[en] ²¹⁰Pb measurements using ²¹⁰Po deposition technique were performed in several marine and lacustrine sediments of French Polynesia to determine sedimentation rates in lakes and lagoons. Some results in terrigeneous sediments were acceptable and permit rate measurements; on the contrary other sediments, especially coral sands provided a ²¹⁰Pb/²²⁶Ra disequilibrium (0.33 to 0.69). The occurring phenomena seem to be related to ²²²Rn scavenging and geothermal endoupwelling which induces ²²⁶Ra enhancement; this leads to the same ²¹⁰Pb/²²⁶Ra disequilibrium as in deep ocean waters as described, for instance by Thomson and Turekian (1976) in an upwelling zone on Peru coasts

No abstract available

[en] The aim of this work was to measure simultaneously and in a quantitative manner double-strand breaks (DSBs), interphase chromosome breaks and cell lethality either immediately after irradiation, or at various times thereafter (up to 24 h), in cells of three nontransformed human fibroblast cell lines of widely different intrinsic radiosensitivity. We wished to assess initial damage, repair kinetics and residual damage at the DNA and the chromosome level, and to correlate these parameters with cell killings. We employed HF19 cells, a normal fibroblast cell line, AT2 cells, a radiosensitive cell line from a patient suffering from ataxia telangiectasia (AT), and 180BR cells, a radiosensitive cell line from a patient with no clinical symptoms of AT. AT2 and 180BR cells, in addition to being radiosensitive, also display a reduced ability to repair potentially lethal damage compared to HF19 cells. The yield of DSBs, as measured by pulsed-field gel electrophoresis, is similar in all three cell lines (slopes correspond to 1.6-1.7% Gy^-1 of DNA-associated radioactivity released from the gel well into the lane). In contrast, residual DSBs measured 24 h after irradiation are almost zero for HF19 cells (0.1% confidence interval=0-1.4%), but are 12.5% (±2.3%) and 43.8% (±1.2%) of those measured immediately after irradiation in HF19, AT2 and 180BR cells, respectively. Neither the initial yield of DSBs nor that of excess interphase chromosomes breaks can explain the differences in radiosensitivity between the three cell lines; however, there is a correlation between residual DSBs, rate of DSB rejoining at 24 h, residual interphase chromosome breaks on the one hand and cell survival on the other hand. 74 refs., 6 figs., 4 tabs

[en] This study shows that it is possible to increase in vivo the efficiency of irradiation by the transfer of the wild-type gene p53 in a model of transferred human carcinoma for this gene, and emphasizes the importance of the therapeutic sequence in the observed effect. (N.C.)

[en] A review of reports dealing with fittings of the data for repair of DNA double-strand breaks (DSBs) and excess chromosome fragments (ECFs) shows that several models are used to fit the repair curves. Since DSBs and ECFs are correleated, it is worth developing a model describing both phenomena. The curve-fitting models used most extensively, the two repair half-times model for DSBs and the monoexponential plus residual model for ECFs, appear to be too inflexible to describe the repair curves for both DSBs and ECFs. We have therefore developed a new concept based on a variable repair half-time. According to this concept, the repair curve is continuously bending and dependent on time and probably reflects a continuous spectrum of damage repairability. The fits of the curves for DSB repair to the variable repair half-time and the variable repair half-time plus residual models were compared to those obtained with the two half-times plus residual and two half-times models. Similarly, the fits of the curves for ECF repair to the variable repair half-time and variable half-time plus residual models were compared to that obtained with the monoexponential plus residual model. The quality of fit and the dependence of adjustable parameters on the portion of the curve fitted were used as comparison criteria. We found that: (a) It is useful to postulate the existence of a residual term for unrepairable lesions, regardless of the model adopted. (b) With the two cell lines tested (a normal and a hypersensitive one), data for both DSBs and ECTs are best fitted to the variable repair half-time plus residual model, whatever the repair time range. 47 refs., 3 figs., 3 tabs

[en] The object of this preliminary work is to measure the gamma radioactivity of some marine species and sediments of the French Mediterranean coast line between Banyuls and Menton. The marine species measured are: mussels, sea urchins and ten species of seaweed, namely: Ulva sp., Codium sp., Zoostera marina, Corallina elongata, Stypocaulon scoparium, Cymodocee nodosa, Pterocladia pinnata, Asparagopsis armata, Cystoseira sp., Sphaerococcus coronopifolius. The sampling places are spread over twenty four stations, eight of which are maritime and six representative of coastal lakes west of the Rhone. This aggregate study allowed us to highlight certain particular points and to make a choice between the indicators for a subsequent study in the most interesting areas

[en] Some phases of the cycles of certain radioelements the period of which is long enough to interfere with man, are described. The behaviour of radionuclides is closely linked with the concomitant presence of isotopes or stable analogues in secular equilibrium in the medium; sources (nuclear explosions, cosmic radiations, nuclear reactors, ...) and behaviour of carbon-14, technetium-99, iodine-129, neptunium-237 and plutonium-239 are briefly described

[en] Enrichment in caesium-137, ruthenium-106, manganese-54 and cobalt-60, could be measured in surface-microlayer samples which had been collected in the North-Western Mediteranean Sea, off the Rhone river, during EURHOGLI oceangraphic cruise. In the underlying waters these elements were only present at trace-levels. Such a concentration appears to be linked to accumulation processes of the particulate fraction and not only to the dynamic of continental-water inflows

[en] In 1987, ²¹⁰Pb and ²¹⁰Po measurements were taken on Tridacna maxima at different locations in Polynesia under a program of biological monitoring of the environment that France has undertaken since 1963. A comparison is given of results since 1966 of the percentage of Cobalt-60 in the flesh of the mollusc in two places : Tahiti and Tureia atoll situated 80 km north of Mururoa

No abstract available