Graphical Requirements for Multistationarity in Reaction Networks and their Verification in BioModels

International audienceThomas's necessary conditions for the existence of multiple steady states in gene networks have been proved by Soulé with high generality for dynamical systems defined by differential equations. When applied to (protein) reaction networks however, those conditions do not provide information since they are trivially satisfied as soon as there is a bimolecular or a reversible reaction. Refined graphical requirements have been proposed to deal with such cases. In this paper, we present for the first time a graph rewriting algorithm for checking the refined conditions given by Soliman, and evaluate its practical performance by applying it systematically to the curated branch of the BioModels repository. This algorithm analyzes all reaction networks (of size up to 430 species) in less than 0.05 second per network, and permits to conclude to the absence of multistationarity in 160 networks over 506. The short computation times obtained in this graphical approach are in sharp contrast to the Jacobian-based symbolic computation approach. We also discuss the case of one extra graphical condition by arc rewiring that allows us to conclude on 20 more networks of this benchmark but with a high computational cost. Finally, we study with some details the case of phosphorylation cycles and MAPK signalling models which show the importance of modelling the intermediate complexations with the enzymes in order to correctly analyze the multistationarity capabilities of such biochemical reaction networks

NG2-expressing glial precursor cells are a new potential oligodendroglioma cell initiating population in N-ethyl-N-nitrosourea-induced gliomagenesis.: Brain precursor cells and gliomas

International audienceGliomas are the most common primary brain tumor affecting human adults and remain a therapeutic challenge because cells of origin are still unknown. Here, we investigated the cellular origin of low-grade gliomas in a rat model based on transplacental exposure to N-ethyl-N-nitrosourea (ENU). Longitudinal magnetic resonance imaging coupled to immunohistological and immunocytochemical analyses were used to further characterize low-grade rat gliomas at different stages of evolution. We showed that early low-grade gliomas have characteristics of oligodendroglioma-like tumors and exclusively contain NG2-expressing slow dividing precursor cells, which express early markers of oligodendroglial lineage. These tumor-derived precursors failed to fully differentiate into oligodendrocytes and exhibited multipotential abilities in vitro. Moreover, a few glioma NG2+ cells are resistant to radiotherapy and may be responsible for tumor recurrence, frequently observed in humans. Overall, these findings suggest that transformed multipotent NG2 glial precursor cell may be a potential cell of origin in the genesis of rat ENU-induced oligodendroglioma-like tumors. This work may open up new perspectives for understanding biology of human gliomas

L'élan (Alces alces ssp.) (bilan d'enquête et maintien en captivité)

NANTES-Ecole Nat.Vétérinaire (441092302) / SudocPARIS-Museum-Bib zoologie mam. (751052312) / SudocSudocFranceF

Baromètre santé 2000 : les comportements des 12-25 ans. 3.1 : Synthèse des résultats nationaux et régionaux

217 p., fig., ill.Cet ouvrage en deux volumes (3.1 et 3.2) s'adresse à tous les acteurs et décideurs de santé publique qui souhaitent approfondir leurs connaissances sur la santé des jeunes tels que ceux-ci la déclarent et la perçoivent. Après l'édition des deux ouvrages Méthode (volume 1) et Résultats (volume 2), ces deux volumes décrivent les résultats d'une analyse secondaire des comportements, attitudes, connaissances et opinions des jeunes âgés de 12 à 25 ans en matière de santé. Le premier est consacré aux données nationales et se propose de dresser un portrait des pratiques de cette population dans le domaine de la vaccination, des consommations de tabac, d'alcool, de cannabis ou encore dans le domaine de la contraception. Les analyses portent également sur des indicateurs de santé comme la santé perçue, la qualité de vie mais aussi les violences subies ou les pensées suicidaires. Le second présente, de façon détaillée et pour ces mêmes thématiques, les données de quatre régions ayant bénéficié d'un sur-échantillon (Alsace, Nord-Pas-de-Calais, Pays de la Loire, Picardie). Ce dernier travail, réalisé pour les observatoires régionaux de la Santé, a permis par la première fois d'effectuer des comparaisons interrégionales en matière de comportements de santé

Evaluation of a dedicated software for semiautomated VMAT planning of spine Stereotactic Body Radiotherapy (SBRT)

International audiencePurpose: To determine whether SBRT of spinal metastasis using a dedicated treatment planning system (TPS) and delivered with a gantry-based LINAC could provide plans of similar quality to the Cyberknife technology. Additional comparison was also done with other commercial TPS used for volumetric modulated arc therapy (VMAT) planning.Materials and Methods: Thirty Spine SBRT patients, previously treated in our institution with CyberKnife (Accuray, Sunnyvale) using Multiplan TPS, were replanned in VMAT with an dedicated TPS (Elements Spine SRS, Brainlab, Munich) and our clinical TPS (Monaco, Elekta LTD, Stockholm), using exactly the same arc geometry. The comparison was done by assessing differences in dose delivered to PTV, CTV and spinal cord, calculating modulation complexity scores (MCS) and performing quality control (QA) of the plans.Results: Regardless of the vertebra level, in general, no statistical difference was found in PTV coverage between all TPS. Conversely, PTV and CTV D50% were found significantly higher for the dedicated TPS compared to others. In addition, the dedicated TPS also resulted in better gradient index (GI) than clinical VMAT TPS, whatever the vertebral level, and better GI than Cyberknife TPS for the thoracic level only. The D2% to the spinal cord was generally significantly lower with the dedicated TPS compared with others. No significant difference was found in the MCS between both VMAT TPS. All QA were clinically acceptable.Conclusion: The Elements Spine SRS TPS offers very effective and user-friendly semi-automated planning tools and is secure and promising for gantry-based LINAC spinal SBRT

Diagnostic précoce de la maladie d’Alzheimer : l’arbre qui cache la forêt ?

National audienc

Pixelated sintering of α-Al2O3

International audienceThe sintering of α-alumina by a brand new and innovative technique, called pixelated sintering (PS), is here studied. Densification and grain growth by PS of perfectly controlled granular compacts are analysed and compared to results obtained using Spark Plasma Sintering (SPS) and Pressure-Less SPS (PL-SPS). Materials are exposed to the same temperature profiles whatever the sintering technique used in order to assess the potential of PS in terms of microstructure control. It is shown that PS can be used as an alternative technique to SPS for fast sintering with the advantages of a much simpler and cost-effective setup , as well as a better control of the localised heat input. PS also appears to be a very modular technology in the way it controls the temperature gradients allowing its implementation for multi-step sintering approaches, as well as for the fabrication of large and complex parts