Conservation and management in the French sub-Antarctic islands and surrounding seas

Of the French islands in the Southern Indian Ocean, Archipel Crozet and Iles Kerguelen are considered sub-Antarctic, and Ile Amsterdam and Ile Saint-Paul temperate. All have endemic species amongst their biota. The Terres Australes et Antarctiques Franyaises (TAAF) is responsible for sovereignty of these islands, the French Polar Institute (IPEV) is the central agency for research, and the Committee for the Polar Environment (CEP) provides advice on environmental protection and management issues. In 2006 all of the islands gained the status of Nature Reserve, and a management plan is expected to be in place within three years, providing greater protection for the environment and biota

Food uptake, lipid transport and vitellogenesis in the sea anemone Nematostella vectensis

Balancing energy input and output is crucial for the survival of all organisms, and involves the coordination of many physiological processes such as food uptake, nutrient storage, reproduction and growth. The uptake of food particles through endocytic mechanisms (e.g. phagocytosis, receptor-mediated endocytosis) is broadly observed and likely the ancestral mode of feeding in metazoans. However, only little is known about the biology and evolution of endocytic cell types involved in animal nutrition. Similarly, the dynamics and molecular pathways underlying the transport of nutrients is poorly investigated in animals without a circulatory system. The lack of available studies, especially in non-bilaterian animals (e.g. cnidarians, sponges) leaves a number of key questions unresolved: how did endocytic cell types evolve? What are the ancestral modalities of nutrient transport in animals? In my thesis, I address these questions by investigating the cells and molecular pathways underlying food uptake and, as a specific example of lipid transport, vitellogenesis, in the sea anemone Nematostella vectensis. By characterizing the path of food particles and dietary lipids from their ingestion to their incorporation into yolk, I aim to fill in gaps in our understanding of nutrient uptake and transport in non-bilaterians and thereby shed light on the evolution of these processes in animals. In Nematostella, nutrient acquisition starts with the extracellular digestion of prey in the gastric cavity through secreted digestive enzymes. Using single-cell RNA sequencing (scRNA-seq), I characterized the cellular composition of the gastrodermal folds lining the gastric cavity (mesenteries) and found a high diversity of specialized gland cells expressing specific enzymatic repertoires. Extra-cellular digestion is followed by endocytosis and subsequent intracellular digestion of food particles. By using particle uptake assays, I revealed that phagocytosis and receptor-mediated endocytosis predominantly occur in specific regions of the mesenteries in Nematostella, highlighting a surprising regionalization of the anthozoan gastrodermis. These regions colocalize with the cellular expression of Nematostella orthologs of bilaterian genes typically involved in endocytosis (e.g. mannose receptor, clathrin). This strongly supports the digestive function of these cells and indicates a conserved nature of endocytic molecular pathways between cnidarians and bilaterians. These results were further validated by scRNA-seq, which revealed three distinct populations of trophic endocytes co-localizing within the endocytic region of the mesentery. In bilaterians, dietary nutrients are most often transported towards other tissues via the circulatory system in order to be stored or to support the metabolism of peripheral tissues. Cnidarians lack a circulatory system, and the gastro-vascular cavity is thought to distribute nutrients throughout the body. The extracellular matrix (mesoglea) was previously proposed to participate in nutrient transport, but its role in this process has so far been unclear. In the present work, I describe for the first time the dynamic trans-epithelial transport of lipids from the gastric cavity into maturing oocytes located in the mesoglea in a cnidarian. Consistent with their function in shuttling lipids between the gastric cavity and the oocyte, somatic cells of the gonad epithelium also produce the glycolipoprotein Vitellogenin, a conserved yolk precursor. Gene expression data shows that the uptake of Vitellogenin into growing oocytes likely occurs through receptor-mediated endocytosis using orthologs of the vldlr/apolipophorin receptor gene family. This supports the hypothesis that a specific Vitellogenin ligand/receptor pair is highly conserved in vitellogenesis between cnidarians and bilaterians. Finally, I characterized the expression and protein localization of ApoB, a Nematostella ortholog of the bilaterian systemic lipid transport proteins Apolipoprotein-B/Apolipophorins. ApoB protein was not detected in growing oocytes in Nematostella but surprisingly localized in spermaries, suggesting a role during spermatogenesis. Overall, these results demonstrate the mesogleal transport of lipids potentially using conserved lipoprotein-lipoprotein receptor pairs in the absence of a circulatory system, and raise the possibility of a rudimentary systemic lipid transport system in Nematostella. Altogether, my thesis revealed that nutrient uptake in Nematostella involves a remarkable diversity of specialized cell types that define functional domains in the mesenteries. The molecular machinery for food uptake, intracellular digestion and lipid transport seems to be highly conserved between Nematostella and bilaterians, providing an opportunity to elucidate the ancestral state of mechanisms underlying energy homeostasis in the last common ancestor to cnidarians and bilaterians.Doktorgradsavhandlin

Biopsable Neural Tissues: Toward New Biomarkers for Parkinson's Disease?

Biomarkers for Parkinson's disease (PD) are mainly intended for the early diagnosis of the disease and to monitor its progression, two aspects insufficiently covered by clinical evaluation. In the last 20 years, the search for biomarkers has been supported by technological advances in the fields of molecular genetics and neuroimaging. Nevertheless, no fully validated biomarker is yet available, and there is still a need for biomarkers that will complement those already available. Development of biomarkers for PD has been hampered by the fact that the core pathology lies in the brainstem, hidden from direct study in living patients. In this context, the recent observations that clearly demonstrated the presence of PD pathology in peripheral neural tissues provide new opportunities to develop original histopathological markers of the disease. Some of these peripheral tissues, especially the enteric nervous system, by being assessable using routine biopsies, could represent a window to assess in vivo the neuropathological processes occurring in PD

2D Axisymmetric Coupled Computational Fluid Dynamics–Kinetics Modeling of a Nonthermal Arc Plasma Torch for Diesel Fuel Reforming

International audienceThe present study is dedicated to the 2D axisymmetric coupled computational fluid dynamics–kinetics modeling of a plasma-assisted diesel fuel reformer developed for two different applications: (i) onboard H2 production for fuel-cell feeding and (ii) NOx trap regeneration. These cases correspond to very different reaction conditions. In the first case, diesel fuel reacts with air, while in the second case, it reacts with diesel engine exhaust gas. The plasma is modeled with a simple power source domain. n-Heptane has been chosen as a surrogate molecule for diesel fuel. A reduced kinetic mechanism is used for the study. Both cases have been studied under adiabatic and nonadiabatic postreactor conditions. We can distinguish four zones in the torch: a reactant heating zone, a plasma zone, a mixing zone, and a postdischarge zone. The main precursors of the reforming reactions are H, O, and OH radicals. The oxygen rate is a key point of the application. The thermal losses make the reforming reaction difficult to ignite and beget a lower syngas production and a lower postdischarge temperature. For the nonadiabatic reactor, the results have been compared to experimental data. The model predicts relevant gas fractions

Evolutionarily conserved aspects of animal nutrient uptake and transport in sea anemone vitellogenesis

The emergence of systemic nutrient transport was a key challenge during animal evolution, yet it is poorly understood. Circulatory systems distribute nutrients in many bilaterians (e.g., vertebrates and arthropods) but are absent in non-bilaterians (e.g., cnidarians and sponges), where nutrient absorption and transport remain little explored at molecular and cellular levels. Vitellogenesis, the accumulation of egg yolk, necessitates high nutrient influx into oocytes and is present throughout animal phyla and therefore represents a well-suited paradigm to study nutrient transport evolution. With that aim, we investigated dietary nutrient transport to the oocytes in the cnidarian Nematostella vectensis (Anthozoa). Using a combination of fluorescent bead labeling and marker gene expression, we found that phagocytosis, micropinocytosis, and intracellular digestion of food components occur within the gonad epithelium. Pulse-chase experiments further show that labelled fatty acids rapidly translocate from the gonad epithelium through the extracellular matrix (ECM) into oocytes. Expression of conserved lipid transport proteins vitellogenin (vtg) and apolipoprotein-B (apoB) and colocalization of labeled fatty acids with a fluorescently tagged ApoB protein further support the lipid-shuttling role of the gonad epithelium. Complementary oocyte expression of very low-density lipoprotein receptor (vldlr) orthologs, which mediate endocytosis of bilaterian ApoB- and Vtg-lipoproteins, supports that this evolutionarily conserved ligand/receptor pair underlies lipid transport during sea anemone vitellogenesis. In addition, we identified lipid- and ApoB-rich cells with potential lipid transport roles in the ECM. Altogether, our work supports a long-standing hypothesis that an ECM-based lipid transport system predated the cnidarian-bilaterian split and provided a basis for the evolution of bilaterian circulatory systems.publishedVersio

David Adé & Thierry Piot (dir.), La formation, entre universitarisation et professionnalisation. Tension et perspectives dans des métiers de l’interaction humaine

L’objet de cet ouvrage collectif porte sur les enjeux et les tensions liés à la professionnalisation et à l’universitarisation des formations dans les métiers de l’interaction humaine. Publié aux presses universitaires de Rouen et du Havre dans la collection « La professionnalisation, entre travail et formation » dirigée par Richard Wittorski, ce livre émane d’un travail de recherche sur les nouvelles conditions de professionnalisation et de développement professionnel. La question centrale d..

3D MHD modelling of low current-high voltage dc plasma torch under restrike mode

International audienceWe present in this paper a magnetohydrodynamic (MHD) modelling of the gliding arc behaviour of a dc plasma torch operating with air under low current and high voltage conditions. The low current leads to instabilities and difficulties with simulating the process because the magnetic field is not sufficient to constrict the arc. The model is 3D, time dependent and the MHD equations are solved using CFD software Code_Saturne®. Although the arc is definitively non-local thermodynamic equilibrium (LTE), the LTE assumption is considered as a first approach. The injection of air is tangential. A hot gas channel reattachment model has been used to simulate the restriking process of the arc root. After the description of the model, the most appropriate electrical voltage breakdown parameter has been selected in comparing with experimental results. A typical operating point is then studied in detail and shows the helical shape of the arc discharge in the nozzle. Finally, the mass flow rate and the current have been varied in the range 0.16-0.5 g s−1 and 100-300 mA, respectively, corresponding to typical glidarc operating points of our experimental plasma torch. The model shows good consistency with experimental data in terms of global behaviour, arc length, mean voltage and glidarc frequency

Test du modèle unitaire de dépense des ménages sur les données canadiennes de 2009

Dans ce mémoire de maîtrise, nous utilisons les microdonnées de l’Enquête sur les dépenses des ménages de Statistique Canada en 2009 pour tester la validité empirique du modèle unitaire de dépense des ménages. En s’inspirant de l’étude conduite par Phipps et Burton en 1998, nous tentons une actualisation de leurs résultats ainsi qu’une analyse de l’évolution du comportement des ménages canadiens entre 1992 et 2009. La nouveauté présentée dans ce mémoire de maîtrise tient justement dans ces résultats. Dans la majorité des catégories de dépenses, nous ne rejetons plus le modèle unitaire et nous en mesurons les implications. Entre ces deux études, les différences entre l’homme et la femme dans les couples canadiens se sont atténuées, ils ont de plus en plus les mêmes préférences en terme de consommation. Enfin, nous poursuivons en apportant un test du modèle coopératif développé par Browning, Bourguignon, Chiappori et Lechene (1994) sur la demande en biens exclusifs. Nous en déduisons un aperçu de la répartition du pouvoir de dépense au sein des ménages canadiens

Theoretical study of Diesel fuel reforming by a non-thermal arc discharge

International audienceNitrogen oxides are in the center of future EURO VI norm, the European anti-pollution norm namely for Diesel powered vehicles. NOx (NO, NO2,...) are very irritant pollutants for people and are considered as tropospherical ozone precursors. Their effect is observed when ozone peak pollution is noticed during rush hours. A promising post-treatment technology is to add a NOx trap in exhaust line to store NOx under nitrate form. An alternative to fuel-air ratio increase and catalytic tech-nologies purge is the use of non-thermal plasma. Plasma reforming of diesel fuel and exhaust gas mix-ture creates reducing chemical species like hydrogen and carbon monoxide, which are able to purge the NOx trap