998 research outputs found
Retrograde semaphorin-plexin signalling drives homeostatic synaptic plasticity.
Homeostatic signalling systems ensure stable but flexible neural activity and animal behaviour. Presynaptic homeostatic plasticity is a conserved form of neuronal homeostatic signalling that is observed in organisms ranging from Drosophila to human. Defining the underlying molecular mechanisms of neuronal homeostatic signalling will be essential in order to establish clear connections to the causes and progression of neurological disease. During neural development, semaphorin-plexin signalling instructs axon guidance and neuronal morphogenesis. However, semaphorins and plexins are also expressed in the adult brain. Here we show that semaphorin 2b (Sema2b) is a target-derived signal that acts upon presynaptic plexin B (PlexB) receptors to mediate the retrograde, homeostatic control of presynaptic neurotransmitter release at the neuromuscular junction in Drosophila. Further, we show that Sema2b-PlexB signalling regulates presynaptic homeostatic plasticity through the cytoplasmic protein Mical and the oxoreductase-dependent control of presynaptic actin. We propose that semaphorin-plexin signalling is an essential platform for the stabilization of synaptic transmission throughout the developing and mature nervous system. These findings may be relevant to the aetiology and treatment of diverse neurological and psychiatric diseases that are characterized by altered or inappropriate neural function and behaviour
Possible roles of Epstein-Barr virus in Castleman disease
<p>Abstract</p> <p>Background</p> <p>Complete resection seemed to be curative in patients with Castleman disease of any location but the disease is likely to be reactive in its pathogenesis. The relation between Epstein-Barr virus and Castleman disease has not been elucidated. We tried to define the role of Epstein-Barr virus in the pathogenesis of Castleman disease.</p> <p>Methods</p> <p>20 cases of Castleman disease were retrospectively reviewed from 1993 to 2006. At least 2 to 4 representative sections of formalin-fixed, paraffin-embedded specimens from each patient were obtained to examine the presence of EBV and its localization by hematoxylin-eosin stain, immunohistochemistry, polymerase chain reaction and In-situ hybridization</p> <p>Results</p> <p>Hyaline-vascular type was diagnosed in 18 cases, plasma cell type in 1 and mixed type in 1 case. All of them were positive for Epstein-Barr virus confirmed by PCR. For tumors that EBER(Epstein-Barr early region) signals mainly localized in the germinal centers have increased vascularity than cases with EBER detected in inter-follicular areas.</p> <p>Conclusion</p> <p>There is a strong association between Castleman disease and Epstein-Barr virus. EBV may have a potential role in angiogenesis of Castleman disease. For smaller lesion with high activity of angiogenesis but not amenable for curative resection, anti-angiogenesis medications may have a potential role to control the disease.</p
Higgs and Dark Matter Hints of an Oasis in the Desert
Recent LHC results suggest a standard model (SM)-like Higgs boson in the
vicinity of 125 GeV with no clear indications yet of physics beyond the SM. At
the same time, the SM is incomplete, since additional dynamics are required to
accommodate cosmological dark matter (DM). In this paper we show that
interactions between weak scale DM and the Higgs which are strong enough to
yield a thermal relic abundance consistent with observation can easily
destabilize the electroweak vacuum or drive the theory into a non-perturbative
regime at a low scale. As a consequence, new physics--beyond the DM
itself--must enter at a cutoff well below the Planck scale and in some cases as
low as O(10 - 1000 TeV), a range relevant to indirect probes of flavor and CP
violation. In addition, this cutoff is correlated with the DM mass and
scattering cross-section in a parameter space which will be probed
experimentally in the near term. Specifically, we consider the SM plus
additional spin 0 or 1/2 states with singlet, triplet, or doublet electroweak
quantum numbers and quartic or Yukawa couplings to the Higgs boson. We derive
explicit expressions for the full two-loop RGEs and one-loop threshold
corrections for these theories.Comment: 29 pages, 13 figure
Obesity as Assessed by Body Adiposity Index and Multivariable Cardiovascular Disease Risk
To assess the role of body adiposity index (BAI) in predicting cardiovascular disease (CVD) and coronary heart disease (CHD) mortality, in comparison with body mass index (BMI), waist circumference (WC), and the waist circumference to hip circumference ratio (WHR). This study was a prospective 15 year mortality follow-up of 4175 Australian males, free of heart disease, diabetes and stroke. The Framingham Risk Scores (FRS) for CHD and CVD death were calculated at baseline for all subjects. Multivariable logistic regression was used to assess the effects of the measures of obesity on CVD and CHD mortality, before adjustment and after adjustment for FRS. The predictive ability of BAI, though present in the unadjusted analyses, was generally not significant after adjustment for age and FRS for both CVD and CHD mortality. BMI behaved similarly to BAI in that its predictive ability was generally not significant after adjustments. Both WC and WHR were significant predictors of CVD and CHD mortality and remained significant after adjustment for covariates. BAI appeared to be of potential interest as a measure of % body fat and of obesity, but was ineffective in predicting CVD and CHD
Positivity, entanglement entropy, and minimal surfaces
The path integral representation for the Renyi entanglement entropies of
integer index n implies these information measures define operator correlation
functions in QFT. We analyze whether the limit , corresponding
to the entanglement entropy, can also be represented in terms of a path
integral with insertions on the region's boundary, at first order in .
This conjecture has been used in the literature in several occasions, and
specially in an attempt to prove the Ryu-Takayanagi holographic entanglement
entropy formula. We show it leads to conditional positivity of the entropy
correlation matrices, which is equivalent to an infinite series of polynomial
inequalities for the entropies in QFT or the areas of minimal surfaces
representing the entanglement entropy in the AdS-CFT context. We check these
inequalities in several examples. No counterexample is found in the few known
exact results for the entanglement entropy in QFT. The inequalities are also
remarkable satisfied for several classes of minimal surfaces but we find
counterexamples corresponding to more complicated geometries. We develop some
analytic tools to test the inequalities, and as a byproduct, we show that
positivity for the correlation functions is a local property when supplemented
with analyticity. We also review general aspects of positivity for large N
theories and Wilson loops in AdS-CFT.Comment: 36 pages, 10 figures. Changes in presentation and discussion of
Wilson loops. Conclusions regarding entanglement entropy unchange
Corner contributions to holographic entanglement entropy
The entanglement entropy of three-dimensional conformal field theories
contains a universal contribution coming from corners in the entangling
surface. We study these contributions in a holographic framework and, in
particular, we consider the effects of higher curvature interactions in the
bulk gravity theory. We find that for all of our holographic models, the corner
contribution is only modified by an overall factor but the functional
dependence on the opening angle is not modified by the new gravitational
interactions. We also compare the dependence of the corner term on the new
gravitational couplings to that for a number of other physical quantities, and
we show that the ratio of the corner contribution over the central charge
appearing in the two-point function of the stress tensor is a universal
function for all of the holographic theories studied here. Comparing this
holographic result to the analogous functions for free CFT's, we find fairly
good agreement across the full range of the opening angle. However, there is a
precise match in the limit where the entangling surface becomes smooth, i.e.,
the angle approaches , and we conjecture the corresponding ratio is a
universal constant for all three-dimensional conformal field theories. In this
paper, we expand on the holographic calculations in our previous letter
arXiv:1505.04804, where this conjecture was first introduced.Comment: 62 pages, 6 figures, 1 table; v2: minor modifications to match
published version, typos fixe
Genetic Polymorphisms of CYP2E1, GSTP1, NQO1 and MPO and the Risk of Nasopharyngeal Carcinoma in a Han Chinese Population of Southern China
<p>Abstract</p> <p>Background</p> <p>Southern China is a major area for endemic nasopharyngeal carcinoma (NPC). Genetic factors as well as environmental factors play a role in development of NPC. To investigate the roles of previously described carcinogen metabolism gene variants for NPC susceptibility in a Han Chinese population, we conducted a case-control study in two independent study population groups afflicted with NPC in Guangdong and Guangxi Provinces of southern China.</p> <p>Methods</p> <p>Five single nucleotide polymorphisms (SNPs) of <it>CYP2E1</it>-rs2031920, <it>CYP2E1</it>-rs6413432, <it>GSTP1</it>-rs947894, <it>MPO</it>-rs2333227 and <it>NQO1</it>-rs1800566 were genotyped by PCR-based RFLP, sequencing and TaqMan assay in 358 NPC cases and 629 controls (phase I cohort). Logistic regression analysis was used to estimate odds ratios (OR) and 95% confidence intervals (CI). To confirm our results, sixteen tag SNPs for <it>GSTP1</it>, <it>MPO</it>, <it>NQO1 </it>(which 100% covered these genes), and 4 functional SNPs of <it>CYP2E1 </it>were genotyped in another cohort of 213 NPC cases and 230 controls (phase II cohort).</p> <p>Results</p> <p>No significant associations in NPC risk were observed for the five polymorphisms tested in the phase I cohort. In an additional stratified analysis for phase I, there was no significant association between cases and controls in NPC high risk population (EBV/IgA/VCA positive population). Analysis of 14 tagging SNPs within the same genes in an independent phase II cohort were in agreement with no SNPs significantly associated with NPC.</p> <p>Conclusions</p> <p>Our results suggest that polymorphism of <it>CYP2E1</it>, <it>GSTP1</it>, <it>MPO </it>and <it>NQO1 </it>genes does not contribute to overall NPC risk in a Han Chinese in southern China.</p
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