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, $\sigma_\mathrm{r}$ = 10, the shape always remains prolate, including when the field is turned off. For $\sigma_\mathrm{r} = 0.1$ and the electric field strength $\beta$ (the ratio of electric to viscous force), $\beta \beta_c$, 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'âge médicolégal grâce à l'étude de la méthylation de l'ADN : revue de la littérature

International audienceL'estimation d'un âge médicolégal est un paramètre clé (fournissant des informa-tions utiles) pour les enquêtes criminelles, juridiques et anthropologiques. L'âge médicolégal peut être défini comme le reflet de l'âge biologique (et non chronologique) d'un individu dans un contexte de recherche judiciaire. Cette estimation initialement basée sur l'étude morpholo-gique, la radiographie osseuse mais également dentaire, s'est tournée depuis 5 ans vers le domaine de l'épigénétique médicolégale. L'analyse de la méthylation de l'ADN est actuellement le meilleur moyen de prédire un âge chronologique. Le développement d'approches molécu-laires pour l'étude de cette méthylation ne cesse de croître et à ce jour plus de 20 publications ont montré une corrélation positive entre vieillissement et changement de méthylation à l'échelle du CpG. Dans cette revue, nous résumons les données de la littérature portant sur l'identification et le développement de marqueurs corrélés à l'âge dans le sang et dans d'autres tissus. Nous recensons aussi les techniques d'études avec leurs avantages et leurs inconvénients

Intérêt de la présence d'une équipe spécialisée pour la levée de corps en anthropologie médico-légale

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 générer des accidents pour les salariés ou des tiers. Ce risque est d’autant plus élevé que le salarié occupe un poste de sûreté/sécurité. La mise en évidence de consommations repose sur le repérage clinique et sur le dépistage biologique. Ce dernier a fait l’objet d’avancées mais aussi de controverses ces dernières années. Les auteurs font le point sur les dernières avancées en la matière.MéthodesAprès une présentation des données épidémiologiques récentes et des effets des principales SPA, les auteurs discutent les dernières avancées technologiques en matière de dépistage, analysent les recommandations du Comité consultatif national d’éthique (CCNE) ainsi que les différents textes législatifs relatifs à la mise en évidence d’une consommation de SPA en milieu professionnel.RésultatsAlors que les modalités de dépistage ainsi que la réglementation concernant l’usage de l’alcool en milieu professionnel n’ont pas connu récemment de modifications majeures, le dépistage salivaire des stupéfiants, dont les performances se sont améliorées, se généralise au détriment du dépistage urinaire, car il est simple à réaliser et plus respectueux de l’intimité de la personne. Le CCNE reconnaît le dépistage salivaire comme acceptable sur le plan éthique et se positionne en sa faveur, alors que les différents textes réglementaires s’orientent plutôt vers un renforcement des actions de prévention. De nombreuses incertitudes persistent donc encore quant au statut du dépistage, rendant parfois difficile le positionnement du médecin du travail

Mechanisms of hyoid bone fracture after modelling: Evaluation of anthropological criteria defining two relevant models

Several studies have attempted to describe the morphology of the hyoid bone, while other authors have focused on discovering the role of this bone in the occurrence of fractures. Hyoid fractures are known to be dependent on the force applied against the bone, or on the location at which the force is applied. We wished to assess the value of defining one or more models of the hyoid bone by analyzing variations in the size and angle of the various component parts of the bone relative to the sex and morphology of an individual (height and weight) in a sample of 72 bones obtained during forensic autopsy at our institution. Statistical analyses were developed using SAS software (Statistical Analysis System, version 9.2). We observed that the length of the hyoid bone and the angle between the greater horns differed significantly between men and women. Length was significantly greater in men (38.20 +/- 4.67 mm) than in women (30.49 +/- 7.90 mm) and the angle between the greater horns of the hyoid bone was larger in women (36.46 +/- 13.77 degrees) than in men (27.56 +/- 13.02 degrees). There was also a statistically significant correlation between the body mass index of an individual and the length of the hyoid bone. As weight increased, the hyoid bone was found to be longer. The weight of an individual was also significantly correlated with the angle of the hyoid bone, with lower weight resulting in larger angles of the bone. Furthermore, hierarchical classification enabled the hyoid bone to be differentiated into two groups or clusters according to anthropometric measurements. ROC curves were used to determine threshold values of length, width and angle to classify the hyoid bones in these two clusters: the first was composed of individuals with longer hyoid bones, and the second of individuals with greater hyoid bone widths and wider angles. Logistic regression showed male gender was more frequently associated with the first group. The morphology of the hyoid bone can be differentiated according to the gender and corpulence of an individual because these parameters are correlated. These findings are crucial in establishing a protocol for modelling the mechanism of fracture of the hyoid bone in strangulation. Two models of the hyoid bone appear to be needed to meet the practical requirements that are the purpose of these biomechanical studies