Improvement of rat islet viability during transplantation: validation of pharmacological approach to induce VEGF overexpression:

Delayed and insufficient revascularization during islet transplantation deprives islets of oxygen and nutrients, resulting in graft failure. Vascular endothelial growth factor (VEGF) could play a critical role in islet revascularization. We aimed to develop pharmacological strategies for VEGF overexpression in pancreatic islets using the iron chelator deferoxamine (DFO), thus avoiding obstacles or safety risks associated with gene therapy. Rat pancreatic islets were infected in vivo using an adenovirus (ADE) encoding human VEGF gene (4.10(8) pfu/pancreas) or were incubated in the presence of DFO (10 mumol/L). In vitro viability, functionality, and the secretion of VEGF were evaluated in islets 1 and 3 days after treatment. Infected islets or islets incubated with DFO were transplanted into the liver of syngenic diabetic rats and the graft efficiency was estimated in vivo by measuring body weight, glycemia, C-peptide secretion, and animal survival over a period of 2 months. DFO induced transient VEGF overexpression over 3 days, whereas infection with ADE resulted in prolonged VEGF overexpression lasting 14 days; however, this was toxic and decreased islet viability and functionality. The in vivo study showed a decrease in rat deaths after the transplantation of islets treated with DFO or ADE compared with the sham and control group. ADE treatment improved body weight and C-peptide levels. Gene therapy and DFO improved metabolic control in diabetic rats after transplantation, but this effect was limited in the presence of DFO. The pharmacological approach is an interesting strategy for improving graft efficiency during transplantation, but this approach needs to be improved with drugs that are more specific

Large-scale genome sequencing of mycorrhizal fungi provides insights into the early evolution of symbiotic traits

Mycorrhizal fungi are mutualists that play crucial roles in nutrient acquisition in terrestrial ecosystems. Mycorrhizal symbioses arose repeatedly across multiple lineages of Mucoromycotina, Ascomycota, and Basidiomycota. Considerable variation exists in the capacity of mycorrhizal fungi to acquire carbon from soil organic matter. Here, we present a combined analysis of 135 fungal genomes from 73 saprotrophic, endophytic and pathogenic species, and 62 mycorrhizal species, including 29 new mycorrhizal genomes. This study samples ecologically dominant fungal guilds for which there were previously no symbiotic genomes available, including ectomycorrhizal Russulales, Thelephorales and Cantharellales. Our analyses show that transitions from saprotrophy to symbiosis involve (1) widespread losses of degrading enzymes acting on lignin and cellulose, (2) co-option of genes present in saprotrophic ancestors to fulfill new symbiotic functions, (3) diversification of novel, lineage-specific symbiosis-induced genes, (4) proliferation of transposable elements and (5) divergent genetic innovations underlying the convergent origins of the ectomycorrhizal guild. Mycorrhizal symbioses have evolved repeatedly in diverse fungal lineages. A large phylogenomic analysis sheds light on genomic changes associated with transitions from saprotrophy to symbiosis, including divergent genetic innovations underlying the convergent origins of the ectomycorrhizal guild.Peer reviewe

Transport et dégradation de pesticides en zones humides : une approche multi-échelles

A mechanistic understanding of transport and degradation processes of modern agricultural pesticides, including chiral pesticides, is critical for predicting their fate in the environment. In agricultural landscapes, wetlands can intercept pesticide-contaminated runoff or groundwater and improve water quality through various retention and degradation processes, which remain unknown. In a downscaling approach, three different wetlands receiving agricultural runoff were used as ‘natural laboratories’ to investigate the fate of widely used pesticides. Overall, our results showed that dynamics of hydrological and redox conditions largely influenced pesticide sorption mechanisms and their distribution over time within wetland compartments, thereby controlling degradation processes. While large-scale studies provide integrative information on pesticide dissipation and distribution patterns with respect to wetland functioning, small-scale investigations using novel methods such as isotope and enantiomer analyses characterize underlying molecular processes governing pesticide degradation.La compréhension des mécanismes de transport et de dégradation des pesticides émergents est primordiale pour prédire leur devenir dans l’environnement. Les zones humides peuvent intercepter des eaux de ruissellement ou des souterraines contaminées par les pesticides et les traiter par le biais de processus de rétention et de dégradation, encore peu connus. Dans une approche multi-échelles, trois zones humides recevant des eaux polluées par les pesticides ont été utilisées comme des « laboratoires naturels » pour étudier le devenir de pesticides couramment utilisés. Cette thèse souligne l’influence des conditions hydrologiques et redox sur la distribution des pesticides au sein des différents compartiments des zones humides ainsi que sur leur potentiel de dégradation. Alors que les études à grande échelle fournissent des informations intégratives sur la dissipation et la rétention des pesticides en lien avec le développement de la végétation, les études à petite échelle utilisant des techniques innovantes telles que les analyses isotopiques et énantiomériques permettent l’exploration des processus moléculaires de dégradation des pesticides

Etude comparative de différentes méthodes de diagnostic de la paratuberculose caprine

Le diagnostic clinique de la paratuberculose chez la chèvre étant très difficile à établir, il est généralement nécessaire de recourir à l utilisation de techniques expérimentales. Dans le cadre de cette étude, 532 chèvres issues de 15 élevages des Deux-Sèvres ont fait l objet d une recherche de paratuberculose, par 7 méthodes de diagnostic : la culture fécale, la bactérioscopie, la PCR, l immuno-diffusion en gélose et 3 tests ELISA commercialisés par des fabricants différents. Les résultats obtenus par les différentes techniques ont été comparés à ceux de la culture fécale, considérée comme méthode de référence. Les sensibilité et spécificité de chaque test ont été calculées, permettant ainsi de les classer par ordre de sensibilité croissante (bactérioscopie, IDG, ELISA, PCR) ou de spécificité croissante (ELISA (2 kits), PCR, ELISA (3ème kit), bactérioscopie, IDG). Les sensibilités sont extrêmement variables (5,6 à 55,6 %). En revanche, les spécificités sont toutes supérieures à 94 %. En outre, cette étude a mis en évidence un faible taux de positivité des animaux âgés de moins de 2 ans, et justifie ainsi de n appliquer les tests de dépistage de la paratuberculose qu aux chèvres de 2 ans et plus.MAISONS-ALFORT-Ecole Vétérin (940462302) / SudocSudocFranceF

Transport et dégradation de pesticides en zones humides (une approche multi-échelles)

La compréhension des mécanismes de transport et de dégradation des pesticides émergents est primordiale pour prédire leur devenir dans l environnement. Les zones humides peuvent intercepter des eaux de ruissellement ou des souterraines contaminées par les pesticides et les traiter par le biais de processus de rétention et de dégradation, encore peu connus. Dans une approche multi-échelles, trois zones humides recevant des eaux polluées par les pesticides ont été utilisées comme des laboratoires naturels pour étudier le devenir de pesticides couramment utilisés. Cette thèse souligne l influence des conditions hydrologiques et redox sur la distribution des pesticides au sein des différents compartiments des zones humides ainsi que sur leur potentiel de dégradation. Alors que les études à grande échelle fournissent des informations intégratives sur la dissipation et la rétention des pesticides en lien avec le développement de la végétation, les études à petite échelle utilisant des techniques innovantes telles que les analyses isotopiques et énantiomériques permettent l exploration des processus moléculaires de dégradation des pesticides.A mechanistic understanding of transport and degradation processes of modern agricultural pesticides, including chiral pesticides, is critical for predicting their fate in the environment. In agricultural landscapes, wetlands can intercept pesticide-contaminated runoff or groundwater and improve water quality through various retention and degradation processes, which remain unknown. In a downscaling approach, three different wetlands receiving agricultural runoff were used as natural laboratories to investigate the fate of widely used pesticides. Overall, our results showed that dynamics of hydrological and redox conditions largely influenced pesticide sorption mechanisms and their distribution over time within wetland compartments, thereby controlling degradation processes. While large-scale studies provide integrative information on pesticide dissipation and distribution patterns with respect to wetland functioning, small-scale investigations using novel methods such as isotope and enantiomer analyses characterize underlying molecular processes governing pesticide degradation.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Inflammation génitale chez la vache (mise au point de méthodes diagnostiques de terrain - Evaluation de l'efficacité de la flunixine par voie parenterale)

L'endométrite, cause majeure d'infertilité bovine, semble aujourd'hui liée à une réponse inflammatoire inappropriée. Son diagnostic, basé sur l'examen cytologique, est néanmoins impossible à mettre en oeuvre au pied de la vache. Nous avons donc recherché des techniques utilisables sur le terrain et comparé les résultats obtenus par ces méthodes à ceux obtenus par la méthode classique cytologique. Sur 125 vaches Prim'Holstein d'un même élevage, présentant des taux d'endométrite et de cervicite cytologiques de 36% et 38% respectivement, nous avons montré que les mesures de protéines et de leucocytes du mucus vaginal, réalisées à l'aide d'une bandelette urinaire, permettaient la détection d'endométrites (p<0.005) et que ces mêmes paramètres, ainsi que la cytologie vaginale et la mesure de densité optique du mucus vaginal étaient révélateurs d'une inflammation génitale, qu'elle soit endométriale ou cervicale (p<0.005). L'injection unique de flunixine s'est révélée inefficace pour limiter l'inflammation endométriale.TOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

Pesticide Mass Budget in a Stormwater Wetland

Wetlands are reactive landscape zones that provide ecosystem services, including the improvement of water quality. Field studies distinguishing pesticide degradation from retention to evaluate the sink and source functions of wetlands are scarce. This study evaluated based on a complete mass budget the partitioning, retention, and degradation of 12 pesticides in water, suspended solids, sediments, and organisms in a wetland receiving contaminated runoff. The mass budget showed the following: (i) dissolved pesticides accounted for 95% of the total load entering the wetland and the pesticide partitioning between the dissolved phase and the suspended solids varied according to the molecules, (ii) pesticides accumulated primarily in the <250 μm bed sediments during spring and late summer, and (iii) the hydrological regime or the incoming pesticide loads did not influence the pesticide dissipation, which varied according to the molecules and the wetland biogeochemical conditions. The vegetation enhanced the pesticide degradation during the vegetative phase and the pesticides were released during plant senescence. The dithiocarbamates were degraded under oxic conditions in spring, whereas glyphosate and aminomethylphosphonic acid (AMPA) degradation occurred under reducing conditions during the summer. The complete pesticide mass budget indicates the versatility of the pesticide sink and source functions of wetland systems

Comparing the thin-film rotating disk electrode and the ultramicroelectrode with cavity techniques to study carbon-supported platinum for proton exchange membrane fuel cell applications

International audienceActive layers elaborated from commercial carbon-supported platinum nanoparticles (10 wt% Pt/C, E-TEK) have been characterized from cyclic voltammetry using either the porous rotating disk electrode (RDE) or the ultramicroelectrode with cavity (UMEC) techniques. The electrochemical properties of the platinum-based active layers were compared for two classical fuel cell catalysts benchmark measurements: the platinum specific area determined from hydrogen adsorption/desorption or CO-stripping coulometry and the evaluation of kinetics parameters for oxygen reduction reaction. Whereas the porous RDE technique requires the prior preparation of an ink composed of a binder (Nafion®) and non negligible amounts of active material (at least 10 mg Pt/C powder), the UMEC is compatible with the elaboration of Nafion®-free active layers, only composed of very small amounts of Pt/C (a few nanograms). Both the UMEC and the porous RDE techniques require the correction from the oxygen diffusion in the active layer for high ORR overpotentials (E E > 0.8 V vs. NHE) only the UMEC requires a correction from the oxygen diffusion in the active layer, easily calculated using the macro-homogeneous model. The so-corrected ORR kinetic current densities are compared with that determined from other techniques of the literature, among which the thin-film RDE. Last, the comparison between UMEC including or not Nafion® and porous RDE showed the non-negligible effect of the presence of Nafion® in carbon-supported active layers, inducing modification of the platinum nanoparticles electrocatalytic activity for both CO-stripping and ORR. Thanks to its great advantages (low amount of Pt/C used, absence of binder and facile control of the quantity of active material in the cavity, shorter time of experiment, higher reproducibility) the ultra-microelectrode with cavity is a promising method to characterize fuel cell electrocatalysts. It enables Pt/C catalysts easy specific area measurements and ORR kinetics parameters determination without using any additional binder. The benefit of UMECs has been validated for the characterisation of commercial fresh or used anode active layer materials, which could not be attempted accurately using the classical RDE technique because of their high Nafion® loading

Detection of Pt^z+ Ions and Pt Nanoparticles Inside the Membrane of a Used PEMFC

International audienceThe physical and chemical state of proton exchange membrane fuel cell (PEMFC) electrocatalysts (Pt/C) were investigated after 529 h of operation under fuel cell relevant conditions (333 K, 0.12 W cm–2) and 123 h of rest time under inert atmosphere (N2). Upon aging, pronounced corrosion of the cathode electrocatalyst (carbon-supported platinum nanoparticles: Pt/C) was evidenced by field-emission gun scanning electron microscopy (FEG-SEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical techniques. Carbon corrosion was witnessed by the decrease of the cathode thickness (–60%) and by the presence of nonsupported Pt particles inside the electrode. At the cathode, the corrosion of Pt nanoparticles produces Pt(*)z+ ions which diffuse in the ionomer phase or in solution [(*) stands for ionic species present in the ionomer phase or in solution]. These ions are highly mobile inside the membrane electrode assembly (MEA) and may cross over from the cathode to the anode through the PEM. The driving force for that is the electro-osmotic drag (if Pt(*)z+ ions combine with anions and carry a negative charge) and the chemical diffusion (concentration gradient of oxidized platinum species). Consequently, Pt(*)z+ ions were detected by ultraviolet (UV) spectroscopy in the PEM. Due to the high mobility of Pt(*)z+ ions, FEG-SEM and HRTEM analysis of the cross sections of MEAs revealed a pronounced change of Pt distribution after operation. Size distributions of both anode and cathode electrocatalysts evidenced an increase of the mean particle size, tailing toward large particle sizes and particle agglomeration. Nonspherical Pt nanoparticles were detected inside the PEM, the size and shape distribution of which strongly depend on the distance from the cathode. We believe Pt(*)z+ ions are reduced chemically inside the membrane by H2 crossing over the PEM and both chemically and electrochemically at the anode/cathode

Seasonal Changes of Macroinvertebrate Communities in a Stormwater Wetland Collecting Pesticide Runoff From a Vineyard Catchment (Alsace, France)

International audienceAgricultural land use may influence macroinvertebrate communities by way of pesticide contamination associated with agricultural runoff. However, information about the relation between runoff-related pesticides and communities of benthic macroinvertebrates in stormwater wetland that receive agricultural runoff does not currently exist. Here we show changes in macroinvertebrates communities of a stormwater wetland that collects pesticidecontaminated runoff from a vineyard catchment. Sixteen runoff-associated pesticides, including the insecticide flufenoxuron, were continuously quantified at the inlet of the stormwater wetland from April to September (period of pesticide application). In parallel, benthic macroinvertebrate communities, pesticide concentrations, and physicochemical parameters in the wetland were assessed twice a month. Twenty-eight contaminated runoffs ranging from 1.1 to 114 m3 entered the wetland during the study period. Flufenoxuron concentrations in runoff-suspended solids ranged from 1.5 to 18.5 lg kg-1 and reached 6 lg kg-1 in the wetland sediments. However, flufenoxuron could not be detected in water. The density, diversity, and abundance of macroinvertebrates largely varied over time. Redundancy and formal concept analyses showed that concentrations of flufenoxuron, vegetation cover, and flow conditions significantly determine the community structures of stormwater wetland macroinvertebrates. This study shows that flow conditions, vegetation cover, and runoff-related pesticides jointly affect communities of benthic macroinvertebrates in stormwater wetlands