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3D Assembly of Nanostructured ZnO: Synthesis Design, Formation Mechanism, Hierarchy and Photocatalytic Properties
No full textThe synthesis of nanostructured ZnO has attracted considerable attention worldwide because of its practical and potential applications. Numerous low-dimensional ZnO nanostructures, such as nanotubes, nanowires, nanobelts, nanorods, etc. have been synthesized. Whilst improvements in performance can be observed in such nanomaterials over bulk ZnO, it is expected that hierarchically structured ZnO can increase performances further still as the advantages of nanoscale structuration can be combined with the advantages of micro and macrostructuration on different length scales. However, investigations on synthesis, characterization, and applications of hierarchically nanostructured ZnO are scarce. The objectives of this thesis are to design and synthesize a series of hierarchically structured ZnO, and to evaluate their potential in photocatalytic applications.
The scientific strategy for the synthesis of hierarchically structured ZnO is to design suitable synthesis routes based around various zinc sources available. In this thesis, two different types of zinc sources, organic (i.e. dimethylzinc and zinc acetate) and inorganic (i.e. zinc nitrate and zinc chloride), have been employed to synthesize hierarchically structured ZnO. A series of hierarchical ZnO have been successfully achieved by adopting various synthesis methods. The obtained hierarchically structured zinc oxides were characterized in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption measurements, room-temperature photoluminescence spectroscopy (RT-PL), and thermogravimetry and differential scanning calorimetry (TG-DSC). Based on these characterizations, formation mechanisms were reasonably proposed. Finally, the photocatalytic performances of the as-synthesized hierarchically structured ZnO materials were investigated by examining the photodegradation of Rhodamine B (RhB) under UV light in the presence of these materials.
The present work demonstrates that hierarchically structured ZnO could be achieved by designing suitable synthesis routes dependant on the zinc source chosen. This thesis not only provides effective ways to hierarchically structured ZnO materials, but also obtains some beneficial results in terms of the optical and photocatalytic properties of these materials. This scientific strategy could subsequently be expanded to the synthesis of other hierarchically structured metal oxides.La synthèse de nanostructures en ZnO attire considérablement l’attention mondiale de part ces applications actuelles et potentielles. De nombreuses nanostructures mono- ou bi-dimensionnelles, tels que les nanotubes, nano-files, ou encore les nano-cloches, ont été synthétisées avec succès. Comparativement à ces structures, les structures hiérarchisées pourraient présenter des propriétés supérieures grâce à leur structure fines et stable. Néanmoins, les recherches sur la synthèse et la caractérisation de nanostructures hiérarchisées en ZnO sont moins rapportées dans la littérature scientifique. L’objectif de cette thèse consiste à synthétiser, d’une part, une série de nanostructures hiérarchisées en ZnO et d’autre part, à étudier leurs propriétés photocatalytiques.
La stratégie scientifique pour la synthèse de ces structures repose sur différentes voies d’assemblage utilisant une variété de source de Zn, en particulier le diméthyl de zinc, le di-acétate de zinc et d’autres sources inorganiques. Les structures obtenues ont été caractérisées par la diffraction de rayon X (DRX), la microscopie électronique à balayage (MEB), la microscopie électronique à transmission (MET), la technique d’adsorption-désorption d’azote, la photoluminescence (PL) et la thermogravimétrie (TG-DSC). Sur base de ces caractérisations, une proposition mécanistique a pu être dégagée. De plus ; les performances photocatalytiques des matériaux ont été investigués via la photodégradation de la Rhodamine B (RhB) sous l’action d’une lumière UV.
Le présent travaille démontre que les structures hiérarchisées en ZnO pourraient être générés et contrôlés en fonction du choix de la source de Zn. De plus, cette thèse démontre que ces mêmes structures présentent des propriétés optiques et photocatalytiques. Cette stratégie scientifique pourrait être étendue à la synthèse de nanostructures à base d’autres oxydes métalliques.(DOCSC02) -- FUNDP, 201
New insights on the male-to-female transdifferentiation processes in rainbow trout (Oncorhynchus mykiss) fry gonads following exposure to ethynylestradiol at the morphological and transcriptional level by in vivo and in silico approaches
No full textGonads are unique among all organs given their bipotential nature: they can develop either into an ovary or a testis from a single germ cells primordium. In mammals, the way by which cells choose between either fate is genetically controlled by the expression of a main male gene SRY (situated on the Y chromosome) that leads irrefutably to testis development. Sex differentiation is the physical achievement of events leading to the development of functional gonads. These steps allow the expression of the genetic sex into the appropriate phenotypic sex. Sex steroids are involved in all aspects of the regulation of reproductive processes in vertebrates, estrogens acting as feminizing factors and inversely androgens acting as masculinizing factors. The release of endocrine disrupting compounds (EDCs) in the aquatic environment disrupts gonads development in numerous fish species. For example, xenoestrogens (molecules that mimics the natural female hormone estradiol), even at very low doses (ng to μg/L range), induced the production of a female protein (vitellogenin) by male fish and gonads morphological disruptions such as intersex induction (e.g. ovotestis: oocyte development into the testis), which can adversely impact species reproductive success. The mechanisms underlying this issue are still largely unknown. The aim of this study was to gain insights into the molecular mechanisms involved in the male-to-female transdifferentiation processes induced by exogenous estrogenic treatment in fish. To this end, we have chronically exposed an all-male rainbow trout fry population to several concentrations (0, 0.01, 0.1, 1 and 10 μg/L) of ethynylestradiol (EE2, the most potent xenoestrogen in vivo) and investigated the alterations induced by this treatment at the morphological level by an extensive histological analysis of the gonads and at the transcriptomic level through the use of microarray. This modern genomic-based technology has enhanced opportunities to find out mechanisms of actions (MOA) and identify biomarkers related to the toxic action of a compound. However, high throughput data interpretation relies sorely on statistical analysis, genomic resource of the model species used, and bioinformatics tools. To obtain differentially expressed genes (DEGs), we have successfully adapted a bioinformatics workflow (including a re-analysis and a meta-analysis with another dataset) previously implemented for human microarray platforms, to our model fish species. The histological investigations revealed the occurrence of intersex features in rainbow trout juvenile gonads exposed to EE2, which appear more complex than those usually observed in other fish species. Three types of ovotestis were observed from the lowest concentration used, and complete sex reversal occurred at higher doses. Gene expression investigations allowed highlighting several pathways/GO Terms associated with the EE2 exposure. It represents mostly pathways involved in Cell division e.g. Cell cycle, DNA replication, and the Lipid metabolism, along with newly associated pathways such as Oocyte meiosis. A similar pattern is highlighted by the GO terms enrichment, with however more significance for terms related to Sexual reproduction (e.g. ‘Female gonad development’, ‘Gametogenesis’), ‘Cell proliferation’ and ‘Sex steroids biosynthesis’. The filtering steps of our workflow, anchored to the morphological investigations, allowed selecting several specific (e.g. Foxl2, spon2, cdkn1b) and/or sensitive (Theg, thrap3, dnaaf2) potential biomarkers of the intersex phenotype observed. Among them, Foxl2 (forkhead box protein L2), is known as an early ovarian differentiation marker. The meta-analysis of our study with a dataset investigating gene expression patterns following EE2 exposure (one high dose, 20 mg/kg of food) in a time-series encompassing earlier developmental stages gives insights into the pathways/GO Terms potentially involved in the response of EE2, by performing the intersection between the lists of differentially expressed genes (DEGs) at early stages and low concentrations. The results encompassed most of the pathways highlighted in the first experiment (e.g. Cell cycle, DNA replication), confirming their implication in the response of EE2. Two interesting pathways emerged, the PPAR signalling and the Progesterone-mediated pathways, and further studies are needed to assess their implication in the appearance of intersexuality. The application of the workflow allowed us to select 20 potential key genes implicated in the process of rainbow trout transdifferentiation. Among them, the expression of 10 genes was found to respond similarly to genes naturally expressed in developing females (e.g. genes encoding enzymes implicated in the production of androgens: cyp17a1, cyp11b and hsd17b6), and the other half show patterns of expression specific to the treatment (e.g. VTG, the gene encoding the vitellogenin, a well-known marker of xenoestrogenic exposure). We show that our workflow can be generalised to other species and different types of microarray platforms, even if the species is not yet completely sequenced. Overall, the results obtained are very promising in the field of environmental risk assessment related to EE2 exposure and the approach allowed generating new insights on the mechanistic basis of the testis feminization induced by EE2. Further studies are needed to confirm the numerous hypotheses generated by our work.Les gonades sont des organes bipotentiels qui se différencient en ovaire ou en testicule à partir d’un même primordium de cellules germinales. La destinée de l’organe est déterminée génétiquement, notamment chez les mammifères par l’expression du gène SRY (situé sur le chromosome Y) qui mène au développement du testicule. La différenciation du sexe comprend toutes les étapes menant au développement fonctionnel des gonades. Les hormones sexuelles jouent un rôle prédominant dans la régulation de ces processus, les estrogènes agissant comme facteurs féminisant, et les androgènes comme facteurs masculinisant. Il existe chez les poissons une diversité des mécanismes de détermination du sexe, ainsi qu’une labilité des processus de différenciation, qui peuvent être sensibles à des facteurs environnementaux externes. La présence accrue de perturbateurs endocriniens dans l’environnement aquatique conduit à des perturbations du développement des gonades chez de nombreuses espèces de poissons. Par exemple, les xénoestrogènes (molécules mimant l’effet de l’hormone femelle estradiol), même à de très faibles doses (de l’ordre du ng au μg/L), conduisent à la production d’une protéine femelle, la vitellogénine, par les poissons mâles, ou encore à des perturbations de la morphologie des gonades en induisant de l’intersexe (ou ovotestis : développement d’ovocytes au sein du testicule), pouvant être délétère à la survie de l’espèce. Les mécanismes par lesquels ces molécules agissent restent largement inconnus. Le principal objectif de notre travail est de mettre en évidence les voies métaboliques impliquées dans la transdifférenciation mâleKfemelle des gonades de poissons soumis à de faibles concentrations en ethynylestradiol (EE2 – un xénoestrogène puissant). Dans ce but, nous avons soumis de façon chronique des truitesKarcKenKciel mâles juvéniles à une large gamme de concentrations en EE2 (de 0.01 à 10 μg/L) afin de caractériser l’apparition d’ovotestis dans les gonades, ainsi que de mesurer leur transcriptome par la technique des microarrays. Cette technique repose sur l’utilisation d’outils statistiques et bioinformatiques puissants. Les résultats de cette approche dépendent également des connaissances génomiques disponibles pour l’espèce modèle utilisée. Nous avons adapté avec succès une méthodologie précédemment mise au point sur le génome humain à notre modèle poisson. Notre étude a mis en évidence une altération de la morphologie des gonades dès la plus faible dose utilisée, avec l’apparition de 3 types d’ovotestis, ainsi qu’une réversion complète des gonades en femelle aux plus fortes doses. Notre approche microarray nous a permis de ressortir plusieurs pathways et ontologies (GO terms) potentiellement impliqués dans la réponse des gonades à l’EE2. Le profil général des pathways implique la Division cellulaire, avec notamment le Cycle cellulaire et la Réplication de l’ADN qui apparaissent significativement enrichis et ont déjà été corrélés à des réponses d’organismes à une exposition à des composés oestrogéniques. De façon originale, la Méiose ovocytaire apparaît dans nos résultats. Un pattern similaire est observé dans l’enrichissement en GO terms, avec cependant l’émergence de termes reliés à la Reproduction sexuelle (par exemple le Développement des gonades femelle et la Gamétogenèse), la Prolifération cellulaire et la Synthèse des stéroides sexuels. Plusieurs étapes de filtration des résultats, ainsi que l’intégration des observations morphologiques nous ont permis de sélectionner plusieurs biomarqueurs potentiels, spécifiques (par exemple Foxl2,* spon2,* cdkn1b) et/ou sensibles (Theg,* thrap3,*dnaaf2) du phénotype d’intersexe. Parmi ceuxKci, Foxl2 est un marqueur de la différenciation ovarienne précoce. Une métaKanalyse de notre étude a été réalisée avec un autre jeu de donnée investiguant l’expression génique de truites arcKenKciel juvéniles exposées à de l’EE2 (une seule dose élevée : 20mg/kg de nourriture) à différent temps d’exposition, au départ de stades de développement très précoces (Jour 0 = 55 jours postKfertilisation). L’intersection des gènes différentiellement exprimés (DEGs) aux stades précoces et aux faibles doses nous a permis de mettre en évidence plusieurs pathways et GO terms potentiellement impliqués dans la réponse précoce à EE2. De façon intéressante, les résultats obtenus sont très similaires aux précédents, la majorité des pathways significatifs étant impliqués dans la Division cellulaire (dont le Cycle cellulaire et la Réplication de l’ADN). Cela renforce leur rôle dans la réponse à EE2. De plus, deux pathways originaux émergent de cette analyse, le ‘PPAR signalling’ ainsi que le ‘Progesterone mediated’ pathways. Des études complémentaires doivent être réalisées pour évaluer leur implication dans la transdifférenciation des gonades. De plus, l’application de notre méthodologie nous a permis de nous focaliser sur 20 gènes potentiellement impliqués dans les mécanismes précoces de transdifférenciation maleKfemelle. Nous avons pu mettre en évidence que dix d’entre eux présentent des profils d’expression similaires à ceux observés chez des femelles contrôles (par exemple plusieurs gènes codant pour des enzymes impliquées dans la production d’androgènes : cyp17a1,* cyp11b* et* hsd17b6). La seconde moitié des gènes présentent des profils d’expression spécifique au traitement (par exemple VTG, le gène codant pour la vitellogénine). Les résultats obtenus sont très prometteurs dans l’évaluation des risques environnementaux liés à l’exposition aux xénoestrogènes, ainsi que pour la mise en évidence de nouvelles hypothèses sur les bases mécanistiques de la féminisation des testicules soumis à l’EE2. Notre méthodologie s’avère applicable à différents types de plateformes microarray ainsi qu’à différentes espèces, même non entièrement séquencées. Des études complémentaires sont nécessaires pour confirmer les nombreuses hypothèses générées dans le cadre de ce travail.(DOCSC03) -- FUNDP, 201
Conception de nanosenseurs du type fluoroionophores immobilisés au sein de matrices silicées mésoporeuses pour le dosage des ions Hg2+
No full textOver the past few decades, one principle research area has focused on the quantification of toxic heavy metals within the organism, the environment and in industrial waste. Amongst these metals, mercury is considered as one of the most harmful due to its devastating effects on the environment and human health. To minimize the dramatic consequences of this highly toxic metal, it seems essential and urgent to design a novel fluorescent detection method to monitor Hg2+ ions based on highly sensitive and selective, fast, miniturisable, reusable and also portable optical devices which can be used to perform field measurements in-situ. Therefore, this thesis project aims at designing optical nanosensors based on fluoroionophores immobilised within mesoporous silica matrices for the detection of Hg2+ ions. To achieve the aim of this project, different fluorescent probe molecules (fluoroionophores), each responding by an enhancement in fluorescence intensity after complexation with Hg2+ ions (due to the modification of their photophysical properties), have been successfully synthesised and tested for their ability to quantify Hg2+ ions with sensitivity and selectivity. The optimisation phase of the molecular structure of the fluoroionophore revealed to be fundamental not only in order to reinforce the interaction (sensitivity and selectivity) between the ion and the recognition site of the fluorescent molecule but also to fill the immobilisation conditions of the probe molecule onto the porous support. To do this, structural changes have been made to both the chelating part (ionophore) and the fluorescent part (fluorophore) of the molecule. Sulfur and selenium have been selected as chelating atoms to the Hg2+ ion and thus incorporated into the ionophore structure and withdrawing groups (bromine and methyl ester) have been grafted onto the fluorophore, the anthracene. Through this study, it was shown that sulfur based ionophores complexed with sensitivity and selectivity both Cu2+ and Pb2+ ions whereas selenium based ionophores enabled a slight enhancement of the sensitivity and selectivity towards the Hg2+ ion. The modification of the fluorophores has also enabled to improve the sensitivity and selectivity of the fluorescent molecule. Hence the grafting of the selenide ionophore onto an anthracene derivative (bromo or methyl ester anthracene) has led to the design of extremely sensitive and selective fluoroionophores towards the Hg2+ ion. With the view to immobilising the most efficient fluoroionophore to obtain nanosensors adapted to the very sensitive and selective detection of Hg2+ ions, various highly structured mesoporous silica materials (viz. CMI-1, SBA-15 and SBA16) were synthesized and characterised. The remarkable properties that these porous matrices possess, which are ideal for the design of very efficient nanosensors, were highlighted by a suite of different characterisation techniques. These materials exhibited highly accessible specific surface areas close to 800 - 1000 m2/g and significant porous volumes of around 1 cm3/g. These materials were identified as having pores with either a bidimensional hexagonal arrangement (CMI-1 and SBA-15) or a tridimensional cubic arrangement (SBA-16), whose size varied from 2.8 to 9.0 nm, making them ideal candidates for the immobilisation of the fluoroionophore. Finally, the nanosensors were obtained by the immobilisation of the fluorescent molecule through direct impregnation and were shown to be efficient in terms of sensitivity, selectivity and response time.Durant ces dernières décennies, une des principales thématiques de recherche s’est focalisée sur la détection et le dosage des métaux lourds présents dans l’organisme, l’environnement ou encore dans les déchets industriels. Parmi ces métaux lourds nuisibles, le mercure occupe une place importante de par ses effets dévastateurs tant sur l’environnement que sur la santé de l’Homme. Dans l’optique de limiter au maximum les conséquences dramatiques de ce métal hautement toxique, il apparaît capital et urgent de développer une nouvelle méthode de détection de ces ions métalliques basée sur un système optique hautement sensible et sélectif, rapide, miniaturisable, réutilisable mais encore portable permettant, ainsi, la prise de mesures directement sur le terrain. De ce fait, ce projet de thèse proposait la conception de nanosenseurs optiques du type fluoroionophores immobilisés au sein de matrices silicées mésoporeuses pour le dosage des ions Hg2+. Afin de mener à bien ce projet, différentes nouvelles molécules sondes fluorescentes (fluoroionophores) répondant toutes par un renforcement de l’intensité de fluorescence linéaire après complexation avec l’ion Hg2+ (dû à la modification de leurs propriétés photophysiques) ont été synthétisées avec succès et testées au niveau de leurs aptitudes à doser sensiblement et sélectivement les ions Hg2+. En outre, un travail d’optimisation de la structure moléculaire du fluoroionophore s’est confirmé être fondamental en vue de renforcer l’interaction (sensibilité et sélectivité) entre l’ion et le site de reconnaissance de la molécule fluorescente mais également pour satisfaire aux conditions d’immobilisation de la molécule sonde sur le support poreux. Pour ce faire, des modifications structurales ont été apportées tant à la partie chélatante (ionophore) qu’à la partie fluorescente (fluorophore). Ainsi, le soufre et le sélénium ont été sélectionnés en tant qu’atomes complexants à l’ion Hg2+ au sein de la structure de l’ionophore et des groupements électro- (brome) ou mésomère (ester méthylique) attracteurs ont été greffés sur le fluorophore, à savoir l’anthracène. Au terme de cette étude, il a été montré que les ionophores soufrés complexaient sensiblement et sélectivement les ions Cu2+ et Pb2+ tandis que l’ionophore sélénié a permis un léger renforcement de la sensibilité et sélectivité envers l’ion Hg2+. La modification du fluorophore, quant à elle, a également permis d’améliorer la sensibilité et sélectivité de la molécule fluorescente. C’est ainsi que le greffage d’un ionophore sélénié sur un dérivé de l’anthracène (bromo ou ester méthylique anthracène) a mené à l’obtention de fluoroionophores extrêmement sensibles et sélectifs à l’ion Hg2+. Dans la perspective d’immobiliser le fluoroionophore le plus performant et, de cette manière, obtenir les nanosenseurs adaptés pour une détection très sensible et très sélective des ions Hg2+, divers matériaux silicés mésoporeux hautement structurés du type CMI-1, SBA-15 et SBA-16 ont été synthétisés et caractérisés. Grâce aux multiples techniques de caractérisation utilisées, les propriétés remarquables que présentent ces matrices poreuses pour la conception de nanosenseurs très efficaces ont pu être mises en évidence. En effet, ces matériaux affichaient des surfaces spécifiques accessibles élevées proches de 800 à 1000 m2/g et des volumes poreux importants d’environ 1 cm3/g. Par ailleurs, ces matériaux se caractérisaient par un arrangement hexagonal bidimensionnel de leurs pores (CMI-1 et SBA-15) ou cubique tridimensionnel (SBA-16) et dont la taille variait de 2,8 à 9,0 nm, faisant d’eux des candidats idéaux pour l’immobilisation du fluoroionophore. Finalement, les nanosenseurs obtenus par immobilisation de la molécule fluorescente via la méthode d’imprégnation directe se sont montrés performants en termes de sensibilité, sélectivité et temps de réponse.(DOCSC02) -- FUNDP, 201
La question de Dieu chez Husserl dans la genèse de la phénoménologie Les enjeux phénoménologiques de la question théologique
No full textThe question of God in the origins of Husserl's phenomenology (until Ideas in 1913)Les enjeux phénoménologiques de la question théologique dans la genèse de la phénoménologie de Husserl (jusqu'aux Idées directrices... (1913)(DOCFILO00) -- FUNDP, 201
Synthesis of UDP-carbasugars as inhibitors of UDP-GALACTOPYRANOSE MUTASE
No full textTuberculosis, caused by Mycobacterium tuberculosis (TB), one of the most contagious diseases, threatens the world population because of the emergence of pathogenic strains highly resistant to known antibiotics. UDP-Galactopyranose mutase (UGM) is a validated target for the discovery of new therapeutic agents to fight TB. This enzyme can catalyze the interconversion of UDP-Galactopyranose (UDP-Galp) into UDPGalactofuranose (UDP-Galf). The contribution of UGM in the biosynthesis of Galf containing glycoconjugates and its absence in mammals push the community to synthesize novel inhibitors in order to elucidate the modes of action and binding of this enzyme. The design of new mechanistic probes that mimick UDP-Galf or the transition states of this reaction will help to better understand its mechanism and then may allow the development of new drugs to cure TB. The aim of this thesis is to synthesize a series of UDP-carbasugars analogues of UDP-Galf in order to study the mechanism and the binding properties of UGM. These compounds feature a UDP moiety, a galactitol chain for mimicking high-energy intermediates of the enzymatic reaction. All these characteristics are essential for the binding within the active site of UGM. Cyclohexene derivatives could be obtained by ring-closing metathesis from the corresponding diene which would be generated by a multi-step synthesis starting from D-galactose. Two different categories of UDP-Galf analogues have been synthesized using the carbocycle (cyclohexene) as precursor: compounds with a phosphonate moiety or with a phosphate group. From these two scaffolds, a divergent synthesis has been carried out by functionalizing the double bond of the carbocycle. These products have then been coupled with uridine monophosphate to provide the different UDPcarbasugars. The inhibition profile of UDP-carbasugars showed that these compounds are competitive inhibitors of UGM. UDP-cyclohexene and UDP-cyclohexane provides the best inhibition profile of this series due to the hydrophobic character present on the anomeric position of the carbocycle. Interestingly, UDP-polyol phosphates can bind UGM better than UDP-polyol phosphonates due to the presence of an oxygen atom between the anomeric position and the UDP.(DOCSC02) -- FUNDP, 201
ὁ Φωκικὸς πόλεμος. Aux sources de la troisième guerre sacrée.
No full textThe Third Sacred War is a major event in Greek history of the fourth century.
The problem of this conflict is fundamentally a problem of sources. Too often modern historians have been content to offer a linear reconstruction of the facts, modeled on the story of the book XVI of Diodorus Library, without the necessary work of criticism and deconstruction, which is the prerequisite for any true historical synthesis. This study will therefore seek to analyze all available sources (mainly epigraphic and literary) in a new light by applying rigorous historical criticism. The aim is to clarify the chronology of events and highlight the difficulties of the sources treatment.La troisième guerre sacrée est un événement majeur de l'histoire grecque du IVe siècle.
Le problème de cette guerre est fondamentalement un problème de sources. Trop souvent les historiens modernes se sont contentés de proposer une reconstruction linéaire des faits, calquée sur le récit du livre XVI de Diodore de Sicile, en reléguant en annexe le nécessaire travail de critique et de déconstruction qui constitue le préalable indispensable à toute véritable étude historique. Cette étude s'attachera donc à analyser sous un jour nouveau les sources disponibles (principalement épigraphiques et littéraires) en leur appliquant une rigoureuse critique historique. L'objectif est de parvenir à clarifier la chronologie des événements et de mettre en évidence les difficultés inhérentes aux sources et à leur traitement.(DOCFILO02) -- FUNDP, 201
Molecular responses of peripheral blood mononuclear cells in European eel Anguilla anguilla following exposure to xenobiotics. Development of a low invasive multi-biomarker approach using sub-proteomic analysis
No full textSince the beginning of the 1980s, stocks of European eel have been declining in most of their geographical distribution area. Many factors can be attributed to this decline such as pollution by xenobiotics released into the environment through agricultural, industrial and domestic activities. Because the New European Chemicals Legislation (REACh) is asking for alternatives to animal testing and reduction of animals sacrified in ecotoxicology and in accordance with conservation biology considerations, we have developed an appropriate and reproducible methodology to obtain a post-nuclear fraction of isolated European eel peripheral blood mononuclear cells (PBMC) in order to evaluate the toxicity of xenobiotics using a subproteomic approach. In a first study, we have studied the in vitro toxicity of perfluorooctane sulfonate (PFOS) in eel PBMC exposed during 48 h to sublethal concentrations (10 µg and 1 mg PFOS/L). A proteomic analysis using 2D-DIGE was performed to compare PBMC from the control group with cells exposed to the pollutant. A total of 48 proteins displaying significant changes in abundance were identified and categorized according to their functional classes. Besides providing clues on the cellular pathways mainly affected by PFOS, results allowed the identification of proteins rarely found in other ecotoxicological proteomic studies. These proteins could constitute potential biomarkers of exposure to PFOS in fish. In order to determine the specificity of the proteomic pattern observed after in vitro PFOS contaminations, we have completed the set of data with in vitro exposures to two other xenobiotics, dichlorodiphenyl-trichloroethane (DDT) and cadmium, using exactly the same methodologies as for the PFOS experiments. The aim of this new study was the discovery of protein expression signatures specific of different classes of pollutants. The identification of the proteins of interest by mass spectrometry allowed selecting four candidates for a minimal common signature between the three experiments. Moreover, 10 protein biomarker candidates belonging to diverse functional classes have been selected to develop an Integrated Biomarker Proteomic index (IBP). For the first time, the use of star plot graphs has been applied to proteomic data in order to allow visual integration of a set of early warning responses measured with protein biomarkers. IBP values, as well as the areas of star plots, could be used to provide information about global adverse environmental effects as well as about the pollutants involved. Lastly, the in vivo toxicological effects of PFOS on the whole animal have been investigated. For that purpose, the protein expression profiles in PBMC of yellow eels exposed in vivo to environmental PFOS concentrations (28 days of exposure to 1 or 10 µg PFOS/L), as well as after in situ samplings of fish from Belgian rivers displaying different levels of PFOS contamination, have been studied. The comparison of the in vitro, in vivo and in situ results allowed the identification of two proteins in common, plastin-2 and alpha-enolase, whose expression was found to be significantly affected by PFOS. Interestingly, the expression of these two proteins was also modified in gills of European bullhead (Cottus gobio) exposed in vivo to either 0.1 or 1 mg PFOS/L (Dorts et al., 2011), suggesting their potential use as biomarkers of PFOS exposure in fish species. Moreover, the recurrence of the main functional classes of proteins affected by PFOS exposure leads us to think that in vitro exposure of cells to pollutants might be useful in the prediction of the in vivo toxicity of these compounds.(DOCSC03) -- FUNDP, 201
Study of cellular processes affected by lysosomal disorders: importance for mitochondrial morphology and cholesterol homeostasis
No full textLSDs (Lysosomal storage diseases) represent diverse sets of conditions resulting from an impaired uptake, sorting or digestion of the material captured by cells during endocytosis or autophagy. These autosomal recessive diseases can be caused by defects in soluble enzymes, in non-enzymatic lysosomal proteins or even in non-lysosomal proteins, resulting, in fine, to the storage of specific macromolecules inside the organelles of the endo-lysosomal system. Numerous and complex biochemical and signaling cascades have been shown to be activated/altered in response to the original lysosomal disorder and are now known or suspected to play an essential role in the cell dysfunction and death. Such “pathogenic mechanisms” include, for example: alterations of cellular calcium homeostasis and impairment of autophagy, the onset of oxidative stress and inflammation (and autoimmune response), an endoplasmic reticulum stress response as well as changes in the lipid homeostasis and mitochondrial dysfunction. However, even if changes in mitochondrial morphology have been already described in more than ten LSDs, the molecular mechanisms underlying these defects in response to the lysosomal storage and more generally the impact of lysosomal dysfunction on mitochondria remain poorly characterized. The first part of this work has been dedicated to the study of the effect of the TPP-1 (TriPeptidyl-Peptidase-I) deficiency (a lysosomal hydrolase deficient in the LINCL (Late Infantile Neuronal Ceroid Lipofuscinosis)) on the mitochondrial population of human skin fibroblasts. We found that a TPP-1 deficiency induces a fragmentation of the mitochondrial network in these cells, probably caused by a reduction in the abundance of both Mitofusin 1 and Mitofusin 2, two proteins that are essential for the mitochondrial fusion process. Surprisingly, this aberrant mitochondrial morphology is not accompanied by changes either in the matrix calcium concentration or in the abundance of ROS (Reactive Oxygen Species) in basal conditions. In addition, changes in matrix calcium concentration and ROS abundance observed in response to an appropriate stimulus are similar in TPP-1 deficient cells than in cells that recovered TPP-1 activity. We also found that BNIP3 (BCL2/adenovirus E1B 19 kDa protein-Interacting Protein 3), a pro-apoptotic BH3-only protein, is over-expressed in TPP-1 deficient cells. By using a RNA interference approach, we showed that BNIP3 is not involved in the fragmentation of the mitochondrial network in LINCL cells in basal conditions but that this protein can sensitize mitochondria of TPP-1 deficient cells to further mitochondrial fragmentation induced by antimycin A, an inhibitor of the complex III of the mitochondrial respiratory chain, well-known to induce ROS production. These results open the way to further investigation on the role of mitochondrial dysfunction in the pathogenesis of the LINCL. The perturbation of the lipid homeostasis is another characteristic shared by several types of lysosomal disorders. Indeed, a sequestration of cholesterol inside the endo-lysosomal system has been observed in several of these diseases and was shown to lead to the activation of SREBPs (Sterol Regulatory Element-Binding Proteins) transcription factors, key actors in the regulation of lipid metabolism. In the second part of this work, we were interested to determine whether or not this phenomenon could be observed in a sucrose-induced lysosomal storage, a model commonly used to study cell response to lysosomal storage. Indeed, while the relevance of this “sucrosome” model in the study of the effects of a lysosomal storage is widely accepted, the question to know whether it could be relevant to study the molecular mechanisms by which the lysosomal storage triggers broader cellular dysfunctions is still unclear. Here, we showed that the non-esterified cholesterol distribution is modified in 143B cells incubated with sucrose and demonstrated that this aberrant free cholesterol distribution is associated with an increase in the activity of SREBPs. Moreover, we found that the activation of these transcription factors is associated with an increase in the expression of HMG-CoA synthase and mevalonate kinase, the products of two of their target genes, accompanied by an increase in total lipid biosynthesis. Finally, using siRNA interference we demonstrate that SREBP-2 but not SREBP-1a is responsible for the up-regulation of genes encoding these two enzymes. Our results therefore confirmed that the sucrosome model is relevant in the study of the molecular mechanisms and signaling pathways activated in response to a cholesterol sequestration in the endo-lysosomal system resulting from a lysosomal storage, a phenomenon observed in several LSDs. This experimental model, contrary to cell lines derived from LSD patients, presents some assets such as its perfect reversibility when cells are pre-incubated with the invertase but also the possibility to study the putative transitory molecular events occurring at the early onset of the lysosomal overload. Finally, in our research of cellular processes that could be impaired in response of a lysosomal dysfunction, we sought to identify putative other transcription factors and signaling pathways activated in the brain of a mouse model knockout for TPP-1. These experiments allowed us to identify several candidates for which DNA-binding activity seems to be increased in the brain of 120 day-old TPP-1 deficient mice. The majority of them have been described to be involved in the differentiation or the activation of cells of the hematopoietic lineage including the microglial cells and therefore suggest that the TPP-1 deficiency triggers directly (or indirectly) the activation of an inflammatory response in the brain of TPP-1 knockout mice. However, the putative role of these transcription factors and the inflammation in the LINCL pathogenesis remains to be determined(DOCSC03) -- FUNDP, 201
Essays on the direct and indirect impacts of microfinance
No full textFinancial deepening, especially through the microfinance revolution, has been one of the boldest and most promising global evolutions over the last decades. My thesis aims at building up the knowledge about the direct and indirect impacts of finance at the micro level, and especially about the mechanisms and welfare implications thereof. My thesis consists of three chapters.
The first one focuses on the potential spillover effects that the entry of microfinance institutions can generate at the level of local informal credit markets. Using a standard model of lending in presence of adverse selection, I show that MFIs can trigger an increase in the equilibrium interest rate of the informal market. Using data from Indian villages, I provide supporting evidence fro the main predictions of the model.
The second chapter investigates the impact of microfinance participation in India on educational outcomes. It is based on a unique long-term panel database on members of informal credit and saving associations, known as SHGs, in villages of Jharkhand, India, in which households were interviewed every two years between 2002 and 2009. Combining panel and propensity-score matching techniques, we find that members of SHGs are significantly more likely to enroll their children in school. However, the treatment effects take time to materialize (about five years on average) and are essentially concentrated on girls.
The final chapter looks at the insurance aspect of SHGs. Using the same database as in chapter 2 combined with meteorological data, I study the extent and the nature of the reaction to rainfall shocks of rural households with and without access to microcredit. I find that member households enjoy a stable access to credit, opening the possibility of short-term consumption smoothing following an adverse rain shock.(DOCSESG00) -- FUNDP, 201