Contribution à l'étude de la biosynthèse et des effets pro-remyelinisants de la progesterone dans le système nerveux central

PARIS-BIUP (751062107) / SudocPARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Contribution à l'étude de la biosynthèse et des effets pro-remyelinisants de la progesterone dans le système nerveux central

PARIS-BIUP (751062107) / SudocPARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Effect of uranium on multipotency of neural stem cells in a primary neurosphere culture model

International audienceUranium exposure situations are diverse and originate from its natural presence in the environment, and from its use in specific professional activities in relation with the nuclear industry (extraction, nuclear fuel cycles, and dismantling operations). Uranium internal contamination can occur via ingestion of contaminated food and drinking water or via inhalation of particulate aerosols containing uranium dust. This latest situation is the main cause of contamination in nuclear occupational activities. These contaminations raise concern in terms of potential consequences on human health. They appear to have negative impact on the brain as experimental studies have shown that uranium exposure via ingestion or inhalation can lead to cognitive impairments in rats. Neurogenesis disruption has been proposed to underlie these effects. To address this question, we used in vitro neurosphere primary cultures from rat embryo’s telencephalon at embryonic day 13. We studied uranium impact on multipotency of neural stem cell within a range of concentrations (10, 50, 100 μM) versus control over 7 days of contamination. Our results show a significant effect on cell survival via a decrease of the absolute number of all cell types: neurons, astrocytes and mature oligodendrocytes at 50 and 100 μM. Among cells surviving after 7 days of contamination, analysis of apoptotic gene expression tend to suggest an adaptive response via Bax/Bcl2 balance in favour of cell survival at 100 μM condition, that will need further investigations. In this condition (100 μM), neurons exhibit an aborted morphology with a reduction of the axon and dendrite length correlated with a significant decrease of gene expression GAP43 known to be involved in dendritic arborization development. Regarding gliogenesis, uranium seems to have a direct action on the maintenance of a population of glial progenitors Olig2 positive, linked with a significant increase of NeuroG3 gene expression at 100 μM. All together, these results suggest that uranium exerts a specific action on late cell maturation phases rather than on early determination stages.Keywords: neurotoxicity, stem cell, multipotency, metals, uraniu

Effect of uranium on multipotency of neural stem cells in a primary neurosphere culture model

International audienceUranium exposure situations are diverse and originate from its natural presence in the environment, and from its use in specific professional activities in relation with the nuclear industry (extraction, nuclear fuel cycles, and dismantling operations). Uranium internal contamination can occur via ingestion of contaminated food and drinking water or via inhalation of particulate aerosols containing uranium dust. This latest situation is the main cause of contamination in nuclear occupational activities. These contaminations raise concern in terms of potential consequences on human health. They appear to have negative impact on the brain as experimental studies have shown that uranium exposure via ingestion or inhalation can lead to cognitive impairments in rats. Neurogenesis disruption has been proposed to underlie these effects. To address this question, we used in vitro neurosphere primary cultures from rat embryo’s telencephalon at embryonic day 13. We studied uranium impact on multipotency of neural stem cell within a range of concentrations (10, 50, 100 μM) versus control over 7 days of contamination. Our results show a significant effect on cell survival via a decrease of the absolute number of all cell types: neurons, astrocytes and mature oligodendrocytes at 50 and 100 μM. Among cells surviving after 7 days of contamination, analysis of apoptotic gene expression tend to suggest an adaptive response via Bax/Bcl2 balance in favour of cell survival at 100 μM condition, that will need further investigations. In this condition (100 μM), neurons exhibit an aborted morphology with a reduction of the axon and dendrite length correlated with a significant decrease of gene expression GAP43 known to be involved in dendritic arborization development. Regarding gliogenesis, uranium seems to have a direct action on the maintenance of a population of glial progenitors Olig2 positive, linked with a significant increase of NeuroG3 gene expression at 100 μM. All together, these results suggest that uranium exerts a specific action on late cell maturation phases rather than on early determination stages.Keywords: neurotoxicity, stem cell, multipotency, metals, uraniu

Design of an Inhalation Chamber and Metrology Assessment to Study Tungsten Aerosol Neurotoxic Effects

International audienceTo evaluate the neurotoxic effects from exposure to airborne tungsten, we developed a method of generating mass concentrations of this element between 5 and 10 mg m-3, the time weighted average occupational exposure limits. We then conducted measurements of the aerosol—a challenge due to the high particle density—that enabled us to calculate the deposition in the upper airway and lungs.First, we fed a mixture of coarse tungsten bead powder and aerosolizable tungsten powder, which had been combined in specific mass proportions, to an RBG 1000 (Palas®) equipped with a cyclone at the outlet that filtered out the coarse particles. Then, we simultaneously measured the resultant aerosol, which was generated in an inhalation chamber, using three pairs of instruments—a Dekati® Low Pressure Impactor (DLPI; 30 L min-1) and a gravimetric filter holder, a DLPI and a TSI® Aerodynamic Particle Sizer (APS; Model 3321), a TSI Engine Exhaust Particle Sizer (EEPS; Model 3090) and an APS—and symmetrical sampling lines. The mass concentrations obtained with the DLPI and the filter holder were extremely consistent with each other, and the mass median aerodynamic diameters based on the DLPI and the APS data (with the Stokes correction applied to the latter) were also fairly close (1.77 and 1.89 ^m, respectively). Additionally, the count median diameter determined from the electrical mobility measured by the EEPS equaled 0.17 ^m, which falls beyond both the intended range of the instrument and the range of previously studied aerodynamic sizes.Overall, the results from the DLPI, the APS, and the EEPS showed very good agreement. Computational fluid dynamics (CFD) simulations of the airflows and aerosol dispersion in the inhalation chamber verified that the test aerosol was homogeneous and representative

Brain accumulation of inhaled uranium in the rat depends on aerosol concentration, exposure repetitions, particle size and solubility

International audienceA rostro-caudal gradient of uranium (U) in the brain has been suggested after its inhalation. To study thefactors influencing this mapping, we first used 30-min acute inhalation at 56 mg/m3 of the relatively soluble form UO4 in the rat. These exposure parameterswere then used as a reference in comparison with the other experimental conditions. Other groups received acute inhalation at different concentrations, repeated low dose inhalation of UO4 (10 exposures) or acute low dose inhalation of the insoluble form UO2. At 24 hafter the last exposure, all rats showed a brain U accumulation with a rostro-caudal gradient as compared to controls. However, the total concentration to the brain was greater after repeated exposure than acute exposure, demonstrating an accumulative effect. In comparison with the low dose soluble U exposure, a higher accumulation in the front of the brain was observed after exposure to higher dose, to insoluble particles and following repetition of exposures, thus demonstrating a dose effect and influences of solubility and repetition of exposures. In the last part, exposure to ultrafine U particles made it possible to show 24 h after exposure the presence of U in the brain according to a rostro-caudal gradient. Finally, the time-course after exposure to micronic or nanometric U particles has revealed greater residence times for nanoparticles

Effets de l’inhalation de particules de tungstène sur le cerveau de rat : métrologie et étude pilote

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Cell proliferation and cell death are disturbed during prenatal and postnatal brain development after uranium exposure

International audienceThe developing brain is more susceptible to neurotoxic compounds than adult brain. It is also well known that disturbances during brain development cause neurological disorders in adulthood. The brain is known to be a target organ of uranium (U) exposure and previous studies have noted that internal U contamination of adult rats induces behavioral disorders as well as affects neurochemistry and neurophysiological properties. In this study, we investigated whether depleted uranium (DU) exposure affects neurogenesis during prenatal and postnatal brain development. We examined the structural morphology of the brain, cell death and finally cell proliferation in animals exposed to DU during gestation and lactation compared to control animals. Our results showed that DU decreases cell death in the cortical neuroepithelium of gestational day (GD) 13 embryos exposed at 40. mg/L and 120. mg/L and of GD18 fetuses exposed at 120. mg/L without modification of the number of apoptotic cells. Cell proliferation analysis showed an increase of BrdU labeling in the dentate neuroepithelium of fetuses from GD18 at 120. mg/L. Postnatally, cell death is increased in the dentate gyrus of postnatal day (PND) 0 and PND5 exposed pups at 120. mg/L and is associated with an increase of apoptotic cell number only at PND5. Finally, a decrease in dividing cells is observed in the dentate gyrus of PND21 rats developmentally exposed to 120. mg/L DU, but not at PND0 and PND5. These results show that DU exposure during brain development causes opposite effects on cell proliferation and cell death processes between prenatal and postnatal development mainly at the highest dose. Although these modifications do not have a major impact in brain morphology, they could affect the next steps of neurogenesis and thus might disrupt the fine organization of the neuronal network

Renal toxicity and biokinetics models after repeated uranium instillation

International audienceUranium kidney toxicity is well documented after acute uranium intake with a threshold of around 1-3 µg/g of kidney. Results of chronic exposure studies are controversial even after long-term exposure via drinking water during 9 months reaching 6 µg/g of kidney. During nuclear fuel processing, workers can potentially be exposed to repeated inhalations of uranium compounds.A biokinetic model after uranium intake has been recently updated by the International Commission on Radiological Protection to include recent data. However most of experimental data consider either acute inhalation, chronic ingestion via drinking water, or wound contamination (shrapnels). To evaluate uranium kidney concentration after protracted inhalations, assumptions of repeated acute intake are made, but no experimental data are available to support them. The objectives of this work is therefore to verify 1) if the uranium biokinetic model developed from the data obtained for acute inhalation is consistent with the data obtained for repeated contaminations of animals; 2) if nephrotoxicity modifies uranium retention and excretion; 3) if nephrotoxicity threshold can be predicted by the models.Mice (C57BL6/J) were exposed to different uranyl nitrate hexahydrate concentrations (0.03-3 mg/kg/day) via intranasal instillation four times a week during two weeks. Concentrations of uranium in urine and in tissues were measured at several time points during exposure and up to 42 days post exposure. In parallel, kidney toxicity was evaluated in urine using Clusterin and Kim-1 kidney biomarkers and confirmed by in situ kidney mRNA levels of early and late nephrotoxicity markers.For the lower uranium concentrations, the experimental retention in kidney was well predicted by the standard rat specific biokinetic model when accounting for the exposure profile. For every concentration tested, the amount of activity retained in the kidney reflected the two consecutive weeks of instillation. Uranium biokinetics was modified for higher doses, probably due to tissue alteration and organ dysfunction not considered in biokinetic models. A clear nephrotoxicity and renal impairment was detected for the highest concentration of 3 mg/kg/day and moderate nephrotoxicity was observed at 1 mg/kg/day.Our results suggest that specified biokinetic models should be developed to take into account the alteration of excretion and retention due to organ toxicity. The threshold of uranium nephrotoxicity should be adapted according to the contamination mode and its duration (acute, chronic, and repeated)