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The aim of our study was to define the biokinetics of 90Sr after chronic contamination by ingestion using a juvenile and adult murine model. Animals ingested 90Sr by drinking water containing 20 kBq l -1 of 90Sr. For the juvenile model, parents received 90Sr before mating and their offspring were killed between birth and 20 weeks of ingestion. For the adult model, 90Sr ingestion started at 9 weeks of age and they were killed after different ingestion periods up to 20 weeks. The body weight, food and water consumption of the animals were monitored on a weekly basis. Before killing and sampling of organs, animals were put in metabolic cages. 90Sr in organs and excreta was determined by liquid scintillation \textgreekb counting. Highest 90Sr contents were found in bones and were generally higher in females than in males, and 90Sr retention varied according to the skeletal sites. An accumulation of 90Sr in the bones was observed over time for both models, with a plateau level at adult age for the juvenile model. The highest rate of 90Sr accumulation in bones was observed in early life of offspring, i.e. before the age of 6 weeks. With the exception of the digestive tract, 90Sr was below the detection limit in all other organs sampled. Overall, our results confirm that 90Sr mainly accumulates in bones. Furthermore, our results indicate that there are gender- and age-dependent differences in the distribution of 90Sr after low-dose chronic ingestion in the mouse model. These results provide the basis for future studies on possible non-cancerous effects during chronic, long-term exposure to 90Sr through ingestion in a mouse model, especially on the immune and hematopoietic systems. © 2011 Springer-Verlag.

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The aim of this work was to compare the distribution of 137Cs in organisms after chronic ingestion following different schedules. Rats were contaminated through drinking water containing 6,500 Bq L-1 of 137Cs, starting either at birth, at weaning, or upon reaching adult age (13 wk). Animals were then sacrificed after different durations of ingestion. 137Cs content of organs and excreta were determined by γ counting. A slight decrease in Cs elimination through urine was observed according to the age of animals. All organs tested showed similar 137Cs content, with the exception of striated muscles and the thyroid at certain ages, which showed the highest accumulation of Cs. The lowest 137Cs concentration was found in the blood, which acts as a transfer compartment after absorption in the intestine. Substructures of the central nervous system showed a homogeneous level of 137Cs accumulation, except for the olfactive bulbs. In these structures, an increased concentration of 137Cs was observed, suggesting a possible direct route of intake through the nasal epithelium. Overall, these results are in agreement with current models for the biokinetics of 137Cs. However, these results also suggest that the thyroid should be taken into account in future models of 137Cs biokinetics. Copyright © 2010 Health Physics Society.

The aim of this work was to define the possible occurrence of hematological changes during the course of a chronic ingestion of 137Cs. A mouse model was used, with ingestion through drinking water with a cesium concentration of 20 kBq l -1. Ingestion started in parent animals before mating, and 137Cs intake and its effect on the hematopoietic system was studied in offspring at various ages between birth and 20 weeks. 137Cs content was measured in various organs, indicating that 137Cs was distributed throughout the organism including lymphohematopoietic organs, i.e., femurs, spleen and thymus. However, we did not observe any effect on the hematopoietic system, whatever the parameter used. In fact, blood cell counts, mononuclear cell counts and progenitor frequency in bone marrow and spleen, and Flt3-ligand, Erythropoietin, G-CSF and SDF-1 concentration in plasma remained unchanged when compared to control animals. Moreover, phenotypic analysis did not show any change in the proportions of bone marrow cell populations. These results indicate that, although 137Cs was found in all organs implicated in the hematopoietic system, this did not induce any changes in bone marrow function. © Springer-Verlag 2010.

Twenty years after the Chernobyl accident, 137-Caesium (137-Cs) is the main residual radionuclide found in contaminated areas. 137-Cs progressively integrated food chains until man, inducing a chronic contamination of large populations through daily ingestion of small quantities of 137-Cs. Some studies indicated an accumulation of 137-Cs in the thyroid, the heart and muscles. It was then suggested that 137-Cs contamination could lead to some pathologies observed within populations living onto contaminated areas. In order to determine the possible influence of Cs137 onto the immune system, we developed a mouse model of chronic contamination through drinking water with a concentration of 20 KBq.l-1 of 137-Cs. This corresponds to a daily ingestion of 6 KBq.day-1.kg of body weight, ten times higher than the highest measurements made after the Chernobyl accident. Parent animals were contaminated before mating and during gestation. After weaning, contamination of offspring was continued through drinking water. Gamma counts indicated that 137-Cs was found in all tissue tested at a concentration between 2 and 20 Bq/g of tissue. However, a progressive accumulation of 137-Cs was observed in muscles and kidney, and to a lesser extend in the heart and in femurs, mainly until 9 weeks of age. The immune system was evaluated by several means, including phenotypic and functional analyses. Phenotypic analysis of blood cells did not showed significant changes in both CD4+ and CD8+ T lymphocytes, in CD4+CD25+ Tregs, or in B220+ B lymphocytes between control and 137-Cs contaminated animals. Intrathymic differentiation was evaluated by phenotypic analysis of thymocyte subpopulation and by T cell excision circle (Trec) detection. However, no significant changes in intra-thymic differentiation were observed whatever the age of animals. Three functional tests were also used to evaluate the immune system, response of splenocytes to a mitogenic stimulation, response of splenocytes in a mixed lymphocyte reaction test, and specific response to a vaccination against tetanus toxoid. However, no significant changes were observed in 137-Cs contaminated animals as compared to control animals, even in 35 weeks-old animals. Overall, these results suggest that 137-Cs may accumulate over time in some organs such as the heart, the kidney, the femurs and muscles. However, our results also demonstrate that 137-Cs ingestion does not induce a significant modification of the immune system. This suggests that the pathologies associated with the immune system observed within populations living onto contaminated territories might not be attributed solely to the 137-Cs internal contamination.

Since the Chernobyl accident, the most significant problem for the population living in the contaminated areas is chronic exposure by ingestion of radionuclides, notably 137Cs, a radioactive isotope of cesium. It can be found in the whole body, including the central nervous system. The present study aimed to assess the effect of 137Cs on the central nervous system and notably on open-field activity and the electroencephalographic pattern. Rats were exposed up to 90 days to drinking water contaminated with 137Cs at a dosage of 400 Bq kg-1, which is similar to that ingested by the population living in contaminated territories. At this level of exposure, no significant effect was observed on open-field activity. On the other hand, at 30 days exposure, 137Cs decreased the number of episodes of wakefulness and slow wave sleep and increased the mean duration of these stages. At 90 days exposure, the power of 0.5-4 Hz band of 137Cs-exposed rats was increased in comparison with controls. These electrophysiological changes may be due to a regional 137Cs accumulation in the brain stem. In conclusion, the neurocognitive effects of 137Cs need further evaluation and central disorders of population living in contaminated territories must be considered. © 2006 Elsevier Ireland Ltd. All rights reserved.