A structural MRI study of motor conversion disorder: evidence of reduction in thalamic volume.

OBJECTIVE: To investigate potential abnormalities in subcortical brain structures in conversion disorder (CD) compared with controls using a region of interest (ROI) approach. METHODS: Fourteen patients with motor CD were compared with 31 healthy controls using high-resolution MRI scans with an ROI approach focusing on the basal ganglia, thalamus and amygdala. Brain volumes were measured using Freesurfer, a validated segmentation algorithm. RESULTS: Significantly smaller left thalamic volumes were found in patients compared with controls when corrected for intracranial volume. These reductions did not vary with handedness, laterality, duration or severity of symptoms. CONCLUSIONS: These differences may reflect a primary disease process in this area or be secondary effects of the disorder, for example, resulting from limb disuse. Larger, longitudinal structural imaging studies will be required to confirm the findings and explore whether they are primary or secondary to CD.

PPAR disruption: Cellular mechanisms and physiological consequences

Endocrine disruption is defined as the perturbation of the endocrine system, which includes disruption of nuclear hormone receptor signalling. Peroxisome proliferator-activated receptors (PPARs) represent a family of nuclear receptors that has not yet been carefully studied with regards to endocrine disruption, despite the fact that PPARs are known to be important targets for xenobiotics. Here we report a first comprehensive approach aimed at defining the mechanistic basis of PPAR disruption focusing on one chemical, the plasticizer monethylhexyl phthalate (MEHP), but using a variety of methodologies and models. We used mammalian cells and a combination of biochemical and live cell imaging techniques to show that MEHP binds to PPAR gamma and selectively regulates interactions with coregulators. Micro-array experiments further showed that this selectivity is translated at the physiological level during adipocyte differentiation. In that context, MEHP functions as a selective PPAR modulator regulating only a subset of PPAR gamma target genes compared to the action of a full agonist. We also explored the action of MEHP on PPARs in an aquatic species, Xenopus laevis, as many xenobiotics are found in aquatic ecosystems. In adult males, micro-array data indicated that MEHP influences liver physiology, possibly through a cross-talk between PPARs and estrogen receptors (ER). In early Xenopus laevis embryos, we showed that PPAR beta/delta exogenous activation by an agonist or by MEHP affects development. Taken together our results widen the concept of endocrine disruption by pinpointing PPARs as key factors in that process.

Differentiating schizoaffective and bipolar I disorder in first-episode psychotic mania.

OBJECTIVE: This study aims to differentiate schizoaffective disorder (SAD) and bipolar-I-disorder (BD) in first-episode psychotic mania (FEPM). METHODS: All 134 patients from an epidemiological first-episode psychosis cohort (N=786) with FEPM and an 18-month follow-up final diagnosis of SAD (n=36) or BD (n=98) were assessed with respect to pre-treatment, baseline and outcome differences. Second, patients with baseline BD who shifted (shifted BD) or did not shift to SAD (stable BD) over the follow-up period were compared regarding pre-treatment and baseline differences. RESULTS: SAD patients displayed a significantly longer duration of untreated psychosis (DUP; effect size r=0.35), a higher illness-severity at baseline (r=0.20) and more traumatic events (Cramer-V=0.19). SAD patients displayed a significantly higher non-adherence rate (Cramer-V=0.19); controlling for time in treatment and respective baseline scores, SAD patients had significantly worse illness severity (CGI-S; partial η(2)=0.12) and psychosocial functioning (GAF; partial η(2)=0.07) at 18-months, while BD patients were more likely to achieve remission of positive symptoms (OR=4.9, 95% CI=1.8-13.3; p=0.002) and to be employed/occupied (OR=7.7, 95% CI=2.4-24.4, p=0.001). The main discriminator of stable and shifted BD was a longer DUP in patients shifting from BD to SAD. CONCLUSIONS: It is difficult to distinguish BD with psychotic symptoms and SAD in patients presenting with FEPM. Longer DUP is related to SAD and to a shift from BD to SAD. Compared to BD, SAD had worse outcomes and higher rates of non-adherence with medication. Despite these differences, both diagnostic groups need careful dimensional assessment and monitoring of symptoms and functioning in order to choose the right treatment.

Budd-Chiari syndrome due to prothrombotic disorder: mid-term patency and efficacy of endovascular stents.

Our objective was to evaluate efficacy and patency of metallic stent placement for symptomatic Budd-Chiari syndrome (BCS) due to prothrombotic disorders. Eleven patients with proved BCS due to prothrombotic disorders were referred for endovascular treatment because of refractory ascites (n=9), abdominal pain (n=8), jaundice (n=6), and/or gastrointestinal bleeding (n=4). Stents were inserted for stenosed hepatic vein (n=7), inferior vena cava (n=2), or mesenterico-caval shunt (n=2). Clinical efficacy and stent patency was evaluated by clinical and Doppler follow-up. After a mean follow-up of 21 months, 6 patients had fully patent stents without reintervention (primary stent patency: 55%). Two patients with hepatic vein stenosis had stent thrombosis and died 4 months after procedure. Restenosis occurred in 3 cases (2 hepatic vein and 1 mesenterico-caval shunt stenosis) and were successfully treated by balloon angioplasty (n=2) and addition of new stents (n=1) leading to a 82% secondary stent patency. Of 9 patients with patent stent, 7 were asymptomatic (77%) at the end of the study. Stent placement is a safe and effective procedure to control of symptomatic BCS. Prothrombotic disorder does not seem to jeopardize patency in anticoagulated patients.

Regulation of sodium transport in the cortical collecting duct : physiological role of GILZ in vitro and in vivo : characterisation of Na+ transport in the mCCDcl1 cell line

SUMMARY Regulation of sodium excretion by the kidney is a key mechanism in the long term regulation of blood pressure, and when altered it constitutes a risk factor for the appearance of arterial hypertension. Aldosterone, which secretion depends upon salt intake in the diet, is a steroid hormone that regulates sodium reabsorption in the distal part of the nephron (functional unit of the kidney) by modulating gene transcription. It has been shown that it can act synergistically with the peptidic hormone insulin through the interaction of their signalisation pathways. Our work consisted of two distinct parts: 1) the in vitro and in vivo characterisation of Glucocorticoid-Induced Leucine Zipper (GILZ) (an aldosterone-induced gene) mechanism of action; 2) the in vitro characterisation of insulin mechanism of action and its interaction with aldosterone. GILZ mRNA, coded by the TSC22D3 gene, is strongly induced by aldosterone in the cell line of principal cells of the cortical collecting duct (CCD) mpkCCDc14, suggesting that GILZ is a mediator of aldosterone response. Co-expression of GILZ and the amiloride-sensitive epithelial sodium channel ENaC in vitro in the Xenopus oocyte expression system showed that GILZ has no direct effect on the ENaC-mediated Na+ current in basal conditions. To define the role of GILZ in the kidney and in other organs (colon, heart, skin, etc.), a conditional knock-out mouse is being produced and will allow the in vivo study of its role. Previous data showed that insulin induced a transepithelial sodium transport at supraphysiological concentrations. Insulin and the insulin-like growth factor 1 (IGF-1) are able to bind to each other receptor with an affinity 50 to 100 times lower than to their cognate receptor. Our starting hypothesis was that the insulin effect observed at these supraphysiological concentrations is actually mediated by the IGF receptor type 1 (IGF-1R). In a new cell line that presents all the characteristics of the principal cells of the CCD (mCCDc11) we have shown that both insulin and IGF-1 induce a physiologically significant increase of Na+ transport through the activation of IGF-1R. Aldosterone and insulin/IGF-1 have an additive effect on Na+ transport, through the activation of the PI3-kinase (PI3-K) pathway and the phosphorylation of the serum- and glucocorticoid-induced kinase 1 (Sgk1) by the IGF-1R, and the induction of Sgk1 expression by aldosterone. Thus, Sgk1 integrates IGF-1/insulin and aldosterone effects. We suggest that IGF-1 is physiologically relevant in the modulation of sodium balance, while insulin can only regulate Na+ transport at supraphysiological conditions. Both hormones would bind to the IGF-1R and induce Na+ transport by activating the PI3-K PDK1/2 - Sgk1 pathway. We have shown for the first time that Sgk1 is expressed and phosphorylated in principal cells of the CCD in basal conditions, although the mechanism that maintains Sgk1 phosphorylation is not known. This new role for IGF-1 suggests that it could be a salt susceptibility gene. In effect, IGF-1 stimulates Na+ and water transport in the kidney in vivo. Moreover, 35 % of the acromegalic patients (overproduction of growth hormone and IGF-1) are hypertensives (higher proportion than in normal population), and genetic analysis suggest a link between the IGF-1 gene locus and blood pressure. RÉSUMÉ La régulation de l'excrétion rénale de sodium (Na+) joue un rôle principal dans le contrôle à long terme de la pression sanguine, et ses altérations constituent un facteur de risque de l'apparition d'une hypertension artérielle. L'aldosterone, dont la sécrétion dépend de l'apport en sel dans la diète, est une hormone stéroïdienne qui régule la réabsorption de Na+ dans la partie distale du nephron (unité fonctionnelle du rein) en contrôlant la transcription de gènes. Elle peut agir de façon synergistique avec l'hormone peptidique insuline, probablement via l'interaction de leurs voies de signalisation cellulaire. Le but de notre travail comportait deux volets: 1) caractériser in vitro et in vivo le mécanisme d'action du Glucocorticoid Induced Leucine Zipper (GILZ) (un gène induit par l'aldosterone); 2) caractériser in vitro le mécanisme d'action de l'insuline et son interaction avec l'aldosterone. L'ARNm de GILZ, codé par le gène TSC22D3, est induit par l'aldosterone dans la lignée cellulaire de cellules principales du tubule collecteur cortical (CCD) mpkCCDc14, suggérant que GILZ est un médiateur potentiel de la réponse à l'aldosterone. La co-expression in vitro de GILZ et du canal à Na+ sensible à l'amiloride ENaC dans le système d'expression de l'oocyte de Xénope a montré que GILZ n'a pas d'effet sur les courants sodiques véhiculées par ENaC en conditions basales. Une souris knock-out conditionnelle de GILZ est en train d'être produite et permettra l'étude in vivo de son rôle dans le rein et d'autres organes. Des expériences préliminaires ont montré que l'insuline induit un transport transépithelial de Na+ à des concentrations supraphysiologiques. L'insuline et l'insulin-like growth factor 1 (IGF-1) peuvent se lier à leurs récepteurs réciproques avec une affinité 50 à 100 fois moindre qu'à leur propre récepteur. Nous avons donc proposé que l'effet de l'insuline soit médié par le récepteur à l'IGF type 1 (IGF-1R). Dans une nouvelle lignée cellulaire qui présente toutes les caractéristiques des cellules principales du CCD (mCCDc11) nous avons montré que les deux hormones induisent une augmentation physiologiquement significative du transport du Na+ par l'activation des IGF-1 R. Aldosterone et insuline/IGF-1 ont un effet additif sur le transport de Na+, via l'activation de la voie de la PI3-kinase et la phosphorylation de la serum- and glucocorticoid-induced kinase 1 (Sgk1) par l'IGF-1R, dont l'expression est induite par l'aldosterone. Sgk1 intègre les effets de l'insuline et l'aldosterone. Nous proposons que l'IGF-1 joue un rôle dans la modulation physiologique de la balance sodique, tandis que l'insuline régule le transport de Na+ à des concentrations supraphysiologiques. Les deux hormones agissent en se liant à l'IGF-1R et induisent le transport de Na+ en activant la cascade de signalisation PI3-K - PDK1/2 - Sgk1. Nous avons montré pour la première fois que Sgk1 est exprimée et phosphorylée dans des conditions basales dans les cellules principales du CCD, mais le mécanisme qui maintient sa phosphorylation n'est pas connu. Ce nouveau rôle pour l'IGF-1 suggère qu'il pourrait être un gène impliqué de susceptibilité au sel. Aussi, l'IGF-1 stimule le transport rénal de Na+ in vivo. De plus, 35 % des patients atteints d'acromégalie (surproduction d'hormone de croissance et d'IGF-1) sont hypertensifs (prévalence plus élevée que la population normale), et des analyses génétiques suggèrent un lien entre le locus du gène de l'IGF-1 et la pression sanguine. RÉSUMÉ GRAND PUBLIC Nos ancêtres se sont génétiquement adaptés pendant des centaines de millénaires à un environnement pauvre en sel (chlorure de sodium) dans la savane équatoriale, où ils consommaient moins de 0,1 gramme de sel par jour. On a commencé à ajouter du sel aux aliments avec l'apparition de l'agriculture (il y a 5000 à 10000 années), et aujourd'hui une diète omnivore, qui inclut des plats préparés, contient plusieurs fois la quantité de sodium nécessaire pour notre fonction physiologique normale (environ 10 grammes par jour). Le corps garde sa concentration constante dans le sang en s'adaptant à une consommation très variable de sel. Pour ceci, il module son excrétion soit directement, soit en sécrétant des hormones régulatrices. Le rein joue un rôle principal dans cette régulation puisque l'excrétion urinaire de sel change selon la diète et peut aller d'une quantité dérisoire à plus de 36 grammes par jour. L'attention qu'on prête au sel est liée à sa relation avec l'hypertension essentielle. Ainsi, le contrôle rénal de l'excrétion de sodium et d'eau est le principal mécanisme dans la régulation de la pression sanguine, et une ingestion excessive de sel pourrait être l'un des facteurs-clé déclenchant l'apparition d'un phénotype hypertensif. L'hormone aldosterone diminue l'excrétion de sodium par le rein en modulant l'expression de gènes qui pourraient être impliqués dans la sensibilité au sel. Dans une lignée cellulaire de rein l'expression du gène TSC22D3, qui se traduit en la protéine Glucocorticoid Induced Leucine Zipper (GILZ), est fortement induite par l'aldosterone. Ceci suggère que GILZ est un médiateur potentiel de l'effet de l'aldosterone, et pourrait être impliqué dans la sensibilité au sel. Pour analyser la fonction de GILZ dans le rein plusieurs approches ont été utilisées. Par exemple, une souris dans laquelle GILZ est spécifiquement inactivé dans le rein est en train d'être produite et permettra l'étude du rôle de GILZ dans l'organisme. De plus, on a montré que GILZ, en conditions basales, n'a pas d'effet direct sur la protéine transportant le sodium à travers la membrane des cellules, le canal sodique épithélial ENaC. On a aussi essayé de trouver des protéines qui interagissent directement avec GILZ utilisant une technique appelée du « double-hybride dans la levure », mais aucun candidat n'a émergé. Des études ont montré que, à de hautes concentrations, l'insuline peut aussi diminuer l'excrétion de sodium. A ces concentrations, elle peut activer son récepteur spécifique, mais aussi le récepteur d'une autre hormone, l'Insulin-Like Growth Factor 1 (IGF-1). En plus, l'infusion d'IGF-1 augmente la rétention rénale de sodium et d'eau, et des mutations du gène codant pour l'IGF-1 sont liées aux différents niveaux de pression sanguine. On a utilisé une nouvelle lignée cellulaire de rein développée dans notre laboratoire, appelée mCCDc11, pour analyser l'importance relative des deux hormones dans l'induction du transport de sodium. On a montré que les deux hormones induisent une augmentation significative du transport de sodium par l'activation de récepteurs à l'IGF-1 et non du récepteur à l'insuline. On a montré qu'à l'intérieur de la cellule leur activation induit une augmentation du transport sodique par le biais du canal ENaC en modifiant la quantité de phosphates fixés sur la protéine Serumand Glucocorticoid-induced Kinase 1 (Sgk1). On a finalement montré que l'IGF-1 et l'aldosterone ont un effet additif sur le transport de sodium en agissant toutes les deux sur Sgk1, qui intègre leurs effets dans le contrôle du transport de sodium dans le rein.

Physiological analysis of leaf senescence of two rice cultivars with different yield potential

The objective of this work was to evaluate the physiological changes that occur in different leaves during the early and late grain-filling stages of two rice genotypes (Oryza sativa subsp. indica , BRS Pelota cultivar, and O. sativa subsp. japonica , BRS Firmeza cultivar), which present differences in grain yield potential. The plants were cultivated in greenhouse. Pigment content, chlorophyll fluorescence, electron transport and oxygen evolution rate were determined in the grain-filling stage, from the first to the forth leaf (top to bottom). Pigment content, photochemical efficiency of photosystem II and electron transport decreased significantly according to the position of leaves in 'BRS Pelota'. The BRS Firmeza cultivar shows higher pigment content and higher activity of the photosynthetic apparatus in comparison to 'BRS Pelota' during the grain-filling stage.

Physiological requirements in triathlon

This article aims to present the current knowledge on physiological requirements in Olympic distance and Ironman triathlon. Showing the data available from a "traditional point of view" (aerobic power, anaerobic threshold, heart rate, running economy) and from a "contemporary" point of view (V̇O2 kinetics), it emphasises where we are currently and the areas that remain unknown.

Effectiveness of psychotropic medications in the maintenance phase of bipolar disorder:a meta-analysis of randomized controlled trials

The purpose of this meta-analysis was to examine the efficacy of maintenance treatments for bipolar disorder. Placebo-controlled or active comparator bipolar maintenance clinical trials of ≥6 months' duration with at least 15 patients/treatment group were identified using Medline, EMBASE, clinicaltrials.gov, and Cochrane databases (1993 to July 2010). The main outcome measure was relative risk for relapse for patients in remission. Twenty trials (5,364 patients) were identified. Overall, lithium and quetiapine were the most studied agents (eight and five trials, respectively). The majority of studies included patients who had previously responded to treatment for an acute episode. All interventions, with the exception of perphenazine+mood stabilizer, showed a relative risk for manic/mixed or depressive relapse below 1.0, although there was variation in the statistical significance of the findings vs. placebo. No monotherapy was associated with a significantly reduced risk for both manic/mixed and depressed relapse. Of the combination treatments, only quetiapine+lithium/divalproex, was associated with a significantly reduced risk vs. comparator (placebo+lithium/valproate) for relapse at both the manic/mixed and depressed poles of bipolar illness. Limitations for the analysis include differences in study durations and definitions of relapse. In conclusion, available maintenance therapies show considerable variation in efficacy. The efficacy of lithium and divalproex has been confirmed, but newer therapies, such as a number of atypical antipsychotics were also shown to be effective in bipolar disorder. Efficacy of all maintenance interventions needs to be balanced against the safety and tolerability profiles of individual agents.

Efficacy and safety of aripiprazole in the treatment of bipolar disorder: a systematic review.

Abstract BACKGROUND: The current article is a systematic review concerning the efficacy and safety of aripiprazole in the treatment of bipolar disorder. METHODS: A systematic Medline and repositories search concerning the usefulness of aripiprazole in bipolar disorder was performed, with the combination of the words 'aripiprazole' and 'bipolar'. RESULTS: The search returned 184 articles and was last updated on 15 April 2009. An additional search included repositories of clinical trials and previous systematic reviews specifically in order to trace unpublished trials. There were seven placebo-controlled randomised controlled trials (RCTs), six with comparator studies and one with add-on studies. They assessed the usefulness of aripiprazole in acute mania, acute bipolar depression and during the maintenance phase in comparison to placebo, lithium or haloperidol. CONCLUSION: Aripiprazole appears effective for the treatment and prophylaxis against mania. The data on bipolar depression are so far negative, however there is a need for further study at lower dosages. The most frequent adverse effects are extrapyramidal signs and symptoms, especially akathisia, without any significant weight gain, hyperprolactinaemia or laboratory test changes.

Class effect of pharmacotherapy in bipolar disorder: fact or misbelieff?

BACKGROUND: Anecdotal reports suggests that most clinicians treat medications as belonging to a class with regard to all therapeutic indications; this means that the whole 'class' of drugs is considered to possesses a specific therapeutic action. The present article explores the possible existence of a true 'class effect' for agents available for the treatment of bipolar disorder. METHODS: We reviewed the available treatment data from randomized controlled trials (RCTs) and explored 16 'agent class'/'treatment issue' cases for bipolar disorder. Four classes of agents were examined: first-generation antipsychotics (FGAs), second-generation antipsychotics (SGAs), antiepileptics and antidepressants, with respect to their efficacy on four treatment issues of bipolar disorder (BD) (acute mania, acute bipolar depression, maintenance against mania, maintenance against depression). RESULTS: From the 16 'agent class'/' treatment issue' cases, only 3 possible class effects were detected, and they all concerned acute mania and antipsychotics. Four effect cases have not been adequately studied (FGAs against acute bipolar depression and in maintenance protection from depression, and antidepressants against acute mania and protection from mania) and they all concern treatment cases with a high risk of switching to the opposite pole, thus research in these areas is poor. There is no 'class effect' at all concerning antiepileptics. CONCLUSIONS: The available data suggest that a 'class effect' is the exception rather than the rule in the treatment of BD. However, the possible presence of a 'class effect' concept discourages clinicians from continued scientific training and reading. Focused educational intervention might be necessary to change this attitude.

Physiological indicators of stress in gestating sows under different cooling systems

The objective of this work was to determine physiological stress markers, neutrophil:lymphocyte ratio (N/L) and corticoid concentrations, in gestating sows under different cooling systems. A sprinkling cooling system (SS) and a system based on fan-assisted evaporative cellulose pad (PS) were used. SS showed higher N/L ratio (1.095) than PS (0.850). Corticoid concentrations showed high variability. Corticosteroids are more efficient short-term stress indicators while N/L ratio is a good medium and long-term stress indicator. According to N/L ratio, gestating sows under PS benefit from a higher level of welfare.

Hot spots for diversity of Magnaporthe oryzae physiological races in irrigated rice fields in Brazil

The objective of this work was to evaluate the Magnaporthe oryzae pathotype diversity in new commercial irrigated rice fields in the Araguaia River Valley, state of Tocantins, Brazil. The causal agent of rice blast has heavily affected rice production in the region. Despite the efforts of breeding programs, blast resistance breakdown has been recorded shortly after the release of new resistant cultivars developed for the region. Among the causes of resistance breakage is the capacity of the fungus to rapidly develop new pathotypes. A sample of 479 M. oryzae monosporic isolates was obtained and tested using the international rice blast differential set. Isolate collections were made in small areas designed as trap nurseries and in scattered sites in their vicinity. Analysis of 250 M. oryzae isolates from three trap nurseries indicated the presence of 45 international M. oryzae races belonging to seven pathotype groups (IA-IG). In the isolates tested, 61 M. oryzae pathotypes belonging to all but the IH group were detected. The new areas of irrigated rice in the Araguaia River Valley have the highest diversity of M. oryzae pathotypes reported so far in Brazil.

Characterization of the molecular mechanisms of insulin exocytosis and of their adaptation to physiopathological conditions

Résumé large public Le glucose est une source d'énergie essentielle pour notre organisme, indispensable pour le bon fonctionnement des cellules de notre corps. Les cellules β du pancréas sont chargées de réguler l'utilisation du glucose et de maintenir la glycémie (taux de glucose dans le sang) à un niveau constant. Lorsque la glycémie augmente, ces dernières sécrètent l'insuline, une hormone favorisant l'absorption, l'utilisation et le stockage du glucose. Une sécrétion insuffisante d'insuline provoque une élévation anormale du taux de glucose dans le sang (hyperglycémie) et peut mener au développement du diabète sucré. L'insuline est sécrétée dans le sang par un mécanisme particulier appelé exocytose. Une meilleure compréhension de ce mécanisme est nécessaire dans l'espoir de trouver des nouvelles thérapies pour traiter les 170 millions de personnes atteintes de diabète sucré à travers le monde. L'implication de diverses protéines, comme les SNAREs ou Rabs a déjà été démontrée. Cependant leurs mécanismes d'action restent, à ce jour, peu compris. De plus, l'adaptation de la machinerie d'exocytose à des conditions physiopathologiques, comme l'hyperglycémie, est encore à élucider. Le but de mon travail de thèse a été de clarifier le rôle de deux protéines, Noc2 et Tomosyn, dans l'exocytose ; puis de déterminer les effets d'une exposition prolongée à un taux élevé de glucose sur l'ensemble des protéines de la machinerie d'exocytose. Noc2 est un partenaire potentiel de deux Rabs connues pour leur implication dans les dernières étapes de l'exocytose, Rab3 et Rab27. Grâce à l'étude de différents mutants de Noc2, j'ai montré que l'interaction avec Rab27 permet à la protéine de s'associer avec les organelles de la cellule β contenant l'insuline. De plus, en diminuant sélectivement l'expression de Noc2, j'ai déterminé l'importance de cette protéine pour le bon fonctionnement du processus d'exocytose et le relâchement de l'insuline. Quant à Tomosyn, une protéine interagissant avec les protéines SNAREs, j'ai démontré son importance dans la sécrétion d'insuline en diminuant de manière sélective son expression dans les cellules β. Ensuite, grâce à une combinaison d'approches moléculaires et de microscopie, j'ai mis en évidence le rôle de Tomosyn dans les dernières étapes de l'exocytose. Enfin, puisque la sécrétion d'insuline est diminuée lors d'une hyperglycémie prolongée, j'ai analysé l'adaptation de la machinerie d'exocytose à ces conditions. Ceci m'a permis de découvrir que l'expression de quatre protéines essentielles pour le processus d'exocytose, Noc2, Rab3, Rab27 et Granuphilin, est fortement diminuée lors d'une hyperglycémie chronique. L'ensemble de ces données met en évidence l'importance de Noc2 et Tomosyn dans la sécrétion d'insuline. L'inhibition, par un taux élevé de glucose, de l'expression de Noc2 et d'autres protéines indispensables pour l'exocytose suggère que ce phénomène pourrait contribuer au développement du diabète sucré. Résumé L'exocytose d'insuline, en réponse au glucose circulant dans le sang, est la fonction principale de la cellule β. Celle-ci permet de stabiliser le taux de glucose sanguin (glycémie). Le diabète de type 2 est caractérisé par une glycémie élevée due, principalement, à un défaut de sécrétion d'insuline en réponse au glucose. La compréhension des mécanismes qui contrôlent l'exocytose d'insuline est essentielle pour clarifier les causes du diabète sucré. Plusieurs composants impliqués dans ce processus ont été identifiés. Ceux-ci incluent les SNAREs Syntaxin-1, VAMP2 et SNAP25 et les GTPases Rab3 et Rab27 qui jouent un rôle dans les dernières étapes de l'exocytose. Pendant mon travail de thèse, j'ai étudié le rôle de Noc2, un des partenaires de Rab3 et Rab27, dans l'exocytose d'insuline. Nous avons déterminé que Noc2 s'associe aux granules de sécrétion d'insuline grâce à son interaction avec Rab27. La diminution de l'expression de Noc2 dans la lignée cellulaire β INS-1E, par ARN interférence, influence négativement la sécrétion d'insuline stimulée par différents sécrétagogues et prouve que cette protéine Noc2 est essentielle pour l'exocytose d'insuline. L'interaction avec Munc13, une protéine impliquée dans l'arrimage des vésicules, suggère que Noc2 participe au recrutement des granules d'insuline à la membrane plasmique. Ensuite, j'ai analysé l'adaptation de la machinerie d'exocytose à des concentrations supraphysiologiques de glucose. Le niveau d'expression de Rab3 et Rab27 et de leurs effecteurs Granuphilin/S1p4 et Noc2 est fortement diminué par une exposition prolongée des cellules β à haut glucose. L'effet observé est en relation avec l'induction de l'expression de ICER, un facteur de transcription surexprimé dans des conditions d'hyperglycémie et également dans des modèles génétiques de diabète de type 2. La surexpression de ICER dans des cellules INS-1E diminue l'expression de Rab3, Rab27, Granuphilin/Slp4 et Noc2 et par conséquent l'exocytose d'insuline. Ainsi, l'induction de ICER, après une exposition prolongée à haut glucose, régule négativement l'expression de protéines essentielles pour l'exocytose et altère la sécrétion d'insuline. Ce mécanisme pourrait contribuer au dysfonctionnement de l'exocytose d'insuline dans le diabète de type 2. Dans la dernière partie de ma thèse, j'ai investigué le rôle de la protéine Tomosyn-1 dans la formation du complexe SNARE. Cette protéine a une forte affinité pour Syntaxin-1 et contient un domaine SNARE. Tomosyn-1 est concentrée dans les régions cellulaires enrichies en granules de sécrétion. La diminution sélective de l'expression de Tomosyn-1 induit une réduction de l'exocytose stimulée par différents sécrétagogues. Cet effet est dû à un défaut de fusion des granules avec la membrane plasmique. Ceci nous indique que Tomosyn-1 intervient dans une phase importante de la préparation des vésicules à la fusion, qui est nécessaire à l'exocytose. Abstract: Insulin exocytosis from pancreatic β-cells plays a central role in blood glucose homeostasis. Diabetes mellitus is a complex metabolic disorder characterized by secretory dysfunctions in pancreatic β-cells and release of amounts of insulin that are inappropriate to maintain blood glucose concentration within normal physiological ranges. To define the causes of β-cell failure a basic understanding of the molecular mechanisms that control insulin exocytosis is essential. Some of the molecular components involved in this process have been identified, including the SNARE proteins VAMP2, Syntaxin-1 and SNAP25 and the two GTPases, Rab3 and Rab27, that regulate the final steps of insulin secretion. I first investigated the role of Noc2, a potential Rab3 and Rab27 partner, in insulin secretion. I found that Noc2 associates with Rab27 and is recruited by this GTPase on insulin- containing granules. Silencing of the Noc2 gene by RNA interference led to a strong impairment in the capacity of the β-cell line INS-1E to respond to secretagogues, indicating that appropriate levels of the protein are essential for insulin exocytosis. I also showed that Noc2 interacts with Munc13, a protein that controls vesicle priming, suggesting a possible involvement of Noc2 in the recruitment of secretory granules at the plasma membrane. In the second part of my thesis, I investigated the adaptation of the molecular machinery of exocytosis to physiopathological conditions. I found that the expression of Rab3, Rab27 and of their effectors Granuphilin/Slp4 and Noc2 is dramatically decreased by chronic exposure of β-ce1ls to supraphysiological glucose levels. The observed glucotoxic effect is a consequence of the induction of ICER, a transcriptional repressor that is increased by prolonged hyperglycemia and in genetic models of type 2 diabetes. Overexpression of ICER reduced Granuphilin, Noc2, Rab3 and Rab27 levels and inhibited exocytosis. These results suggest that the presence of inappropriate levels of ICER diminishes the expression of a group of proteins essential for exocytosis and contributes to defective insulin release in type 2 diabetes. In the last part of my thesis, I focused my attention on the role of Tomosyn-1, a Syntaxin-1 binding protein possessing a SNARE-like motif, in the control of SNARE complex assembly. I found that Tomosyn-1 is concentrated in cellular compartments enriched in insulin-containing secretory granules. Silencing of Tomosyn-1 did not affect the number of secretory granules docked at the plasma membrane but decreased their release probability, resulting in a reduction in stimulus-induced insulin exocytosis. These findings suggest that Tomosyn-1 is involved in a post-docking event that prepares secretory granules for fusion and is necessary to sustain exocytosis in response to insulin secretagogues.

Life events in conversion disorder: Role of timing and nature of events

Aims: To compare the frequency of life events in the year preceding illness onset in a series of Conversion Disorder (CD) patients, with those of a matched control group and to characterize the nature of those events in terms of "escape" potential. Traditional models of CD hypothesise that relevant stressful experiences are "converted" into physical symptoms to relieve psychological pressure, and that the resultant disability allows "escape" from the stressor, providing some advantage to the individual. Methods: The Life Events and Difficulties Schedule (LEDS) is a validated semi-structured interview designed to minimise recall and interviewer bias through rigorous assessment and independent rating of events. An additional "escape" rating was developed. Results: In the year preceding onset in 25 CD patients (mean age 38.9 years ± 8) and a similar matched period in 13 controls (mean age 36.2 years ± 10), no significant difference was found in the proportion of subjects having ≥ 1 severe event (CD 64%, controls 38%; p=0.2). In the last month preceding onset, a higher number of patients experienced ≥1 severe events than controls (52% vs 15%, odds ratio 5.95 (CI: 1.09-32.57)). Patients were twice as much more likely to have a severe escape events than controls, in the month preceding onset (44% vs 7%, odds ratio 9.43 (CI: 1.06-84.04). Conclusion: Preliminary data from this ongoing study suggest that the time frame (preceding month) and the nature ("escape") of the events may play an important role in identifying key events related to CD onset.

Leaf morphological and physiological responses of Quercus aquifolioides along an altitudinal gradient

Abstract