Vascular and liver homeostasis in juvenile mice require endothelial cyclic AMP-dependent protein kinase A

During vascular development, endothelial cAMP-dependent protein kinase A (PKA) regulates angiogenesis by controlling the number of tip cells, and PKA inhibition leads to excessive angiogenesis. Whether this role of endothelial PKA is restricted to embryonic and neonatal development or is also required for vascular homeostasis later on is unknown. Here, we show that perinatal (postnatal days P1-P3) of later (P28-P32) inhibition of endothelial PKA using dominant-negative PKA expressed under the control of endothelial-specific Cdh5-CreERT2 recombinase (dnPKA(iEC) mice) leads to severe subcutaneous edema, hypoalbuminemia, hypoglycemia and premature death. These changes were accompanied by the local hypersprouting of blood vessels in fat pads and the secondary enlargement of subcutaneous lymphatic vessels. Most noticeably, endothelial PKA inhibition caused a dramatic disorganization of the liver vasculature. Hepatic changes correlated with decreased gluconeogenesis, while liver albumin production seems to be unaffected and hypoalbuminemia is rather a result of increased leakage into the interstitium. Interestingly, the expression of dnPKA only in lymphatics using Prox1-CreERT2 produced no phenotype. Likewise, the mosaic expression in only endothelial subpopulations using Vegfr3-CreERT2 was insufficient to induce edema or hypoglycemia. Increased expression of the tip cell marker ESM1 indicated that the inhibition of PKA induced an angiogenic response in the liver, although tissue derived pro- and anti-angiogenic factors were unchanged. These data indicate that endothelial PKA is a gatekeeper of endothelial cell activation not only in development but also in adult homeostasis, preventing the aberrant reactivation of the angiogenic program

Caspase-8 binding to cardiolipin in giant unilamellar vesicles provides a functional docking platform for bid

Caspase-8 is involved in death receptor-mediated apoptosis in type II cells, the proapoptotic programme of which is triggered by truncated Bid. Indeed, caspase-8 and Bid are the known intermediates of this signalling pathway. Cardiolipin has been shown to provide an anchor and an essential activating platform for caspase-8 at the mitochondrial membrane surface. Destabilisation of this platform alters receptor-mediated apoptosis in diseases such as Barth Syndrome, which is characterised by the presence of immature cardiolipin which does not allow caspase-8 binding. We used a simplified in vitro system that mimics contact sites and/or cardiolipin-enriched microdomains at the outer mitochondrial surface in which the platform consisting of caspase-8, Bid and cardiolipin was reconstituted in giant unilamellar vesicles. We analysed these vesicles by flow cytometry and confirm previous results that demonstrate the requirement for intact mature cardiolipin for caspase-8 activation and Bid binding and cleavage. We also used confocal microscopy to visualise the rupture of the vesicles and their revesiculation at smaller sizes due to alteration of the curvature following caspase-8 and Bid binding. Biophysical approaches, including Laurdan fluorescence and rupture/tension measurements, were used to determine the ability of these three components (cardiolipin, caspase-8 and Bid) to fulfil the minimal requirements for the formation and function of the platform at the mitochondrial membrane. Our results shed light on the active functional role of cardiolipin, bridging the gap between death receptors and mitochondria

The synthetic peptide P111-136 derived from the C-terminal domain of heparin affin regulatory peptide inhibits tumour growth of prostate cancer PC-3 cells

<p>Abstract</p> <p>Background</p> <p>Heparin affin regulatory peptide (HARP), also called pleiotrophin, is a heparin-binding, secreted factor that is overexpressed in several tumours and associated to tumour growth, angiogenesis and metastasis. The C-terminus part of HARP composed of amino acids 111 to 136 is particularly involved in its biological activities and we previously established that a synthetic peptide composed of the same amino acids (P111-136) was capable of inhibiting the biological activities of HARP. Here we evaluate the ability of P111-136 to inhibit <it>in vitro </it>and <it>in vivo </it>the growth of a human tumour cell line PC-3 which possess an HARP autocrine loop.</p> <p>Methods</p> <p>A total lysate of PC-3 cells was incubated with biotinylated P111-136 and pulled down for the presence of the HARP receptors in Western blot. <it>In vitro</it>, the P111-136 effect on HARP autocrine loop in PC-3 cells was determined by colony formation in soft agar. <it>In vivo</it>, PC-3 cells were inoculated in the flank of athymic nude mice. Animals were treated with P111-136 (5 mg/kg/day) for 25 days. Tumour volume was evaluated during the treatment. After the animal sacrifice, the tumour apoptosis and associated angiogenesis were evaluated by immunohistochemistry. <it>In vivo </it>anti-angiogenic effect was confirmed using a mouse Matrigel™ plug assay.</p> <p>Results</p> <p>Using pull down experiments, we identified the HARP receptors RPTPβ/ζ, ALK and nucleolin as P111-136 binding proteins. <it>In vitro</it>, P111-136 inhibits dose-dependently PC-3 cell colony formation. Treatment with P111-136 inhibits significantly the PC-3 tumour growth in the xenograft model as well as tumour angiogenesis. The angiostatic effect of P111-136 on HARP was also confirmed using an <it>in vivo </it>Matrigel™ plug assay in mice</p> <p>Conclusions</p> <p>Our results demonstrate that P111-136 strongly inhibits the mitogenic effect of HARP on <it>in vitro </it>and <it>in vivo </it>growth of PC-3 cells. This inhibition could be linked to a direct or indirect binding of this peptide to the HARP receptors (ALK, RPTPβ/ζ, nucleolin). <it>In vivo</it>, the P111-136 treatment significantly inhibits both the PC-3 tumour growth and the associated angiogenesis. Thus, P111-136 may be considered as an interesting pharmacological tool to interfere with tumour growth that has now to be evaluated in other cancer types.</p

Dynamic endothelial cell rearrangements drive developmental vessel regression

Patterning of functional blood vessel networks is achieved by pruning of superfluous connections. The cellular and molecular principles of vessel regression are poorly understood. Here we show that regression is mediated by dynamic and polarized migration of endothelial cells, representing anastomosis in reverse. Establishing and analyzing the first axial polarity map of all endothelial cells in a remodeling vascular network, we propose that balanced movement of cells maintains the primitive plexus under low shear conditions in a metastable dynamic state. We predict that flow-induced polarized migration of endothelial cells breaks symmetry and leads to stabilization of high flow/shear segments and regression of adjacent low flow/shear segments.status: publishe

Utilisation des cannes dérivées du tube de pitot pour l'étude des débits dans les conduites

1. The author states the problem as having to determine a simple instrument capable of being introduced without difficulty and at little cost at any point in the pipes constituting the Paris Prefecture's water distribution loop system. His choice fell on a cylindrical tube derived from the Pitot tube, featuring two dynamic pressure tappings and no static pressure hole in order to increase the differential pressure. 2. On calibrating this probe in an infinite medium in the French Navy's hull testing tank, it was found that the conventional formula Q = K D2 Ha relating discharge to average velocity Vm gave two values of the exponent a, both of which were dose to 1/2, and that the discontinuity invariably occurred at a velocity in the neighbourhood of 1 m/sec. 3. The author decided to always measure the velocity in the centre Vo in order to reduce the margin of uncertainty to a minimum. He made measurements on a large number of pipes with widely varying velocity distribution curves in order to determine the maximum probable variation range of coefficient v = mean velocity/central velocity 4. The author was then able to plot a graph consisting of a family of straight lines on a double logarithmic scale, the spacing of which was related to pipe diameter by a parabolic law. 5. The author then goes on to show successive applications of the probe in the Paris Prefecture's water distribution system, including one probe permanently installed in a 1.5 m diameter pipe. 6. Finally, the author argues in favour of the use of these probes for investigation and supervisory purposes and not as precision instruments-as a means of establishing basic requirements for operation ensuring optimum running economy, combined with satisfactory service to the consumer

Shape change and physical properties of giant phospholipid vesicles prepared in the presence of an AC electric field.

Giant unilamellar vesicles with diameters ranging from 10 to 60 microns were obtained by the swelling of phospholipid bilayers in water in the presence of an AC electric field. This technique leads to a homogeneous population of perfectly spherical and unilamellar vesicles, as revealed by phase-contrast optical microscopy and freeze-fracture electron microscopy. Freshly prepared vesicles had a high surface tension with no visible surface undulations. Undulations started spontaneously after several hours of incubation or were triggered by the application of a small osmotic pressure. Partially deflated giant vesicles could undergo further shape change if asymmetrical bilayers were formed by adding lyso compounds to the external leaflet or by imposing a transmembrane pH gradient that selectively accumulates on one leaflet phosphatidylglycerol. Fluorescence photobleaching with 7-nitrobenz-2-oxa-1,3-diazol-4-yl-labeled phospholipids or labeled dextran trapped within the vesicles enabled the measurement of the membrane continuity in the dumbbell-shaped vesicles. In all instances phospholipids diffused from one lobe to the other, but soluble dextran sometimes was unable to traverse the neck. This suggests that the diameter of the connecting neck may be variable

How lipid asymmetry can make vesicles fusion-competent by inhibition of the thermal undulations

International audienc

Angiopoietin-like 4 serum levels on admission for acute myocardial infarction are associated with no-reflow assessed by magnetic resonance imaging

Background: No-reflow in ST-segment elevation acute myocardial infarction (STEMI) is associated with a poor clinical prognosis. Its pathophysiologal mechanism

Clé d’identification illustrée des écailles de scinques de Nouvelle-Calédonie

International audience- L'élaboration de la clé d'identification des écailles de scinques de Nouvelle-Calédonie s'inscrit dans le cadre du programme Rmines : "Impacts des espèces invasives sur les reptiles des massifs miniers, application à la conservation durable d’un patrimoine faunistique exceptionnel et menacé." - Cette clé dichotomique est conçue dans le but d’identifier les macro-restes de Scincidaeretrouvés dans les fèces et contenus stomacaux de prédateurs introduits - chat haret (Felis silvestriscatus) et rongeurs (Rattus spp.).- Elle a été réalisée à partir du croisement des données analysées à partir de photographiesd’écailles au microscope électronique à balayage (SEM) provenant de 39 espèces de Scincidae parmiles 63 actuellement décrites en Nouvelle-Calédonie. Cette clé s'appuie également sur la constitutiond'une collection de référence d'écailles montées sur lames microscopiques (49 taxons). Afin decompléter le diagnostic, nous proposons des photographies réalisées à la loupe binoculaire d’écaillescrâniennes typiques pour les différents genres, ainsi que des informations de répartition pour lesdifférentes espèces (données issues de la littérature et des spécimens en collection (AustralianMuseum)).- Par ailleurs, les patrons d’écailles digitales des pattes antérieures et postérieures pour les 46mêmes espèces sont également présentés. Toutes les écailles ont été prélevées – et les clichés réalisés– sur des scinques de la collection de référence de l’Australian Museum ou de celle en cours deconstitution à l’IMBE-IRD à Nouméa