Treatment with thrombopoietin of the hematopoietic syndrome induced by lethal irradiation.The therapeutical efficacy of thrombopoietin, an haematopoietic cytokine, has been evaluated on improvement of haematopoietic syndrome, haematopoietic recovery and survival in C57BL6J mice following total body irradiation with a 60Co source (7-10 Gy). A single administration of 0.3 μg thrombopoietin 2 h after an irradiation of 9 Gy increased the 30-day survival. The survival enhancement was related to an accelerated haematopoietic recovery for all lineages and a decrease in bacterial infections. However, when the administration was delayed to 24 h after irradiation, thrombopoietin had a lower efficiency on both survival and haematopoietic recovery. We observed that half of the thrombopoietin-treated mice died between the 2nd and the 6th month after irradiation. This long-term mortality was likely to be due to thrombosis formation. In fact, we have demonstrated that thrombopoietin activates platelets which in turn enhance thrombosis formation in irradiated mice. In order to avoid thrombosis, we administered ticlopidine, an antagonist of platelet activation, to mice before irradiation. Almost all of the 9 Gy irradiated mice which received both thrombopoietin and ticlopidine survived up to 6 months, reaching the same efficiency than a bone marrow graft. In summary, we have shown that thrombopoietin treatment enhances survival of lethally irradiated mice in relation with protection from haematopoietic syndrome. Nonetheless, an anti-platelet drug might be associated with thrombopoietin to avoid thrombosis formation which might be lethal on a long-term basis.

The consequences of a severe nuclear accident on the agricultural environment, releasing 137Cs and 90Sr-enriched aerosols, have been studied within an original lysimetric facility driven in controlled conditions. Focal point of a research scope widely open to European collaborations, this facility has hosted several scientific programmes spread over about a decade (RESSAC and PEACE, notably), the principal achievements of which are provided in the form of a synthetic overview. After a brief reminder of the historical context strongly challenged by the Chernobyl accident within which this project has evolved, the originality of the instrumental set up used for simulating a nuclear accident at a small scale is presented. The addressed scientific aspects concern the clarification of radioecological mechanisms governing the behaviour of these two radionuclides in the soil-plant system. A particular focus is placed on foliar transfers and the resulting translocation, soil in-depth migration, chemical composition of the soil interstitial water, the influence of the later on root absorption which determines the soil-to-plant transfer, all aspects being stressed over a representative spectrum of plants, soil and climates. Based on a strategy of synergy between experiments and modelling developments, the achievements obtained are used to improve the predictive radioprotection tools.

Plasma Flt3-ligand as a prognostic bio-indicator of radiation-induced bone marrow damage.Following an accidental irradiation, the choice between different therapeutic strategies mainly depends upon the estimated radiation-induced bone marrow damage. It was shown recently that the serum concentration of Flt3-ligand (FL), a cytokine mainly acting on immature haemopoietic cells, is highly elevated in either acquired or induced bone marrow aplasia. This suggested to us that FL measurement could be used as a bio-indicator of radiation-induced bone marrow damage. In order to verify this hypothesis, studies were conducted in a non human primate model as well as in humans undergoing radio and/or chemotherapy. Results showed that the increase in FL concentration on day 5 after irradiation is predictive of the evolution of the haemopoietic syndrome. Similar results were obtained in humans. Overall these results suggested that FL measurement could be used as a reliable bio-indicator of radiation-induced bone marrow damage in accidental irradiation situations.

Dosimetric control: report of French submarine forces from 1989 to 1999.We report on the Ile Longue strategic site and describe the medical and dosimetric monitoring of nuclear submarine crews. Over the past eleven years, dosimetric results of nuclear submarine crews have been gathered. We have compared these results to those of workers employed by outside enterprises and the directorate of naval constructions. During this period, neither the crew members nor the workers have been over-exposed. Considering each group, we show a more or less distinct diminution of equivalent doses.

In the present work, external annual radiation doses in human body due to presence of 226Ra, 232Th, 238U and 40K in conventional building materials and by-products from coal power plants which are being used or have the potential for use in buildings and soil in India were calculated in the human body by using GENII radiation dose calculation computer programme (Napier et al., 1988). In the calculations, human beings receive the most radiation dose from building materials from 1.0 × 10-6 Sv from 40K and the least from 2.3 × 10-11 Sv from 232Th. It has been calculated that human beings receive total 6.3 × 10$^{-7} \pm$ 2 × 10-7 Sv radiation dose exposure from soil. Data obtained are acceptable in comparison with radiation doses attributable to building materials in OECD countries.