SUMMARY Ion microscopy is a microanalytical method by which one can obtain distribution images of any chemical element with isotope discrimination even at very low local concentrations, in successive slices of the specimen. These images are obtained at the price of progressive erosion of the specimen, so that the analysis may not be replayed and it is necessary to record the maximum amount of information during specimen erosion. We present an improvement of this method using a highly sensitive camera connected to a video analog‐digital converter. The images are acquired and digitized on line and may be processed by an image computer. We illustrate the technique described with an application of ion microscopy that is made possible by digital recording and processing of images. This application concerns the precise comparison of iodine isotopes and phosphorus distributions in sections of the thyroid gland of rats which were submitted to an iodine‐deficient diet followed by an injection of 129 I.
Summary— Ecotoxicological investigations were performed on two sets of biological models. The first one concerns marine pollution and was composed of invertebrates (molluscs and crustaceans) contaminated by stable or radioactive elements originating from wastes discharged into sea water. The second one concerns freshwater pollution and was composed of vertebrates (fish) contaminated by aluminium which was dissolved in rivers, as a consequence of an atmospheric pollution by acid rain. Mechanisms involved in the uptake, storage and elimination processes of these toxicants were studied, with a special emphasis on cellular and subcellular aspects of concentration sites. Two microanalytical methods were employed: secondary ion mass spectrometry (SIMS), using the ion microscope and the ion microprobe, and X‐ray spectrometry using the electron microprobe (EMP). SIMS, which enables the visualization of trace elements, was associated with an image processing system using a highly sensitive television camera connected to an image computer. Polychromatic images were obtained, allowing to establish the cellular distribution of metal contaminants. In marine organisms, the target organs and tissues of Al, rare earth elements (Tm and La) and radionuclides (U, Pu, Am) were shown to be mainly digestive gland and exoskeleton. The target organelles were shown to be spherocrystals and lysosomes where the enzymatic lysosomal coprecipitation with phosphorus was observed. Amoebocytes, which are enzymatically equipped with lysosomal phosphatase, were involved in the phagocytic clearance of metal pollutants. In trout, two processes appeared to be involved in Al accumulation. The first one corresponds to the well known insolubilisation of Al phosphate, within lysosomes of organs devoted to uptake and excretion such as gill and kidney. The second one demonstrates that organs and tissues which cannot eliminate, such as bone, heart and brain, retain Al, exhibiting a high intracellular metal concentration; moreover, large Al deposits inducing nervous tissue destruction have been observed. Data have been discussed in connection with the relationship between man and his environment.
