The P2Y12 receptor induces platelet aggregation through weak activation of the αIIbβ3 integrin – a phosphoinositide 3-kinase-dependent mechanism

AbstractHigh concentrations of adenosine-5′-diphosphate ADP are able to induce partial aggregation without shape change of P2Y1 receptor-deficient mouse platelets through activation of the P2Y12 receptor. In the present work we studied the transduction pathways selectively involved in this phenomenon. Flow cytometric analyses using R-phycoerythrin-conjugated JON/A antibody (JON/A-PE), an antibody which recognizes activated mouse αIIbβ3 integrin, revealed a low level activation of αIIbβ3 in P2Y1 receptor-deficient platelets in response to 100 μM ADP or 1 μM 2MeS-ADP. Adrenaline induced no such activation but strongly potentiated the effect of ADP in a dose-dependent manner. Global phosphorylation of 32P-labeled platelets showed that P2Y12-mediated aggregation was not accompanied by an increase in the phosphorylation of myosin light chain (P20) or pleckstrin (P47) and was not affected by the protein kinase C (PKC) inhibitor staurosporine. On the other hand, two unrelated phosphoinositide 3-kinase inhibitors, wortmannin and LY294002, inhibited this aggregation. Our results indicate that (i) the P2Y12 receptor is able to trigger a P2Y1 receptor-independent inside-out signal leading to αIIbβ3 integrin activation and platelet aggregation, (ii) ADP and adrenaline use different signaling pathways which synergize to activate the αIIbβ3 integrin, and (iii) the transduction pathway triggered by the P2Y12 receptor is independent of PKC but dependent on phosphoinositide 3-kinase

A new variational approach to the stability of gravitational systems

We consider the three dimensional gravitational Vlasov Poisson system which describes the mechanical state of a stellar system subject to its own gravity. A well-known conjecture in astrophysics is that the steady state solutions which are nonincreasing functions of their microscopic energy are nonlinearly stable by the flow. This was proved at the linear level by several authors based on the pioneering work by Antonov in 1961. Since then, standard variational techniques based on concentration compactness methods as introduced by P.-L. Lions in 1983 have led to the nonlinear stability of subclasses of stationary solutions of ground state type. In this paper, inspired by pioneering works from the physics litterature (Lynden-Bell 94, Wiechen-Ziegler-Schindler MNRAS 88, Aly MNRAS 89), we use the monotonicity of the Hamiltonian under generalized symmetric rearrangement transformations to prove that non increasing steady solutions are local minimizer of the Hamiltonian under equimeasurable constraints, and extract compactness from suitable minimizing sequences. This implies the nonlinear stability of nonincreasing anisotropic steady states under radially symmetric perturbations

A system of ODEs for a Perturbation of a Minimal Mass Soliton

We study soliton solutions to a nonlinear Schrodinger equation with a saturated nonlinearity. Such nonlinearities are known to possess minimal mass soliton solutions. We consider a small perturbation of a minimal mass soliton, and identify a system of ODEs similar to those from Comech and Pelinovsky (2003), which model the behavior of the perturbation for short times. We then provide numerical evidence that under this system of ODEs there are two possible dynamical outcomes, which is in accord with the conclusions of Pelinovsky, Afanasjev, and Kivshar (1996). For initial data which supports a soliton structure, a generic initial perturbation oscillates around the stable family of solitons. For initial data which is expected to disperse, the finite dimensional dynamics follow the unstable portion of the soliton curve.Comment: Minor edit

Resistance de l'oidium de la vigne aux fongicides IBS : situation en 1991 et perspectives pour 1992

National audienc

Resistance de l'oidium de la vigne aux fongicides IBS : situation en 1991 et perspectives pour 1992

National audienc

Modelling of Hfe avalanche degradation in gate controlled bipolar transistors

The avalanche degradation phenomenon model presented here takes into account both : an increase of surface recombination rate localized near the initial intrinsic point in the junction transition region surface and a displacement of the intrinsic point due to the oxide injected charge. A method for the determination of parameters of the model is presented. The modelling results are given for uniform surface state density increase and for an other distribution. This model is used to improve the design of memory cells devices using this phenomenon

Simple determination of BJT extrinsic base resistance

International audienc

Modelling of Hfe avalanche degradation in gate controlled bipolar transistors

The avalanche degradation phenomenon model presented here takes into account both : an increase of surface recombination rate localized near the initial intrinsic point in the junction transition region surface and a displacement of the intrinsic point due to the oxide injected charge. A method for the determination of parameters of the model is presented. The modelling results are given for uniform surface state density increase and for an other distribution. This model is used to improve the design of memory cells devices using this phenomenon.Modélisation de la dégradation par avalanche du gain HFE d'un transistor bipolaire à grille de contrôle. Le modèle du phénomène de dégradation par avalanche présenté ici prend en compte à la fois l'augmentation de la vitesse de recombinaison en surface localisée près du point intrinsèque dans la zone de transition surfacique de la jonction et le déplacement du point intrinsèque dû à la charge injectée dans l'oxyde. On présente une méthode de détermination des paramètres du modèle. On donne les résultats de la modélisation pour une augmentation uniforme de la densité des états de surface et pour une distribution gaussienne. Ce modèle est utilisé pour améliorer la conception de points mémoires basés sur ce phénomène