Internalization and induction of antioxidant messages by microvesicles contribute to the antiapoptotic effects on human endothelial cells

Microvesicles are plasma membrane-derived fragments released from various cell types during activation and/or apoptosis and posses the ability to deliver biological information between cells. Microvesicles generated from T lymphocytes undergoing activation and apoptosis bear the morphogen Sonic Hedgehog, and exert a beneficial potential effect on the cardiovascular system through their dual capacity to increase nitric oxide and reduce reactive oxygen species production. This study investigated the effect of microvesicles on the apoptosis of human umbilical vein endothelial cells triggered by actinomycin D. Microvesicles prevented apoptosis induced by actinomycin D by modulating reactive oxygen species production: during the early phase of apoptosis, microvesicles might act directly as reactive oxygen species scavengers, owing to their ability to carry active antioxidant enzymes, catalase, and isoforms of the superoxide dismutase. Furthermore, their effects were associated with the ability to increase the expression of manganese-superoxide dismutase in endothelial cells, through the internalization process. Interestingly, microvesicles bearing Sonic Hedgehog induced cytoprotection in endothelial cells through the activation of the Sonic Hedgehog pathway. These findings provide additional evidence that microvesicles from T lymphocytes exert their vasculoprotective effects by promoting internalization and induction of antioxidant messages to the endothelial monolayer

Anisotropic Decay Dynamics of Photoexcited Aligned Carbon Nanotube Bundles

We have performed polarization-dependent ultrafast pump-probe spectroscopy of a film of aligned single-walled carbon nanotube bundles. By taking into account imperfect nanotube alignment as well as anisotropic absorption cross sections, we quantitatively determined distinctly different photo-bleaching dynamics for polarizations parallel and perpendicular to the tube axis. For perpendicular polarization, we observe a slow (1.0-1.5 ps) relaxation process, previously unobserved in randomly-oriented nanotube bundles. We attribute this slower dynamics to the excitation and relaxation of surface plasmons in the radial direction of the nanotube bundles.Comment: 4 pages, 3 figure

Quine, Ontology, and Physicalism

Quine's views on ontology and naturalism are well-known but rarely considered in tandem. According to my interpretation the connection between them is vital. I read Quine as a global epistemic structuralist. Quine thought we only ever know objects qua solutions to puzzles about significant intersections in observations. Objects are always accessed descriptively, via their roles in our best theory. Quine's Kant lectures contain an early version of epistemic structuralism with uncharacteristic remarks about the mental. Here Quine embraces mitigated anomalous monism, allowing introspection and the availability in principle of full physical descriptions of the perceptual states which get science off the ground. Later versions abandon these ideas. My epistemic-structural interpretation explains why. I argue first-personal introspective access to mental states is incompatible with global epistemic structuralism

Near-field BLEVE overpressure effects: The shock start model

International audienceThis paper presents the results of a small scale experimental study of BLEVE overpressure effects. Testing consisted of a sealed aluminum tube (0.6 L) filled with either water or propane, being heated by a flame until the internal pressure led to catastrophic failure and explosion. Three parameters were controlled during the experiments: the failing pressure, the weakened length on the tube and the fill level. BLEVEs were obtained with tests involving water and propane. Blast gages and optical techniques were used to characterize the shock wave escaping from the failing tube. The results obtained suggest that the lead shock was primarily generated by the vapor space. Overpressure results obtained were compared with the predictions of existing models and found to be in reasonable agreement except for overpressures measured vertically above the cylinder where the overpressures were highest. A prediction model based on only vapor space characteristics was developed. Images show that the shock was fully formed at some distance away from the vessel opening and this was due to the non-ideal opening of the vessel. The model developed was based on the characteristics of the shock when fully formed away from the tube. These characteristics were defined using a combination of imaging, pressure measurements, and predictions from shock tube theory

Pro-angiogenic effet of N,N-diethyl-m-toluamide (DEET) mediated by M3 receptors

National audienc

Effects of N,N-diethyl-m-toluamide (DEET) in the cellular processes leading to angiogenesis

National audienc

Transfer of antioxidant message by microvesicles mediates antiapoptotic effects on human endothelial cells

Microvesicles (MVs) are small membrane-derived fragments shed from various cell types during activation and/or apoptosis and represent a new class of biological information mediators. MVs generated from T lymphocytes undergoing activation and apoptosis exert a beneficial potential effect on the cardiovascular system through their dual capacity to increase nitric oxide and reduce reactive oxygen species production. This study investigated the effect of MVs on the apoptosis of human umbilical vein endothelial cells triggered by actinomycin D (Act D). The effect of Act D treatment on reactive oxygen species (ROS) production was biphasic. Indeed, ROS levels significantly increased during the early phase of apoptosis (2 h) and after 10 h of treatment, but not at 4, 8 and 24 h. MVs significantly attenuated the increase in ROS production induced by Act D at 2 h, but not at 10 h, indicating that they normalize ROS production during the early phase of apoptosis by acting directly as ROS scavengers, owing to their ability to carry active antioxidant enzymes such as catalase and the three isoforms of the superoxide dismutase. Furthermore, the effects of MVs on the late phases of apoptosis were associated with the ability of these vesicles to increase the expression of manganese-superoxide dismutase, probably by the transfer of its mRNA, in endothelial cells, through internalization process. These findings illustrate new mechanisms by which MVs from T lymphocytes exert their vasculo-protective effects by improving endothelial function under pathological conditions in which apoptosis and oxidative stress are enhanced

Inferring periodic orbits from spectra of simple shaped micro-lasers

Dielectric micro-cavities are widely used as laser resonators and characterizations of their spectra are of interest for various applications. We experimentally investigate micro-lasers of simple shapes (Fabry-Perot, square, pentagon, and disk). Their lasing spectra consist mainly of almost equidistant peaks and the distance between peaks reveals the length of a quantized periodic orbit. To measure this length with a good precision, it is necessary to take into account different sources of refractive index dispersion. Our experimental and numerical results agree with the superscar model describing the formation of long-lived states in polygonal cavities. The limitations of the two-dimensional approximation are briefly discussed in connection with micro-disks.Comment: 13 pages, 19 figures, accepted for publication in Physical Review

Nuclear suppression of heavy quark production at forward rapidities in relativistic heavy ion collisions

We calculate nuclear suppression $R_{AA}$ of heavy quarks produced from the initial fusion of partons in nucleus-nucleus collisions at RHIC and LHC energies. We take the shadowing as well as the energy loss suffered by them while passing through Quark Gluon Plasma into account. We obtain results for charm and bottom quarks at several rapidities using different mechanisms for energy loss, to see if we can distinguish between them.Comment: 21 pages including 13 figures. To appear in J. Phys.