Exocyclic Carbons Adjacent to the N6 of Adenine are Targets for Oxidation by the Escherichia coli Adaptive Response Protein AlkB

The DNA and RNA repair protein AlkB removes alkyl groups from nucleic acids by a unique iron- and α-ketoglutarate-dependent oxidation strategy. When alkylated adenines are used as AlkB targets, earlier work suggests that the initial target of oxidation can be the alkyl carbon adjacent to N1. Such may be the case with ethano-adenine (EA), a DNA adduct formed by an important anticancer drug, BCNU, whereby an initial oxidation would occur at the carbon adjacent to N1. In a previous study, several intermediates were observed suggesting a pathway involving adduct restructuring to a form that would not hinder replication, which would match biological data showing that AlkB almost completely reverses EA toxicity in vivo. The present study uses more sensitive spectroscopic methodology to reveal the complete conversion of EA to adenine; the nature of observed additional putative intermediates indicates that AlkB conducts a second oxidation event in order to release the two-carbon unit completely. The second oxidation event occurs at the exocyclic carbon adjacent to the N[superscript 6] atom of adenine. The observation of oxidation of a carbon at N[superscript 6] in EA prompted us to evaluate N[superscript 6]-methyladenine (m6A), an important epigenetic signal for DNA replication and many other cellular processes, as an AlkB substrate in DNA. Here we show that m6A is indeed a substrate for AlkB and that it is converted to adenine via its 6-hydroxymethyl derivative. The observation that AlkB can demethylate m6A in vitro suggests a role for AlkB in regulation of important cellular functions in vivo.National Institutes of Health (U.S.) (Grant number CA080024)National Institutes of Health (U.S.) (Grant number CA26731)National Institutes of Health (U.S.) (Grant number ES02109

DNA methylation on N6-adenine in mammalian embryonic stem cells

It has been widely accepted that 5-methylcytosine is the only form of DNA methylation in mammalian genomes. Here we identify N6-methyladenine as another form of DNA modification in mouse embryonic stem cells. Alkbh1 encodes a demethylase for N6-methyladenine. An increase of N6-methyladenine levels in Alkbh1-deficient cells leads to transcriptional silencing. N6-methyladenine deposition is inversely correlated with the evolutionary age of LINE-1 transposons; its deposition is strongly enriched at young (6 million years old) L1 elements. The deposition of N6-methyladenine correlates with epigenetic silencing of such LINE-1 transposons, together with their neighbouring enhancers and genes, thereby resisting the gene activation signals during embryonic stem cell differentiation. As young full-length LINE-1 transposons are strongly enriched on the X chromosome, genes located on the X chromosome are also silenced. Thus, N6-methyladenine developed a new role in epigenetic silencing in mammalian evolution distinct from its role in gene activation in other organisms. Our results demonstrate that N6-methyladenine constitutes a crucial component of the epigenetic regulation repertoire in mammalian genomes

High-Intensity Interval Training Interventions in Children and Adolescents: A Systematic Review

BackgroundWhilst there is increasing interest in the efficacy of high-intensity interval training in children and adolescents as a time-effective method of eliciting health benefits, there remains little consensus within the literature regarding the most effective means for delivering a high-intensity interval training intervention. Given the global health issues surrounding childhood obesity and associated health implications, the identification of effective intervention strategies is imperative.ObjectivesThe aim of this review was to examine high-intensity interval training as a means of influencing key health parameters and to elucidate the most effective high-intensity interval training protocol.MethodsStudies were included if they: (1) studied healthy children and/or adolescents (aged 5–18 years); (2) prescribed an intervention that was deemed high intensity; and (3) reported health-related outcome measures.ResultsA total of 2092 studies were initially retrieved from four databases. Studies that were deemed to meet the criteria were downloaded in their entirety and independently assessed for relevance by two authors using the pre-determined criteria. From this, 13 studies were deemed suitable. This review found that high-intensity interval training in children and adolescents is a time-effective method of improving cardiovascular disease biomarkers, but evidence regarding other health-related measures is more equivocal. Running-based sessions, at an intensity of >90% heart rate maximum/100–130% maximal aerobic velocity, two to three times a week and with a minimum intervention duration of 7 weeks, elicit the greatest improvements in participant health.ConclusionWhile high-intensity interval training improves cardiovascular disease biomarkers, and the evidence supports the effectiveness of running-based sessions, as outlined above, further recommendations as to optimal exercise duration and rest intervals remain ambiguous owing to the paucity of literature and the methodological limitations of studies presently available

Quantitative In Vivo Magnetic Resonance Spectroscopy Using Synthetic Signal Injection

Accurate conversion of magnetic resonance spectra to quantitative units of concentration generally requires compensation for differences in coil loading conditions, the gains of the various receiver amplifiers, and rescaling that occurs during post-processing manipulations. This can be efficiently achieved by injecting a precalibrated, artificial reference signal, or pseudo-signal into the data. We have previously demonstrated, using in vitro measurements, that robust pseudo-signal injection can be accomplished using a second coil, called the injector coil, properly designed and oriented so that it couples inductively with the receive coil used to acquire the data. In this work, we acquired nonlocalized phosphorous magnetic resonance spectroscopy measurements from resting human tibialis anterior muscles and used pseudo-signal injection to calculate the Pi, PCr, and ATP concentrations. We compared these results to parallel estimates of concentrations obtained using the more established phantom replacement method. Our results demonstrate that pseudo-signal injection using inductive coupling provides a robust calibration factor that is immune to coil loading conditions and suitable for use in human measurements. Having benefits in terms of ease of use and quantitative accuracy, this method is feasible for clinical use. The protocol we describe could be readily translated for use in patients with mitochondrial disease, where sensitive assessment of metabolite content could improve diagnosis and treatment

Development of a Unifying Target and Consensus Indicators for Global Surgical Systems Strengthening: Proposed by the Global Alliance for Surgery, Obstetric, Trauma, and Anaesthesia Care (The G4 Alliance)

After decades on the margins of primary health care, surgical and anaesthesia care is gaining increasing priority within the global development arena. The 2015 publications of the Disease Control Priorities third edition on Essential Surgery and the Lancet Commission on Global Surgery created a compelling evidenced-based argument for the fundamental role of surgery and anaesthesia within cost-effective health systems strengthening global strategy. The launch of the Global Alliance for Surgical, Obstetric, Trauma, and Anaesthesia Care in 2015 has further coordinated efforts to build priority for surgical care and anaesthesia. These combined efforts culminated in the approval of a World Health Assembly resolution recognizing the role of surgical care and anaesthesia as part of universal health coverage. Momentum gained from these milestones highlights the need to identify consensus goals, targets and indicators to guide policy implementation and track progress at the national level. Through an open consultative process that incorporated input from stakeholders from around the globe, a global target calling for safe surgical and anaesthesia care for 80% of the world by 2030 was proposed. In order to achieve this target, we also propose 15 consensus indicators that build on existing surgical systems metrics and expand the ability to prioritize surgical systems strengthening around the world

Systematic ratio normalization of gas chromatography signals for biological sample discrimination and biomarker discovery

The present paper introduces a new gas chromatography data processing procedure dubbed systematic ratio normalization (SRN) enabling to improve both sample set discrimination and biomarker identification. SRN consists in (1) calculating, for each sample, all the log-ratios between abundances of chromatography-analyzed compounds, then (2) selecting the log-ratio(s) that best maximize the discrimination between sample-sets. The relevance of SRN was evaluated on two data sets acquired through gas chromatography-mass spectrometry as part of separate studies designed (i) to discriminate source-origins between vegetable oils analyzed via an analytical system exposed to instrument drift (data set 1) and (ii) to discriminate animal feed between meat samples aged for different durations (data set 2). Applying SRN to raw data made it possible to obtain robust discrimination models for the two data sets by enhancing the contribution to the data variance of the factor-of-interest while stabilizing the contribution of the disturbance factor. The most discriminant log-ratios were shown to employ the most relevant biomarkers presenting relative independence of the factor-of-interest as well as co-behavior of the disturbance effects potentially biasing the discrimination, such as instrument drift or sample biochemical changes. SRN can be run a posteriori on any data set, and might be generalizable to most of separating methods. (C) 2012 Elsevier B.V. All rights reserved

Validation de la détermination des contraintes par diffraction des rayons X avec un détecteur 2D - Développement d'un logiciel libre 'X-light'

National audienc

Validation de la détermination des contraintes par diffraction des rayons X avec un détecteur 2D - Développement d'un logiciel libre 'X-light'

National audienc

Évaluation des contraintes résiduelles dans l’alliages Ti-6Al-4V mis en forme par SLM

International audienceLa fabrication additive est définie comme étant le procédé de mise en forme d’une pièce par ajout de matière, à l’opposé de la mise en forme traditionnelle par enlèvement de matière (usinage). La fusion laser sur lit de poudre « Selective Laser Melting - SLM » est l’une des technologies les plus développées de la fabrication additive. Au cours de ce procédé, un laser vient fondre une couche fine de poudre. Une seconde couche est ensuite déposée puis fondue. Plusieurs géométries ont été proposées dans la littérature pour permettre de montrer les effets des paramètres procédés sur les champs de CR [1, 2, 3]. Pour quantifier les CR par une méthode autre que la DRX, nous avons choisi une géométrie d’échantillon particulière. Il s’agit d’un parallélépipède troué par un demi-cercle. Les résultats d’analyse des CR par DRX montrent en surface des contraintes en traction pouvant atteindre 350 MPa. Une étude de l’influence des paramètres du procédé sur les niveaux de contraintes a été également menée. Un modèle numérique avec un couplage thermomécanique est mis en place pour prédire les CR engendrée par les gradients de température dans la pièce fabriquée avec différentes stratégies. Les modèles montrent que ces CR sont de l’ordre de 750 MPa pour le TA6V. 1. D. Buchbinder et al., Journal of Laser Applications, 26, (2014). 2. M. F. Zaeh and G. Branner, Prod. Eng. Res. Devel., (2010), 35-45. 3. L.N. Carter et al., Journal of Alloys and Compounds, 615, (2014), 338-347

Évaluation des contraintes résiduelles dans l’alliages Ti-6Al-4V mis en forme par SLM

International audienceLa fabrication additive est définie comme étant le procédé de mise en forme d’une pièce par ajout de matière, à l’opposé de la mise en forme traditionnelle par enlèvement de matière (usinage). La fusion laser sur lit de poudre « Selective Laser Melting - SLM » est l’une des technologies les plus développées de la fabrication additive. Au cours de ce procédé, un laser vient fondre une couche fine de poudre. Une seconde couche est ensuite déposée puis fondue. Plusieurs géométries ont été proposées dans la littérature pour permettre de montrer les effets des paramètres procédés sur les champs de CR [1, 2, 3]. Pour quantifier les CR par une méthode autre que la DRX, nous avons choisi une géométrie d’échantillon particulière. Il s’agit d’un parallélépipède troué par un demi-cercle. Les résultats d’analyse des CR par DRX montrent en surface des contraintes en traction pouvant atteindre 350 MPa. Une étude de l’influence des paramètres du procédé sur les niveaux de contraintes a été également menée. Un modèle numérique avec un couplage thermomécanique est mis en place pour prédire les CR engendrée par les gradients de température dans la pièce fabriquée avec différentes stratégies. Les modèles montrent que ces CR sont de l’ordre de 750 MPa pour le TA6V. 1. D. Buchbinder et al., Journal of Laser Applications, 26, (2014). 2. M. F. Zaeh and G. Branner, Prod. Eng. Res. Devel., (2010), 35-45. 3. L.N. Carter et al., Journal of Alloys and Compounds, 615, (2014), 338-347