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Effects of dietary N-3 and N-6 polyunsaturated fatty acids on the lipid metabolism and on reproductive physiology and performances of eurasian perch breeders (perca fluviatilis)
No full textControl of good quality eggs and larvae takes into account the influence of some factors such as temperature, photoperiod, nutrition, stocking conditions,… Up to now, in Percid fishes, it has been demonstrated that gamete quality of captive breeders constitutes one of the principal limiting factor in the production of these species, even more when fish are fed with an artificial dry diet. It has been demonstrated that the dietary fatty acid content might affect the physiology of breeders and their reproductive performances.
Therefore, the general objective of the thesis was to understand the mecanisms implicated in the preferential utilization of dietary fatty acids in relation to changes in lipid metabolism, as well as to endocrine changes linked to maturation observed during a reproductive cycle in Percid females, with Eurasian perch as biological model. Indicators of sperm quality were also investigated.
We have studied the impact of polyunsaturated fatty acids on the physiology of reproduction, both in vivo and in vitro. The results showed that AA, via its conversion to PGE2 and PGF2 alpha, may have a stimulating role in the oocyte maturation, by enhancing some maturation-inducing steroids, such as the maturational hormone. As observed in mammals, we concluded that the cAMP production in response to PGE2 was probably mediated by an intracellular mechanism via the EP2 receptor. Nevertheless, in our study, the production of PGE2 and PGF2 alpha was conditioned by the EPA/AA ratio in fish tissues, which is dependent upon the EPA/AA ratio found in the diet. Vitellogenin production was also depending on the EPA/AA ratio, with values fluctuating in a similar manner to what was obtained with prostaglandins, just before the spawning season. Sperm and eggs fatty acid compositions were dependent on the fatty acid content of broodstock diet, while indicators of sperm quality were all good in fish fed diets with a high or low DHA/EPA/AA ratio, and egg and larval quality were both affected by the diet given to breeders. So it can be concluded that female gamete quality was more sensitive to the dietary DHA/EPA/AA ratio than the male one. A study of fertilizing ability should be conducted to definitely confirm this statement.
A dietary imbalance of highly unsaturated fatty acid is certainly responsible for the lower egg and larval quality observed for some diets. Indeed, reproductive performances were characterised by lower spawning, fertilizing and hatching rates for fish fed a high EPA/AA ratio compared to a ratio of 1, and larval resistance after an osmotic stress was also lower. In all the experiments, the relative levels of AA and DHA were maintained in eggs, whatever the tested diet, except in eggs of fish fed a commercial food for salmonids (DHA/EPA/AA : 14/16/1). This diet provided the lowest egg and larval quality, with only 26% fertilization rate, 15% hatching rate and 100% of larval mortality at the end of the osmotic stress. This suggests that AA and DHA present in eggs conditioned the correct hatching and fertilization rates, and also the larval survival. The essential fatty acid requirement from the n-3 series for Eurasian perch breeders is 18:3 n-3, since perch is clearly able to elongate and desaturate 18:3 n-3 into HUFA, while for the n-6 series, AA is definitely required. Providing 18:2 n-6 as the only source of n-6 PUFA is not sufficient since it has been shown that AA is particularly needed during maturation and spawning due to its important role as eicosanoids precursor.
All in all, it can be hypothesized that the best dietary DHA/EPA/AA ratio tested is 2/1/1 for Eurasian perch breeders in order to obtain good egg and larval quality.(DOCSC03) -- FUNDP, 200
Algorithms and software for multilevel nonlinear optimization
No full textThis research concerns the algorithmic study of multilevel nonlinear optimization
problems. We have developped during our thesis new methods to solve this type of problems
and we analyze their convergence and numerical results. We have also implemented a soft-
ware for which a complete description is given in this manuscript. A library of test problems
has also been constructed on which we have tested our software. The numerical results ob-
tained show that our method is clearly the best for this class of problems. The software also
allowed the solution of a progressive lens industrial application that had never been solved
by existing methods.Cette recherche concerne l’étude algorithmique des problèmes d’optimisation non-
linéaire multi-niveaux. Nous avons développé au cours de cette thèse de nouvelles méthodes
pour la résolution de ce type de problèmes et nous analysons leur convergence et résultats
numériques. Nous avons également implémenté un logiciel pour lequel une description com-
plète est donnée dans ce manuscrit. Une librairie de problèmes tests a également été constru-
ite sur laquelle nous avons pu tester notre logiciel. Les résultats obtenus montrent clairement
que notre méthode est la meilleure pour cette classe de problèmes. Le logiciel a également
permis la résolution d’une application industrielle de verres progressifs qui n’avaient pu être
résolue par les méthodes existantes.(DOCSC00 ) -- FUNDP, 200
Biomarkers in black tiger shrimp (Penaeus monodon)exposed to antibiotics and pesticides
No full textIn Vietnam, the growth of black tiger shrimp (Penaeus monodon) aquaculture, has resulted from the expansion of farming areas, adoption of new culture techniques and enhanced level of intensification. The use of pesticides and antibiotics in shrimp farming has increased to prevent and to treat disease. These compounds pose a potential threat to shrimp health, product quality and, ultimately, consumers'health. The present study aimed to assess the effects of the most commonly used antibiotics and pesticides on biomarker responses in black tiger shrimp in order to develop a useful set of biomarkers to assess the health/stress status of shrimp and product safety.
In order to fully investigate the utility of such a comprehensive set of biomarkers, their performance in laboratory and field situations was tested. In laboratory conditions, shrimp were fed with medicated feed containing 4g enrofloxacin (quinolone) or furazolidone (nitrofuran)/kg for 7 days, or exposed to three nominal concentrations of endosulfan (0, 0.01, 0.1, 1 µg/L) or deltamethrin (0, 0.001, 0.01, 0.1 µg/L) for 4 days. After treatment, shrimp were decontaminated during 7 days. Results showed that antibiotics cause very small changes in the oxidative stress status of shrimp. In contrast, lipid peroxidation level (LPO) may be a potential discriminating biomarker to assess the stress level in farmed shrimp. Results also showed that 4 days exposure to 0.1 µg/L deltamethrin significantly (p<0.05) increased LPO in gills. However, none pesticide treatment had a significant effect on the activities of antioxidant enzymes such as catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST). In addition, acetylcholinesterase activity (AChE) can indicate the health status of cultured shrimp exposed to those commonly used pesticides and antibiotics. Muscle AChE activity should be assessed to point out endosulfan or deltamethrin exposure, whereas gill AChE activity impairment could indicate exposure to furazolidone.
The interpretation of biomarker data is challenging because natural variation of environmental factors likely influences enzyme activities. A combination of three temperatures (24, 29 and 34oC), two salinities (15 and 25ppt) and the absence or presence of 0.1µg/L deltamethrin was applied on shrimp during 4 days. LPO suggested that shrimp may not be susceptible to this form of oxidative damage by deltamethrin. While, AChE in muscle was strongly inhibited by deltamethrin at all tested temperatures and salinities, indicating that AChE activity could be the most appropriate tested biomarker of deltamethrin exposure. Moreover, due to strong interactions between deltamethrin exposure and temperature and/or salinity, mostly on GPx, tGSH and CAT, those biomarkers are less suitable for pesticides exposure monitoring in the field.
It is also important to carry out field studies in order to examine how abiotic and biotic factors can modify the biomarker responses to toxicants relative to those seen in laboratory conditions, where these factors are controlled. In field conditions, for which two different culture systems were distinguished (intensive and improved extensive), enrofloxacin medication caused very small changes in oxidative stress status. However, the type of culture system has a significant impact on basal oxidative stress level. It is concluded that LPO in gills and hepatopancreas, CAT, GPx, GST in gills, and AChE in muscle could be used as biomarkers of general health status and can discriminate between shrimp cultivated in different culture systems. Finally, another part of this study examines the advantages of the use of biomarkers as an early warning system by applying it to different shrimp farming systems. Shrimp sampled from intensive, or converted from rice paddy to intensive shrimp farming or rice shrimp integrated farming are suffering from an oxidative stress in all studied tissues.
The present study provides evidence that integrating a set of biomarkers to define the health status of shrimp in different shrimp culture systems can be useful. Our results could be used as a reference to undertake future research aiming to assess the health of shrimp exposed to xenobiotics. Moreover, the set of biomarkers needs further research. These tools can be used for screening and for diagnosis, in trend analyses or for predictive purposes, including risk assessment.(DOCSC03)--FUNDP, 200
Essays in the economics of the retirement decision-making
No full textLiving longer and in a better health condition should be seen as a chance. However, the increase in the life expectancy is often presented as a source of concern. Indeed, combined with the decline in the fertility rate, the increase in the life expectancy gives rise to the aging of the population that represents one of the main challenges of the twenty-first century since it will put the financial health of the Welfare State under pressure in many countries. Moreover, living longer requires more income and particularly more retirement income. Consequently, citizens of those countries will have probably to rely more on themselves than in the past to get this income. Therefore, it is essential that the young generations are able to make plans for the future in order to have enough resources during their retirement. However, the elaboration of these plans poses two issues. First, the young generations should have all the necessary information to build these plans. Second, once these plans are built, the young generations have to follow them. In this regard, the economic literature provides some upsetting evidence. First, some empirical studies show that the discount rate is not constant over time but is higher for short horizons than for long horizons (e.g. Thaler (1982)). These studies suggest that the discount function would be (quasi-)hyperbolic and not exponential as it is generally assumed in the literature dealing with intertemporal choices. When a person displays a quasi-hyperbolic discount function, it means that this person is too optimistic concerning her future behaviours what can lead her to make time-inconsistent choices due to self-control problems. Second, several studies show a lack of knowledge about pension and Social Security benefits among the population of some countries (e.g. Gustman and Steinmeier (2001)). In conclusion, this evidence suggests that the required information to make plans for the future is not widespread among the population and that people do not follow these plans once they are build because of self-control problems. Therefore, the misperception of the retirement income and quasi-hyperbolic discounting are two factors that could affect the standard of living of the elderly.
This thesis is a collection of five independent chapters addressing these issues.
Chapter 1 is a short note describing hyperbolic and quasi-hyperbolic discounting.
Chapter 2 examines how quasi-hyperbolic discounting influences the retirement decision with respect to exponential discounting. In a 3-period model in which a person has to decide to work or to retire in period 2, we investigate whether quasi-hyperbolic discounting leads to early or later retirement compared with exponential discounting. With respect to exponential discounting, quasi-hyperbolic discounting implies that the agent cares relatively more about the remote future than about the near future. For the young generation, retiring later implies to incur a higher effort cost that takes place in the near future to benefit from a higher income that partially takes place in the remote future. Thus, quasi-hyperbolic discounting induces the young generation to plan to retire later. On the other hand, for the middle-aged generation, retiring later implies to incur an effort cost now to benefit from a higher income in the near future. That is why quasi-hyperbolic discounting induces the middle-aged generation to retire earlier than planned. Therefore, a person who displays a quasi-hyperbolic discount function may retire later or earlier than a person who displays an exponential discount function. However, the impact of quasi-hyperbolic discounting on the retirement decision depends on the degree of awareness of the potential self-control problem and on the tools available to deal with it. In this regard, if the person perceives the potential self-control problem and if she is able to commit her future retirement choice, quasi-hyperbolic discounting leads to later retirement with respect to exponential discounting. On the contrary, if she does not perceive the potential self-control problem or if she is unable to commit her retirement choice, the impact of quasi-hyperbolic discounting on the retirement decision is indeterminate. In conclusion, the retirement decision depends effectively on the discount function we consider and quasi-hyperbolic discounting, even if it does not provide a general explanation for early retirement, may explain, in some cases, this phenomenon.
Chapter 3 provides a deep analysis on how quasi-hyperbolic discounting affects the retirement decision. This chapter investigates how the bias for the present that is inherent to quasi-hyperbolic discounting influences the retirement choice. As in Salanié and Treich (2006), the two impacts of the present bias, i.e. the self-control effect and the discounting effect, are considered. Contrary to Chapter 2, we consider that the workers can retire at any age. We show that the self-control effect leads to early retirement while the discounting effect leads to later retirement. Indeed, if the person cares less about the future, she saves less what induces her to retire later. On the contrary, her lack of self-control induces her to retire earlier than expected. The global impact of the bias for the present on the retirement decision is therefore indeterminate. Nevertheless, if a person is able to commit her retirement choice, she avoids early retirement since the self-control effect does not play. However, we show that perceiving the potential self-control problem is not sufficient to attenuate early retirement.
The literature on quasi-hyperbolic discounting generally considers that a person who perceives the potential self-control problem tries to commit her future choices or determines her current actions by taking into account her effective future reactions to these actions (Strotz (1956)). Cremer et al. (2007) and Bassi (2008) show that is also possible to design a public transfer scheme through majority voting in order to deal with self-control problems. Following this idea, Chapter 4 shows how a Pay-As-You-Go (PAYG) pension can emerge in order to solve the self-control problem regarding the retirement decision. If an agent perceives the potential self-control problem but if a commitment technology is not available, he can make a time-consistent retirement choice by contributing to a PAYG pension system in which the contributions made are lost in the case of early retirement. Therefore, a PAYG pension system can emerge even if it is a dominated saving device since contributing to such a pension system can be a way to constraint the future retirement choice by increasing the cost of early retirement. This chapter identifies the conditions under which such equilibrium arises and compares this voting equilibrium to the one emerging in an economy populated by agents who do not perceive the potential self-control problem.
Finally, several studies show a lack of knowledge about pension and Social Security benefits among the population in many countries. However, other studies show that the knowledge of these benefits become more precise for people close to their retirement what suggests that a progressive learning process is at work (e.g. Rohwedder and Kleinjans (2006)). While this lack of knowledge should have sizeable effects on the consumption level during the retirement and on the retirement age, empirical studies find that this misperception has a low impact on the retirement decision and on the consumption level during retirement (e.g. Gustman and Steinmeier (2001), Rohwedder and van Soest (2006)). Chapter 5 investigates the theoretical implications of this misperception of the pension benefit and this progressive learning on the retirement and consumption decisions. The main result is that the impact of the misperception on these outcomes may be ambiguous if only two retirement ages are possible. This could rationalize why empirical studies only find a limited impact of the misperception of the retirement benefit on these outcomes. In addition, this misperception may explain simultaneously early retirement and the Retirement-Consumption Puzzle, i.e. the unexplained downward shift in the consumption path around the retirement age.(DOCSESG00)--FUNDP, 200
Le flagelle de Brucella melitensis : caractérisation de la structure et de la régulation flagellaire
No full textThe bacterial flagellum is a rotative filamentous appendage which is anchored in the bacterial membranes and allows the bacterium to move. Besides its main locomotive function, the bacterial flagellum fulfills other functions such as adhesion and secretion. The filament, which comprises most of the flagellum structure, is formed by an assembly of proteins called flagellins. It is estimated that nearly 80% of the bacteria produce a flagellum. Brucella is a mammal pathogens bacterium that had long been designated as non-flagellated. However, recent discoveries have shown that all flagellar genes were present in its genome and were necessary to Brucella’s pathogenic ability. Several regulators that control the production of flagellar proteins have also been uncovered. However, no flagellum was viewed on Brucella until today.
In this work, we showed for the first time through the optical and electron microscopy that B. melitensis produces transitionally a polar sheathed flagellum. On the other hand, we also investigated the regulation of flagellar system. Firstly, we studied the role of sigma factor RpoE1 on flagellar genes. The rpoE1 mutant overexpresses flagellar genes and produces a longer flagellum. Secondly, we showed that the production of flagellin was controlled by specific regulators named FlbT and FlaF. FlbT is a flagellin activator while FlaF is a flagellin inhibitor. In addition, we showed that the function of FlbT appears to be conserved among the Rizhobiales. We also showed that B. melitensis is more virulent in the absence of flagellin, which indicates a specific role of flagellin. The function of the flagellin of Brucella remains to be investigated.
Finally, a preliminary in silico analysis of the genome of Brucella has enabled us to target other potential regulators of the flagellar system. The data gathered during this work have allowed us to draw a hierarchical regulatory cascade of flagellar genes of Brucella in 3 classes.Le flagelle bactérien est un appendice rotatoire filamenteux ancré dans les membranes bactériennes et permet à la bactérie de se mouvoir. Bien que le rôle locomoteur soit principal, d’autres rôles lui sont attribués comme l’adhérence et la sécrétion. Le filament compose la plus grande partie du flagelle. Celui-ci est formé par un assemblage de protéines appellées flagellines. On estime que près de 80% des bactéries produisent un flagelle. Brucella est une bactérie pathogène de mammifères qui a longtemps été désignée comme non-flagellée. Cependant, les récentes découvertes ont montré que tous les gènes flagellaires étaient présents dans son génome et qu’ils étaient nécessaires lors de l’infection. Plusieurs régulateurs qui contrôlent la production des protéines flagellaires ont également été mis au jour. Néanmoins, aucun flagelle n’avait encore été visualisé chez Brucella.
Lors de ce travail, nous avons montré pour la première fois grâce à la microscopie optique et électronique que B. melitensis produit de manière transitoire un flagelle polaire de type gainé. D’autre part, nous avons aussi investigué la régulation du système flagellaire. Premièrement, nous avons étudié le rôle du facteur sigma RpoE1 sur les gènes flagellaires. Le mutant rpoE1 surexprime les gènes flagellaires et produit des flagelles plus longs. Deuxiemement, nous avons montré que la production de la flagelline était controlée par des régulateurs spécifiques nommés FlbT et FlaF. FlbT est un activateur de la production de la flagelline alors que FlaF est un inhibiteur. De plus, nous avons montré que la fonction de FlbT semble conservée parmi les Rizhobiales. Nous avons également montré que B. melitensis était plus virulente en absence de flagelline, ce qui montre un rôle spécifique de la flagelline qui reste à être investigué.
Pour terminer, une analyse préliminaire in silico du gènome de Brucella nous a permis de cibler d’autres régulateurs potentiels du système flagellaire. Les données récoltées lors de ce travail nous ont permis de dessiner un schéma de régulation hiérarchique des gènes flagellaires de Brucella en 3 classes.(DOCSC03 ) -- FUNDP, 200
Alimentation et Nutrition des juvéniles de Heterotis niloticus (Arapaimidae, Teleostei). Premières estimations des besoins nutritionnels et valorisation des sous-produits végétaux
No full textHeterotis niloticus is an African species with a great potential for fish farming as a result of its remarkably rapid growth, air-breathing characteristic, omnivorous diet, good meat quality and relative high commercial value. However, its use for aquaculture is limited due to the difficulty in the massive production of fingerlings and the lack of knowledge on its artificial feeding. Therefore, the estimations of its nutritional requirements at different ontogenetic stages are necessary in view of its effective contribution to the aquaculture production in Cameroon and other African countries. The present research aims to establish some basic nutritional variables relative to its fingerlings rearing and to examine the suitability of plant oil cakes as a partial substitute of fish meal in its compounded diets.
Between May 2005 and August 2008, several experiments were conducted in rectangular hapas (0.5 m3 useful capacity) placed in two earthen pond (300 and 600 m²) at the Melen Aquaculture Station (Yaounde, Cameroon). Replicate groups of juveniles were handfed twice daily to apparent satiation all the time. Analyses were performed at the laboratory of the Research Unit in Organismal Biology (University of Namur, Belgium) and the Unit of Industrial Chemistry Biology (Gembloux Agricultural University, Belgium).
On the protein and amino acids requirements, the results revealed that the dietary protein requirements are 310 and 345 g protein per kg diet for optimal and maximal growth, respectively for fish size ranging from 3 to 62 g. Based on whole body or muscle tissue indispensable amino acids to A/E ratios, its IAA requirement profile is similar to those of other omnivorous tropical fish species with the exception of tryptophan and histidine.
The dietary protein-sparing effect has been clearly demonstrated when the dietary energy of lipid increases from 17 to 19.6 kJ g-1 at 28% crude protein. Therefore, this result indicates that the optimum protein and lipid levels in its diet are 280 and 130 g kg-1 diet, respectively. Finally, the soybean and cottonseed oilcakes meals could partially replace up to 50% the dietary fish meal in its practical fingerlings diets without negative effect on maximal growth. This study contributes to improve our knowledge on basic nutrients requirements for the juveniles of a new aquaculture species for Africa.
However, massive production of quality fingerlings of this species remains a major obstacle to overcome on the road of the domestication of H. Niloticus for aquaculture use. Our work reveals that even with that constraint, optimism is permitted for a sustainable and rentable culture of this species in sub-Saharan Africa.L'Arapaimidae Heterotis niloticus est une espèce africaine à fort potentiel aquacole en raison de sa forte croissance, sa double respiration, la bonne qualité gustative et ferme de sa chair, et sa relative haute valeur commerciale. Toutefois, son utilisation à des fins piscicoles est limitée par la difficulté d'approvisionnement en alevins de qualité et par l'absence de connaissances sur ses besoins nutritionnels indispensables à l'optimisation de formules alimentaires pour l'espèce. En vue de sa contribution efficace dans l'augmentation de la production aquacole du Cameroun et des autres pays africains, la détermination entre autres de ses besoins alimentaires et nutritionnels à divers stades ontogénétiques s'avère nécessaire et incontournable. La présente recherche, inscrite dans cette perspective de domestication plus avancée de l'Heterotis du Nil, s'est proposée d'établir certaines variables nutritionnelles de base relatives à son pré-grossissement et d'évaluer ses capacités de valorisation des sous-produits oléagineux.
Entre mai 2005 et août 2008, une série d'expériences en triplicat sur la nutrition des juvéniles de H. niloticus ont été réalisées dans des hapas (0,5 m3 de volume en eau) installés en étangs de dérivation (300-600 m²) à la station aquacole de Melen (Yaoundé, Cameroun). Les analyses ont été effectuées au sein de l'Unité de Recherche en Biologie des Organismes des Facultés Universitaires Notre-Dame de la Paix (Namur, Belgique) et de l'Unité de Chimie Biologique Industrielle de la Faculté Universitaire des
Sciences Agronomiques (Gembloux, Belgique).
Sur le plan protéique, les résultats ont révélé que cette espèce nécessite 310 et 345 g protéines kg-1 d'aliment respectivement pour la croissance optimale et maximale des sujets pesant entre 3 et 62 g et que ses besoins spécifiques en acides aminés indispensables, excepté pour le tryptophane et l'histidine, sont similaires à ceux d'autres poissons tropicaux omnivores. Ensuite, le phénomène d'épargne des protéines par les lipides alimentaires a été clairement mis en évidence lorsque l'énergie a été augmentée de 17 à 19,6 MJ kg-1 d'aliment contenant 28% de protéines, ce qui nous a permis de suggérer que les besoins protéiques des juvéniles de H. niloticus peuvent être réduits de 310 à 280 g protéines kg-1 d'aliment dans les conditions expérimentales de notre étude. Enfin, la dernière approche de notre investigation a montré que les tourteaux de soja et de coton peuvent remplacer jusqu'à hauteur de 50% la farine de poisson dans l'alimentation des juvéniles de cette espèce. Ces différents acquis constituent en soi une avancée certaine dans la connaissance des besoins nutritionnels et alimentaires des Heterotis.
Le parcours de la domestication de cette espèce reste néanmoins encore difficile, notamment avec l'épineux problème de la production massive de juvéniles de qualité. Les perspectives de recherche-développement envisagées au terme de cette thèse laissent entrevoir de réelles chances de surmonter cet autre handicap-clé. Nous restons donc optimistes quant à l'élevage durable et rentable de ce poisson en Afrique sub-saharienne.(DOCSC03)--FUNDP, 200
La coordination en situation d'urgence : une approche située
No full textIn this research we analyse collective work in emergency situations. We use a qualitative methodology developed for emergency exercises analysis. The methodology is a collaborative one, involving a team of specialized observers. Each of them collects video data in one of the different “sites” involved (e.g. field, the crisis center(s), expert cells, …) or on one crisis management activity. Using a situated approach, the methodology gives us the opportunity to better understand the individual and organizational dynamics of crisis management organisations.
The data analysis highlights different tensions in emergency organizations. Moreover, we identify levers which enable actors to manage these tensions. These levers are part of the articulation work and are found in three central dimensions : structures, interactions, and sensemaking.L'objectif de la thèse est d'analyser le fonctionnement collectif en situation d'urgence. Sur base de données récoltées dans le cadre d’exercices d’urgence de grande ampleur, l'idée est de parvenir à éclairer les différentes dimensions psychosociales et organisationnelles qui sous-tendent la coordination entre acteurs. La problématique s’est construite sur base de deux constats, à l’issue de l’étude de la littérature sur la gestion des crises, et en particulier la coordination en situation d’urgence. D’une part, le concept de coordination, régulièrement cité comme fondamental dans la compréhension des situations critiques, n'est pas analysé en profondeur. D’autre part, les études existantes, souvent menées a posteriori (sur base de récits d’accidents par les acteurs), ne permettent pas de comprendre les phénomènes à l’œuvre dans ces situations. Les récits reconstruits a posteriori par les acteurs, et les phénomènes individuels et collectifs dont ils ne sont eux-mêmes pas conscients, sont des incitants à mener des observations « in situ ».
Le projet utilise une méthode de collecte de données originale, impliquant plusieurs chercheurs, et basée sur la collecte d’enregistrements vidéo dans les différents sites impliqués lors des exercices d’urgence. Cette démarche permet par conséquent d’aboutir, lors de l’analyse des données, à la fois à une vue d’ensemble et à un enregistrement détaillé des interactions entre acteurs et sites impliqués.
La coordination en situation d’urgence est étudiée sous ses différents aspects : en coprésence et à distance ; au sein d’une même organisation et entre deux ou plusieurs organisations.
La thèse poursuit plusieurs objectifs :
• Un objectif d’ordre théorique, en intégrant la littérature sur la coordination dans les théories des organisations et dans les approches centrées sur les situations d’urgence et de crise
• Un objectif méthodologique, en utilisant une méthode située et collaborative de récolte de données audiovisuelles sur des exercices d’urgence de grande ampleur. Ces données audiovisuelles ont l’avantage de nous permettre d’accéder à l’aspect multimodal des interactions. Notre matériau est constitué de 11 exercices, organisés en France et en Belgique, qui représentent environ 150 heures d’enregistrements.
• Un objectif d’élaboration théorique à partir de l’analyse des données :
Les situations d’urgence sont considérées comme des situations en équilibre instable à plusieurs niveaux : au niveau de la structure, des tâches mais aussi des interactions et du sens. L’objectif de l’analyse des données est de mettre en évidence les mécanismes structurants dans les situations d’urgence à ces différents niveaux. L’objectif est également d’observer dans quel contexte ces mécanismes émergent. L'analyse utilise le concept de travail d'articulation pour détecter les modalités qui permettent à la coordination d'avoir lieu. Le résultat de l'analyse permet par ailleurs d'identifier les différentes tensions inhérentes à l'activité collective dans l'urgence, et les leviers qui permettent aux acteurs de gérer ces tensions
• Un objectif d’élaboration méthodologique à partir de l’expérience de terrain :
Nous avons constaté de graves lacunes sur le terrain en matière d’observation des exercices. Les acteurs qui sont préposés à l’observation des exercices ne possèdent bien souvent aucune autre directive que celle de vérifier les écarts par rapport au plan. Il existe un besoin en matière de construction d’une grille d’observation et d’analyse des exercices d’urgence. Les différentes modalités du travail d’articulation aux différents niveaux permettront d’élaborer une grille d’analyse/grille de lecture des exercices d’urgence. Cette grille pourra faire l’objet d’une réappropriation par les acteurs de terrain.(DOCSESG00) -- FUNDP, 200
Multilevel optimization in infinity norm and associated stopping criteria. Optimisation multiniveaux en norme infinie et critères d'arrêt associés.
No full textThis thesis presentation concerns the study of a multilevel trust-region algorithm in infinity norm, designed for the solution of nonlinear optimization problems of high size, possibly submitted to bound-constraints. The multilevel algorithm that we study has been developed on the basis of the algorithm created by Gratton, Sartenaer and Toint (2008). In this work, we look at both theoretical and numerical properties of the new algorithm. In a first part, the main features of the new algorithm are exposed. We then look at several stopping criteria for nonlinear bound-constrained optimization algorithms. In particular we define stopping criteria that are meaningful in terms of backward error analysis. We finally compare numerically our method to competing algorithms in the same field in order to show its remarkable efficiency.Cette thèse se concentre sur l'étude d'un algorithme multiniveaux de régions de confiance en norme infinie, conçu pour la résolution de problèmes d'optimisation non-linéaires de grande taille pouvant être soumis à des contraintes de bornes. L'étude est réalisée tant sur le plan théorique que numérique. Dans un premier temps, les spécificités du nouvel algorithme sont exposées et discutées. Par la suite, nous étudions différents critères d'arrêt pour les algorithmes d'optimisation avec contraintes de bornes. En particulier, les critères d'arrêts sont analysés en termes d'erreur inverse (backward erreur). Enfin, la méthode est comparée numériquement à certains algorithmes concurrents du domaine dans le but de montrer sa remarquable efficacité.(-) -- FUNDP, 200
Caractérisation de la différenciation alternative de kératinocytes humains induite par des expositions répétées aux UVB et étude fonctionnelle de TRIM29, une protéine impliquée dans la survie cellulaire
No full textExposures to ultaviolet radiations (UV) is one of the most dangerous stresses to which human
skin is exposed daily. Keratinocytes, the main cell type of the epidermis, constitue our first
line of defense against UV. UVB are highly mutagenic and are the most deleterious
component of sunlight reaching earth surface.
We developed an original model of eight repeated sublethal exposures of human keratinocytes
lacking p16INK-4a and expressing human telomerase (hTERT), while retaining other growth
controls and the ability to fully differentiate in vitro in a reconstructed epidermis. While
premature senescence can occur in primary keratinocytes after exposure to a single dose of
UVB, we did not observe any significant increase of the proportion of senescence-associated
beta-galactosidase activity positive cells following UVB exposure in this cell line in contrast to
primary keratinocytes. This suggested a role for p16INK-4a in UVB-induced senescence. We
detected severe oxidative stress, sustained DNA damage, prolonged cell cycle arrest, and
induction of markers of epidermal differentiation suggesting an alternative differentiation. In
vivo, keratinocyte differentiation is an important mechanism of defense against UVB.
In order to characterize this phenotype, a proteomic profiling with fluorescent twodimensional
difference in-gel electrophoresis (2D-DIGE) at 16, 40 and 64 h after repeated
exposures to UVB allowed to identify 69 differentially abundant protein species. Among
these protein species, Capping-protein Gelsolin-like protein (CapG), TRIparite Motif Protein
29 (TRIM29) and several phosphorylated cytokeratins had never been previously involved in
the response of keratinocytes to UVB. Increased abundance of capping-protein Gelsolin-like
protein was mostly localized on cell edges suggesting its participation in morphological
changes through modulation of the actin cytoskeleton. Keratin 8 was phosphorylated on two
sites as previously analysed in association with stress. Invalidation of TRIM29 in
keratinocytes favored apoptosis after UVB exposure and also in reconstructed epidermis,
suggesting a role in a cell survival pathway. Analysis with chemical inhibitors suggested that
the increased abundance of TRIM29 was a PKC-dependent process.
This work allows a better understanding of specific mechanisms of the defense of
keratinocytes repeatedly exposed to UVB particularly through an alternative differentiation
process. Furthermore, we revealed that TRIM29 is involved in the cell survival of
keratinocytes exposed to UVB.L'exposition aux rayonnements ultraviolets (UV) constitue un des stress quotidiens les plus
importants auxquels est confrontée la peau. Les kératinocytes, type cellulaire majoritaire de
l'épiderme, constituent donc notre première ligne de défense contre les UV. Les UVB sont de
puissants mutagènes et sont considérés comme les rayonnements du spectre solaire les plus
dangereux.
La première partie de ce travail visait à étudier la réponse de kératinocytes humains exposés
de façon répétée aux UVB. Un modèle original basé sur huit expositions à une dose sublétale
d'UVB a été mis au point sur une lignée de kératinocytes humains. Ces kératinocytes (NhTERT)
sont immortalisés par l'expression ectopique de la sous-unité catalytique de la
télomérase et n'expriment pas la protéine p16INK4a, un inhibiteur du cycle cellulaire. Ces
kératinocytes conservent néanmoins le contrôle du cycle cellulaire et sont capables de se
différencier normalement in vitro. L'exposition de façon répétée aux UVB de ces
kératinocytes provoque un stress oxydatif sévère et des dommages persistants à l'ADN,
menant à un arrêt du cycle cellulaire, et un étalement morphologique. Après exposition aux
UVB, les kératinocytes N-hTERT ne possèdent pas d'activité beta-galactosidase associée à la
sénescence alors que cette activité est détectée chez les kératinocytes normaux, suggérant que
la protéine p16INK4a joue un rôle essentiel dans la sénescence induite prématurément par les
UVB. Par contre, plusieurs marqueurs de la différenciation des kératinocytes sont induits
après les expositions des cellules N-hTERT, suggérant plutôt un phénotype de différenciation
alternative. In vivo, la différenciation est un mécanisme majeur de défense des kératinocytes
exposés aux UVB.
Nous avons ensuite caractérisé ce modèle par une étude protéomique à l'aide de la technique
du 2D-DIGE. Nous avons mis en évidence 69 protéines dont l'abondance varie suite aux
expositions aux UVB à 16, 40 et 64 h après la dernière exposition. Parmi ces protéines, CapG
(Capping-protein Gelsolin-like protein), TRIM29 (TRIparite Motif Protein 29) et la kératine 8
n'avaient jamais été impliquées dans la réponse des kératinocytes exposés aux UVB. CapG,
une protéine de la famille des gelsolines, est localisée à la périphérie cellulaire chez les
cellules exposées aux UVB suggérant un rôle dans la morphologie étalée par modification du
cytosquelette d'actine. La kératine 8 est phosphorylée sur deux sites associés à un état de
stress. Enfin, nous avons étudié l'effet de l'invalidation de la protéine TRIM29 sur les
kératinocytes N-hTERT exposés aux UVB. Nous avons montré que TRIM29 joue un rôle
important dans la survie des kératinocytes exposés aux UVB, et cela également sur des
épidermes reconstitués exposés aux UVB. En parallèle, nous avons tenté de déterminer, à
l'aide d'inhibiteurs chimiques, quelle voie de signalisation était impliquée dans l'induction de
TRIM29 suite aux expositions aux UVB. Il semble que l'augmentation d'abondance de
TRIM29 suite aux expositions aux UVB soit dépendante de la voie des protéines kinases C.
Ce travail a permis de mieux comprendre les mécanismes de défense spécifiques des
kératinocytes exposés aux UVB les menant à une différentiation alternative. De plus, nous
avons mis en évidence la protéine TRIM29 qui favorise la survie des kératinocytes exposés
aux UVB.(DOCSC03) -- FUNDP, 200
Improvement of in vitro methods to study nanoparticles toxicology Application to gold and cobalt nanoparticles
No full textNanotechnology represents a new emerging field in different applications that involves the development, manufacturing of materials in the sub micron range down to the nanometers (nm) range scale. These new materials will soon be able to improve our everyday life and the advantages can be considered enormous and, in the near future, the development of nanotechnologies is expected to have a large socio-economical impact in practically all industrial activity fields. Anyway, the potential risk of these nanomaterials for human health and environment is not clear and remains largely unknown. This work aims to propose, develop and demonstrate the possible use of in vitro methods and systems in order to better understand the toxicology of nanoparticles (NPs) that is a research field in which an integrated approach based on the use of different techniques (e.g. to assess physicochemical characterization of NPs) is required. In particular, four in vitro models were taken into consideration in this study: (i) Balb/3T3 immortalised mouse fibroblasts; (ii) Peripheral Blood Mononuclear Cells (PBMC); (iii) Madin-Darby canine kidney epithelial cells (MDCK cells) and (iv) Human hepatoma cells (HepG2 cells). Considering different in vitro toxicological end-points, the use of in vitro methods was demonstrated to possibly explain some of the effects of Cobalt NPs (Co-nano) and Gold NPs (AuNPs). In particular, standard in vitro tests as well as original newly developed methods were used to assess the cell viability as end point of basal cytotoxicity; morphological transformation for carcinogenic potential; single strand and double strand DNA breaks and chromosomal aberrations for genotoxicity and cellular internalization for biokinetics and NPs intracellular fate. Briefly, the results showed uptake of both NPs; no basal cytotoxicity induced by AuNPs, while cytotoxicity, carcinogenic potential and genotoxicity were demonstrated for Co-nano. Concerning Co-nano, basal cytotoxicity was also observed by an impedance-based assay that can be considered as a new approach for the assessment of basal cytotoxicity induced by chemicals and that was demonstrated to be comparable with standard in vitro methods during this thesis work. This approach was also successfully applied to NPs. Our study also points out that any NPs toxicological study requires a preliminary careful physicochemical characterization of the NPs used, in order to highlight and understand their mechanisms of action. Moreover the possibility to use in vitro methods could be pointed out especially due to the fact that they can be considered "easier" to use in comparison to in vivo approaches, although the latter remain unavoidable, in particular to find the potential effect liked to the exposure routes in the body and the target organs. This work shows how complicated NPs toxicology research is and confirms the need for integrated approaches and discussion/agreement among scientists.(DOCSC03 ) -- FUNDP, 200