Codes multiéchelles et sûreté nucléaire : cas du RIA

International audienc

Methamphetamine decreases dentate gyrus stem cell self-renewal and shifts the differentiation towards neuronal fate

Methamphetamine (METH) is a highly addictive psychostimulant drug of abuse that negatively interferes with neurogenesis. In fact, we have previously shown that METH triggers stem/progenitor cell death and decreases neuronal differentiation in the dentate gyrus (DG). Still, little is known regarding its effect on DG stem cell properties. Herein, we investigate the impact of METH on mice DG stem/progenitor cell self-renewal functions. METH (10 nM) decreased DG stem cell self-renewal, while 1 nM delayed cell cycle in the G0/G1-to-S phase transition and increased the number of quiescent cells (G0 phase), which correlated with a decrease in cyclin E, pEGFR and pERK1/2 protein levels. Importantly, both drug concentrations (1 or 10 nM) did not induce cell death. In accordance with the impairment of self-renewal capacity, METH (10 nM) decreased Sox2+/Sox2+ while increased Sox2−/Sox2− pairs of daughter cells. This effect relied on N-methyl-d-aspartate (NMDA) signaling, which was prevented by the NMDA receptor antagonist, MK-801 (10 μM). Moreover, METH (10 nM) increased doublecortin (DCX) protein levels consistent with neuronal differentiation. In conclusion, METH alters DG stem cell properties by delaying cell cycle and decreasing self-renewal capacities, mechanisms that may contribute to DG neurogenesis impairment followed by cognitive deficits verified in METH consumers

Spontaneous Pneumomediastinum: A Rare Cause of Chest Pain

Spontaneous pneumomediastinum is a rare medical condition characterized by the presence of free air in the mediastinum, not preceded by trauma, surgery, or another medical procedure. It predominantly affects young adult males and usually has a benign course, and in most cases, it is not possible to identify the precipitating factor. There are some conditions that predispose to its occurrence, namely those that lead to an increase in intrapleural pressure, such as coughing, vomiting, or vigorous exercise. We report a case of a 21-year-old male who presented with acute-onset shortness of breath after an episode of coughing and was found to have mediastinal and subcutaneous emphysema. Clinical, laboratory, and radiological studies did not demonstrate any predisposing factor, and the case was classified as spontaneous pneumomediastinuminfo:eu-repo/semantics/publishedVersio

Modulation of subventricular zone oligodendrogenesis: a role for hemopressin?

Neural stem cells (NSCs) from the subventricular zone (SVZ) have been indicated as a source of new oligodendrocytes to use in regenerative medicine for myelin pathologies. Indeed, NSCs are multipotent cells that can self-renew and differentiate into all neural cell types of the central nervous system. In normal conditions, SVZ cells are poorly oligodendrogenic, nevertheless their oligodendrogenic potential is boosted following demyelination. Importantly, progressive restriction into the oligodendrocyte fate is specified by extrinsic and intrinsic factors, endocannabinoids being one of these factors. Although a role for endocannabinoids in oligodendrogenesis has already been foreseen, selective agonists and antagonists of cannabinoids receptors produce severe adverse side effects. Herein, we show that hemopressin (Hp),a modulator of CB1 receptors, increased oligodendroglial differentiation in SVZ neural stem/progenitor cell cultures derived from neonatal mice. The original results presented in this work suggest that Hp and derivates may be of potential interest for the development of future strategies to treat demyelinating diseases

Strain evolution during hydride precipitation in Zircaloy-4 observed with synchrotron X-ray diffraction

Synchrotron X-ray diffraction was used to evaluate strain evolution observed in Zircaloy-4 undergoing hydride precipitation during a range of thermal operations. During continuous heating, a change in the constraining effect of the matrix was observed at a temperature of 280 °C, thought to be the result of matrix dilatation from interstitial hydrogen. A deconvolution of the thermal, chemical and mechanical sources of strain during quench and dwell operations identified a non-negligible mechanical effect in the matrix. During these dwells, slow strain rate relaxation of elastic strains was seen in the matrix and hydride, suggesting that time dependent relaxation of misfit stresses may be possible at reactor relevant temperatures. Notable anisotropy was observed between the rolling and transverse directions, identified as being the likely product of a similar anisotropy in the relaxation of the hydride misfit between the α and α matrix directions, owing to the differing coherency of these two interfaces

In situ hydrogen loading on zirconium powder

For the first time, various hydride phases in a zirconium-hydrogen system have been prepared in a high-energy synchrotron X-ray radiation beamline and their transformation behaviour has been studied in situ. First, the formation and dissolution of hydrides in commercially pure zirconium powder were monitored in real time during hydrogenation and dehydrogenation, then whole pattern crystal structure analysis such as Rietveld and Pawley refinements were performed. All commonly reported low-pressure phases presented in the Zr-H phase diagram are obtained from a single experimental arrangement