499 research outputs found
Long-Lasting Alterations in Membrane Properties, K+ Currents, and Glutamatergic Synaptic Currents of Nucleus Accumbens Medium Spiny Neurons in a Rat Model of Alcohol Dependence
Chronic alcohol exposure causes marked changes in reinforcement mechanisms and motivational state that are thought to contribute to the development of cravings and relapse during protracted withdrawal. The nucleus accumbens (NAcc) is a key structure of the mesolimbic dopaminergic reward system. Although the NAcc plays an important role in mediating alcohol-seeking behaviors, little is known about the molecular mechanisms underlying alcohol-induced neuroadaptive changes in NAcc function. The aim of this study was to investigate the effects of chronic intermittent ethanol (CIE) treatment, a rat model of alcohol withdrawal and dependence, on intrinsic electrical membrane properties and glutamatergic synaptic transmission of medium spiny neurons (MSNs) in the NAcc core during protracted withdrawal. We show that CIE treatment followed by prolonged withdrawal increased the inward rectification of MSNs observed at hyperpolarized potentials. In addition, MSNs from CIE-treated animals displayed a lower input resistance, faster action potentials (APs), and larger fast afterhyperpolarizations (fAHPs) than MSNs from vehicle-treated animals, all suggestive of increases in K+-channel conductances. Significant increases in the Cs+-sensitive inwardly rectifying K+-current accounted for the increased input resistance, while increases in the A-type K+-current accounted for the faster APs and increased fAHPs in MSNs from CIE rats. We also show that the amplitude and the conductance of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated mEPSCs were enhanced in CIE-treated animals due to an increase in a small fraction of functional postsynaptic GluA2-lacking AMPARs. These long-lasting modifications of excitability and excitatory synaptic receptor function of MSNs in the NAcc core could play a critical role in the neuroadaptive changes underlying alcohol withdrawal and dependence
Les « X » Ă QuĂ©bec : La construction discursive dâun groupe exclusif
De 1996 Ă 2005, lâĂ©mission radiophonique « Le monde parallĂšle de Jeff Fillion » prend une place prĂ©pondĂ©rante dans lâunivers mĂ©diatique de QuĂ©bec. Lâengouement crĂ©Ă© par cette radio repose sur un ensemble de constructions discursives qui suscitent un fort sentiment dâappartenance. Dans cet article, nous voulons explorer de façon spĂ©cifique la mĂ©canique discursive qui contribue Ă la dĂ©finition du groupe des X, les supporters de la station CHOI. Deux mouvements discursifs complĂ©mentaires Ă lâoeuvre dans la construction identitaire des X telle quâopĂ©rĂ©e par Fillion seront dĂ©crits. Le premier mouvement, positif, consiste Ă proposer aux auditeurs de CHOI (des X potentiels) un rapport au monde auquel ils vont sâidentifier ; le second, nĂ©gatif, est une construction identitaire « contre » oĂč lâidentitĂ© des X est suggĂ©rĂ©e Ă travers la prĂ©sentation dĂ©prĂ©ciative dâindividus, de groupes et dâidĂ©ologies. De ce double mouvement Ă©merge une reprĂ©sentation des X incarnant la « vraie » ville de QuĂ©bec, un QuĂ©bec opposĂ© tant Ă celui que reprĂ©sente son Ă©lite, quâau MontrĂ©al « de la âcliqueâ du Plateau Mont-Royal ». Notre Ă©tude repose sur lâanalyse de cinq Ă©missions de Fillion diffusĂ©es Ă lâĂ©tĂ© et Ă lâautomne 2004, moment propice au dĂ©ploiement de stratĂ©gies de polarisation alors que la survie de la station de radio CHOI est menacĂ©e et que Fillion lutte pour conserver son poste dâanimateur.From 1996 to 2005, the radio program Le monde parallele de Jeff Fillion held a predominant position in QuĂ©bec Cityâs media world. The strong following built by this radio program was generated through a series of discursive constructions that created a strong sense of belonging. This paper aims specifically to explore the discursive mechanism that contributes to the definition of Generation X, the group from which the CHOI radio station drew its audience. Two additional discursive movements that contribute to the X groupâs sense of identity, as developed by Fillion, will be described. The first of these, being positive, consists in offering CHOI listeners (who are potential Xâs) a relationship to the world with which they will identify; the second, which is negative, is an adverse identity construction in which the identity of the Xâs is suggested through the derogatory presentation of individuals, groups, and ideologies. From this twofold movement emerges a representation of the Xâs that embodies the ârealâ QuĂ©bec City, a QuĂ©bec City opposed both to that represented by its Ă©lite and to the MontrĂ©al of the âPlateau Mont-Royal cliqueâ. Our study is based on the analysis of five broadcasts that Fillion made in the summer and autumn of 2004, an ideal moment for the deployment of polarization strategies while the survival of the CHOI radio station was threatened and Fillion was struggling to keep his position as a radio host
Adaptation de l'Archaea halophile halobacterium salinarum aux stress environnementaux : mécanismes de survie et rÎle de la protéolyse intracellulaire
Molecular systems described for Archaea show primitive and simple characteristics, compared to their homologous eukaryotes. In addition, extremophilic characteristic results in an hyper-robust which makes in vitro manipulation and structural studies much easier. Thus, Archaea represent good models for understanding complex cellular functions, particularly those that involve large molecular machines, such as those involved in proteolysis. My thesis consisted in understanding the resistance mechanisms and the importance of proteolytic systems in the adaptation of halophilic Archaea to environmental stresses. Halophilic Archaea accumulate multi-molar concentrations of KCl / NaCl in their cytosol (3.4M KCl / NaCl 1.1M for Halobacterium Salinarum). This requires a very special biochemistry that allows operation in solvents where free water is scarce. Thus, the proteins of these organisms are themselves halophilic and are soluble and folded only in extreme salinity conditions (2 to 5 M). This particular biochemistry partly explain the extraordinary ability of halophilic Archaea to resist physical and chemical stress (temperature, radiation, dehydration). We study the response of the halophilic Archaea strict H. salinarum at low-salinity stress. Indeed, beyond the osmotic shock, the fall of the environment salt concentration causes a decrease in the intracellular KCl concentration, which should have a direct effect on the folding state of intracellular protein, as in case of heat stress. In the first part of this thesis, a study was conduct to determine viability limits and cytosolic modifications, associated with a salinity decrease. These studies involve intracellular salt dosages, viability studies (microscopic counts, color live / dead), induction of chaperone proteins linked to stress response and biophysical neutron experiments, to evaluate the effect of stress on proteins folding. In this work, a phenomenon of survival at low salinity linked to morphological changes was revealed. To describe this phenomenon, this second study involves confocal microscopy experiences, fluorescence microscopy, viability tests, counting on box, scanning electron microscopy, electron microscopy by negative staining, salt intracellular dosages and proteins separation experiments, to study the overall proteome composition during low salinity stress. In this study, a fall of the intracellular Kâș concentration and the proteome clarification during stress was revealed. Low salt concentrations causes halophiles proteins denaturation, the accumulation of misfolded proteins in the cytoplasm involves chaperones systems and intracellular proteolysis machinery. In this context, another objective of my thesis was to contribute to the understanding of the intracellular proteolysis role in the PAN-proteasome system and in the aminopeptidase TET complex, in stress conditions established in previous studies. This part of the thesis involves experiments of endopeptidase activity assay, aminopeptidase activity assay, quantification of mRNA genic expression by Northern blot, immunoprecipitation, proteins separation by sucrose gradient and proteasome chemical inhibition (drug). We show the role of the PAN-proteasome system in stress response and we deepen our understanding of the aminopeptidase TET role in vivo. This protease appears to have an independent role of the proteasome complex. The protease TET seems to participate at the amino acids treatment in cells to maintain the metabolic activities in nutritional deficiencies.Les systĂšmes molĂ©culaires dĂ©crits chez les Archaea mettent en Ă©vidence un caractĂšre primitif et une simplicitĂ©, comparativement Ă leurs homologues eucaryotes. Par ailleurs, leur caractĂšre extrĂȘmophile a pour consĂ©quence une hyper-robustesse qui rend leur manipulation in vitro et les Ă©tudes structurales beaucoup plus aisĂ©es. Ainsi les Archaea reprĂ©sentent de bons modĂšles pour comprendre les fonctions cellulaires complexes, particuliĂšrement celles qui mettent en jeu de grandes machineries molĂ©culaires, comme celles impliquĂ©es dans la protĂ©olyse. Mon travail de thĂšse a consistĂ© Ă comprendre les mĂ©canismes de rĂ©sistance et l'importance des systĂšmes de protĂ©olyse dans l'adaptation des Archaea halophiles aux stress environnementaux. Les Archaea halophiles accumulent des concentrations multi-molaires de KCl/NaCl dans leur cytosol (3.4M KCl / 1.1M NaCl chez Halobacterium salinarum). Ainsi, les protĂ©ines de ces organismes sont elles-mĂȘmes halophiles et ne sont solubles et repliĂ©es que dans des conditions de salinitĂ© extrĂȘmes (de 2 Ă 5M).Nous avons Ă©tudiĂ© la rĂ©ponse de l'Archaea halophile stricte H. salinarum Ă des stress, dont les stress Ă basse salinitĂ©, en se focalisant en particulier sur les modifications de la dynamique molĂ©culaire du protĂ©ome in vivo (diffusion neutronique). Au cours de ce travail, il a Ă©tĂ© mis en Ă©vidence un phĂ©nomĂšne de survie Ă la basse salinitĂ© associĂ© Ă des modifications morphologiques.Un autre objectif de ma thĂšse a Ă©tĂ© de contribuer Ă la comprĂ©hension du rĂŽle dans la protĂ©olyse intracellulaire du complexe aminopeptidasique TET, dans les conditions de stress mises en place dans les Ă©tudes prĂ©cĂ©dentes
Adaptation de l'Archaea halophile halobacterium salinarum aux stress environnementaux : mécanismes de survie et rÎle de la protéolyse intracellulaire
Molecular systems described for Archaea show primitive and simple characteristics, compared to their homologous eukaryotes. In addition, extremophilic characteristic results in an hyper-robust which makes in vitro manipulation and structural studies much easier. Thus, Archaea represent good models for understanding complex cellular functions, particularly those that involve large molecular machines, such as those involved in proteolysis. My thesis consisted in understanding the resistance mechanisms and the importance of proteolytic systems in the adaptation of halophilic Archaea to environmental stresses. Halophilic Archaea accumulate multi-molar concentrations of KCl / NaCl in their cytosol (3.4M KCl / NaCl 1.1M for Halobacterium Salinarum). This requires a very special biochemistry that allows operation in solvents where free water is scarce. Thus, the proteins of these organisms are themselves halophilic and are soluble and folded only in extreme salinity conditions (2 to 5 M). This particular biochemistry partly explain the extraordinary ability of halophilic Archaea to resist physical and chemical stress (temperature, radiation, dehydration). We study the response of the halophilic Archaea strict H. salinarum at low-salinity stress. Indeed, beyond the osmotic shock, the fall of the environment salt concentration causes a decrease in the intracellular KCl concentration, which should have a direct effect on the folding state of intracellular protein, as in case of heat stress. In the first part of this thesis, a study was conduct to determine viability limits and cytosolic modifications, associated with a salinity decrease. These studies involve intracellular salt dosages, viability studies (microscopic counts, color live / dead), induction of chaperone proteins linked to stress response and biophysical neutron experiments, to evaluate the effect of stress on proteins folding. In this work, a phenomenon of survival at low salinity linked to morphological changes was revealed. To describe this phenomenon, this second study involves confocal microscopy experiences, fluorescence microscopy, viability tests, counting on box, scanning electron microscopy, electron microscopy by negative staining, salt intracellular dosages and proteins separation experiments, to study the overall proteome composition during low salinity stress. In this study, a fall of the intracellular Kâș concentration and the proteome clarification during stress was revealed. Low salt concentrations causes halophiles proteins denaturation, the accumulation of misfolded proteins in the cytoplasm involves chaperones systems and intracellular proteolysis machinery. In this context, another objective of my thesis was to contribute to the understanding of the intracellular proteolysis role in the PAN-proteasome system and in the aminopeptidase TET complex, in stress conditions established in previous studies. This part of the thesis involves experiments of endopeptidase activity assay, aminopeptidase activity assay, quantification of mRNA genic expression by Northern blot, immunoprecipitation, proteins separation by sucrose gradient and proteasome chemical inhibition (drug). We show the role of the PAN-proteasome system in stress response and we deepen our understanding of the aminopeptidase TET role in vivo. This protease appears to have an independent role of the proteasome complex. The protease TET seems to participate at the amino acids treatment in cells to maintain the metabolic activities in nutritional deficiencies.Les systĂšmes molĂ©culaires dĂ©crits chez les Archaea mettent en Ă©vidence un caractĂšre primitif et une simplicitĂ©, comparativement Ă leurs homologues eucaryotes. Par ailleurs, leur caractĂšre extrĂȘmophile a pour consĂ©quence une hyper-robustesse qui rend leur manipulation in vitro et les Ă©tudes structurales beaucoup plus aisĂ©es. Ainsi les Archaea reprĂ©sentent de bons modĂšles pour comprendre les fonctions cellulaires complexes, particuliĂšrement celles qui mettent en jeu de grandes machineries molĂ©culaires, comme celles impliquĂ©es dans la protĂ©olyse. Mon travail de thĂšse a consistĂ© Ă comprendre les mĂ©canismes de rĂ©sistance et l'importance des systĂšmes de protĂ©olyse dans l'adaptation des Archaea halophiles aux stress environnementaux. Les Archaea halophiles accumulent des concentrations multi-molaires de KCl/NaCl dans leur cytosol (3.4M KCl / 1.1M NaCl chez Halobacterium salinarum). Ainsi, les protĂ©ines de ces organismes sont elles-mĂȘmes halophiles et ne sont solubles et repliĂ©es que dans des conditions de salinitĂ© extrĂȘmes (de 2 Ă 5M).Nous avons Ă©tudiĂ© la rĂ©ponse de l'Archaea halophile stricte H. salinarum Ă des stress, dont les stress Ă basse salinitĂ©, en se focalisant en particulier sur les modifications de la dynamique molĂ©culaire du protĂ©ome in vivo (diffusion neutronique). Au cours de ce travail, il a Ă©tĂ© mis en Ă©vidence un phĂ©nomĂšne de survie Ă la basse salinitĂ© associĂ© Ă des modifications morphologiques.Un autre objectif de ma thĂšse a Ă©tĂ© de contribuer Ă la comprĂ©hension du rĂŽle dans la protĂ©olyse intracellulaire du complexe aminopeptidasique TET, dans les conditions de stress mises en place dans les Ă©tudes prĂ©cĂ©dentes
Genetic structure and evolution of the Leishmania genus in Africa and Eurasia: what does MLSA tell us
Leishmaniasis is a complex parasitic disease from a taxonomic, clinical and epidemiological point of view. The role of genetic exchanges has been questioned for over twenty years and their recent experimental demonstration along with the identification of interspecific hybrids in natura has revived this debate. After arguing that genetic exchanges were exceptional and did not contribute to Leishmania evolution, it is currently proposed that interspecific exchanges could be a major driving force for rapid adaptation to new reservoirs and vectors, expansion into new parasitic cycles and adaptation to new life conditions. To assess the existence of gene flows between species during evolution we used MLSA-based (MultiLocus Sequence Analysis) approach to analyze 222 Leishmania strains from Africa and Eurasia to accurately represent the genetic diversity of this genus. We observed a remarkable congruence of the phylogenetic signal and identified seven genetic clusters that include mainly independent lineages which are accumulating divergences without any sign of recent interspecific recombination. From a taxonomic point of view, the strong genetic structuration of the different species does not question the current classification, except for species that cause visceral forms of leishmaniasis (L. donovani, L. infantum and L. archibaldi). Although these taxa cause specific clinical forms of the disease and are maintained through different parasitic cycles, they are not clearly distinct and form a continuum, in line with the concept of species complex already suggested for this group thirty years ago. These results should have practical consequences concerning the molecular identification of parasites and the subsequent therapeutic management of the disease
Addressing the problem of plastic waste: Development of an enzymatic process for PET recycling
Every day, media and NGOs describe the society\u27s disaffection for plastics accused of polluting the planet. All major brand-owners made commitments to solve this problem (e.g. Coca-Cola, NestlĂ©, Danone, PepsiCo, Suntory, Unilever, LâOrĂ©al, Nike) and announced a future with less plastic waste by 2025.
Nevertheless, only 6 years before the announced term, no effective solution is yet available to meet these goals. Indeed, existing technologies like thermo-mechanical recycling leads to loss in mechanical properties of the polymer and even if several chemical recycling processes are under development, they suffer from the disadvantages of using organic solvents, high reaction temperatures and the need of an intensive waste sorting. Consequently, enzymatic recycling appears as a pertinent solution notably because the enzyme selectivity avoids a drastic sorting of waste and enables the recycling of complex plastics (multi-layers construction in some bottles of sparkling water for instance), it is an eco-friendly reaction in water and because of savings in energy consumption due to a low temperature of reaction.
Using a computer-aided engineering strategy, we drastically improved the depolymerizing performance of the best identified enzyme candidate. Utilizing site-directed mutagenesis targeted at the active site, combined with three-dimensional fold stabilization, we engineered an enzyme variant, demonstrating an astounding increase in thermostability combined with a high activity. This enzyme is able to depolymerize 90% of PET waste (200g/kg) into monomers, terephthalic acid and ethylene glycol, in less than 10 hours.
The downstream processing was developed and optimized leading to the demonstration that this enzymatic technology could enable the use of an industrial plastic waste to produce again PET monomers and ultimately a bottle from this recycled PET.
We hope to demonstrate the strong potential of the enzymatic technology jointly developed by CARBIOS and LISBP to provide a breakthrough solution to help solve societyâs growing plastic waste problem
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Synthetic peripherally-restricted cannabinoid suppresses chemotherapy-induced peripheral neuropathy pain symptoms by CB1 receptor activation.
Chemotherapy-induced peripheral neuropathy (CIPN) is a severe and dose-limiting side effect of cancer treatment that affects millions of cancer survivors throughout the world and current treatment options are extremely limited by their side effects. Cannabinoids are highly effective in suppressing pain symptoms of chemotherapy-induced and other peripheral neuropathies but their widespread use is limited by central nervous system (CNS)-mediated side effects. Here, we tested one compound from a series of recently developed synthetic peripherally restricted cannabinoids (PRCBs) in a rat model of cisplatin-induced peripheral neuropathy. Results show that local or systemic administration of 4-{2-[-(1E)-1[(4-propylnaphthalen-1-yl)methylidene]-1H-inden-3-yl]ethyl}morpholine (PrNMI) dose-dependently suppressed CIPN mechanical and cold allodynia. Orally administered PrNMI also dose-dependently suppressed CIPN allodynia symptoms in both male and female rats without any CNS side effects. Co-administration with selective cannabinoid receptor subtype blockers revealed that PrNMI's anti-allodynic effects are mediated by CB1 receptor (CB1R) activation. Expression of CB2Rs was reduced in dorsal root ganglia from CIPN rats, whereas expression of CB1Rs and various endocannabinoid synthesizing and metabolizing enzymes was unaffected. Daily PrNMI treatment of CIPN rats for two weeks showed a lack of appreciable tolerance to PrNMI's anti-allodynic effects. In an operant task which reflects cerebral processing of pain, PrNMI also dose-dependently suppressed CIPN pain behaviors. Our results demonstrate that PRCBs exemplified by PrNMI may represent a viable option for the treatment of CIPN pain symptoms
Deviation from the normal mode expansion in a coupled graphene-nanomechanical system
We optomechanically measure the vibrations of a nanomechanical system made of
a graphene membrane suspended on a silicon nitride nanoresonator. When probing
the thermal noise of the coupled nanomechanical device, we observe a
significant deviation from the normal mode expansion. It originates from the
heterogeneous character of mechanical dissipation over the spatial extension of
coupled eigenmodes, which violates one of the fundamental prerequisite for
employing this commonly used description of the nanoresonators' thermal noise.
We subsequently measure the local mechanical susceptibility and demonstrate
that the fluctuation-dissipation theorem still holds and permits a proper
evaluation of the thermal noise of the nanomechanical system. Since it
naturally becomes delicate to ensure a good spatial homogeneity at the
nanoscale, this approach is fundamental to correctly describe the thermal noise
of nanomechanical systems which ultimately impact their sensing capacity
Ătude expĂ©rimentale et modĂ©lisation de l'Ă©coulement de jeu d'une aube fixe isolĂ©e
International audienceThe tip-leakage flow has detrimental effects on the performance of compressors. In this paper the effects of gap height and incoming casing boundary layer thickness are analyzed. Velocity and total pressure measurements are carried out in a plane behind the trailing edge of an isolated fixed blade. The total pressure loss is decomposed in a vortex loss and a wake loss. It appears that the increase of total pressure losses with the gap height comes essentially from the vortex part. This observation motivated the development of a model based on an analogy with a jet in crossflow to estimate the tip-leakage vortex circulation. The predictions of this model are consistent with the experimental data for gaps smaller than 4 % of chord
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