[en] Qualitative and quantitative methods have been developed to relate phosphate/UO₂ interactions and U dissolution, in vitro, in a medium containing 0 or 10 mM phosphate concentrations at pH 5. This was performed by Energy Dispersive X ray Spectrometry (EDS) at 200 kV on entire particles and by fluorimetric measurement. The U dissolution rate was larger in a medium without phosphate than in a medium containing 10 mM phosphate. During the first day, the initial U dissolution involved 80.55% and 91.13% of the powder in media with and without phosphate respectively. From 5 to 15 d after beginning the assay, the dissolution half-times were longer than 92 d and 22 d for media with and without phosphate. EDS analyses have shown a constant P/U X ray intensity ratio for reference U₂O(PO₄)₂ for the same range of particle diameter. A gradual increase of this ratio was measured for UO₂ incubated in a 10 mM phosphate medium throughout the experiment. (author)

[en] Solid track detectors (CR-39) have been used to visualise actinide oxides distribution in rat lungs using thick samples. Animals were exposed to aerosols of ²³⁷NpO₂ or MOX obtained during the grinding step of the MIMAS process. After MOX inhalation, autoradiographs were performed on 200 μm thick cryostat lung sections after drying. One month after exposure, the autoradiographs showed a homogeneous particle distribution within lung parenchyma. By contrast, a heterogeneous distribution was observed as soon as 3 months after inhalation. After inhalation of NpO₂, lungs were embedded in paraffin and autoradiographs were performed on blocks. Particle distribution appeared heterogeneous from 450 to 800 days after inhalation exposure, and areas of high α track density could be clearly associated with some specific lung structures or lesions identified on the last stained thin section. (author)

[en] Determination of absorbed dose in biological targets after high LET α particles irradiation needs heavy calculations. A software has been developed in order to allow everyone to calculate hit probability and absorbed dose. It is particularly adapted to the study of cell cultures irradiated with electrodeposited source or α -beam accelerator. It is based first, on a random generator of α -track homogeneously distributed in 47π, second, on the evaluation of energy loss in the different media along the track and then on a statistical analysis of the results. This method is accurate and low time consuming. The target is either modeled by an ellipsoid or represented by its 3-D shape recorded using confocal microscopy. (authors)

[en] In order to compare the cell transformation induced by α- and γ-irradiation, primary cultures of tracheal epithelial cells from two rat strains, Sprague Dawley (SD) and Wistar Furth/FIsher F344 (WF/Fi) rats, were irradiated with ²⁴¹Am α-particles or ⁶⁰Co γ-rays. The relative transformation frequency (RTF) for WF/Fi primary cells was very close to the level of the spontaneous incidence and independent on the two irradiation types used. On the contrary, the RTF for the SD primary cells increased with a decrease of the LET radiation when the relative survival was higher than about 40%. Therefore, the RTF values reached 4-5 for α-particles and 10-12 for γ-rays. The RTF can be related to the intrinsic radiosensitivity of the rat epithelial cells. However, the difference in the radiation-induced RTF for SD or WF/Fi primary cells seems to be due to the development, under genetic control, of the initial lesion to the neoplastic state. (author)

[en] In order to compare the radiotoxicity of alpha- and gamma-irradiations, primary cultures of tracheal epithelial cells from two rat strains, Sprague Dawley (SD) and Wistar Furth/Fisher F344 (WF/Fi) rats, were irradiated with ²⁴¹Am α-particles or ⁶⁰Co γ-rays. The survival ratio for each of the two rat strain cells appeared to be statistically different after high-LET irradiation. WF/Fi rat cells were 1.7-times more radiosensitive than SD rat cells, whereas no difference was observed following low-LET irradiation. A comparison of the cell survival yielded RBEs of 2.8 and 4.5 for SD and WF/Fi rat cells, respectively. As previously observed, with increasing LET of particles, the cell-survival curves approximate an exponential function of the dose. On the contrary, for low-LET, the survival curves showed a marked initial shoulder. This in vitro cellular model, using epithelial cells of the upper airway, provides a suitable system to estimate the mechanism involved in radiosensitivity after high-LET irradiation. The responses to radiation-induced lethal effects within a same type of cell were dependent on the irradiation parameters, but might be modulated by the individual sensitivity under genetic or epigenetic factor controls. (author)

[en] We have developed an autoradiographic method to provide representative images of dose rate and dose distribution in the lungs after actinide oxide inhalation. This was based on the study of 30 μm thick dry sections obtained from 200 μm thick cryostat sections. In this case, solid track detector had a recording yield similar to that obtain for 5 μm thin sections and the resolution was less than 90 μm. Using this method, we visualized a heterogeneous particle distribution as soon as 3 months after exposure of rats to (U, Pu)O₂ aerosols. (authors)

[en] In the context of radiobiological and radiotoxicological studies, the development of a charged-particle beam for irradiation of biological cell culture provides an opportunity to precisely control and adjust the dose and the dose rate delivered to the cells. H⁺ and He²⁺ ions are used in an energy range of 1-16 MeV at the cell entrance. A multiple scattering method of the ions on a gold foil is used to enable homogeneous irradiation of a large sample (about 1 cm²). All intermediate foils traversed by the ions before impacting the cells are selected so as to limit the degradation of the beam characteristics, such as energy loss, and energy and angular straggling. The number of impacted ions is checked indirectly using a Faraday cup system at high beam flux (>10⁶ ions/cm²/s) or directly using a NE102 scintillator and a CR39 solid nuclear track detector. In addition, a control of the particle energy is performed using a CR39 detector. Finally, the dose delivered by the ion and the dose contribution of the secondary emission are estimated. This report describes the characteristics of the irradiation system and of the experimental procedure

No abstract available

No abstract available

[en] Measurement of alveolar macrophage survival after α irradiation to evaluate the toxicity of inhaled actinide oxides. We have studied rat alveolar macrophage survival after in vitro α irradiation with electrodeposited sources of ²³⁹Pu. Survival was estimated by the ratio of the number of adherent cells per unit of area at the end of the irradiation, versus unirradiated cells. The dose effect relationship fit to a single exponential function of fluence. A dosimetric calculation has been performed after measurement of projected areas of entire cells and cell nuclei, and estimate of their shape. The number of α tracts needed to induce 63 % alveolar macrophage lethality was about 550 α per cell about 150 α per nucleus, corresponding to a Do at about 90 Gy for entire cell or cell nucleus. Our results allow us to estimate in vivo macrophage survival after phagocytosis of actinide oxides as a function of particle size and their α specific activity. A significant lethality could be induced by actinide oxides with an aerodynamic median activity diameter higher than 1 μm and a specific α activity higher that that of ²³⁹PuO₂. (authors)