Quantitative Organization of GABAergic Synapses in the Molecular Layer of the Mouse Cerebellar Cortex

In the cerebellar cortex, interneurons of the molecular layer (stellate and basket cells) provide GABAergic input to Purkinje cells, as well as to each other and possibly to other interneurons. GABAergic inhibition in the molecular layer has mainly been investigated at the interneuron to Purkinje cell synapse. In this study, we used complementary subtractive strategies to quantitatively assess the ratio of GABAergic synapses on Purkinje cell dendrites versus those on interneurons. We generated a mouse model in which the GABAA receptor α1 subunit (GABAARα1) was selectively removed from Purkinje cells using the Cre/loxP system. Deletion of the α1 subunit resulted in a complete loss of GABAAR aggregates from Purkinje cells, allowing us to determine the density of GABAAR clusters in interneurons. In a complementary approach, we determined the density of GABA synapses impinging on Purkinje cells using α-dystroglycan as a specific marker of inhibitory postsynaptic sites. Combining these inverse approaches, we found that synapses received by interneurons represent approximately 40% of all GABAergic synapses in the molecular layer. Notably, this proportion was stable during postnatal development, indicating synchronized synaptogenesis. Based on the pure quantity of GABAergic synapses onto interneurons, we propose that mutual inhibition must play an important, yet largely neglected, computational role in the cerebellar cortex

A High Throughput Genetic Screen Identifies New Early Meiotic Recombination Functions in Arabidopsis thaliana

Meiotic recombination is initiated by the formation of numerous DNA double-strand breaks (DSBs) catalysed by the widely conserved Spo11 protein. In Saccharomyces cerevisiae, Spo11 requires nine other proteins for meiotic DSB formation; however, unlike Spo11, few of these are conserved across kingdoms. In order to investigate this recombination step in higher eukaryotes, we took advantage of a high-throughput meiotic mutant screen carried out in the model plant Arabidopsis thaliana. A collection of 55,000 mutant lines was screened, and spo11-like mutations, characterised by a drastic decrease in chiasma formation at metaphase I associated with an absence of synapsis at prophase, were selected. This screen led to the identification of two populations of mutants classified according to their recombination defects: mutants that repair meiotic DSBs using the sister chromatid such as Atdmc1 or mutants that are unable to make DSBs like Atspo11-1. We found that in Arabidopsis thaliana at least four proteins are necessary for driving meiotic DSB repair via the homologous chromosomes. These include the previously characterised DMC1 and the Hop1-related ASY1 proteins, but also the meiotic specific cyclin SDS as well as the Hop2 Arabidopsis homologue AHP2. Analysing the mutants defective in DSB formation, we identified the previously characterised AtSPO11-1, AtSPO11-2, and AtPRD1 as well as two new genes, AtPRD2 and AtPRD3. Our data thus increase the number of proteins necessary for DSB formation in Arabidopsis thaliana to five. Unlike SPO11 and (to a minor extent) PRD1, these two new proteins are poorly conserved among species, suggesting that the DSB formation mechanism, but not its regulation, is conserved among eukaryotes

Comportement au feu de réservoirs composites de stockage d’hydrogène sous pression

International audienceA type IV composite pressure vessel subjected to fire may burst because of the degradation of the outer layers, but when the inner pressure is less than a critical value, leak is observed instead of burst. This phenomenon is due to the heat transfer through the composite shell which leads to liner melting. In order to characterize this failure mechanisms, engulfing fire tests have been performed in the framework of the FireComp project whose objective is to understand and simulate the fire performance of hydrogen storage. An experimental set-up has been implemented to expose the cylinders to fire by the means of gas injectors. A complete instrumentation of the tank was implemented to follow the behavior of its envelope during and after the fire using thermocouples located inside its composite wall, and pressure measurement inside the vessel. A simple Finite Element model has been developed to simulate the coupled effects of mechanical damage and temperature. This approach accurately predicts the time leading to burst of the composite tank, as well as the transition between burst and leak.L’utilisation de l’hydrogène à grande échelle, et notamment pour les véhicules, nécessite de maîtriser la fiabilité de stockage de ce gaz à très haute pression. Les réservoirs de type IV constitués d’une coque composite enroulée sur un revêtement en polymère, sont aujourd’hui considérés comme une technologie mature. Afin de mieux caractériser les conditions à éviter pour observer une défaillance de ce type de stockage dans des conditions accidentelles, en particulier un incendie, le projet FireComp (projet de recherche pré-normatif de trois ans) vise à caractériser le comportement thermomécanique de ce type de stockag

Composite pressure vessels for hydrogen storage in fire conditions: Fire tests and burst simulation

International audienceA type IV composite pressure vessel subjected to fire may burst because of the degradation of the outer layers, but when the inner pressure is less than a critical value, leak is observed instead of burst. This phenomenon is due to the heat transfer through the composite shell which leads to liner melting. In order to characterize this failure mechanisms, engulfing fire tests have been performed in the framework of the FireComp project whose objective is to understand and simulate the fire performance of hydrogen storage. An experimental set-up has been implemented to expose the cylinders to fire by the means of gas injectors. A simple FE model has been developed to simulate the coupled effects of mechanical damage and of temperature. This approach is found to accurately predict the time to burst of the composite tank, as well as the transition between burst and leak

Remplacer la mère par une autre figure d'attachement conduit-il à une perturbation de l'axe corticotrope et du système ocytocinergique ?

National audienc

Scientific Outreach with Teegi, a Tangible EEG Interface to Talk about Neurotechnologies

International audienceTeegi is an anthropomorphic and tangible avatar exposing a users' brain activity in real time. It is connected to a device sensing the brain by means of electroencephalog-raphy (EEG). Teegi moves its hands and feet and closes its eyes along with the person being monitored. It also displays on its scalp the associated EEG signals, thanks to a semi-spherical display made of LEDs. Attendees can interact directly with Teegi – e.g. move its limbs – to discover by themselves the underlying brain processes. Teegi can be used for scientific outreach to introduce neurotechnologies in general and brain-computer interfaces (BCI) in particular

Polar space group and complex magnetism in Ni-11 square(HPO3)(8)(OH)(6): towards a new multiferroic material?

International audienceThe Ni-11 square(HPO3)(8)(OH)(6) phosphite was prepared using a hydrothermal method. Depending on the pressure used during the synthesis, different hierarchical superstructures were encountered, including a new original cross-shaped star. The as-obtained products were characterized by X-ray diffraction, scanning and transmission electron microscopy and magnetization. In agreement with the presence of transition metal dimers in the structure, a complex magnetic behavior is observed at low temperature. This magnetic ground-state, combined with the non-centrosymmetry of the space group, creates new opportunities for applications in this class of open framework inorganic materials. (C) 2014 Elsevier Masson SAS. All rights reserved

Polar space group and complex magnetism in Ni-11 square(HPO3)(8)(OH)(6): towards a new multiferroic material?

International audienceThe Ni-11 square(HPO3)(8)(OH)(6) phosphite was prepared using a hydrothermal method. Depending on the pressure used during the synthesis, different hierarchical superstructures were encountered, including a new original cross-shaped star. The as-obtained products were characterized by X-ray diffraction, scanning and transmission electron microscopy and magnetization. In agreement with the presence of transition metal dimers in the structure, a complex magnetic behavior is observed at low temperature. This magnetic ground-state, combined with the non-centrosymmetry of the space group, creates new opportunities for applications in this class of open framework inorganic materials. (C) 2014 Elsevier Masson SAS. All rights reserved

Anti-GnRH vaccination of stallions shedding equine arteritis virus in their semen: a field study

International audienceStallions are natural reservoirs of equine arteritis virus (EAV) in their semen, representing a potential source of outbreaks. The carrier-state is testosterone-dependent, and clears spontaneously in 4 to 40% stallions. Reduction of testosterone secretion may be obtained with the anti-GnRH vaccine Equity. In this report, 16 naturally infected stallions excreting EAV in their semen were vaccinated twice with the vaccine EquityTM and monitored irregularly under field conditions for EAV viral load in their semen and plasmatic testosterone concentration. The results are indicated in months (M) after the first vaccine injection. Testosterone concentrations decreased from 1.7 to 0.2 ng/mL (P<0.002) after 3M. The EAV viral load decreased from 3.2×109 to 1.1×106 RNA copy/mL of semen (P<0.001) after 5M. One stallion died at 7M for other reason. At M3-10, 12/15 stallions ceased to shed the virus in their semen. At M5-10, 9/15 stallions had plasmatic testosterone concentrations of ≥ 0.5 ng/mL but the 6 others showed a persistently low testosterone concentration (≤0.3 ng/mL). Of the 14 stallions that were expected to recover their reproductive activity at the time of the next breeding season (<M12), 8 were EAV negative and produced foals, and 6 were not usable (4 for reproductive deficiency and 2 for EAV positivity). All the stallions were EAV negative at M22, with one stallion being vaccinated a third time at M15. These results suggest that the anti-GnRH vaccination could help to clear EAV shedding in stallions, without a significant effect on reproductive capacity for most of them, but some present a long lasting reduced testosterone secretion

Electron Storage System Based on a Two-Way Inversion of Redox Potentials

International audienc