Analytical microscopy observations of rat enterocytes after oral administration of soluble salts of lanthanides, actinides and elements of group III-A of the periodic chart.

The behavior in the intestinal barrier of nine elements (three of the group III-A, four lanthanides and two actinides), absorbed as soluble salts, has been studied by two microanalytical methods: electron probe X-ray micro analysis (EPMA) and secondary ion mass spectrometry (SIMS). It has been shown that the three elements of group III-A, aluminium, gallium and indium; and the four lanthanides, lanthanum, cerium, europium and thulium, are selectively concentrated and precipitated as non-soluble form in enterocytes of proximal part of the intestinal tract. SIMS microscopy has shown that these elements are concentrated as a number of submicroscopic precipitates, most of them localized in the apical part of the duodenum enterocytes, where they are observed from one hour to 48 hr after a single intragastric administration. No precipitate is observed after three days. It is suggested that this mechanism of local concentration limits the diffusion of these elements through the digestive barrier, some of them being toxic and none of them having a recognized physiological role. Additionally, the precipitation in duodenal enterocytes, the life time of which is on the order of 2-3 days, allows the elements absorbed as soluble form to be eliminated as a non-soluble form in the digestive lumen along with the desquamation of the apoptotic enterocytes. The intracytoplasmic localization of the precipitates are supposed to be the lysosomes although no direct evidence could be given here due to the very small sizes of the lysosomes of enterocytes. The same results were not observed with the two studied actinides. After administration of thorium, only some very sparse microprecipitates could be observed in intestinal mucosa and, after administration of uranium, no precipitates were observed with the exception of some in the conjunctive part of the duodenal villi.

Apoptosis of rat kidney cells after 241-americium administration.

Tumors induction by americium is well known but there are no data on the biological effects of this radionucleide at subcellular level. In order to study the possible ultrastructural lesions induced by this element, a group of rats were injected with 241-Americium-citrate (9 kBq), once a week for five weeks and sacrificed 7 days after the last injection. We describe the alterations observed in the cortex kidney using cytochemical (TUNEL reaction) and histochemical (PAS staining) methods for light microscopy as well as electron microscopy techniques. Various types of lesions were detected: condensation of nuclear chromatine, fragmentation of the nuclei, swollen mitochondria, disappearance of mitochondrial crests and skrinking of the cytoplasm. This study clearly demonstrated the induction of apoptosis by americium in rat cortex kidney cells.

Early ultrastructural lesions of apoptosis induced in vivo in two varieties of tissues (thymus and kidneys) after a single whole-body-gamma irradiation of adult mice.

Three groups of adult Swiss albino female mice with an average body weight of 20 grams were exposed to a whole-body irradiation by 137-cesium gamma rays at 2, 4 and 6 Gy (1.4 Gy/min.). For all groups, samples of thymus and kidney were taken 15 min., 2, 6 and 24 hrs. after irradiation and immediately prepared for observation by electron microscopy. In the thymus the earliest significant ultrastructural lesions are observed in the nuclei from the fifteenth minute. These lesions are characterized by condensation of chromatin, convolution and fragmentation of nuclei. Alteration of mitochondria and clarification of cytoplasm in a number of thymocytes are also observed depending on the dose of radiation. These lesions increased according to the length of the post-irradiation period and after six hrs. a great number of macrophages are observed in the thymus. Most often a single macrophage, contain several apoptotic thymocytes, with a maximum number up to eight. In the kidney, serious lesions were observed, affecting both, the nucleus and the cytoplasm of the proximal convoluted tubule cells (PCT). However in these cells, the most significant and earliest lesions consist of wide cytoplasmic clarifications, severe mitochondrial damages, associated with architectural modifications of the brush border and the beta-cytomembranes. These damaged cells have been observed to occur close to normal ultrastructural cells. Less significant ultrastructural alterations are also noticed in different varieties of glomerular cells. In contrast to the serious lesions of the PCT and glomerular cells, no ultrastructural alteration were observed in the distal tubule.