Le blocage de la reconsolidation des souvenirs, une avenue possible pour le traitement du trouble de stress post-traumatique?

La présente thèse porte sur l’évaluation de l’efficacité d’un nouveau traitement pour le trouble de stress post-traumatique (TSPT). Le traitement a été développé selon les prémisses de la théorie de la reconsolidation des souvenirs. Il consiste en six courtes séances de remémoration de l’événement traumatique réalisées sous l’effet du propranolol, un bêtabloquant. La population de l’étude est constituée de patients souffrant d’un TSPT chronique. La thèse comporte cinq chapitres. Le premier chapitre est l’introduction, on y retrouve une description du TSPT, des traitements validés empiriquement, de diverses théories de la mémoire, d’un modèle étiologique du TSPT, d’études sur la consolidation et la reconsolidation, de la pharmacocinétique et du mécanisme d’action du propranolol,ainsi que des objectifs de la thèse. Le second chapitre est une revue critique de littérature sur la théorie de la reconsolidation. Comme l’étude du phénomène de la reconsolidation est récente, nous tentons de faire le point sur l’état des connaissances dans le domaine, dans un effort de réflexion sur la validité de la théorie. Nous proposons une série de critères permettant de différencier la reconsolidation d’autres processus connexes. Nous concluons que la théorie paraît valide, bien que d’autres études soient nécessaires afin de rendre compte de résultats négatifs publiés par le passé. Le troisième chapitre est un essai ouvert, et vise à évaluer l’efficacité d’un traitement basé sur la reconsolidation à diminuer la sévérité et l’incidence du TSPT, auprès de 42 patients souffrant d’un TSPT chronique. Le traitement consiste en six séances de remémoration de l’événement traumatique sous propranolol. Lors d’un suivi à trois mois, nous rapportons une diminution des symptômes de TSPT de 41%-56%, ainsi qu’une diminution de l’incidence du TSPT de 74%. En comparaison, seulement 2/25 patients du groupe contrôle (ayant participé uniquement aux évaluations) ne souffrent plus d’un TSPT. Dans le groupe traitement, les tailles d’effet (d de Cohen)varient entre 1.32-2.19. Le quatrième chapitre a comme objectif d’identifier des caractéristiques des patients prédisant l’efficacité du traitement, et d’explorer s’ils s’améliorent dans des domaines de santé autres que le TSPT. Nous rapportons que les femmes s’améliorent davantage que les hommes, mais que d’autres facteurs, tels que la sévérité des traits de personnalité borderline ou le type de trauma (enfance versus adulte), n’influent pas sur l’efficacité. Également, les patients s’améliorent dans les domaines de santé suivants : la qualité de vie, la symptomatologie dépressive, l’intensité des émotions négatives au rappel de l’événement traumatique et dans la vie courante. Le cinquième chapitre contient la discussion générale de la thèse. Nous effectuons une synthèse et interprétation des résultats, nous examinons les hypothèses alternatives à l’amélioration clinique et abordons des pistes de recherches futures. Nous concluons que le traitement à l’étude a été efficace dans notre échantillon de patients souffrant d’un TSPT chronique. Étant donné la méthodologie employée (essai ouvert), nous ne pouvons statuer sur le mécanisme d’action du traitement, à savoir si l’amélioration clinique a été réellement causée par un blocage de la reconsolidation des souvenirs.

The skull of the Upper Cretaceous snake Dinilysia patagonica Smith-Woodward, 1901, and its phylogenetic position revisited

The cranial anatomy of Dinilysia patagonica, a terrestrial snake from the Upper Cretaceous of Argentina, is redescribed and illustrated, based on high-resolution X-ray computed tomography and better preparations made on previously known specimens, including the holotype. Previously unreported characters reinforce the intriguing mosaic nature of the skull of Dinilysia, with a suite of plesiomorphic and apomorphic characters with respect to extant snakes. Newly recognized plesiomorphies are the absence of the medial vertical flange of the nasal, lateral position of the prefrontal, lizard-like contact between vomer and palatine, floor of the recessus scalae tympani formed by the basioccipital, posterolateral corners of the basisphenoid strongly ventrolaterally projected, and absence of a medial parietal pillar separating the telencephalon and mesencephalon, amongst others. We also reinterpreted the structures forming the otic region of Dinilysia, confirming the presence of a crista circumfenestralis, which represents an important derived ophidian synapomorphy. Both plesiomorphic and apomorphic traits of Dinilysia are treated in detail and illustrated accordingly. Results of a phylogenetic analysis support a basal position of Dinilysia, as the sister-taxon to all extant snakes. The fossil taxa Yurlunggur, Haasiophis, Eupodophis, Pachyrhachis, and Wonambi appear as derived snakes nested within the extant clade Alethinophidia, as stem-taxa to the crown-clade Macrostomata. The hypothesis of a sister-group relationship between Dinilysia and Najash rionegrina, as suggested by some authors, is rejected by the results of our analysis.

Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

La lingua e l'estraneità: Franco Biondi e la letteratura dell'immigrazione in Germania. Proposta di traduzione di "Und nun schieben sie mich ab"

In questo lavoro è presentata una proposta di traduzione del racconto Und nun schieben sie mich ab (Biondi, 1985: 168- 174), di Franco Biondi, un autore di origini italiane residente in Germania dal 1965 (Amodeo, 2007: 6). Data la sua biografia, Biondi è un autore emblematico tanto della letteratura italiana della migrazione, quanto della letteratura dell’immigrazione in Germania, a testimonianza di come questa letteratura sia riuscita a superare i confini letterari nazionali per entrare a far parte di una «letteratura mondiale della transculturalità» (Amodeo, 2000: 327) . Considerati il terreno comune su cui si sono sviluppate le opere di autori di varie nazionalità in Germania, e l’eterogeneità dei contesti letterari e sociali degli autori italiani nei vari Paesi, si è ritenuto più efficace focalizzare i capitoli teorici del lavoro sulla letteratura dell’immigrazione in Germania, con un’attenzione particolare agli autori di origine italiana. La proposta di traduzione sarà preceduta da un inquadramento storico degli albori della letteratura dell’immigrazione in Germania, nata negli anni Sessanta del Novecento. Da lì si procederà presentando gli sviluppi di questa letteratura fino agli anni più recenti: si partirà dalla letteratura dell’immigrazione in Germania prodotta da autori di varie nazionalità, entrando poi nel merito degli autori di origine italiana attivi in Germania. Il terzo capitolo è dedicato a Franco Biondi, di cui saranno presentate una breve biografia e le opere più significative. Il quarto e il quinto capitolo sono dedicati interamente al racconto Und nun schieben sie mich ab (Biondi, 1985): in particolare, il quarto capitolo contiene un’analisi del tema e del contenuto del racconto, contestualizzato poi all’interno della raccolta “Passavantis Rückkehr” (Ibid.) e dell’opera dell’autore; in questo capitolo inoltre viene presentata un’analisi linguistica e stilistica del racconto. Il quinto capitolo contiene la proposta di traduzione, seguita da un commento della traduzione e delle strategie utilizzate.