radio-adaptation experiments when mono-layers of different unsynchronised cell cultures were irradiated by neutrons produced in the filtered beam of the Budapest Research Reactor. The energy deposition was investigated by replacing the mono-layers with etched track detectors of the CR-39 type. (author)
[en] It has been reported that the aminothiol compound WR-2721 is a promising radioprotective agent and in combination with misonidazole (MISO) seems to be of therapeutic benefit. Since the radiomodification is oxygen-dependent, the actual oxygen status of cells and the surrounding media is an important factor influencing their effectiveness. Escherichia coli B/r radioresponse was studied either alone or in combination with these compounds at various oxygen concentrations ranging from anoxia to high oxygen content. WR-2721 had a protective effect under anoxic conditions and gave overall protection when oxygen was present. The maximum protection was seen at 3.2% O2 in N2 (PF 2.08). In combination with MISO the hypoxic sensitization of MISO was completely abolished by WR-2721, resulting in radioprotection under hypoxic conditions as well. Under euoxic conditions MISO was able to reduce the protective effect of WR-2721 by about 21%. According to our results MISO and WR-2721 influence each other in their radiomodifying effect in either fixation or repair of the radiation-induced damage. (orig.)
[en] One way of studying the risk to human health of low-level radiation exposure is to make biological experiments on living cell cultures. Two 210Po α-particle emitting devices, with 0.5 and 100 MBq activity, were designed and constructed to perform such experiments irradiating monolayers of cells. Estimates of dose rate at the cell surface were obtained from measurements by a PIPS α-particle spectrometer and from calculations by the SRIM 2000, Monte Carlo charged particle transport code. Particle fluence area distributions were measured by solid state nuclear track detectors. The design and dosimetric characterisation of the devices are discussed
[en] Complete text of publication follows. Objectives: Low dose alpha particles derived from radon, induce non-targeted effects such as bystander phenomenon, adaptive response or genomic instability, which may increase or decrease the risk of lung cancer. Our study was aimed to investigate whether the low radiation dose induced effects are involved in carcinogenesis induced by multiple environmental exposures. Methods: The interaction of low dose (mGy) alpha particles and the environmental PAHs (polycyclic aromatic hydrocarbons), cadmium, nickel and asbestos exposures were investigated on human lung cell lines (BEAS-2B and HFL1). Cells were treated separately and in combinations with alpha irradiation. PAH-DNA adduct levels were determined by 32P-postlabelling. DNA strand breaks were measured by Comet-assay. Micronucleus frequency, apoptosis and proliferation were also followed. Results: Alpha irradiation (10 mGy) prior to PAH's treatment, substantially de-creased the adduct level. Alpha irradiation significantly induced DNA strand breaks, whereas the PAHs at 0.2 μM did not have measurable effect by the Comet assay. In combination of alpha irradiation and the PAHs, only benzo[a]-pyrene had a modifying, ie. additive effect to alpha irradiation. Metal compounds (Cd and Ni-chloride; ) in low concentration (0,5-1μM) reduced the cytotoxicity of alpha particles, depending on the compound, incubation time, cell line treated and also low doses of radiation (mGy-s) reduced the cytotoxic effect of metals (cross adaptive response). Further increases in concentrations and/or doses caused additive cytotoxic responses. The rejoining of DNA breaks was more efficient when the cells were treated in combination with glass fibres and low dose radiation then after each single exposures. The radio-adaptive response induced by 10 mGy alpha particles was diminished by Cd (24-48 h) incubation. Cd (0,01 mM) enhanced the radiosensitivity of cells. Bystander cells found to be more sensitive to Cd, then directly irradiated ones. In the presence of Cd the re-joining of the radiation induced DNA breaks slowed down. The data on proliferation and micronuclei induction indicated that the genetic changes were detected in the progeny of irradiated and Cd-treated cells. Conclusion: It can be concluded that low dose radiation effects must be taken into consideration in estimating the health risk from combined multiple environmental exposures. This research was supported by NKFP-1B/047/2004 and GVOP 3.1.1.-2004-05-0432/3.0 grants.
[en] To mmol/l diethylmaleate (DEM) were applied during cultivation and preparation of Bacillus megaterium spores. Radiation responses of treated spores were investigated at various oxygen concentrations. DEM pretreatment did not influence the radiosensitivity of spores under anoxic conditions but an enhanced radiation response could be obtained when oxygen was present (indirect effect). Enhanced radiation response was seen when DEM was present only during irradiation under both anoxic and hypoxic conditions (direct effect). These data indicate that DEM has two different modes of action and only one of them is due to the reduction of glutathions level. (author) 9 refs.; 2 figs