Pseudomonas aeruginosa est un pathogène opportuniste responsable d'infections graves chez les personnes immunodéprimées, les grands brûlés et les patients atteints de la mucoviscidose. Cette pathogénicité repose sur de nombreux facteurs de virulence dont le système de sécrétion de type III (SSTT).Nous avons observé une protéine précédemment identifiée, PsrA, nécessaire pour la pleine activation de l'expression du SSTT chez P. aeruginosa. Les analyses par retard de migration électrophorétique de fragments du promoteur de l'operon régulateur exsCEBA ont montré que la protéine recombinante PsrA pourrait se fixer sur celui-ci. Le mutant DpsrA a montré une diminution marquée de la sécrétion des effecteurs de type III et une faible résistance à la bactéricidie par des cellules de type phagocytaires, PLB-985. L'ensemble des résultats suggèrent que PsrA est un nouvel activateur qui est impliqué dans l'expression du SSTT en augmentant le niveau de la transcription d'exsCEBA.Dans un second temps, nous avons mis en évidence qu'un signal inhibiteur, de type quorum sensing inconnu et produit dans la phase stationnaire de la culture, peut réprimer l'expression du SSTT in vitro. L'analyse de milliers de mutants de transposition a montré que la production de ce signal dépend du tryptophane, qui est le précurseur de nombreux métabolites dont l'acide d'indole-3-acétic (IAA). IAA-Na et un autre membre de cette famille de molécules, le acide 1-naphthalenacétique (NAA-K) aux concentrations millimolaires peuvent en effet inhiber l'expression et la sécrétion du SSTT. L'identification précise de ce signal nécessite des investigations plus poussées.

The development of the mature cardiovascular system is one of the most captivating stories in embryonic development. The heart is the first organ to form in embryogenesis, and is functional early in development to perfuse the embryo with blood supplying oxygen and the nutrients required for organogenesis. The structural changes in heart development required for formation of the mature four chambered heart are under tight molecular regulation. Severe defects manifest as gross structural malformations of the valves, septa, or vessels that result in physiological consequences that my include hypertension, arrhythmia, or heart failure and may ultimately lead to lethality. According to the American Heart Association, cardiovascular disease is the leading cause of mortality worldwide. A more detailed understanding of the origin of congenital heart defects is necessary for improving prediction, diagnosis, and treatment of cardiovascular disease. Derived from the epicardium, coronary vessel formation relies on growth factor as well as extracellular matrix (ECM) influences on cells of the epicardium that regulate proliferation, motility, invasion and differentiation. The Transforming Growth Factor β (TGFβ) family of receptors have been well described in regulating cardiovascular development. The Type III TGFβ receptor (TGFβR3) has been shown to be required for development of the coronary vessels. Mouse embryos lacking TGFβR3 exhibit inhibited invasion of epicardially derived cells (EPDCs) into the myocardium. This delay of cell invasion of EPDCs and formation of coronary vessels is lethal at E 14.5. Relative to Tgfbr3+/+ cells, epicardial cells lacking TGFβR3 are hypo-proliferative, deficient in cell invasion, and deficient in executing TGFβ ligand and High-Molecular Weight Hyaluronan (HMWHA) stimulated cell invasion. Hyaluronan (HMWHA) is a glycosaminoglycan unmodified sugar extracellular matrix (ECM) molecule synthesized by the Hyaluronan Synthase (Has) family of enzymes. Mouse embryos lacking Hyaluronan Synthase 2 (Has2) are lethal at E 9.5 as a result of severely blocked cardiogenesis due to insufficient endocardial EMT. HA serves structural and bioactive functions in its capacity to stimulate signal transduction pathways required for EMT. Src kinase is a non-receptor tyrosine kinase well characterized to function in growth factor as well as ECM signal transduction, but its role in epicardial cell biology is unclear. Our hypothesis is that Src kinase is a critical regulator of TGFβ and Hyaluronan induced epicardial cell invasion, differentiation and migration during coronary vessel development. Our studies reveal that Src activity is required for TGFβ2-induced synthesis of HA in epicardial cells. We show Src is required for TGFβ2-induced vascular smooth muscle differentiation as well as TGFβ2-induced EMT, cell invasion, and filamentous actin polymerization. Src activity is sufficient to drive epicardial activation of EMT, but not vascular smooth muscle differentiation. These data show that Src is required in the context of TGFβ2-stimulated invasion and differentiation, and sufficient to drive activation of EMT. Next we demonstrate that TGFβR3 and Src are required for HMWHA induced cell invasion and filamentous actin polymerization in epicardial cells. HMWHA induces activation of Src kinase in Tgfbr3+/+ epicardial cells, but not Tgfbr3-/- epicardial cells. siRNA knockdown of TGFβR3 in Tgfbr3+/+ epicardial cells subsequently stimulated with HMWHA phenocopy this deficit in Src activation. Tgfbr3-/- epicardial cells fail to activate Rac1 or RhoA GTPases in the presence of HMWHA. Finally, we demonstrate stimulus independent activation of TGFβR3 is sufficient to activate Src. Taken together, these constitute novel findings establishing TGFβR3 as an HMWHA responsive receptor that is upstream of Src signal transduction. Migration of the epicardium to cover the looped and functioning heart tube is an early step required for development of the coronary vessels. We demonstrate that Tgfbr3-/- epicardial cells are delayed in cell migration relative to Tgfbr3+/+ cells in a wound healing model of cell migration. Tgfbr3-/- cells lack expression of BMP2 mRNA, we found that exogenous BMP2 is sufficient to drive Tgfbr3-/- (but not Tgfbr3+/+) cell migration to levels comparable to unstimulated Tgfbr3+/+ epicardial cells, without enhancing cell proliferation. We demonstrate that Src is required for this BMP2 induced cell migration and filamentous actin polymerization in Tgfbr3-/- cells. These studies demonstrate mechanisms required for TGFβ ligand as well as HMWHA stimulated epicardial cell behavior changes have a common mediator in Src kinase, and provide novel insights into early events in the development of the cardiovascular system. The adult epicardium has been demonstrated to participate in repair of ischemic myocardium in mouse models of myocardial infarction. Expression of molecules required for coronary vessel development are re-expressed in this regeneration (as discussed in chapter 5). Elucidating these pathways will constitute important future targets in aiding in adult cardiovascular regeneration and cardioprotection in adult heart disease.

No description available.

Type III secretion is a virulence system utilized by several clinically important Gram-negative pathogens. Computational methods have been used to develop two classes of type III secretion inhibitors, the salicylidene acylhydrazides and the acetylated salicylanilides. For these classes of compounds, quantitative structure-activity relationship models have been constructed with data from focused libraries obtained by statistical molecular design. The models have been validated and shown to provide useful predictions of untested compounds belonging to these classes. Scaffold hopping of the salicylidene acylhydrazides have resulted in a number of synthetic targets that might mimic the scaffold of the compounds. The synthesis of two libraries of analogs to two of these scaffolds and the biological evaluation of them is presented.

Blockade of the renin-angiotensin system lowers the rate of cardiovascular events in patients at risk for vascular disease and also improves endothelial function but the mechanism remains unclear. HUVECs were stimulated with Ang II (100 nM). Ang II produced a 2-fold increase in O2- production, which was measured by lucigenin-enhanced chemiluminescence. This increase was blocked by NAD(P)H oxidase inhibitor DPI, but not by eNOS inhibitor L-NAME. Ang II increased monocyte adhesion to ECs by 4.5-fold, and this increase was blocked by candesartan (AT1 receptor antagonist), DPI, L-NAME, wortmannin (PI3K inhibitor), dominant negative-AKT, and p22phox siRNA. Dominant active-AKT increased adhesion by 1.5-fold. Our findings indicate that the simultaneous activation by Ang II of eNOS and NAD(P)H oxidase leads to endothelial activation. This process can partially explain the therapeutic benefits of reducing the action of Ang II.

Pseudomonas aeruginosa causes various infections in humans, animals and plants. Type III secretion system (T3SS) is one of the essential virulence factors used by P. aeruginosa. In this study, a previously uncharacterized gene PA0466 and its role in T3SS regulation have been examined. The results indicate that PA0466 is a novel T3SS regulator. It regulates T3SS directly through an unknown pathway and has a minor effect on the GacA-RsmA pathway. Besides the role in the interaction between the pathogen and the host, T3SS may also play a role in the interspecies interaction. A real-time PCR based Competitive Index (CI) assay was used to compare the wild type and T3SS mutant with and without the presence of Staphylococcus spp.. The results indicate that PAO1 was more competitive than exsA mutant and the difference was even bigger in the presence of Staphylococcus, suggesting T3SS may play a significant role in bacterium-bacterium interaction.

Power consumption is the primary concern in battery-operated portable applications. Buck converters have gained popularity in powering portable devices due to their compact size, good current delivery capability and high efficiency. However, portable devices are operating under light load condition for the most of the time. Conventional buck converters suffer from low light-load efficiency which severely limits battery lifetime. In this project, a novel technique for buck converter is proposed to reduce the switching loss by reducing the effective input supply voltage at light load. This is achieved by switching between two different input voltages (3.3V and 1.65V) depending on the output current value. Experimental results show that this technique improves the efficiency at light loads by 18.07%. The buck voltage possesses an output voltage of 0.9V and provides a maximum output current of 400mA. The buck converter operates at a switching frequency of 1MHz. The prototype was fabricated using 0.18µm CMOS technology, and occupies a total active area of 0.6039mm^2.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "August 2007" Includes bibliographical references.

Les salmonelles, responsables de fièvres typhoïdes et gastro-entérites, sont un problème majeur de santé publique. Les systèmes de sécrétion de type III (TTSS) sont des facteurs de virulence cruciaux de Salmonella. Nos travaux ont montré que délétion du cadre ouvert de lecture yfgL conduit à une faible transcription des gènes codant les 3 TTSS conduisant à une baisse importante de la virulence de Salmonella Enteritidis. Or, la délétion de ce gène, dont la protéine chez E.coli est en complexe avec les protéines YaeT, YfiO, NlpB et SmpA, conduit à une altération de la membrane externe. Chez S. Enteritidis, nous avons montré que le rôle du complexe « YaeT » dans l’assemblage des protéines de membrane externe est conservé. Or, seule l’inactivation d’yfiO, conduit une diminution de l’expression des TTSS. Nos travaux ont toutefois suggéré que le défaut d’assemblage des protéines de membrane externe n’est pas la cause de ce défaut d’expression des TTSS observés chez les mutants yfgL et yfiO. / Salmonella, responsible for typhoid fever and gastroenteritis, is a worldwide health problem. Type three secretion system (TTSS) are crucial virulence factors in Salmonella. Our work showed that deletion of the open reading frame yfgL led to a transcriptional down-regulation of the genes encoding the proteins involved in the biosynthesis of the 3 TTSS in Salmonella Enteritidis. It was shown that inactivation of yfgL whose encoded protein is in complex with YaeT, YfiO, NlpB and SmpA in E. coli, causes an outer membrane alteration. In S. Enteritidis, we observed that the role of the “YaeT” complex in outer membrane protein assembly is conserved in S. Enteritidis. In addition, only yfiO inactivation resulted in a down-expression of the TTSS. However, we presented elements suggesting that the outer membrane protein targeting defect was not responsible for the TTSS down-expression observed in the yfgL and yfiO mutants.

This thesis, which focuses on sleep disturbance in people with neurodevelopmental disabilities, is divided into three sections. Paper one is a systematic review of the extant literature on objective studies of sleep in neurodevelopmental genetic disorders. Twenty papers met inclusion criteria and were subject to quality assessment, of which five were found to be high-quality, thirteen were medium-quality and two were low-quality. Studies were grouped by disorder and although there was some disparity across investigations, generally there was agreement about specific sleep difficulties in each disorder which seem to be part of the behavioural phenotypes. Overall a lack of total sleep, diminished REM sleep, and fragmented, less efficient sleep are prevalent across the disorders. Paper two is an empirical study which employed actigraphy to assess sleep in children with mucopolysaccharidosis type III (MPS III) and typically developing children. Parents completed a sleep diary, a sleep questionnaire and took saliva samples from their child. Actigraphic findings showed that MPS III patients had lengthened sleep onset latencies and greater daytime sleep than controls, but night-time sleep duration was within the normal range. In the MPS III group, some sleep problems correlated with age and progression of the disorder. Analysis of saliva samples revealed that children with MPS III had abnormal melatonin concentrations. Questionnaire responses demonstrated that children with MPS III had more sleep difficulties in all domains compared to controls. Implications for the management of sleep difficulties are discussed. Paper three is a critical appraisal of the research process which includes personal reflections on designing and conducting this research and a discussion of the principal issues which arose. Strengths and limitations of the research, ideas for further research and implications for clinical practice are considered.