Evaluation de la durabilité du béton armé vis à vis des ions chlorure à l'aide de capteurs noyés dans le béton versus des auscultations en parement

GC'2019, le Génie Civil au coeur des mutations technologiques et numériques , CACHAN, FRANCE, 20-/03/2019 - 21/03/2019L'évaluation du processus de corrosion de structures en béton armé en milieu chloruré a été étudiée en utilisant deux approches complémentaires : l'auscultation non destructive (ND) du béton d'enrobage et la corrosion des armatures. Différentes méthodes d'évaluation non destructives basées, soit sur de l'instrumentation avec des capteurs noyés dans le béton armé, soit sur des auscultations réalisées en parement, ont été utilisées afin de caractériser la phase d'incubation puis la phase de propagation de la corrosion. Dans cette première phase d'étude, les différents objectifs étaient les suivants : 1) Etudier des bétons différents formulés avec du ciment Portland ou des laitiers, en termes de réaction de transfert dans le béton et de réactions électrochimiques armature/béton/environnement, 2) Analyser les résultats des capteurs noyés dans le béton armé (formulé avec du ciment Portland ou des laitiers) qui permettent de suivre en continu l'évolution des phénomènes, 3) Comparer les résultats entre les capteurs noyés et les mesures réalisées sur parement, 4) Démontrer l'intérêt du Corrosion Health Monitoring sur ouvrages neufs et/ou réparés en termes de surveillance (système d'alerte plutôt qu'alarme) dans le temps. Les différentes méthodes basées sur des mesures de résistivité (capteurs noyés et auscultation en surface) permettent d'accéder à des profils traduisant la pénétration d'eau de mer par imbibition. Des méthodologies d'inversion et de calibration ont été consolidées. Une expérience sur les capteurs de corrosion a été capitalisée. Enfin, de nouvelles méthodes ont été explorées (SUSI, radar de fréquence,...) et certaines sont prometteuses. Les interprétations des résultats peuvent s'avérer délicates et il convient de bien énoncer les hypothèses et les limites notamment dans une prise de décision (maintenance et/ou réparation par ex). Enfin, il est nécessaire de poursuivre cette étude sur du plus long terme afin d'affiner les résultats et les applications fortes pour la gestion du parc d'ouvrages vieillissants

Multifocal Ectopic Purkinje-Related Premature Contractions: A New SCN5A-Related Cardiac Channelopathy.: MEPPC: a new SCN5A-related cardiac channelopathy

International audienceOBJECTIVES: The aim of this study was to describe a new familial cardiac phenotype and to elucidate the electrophysiological mechanism responsible for the disease. BACKGROUND: Mutations in several genes encoding ion channels, especially SCN5A, have emerged as the basis for a variety of inherited cardiac arrhythmias. METHODS: Three unrelated families comprising 21 individuals affected by multifocal ectopic Purkinje-related premature contractions (MEPPC) characterized by narrow junctional and rare sinus beats competing with numerous premature ventricular contractions with right and/or left bundle branch block patterns were identified. RESULTS: Dilated cardiomyopathy was identified in 6 patients, atrial arrhythmias were detected in 9 patients, and sudden death was reported in 5 individuals. Invasive electrophysiological studies demonstrated that premature ventricular complexes originated from the Purkinje tissue. Hydroquinidine treatment dramatically decreased the number of premature ventricular complexes. It normalized the contractile function in 2 patients. All the affected subjects carried the c.665G>A transition in the SCN5A gene. Patch-clamp studies of resulting p.Arg222Gln (R222Q) Nav1.5 revealed a net gain of function of the sodium channel, leading, in silico, to incomplete repolarization in Purkinje cells responsible for premature ventricular action potentials. In vitro and in silico studies recapitulated the normalization of the ventricular action potentials in the presence of quinidine. CONCLUSIONS: A new SCN5A-related cardiac syndrome, MEPPC, was identified. The SCN5A mutation leads to a gain of function of the sodium channel responsible for hyperexcitability of the fascicular-Purkinje system. The MEPPC syndrome is responsive to hydroquinidine

MAGP-1 and fibronectin control EGFL7 functions by driving its deposition into distinct endothelial extracellular matrix locations

The extracellular matrix (ECM) is essential to provide mechanical support to tissues but is also a bioactive edifice which controls cell behavior. Cell signaling generated by ECM components through integrin-mediated contacts, modulates cell biological activity. In addition, by sequestrating or releasing growth factors, the ECM is an active player of physiological and pathological processes such as vascular development. EGFL7 is mainly expressed during blood vessel development and is deposited in the ECM after secretion by endothelial cells. While EGFL7 is known to control various endothelial cell molecular mechanisms [i.e., the repression of endothelial-derived lysyl oxidase (LOX) enzyme, the regulation of the Notch pathway, and the expression of leukocyte adhesion molecules and of RHOA by endothelial cells], it is not established whether EGFL7 functions when bound to the ECM. Here, we show that microfibrillar-associated glycoprotein-1 (MAGP-1) and fibronectin drive the deposition of EGFL7 into both fibers and individual aggregates in endothelial ECM. Although EGFL7 does not need to be docked into the ECM to control endothelial adhesion molecule expression, the ECM accumulation of EGFL7 is required for its regulation of LOX activity and of HEY2 expression along the Notch pathway. The interaction of EGFL7 with MAGP-1 is necessary for LOX activity repression by EGFL7 while it does not participate in the control of the Notch pathway by this protein. Altogether, this study highlights the roles played by EGFL7 in controlling various endothelial molecular mechanisms upon its localization and shows how the ECM can modulate its functions

Heterozygous mutation in the pore of potassium channel gene KvLQT1 causes an apparently normal phenotype in long QT syndrome

International audienceMutations in KvLQT1, a gene encoding a potassium channel, cause both the recessive Jervell and Lange-Nielsen (JLN) syndrome and the dominant Romano-Ward (RW) syndrome. These diseases are characterised by a prolonged QT interval on the ECG, syncopes and sudden death due to cardiac arrhythmias. The JLN syndrome is also associated with a congenital bilateral deafness. We report here a novel missense mutation, W305S, in the pore region of KvLQT1 identified by PCR-SSCP analysis in two consanguineous JLN families. In contrast to several missense mutations found in the same region of KvLQT1 in RW patients which are associated with severe cardiac phenotypes, the W305S mutation is responsible for an apparently normal phenotype in heterozygous JLN carriers

Long QT syndrome in neonates Conduction disorders associated with HERGmutations and sinus bradycardia with KCNQ1mutations

AbstractObjectivesWe hypothesized that neonatal long QT syndrome (LQTS) with 2:1 atrioventricular block (AVB) could be related to HERGmutations.BackgroundEarly onset of LQTS is rare but carries a high risk of life-threatening events such as ventricular arrhythmias and conduction disorders. There are no data on possible gene specificity.MethodsWe analyzed the characteristics and outcomes of 23 neonate probands from our LQTS population. Samples of DNA were available in 18 cases.ResultsLong QT syndrome was diagnosed because of corrected QT interval (QTc) prolongation (mean QTc of 558 ± 62 ms) and neonatal bradycardia attributable to sinus bradycardia (n = 8) or 2:1 AVB (n = 15). Symptoms included syncope (n = 2), torsades de pointes (n = 7), and hemodynamic failure (n = 6). Three infants with 2:1 AVB died during the first month of life. During the neonatal period, all living patients received beta-blockers (BB) and 13 had a combination of BB and permanent cardiac pacing. Under treatment, patients remained asymptomatic, with a mean follow-up of seven years. Mutations were identified in HERG(n = 8) and KCNQ1(n = 8), and one child had three mutations (HERG, KCNQ1, and SCN5A). Conduction disorders were associated with LQT2, whereas sinus bradycardia was associated with LQT1.ConclusionsTwo-to-one AVB seems preferentially associated with HERGmutations, either isolated or combined. Long QT syndrome with relative bradycardia attributable to 2:1 AVB has a poor prognosis during the first month of life. In contrast, sinus bradycardia seems to be associated with KCNQ1mutations, with a good short-term prognosis under BB therapy

Incomplete Timothy syndrome secondary to a mosaic mutation of the CACNA1C gene diagnosed using next-generation sequencing

International audienceAutosomal dominant genetic diseases can occur de novo and in the form of somatic mosaicism, which can give rise to a less severe phenotype, and make diagnosis more difficult given the sensitivity limits of the methods used. We report the case of female child with a history of surgery for syndactyly of the hands and feet, who was admitted at 6 years of age to a pediatric intensive care unit following cardiac arrest. The electrocardiogram (ECG) showed a long QT interval that on occasions reached 500ms. Despite the absence of facial dysmorphism and the presence of normal psychomotor development, a diagnosis of Timothy syndrome was made given the association of syndactyly and the ECG features. Sanger sequencing of the CACNA1C gene, followed by sequencing of the genes KCNQ1, KCNH2, KCNE1, KCNE2, were negative. The subsequent analysis of a panel of genes responsible for hereditary cardiac rhythm disorders using Haloplex technology revealed a recurrent mosaic p.Gly406Arg missense mutation of the CACNA1C gene in 18% of the cells. This mosaicism can explain the negative Sanger analysis and the less complete phenotype in this patient. Given the other cases in the literature, mosaic mutations in Timothy syndrome appear more common than previously thought. This case demonstrates the importance of using next-generation sequencing to identify mosaic mutations when the clinical picture supports a specific mutation that is not identified using conventional testing