Correlations between urinary excretion of catecholamines and electrocardiographic parameters of vagal hyperreactivity in infants with fainting spells. Implication of sympathetic hypotonia?

SummaryBackgroundVagal hyperreactivity (VHR) is a frequent etiology of infant fainting spells; but it is sometimes difficult to diagnose. A biochemical test would therefore be useful, especially as the oculocardiac reflex (OCR) test innocuity is not absolute.AimsTo evaluate urinary excretions of norepinephrine, epinephrine and dopamine as markers for vagal hyperreactivity.MethodsDuring check-up of 55 infants from 0.5 to 11months of age, for discomfort episodes, including OCR and Holter recording, 24h urinary assays of total norepinephrine, epinephrine and dopamine were carried out to evaluate sympathetic activity.ResultsEpinephrine and norepinephrine urinary excretions were negatively correlated with VHR intensity, as measured by the OCR ECG parameters: RRmax, % cardiac deceleration and minimal frequency; dopamine excretion was not. When RRmaxOCR was greater or equal to 800ms, epinephrine urinary excretion tended to be less or equal to 9nmol/mmol creatinine and norepinephrine excretion less or equal to 190nmol/mmol creatinine.ConclusionA delay in maturation of the sympathetic system and/or adrenomedullary glands with low secretion of norepinephrine and epinephrine inducing a desequilibrium of the sympathetic/parasympathetic balance may contribute to the fainting spells observed with VHR. Epinephrine and norepinephrine urinary excretions may provide informative complementary noninvasive markers for VHR

Application of ToF-SIMS for sulfur isotopic fractionation in sulfide phases of iron corrosion layers: determination of bacterial impact on the formation of these phases

International audienceTo a better understanding of the iron corrosion mechanisms, it is crucial to elucidate the role of bacteria. Thus, in order to have a diagnosis of the action of bacteria in the iron corrosion, the objective of this study is to determine by ToF-SIMS the isotopic sulfur fractionation δ 34 S in iron sulfides of (sub)micrometric size located in the corrosion product layers of the ferrous objects corroded in anoxic soils and marine environment. These iron sulfides may have two origins: an abiotic origin resulting in the dissolution/reprecipitation of sulfides from the surrounding medium (for example from pyrite in a soil) or a biotic origin by the action of the sulfate-reducing bacteria that reduce sulfate ions into sulfides leading to the formation of iron sulfides with ferrous ions issued from the aqueous dissolution of metal iron. A difference in the isotopic sulfur fractionation δ 34 S in the sulfur phases according to the abiotic or biotic origin of these phases is reported in the literature. Thus in this study, the isotopic sulfur fractionation δ 34 S in the iron sulfides formed in the corrosion product layers of iron was determined to identify the formation origin of these phases and the role of bacteria in the iron corrosion. After characterization of the distribution of the different iron sulfides within the layers (optical microscopy, SEM-EDS, μRaman spectroscopy), the local isotopic fractionation of sulfur is measured by the imaging and spectroscopy ToF-SIMS technique. Some important results have been obtained. First of all, the reproducibility and the accuracy of the method were established by the choice and the validation of a hydrothermal pyrite sample calibrated relatively to the international sulfur isotopic standard Canon Diablo Troilite. Secondly, it was observed that there was no or little variation in the isotopic sulfur fractionation δ 34 S with the degree of oxidation of sulfur. Finally, a noticeable difference in the isotopic sulfur fractionation δ 34 S between iron sulfides formed in laboratory under abiotic or biotic conditions was evidenced: δ 34 S is close to 0 in abiotic conditions whereas in biotic conditions it is shifted from 0 with values up to up to some tens per mil. These first results being promising, the study is actually in progress to determine the formation origin (abiotic/biotic) of the Fe-S present in the corrosion product layers of natural systems of iron corrosion, from soils, subaquatic and marine environments

Inhibition de la glycation avancée par les flavonoïdes. Implication nutritionnelle dans la prévention des complications du diabète ?

La glycation avancée des collagènes contribue au développement des complications micro- et macrovasculaires du diabète. Les flavonoïdes sont des antioxydants naturels puissants ; il était donc intéressant de tester leurs effets sur la formation d'un produit de glycation avancée, la pentosidine, dans du collagène incubé avec du glucose. Les flavonoïdes monomériques (25 et 250 $\mu$M) réduisent fortement le rapport pentosidine/hydroxyproline en fonction de leur concentration et de leur structure. Les oligomères procyanidiques de pépin de raisin sont plus actifs que ceux d'écorce de pin. Les oligomères sont clivés en monomères dans le milieu gastrique, et les flavonoïdes monomériques sont absorbés et retrouvés à la concentration micromolaire (avec une longue durée de vie) dans les liquides extra-cellulaires, en contact avec les collagènes. En conclusion les flavonoïdes sont des inhibiteurs puissants de la formation de pentosidine dans les collagènes, actifs aux concentrations micromolaires ; de telles concentrations pourraient être obtenues dans le plasma chez les patients diabétiques après ingestion de flavonoïdes

Molecular structure of bacterial biofilms involved in iron biocorrosion

International audienceTo a better knowledge of iron biocorrosion mechanisms occurring in different applications (nuclear context, petroleum industry, cultural heritage,…), it is crucial to define which bacteria are active and their role. Despite a wide literature on the influence of bacteria on iron corrosion rates, most often considering a single metabolic group (Iron-Reducing Bacteria IRB, Sulfate-Reducing Bacteria SRB), the role of each species in a population involving various metabolisms possibly affecting corrosion remains unknown. At the same time, it is also essential to identify the corrosion products and to be able to link them to a possible bacterial activity. Our study is then devoted to the local diagnostic of the action of bacterial strains in iron corrosion. An innovative methodology for diagnosing the active bacterial strains in iron corrosion at the micrometric scale was developed by using vibrational techniques such as Attenuated Total Reflection Infra-Red ATR-IR and μRaman spectroscopies. The first step was the setup of a preparation protocol and its optimization for the characterization of bacteria by ATR-IR to obtain the vibrational fingerprint of bacterial strains performing metabolisms already identified in the nuclear context (IRB, SRB and sulfate-oxidizing bacteria SOB). The spectral fingerprint was also determined for iron coupons corroded in the presence of each strain. The question of the ability to discriminate the strains, whether planktonic or in biofilm, by their vibrational fingerprint was resolved. Indeed, the discrimination of the three bacterial strains was possible in the spectral region around 1000 cm-1. Furthermore, the strains evidenced spectra differences according to their growth mode: for strains in planktonic form, the most intense bands of the IR spectrum were those of amide I and II while for the ones in biofilm form, these were the bands of exopolysaccharides (compounds excreted by bacteria when they form biofilms) in the region around 1000 cm-1. These results allow discrimination by the ATR-IR spectrum of different bacterial strains in planktonic or in biofilm form. Since both the three strains but also their form (planktonic or biofilm) were distinguishable by their IR spectrum, experiments were conducted on iron coupons corroded with the bacterial consortium. The objective was to determine the active strains and to couple this information with the nature of the corrosion products. This diagnostic tool for bacterial signature determination can be transposed to a variety of corrosion problems providing significant benefits

Préserver les épaves métalliques coulées lors des conflits mondiaux par une protection cathodique : caractérisation globale in situ et analyse multi-échelle des couches de corrosion et de la biodiversité

International audienc

Préserver les épaves métalliques coulées lors des conflits mondiaux par une protection cathodique : caractérisation globale in situ et analyse multi-échelle des couches de corrosion et de la biodiversité

International audienc

Microbial corrosion of steel in argillite: complementarity of surface characterization (µRamanS and FESEM) and of microbiological approach

International audienc

Microbial corrosion of steel in argillite: complementarity of surface characterization (µRamanS and FESEM) and of microbiological approach

International audienc

Bioréactivité fer-argile en conditions de stockage géologique profond : approche multi-techniques

International audienceEn France, le concept de stockage de déchets radioactifs en couche argileuse profonde au sein de la formation du Callovo-Oxfordien actuellement développé par l’Agence nationale pour la gestion des déchets radioactifs (Andra) prévoit notamment l’utilisation de composants métalliques. En effet,les colis de déchets de haute activité seront placés dans des surconteneurs en acier au carbone, dont l’étanchéité doit être assurée pendant plusieurs centaines d’années, puis mis dans des alvéoles de stockage revêtues d’un chemisage de même type d’acier. Or, la présence de microorganismes aux interfaces entre la roche hôte et l’acier pourrait accélérer la corrosion des composants métalliques(chemisages et surconteneurs) et ainsi affecter leur durabilité. Les conditions d’environnement de ces composants pourront être aérées pendant plusieurs années au cours de la phase d’exploitation du stockage et, après cette phase transitoire, devenir anoxiques et saturées en eau en se rapprochant de celles de la roche hôte