1,165 research outputs found
Pathological Changes in Microvascular Morphology, Density, Size and Responses Following Comorbid Cerebral Injury
Aberrations in brain microcirculation and the associated increase in blood-brain-barrier (BBB) permeability in addition to neuroinflammation and Aβ deposition observed in Alzheimer’s disease (AD) and ischemia have gained considerable attention recently. However, the role of microvascular homeostasis as a pathogenic substrate to disturbed microperfusion as well as an overlapping etiologic mechanism between AD and ischemia has not been thoroughly explored. In this study, we employ temporal histopathology of cerebral vasculature in a rat model of β-amyloid (Aβ) toxicity and endothelin-1 induced-ischemia (ET1) to investigate the panorama of cerebral pathology and the protein expression on d1, d7, and d28 post-injury. The combination of Aβ and ET1 pathological states leads to an alteration in microvascular anatomy, texture, diameter, density, and protein expression, in addition to disturbed vessel-matrix-connections, inter-compartmental water exchange and basement membrane profile within the lesion epicenter localized in the striatum of Aβ+ET1 brains compared to Aβ and ET1 rats. We conclude that the neural microvascular network, in addition to the neural tissue, is not only sensitive to structural deterioration but also serves as an underlying vascular etiology between ischemia and AD pathologies. Such investigation can provide prospects to appreciate the interrelationships between structure and responses of cerebral microvasculature and to provide a venue for vascular remodeling as a new treatment strategy
Wilcoxon Rank-Based Tests for Clustered Data with R Package clusrank
Wilcoxon rank-based tests are distribution-free alternatives to the popular two-sample and paired t tests. For independent data, they are available in several R packages such as stats and coin. For clustered data, in spite of the recent methodological developments, there did not exist an R package that makes them available at one place. We present a package clusrank where the latest developments are implemented and wrapped under a unified user-friendly interface. With different methods dispatched based on the inputs, this package offers great flexibility in rank-based tests for various clustered data. Exact tests based on permutations are also provided for some methods. Details of the major schools of different methods are briefly reviewed. Usages of the package clusrank are illustrated with simulated data as well as a real dataset from an ophthalmological study. The package also enables convenient comparison between selected methods under settings that have not been studied before and the results are discussed
EFFECTS OF EIGHT-WEEK WHOLE-BODY VIBRATION TRAINING ON POSTURAL STABILITY IN ELDERLY ADULTS
The aim of this study was to examine the effects of an eight-week whole-body vibration training (WBVT) on postural stability (PS) in elderly people. Twenty-two elderly people with normal ability of movement were randomized into the WBVT group (WBVTG, 13 elders), and the control group (CG, 9 elders). The WBVTG underwent WBV training for 8 weeks. The CG did not take any physical training. The PS performance was evaluated by the Biodex Balance System to measure the overall (O), anterior-posterior (AP), and medial-lateral (ML) stability at level 2 (unstable) and level 8 (stable). One-way ANCOVA were used for statistical analysis, with =0.05. Results showed that after training, the WBVG significantly improved the O, AP, and ML stability performance at level 2, and also the O and ML stability performance at level 8
Temporal changes in blood-brain barrier permeability and cerebral perfusion in lacunar/subcortical ischemic stroke
BACKGROUND: Cerebral microvascular abnormality is frequently associated with lacunar and subcortical ischemic lesions. We performed acute and follow-up CT perfusion scans over the first 3 months after ischemic stroke to investigate disturbances of the blood–brain barrier (BBB) and cerebral perfusion in patients with lacunar/subcortical lesions compared to those with cortical lesions alone. METHODS: Thirty-one patients with lacunar/subcortical infarct (n = 14) or with cortical large vessel infarct (n = 17) were recruited and underwent a CT perfusion study at admission, 24 h, 7 days and 3 months after stroke using a two-phase imaging protocol. Functional maps of BBB permeability surface area product (BBB-PS), cerebral blood flow (CBF) and blood volume (CBV) at follow-up were co-registered with those at admission, and the measurements in non-infarcted ipsilateral basal ganglia and thalamus were compared within each group and between the two groups. RESULTS: For the lacunar/subcortical group, BBB-PS within non-infarcted ipsilateral basal ganglia and thalamus peaked at day 7 compared to all other time points, and was significantly higher than the cortical group at day 7 and month 3. The CBF and CBV in the same region were significantly lower at admission and transient hyperemia was seen at day 7 in the lacunar/subcortical group. CONCLUSION: Disturbed BBB-PS and compromised cerebral perfusion over the first 3 months post stroke were shown in the non-infarcted basal ganglia and thalamus of lacunar/subcortical stroke using CT perfusion. Future studies are required to elucidate the relationship of post-stroke BBB disturbances to chronic cognitive impairment
Polarization of Quasars: Resonant Line Scattering in the Broad Absorption Line Region
Recent works showed that the absorbing material in broad absorption line
(BAL) quasars is optically thick to major resonant absorption lines. This
material may contribute significantly to the polarization in the absorption
lines. In this paper, we present a detailed study of the resonant line
scattering process using Monte-Carlo method to constrain the optical depth, the
geometry and the kinematics of BAL Region (BALR). By comparing our results with
observed polarized spectra of BAL quasars, we find: (1) Resonant scattering can
produce polarization up to 9% at the absorption trough for doublet transitions
and up to 20% for singlet transitions in radially accelerated flows. To explain
the large polarization degree in the CIV, NV absorption line troughs detected
in a small fraction of BAL QSOs, a nonmonotonic velocity distribution along the
line of sight or/and additional contribution from the electron scattering
region is required. (2) The rotation of the flow can lead to the rotation of
the polarization position angle (PA) in the line trough. Large extending angle
of BALR is required to produce the observed large PA rotation in a few BAL
QSOs. (3) A large extending angle of BALR is required to explain a sub-trough
in the polarized flux that was observed in a number of BAL QSOs. (4) The
resonant-scattering can contribute a significant part of NV emission line in
some QSOs, and may give rise to anomalous strong NV lines in these quasars. (5)
The polarized flux and PA rotation produced by the resonant scattering in
non-BAL is uniquely asymmetric, which may be used to test the presence of BALR
in non-BAL QSOs.Comment: 54 pages, 26 figures, accepted by ApJS, contact author by email for
version with higher resolution figure
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