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Search Results: 1 - 10 of 6321 matches for " Nicolas Rapin "
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Trace elements in glucometabolic disorders: an update
Nicolas Wiernsperger, JeanRobert Rapin
Diabetology & Metabolic Syndrome , 2010, DOI: 10.1186/1758-5996-2-70
Abstract: Many trace elements, among which metals, involved as cofactors in myriads of biochemical-especially-enzymatic reactions. As such they play cardinal roles in many physiological processes, in particular immunity and metabolism. A good example to illustrate their important contribution is magnesium: low magnesium levels have been associated with increased type 2 diabetes [1,2], whereas controversy exists about the importance of hypomagnesaemia in prediabetic states [3].Trace elements have been identified for long time as potential candidates for improving metabolic disorders like prediabetes [insulin resistance, obesity, metabolic syndrome] or diabetes. In parallel with increasing comprehension of cellular and biochemical mechanisms leading to-or aggravating- these metabolic disorders, identifying the cellular targets and sites of action of trace elements has reactivated interest in their therapeutic potential. Activation of insulin receptor signalling (chromium), antioxidant properties (selenium, zinc) or inhibition of phosphatases (vanadium) thus appeared promising in view of the key importance of these processes in glucose homeostasis and insulin sensitivity. Indeed insulin receptor/postreceptor signalling defects are considered to underlie glycemic dysregulation and insulin resistance, although the precise causal defects must still be unravelled [4,5]. Prediabetic states, and even more so frank diabetes, are characterized by inflammation [cytokines] and oxidative stress, due to disruption of the equilibrium between production of free radicals and their scavenging by multiple antioxidant systems [6-8]. Moreover, these mechanisms may be involved in concert in the pathogenesis of insulin resistance and accompanying pathologies [9].The present review updates our actual state of knowledge about those five trace elements (chromium, zinc, selenium, vanadium, lithium)which have a therapeutic potential in insulin resistance and diabetes, describing their mechanisms of actio
Possible links between intestinal permeablity and food processing: a potential therapeutic niche for glutamine
Rapin, Jean Robert;Wiernsperger, Nicolas;
Clinics , 2010, DOI: 10.1590/S1807-59322010000600012
Abstract: increased intestinal permeability is a likely cause of various pathologies, such as allergies and metabolic or even cardiovascular disturbances. intestinal permeability is found in many severe clinical situations and in common disorders such as irritable bowel syndrome. in these conditions, substances that are normally unable to cross the epithelial barrier gain access to the systemic circulation. to illustrate the potential harmfulness of leaky gut, we present an argument based on examples linked to protein or lipid glycation induced by modern food processing. increased intestinal permeability should be largely improved by dietary addition of compounds, such as glutamine or curcumin, which both have the mechanistic potential to inhibit the inflammation and oxidative stress linked to tight junction opening. this brief review aims to increase physician awareness of this common, albeit largely unrecognized, pathology, which may be easily prevented or improved by means of simple nutritional changes.
Computational Immunology Meets Bioinformatics: The Use of Prediction Tools for Molecular Binding in the Simulation of the Immune System
Nicolas Rapin,Ole Lund,Massimo Bernaschi,Filippo Castiglione
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009862
Abstract: We present a new approach to the study of the immune system that combines techniques of systems biology with information provided by data-driven prediction methods. To this end, we have extended an agent-based simulator of the immune response, C-ImmSim, such that it represents pathogens, as well as lymphocytes receptors, by means of their amino acid sequences and makes use of bioinformatics methods for T and B cell epitope prediction. This is a key step for the simulation of the immune response, because it determines immunogenicity. The binding of the epitope, which is the immunogenic part of an invading pathogen, together with activation and cooperation from T helper cells, is required to trigger an immune response in the affected host. To determine a pathogen's epitopes, we use existing prediction methods. In addition, we propose a novel method, which uses Miyazawa and Jernigan protein–protein potential measurements, for assessing molecular binding in the context of immune complexes. We benchmark the resulting model by simulating a classical immunization experiment that reproduces the development of immune memory. We also investigate the role of major histocompatibility complex (MHC) haplotype heterozygosity and homozygosity with respect to the influenza virus and show that there is an advantage to heterozygosity. Finally, we investigate the emergence of one or more dominating clones of lymphocytes in the situation of chronic exposure to the same immunogenic molecule and show that high affinity clones proliferate more than any other. These results show that the simulator produces dynamics that are stable and consistent with basic immunological knowledge. We believe that the combination of genomic information and simulation of the dynamics of the immune system, in one single tool, can offer new perspectives for a better understanding of the immune system.
Fructose and cardiometabolic disorders: the controversy will, and must, continue
Wiernsperger, Nicolas;Geloen, Alain;Rapin, Jean-Robert;
Clinics , 2010, DOI: 10.1590/S1807-59322010000700013
Abstract: the present review updates the current knowledge on the question of whether high fructose consumption is harmful or not and details new findings which further pushes this old debate. due to large differences in its metabolic handling when compared to glucose, fructose was indeed suggested to be beneficial for the diet of diabetic patients. however its growing industrial use as a sweetener, especially in soft drinks, has focused attention on its potential harmfulness, possibly leading to dyslipidemia, obesity, insulin resistance/metabolic syndrome and even diabetes. many new data have been generated over the last years, confirming the lipogenic effect of fructose as well as risks of vascular dysfunction and hypertension. fructose exerts various direct effects in the liver, affecting both hepatocytes and kupffer cells and resulting in non-alcoholic steatotic hepatitis, a well known precursor of the metabolic syndrome. hepatic metabolic abnormalities underlie indirect peripheral metabolic and vascular disturbances, for which uric acid is possibly the culprit. nevertheless major caveats exist (species, gender, source of fructose, study protocols) which are detailed in this review and presently prevent any firm conclusion. new studies taking into account these confounding factors should be undertaken in order to ascertain whether or not high fructose diet is harmful.
Des épées romaines dans la collection d’ Alise-Sainte-Reine
Rapin, Andre
Gladius , 2001, DOI: 10.3989/gladius.2001.79
Abstract: Not available La colección de armas recuperadas en las excavaciones de Alise-Sainte-Reine, impulsadas por Napoleón III, constituye un corpus heterogéneo. Algunas espadas célticas, en efecto, son varios siglos anteriores a los sucesos militares del 52 a.C. e incluso otras no son ni siquiera célticas. En concreto dos de ellas, soldadas por la corrosión y unidas por la lámina broncínea de una vaina de La Tène presentan características morfológicas peculiares. Su análisis tecnológico permite situarlas entre los antecesores de la familia de las espadas romanas. Una primera aproximación comparativa permite considerarlas como candidatos verosímiles para ilustrar el texto de Polibio sobre el gladius hispaniensis, esto es, armas republicanas muy anteriores al asedio de Alesia.
L'armement celtique en Europe: chronologie de son evolution technologique du Ve au Ier. s. av. J.-C
Rapin, André
Gladius , 1999, DOI: 10.3989/gladius.1999.13
Abstract: Not Available Las corrosiones peculiares del hierro han sido durante dos siglos un obstáculo infranqueable para el análisis y estudio de la mayoría de los documentos fundamentales de las culturas protohistoricas que emplearon este metal. La orientación actual de los nuevos tipos de laboratorios especializados en estas investigaciones permite superar progresivamente estas deficiencias, en particular en 10 referente al armamento. El continuo flujo de nuevos datos surgidos de los estudios tecnológicos permite cambiar la rnisma naturaleza de las documentación desde ahora accesible. Las mutaciones tecnológicas que se aprecian y las nuevas tipologias permiten en la actualidad alterar sustancialmente nuestra aproximación a las culturas bárbaras y nuestra percepción de sus contactos e influencias reciprocas con las civilizaciones mediterráneas.
C/EBPα Is Required for Long-Term Self-Renewal and Lineage Priming of Hematopoietic Stem Cells and for the Maintenance of Epigenetic Configurations in Multipotent Progenitors
Marie S. Hasemann,Felicia K. B. Lauridsen,Johannes Waage,Janus S. Jakobsen,Anne-Katrine Frank,Mikkel B. Schuster,Nicolas Rapin,Frederik O. Bagger,Philipp S. Hoppe,Timm Schroeder,Bo T. Porse
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004079
Abstract: Transcription factors are key regulators of hematopoietic stem cells (HSCs) and act through their ability to bind DNA and impact on gene transcription. Their functions are interpreted in the complex landscape of chromatin, but current knowledge on how this is achieved is very limited. C/EBPα is an important transcriptional regulator of hematopoiesis, but its potential functions in HSCs have remained elusive. Here we report that C/EBPα serves to protect adult HSCs from apoptosis and to maintain their quiescent state. Consequently, deletion of Cebpa is associated with loss of self-renewal and HSC exhaustion. By combining gene expression analysis with genome-wide assessment of C/EBPα binding and epigenetic configurations, we show that C/EBPα acts to modulate the epigenetic states of genes belonging to molecular pathways important for HSC function. Moreover, our data suggest that C/EBPα acts as a priming factor at the HSC level where it actively promotes myeloid differentiation and counteracts lymphoid lineage choice. Taken together, our results show that C/EBPα is a key regulator of HSC biology, which influences the epigenetic landscape of HSCs in order to balance different cell fate options.
Robust Sparse Blind Source Separation
Cecile Chenot,Jerome Bobin,Jeremy Rapin
Computer Science , 2015, DOI: 10.1109/LSP.2015.2463232
Abstract: Blind Source Separation is a widely used technique to analyze multichannel data. In many real-world applications, its results can be significantly hampered by the presence of unknown outliers. In this paper, a novel algorithm coined rGMCA (robust Generalized Morphological Component Analysis) is introduced to retrieve sparse sources in the presence of outliers. It explicitly estimates the sources, the mixing matrix, and the outliers. It also takes advantage of the estimation of the outliers to further implement a weighting scheme, which provides a highly robust separation procedure. Numerical experiments demonstrate the efficiency of rGMCA to estimate the mixing matrix in comparison with standard BSS techniques.
New constructions of domain decomposition methods for systems of PDEs
Victorita Dolean,Frédéric Nataf,Gerd Rapin
Physics , 2005,
Abstract: We propose new domain decomposition methods for systems of partial differential equations in two and three dimensions. The algorithms are derived with the help of the Smith factorization of the operator. This could also be validated by numerical experiments.
Sparsity and adaptivity for the blind separation of partially correlated sources
Jerome Bobin,Jeremy Rapin,Anthony Larue,Jean-Luc Starck
Computer Science , 2014, DOI: 10.1109/TSP.2015.2391071
Abstract: Blind source separation (BSS) is a very popular technique to analyze multichannel data. In this context, the data are modeled as the linear combination of sources to be retrieved. For that purpose, standard BSS methods all rely on some discrimination principle, whether it is statistical independence or morphological diversity, to distinguish between the sources. However, dealing with real-world data reveals that such assumptions are rarely valid in practice: the signals of interest are more likely partially correlated, which generally hampers the performances of standard BSS methods. In this article, we introduce a novel sparsity-enforcing BSS method coined Adaptive Morphological Component Analysis (AMCA), which is designed to retrieve sparse and partially correlated sources. More precisely, it makes profit of an adaptive re-weighting scheme to favor/penalize samples based on their level of correlation. Extensive numerical experiments have been carried out which show that the proposed method is robust to the partial correlation of sources while standard BSS techniques fail. The AMCA algorithm is evaluated in the field of astrophysics for the separation of physical components from microwave data.
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