Calcium entry via TRPV1 but not ASICs induces neuropeptide release from sensory neurons

Inflammatory mediators induce neuropeptide release from nociceptive nerve endings and cell bodies, causing increased local blood flow and vascular leakage resulting in edema. Neuropeptide release from sensory neurons depends on an increase in intracellular Ca2+ concentration. In this study we investigated the role of two types of pH sensors in acid-induced Ca2+ entry and neuropeptide release from dorsal root ganglion (DRG) neurons. The transient receptor potential vanilloid 1 channel (TRPV1) and acid-sensing ion channels (ASICs) are both H+-activated ion channels present in these neurons, and are therefore potential pH sensors for this process. We demonstrate with in situ hybridization and immunocytochemistry that TRPV1 and several ASIC subunits are co-expressed with neuropeptides in DRG neurons. Activation of ASICs and of TRPV1 led to an increase in intracellular Ca2+ concentration. While TRPV1 has a high Ca2+ permeability and allows direct Ca2+ entry when activated, we show here that ASICs of DRG neurons mediate Ca2+ entry mostly by depolarization-induced activation of voltage-gated Ca2+ channels and only to a small extent via the pore of Ca2+-permeable ASICs. Extracellular acidification led to release of the neuropeptide calcitonin gene-related peptide from DRG neurons. The pH dependence and the pharmacological profile indicated that TRPV1, but not ASICs, induced neuropeptide secretion. In conclusion, this study shows that although both TRPV1 and ASICs mediate Ca2+ influx, TRPV1 is the principal sensor for acid-induced neuropeptide secretion from sensory neurons.

A study of the translational regulation exerted by some neuroactive substances on the expression of the monocarboxylate transporter MCT2 in cultured cortical neurons

Summary of the thesis Glucose has been considered the major, if not the exclusive, energy substrate for the brain. But under certain conditions other substrates, namely monocarboxylates (lactate, pyruvate, and ketone bodies), can contribute significantly to satisfy brain energy demands. These monocarboxylates need to be transported across the blood brain barrier as well as out of astrocytes into the extracellular space and taken up into neurons. It has been shown that monocarboxylates are transported by a family of proton-linked transporters called monocarboxylate transporters (MCTs). In the central nervous system, MCT2 is the predominant neuronal form and little is known about the regulation of its expression. The neurotransmitter noradrenaline (NA) was shown previously to enhance the expression of MCT2 in cultured cortical neurons via a translational mechanism. Here, we demonstrate that two other substances, namely, insulin and IGF-1 enhance MCT2 protein expression in cultured mouse cortical neurons in a time- and concentrationdependent manner without affecting MCT2 mRNA levels. This result confirmed that MCT2 protein expression is translationally regulated and extend the observation to different types of neuroactive substances. Then we sought to determine by which signaling pathway(s) NA, insulin and IGF-1 can induce MCT2 protein expression. First, we observed by Western blot that all three substances cause activation of the MAP kinase ERK as well as the kinase Akt via their phosphorylation. Moreover, the mTOR/S6K pathway which is known to play an important role in translation initiation regulation was also strongly stimulated by all three substances. Second, we sought to determine the implication of these signaling pathways on the NA-, insulin- and IGF-1-induced enhancement of MCT2 protein expression and used specific inhibitors of these signaling pathways. We observed that the Pia kinase and mTOR inhibitors LY294002 and rapamycin respectively, strongly prevent the enhancement. of MCT2 expression caused by either NA, insulin ar IGF-1. In contrast, the MEK inhibitor PD98059 and the p38 MAP kinase inhibitor SB202190 had only a slight effect on the enhancement of MCT2 expression in all three cases. These results suggest that NA, insulin and IGF-1 regulate MCT2 protein expression by a common mechanism most likely involving the Akt/PKB pathway and translational activation via mTOR. In conclusion, considering the roles of NA, insulin and IGF-1 in synaptic plasticity, the tight translational regulation of MCT2 expression by these substances may represent a common mechanism through which supply of potentiated synapses with nonglucose energy substrates can be adapted to the level of activity. Résumé du travail de thèse Le glucose représente le substrat énergétique majeur pour le cerveau. Cependant, dans certaines conditions physiologiques ou pathologiques, le cerveau a la capacité d'utiliser des substrats énergétiques appartenant à la classe des monocarboxylates (lactate, pyruvate et corps cétoniques) afin de satisfaire ses besoins énergétiques. Ces monocarboxylates doivent être transportés à travers la barrière hématoencéphalique mais aussi hors des astrocytes vers l'espace extracellulaire puis re-captés par les neurones. Leur transport est assuré par une famille de transporteurs spécifiques, protons-dépendants, appelés transporteurs aux monocarboxylates (MCTs). Dans le système nerveux central, les neurones expriment principalement l'isoforme MCT2 mais peu d'informations sont disponibles concernant la régulation de son expression. Il a été montré que le neurotransmetteur noradrénaline (NA) augmente l'expression de MCT2 dans les cultures de neurones corticaux de souris par le biais d'un mécanisme de régulation traductionnel. La présente étude nous a permis de démontrer que deux autres substances, l'insuline et 17GF-1, induisent une augmentation de la protéine MCT2 dans ces mêmes cultures selon un décours temporel et une gamme de concentrations particulière. Etonnamment, aucun changement n'a été observé concernant les niveaux d'ARNm de MCT2. Ce résultat .confirme que la protéine MCT2 est régulée de manière traductionnelle et révèle que différentes substances neuro-actives peuvent réguler l'expression de MCT2. Compte tenu de ces observations, nous avons voulu déterminer par quelle(s) voie(s) de signalisation la NA, l'insuline et l'IGF-1 exercent leur effet sur l'expression de MCT2. Dans un premier temps, nous avons pu observer par Western blot que ces trois substances activent la MAP kinase ERK ainsi que la kinase Akt via leur phasphorylation. De plus, la voie mTOR/S6K, connue pour son implication dans la régulation de l'initiation de la traduction est aussi fortement activée par ces trois substances. Dans un second temps, nous avons voulu déterminer I implication de chacune de ces voies de signalisation dans l'augmentation de l'expression de la protéine MCT2 observée après stimulation à la NA, à l'insuline et à l'IGF-1. Pour ce faire, nous avons utilisé des inhibiteurs spécifiques de chacune de ces voies. (Vous avons observé que les inhibiteurs des voies PI3 kinase et mTOR (LY294002 et rapamycin respectivement), prévenaient fortement l'augmentation de l'expression de MCT2 induite par la NA, l'insuline ou (IGF-1. A l'inverse, les inhibitions de la MAP kinase .kinase MEK ainsi que de la MAP kinase p38 (par l'utilisation des inhibiteurs spécifiques PD98059 et SB202190 respectivement) n'ont eu qu'un léger effet dans ces mêmes conditions. Ces résultats suggèrent que la NA, 'l'insuline et I~GF-1 régulent l'expression de la protéine MCT2 par un mécanisme commun impliquant probablement la voie Akt/PKB et l'activation de la traduction via mTOR. En conclusion, considérant l'implication de la NA, de l'insuline et de I`IGF-1 dans la plasticité synaptique, le contrôle traductionnel étroit exercé par ces substances sur l'expression de MCT2 pourrait être un moyen d'alimenter en substrats énergétiques autres que le glucose les synapses activées et également d'adapter l'approvisionnement en substrats énergétiques au niveau d'activité. Résumé « grand public » Le cerveau est un organe qui réalise des tâches complexes nécessitant un apport important en énergie. La principale source d'énergie du cerveau est le glucose. Bien que le cerveau ne représente que 2% de la masse corporelle, il consomme à lui seul plus de 25% du glucose et 20% de l'oxygène provenant de la circulation sanguine. La nécessité d'un tel apport en énergie réside dans la nature -même du fonctionnement des milliards de neurones qui utilisent des signaux électriques et chimiques pour communiquer entre eux. Hormis l'utilisation massive du glucose comme source d'énergie, le cerveau est capable de consommer d'autres substrats énergétiques dans certaines conditions physiologiques ou pathologiques. Les monocarboxylates (lactate, pyruvate et corps cétoniques) font partie de ces autres sources d'énergie. Contrairement au glucose, les monocarboxylates ne diffusent pas facilement de la circulation sanguine vers les neurones. Afin de pouvoir être consommés par les neurones, ils doivent être transportés par un système adapté. Ce sont des transporteurs appelés transporteurs aux monocarboxylates ou MCT qui permettent le passage de ces substrats énergétiques du sang vers les neurones. Le but de ce travail de thèse a été de comprendre comment est régulée l'expression de MCT2, l'un de ces transporteurs exprimé spécifiquement à la surface des neurones. Cette étude nous a permis de mettre en évidence que le neurotransmetteur noradrénaline ainsi que les hormones insuline et IGF-1 (insulinlike growth factor-1) sont capables d'induire une augmentation d'expression de MCT2 à la surface des neurones en culture. Nous avons ensuite voulu déterminer par quels mécanismes de signalisation ces substances agissent sur l'expression de MCT2. Nous avons pu observer que la surexpression de la protéine MCT2 est due à une augmentation d'activité traductionnelle (la traduction étant une des étapes qui permet la synthèse des protéines) induite par le biais d'une voie de signalisation particulière. En conclusion, lorsque la noradrénaline, l'insuline ou 17GF-1 agissent sur les neurones, la traduction de la protéine MCT2 est activée et on observe une augmentation de l'expression de MCT2. Ce mécanisme pourrait permettre d'augmenter l'apport énergétique au niveau des neurones en augmentant le nombre de transporteurs pour les substrats énergétiques que sont les monocarboxylates. D'un point de vue physiologique, cette régulation d'expression pourrait jouer un rôle primordial dans des situations d'apprentissage et de mémorisation. Sur le plan pathologique, cela pourrait permettre de prévenir les dommages causes aux neurones dans certains cas d'atteintes cérébrales.

Nevirapine vs efavirenz in virologically supressed patients: Differences in lipoprotein subclasses and inflammatory biomarkers.

Background: The interaction between lipid disturbances and inflammatory markers is not well known in patients on antiretroviral therapy (ART). As nevirapine (NVP) is associated with a better lipid profile than efavirenz (EFV), we investigated the relationships between lipid profiles, lipoprotein subclasses and inflammatory biomarkers in patients with prolonged viral suppression with either NVP or EFV and no obvious clinical inflammation. Methods: 122 clinically stable HIV-infected patients with HIV-1 RNA <20 copies longer than 6 months on NNRTI therapy were studied. 72 (59%) were on EFV and 50 (41%) on NVP. Any potentially inflammatory co-morbid diseases (concurrent viral hepatitis, diabetes, hypertension, chronic liver or renal diseases), or statin treatment, were exclusion criteria. Inflammatory biomarkers included hsCRP, LpPLA2, sCD40L, IL-6, IL-8, t-PA, MCP-1, p-selectin and VCAM-1. Lipoprotein subclass measures (VLDL, LDL, IDL and HDL particle number and size) were obtained by the use of proton nuclear magnetic resonance spectroscopy. Results: 82% were male; median age 45 years. Median CD4 count 550/μL (IQR 324). Median time since HIV diagnosis 96 months (IQR 102) and accumulated time on ART 50 months (IQR 101). Patients on NVP had higher time since HIV diagnosis (126.9 [66.7] vs 91.3 [6.6] months, p=0.008) a prolonged time on ART (89.6 [54.6] vs 62.3 [52.2] months, p=0.01) and were older (47.7 vs 40.7 years, p=0.001) than those on EFV. NVP-treated patients presented increased HDL-c (55.8 [16] vs 48.8 [10.7] mg/dL, p=0.007) and apoA1 levels (153.4 [31.9] vs 141.5 [20.5] mg/dL, p=0.02), and reduced apoB/apoA1 ratio (0.68 [0.1] vs 0.61 [0.1], p=0.003) than EFV-treated patients. No differences in inflammatory markers or lipoprotein subclasses were found between NVP and EFV. In patients with extreme lipid values (less favorable: 75th percentiles of LDL, small/dense LDLp and small HDLp, or more favorable: HDL p75 and apoB/apoA1 ratio p25), no consistent differences in inflammatory biomarkers were found. Conclusions: Patients with prolonged viral suppression on NVP present significantly higher HDL and apoA1 levels and reduced apoB/apoA1 ratios than those on EFV, but no differences were found in lipoprotein particles nor inflammatory biomarkers. Relationships between lipid parameters and inflammatory biomarkers in NNRTItreated patients are complex and do not show a linear relationship in this study.

Maladies peptiques [Progress in 2008 for acid related diseases]

The treatment of reflux disease did not change in the review period. PPI therapy remains the first line treatment and surgery the second line approach. Endoscopic anti-reflux procedures should be only performed in controlled studies. Beside the classic triple therapy, sequential treatment of Helicobacter pylori infection can today be considered as a first line therapy. PPI are effective in the prevention of gastroduodenal lesions and in the treatment of dyspeptic symptoms induced by NSAIDs treatment. Only patients younger then 65 years and without any risk factors do not need a preventive PPI prescription during classic NSAIDS treatment.

Update on basic and clinical aspects of eosinophilic oesophagitis.

The identification of a distinct syndrome, designated eosinophilic oesophagitis (EoE), with its own clinical and histopathological characteristics, was first described in the early 1990s. Meanwhile intense research has uncovered many molecular, immunological and clinical aspects of this chronic-inflammatory disorder. This article focuses exclusively on basic and clinical insights of EoE gathered during the last few years. Regarding aetiopathogenesis it has become clear that EoE is a food-triggered disease with milk and wheat as the dominant culprit food categories. However, it is still debated whether a disturbed mucosal integrity allowing allergens to cross the mucosal barrier, or changes in wheat and milk manufacturing might induce these inflammatory responses. Furthermore, basic science and clinical studies have accordingly confirmed that a chronic eosinophilic inflammation leads to a remodelling of the oesophagus with micro- and macro-morphological alterations, ending in a strictured oesophagus with impaired function. Fortunately, long-term therapeutic trials, using either topical corticosteroids or dietary allergen avoidance, have demonstrated that this sequela can be prevented or even reversed. This finding is of clinical relevance as it supports the initiation of a consistent anti-inflammatory therapy. Nevertheless, EoE is still an enigmatic disease and the long list of unanswered questions will certainly stimulate further research.

Contribution de la biomicroscopie ultrasonore au traitement conservateur des mélanomes de l'uvée antérieure [Contribution of ultrasound biomicroscopy to conservative treatment of anterior uveal melanoma]

BACKGROUND: Ultrasound Biomicroscopy (UBM) is a new ophthalmological imaging technique essentially designed for the study of the anterior eye segment. Over the last 10 months, we've evaluated its contribution to the conservative treatment of anterior uveal melanoma's by means of accelerated proton beam irradiation. MATERIAL: Using UBM, we have examined 55 cases of uveal melanoma's, whose anterior border was situated at 6 mm or less from the limbus and that were consequently treated by proton beam irradiation. RESULTS: The presumed tumoral origin was the ciliary body's pars plicata in 13 cases and the pars plana or the choroid in 42 cases, 17 of which presented a tumoral invasion of the pars plicata. A pars plana detachment anterior to or surrounding the anterior tumoral border, was present in 22 cases. The height of the tumor could only be measured by UBM if it was less than 2.5 mm. Information gathered using UBM have contributed to an improvement of the therapy plan in 32 cases. CONCLUSION: Because of the strong attenuation of the high frequency ultrasound signal, UBM can only be used for the examination of intra-ocular structures situated in direct neighbourhood to the global wall. Despite this technical limitation, ist contribution to the planning of the conservative treatment of anterior uveal melanoma's by proton beam irradiation has appeared to be considerable.

Comparison of T1 relaxation times of the neurochemical profile in rat brain at 9.4 tesla and 14.1 tesla.

Knowledge of T(1) relaxation times can be important for accurate relative and absolute quantification of brain metabolites, for sensitivity optimizations, for characterizing molecular dynamics, and for studying changes induced by various pathological conditions. (1)H T(1) relaxation times of a series of brain metabolites, including J-coupled ones, were determined using a progressive saturation (PS) technique that was validated with an adiabatic inversion-recovery (IR) method. The (1)H T(1) relaxation times of 16 functional groups of the neurochemical profile were measured at 14.1T and 9.4T. Overall, the T(1) relaxation times found at 14.1T were, within the experimental error, identical to those at 9.4T. The T(1)s of some coupled spin resonances of the neurochemical profile were measured for the first time (e.g., those of gamma-aminobutyrate [GABA], aspartate [Asp], alanine [Ala], phosphoethanolamine [PE], glutathione [GSH], N-acetylaspartylglutamate [NAAG], and glutamine [Gln]). Our results suggest that T(1) does not increase substantially beyond 9.4T. Furthermore, the similarity of T(1) among the metabolites (approximately 1.5 s) suggests that T(1) relaxation time corrections for metabolite quantification are likely to be similar when using rapid pulsing conditions. We therefore conclude that the putative T(1) increase of metabolites has a minimal impact on sensitivity when increasing B(0) beyond 9.4T.

Adjuvant intra-arterial hepatic fotemustine for high-risk uveal melanoma patients.

Uveal melanoma metastases occur most commonly in the liver. Given the 50% mortality rate in patients at high risk of developing liver metastases, we tested an adjuvant intra-arterial hepatic (i.a.h.) chemotherapy with fotemustine after proton beam irradiation of the primary tumour. We treated 22 high-risk patients with adjuvant i.a.h. fotemustine. Planned treatment duration was 6 months, starting with four weekly doses of 100 mg/m(2), and after a 5-week rest, repeated every 3 weeks. The survival of this patient group was compared with that of a 3 : 1 matched control group randomly selected from our institutional database. Half of the patients experienced > or =grade 3 hepatotoxicity (one patient developing cholangitis 8 years later). Catheter-related complications occurred in 18%. With a median follow-up of 4.6 years for the fotemustine group and 8.5 years for the control group, median overall survival was 9 years [95% confidence interval (CI) 2.2-12.7] and 7.4 years (95% CI 5.4-12.7; P=0.5), respectively, with 5-year survival rates of 75 and 56%. Treatment with adjuvant i.a.h. fotemustine is feasible. However, toxicities are important. Although our data suggest a survival benefit, it was not statistically significant. Confirming such a benefit would require a large, internationally coordinated, prospective randomized trial.

Use of an in-house approach to study the three-dimensional structures of various outer membrane proteins: structure of the alcaligin outer membrane transporter FauA from Bordetella pertussis.

Bordetella pertussis is the bacterial agent of whooping cough in humans. Under iron-limiting conditions, it produces the siderophore alcaligin. Released to the extracellular environment, alcaligin chelates iron, which is then taken up as a ferric alcaligin complex via the FauA outer membrane transporter. FauA belongs to a family of TonB-dependent outer membrane transporters that function using energy derived from the proton motive force. Using an in-house protocol for membrane-protein expression, purification and crystallization, FauA was crystallized in its apo form together with three other TonB-dependent transporters from different organisms. Here, the protocol used to study FauA is described and its three-dimensional structure determined at 2.3 A resolution is discussed.

Nouvelles stratégies thérapeutiques en oncologie ophtalmo-pédiatrique [New strategies in pediatric ophthalmic oncology]

Le rétinoblastome représente 11% de tous les cancers apparaissant pendant la première année de vie. Pour éviter les effets secondaires de la chimiothérapie systémique ou de la radiothérapie externe, de nouveaux médicaments et de nouvelles techniques de traitement focalisé ont été développés. Des voies d'administration telles la voie périoculaire (topotécan) ou la voie artérielle ophtalmique directe (carboplatine) sont utilisées aujourd'hui dans certains cas résistants. La radiothérapie actuelle, appliquée exclusivement en deuxième intention, fait appel également à des techniques ciblées, permettant d'éviter les tissus sains et de réduire le risque de cancers radio-induits non oculaires. La radiothérapie stéréotaxique conformationnelle ou conformale et la proton-thérapie font ainsi partie du nouvel arsenal thérapeutique du rétinoblastome. Retinoblastoma represents 11% of all cancers during the first year of life. New drugs and focal treatments have been developed in order to avoid the side effects of systemic chemotherapy and external radiotherapy. New targeted and local administration strategies such as periocular chemotherapy (topotecan) or direct ophthalmic artery delivery (carboplatin), are already used today in selected resistant cases. Radiotherapy, presently indicated only as a second-line treatment, is also subject to new techniques, targeting tumors more closely to avoid involving healthy tissue and reduce the risk of radio-induced nonocular tumors. Stereotactic conformal radiotherapy and proton therapy may thus be included in the new range of treatment methods in retinoblastoma

Handling macromolecule signals in the quantification of the neurochemical profile.

In vivo localized proton magnetic resonance spectroscopy (1H MRS) became a powerful and unique technique to non-invasively investigate brain metabolism of rodents and humans. The main goal of 1H MRS is the reliable quantification of concentrations of metabolites (neurochemical profile) in a well-defined region of the brain. The availability of very high magnetic field strengths combined with the possibility of acquiring spectra at very short echo time have dramatically increased the number of constituents of the neurochemical profile. The quantification of spectra measured at short echo times is complicated by the presence of macromolecule signals of particular importance at high magnetic fields. An error in the macromolecule estimation can lead to substantial errors in the obtained neurochemical profile. The purpose of the present review is to overview methods of high field 1H MRS with a focus on the metabolite quantification, in particular in handling signals of macromolecules. Three main approaches of handling signals of macromolecules are described, namely mathematical estimation of macromolecules, measurement of macromolecules in vivo, and direct acquisition of the in vivo spectrum without the contribution of macromolecules.

Long-distance wound signalling in arabidopsis

The leaves of all plants use elaborate and inducible defence systems to protect themselves. A wide variety of such defences are known and they include defence chemicals such as alkaloids, phenolics and terpenes, physical structures ranging from fibre cells to silica deposits, and a wide variety of defence proteins many of which target digestive processes in herbivores. It has long been known that the defence responses of plants under attack by insects are not restricted to the site of attack. Instead, if a leaf is damaged, defence can be triggered in other parts of the plant body, for example in distal leaves or even in roots and flowers. This raises the question of what are the organ-to-organ signals that coordinate this process. Several hypotheses have been proposed. These include the long-distance transfer of chemical signals through the plant vasculature, hydraulic signals that may transit through the xylem, and electrical signals that would move through living tissues such as the phloem. Much evidence for each of these scenarios has been published. In this thesis we took advantage of the fact that many plant defence responses are regulated by a signal transduction pathway based on a molecule called jasmonic acid. We used this molecule, one of its derivatives (jasmonoyl-isoleucine), and some of the genes it regulates as markers. Using these we investigated the possible role of the electrical signals in the leaf- to-leaf activation of the jasmonate pathway. We found that feeding insects stimulate easily detected electrical activity in the leaves of Arabidopsis thaliana and we used non-invasive surface electrodes to record this activity. This approach showed that jasmonate pathway activity and the electrical activity provoked by mechanical wounding occurred within identical spatial boundaries. Measurements of the apparent speed of surface potentials agreed well with previous velocity estimates for the speed of leaf-to-leaf signals that activate the jasmonate pathway. Using this knowledge we were able to investigate the effects of current injection into Arabidopsis leaves. This resulted in the strong expression of many jasmonate-regulated genes. All these results showed that electrical activity and the activation of jasmonate signalling were highly correlated. In order to test for possible causal links between the two processes, we conducted a small-scale reverse genetic screen on a series of T-DNA insertion mutants in ion channel genes and in other genes encoding proteins such as proton pumps. This screen, which was based on surface potential measurements, revealed that mutations in genes related to ionotropic glutamate receptors in animals had impaired electrical activity after wounding. Combining mutation of two of these glutamate-receptor-like genes in a double mutant reduced the response of leaves to current injection. When a leaf of this double mutant was wounded it failed to transmit a long-distance signal to a distal leaf. This result distinguished the double mutant from the wild-type plant and provides the first genetic evidence that electrical signalling is necessary to coordinate defence responses between organs in plants. - Les feuilles des plantes disposent de systèmes de défense inductibles très élaborés. Un grand nombre de ces systèmes de défenses sont connus et sont basés sur des composés chimiques comme les alcaloïdes, les composés phénoliques ou les terpènes, des systèmes physiques allant de la production de cellules fibreuses aux cristaux de silice ainsi qu'un grand nombre de protéines de défense ciblant le processus digestif des herbivores. Il est connu dépuis longtemps que la réponse défensive de la plante face à l'attaque pas un insecte n'est pas seulement localisée au niveau de la zone d'attaque. A la place, si une feuille est attaquée, les systèmes de défense peuvent être activés ailleurs dans la plante, comme par exemple dans d'autres feuilles, les racines ou même les fleurs. Ces observations soulèvent la question de la nature des signaux d'organes à organes qui régulent ces systèmes. Plusieurs hypothèses ont été formulées; une ou plusieures molécules pourraient être véhiculées dans la plante grâce au système vasculaire, un signal hydraulique transmis au travers du xylème ou encore des signaux électriques transmis par les cellules comme dans le phloème par exemple. De nombreuses études ont été publiées sur ces différentes hypothèses. Dans ce travail de thèse, nous avons choisi d'utiliser à notre avantage le fait que de nombreuses réponses de défense de la plante sont régulées par une même voie de signalisation utilisant l'acide jasmonique. Nous avons utilisé comme marqueurs cette molécule, un de ses dérivés (le jasmonoyl-isoleucine) ainsi que certains des gènes que l'acide jasmonique régule. Nous avons alors testé l'implication de la transmission de signaux électriques dans l'activation de la voie du jasmonate de feuille à feuille. Nous avons découvert que les insectes qui se nourrissent de feuilles d'Arabidopsis thaliana activent un signal électrique que nous avons pu mesurer grâce à une technique non invasive d'électrodes de surface. Les enregistrements ont montré que la génération de signaux électriques et l'activation de la voie du jasmonate avaient lieu aux mêmes endroits. La mesure de la vitesse de déplacement des impulsions électriques correspond aux estimations faites concernant l'activation de la voie du jasmonate. Grâce à cela, nous avons pu tester l'effet d'injection de courant électrique dans les feuilles d'Arabidopsis. La conséquence a été une forte expression de nombreux gènes de la voie du jasmonate, suggérant une forte corrélation entre l'activité électrique et l'activation de la voie du jasmonate. Afin de tester le lien de cause entre ces deux phénomènes, nous avons entrepris un criblage génétique sur une série de mutants d'insertion à l'ADN-T dans des gènes de canaux ioniques et d'autres gènes d'intérêt comme les gènes des pompes à protons. Ce criblage, basé sur la mesure de potentiels de surface, a permis de montrer que plusieurs mutations de gènes liés aux récepteurs au glutamate ionotropique présentent une baisse drastique de leurs activités électriques après une blessure mécanique des feuilles par rapport au type sauvage. Par la combinaison de deux mutations de ces récepteurs au glutamate en un double mutant, on obtient une réponse à la stimulation électrique encore plus faible. Quand une feuille du double mutant est blessée, elle est incapable de transmettre un signal à longue distance vers une feuille éloignée. Ce résultat permet de distinguer le double mutant de la plante sauvage et amène la première preuve génétique que l'activité électrique est nécessaire pour coordonner les réponses de défense entre les organes chez les plantes.

Appropriate management of special situations in Crohn's disease (upper gastro-intestinal; extra-intestinal manifestations; drug safety during pregnancy and breastfeeding): results of a multidisciplinary international expert panel-EPACT II

Introduction: High-grade evidence is lacking for most therapeutic decisions in Crohn's disease. Appropriateness criteria were developed for upper gastro-intestinal, extra-intestinal manifestations and drug safety during conception, pregnancy and breastfeeding in patients with Crohn's disease, to assist the physician in clinical decision making. Methods: The European Panel on the Appropriateness of Crohn's Disease Therapy (EPACT II), a multidisciplinary international European expert panel, rated clinical scenarios based on evidence from the published literature and panelists' own clinical expertise. Median ratings (on a 9-point scale) were stratified into three categories: appropriate (7-9), uncertain (4-6 with or without disagreement) and inappropriate (1-3). Experts were also asked to rank appropriate medications by priority. Results: Proton pump inhibitors, steroids, azathioprine/6-mercaptopurine and infliximab are appropriate for upper gastro-duodenal Crohn's disease; for stenosis, endoscopic balloon dilation is the first-tine therapy, although surgery is also appropriate. Ursodeoxycholic acid is the only appropriate treatment for primary sclerosing cholangitis. Infliximab is appropriate for Pyoderma gangrenosum, ankylosing spondylitis and uveitis, steroids for Pyoderma gangrenosum and ankylosing spondylitis, adalimumab for Pyoderma gangrenosum and ankylosing spondylitis, cyclosporine-A/tacrolimus for Pyoderma gangrenosum. Mesalamine, sulfasalazine, prednisone, azathioprine/6-mercaptopurine, ciprofloxacin, and probiotics, may be administered safety during pregnancy or for patients wishing to conceive, with the exception that mate patients considering conception should avoid sulfasalazine. Metronidazol is considered safe in the 2nd and 3rd trimesters whereas infliximab is rated safe in the 1st trimester but uncertain in the 2nd and 3rd trimesters. Methotrexate is always contraindicated at conception, during pregnancy or during breastfeeding, due to its known teratogenicity. Mesalamine, prednisone, probiotics and infliximab are considered safe during breastfeeding. Conclusion: EPACT II recommendations are freely available online (www.epact.ch). The validity of these criteria should now be tested by prospective evaluation. (C) 2009 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.

Pharmacovigilance update [Pharmacovigilance update]

Main pharmacovigilance signals and alerts issued in 2009 are reviewed. Efalizumab was withdrawn from the market due to increased risks, including progressive multifocal leukoencephalopathy (PML) and questionable efficacy. New cases of PML are still being reported with rituximab and natalizumab. Rare cases of pure red cell aplasia have been observed with mycophenate. Gastrointestinal perforation, severe skin rashes and various ocular disorders have been reported during erlotinib use. Severe skin rashes have been related to etravirine. Acute renal failure and pancreatitis can occur with exenatide. A link between sitagliptin and pancreatitis is suspected. Raised concerns of causality between insuline glargine and malignant tumors are not supported by strong evidence. Proton pump inhibitors seem to blunt clopidogrel benefit. Aliskiren can cause angioedema.

Combined transesophageal and surface MRI provides optimal imaging in aortic atherosclerosis.

OBJECTIVE: Surface magnetic resonance imaging (MRI) for aortic plaque assessment is limited by the trade-off between penetration depth and signal-to-noise ratio (SNR). For imaging the deep seated aorta, a combined surface and transesophageal MRI (TEMRI) technique was developed 1) to determine the individual contribution of TEMRI and surface coils to the combined signal, 2) to measure the signal improvement of a combined surface and TEMRI over surface MRI, and 3) to assess for reproducibility of plaque dimension analysis. METHODS AND RESULTS: In 24 patients six black blood proton-density/T2-weighted fast-spin echo images were obtained using three surface and one TEMRI coil for SNR measurements. Reproducibility of plaque dimensions (combined surface and TEMRI) was measured in 10 patients. TEMRI contributed 68% of the signal in the aortic arch and descending aorta, whereas the overall signal gain using the combined technique was up to 225%. Plaque volume measurements had an intraclass correlation coefficient of as high as 0.97. CONCLUSION: Plaque volume measurements for the quantification of aortic plaque size are highly reproducible for combined surface and TEMRI. The TEMRI coil contributes considerably to the aortic MR signal. The combined surface and TEMRI approach improves aortic signal significantly as compared to surface coils alone. CONDENSED ABSTRACT: Conventional MRI aortic plaque visualization is limited by the penetration depth of MRI surface coils and may lead to suboptimal image quality with insufficient reproducibility. By combining a transesophageal MRI (TEMRI) with surface MRI coils we enhanced local and overall image SNR for improved image quality and reproducibility.