365 research outputs found

    Principles and Practices of Neurodevelopmental Assessment in Children: Lessons Learned from the Centers for Children’s Environmental Health and Disease Prevention Research

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    Principles and practices of pediatric neurotoxicology are reviewed here with the purpose of guiding the design and execution of the planned National Children’s Study. The developing human central nervous system is the target organ most vulnerable to environmental chemicals. An investigation of the effects of environmental exposures on child development is a complex endeavor that requires consideration of numerous critical factors pertinent to a study’s concept, design, and execution. These include the timing of neurodevelopmental assessment, matters of biologic plausibility, site, child and population factors, data quality assurance and control, the selection of appropriate domains and measures of neurobehavior, and data safety and monitoring. Here we summarize instruments for the assessment of the neonate, infant, and child that are being employed in the Centers for Children’s Environmental Health and Disease Prevention Research, sponsored by the National Institute of Environmental Health Sciences and the U.S. Environmental Protection Agency, discuss neural and neurobiologic measures of development, and consider the promises of gene–environment studies. The vulnerability of the human central nervous system to environmental chemicals has been well established, but the contribution these exposures may make to problems such as attention deficit disorder, conduct problems, pervasive developmental disorder, or autism spectrum disorder remain uncertain. Large-scale studies such as the National Children’s Study may provide some important clues. The human neurodevelopmental phenotype will be most clearly represented in models that include environmental chemical exposures, the social milieu, and complex human genetic characteristics that we are just beginning to understand

    Effect of β-alanine supplementation on 20 km cycling time trial performance

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    The effects of β-alanine supplementation on high-intensity cycling performance and capacity have been evaluated, although the effects on longer duration cycling performance are unclear. Nineteen UK category 1 male cyclists completed four 20 km cycling time trials, two before and two after supplementation with either 6.4 g•d -1 β-alanine (n = 10; BA) or a matched placebo (n = 9; P). Performance time for the 20 km time trial and 1 km split times were recorded. There was no significant effect of β-alanine supplementation on 20 km time trial performance (BA-pre 1943 ± 129 s; BA-post 1950 ± 147 s; P-pre 1989 ± 106 s; P-post 1986 ± 115 s) or on the performance of each 1 km split. The effect of β-alanine on 20 km time trial performance was deemed unclear as determined by magnitude based inferences. Supplementation with 6.4 g•d -1 of β-alanine for 4 weeks did not affect 20 km cycling time trial performance in well trained male cyclists

    Determining the neurotransmitter concentration profile at active synapses

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    Establishing the temporal and concentration profiles of neurotransmitters during synaptic release is an essential step towards understanding the basic properties of inter-neuronal communication in the central nervous system. A variety of ingenious attempts has been made to gain insights into this process, but the general inaccessibility of central synapses, intrinsic limitations of the techniques used, and natural variety of different synaptic environments have hindered a comprehensive description of this fundamental phenomenon. Here, we describe a number of experimental and theoretical findings that has been instrumental for advancing our knowledge of various features of neurotransmitter release, as well as newly developed tools that could overcome some limits of traditional pharmacological approaches and bring new impetus to the description of the complex mechanisms of synaptic transmission

    Regional cortical volumes and congenital heart disease: a MRI study in 22q11.2 deletion syndrome

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    Children with congenital heart disease (CHD) who survive surgery often present impaired neurodevelopment and qualitative brain anomalies. However, the impact of CHD on total or regional brain volumes only received little attention. We address this question in a sample of patients with 22q11.2 deletion syndrome (22q11DS), a neurogenetic condition frequently associated with CHD. Sixty-one children, adolescents, and young adults with confirmed 22q11.2 deletion were included, as well as 80 healthy participants matched for age and gender. Subsequent subdivision of the patients group according to CHD yielded a subgroup of 27 patients with normal cardiac status and a subgroup of 26 patients who underwent cardiac surgery during their first years of life (eight patients with unclear status were excluded). Regional cortical volumes were extracted using an automated method and the association between regional cortical volumes, and CHD was examined within a three-condition fixed factor. Robust protection against type I error used Bonferroni correction. Smaller total cerebral volumes were observed in patients with CHD compared to both patients without CHD and controls. The pattern of bilateral regional reductions associated with CHD encompassed the superior parietal region, the precuneus, the fusiform gyrus, and the anterior cingulate cortex. Within patients, a significant reduction in the left parahippocampal, the right middle temporal, and the left superior frontal gyri was associated with CHD. The present results of global and regional volumetric reductions suggest a role for disturbed hemodynamic in the pathophysiology of brain alterations in patients with neurodevelopmental disease and cardiac malformations

    Influence of training status on high-intensity intermittent performance in response to β-alanine supplementation

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    Recent investigations have suggested that highly trained athletes may be less responsive to the ergogenic effects of β-alanine (BA) supplementation than recreationally active individuals due to their elevated muscle buffering capacity. We investigated whether training status influences the effect of BA on repeated Wingate performance. Forty young males were divided into two groups according to their training status (trained: T, and non-trained: NT cyclists) and were randomly allocated to BA and a dextrose-based placebo (PL) groups, providing four experimental conditions: NTPL, NTBA, TPL, TBA. BA (6.4 g day-1 ) or PL was ingested for 4 weeks, with participants completing four 30-s lower-body Wingate bouts, separated by 3 min, before and after supplementation. Total work done was significantly increased following supplementation in both NTBA (p = 0.03) and TBA (p = 0.002), and it was significantly reduced in NTPL (p = 0.03) with no difference for TPL (p = 0.73). BA supplementation increased mean power output (MPO) in bout 4 for the NTBA group (p = 0.0004) and in bouts 1, 2 and 4 for the TBA group (p ≤ 0.05). No differences were observed in MPO for NTPL and TPL. BA supplementation was effective at improving repeated high-intensity cycling performance in both trained and non-trained individuals, highlighting the efficacy of BA as an ergogenic aid for high-intensity exercise regardless of the training status of the individual

    Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron

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    We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles (transverse momentum pT > 0.5 GeV/c, pseudorapidity |\eta| < 1) produced in association with large transverse momentum jets (~2.2 fb-1) or with Drell-Yan lepton-pairs (~2.7 fb-1) in the Z-boson mass region (70 < M(pair) < 110 GeV/c2) as measured by CDF at 1.96 TeV center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan production) or the leading jet (in high-pT jet production) in each event to define three regions of \eta-\phi space; toward, away, and transverse, where \phi is the azimuthal scattering angle. For Drell-Yan production (excluding the leptons) both the toward and transverse regions are very sensitive to the underlying event. In high-pT jet production the transverse region is very sensitive to the underlying event and is separated into a MAX and MIN transverse region, which helps separate the hard component (initial and final-state radiation) from the beam-beam remnant and multiple parton interaction components of the scattering. The data are corrected to the particle level to remove detector effects and are then compared with several QCD Monte-Carlo models. The goal of this analysis is to provide data that can be used to test and improve the QCD Monte-Carlo models of the underlying event that are used to simulate hadron-hadron collisions.Comment: Submitted to Phys.Rev.

    Precision measurement of the top quark mass from dilepton events at CDF II

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    We report a measurement of the top quark mass, M_t, in the dilepton decay channel of ttˉb+νbˉνˉt\bar{t}\to b\ell'^{+}\nu_{\ell'}\bar{b}\ell^{-}\bar{\nu}_{\ell} using an integrated luminosity of 1.0 fb^{-1} of p\bar{p} collisions collected with the CDF II detector. We apply a method that convolutes a leading-order matrix element with detector resolution functions to form event-by-event likelihoods; we have enhanced the leading-order description to describe the effects of initial-state radiation. The joint likelihood is the product of the likelihoods from 78 candidate events in this sample, which yields a measurement of M_{t} = 164.5 \pm 3.9(\textrm{stat.}) \pm 3.9(\textrm{syst.}) \mathrm{GeV}/c^2, the most precise measurement of M_t in the dilepton channel.Comment: 7 pages, 2 figures, version includes changes made prior to publication by journa

    Measurement of the Ratios of Branching Fractions B(Bs -> Ds pi pi pi) / B(Bd -> Dd pi pi pi) and B(Bs -> Ds pi) / B(Bd -> Dd pi)

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    Using 355 pb^-1 of data collected by the CDF II detector in \ppbar collisions at sqrt{s} = 1.96 TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B -> D pi and B -> D pi pi pi. We present the first measurement of the ratio of branching fractions B(Bs -> Ds pi pi pi) / B(Bd -> Dd pi pi pi) = 1.05 pm 0.10 (stat) pm 0.22 (syst). We also update our measurement of B(Bs -> Ds pi) / B(Bd -> Dd pi) to 1.13 pm 0.08 (stat) pm 0.23 (syst) improving the statistical uncertainty by more than a factor of two. We find B(Bs -> Ds pi) = [3.8 pm 0.3 (stat) pm 1.3 (syst)] \times 10^{-3} and B(Bs -> Ds pi pi pi) = [8.4 pm 0.8 (stat) pm 3.2 (syst)] \times 10^{-3}.Comment: 7 pages, 2 figure

    Cross Section Measurements of High-pTp_T Dilepton Final-State Processes Using a Global Fitting Method

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    We present a new method for studying high-pTp_T dilepton events (e±ee^{\pm}e^{\mp}, μ±μ\mu^{\pm}\mu^{\mp}, e±μe^{\pm}\mu^{\mp}) and simultaneously extracting the production cross sections of ppˉttˉp\bar{p} \to t\bar{t}, ppˉW+Wp\bar{p} \to W^+W^-, and p\bar{p} \to \ztt at a center-of-mass energy of s=1.96\sqrt{s} = 1.96 TeV. We perform a likelihood fit to the dilepton data in a parameter space defined by the missing transverse energy and the number of jets in the event. Our results, which use 360pb1360 {\rm pb^{-1}} of data recorded with the CDF II detector at the Fermilab Tevatron Collider, are σ(ttˉ)=8.52.2+2.7\sigma(t\bar{t}) = 8.5_{-2.2}^{+2.7} pb, σ(W+W)=16.34.4+5.2\sigma(W^+W^-) = 16.3^{+5.2}_{-4.4} pb, and \sigma(\ztt) =291^{+50}_{-46} pb.Comment: 20 pages, 2 figures, to be submitted to PRD-R
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