676 research outputs found
Chandra Observations of the Faintest Low-Mass X-ray Binaries
There exists a group of persistently faint galactic X-ray sources that, based
on their location in the galaxy, high L_x/L_opt, association with X-ray bursts,
and absence of low frequency X-ray pulsations, are thought to be low-mass X-ray
binaries (LMXBs). We present results from Chandra observations for eight of
these systems: 4U 1708-408, 2S 1711-339, KS 1739-304, SLX 1735-269, GRS
1736-297, SLX 1746-331, 1E 1746.7-3224, and 4U 1812-12. Locations for all
sources, excluding GRS 1736-297, SLX 1746-331, and KS 1739-304 (which were not
detected) were improved to 0.6" error circles (90% confidence). Our
observations support earlier findings of transient behavior of GRS 1736-297, KS
1739-304, SLX 1746-331, and 2S 1711-339 (which we detect in one of two
observations). Energy spectra for 4U 1708-408, 2S 1711-339, SLX 1735-269, 1E
1746.7-3224, and 4U 1812-12 are hard, with power law indices typically 1.4-2.1,
which are consistent with typical faint LMXB spectra.Comment: 15 pages, 3 figures. Accepted by Ap
The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
The all sky surveys done by the Palomar Observatory Schmidt, the European
Southern Observatory Schmidt, and the United Kingdom Schmidt, the InfraRed
Astronomical Satellite and the 2 Micron All Sky Survey have proven to be
extremely useful tools for astronomy with value that lasts for decades. The
Wide-field Infrared Survey Explorer is mapping the whole sky following its
launch on 14 December 2009. WISE began surveying the sky on 14 Jan 2010 and
completed its first full coverage of the sky on July 17. The survey will
continue to cover the sky a second time until the cryogen is exhausted
(anticipated in November 2010). WISE is achieving 5 sigma point source
sensitivities better than 0.08, 0.11, 1 and 6 mJy in unconfused regions on the
ecliptic in bands centered at wavelengths of 3.4, 4.6, 12 and 22 microns.
Sensitivity improves toward the ecliptic poles due to denser coverage and lower
zodiacal background. The angular resolution is 6.1, 6.4, 6.5 and 12.0
arc-seconds at 3.4, 4.6, 12 and 22 microns, and the astrometric precision for
high SNR sources is better than 0.15 arc-seconds.Comment: 22 pages with 19 included figures. Updated to better match the
accepted version in the A
Post-stroke inhibition of induced NADPH oxidase type 4 prevents oxidative stress and neurodegeneration
Ischemic stroke is the second leading cause of death worldwide. Only one moderately effective therapy exists, albeit with contraindications that exclude 90% of the patients. This medical need contrasts with a high failure rate of more than 1,000 pre-clinical drug candidates for stroke therapies. Thus, there is a need for translatable mechanisms of neuroprotection and more rigid thresholds of relevance in pre-clinical stroke models. One such candidate mechanism is oxidative stress. However, antioxidant approaches have failed in clinical trials, and the significant sources of oxidative stress in stroke are unknown. We here identify NADPH oxidase type 4 (NOX4) as a major source of oxidative stress and an effective therapeutic target in acute stroke. Upon ischemia, NOX4 was induced in human and mouse brain. Mice deficient in NOX4 (Nox4(-/-)) of either sex, but not those deficient for NOX1 or NOX2, were largely protected from oxidative stress, blood-brain-barrier leakage, and neuronal apoptosis, after both transient and permanent cerebral ischemia. This effect was independent of age, as elderly mice were equally protected. Restoration of oxidative stress reversed the stroke-protective phenotype in Nox4(-/-) mice. Application of the only validated low-molecular-weight pharmacological NADPH oxidase inhibitor, VAS2870, several hours after ischemia was as protective as deleting NOX4. The extent of neuroprotection was exceptional, resulting in significantly improved long-term neurological functions and reduced mortality. NOX4 therefore represents a major source of oxidative stress and novel class of drug target for stroke therapy
Gene Expression Analysis of In Vivo Fluorescent Cells
BACKGROUND: The analysis of gene expression for tissue homogenates is of limited value because of the considerable cell heterogeneity in tissues. However, several methods are available to isolate a cell type of interest from a complex tissue, the most reliable one being Laser Microdissection (LMD). Cells may be distinguished by their morphology or by specific antigens, but the obligatory staining often results in RNA degradation. Alternatively, particular cell types can be detected in vivo by expression of fluorescent proteins from cell type-specific promoters. METHODOLOGY/PRINCIPAL FINDINGS: We developed a technique for fixing in vivo fluorescence in brain cells and isolating them by LMD followed by an optimized RNA isolation procedure. RNA isolated from these cells was of equal quality as from unfixed frozen tissue, with clear 28S and 18S rRNA bands of a mass ratio of approximately 2ratio1. We confirmed the specificity of the amplified RNA from the microdissected fluorescent cells as well as its usefulness and reproducibility for microarray hybridization and quantitative real-time PCR (qRT-PCR). CONCLUSIONS/SIGNIFICANCE: Our technique guarantees the isolation of sufficient high quality RNA obtained from specific cell populations of the brain expressing soluble fluorescent marker, which is a critical prerequisite for subsequent gene expression studies by microarray analysis or qRT-PCR
Acidic preconditioning protects endothelial cells against apoptosis through p38- and Akt-dependent Bcl-xL overexpression
To analyze the underlying cellular mechanisms of adaptation to ischemia-induced apoptosis through short acidic pretreatment, i.e. acidic preconditioning (APC), Wistar rat coronary endothelial cells (EC) were exposed for 40 min to acidosis (pH 6.4) followed by a 14 h recovery period (pH 7.4) and finally treated for 2 h with simulated in vitro ischemia (glucose-free anoxia at pH 6.4). APC led to a transient activation of p38 and Akt kinases, but not of JNK and ERK1/2 kinases, which was accompanied by significant reduction of the apoptotic cell number, caspase-12/-3 cleavage and Bcl-xL overexpression. These effects of APC were completely abolished by prevention of Akt- or p38-phosphorylation during APC. Furthermore, knock-down of Bcl-xL by siRNA-transfection also abolished the anti-apoptotic effect of APC. Therefore, APC leads to protection of EC against ischemic apoptosis by activation of Akt and p38 followed by overexpression of Bcl-xL, which is a key anti-apoptotic mechanism of APC
Transverse-Momentum Dependence of the J/psi Nuclear Modification in d+Au Collisions at sqrt(s_NN)=200 GeV
We present measured J/psi production rates in d+Au collisions at sqrt(s_NN) =
200 GeV over a broad range of transverse momentum (p_T=0-14 GeV/c) and rapidity
(-2.2<y<2.2). We construct the nuclear-modification factor R_dAu for these
kinematics and as a function of collision centrality (related to impact
parameter for the R_dAu collision). We find that the modification is largest
for collisions with small impact parameters, and observe a suppression
(R_dAu<1) for p_T<4 GeV/c at positive rapidities. At negative rapidity we
observe a suppression for p_T1) for p_T>2
GeV/c. The observed enhancement at negative rapidity has implications for the
observed modification in heavy-ion collisions at high p_T.Comment: 384 authors, 24 pages, 19 figures, 13 tables. Submitted to Phys. Rev.
C. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/info/data/ppg123_data.htm
No Evidence of a Common DNA Variant Profile Specific to World Class Endurance Athletes
There are strong genetic components to cardiorespiratory fitness and its
response to exercise training. It would be useful to understand the
differences in the genomic profile of highly trained endurance athletes of
world class caliber and sedentary controls. An international consortium
(GAMES) was established in order to compare elite endurance athletes and
ethnicity-matched controls in a case-control study design. Genome-wide
association studies were undertaken on two cohorts of elite endurance athletes
and controls (GENATHLETE and Japanese endurance runners), from which a panel
of 45 promising markers was identified. These markers were tested for
replication in seven additional cohorts of endurance athletes and controls:
from Australia, Ethiopia, Japan, Kenya, Poland, Russia and Spain. The study is
based on a total of 1520 endurance athletes (835 who took part in endurance
events in World Championships and/or Olympic Games) and 2760 controls. We
hypothesized that world-class athletes are likely to be characterized by an
even higher concentration of endurance performance alleles and we performed
separate analyses on this subsample. The meta-analysis of all available
studies revealed one statistically significant marker (rs558129 at GALNTL6
locus, p = 0.0002), even after correcting for multiple testing. As shown by
the low heterogeneity index (I2 = 0), all eight cohorts showed the same
direction of association with rs558129, even though p-values varied across the
individual studies. In summary, this study did not identify a panel of genomic
variants common to these elite endurance athlete groups. Since GAMES was
underpowered to identify alleles with small effect sizes, some of the
suggestive leads identified should be explored in expanded comparisons of
world-class endurance athletes and sedentary controls and in tightly
controlled exercise training studies. Such studies have the potential to
illuminate the biology not only of world class endurance performance but also
of compromised cardiac functions and cardiometabolic diseases
Deficiency of Vasodilator-Stimulated Phosphoprotein (VASP) Increases Blood-Brain-Barrier Damage and Edema Formation after Ischemic Stroke in Mice
Background: Stroke-induced brain edema formation is a frequent cause of secondary infarct growth and deterioration of neurological function. The molecular mechanisms underlying edema formation after stroke are largely unknown. Vasodilator-stimulated phosphoprotein (VASP) is an important regulator of actin dynamics and stabilizes endothelial barriers through interaction with cell-cell contacts and focal adhesion sites. Hypoxia has been shown to foster vascular leakage by downregulation of VASP in vitro but the significance of VASP for regulating vascular permeability in the hypoxic brain in vivo awaits clarification. Methodology/Principal Findings: Focal cerebral ischemia was induced in Vasp2/2 mice and wild-type (WT) littermates by transient middle cerebral artery occlusion (tMCAO). Evan’s Blue tracer was applied to visualize the extent of blood-brainbarrier (BBB) damage. Brain edema formation and infarct volumes were calculated from 2,3,5-triphenyltetrazolium chloride (TTC)-stained brain slices. Both mouse groups were carefully controlled for anatomical and physiological parameters relevant for edema formation and stroke outcome. BBB damage (p,0.05) and edema volumes (1.7 mm360.5 mm3 versus 0.8 mm360.4 mm3; p,0.0001) were significantly enhanced in Vasp2/2 mice compared to controls on day 1 after tMCAO. This was accompanied by a significant increase in infarct size (56.1 mm3617.3 mm3 versus 39.3 mm3610.7 mm3, respectively; p,0.01) and a non significant trend (p.0.05) towards worse neurological outcomes. Conclusion: Our study identifies VASP as critical regulator of BBB maintenance during acute ischemic stroke. Therapeutic modulation of VASP or VASP-dependent signalling pathways could become a novel strategy to combat excessive edema formation in ischemic brain damage
Low-Cost Flexible Nano-Sulfide/Carbon Composite Counter Electrode for Quantum-Dot-Sensitized Solar Cell
Cu2S nanocrystal particles were in situ deposited on graphite paper to prepare nano-sulfide/carbon composite counter electrode for CdS/CdSe quantum-dot-sensitized solar cell (QDSC). By optimization of deposition time, photovoltaic conversion efficiency up to 3.08% was obtained. In the meantime, this composite counter electrode was superior to the commonly used Pt, Au and carbon counter electrodes. Electrochemical impedance spectra further confirmed that low charge transfer resistance at counter electrode/electrolyte interface was responsible for this, implied the potential application of this composite counter electrode in high-efficiency QDSC
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