Estudo do Ruído Sísmico no Arquipélago de Cabo Verde

Traditionally the study of Earth's internal structure has been based on analysis of seismic waves recorded during the occurrence of earthquakes. Recently, some researchers have shown to be possible to use ambient seismic noise (generally generated by ocean storms) to obtain dispersion curves with satisfactory results. Moreover, the use of ambient seismic noise measurement has advantages because they are independent of the earthquake-station geometry. This study aims to determine the dispersion curves of Rayleigh waves from the analysis of ambient seismic noise records, obtained in Cape Verde archipelago, whose origin and structure has attracted interest from several researchers. Analyzing the data collected between November 2007 and September 2008, Green's functions were determined. The analysis of these functions allowed to construct energy diagrams and to measure dispersion curves of group velocities between pairs of stations.

Health investment complementarities under competing risks

Applying the competing--risks model to multi--cause mortality,this paper provides a theoretical and empirical investigation of the positive complementarities that occur between disease--specific policy interventions. We argue that since an individual cannot die twice, competing risks imply that individuals will not waste resources on causes that are not the most immediate, but will make health investments so as to equalize cause--specific mortality. However, equal mortality risk from a variety of diseases does not imply that disease--specific public health interventions are a waste. Rather, a cause--specific intervention produces spillovers to other disease risks, so that the overall reduction in mortality will generally be larger than the direct effect measured on the targeted disease. The assumption that mortality from non--targeted diseases remains the same after a cause--specific intervention under--estimates the true effect of such programs, since the background mortality is also altered as a result of intervention. Analyzing data from one of the most important public health programs ever introduced, the Expanded Program on Immunization (EPI) of the United Nations, we find evidence for the existence of such complementarities, involving causes that are not biomedically, but behaviorally, linked.

Expanding molecular modeling and design tools to non-natural sidechains.

Protein-protein interactions encode the wiring diagram of cellular signaling pathways and their deregulations underlie a variety of diseases, such as cancer. Inhibiting protein-protein interactions with peptide derivatives is a promising way to develop new biological and therapeutic tools. Here, we develop a general framework to computationally handle hundreds of non-natural amino acid sidechains and predict the effect of inserting them into peptides or proteins. We first generate all structural files (pdb and mol2), as well as parameters and topologies for standard molecular mechanics software (CHARMM and Gromacs). Accurate predictions of rotamer probabilities are provided using a novel combined knowledge and physics based strategy. Non-natural sidechains are useful to increase peptide ligand binding affinity. Our results obtained on non-natural mutants of a BCL9 peptide targeting beta-catenin show very good correlation between predicted and experimental binding free-energies, indicating that such predictions can be used to design new inhibitors. Data generated in this work, as well as PyMOL and UCSF Chimera plug-ins for user-friendly visualization of non-natural sidechains, are all available at http://www.swisssidechain.ch. Our results enable researchers to rapidly and efficiently work with hundreds of non-natural sidechains.

Pesca exploratoria y experimental con red de cerco artesanal en la Región Tumbes.2005

Se evaluó la utilización de la malla de 50 mm (2”) en redes de cerco artesanal de la Región Tumbes en una pesquería multiespecífica. Se trabajó con una red control de tamaño de malla de 38 mm (1,5”) y la red experimental de 50 mm (2,0”), con un porcentaje de embande de 0,65 y 0,77, respectivamente. Se determinó diferencia entre las curvas de profundidad de calado del cuerpo central de las redes (tc= 46,670, t*= 1,98, p= 0) la red experimental tuvo mayor profundidad de velado; entre las curvas de velocidad de caída del cuerpo central de las redes, hubo diferencia significativa (tc= 7,790, t*= 1,98, p = 0,000), debido al mayor lastre y filtrado de las mallas de la red experimental. El coeficiente abertura horizontal (μ1) de las mallas en la franja superior durante el máximo velado de la red y el gareteo fue en las mallas del cabecero o copo, parte central y ultimo cuerpo de la red, en promedio 0,71; 0,74 y 0,73 respectivamente; (valores cercanos al coeficiente de armado ideal para el escape de ciertos peces fusiformes). El promedio de μ1 obtenidos en la región de las mallas centrales en el cabecero, centro y ultimo cuerpo de la red fue 0,85; 0,85 y 0,84 respectivamente; lo que indicó una mayor abertura horizontal de las mallas por encima del valor del coeficiente de armado que no permitiría el escape de los peces. Se concluyó que por la condición de las mallas de la red de cerco experimental (tamaño de malla 50 mm) no es óptima para gran parte de la estructura de la red, esto no permitiría la selectividad por tamaños.

Bilan préopératoire pour la chirurgie cardio-vasculaire en urgence [Preoperative assessment in emergency cardiovascular surgery].

In the emergency situation, preoperative patient work-up for cardio-vascular surgery is quite different from the elective setting. We have analyzed a consecutive series of 5576 cases out of which 823 underwent emergency procedures (14.8%). The most frequent problems requiring emergent intervention were peripheral vascular (186 cases; 22.6% of the emergent procedure), followed by coronary artery disease (156 cases; 19.0%), thoracic aortic aneurysms (86 cases; 10.4%), abdominal aortic aneurysms (54 cases; 6.6%), congenital heart disease (36 cases: 4.4%), heart and heart lung transplantation (31 cases; 3.8%), problems with cardiac rythm (25 cases: 3.0%), and others (267 cases: 32.4%). Classification by proportion of urgent procedures with reference to elective operations shows a different picture. As a matter of fact transplantations were always emergency procedures (100%), whereas repair of aortic dissections type A and B was an emergency procedure in 81.5%. Emergency thoracic and abdominal aortic aneurysm repair accounted for 30% and 20% respectively and the corresponding proportion for peripheral vascular surgery is 19%. However, emergency surgery for acute coronary ischemia, valvular and congenital heart disease accounted for somewhat less than 10% for each group of these pathologies. Systematic pre-operative diagnostic work-up is a recognized tool for procedure related risk assessment and superior management of diseases. However, hemodynamic instability and other time related events correlated with negative outcome, are the main driving forces for accelerated diagnostic pathways

Ontogeny and covariation in the Toarcian genus Osperleioceras (Ammonoidea)

Starting from embryonic (protoconch-ammonitella) and early juvenile shells, which are indistinguishable at the species level, growth curves of Osperleioceras from the Reynesi Subzone (Upper Toarcian) of the Causses Basin (Aveyron, France) show a continuous radiating range of correlated variation in dimensional and ornamental characters, such as involution, whorl compression, rib strength and rib density. This covariation pattern can be observed among single-horizon assemblages, as well as during individual ontogenetic development. The existence of a continuous intergradational series of shells, ranging from stout coarsely ribbed to smooth suboxycone morphologies, rules out functional or ecological selectivity to explain this non-random variability pattern. The complex interdependence of shape and sculpture can be simulated by a model in which sculpture intensity depends on mantle curvature [GUEX, 1999]. The expression of covariation in subadult specimens since the base of Upper Toarcian reveals a rise in variability, concomitant with a size decrease, both contemporaneous with environmental instability. It developed in successive bursts from a fairly long low variability period spanning the whole Middle Toarcian.

Acute alcohol consumption and injury: risk associations and attributable fractions for different injury mechanisms.

OBJECTIVE: Most studies on alcohol as a risk factor for injuries have been mechanism specific, and few have considered several mechanisms simultaneously or reported alcohol-attributable fractions (AAFs)-which was the aim of the current study. METHOD: Data from 3,592 injured and 3,489 noninjured patients collected between January 2003 and June 2004 in the surgical ward of the emergency department of the Lausanne University Hospital (Switzerland) were analyzed. Four injury mechanisms derived from the International Classification of Diseases, 10th Revision, were considered: transportation-related injuries, falls, exposure to forces and other events, and interpersonal violence. Multinomial logistic regression models were calculated to estimate the risk relationships of different levels of alcohol consumption, using noninjured patients as quasi-controls. The AAFs were then calculated. RESULTS: Risk relationships between injury and acute consumption were found across all mechanisms, commonly resulting in dose-response relationships. Marked differences between mechanisms were observed for relative risks and AAFs, which varied between 15.2% and 33.1% and between 10.1% and 35.9%, depending on the time window of consumption (either 6 hours or 24 hours before injury, respectively). Low and medium levels of alcohol consumption generally were associated with the most AAFs. CONCLUSIONS: This study underscores the implications of even low levels of alcohol consumption on the risk of sustaining injuries through any of the mechanisms considered. Substantial AAFs are reported for each mechanism, particularly for injuries resulting from interpersonal violence. Observation of a so-called preventive paradox phenomenon is discussed, and prevention or intervention measures are described.

Trends in mortality from coronary heart and cerebrovascular disease in Switzerland, 1969-87.

Trends in age-specific and age-standardized death certification rates from all ischaemic heart disease and cerebrovascular disease in Switzerland have been analysed for the period 1969-87, i.e. since the introduction of the Eighth Revision of the International Classification of Diseases for coding causes of death. For coronary heart disease, overall age-standardized rates of males in the mid-late 1980's were similar to those in the late 1960's, although some upward trend was evident up to the mid 1970's (with a peak rate of 120.4/100,000, World standard, in 1978) followed by steady declines in more recent years (103.8/100,000 in 1987). These falls were larger in truncated (35 to 64 years) rates. For females, overall age-standardized rates were stable around a value of 40/100,000, while truncated rates tended to decrease, particularly over most recent years, with an overall decline of over 25%. Examination of age-specific trends showed that in both sexes declines at younger ages were already evident in the earlier calendar period, while above age 50 some fall became evident only in most recent years. Thus, in a formal log-linear age/period/cohort model, both a period and a cohort component emerged. In relation to cerebrovascular diseases, the overall declines were around 40% in males (from 67.4 to 41.2/100,000, World standard) and 45% for females (from 56.6 to 31.7/100,000), and were proportionally comparable across subsequent age groups above age 45. The estimates for the age/period/cohort model were thus downwards both for the period and the cohort component although, in such a situation, it is difficult to disentangle the major underlying component.(ABSTRACT TRUNCATED AT 250 WORDS)

Phonon softening in Ni-Mn-Ga alloys

The TA2 phonon dispersion curves of Ni-Mn-Ga alloys with different compositions which transform to different martensitic structures have been measured over a broad temperature range covering both paramagnetic and ferromagnetic phases. The branches show an anomaly (dip) at a wave number that depends on the particular martensitic structure, and there is softening of these anomalous phonons with decreasing temperature. This softening is enhanced below the Curie point, as a consequence of spin-phonon coupling. This effect is stronger for systems with higher electronic concentration.

Prestress in the extracellular matrix sensitizes latent TGF-β1 for activation.

Integrin-mediated force application induces a conformational change in latent TGF-β1 that leads to the release of the active form of the growth factor from the extracellular matrix (ECM). Mechanical activation of TGF-β1 is currently understood as an acute process that depends on the contractile force of cells. However, we show that ECM remodeling, preceding the activation step, mechanically primes latent TGF-β1 akin to loading a mechanical spring. Cell-based assays and unique strain devices were used to produce a cell-derived ECM of controlled organization and prestrain. Mechanically conditioned ECM served as a substrate to measure the efficacy of TGF-β1 activation after cell contraction or direct force application using magnetic microbeads. The release of active TGF-β1 was always higher from prestrained ECM as compared with unorganized and/or relaxed ECM. The finding that ECM prestrain regulates the bioavailability of TGF-β1 is important to understand the context of diseases that involve excessive ECM remodeling, such as fibrosis or cancer.

Counter-ion effect on surfactant-DNA gel particles as controlled DNA delivery systems

The ability to entrap drugs within vehicles and subsequently release them has led to new treatments for a number of diseases. Based on an associative phase separation and interfacial diffusion approach, we developed a way to prepare DNA gel particles without adding any kind of cross-linker or organic solvent. Among the various agents studied, cationic surfactants offered particularly efficient control for encapsulation and DNA release from these DNA gel particles. The driving force for this strong association is the electrostatic interaction between the two components, as induced by the entropic increase due to the release of the respective counter-ions. However, little is known about the influence of the respective counter-ions on this surfactant-DNA interaction. Here we examined the effect of different counter-ions on the formation and properties of the DNA gel particles by mixing DNA (either single- (ssDNA) or double-stranded (dsDNA)) with the single chain surfactant dodecyltrimethylammonium (DTA). In particular, we used as counter-ions of this surfactant the hydrogen sulfate and trifluoromethane sulfonate anions and the two halides, chloride and bromide. Effects on the morphology of the particles obtained, the encapsulation of DNA and its release, as well as the haemocompatibility of these particles, are presented, using the counter-ion structure and the DNA conformation as controlling parameters. Analysis of the data indicates that the degree of counter-ion dissociation from the surfactant micelles and the polar/hydrophobic character of the counter-ion are important parameters in the final properties of the particles. The stronger interaction with amphiphiles for ssDNA than for dsDNA suggests the important role of hydrophobic interactions in DNA.

In rats, oral oleoyl-DHEA is rapidly hydrolysed and converted to DHEA-sulphate

Background: Dehydroepiandrosterone (DHEA) released by adrenal glands may be converted to androgens and estrogens mainly in the gonadal, adipose, mammary, hepatic and nervous tissue. DHEA is also a key neurosteroid and has antiglucocorticoid activity. DHEA has been used for the treatment of a number of diseases, including obesity; its pharmacological effects depend on large oral doses, which effect rapidly wanes in part because of its short half-life in plasma. Since steroid hormone esters circulate for longer periods, we have studied here whether the administration of DHEA oleoyl ester may extend its pharmacologic availability by keeping high circulating levels. Results: Tritium-labelled oleoyl-DHEA was given to Wistar male and female rats by gastric tube. The kinetics of appearance of the label in plasma was unrelated to sex; the pattern being largely coincident with the levels of DHEA-sulfate only in females, and after 2 h undistinguishable from the results obtained using labelled DHEA gavages; in the short term, practically no lipophilic DHEA label was found in plasma. After 24 h only a small fraction of the label remained in the rat organs, with a different sex-related distribution pattern coincident for oleoyl- and free- DHEA gavages. The rapid conversion of oleoyl-DHEA into circulating DHEA-sulfate was investigated using stomach, liver and intestine homogenates; which hydrolysed oleoyl-DHEA optimally near pH 8. Duodenum and ileum contained the highest esterase activities. Pure hog pancreas cholesterol-esterase broke down oleoyl-DHEA at rates similar to those of oleoyl-cholesterol. The intestinal and liver esterases were differently activated by taurocholate and showed different pH-activity patterns than cholesterol esterase, suggesting that oleoyl-DHEA can be hydrolysed by a number of esterases in the lumen (e.g. cholesterol-esterase), in the intestinal wall and the liver. Conclusion: The esterase activities found may condition the pharmacological availability (and depot effect) of orally administered steroid hormone fatty acid esters such as oleoyl-DHEA. The oral administration of oleoyl-DHEA in order to extend DHEA plasma availability has not been proved effective, since the ester is rapidly hydrolysed, probably in the intestine itself, and mainly converted to DHEA-sulfate at least in females.

Oxidation and ubiquitination in neurodegeneration.

It is widely accepted that protein oxidation is involved in a variety of diseases, including neurodegenerative diseases. Especially during aging, a reduction in anti-oxidant defence mechanisms leads to an increased formation of free radical oxygen species and consequently results in a damage of proteins, including mitochondrial and synaptic ones. Even those proteins involved in repair and protein clearance via the ubiquitin proteasome and lysosomal system are subject to damage and show a reduced function. Here, we will discuss a variety of mechanisms and provide examples where cognition is affected and where repair mechanisms are no longer sufficient to compensate for a dysfunction of damaged proteins or even may become toxic. Next to physiological deficits, an accumulation of deficient proteins in aggresomes may occur and result in a formation of pathological hallmark structures typical for aging and disease. A major challenge is how to prevent aberrant oxidation, given that oxidation plays an essential role in aging and neurodegenerative diseases. Particularly interesting are the possibilities to reduce the formation of radical oxygen species leading to a dysfunction of protein repair and protein clearance, or to a formation of toxic byproducts accelerating neurodegeneration.

Régulation du canal à sodium épithélial par le sodim extracellulaire et développement d'un microsystème intégré pour l'étude électrophysiologique sur ovocytes de "Xenopus laevis"

Résumé : La première partie de ce travail de thèse est consacrée au canal à sodium épithélial (ENaC), l'élément clé du transport transépithélial de Na+ dans le néphron distal, le colon et les voies aériennes. Ce canal est impliqué dans certaines formes génétiques d'hypo- et d'hypertension (PHA I, syndrome de Liddle), mais aussi, indirectement, dans la mucoviscidose. La réabsorption transépithéliale de Na+ est principalement régulée par des hormones (aldostérone, vasopressine), mais aussi directement par le Na+, via deux phénomènes distincts, la « feedback inhibition » et la « self-inhibition » (SI). Ce second phénomène est dépendant de la concentration de Na+ extracellulaire, et montre une cinétique rapide (constante de temps d'environ 3 s). Son rôle physiologique serait d'assurer l'homogénéité de la réabsorption de Na+ et d'empêcher que celle-ci soit excessive lorsque les concentrations de Na+ sont élevées. Différents éléments appuient l'hypothèse de la présence d'un site de détection de la concentration du Na+ extracellulaire sur ENaC, gouvernant la SI. L'objectif de ce premier projet est de démontrer l'existence du site de détection impliqué dans la SI et de déterminer ses propriétés physiologiques et sa localisation. Nous avons montré que les caractéristiques de la SI (en termes de sélectivité et affinité ionique) sont différentes des propriétés de conduction du canal. Ainsi, nos résultats confirment l'hypothèse de l'existence d'un site de détection du Na+ (responsable de la transmission de l'information au mécanisme de contrôle de l'ouverture du canal), différent du site de conduction. Par ailleurs, ce site présente une affinité basse et indépendante du voltage pour le Na+ et le Li+ extracellulaires. Le site semble donc être localisé dans le domaine extracellulaire, plutôt que transmembranaire, de la protéine. L'étape suivante consiste alors à localiser précisément le site sur le canal. Des études précédentes, ainsi que des résultats préliminaires récemment obtenus, mettent en avant le rôle dans la self-inhibition du premiers tiers des boucles extracellulaires des sous-unités α et γ du canal. Le second projet tire son origine des limitations de la méthode classique pour l'étude des canaux ioniques, après expression dans les ovocytes de Xenopus laevis, par la méthode du voltage-clamp à deux électrodes, en particulier les limitations dues à la lenteur des échanges de solutions. En outre, cette méthode souffre de nombreux désavantages (manipulations délicates et peu rapides, grands volumes de solution requis). Plusieurs systèmes améliorés ont été élaborés, mais aucun ne corrige tous les désavantages de la méthode classique Ainsi, l'objectif ici est le développement d'un système, pour l'étude électrophysiologique sur ovocytes, présentant les caractéristiques suivantes : manipulation des cellules facilitée et réduite, volumes de solution de perfusion faibles et vitesse rapide d'échange de la perfusion. Un microsystème intégré sur une puce a été élaboré. Ces capacités de mesure ont été testées en utilisant des ovocytes exprimant ENaC. Des résultats similaires (courbes IV, courbes dose-réponse au benzamil) à ceux obtenus avec le système traditionnel ont été enregistrés avec le microsystème. Le temps d'échange de solution a été estimé à ~20 ms et des temps effectifs de changement ont été déterminés comme étant 8 fois plus court avec le nouveau système comparé au classique. Finalement, la SI a été étudiée et il apparaît que sa cinétique est 3 fois plus rapide que ce qui a été estimé précédemment avec le système traditionnel et son amplitude de 10 à 20 % plus importante. Le nouveau microsystème intégré apparaît donc comme adapté à la mesure électrophysiologique sur ovocytes de Xenopus, et possèdent des caractéristiques appropriées à l'étude de phénomènes à cinétique rapide, mais aussi à des applications de type « high throughput screening ». Summary : The first part of the thesis is related to the Epithelial Sodium Channel (ENaC), which is a key component of the transepithelial Na+ transport in the distal nephron, colon and airways. This channel is involved in hypo- and hypertensive syndrome (PHA I, Liddle syndrome), but also indirectly in cystic fibrosis. The transepithelial reabsorption of Na+ is mainly regulated by hormones (aldosterone, vasopressin), but also directly by Na+ itself, via two distinct phenomena, feedback inhibition and self-inhibition. This latter phenomenon is dependant on the extracellular Na+ concentration and has rapid kinetics (time constant of about 3 s). Its physiological role would be to prevent excessive Na+ reabsorption and ensure this reabsorption is homogenous. Several pieces of evidence enable to propose the hypothesis of an extracellular Na+ sensing site on ENaC, governing self-inhibition. The aim of this first project is to demonstrate the existence of the sensing site involved in self-inhibition and to determine its physiological properties and localization. We show self-inhibition characteristics (ionic selectivity and affinity) are different from the conducting properties of the channel. Our results support thus the hypothesis that the Na+ sensing site (responsible of the transmission of the information about the extracellular Na+ concentration to the channel gating mechanism), is different from the channel conduction site. Furthermore, the site has a low and voltage-insensitive affinity for extracellular Na+ or Li+. This site appears to be located in the extracellular domain rather than in the transmembrane part of the channel protein. The next step is then to precisely localize the site on the channel. Some previous studies and preliminary results we recently obtained highlight the role of the first third of the extracellular loop of the α and γ subunits of the channel in self-inhibition. The second project originates in the limitation of the classical two-electrode voltageclamp system classically used to study ion channels expressed in Xenopus /aevis oocytes, in particular limitations related to the slow solution exchange time. In addition, this technique undergoes several drawbacks (delicate manipulations, time consumption volumes). Several improved systems have been built up, but none corrected all these detriments. The aim of this second study is thus to develop a system for electrophysiological study on oocytes featuring an easy and reduced cell handling, small necessary perfusion volumes and fast fluidic exchange. This last feature establishes the link with the first project, as it should enable to improve the kinetics analysis of self-inhibition. A PDMS chip-based microsystem has been elaborated. Its electrophysiological measurement abilities have been tested using oocytes expressing ENaC. Similar measurements (IV curves of benzamil-sensitive currents, benzamil dose-response curves) have been obtained with this system, compared to the traditional one. The solution exchange time has been estimated at N20 ms and effective exchange times (on inward currents) have been determined as 8 times faster with the novel system compared to the classical one. Finally, self-inhibition has been studied and it appears its kinetics is 3 times faster and its amplitude 10 to 20 % higher than what has been previously estimated with the traditional system. The novel integrated microsystem appears therefore to be convenient for electrophysiological measurement on Xenopus oocytes, and displays features suitable for the study of fast kinetics phenomenon, but also high throughput screening applications. Résumé destiné large public : Le corps humain est composé d'organes, eux-mêmes constitués d'un très grand nombre de cellules. Chaque cellule possède une paroi appelée membrane cellulaire qui sépare l'intérieur de cette cellule (milieu intracellulaire) du liquide (milieu extracellulaire) dans lequel elle baigne. Le maintien de la composition stable de ce milieu extracellulaire est essentiel pour la survie des cellules et donc de l'organisme. Le sodium est un des composants majeurs du milieu extracellulaire, sa quantité dans celui-ci doit être particulièrement contrôlée. Le sodium joue en effet un rôle important : il conditionne le volume de ce liquide extracellulaire, donc, par la même, du sang. Ainsi, une grande quantité de sodium présente dans ce milieu va de paire avec une augmentation du volume sanguin, ce qui conduit l'organisme à souffrir d'hypertension. On se rend donc compte qu'il est très important de contrôler la quantité de sodium présente dans les différents liquides de l'organisme. Les apports de sodium dans l'organisme se font par l'alimentation, mais la quantité de sodium présente dans le liquide extracellulaire est contrôlée de manière très précise par le rein. Au niveau de cet organe, on appelle urine primaire le liquide résultant de la filtration du sang. Elle contient de nombreuses substances, des petites molécules, dont l'organisme a besoin (sodium, glucose...), qui sont ensuite récupérées dans l'organe. A la sortie du rein, l'urine finale ne contient plus que l'excédent de ces substances, ainsi que des déchets à éliminer. La récupération du sodium est plus ou moins importante, en fonction des ajustements à apporter à la quantité présente dans le liquide extracellulaire. Elle a lieu grâce à la présence de protéines, dans les membranes des cellules du rein, capables de le transporter et de le faire transiter de l'urine primaire vers le liquide extracellulaire, qui assurera ensuite sa distribution dans l'ensemble de l'organisme. Parmi ces protéines « transporteurs de sodium », nous nous intéressons à une protéine en particulier, appelée ENaC. Il a été montré qu'elle jouait un rôle important dans cette récupération de sodium, elle est en effet impliquée dans des maladies génétiques conduisant à l'hypo- ou à l'hypertension. De précédents travaux ont montré que lorsque le sodium est présent en faible quantité dans l'urine primaire, cette protéine permet d'en récupérer une très grande partie. A l'inverse, lorsque cette quantité de sodium dans l'urine primaire est importante, sa récupération par le biais d'ENaC est réduite. On parle alors d'autorégulation : la protéine elle-même est capable d'adapter son activité de transport en fonction des conditions. Ce phénomène d'autorégulation constitue a priori un mécanisme préventif visant à éviter une trop grande récupération de sodium, limitant ainsi les risques d'hypertension. La première partie de ce travail de thèse a ainsi consisté à clarifier le mécanisme d'autorégulation de la protéine ENaC. Ce phénomène se caractérise en particulier par sa grande vitesse, ce qui le rend difficile à étudier par les méthodes traditionnelles. Nous avons donc, dans une deuxième partie, développé un nouveau système permettant de mieux décrire et analyser cette « autorégulation » d'ENaC. Ce second projet a été mené en collaboration avec l'équipe de Martin Gijs de l'EPFL.

Muscarinic receptor M1 and phosphodiesterase 1 are key determinants in pulmonary vascular dysfunction following perinatal hypoxia in mice.

Perinatal adverse events such as limitation of nutrients or oxygen supply are associated with the occurrence of diseases in adulthood, like cardiovascular diseases and diabetes. We investigated the long-term effects of perinatal hypoxia on the lung circulation, with particular attention to the nitric oxide (NO)/cGMP pathway. Mice were placed under hypoxia in utero 5 days before delivery and for 5 days after birth. Pups were then bred in normoxia until adulthood. Adults born in hypoxia displayed an altered regulation of pulmonary vascular tone with higher right ventricular pressure in normoxia and increased sensitivity to acute hypoxia compared with controls. Perinatal hypoxia dramatically decreased endothelium-dependent relaxation induced by ACh in adult pulmonary arteries (PAs) but did not influence NO-mediated endothelium-independent relaxation. The M(3) muscarinic receptor was implicated in the relaxing action of ACh and M(1) muscarinic receptor (M(1)AChR) in its vasoconstrictive effects. Pirenzepine or telenzepine, two preferential inhibitors of M(1)AChR, abolished the adverse effects of perinatal hypoxia on ACh-induced relaxation. M(1)AChR mRNA expression was increased in lungs and PAs of mice born in hypoxia. The phosphodiesterase 1 (PDE1) inhibitor vinpocetine also reversed the decrease in ACh-induced relaxation following perinatal hypoxia, suggesting that M(1)AChR-mediated alteration of ACh-induced relaxation is due to the activation of calcium-dependent PDE1. Therefore, perinatal hypoxia leads to an altered pulmonary circulation in adulthood with vascular dysfunction characterized by impaired endothelium-dependent relaxation and M(1)AChR plays a predominant role. This raises the possibility that muscarinic receptors could be key determinants in pulmonary vascular diseases in relation to "perinatal imprinting."