Quantifying the PR interval pattern during dynamic exercise and recovery.

International audienceWe present a novel analysis tool for time delay estimation in electrocardiographic signal processing. This tool enhances PR interval estimation (index of the atrioventricular conduction time) by limiting the distortion effect of the T wave overlapping the P wave at high heart rates. Our approach consists of modeling the T wave, cancelling its influence, and finally estimating the PR intervals during exercise and recovery with the proposed generalized Woody method. Different models of the T wave are presented and compared in a statistical summary that quantitatively justifies the improvements introduced by this study. Among the different models tested, we found that a piecewise linear function significantly reduces the T wave-induced bias in the estimation process. Combining this modeling with the proposed time delay estimation method leads to accurate PR interval estimation. Using this method on real ECGs recorded during exercise and its recovery, we found: 1) that the slopes of PR interval series in the early recovery phase are dependent on the subjects' training status (average of the slopes for sedentary men = 0.11 ms/s, and for athlete men = 0.28 ms/s), and 2) an hysteresis phenomenon exists in the relation PR/RR intervals when data from exercise and recovery are compared

Susceptibility to Paroxysmal Atrial Fibrillation: A Study using Sinus Rhythm P Wave Parameters

International audienceEarly recognition of patients at high risk for atrial fibrillation may help to minimize potential health risks. The detection of susceptibility to develop atrial fibrillation is thus a real clinical challenge. Whereas many studies have used the signal-averaged P wave, the aim of this work is to determine whether electrocardiographic parameters resulting from the analysis of the P wave in ECG recorded during sinus rhythm could be markers for paroxysmal atrial fibrillation susceptibility. Our idea was to compare the ECG in sinus rhythm from two populations: healthy people and patients subject to paroxysmal atrial fibrillation. In addition to standard P wave parameters (P width, P-R interval,...), the Euclidean distance between beat-to-beat P waves, which has been rarely addressed in this context, was studied on lead V1. Significant differences between the healthy and the paroxysmal atrial fibrillation groups were obtained for various parameters. Moreover, a classification of the two groups based on the joint analysis of P width and P-R interval was suggested. This proposed classification could lead to an effective identification of patients at risk to develop atrial fibrillation

Ressources génétiques : apport de l'hybridation somatique pour l'exploitation des ressources génétiques des agrumes

L'hybridation somatique permet d'accroître la diversité des pools géniques des espèces cultivées, non seulement en contournant les incompatibilités ou contraintes sexuelles, mais également en combinant les génomes nucléaires, chloroplastiques et mitochondriaux suivant de nouvelles règles. Elle trouve des applications importantes chez les agrumes compte tenu du caractère apomictique ou de la stérilité de nombreux cultivars et de la structure du complexe d'espèces. Les génomes de cultivars inexploitables par voie sexuée ont ainsi été intégrés au sein d'hybrides tétraploïdes par fusion de protoplastes au polyéthylène glycol ou par électrofusion. Cette manipulation de la ploïdie via l'hybridation somatique, dont l'objectif final est la sélection de cultivars triploïdes aspermes, a permis d'enrichir considérablement le compartiment têtraploïde du complexe d'espèce. Elle s'applique également à la synthèse directe d'hybrides triploïdes par fusion de roto astes ha loïdes et diploïdes. L'addition de l'ensemble des gènes des deux parents quels que soient leurs niveaux d'hétérozygotie trouve une application majeure pour la création de porte-greffes cumulant des caractères de résistance. L'exploitation de la diversité de genres sexuellement incompatibles est en revanche moins utile compte tenu des défauts présentés par la majorité des hybrides. Dans ce cas, la mise en oeuvre de programmes d'hybridations asymétriques paraît souhaitable pour n'introgresser que quelques fragments du génome des espèces sauvages. Des alloplastes générés par hybridation symétrique ouvrent la voie à l'étude des interactions nuclé-cytoplasmiques. L'hybridation somatique entraîne une évolution majeure du pool génique des agrumes vers un complexe polyploïde. (Résumé d'auteur

A new method for the PP-PR hysteresis phenomenon enhancement under exercise conditions

A non-linear relation between PR and PP intervals has been established in a previous work [1] under maximal and graded exercise test as well as under pyramidal ex-ercise where the effort is not released abruptly. This study presents a new method whose aim is to exhibit more clearly the hysteresis behavior of this non-linear relation under graded exercise. After the description of the initial ap-proach, we propose a second one which can provide a bet-ter estimation of the PR intervals. Moreover pooling the results of these two methods leads to an improvement of the estimation accuracy of PR intervals and then the hys-teresis. It is well known that a hysteresis behavior exists at AV node’s level, between the refractory period and the repo-larization period. Besides, the autonomic neural system also acts upon the cardiac activity during an intense ef-fort. Therefore, hysteresis which links the “PR interval vs PP interval ” seems not be explained only at the cellular level; the heart must be viewed in his global context con-sidering the nervous system. 1

Validation of the PR-RR Hysteresis Phenomenon

Abstract Previous studies on ECG recorded under exercise conditions on sedentary and athlete subjects lead to following results: 1) the subjects can be characterized according to their training level studying the PR slope in the early recovery phase, and 2) it exists a non-linear relationship between PR and RR intervals which exhibits a clockwise hysteresis shape when data from exercise and its recovery are compared. The main drawback of these studies is that they were performed on a small size data set. As the understanding of the PR-RR hysteresis phenomenon may lead to improvement of pacemaker's design, the aim of this study is to check the PR-RR hysteresis on a larger data set

Impaired cell growth under ammonium stress explained by modeling the energy cost of vacuole expansion in tomato leaves

Ammonium (NH4+)-based fertilization efficiently mitigates the adverse effects of nitrogen fertilization on the environment. However, high concentrations of soil NH4+ provoke growth inhibition, partly caused by the reduction of cell enlargement and associated with modifications of cell composition, such as an increase of sugars and a decrease in organic acids. Cell expansion depends largely on the osmotic-driven enlargement of the vacuole. However, the involvement of subcellular compartmentation in the adaptation of plants to ammonium nutrition has received little attention, until now. To investigate this, tomato (Solanum lycopersicum) plants were cultivated under nitrate and ammonium nutrition and the fourth leaf was harvested at seven developmental stages. The vacuolar expansion was monitored and metabolites and inorganic ion contents, together with intracellular pH, were determined. A data-constrained model was constructed to estimate subcellular concentrations of major metabolites and ions. It was first validated at the three latter developmental stages by comparison with subcellular concentrations obtained experimentally using non-aqueous fractionation. Then, the model was used to estimate the subcellular concentrations at the seven developmental stages and the net vacuolar uptake of solutes along the developmental series. Our results showed ammonium nutrition provokes an acidification of the vacuole and a reduction in the flux of solutes into the vacuoles. Overall, analysis of the subcellular compartmentation reveals a mechanism behind leaf growth inhibition under ammonium stress linked to the higher energy cost of vacuole expansion, as a result of alterations in pH, the inhibition of glycolysis routes and the depletion of organic acids.TP benefited from a cotutelle PhD (University of Bordeaux and University of the Basque Country) and thanks the University of the Basque Country (UPV/EHU, Spain) for his PhD grant during the execution of this work. This research was financially supported by the Basque Government (IT-932-16) and the Spanish Government (BIO2017-84035-R co-funded by Fondo Europeo para el Desarrollo Regional [FEDER]). Analytics were supported by MetaboHUB (ANR-11-INBS-0010) and PHENOME (ANR-11-INBS-0012) projects. Technical support was provided by Cedric Cassan, Ana Renovales and Mandy Bordas. The authors also thank SGIker (UPV/EHU, FEDER, EU) for the technical and human support provided

1H-NMR metabolomics: Profiling method for a rapid and efficient screening of transgenic plants

Metabolomics-based approaches are methods of choice for studying changes in fruit composition induced by  environmental or genetic modulation of biochemical pathways in the fruit. Owing to enzyme redundancy and  high plasticity of the metabolic network, transgenic alteration of the activity of the enzymes from the central metabolism very often results in only slight modifications of the fruit composition. In order to avoid costly and  time-consuming plant analysis, we used a fast and sensitive 1H-NMR-based metabolomic profiling technique  allowing discovery of slight metabolite variations in a large number of samples. Here, we describe the  screening of transgenic tomato plants in which two genes from the central metabolism, phosphoenolpyruvate  carboxylase (EC.3.4.1.1) and malate synthase (EC 2.3.3.9) were silenced by antisens and RNAi strategy.  1H-NMR metabolomic profiles of methanol-d4 D2O buffer extracts of tomato fruit flesh were acquired and  subjected to unsupervised multivariate statistical analysis. 1H-NMR spectra were binned into variable-size  spectral domains, making it possible to get an overall analysis of a large number of resonances, even in the  case of uncontrolled variation of the chemical shift. Principal component analysis was used to separate groups  of samples and to relate known and unknown metabolites to transgenic events. The screening of 100 samples,  from extraction to data mining, took 36 h. Thus, this procedure allows the rapid selection of metabolic  phenotypes of interest among about 30 transgenic lines.Key words: Metabolome, GMO, tomato, fruit, 1H-NMR profiling, screening

High-flow nasal cannula oxygen therapy alone or with non-invasive ventilation during the weaning period after extubation in ICU: the prospective randomised controlled HIGH-WEAN protocol

INTRODUCTION: Recent practice guidelines suggest applying non-invasive ventilation (NIV) to prevent postextubation respiratory failure in patients at high risk of extubation failure in intensive care unit (ICU). However, such prophylactic NIV has been only a conditional recommendation given the low certainty of evidence. Likewise, high-flow nasal cannula (HFNC) oxygen therapy has been shown to reduce reintubation rates as compared with standard oxygen and to be as efficient as NIV in patients at high risk. Whereas HFNC may be considered as an optimal therapy during the postextubation period, HFNC associated with NIV could be an additional means of preventing postextubation respiratory failure. We are hypothesising that treatment associating NIV with HFNC between NIV sessions may be more effective than HFNC alone and may reduce the reintubation rate in patients at high risk. METHODS AND ANALYSIS: This study is an investigator-initiated, multicentre randomised controlled trial comparing HFNC alone or with NIV sessions during the postextubation period in patients at high risk of extubation failure in the ICU. Six hundred patients will be randomised with a 1:1 ratio in two groups according to the strategy of oxygenation after extubation. The primary outcome is the reintubation rate within the 7 days following planned extubation. Secondary outcomes include the number of patients who meet the criteria for moderate/severe respiratory failure, ICU length of stay and mortality up to day 90. ETHICS AND DISSEMINATION: The study has been approved by the ethics committee and patients will be included after informed consent. The results will be submitted for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT03121482