1,968 research outputs found

    Ultrasonic Stimulation of Mouse Skin Reverses the Healing Delays in Diabetes and Aging by Activation of Rac1

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    Chronic skin-healing defects are one of the leading challenges to lifelong well-being, affecting 2–5% of populations. Chronic wound formation is linked to age and diabetes and frequently leads to major limb amputation. Here we identify a strategy to reverse fibroblast senescence and improve healing rates. In healthy skin, fibronectin activates Rac1 in fibroblasts, causing migration into the wound bed, and driving wound contraction. We discover that mechanical stimulation of the skin with ultrasound can overturn healing defects by activating a calcium/CamKinaseII/Tiam1/Rac1 pathway that substitutes for fibronectin-dependent signaling and promotes fibroblast migration. Treatment of diabetic and aged mice recruits fibroblasts to the wound bed and reduces healing times by 30%, restoring healing rates to those observed in young, healthy animals. Ultrasound treatment is equally effective in rescuing the healing defects of animals lacking fibronectin receptors, and can be blocked by pharmacological inhibition of the CamKinaseII pathway. Finally, we discover that the migration defects of fibroblasts from human venous leg ulcer patients can be reversed by ultrasound, demonstrating that the approach is applicable to human chronic samples. By demonstrating that this alternative Rac1 pathway can substitute for that normally operating in the skin, we identify future opportunities for management of chronic wounds

    A Scintillating Fiber Tracker With SiPM Readout

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    We present a prototype for the first tracking detector consisting of 250 micron thin scintillating fibers and silicon photomultiplier (SiPM) arrays. The detector has a modular design, each module consists of a mechanical support structure of 10mm Rohacell foam between two 100 micron thin carbon fiber skins. Five layers of scintillating fibers are glued to both top and bottom of the support structure. SiPM arrays with a channel pitch of 250 micron are placed in front of the fibers. We show the results of the first module prototype using multiclad fibers of types Bicron BCF-20 and Kuraray SCSF-81M that were read out by novel 32-channel SiPM arrays from FBK-irst/INFN Perugia as well as 32-channel SiPM arrays produced by Hamamatsu. A spatial resolution of 88 micron +/- 6 micron at an average yield of 10 detected photons per minimal ionizig particle has been achieved.Comment: 5 pages, 7 figures, submitted as proceedings to the 11th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD08

    A High-resolution Scintillating Fiber Tracker With Silicon Photomultiplier Array Readout

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    We present prototype modules for a tracking detector consisting of multiple layers of 0.25 mm diameter scintillating fibers that are read out by linear arrays of silicon photomultipliers. The module production process is described and measurements of the key properties for both the fibers and the readout devices are shown. Five modules have been subjected to a 12 GeV/c proton/pion testbeam at CERN. A spatial resolution of 0.05 mm and light yields exceeding 20 detected photons per minimum ionizing particle have been achieved, at a tracking efficiency of more than 98.5%. Possible techniques for further improvement of the spatial resolution are discussed.Comment: 31 pages, 27 figures, pre-print version of an article published in Nuclear Instruments and Methods in Physics Research Section A, Vol. 62

    A New Measurement of the 1S0 Neutron-Neutron Scattering Length using the Neutron-Proton Scattering Length as a Standard

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    The present paper reports high-accuracy cross-section data for the 2H(n,nnp) reaction in the neutron-proton (np) and neutron-neutron (nn) final-state-interaction (FSI) regions at an incident mean neutron energy of 13.0 MeV. These data were analyzed with rigorous three-nucleon calculations to determine the 1S0 np and nn scattering lengths, a_np and a_nn. Our results are a_nn = -18.7 +/- 0.6 fm and a_np = -23.5 +/- 0.8 fm. Since our value for a_np obtained from neutron-deuteron (nd) breakup agrees with that from free np scattering, we conclude that our investigation of the nn FSI done simultaneously and under identical conditions gives the correct value for a_nn. Our value for a_nn is in agreement with that obtained in pion-deuteron capture measurements but disagrees with values obtained from earlier nd breakup studies.Comment: 4 pages and 3 figure

    Intrauterine growth restriction increases fetal hepatic gluconeogenic capacity and reduces messenger ribonucleic acid translation initiation and nutrient sensing in fetal liver and skeletal muscle.

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    Expression of key metabolic genes and proteins involved in mRNA translation, energy sensing, and glucose metabolism in liver and skeletal muscle were investigated in a late-gestation fetal sheep model of placental insufficiency intrauterine growth restriction (PI-IUGR). PI-IUGR fetuses weighed 55% less; had reduced oxygen, glucose, isoleucine, insulin, and IGF-I levels; and had 40% reduction in net branched chain amino acid uptake. In PI-IUGR skeletal muscle, levels of insulin receptor were increased 80%, whereas phosphoinositide-3 kinase (p85) and protein kinase B (AKT2) were reduced by 40%. Expression of eukaryotic initiation factor-4e was reduced 45% in liver, suggesting a unique mechanism limiting translation initiation in PI-IUGR liver. There was either no change (AMP activated kinase, mammalian target of rapamycin) or a paradoxical decrease (protein phosphatase 2A, eukaryotic initiation factor-2 alpha) in activation of major energy and cell stress sensors in PI-IUGR liver and skeletal muscle. A 13- to 20-fold increase in phosphoenolpyruvate carboxykinase and glucose 6 phosphatase mRNA expression in the PI-IUGR liver was-associated with a 3-fold increase in peroxisome proliferator-activated receptor-gamma coactivator-1 alpha mRNA and increased phosphorylation of cAMP response element binding protein. Thus PI-IUGR is-associated with reduced branched chain amino acid uptake and growth factors, yet up-regulation of proximal insulin signaling and a marked increase in the gluconeogenic pathway. Lack of activation of several energy and stress sensors in fetal liver and skeletal muscle, despite hypoxia and low energy status, suggests a novel strategy for survival in the PI-IUGR fetus but with potential maladaptive consequences for reduced nutrient sensing and insulin sensitivity in postnatal life
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