18 research outputs found
Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow
We review modeling of astrocyte ion dynamics with a specific focus on the
implications of so-called spatial potassium buffering, where excess potassium
in the extracellular space (ECS) is transported away to prevent pathological
neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for
modeling ion dynamics in astrocytes (and brain tissue in general) is outlined
and used to study such spatial buffering. We next describe how the ion dynamics
of astrocytes may regulate microscopic liquid flow by osmotic effects and how
such microscopic flow can be linked to whole-brain macroscopic flow. We thus
include the key elements in a putative multiscale theory with astrocytes
linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure
Influence of specific ionic diffusion on the protein self-aggregation instability
Transcellular currents are involved in the generation of spatial
order during the growth of numerous biological cells. A dynamic instability
triggered by the aggregation of the proteins may be at the origin of the
symmetry breaking. An analysis in terms of a semi-microscopic model is performed.
It reveals that the dynamics of the ion transferred by the mobile proteins,
pumps or channels, is of paramount importance. The diffusion currents play
a crucial role in the critical behaviour, even if the instability mechanism
is of electric origin. When the diffusion coefficients of the different species
are different, our results do not agree with those of the classical cable
formalism
Dynamics of a deflated vesicle in bipolar pulsed electric field
submitted to Soft MatterGiant unilamellar vesicles (GUVs) under pulsed direct current (pulsed-DC) fields are promising biomimetic systems to investigate electroporation of cells and vesicles. A question of relevance is the shape deformation of a vesicle when a DC-pulse is applied. Previous theoretical studies have looked at vesicles in DC fields (which are not pulsed). However, a pulsed-DC field yields electric stresses that can push a long time prolate spheroidal shape into an oblate spheroid. In this work, we computationally investigate the deformation of a vesicle under unipolar, bipolar, and two-step unipolar pulses. Our study indicates that the transmembrane potential can be regulated using a bipolar pulsed-DC field. For the ratio of inner to outer fluid conductivity, = 10, the shape always remains prolate, including when the field is turned off. For and the electric field strength (the ratio of electric to viscous force), , a metastable oblate equilibrium shape is predicted in pulsed-DC fields similar to that in the DC field. A prolate-to-oblate transition on turning off the field is an important characteristic of the dynamics in unipolar and bipolar pulsed-DC electric fields. When a two-step unipolar pulse (a combination of a strong and a weak subpulse) is applied, a vesicle can reach an oblate or a prolate final shape depending upon the relative durations of the two subpulses. The simulation results can be demonstrated in an experiment under typical experimental conditions
Ice Pile-Up at Stonehaven Harbour, New Brunswick: Ice Survey Report
prepared for National Research Council Canadapr\ue9par\ue9 pour le Conseil national de recherches CanadaPeer reviewed: NoNRC publication: Ye
Child pedestrian anthropometry: evaluation of potential impact points during a crash
International audienceThis paper highlights potential impact points of a child pedestrian during a crash with a front end of a vehicle. Child anthropometry is defined for ages between 3 and 15 years. It is based on the measurement of 7 different segment body heights (knee, femur, pelvis, shoulder, neck, chin, vertex) performed on about 2000 French children. For each dimension, the 5th, 50th and 95th percentile values are reported and the corresponding linear regression lines are given. Then, these heights are confronted with three different vehicle shapes corresponding to a passenger car, a sport utility vehicle and a light truck in order to identify impact points. In particular, it is shown that the thigh is directly hit by the bumper for children above 12 years old whereas head impacts principally the hood. Influences of the child anthropometry on the pedestrian trajectory and comparison with tests procedure in regulation are also discussed. child, anthropometry, pedestrian, vehicle shape, acciden
Estimation de l'ùge médicolégal grùce à l'étude de la méthylation de l'ADN : revue de la littérature
International audienceL'estimation d'un Ăąge mĂ©dicolĂ©gal est un paramĂštre clĂ© (fournissant des informa-tions utiles) pour les enquĂȘtes criminelles, juridiques et anthropologiques. L'Ăąge mĂ©dicolĂ©gal peut ĂȘtre dĂ©fini comme le reflet de l'Ăąge biologique (et non chronologique) d'un individu dans un contexte de recherche judiciaire. Cette estimation initialement basĂ©e sur l'Ă©tude morpholo-gique, la radiographie osseuse mais Ă©galement dentaire, s'est tournĂ©e depuis 5 ans vers le domaine de l'Ă©pigĂ©nĂ©tique mĂ©dicolĂ©gale. L'analyse de la mĂ©thylation de l'ADN est actuellement le meilleur moyen de prĂ©dire un Ăąge chronologique. Le dĂ©veloppement d'approches molĂ©cu-laires pour l'Ă©tude de cette mĂ©thylation ne cesse de croĂźtre et Ă ce jour plus de 20 publications ont montrĂ© une corrĂ©lation positive entre vieillissement et changement de mĂ©thylation Ă l'Ă©chelle du CpG. Dans cette revue, nous rĂ©sumons les donnĂ©es de la littĂ©rature portant sur l'identification et le dĂ©veloppement de marqueurs corrĂ©lĂ©s Ă l'Ăąge dans le sang et dans d'autres tissus. Nous recensons aussi les techniques d'Ă©tudes avec leurs avantages et leurs inconvĂ©nients
IntĂ©rĂȘt de la prĂ©sence d'une Ă©quipe spĂ©cialisĂ©e pour la levĂ©e de corps en anthropologie mĂ©dico-lĂ©gale
National audienc
Dépistage de la consommation de substances psychoactives en milieu professionnel : enjeux techniques, éthiques et réglementaires
ObjectifsLa consommation de substances psychoactives (SPA) en milieu professionnel peut gĂ©nĂ©rer des accidents pour les salariĂ©s ou des tiers. Ce risque est dâautant plus Ă©levĂ© que le salariĂ© occupe un poste de sĂ»retĂ©/sĂ©curitĂ©. La mise en Ă©vidence de consommations repose sur le repĂ©rage clinique et sur le dĂ©pistage biologique. Ce dernier a fait lâobjet dâavancĂ©es mais aussi de controverses ces derniĂšres annĂ©es. Les auteurs font le point sur les derniĂšres avancĂ©es en la matiĂšre.MĂ©thodesAprĂšs une prĂ©sentation des donnĂ©es Ă©pidĂ©miologiques rĂ©centes et des effets des principales SPA, les auteurs discutent les derniĂšres avancĂ©es technologiques en matiĂšre de dĂ©pistage, analysent les recommandations du ComitĂ© consultatif national dâĂ©thique (CCNE) ainsi que les diffĂ©rents textes lĂ©gislatifs relatifs Ă la mise en Ă©vidence dâune consommation de SPA en milieu professionnel.RĂ©sultatsAlors que les modalitĂ©s de dĂ©pistage ainsi que la rĂ©glementation concernant lâusage de lâalcool en milieu professionnel nâont pas connu rĂ©cemment de modifications majeures, le dĂ©pistage salivaire des stupĂ©fiants, dont les performances se sont amĂ©liorĂ©es, se gĂ©nĂ©ralise au dĂ©triment du dĂ©pistage urinaire, car il est simple Ă rĂ©aliser et plus respectueux de lâintimitĂ© de la personne. Le CCNE reconnaĂźt le dĂ©pistage salivaire comme acceptable sur le plan Ă©thique et se positionne en sa faveur, alors que les diffĂ©rents textes rĂ©glementaires sâorientent plutĂŽt vers un renforcement des actions de prĂ©vention. De nombreuses incertitudes persistent donc encore quant au statut du dĂ©pistage, rendant parfois difficile le positionnement du mĂ©decin du travail