1,307 research outputs found

    WNT5A regulates adipose tissue angiogenesis via antiangiogenic VEGF-A165b in obese humans

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    Experimental studies have suggested that Wingless-related integration site 5A (WNT5A) is a proinflammatory secreted protein that is associated with metabolic dysfunction in obesity. Impaired angiogenesis in fat depots has been implicated in the development of adipose tissue capillary rarefaction, hypoxia, inflammation, and metabolic dysfunction. We have recently demonstrated that impaired adipose tissue angiogenesis is associated with overexpression of antiangiogenic factor VEGF-A165b in human fat and the systemic circulation. In the present study, we postulated that upregulation of WNT5A is associated with angiogenic dysfunction and examined its role in regulating VEGF-A165b expression in human obesity. We biopsied subcutaneous and visceral adipose tissue from 38 obese individuals (body mass index: 44 ± 7 kg/m2, age: 37 ± 11 yr) during planned bariatric surgery and characterized depot-specific protein expression of VEGF-A165b and WNT5A using Western blot analysis. In both subcutaneous and visceral fat, VEGF-A165b expression correlated strongly with WNT5A protein (r = 0.9, P \u3c 0.001). In subcutaneous adipose tissue where angiogenic capacity is greater than in the visceral depot, exogenous human recombinant WNT5A increased VEGF-A165b expression in both whole adipose tissue and isolated vascular endothelial cell fractions (P \u3c 0.01 and P \u3c 0.05, respectively). This was associated with markedly blunted angiogenic capillary sprout formation in human fat pad explants. Moreover, recombinant WNT5A increased secretion of soluble fms-like tyrosine kinase-1, a negative regulator of angiogenesis, in the sprout media (P \u3c 0.01). Both VEGF-A165b-neutralizing antibody and secreted frizzled-related protein 5, which acts as a decoy receptor for WNT5A, significantly improved capillary sprout formation and reduced soluble fms-like tyrosine kinase-1 production (P \u3c 0.05). We demonstrated a significant regulatory nexus between WNT5A and antiangiogenic VEGF-A165b in the adipose tissue of obese subjects that was linked to angiogenic dysfunction. Elevated WNT5A expression in obesity may function as a negative regulator of angiogenesis

    Euclidean Distances, soft and spectral Clustering on Weighted Graphs

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    We define a class of Euclidean distances on weighted graphs, enabling to perform thermodynamic soft graph clustering. The class can be constructed form the "raw coordinates" encountered in spectral clustering, and can be extended by means of higher-dimensional embeddings (Schoenberg transformations). Geographical flow data, properly conditioned, illustrate the procedure as well as visualization aspects.Comment: accepted for presentation (and further publication) at the ECML PKDD 2010 conferenc

    Towards coherent optical control of a single hole spin: rabi rotation of a trion conditional on the spin state of the hole

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    A hole spin is a potential solid-state q-bit, that may be more robust against nuclear spin induced dephasing than an electron spin. Here we propose and demonstrate the sequential preparation, control and detection of a single hole spin trapped on a self-assembled InGaAs/GaAs quantum dot. The dot is embedded in a photodiode structure under an applied electric field. Fast, triggered, initialization of a hole spin is achieved by creating a spin-polarized electron-hole pair with a picosecond laser pulse, and in an applied electric field, waiting for the electron to tunnel leaving a spin-polarized hole. Detection of the hole spin with picoseconds time resolution is achieved using a second picosecond laser pulse to probe the positive trion transition, where a trion is created conditional on the hole spin being detected as a change in photocurrent. Finally, using this setup we observe a Rabi rotation of the hole-trion transition that is conditional on the hole spin, which for a pulse area of 2 pi can be used to impart a phase shift of pi between the hole spin states, a non-general manipulation of the hole spin. (C) 2009 Elsevier Ltd. All rights reserved

    Multi-Channel Kondo Necklace

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    A multi--channel generalization of Doniach's Kondo necklace model is formulated, and its phase diagram studied in the mean--field approximation. Our intention is to introduce the possible simplest model which displays some of the features expected from the overscreened Kondo lattice. The NN conduction electron channels are represented by NN sets of pseudospins \vt_{j}, j=1,...,Nj=1, ... , N, which are all antiferromagnetically coupled to a periodic array of |\vs|=1/2 spins. Exploiting permutation symmetry in the channel index jj allows us to write down the self--consistency equation for general NN. For N>2N>2, we find that the critical temperature is rising with increasing Kondo interaction; we interpret this effect by pointing out that the Kondo coupling creates the composite pseudospin objects which undergo an ordering transition. The relevance of our findings to the underlying fermionic multi--channel problem is discussed.Comment: 29 pages (2 figures upon request from [email protected]), LATEX, submitted for publicatio

    Pulsar Timing and its Application for Navigation and Gravitational Wave Detection

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    Pulsars are natural cosmic clocks. On long timescales they rival the precision of terrestrial atomic clocks. Using a technique called pulsar timing, the exact measurement of pulse arrival times allows a number of applications, ranging from testing theories of gravity to detecting gravitational waves. Also an external reference system suitable for autonomous space navigation can be defined by pulsars, using them as natural navigation beacons, not unlike the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board a spacecraft with predicted pulse arrivals at a reference location (e.g. the solar system barycenter), the spacecraft position can be determined autonomously and with high accuracy everywhere in the solar system and beyond. We describe the unique properties of pulsars that suggest that such a navigation system will certainly have its application in future astronautics. We also describe the on-going experiments to use the clock-like nature of pulsars to "construct" a galactic-sized gravitational wave detector for low-frequency (f_GW ~1E-9 - 1E-7 Hz) gravitational waves. We present the current status and provide an outlook for the future.Comment: 30 pages, 9 figures. To appear in Vol 63: High Performance Clocks, Springer Space Science Review

    Metal enrichment processes

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    There are many processes that can transport gas from the galaxies to their environment and enrich the environment in this way with metals. These metal enrichment processes have a large influence on the evolution of both the galaxies and their environment. Various processes can contribute to the gas transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy interactions and others. We review their observational evidence, corresponding simulations, their efficiencies, and their time scales as far as they are known to date. It seems that all processes can contribute to the enrichment. There is not a single process that always dominates the enrichment, because the efficiencies of the processes vary strongly with galaxy and environmental properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 17; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

    Tomato: a crop species amenable to improvement by cellular and molecular methods

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    Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.
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