3,331 research outputs found
De Novo Superinfection of Hepatitis B Virus in an Anti-HBs Positive Patient with Recurrent Hepatitis C Following Liver Transplantation
A 60-year-old woman with end stage liver cirrhosis caused by genotype 2 hepatitis C virus (HCV) infection received an orthotopic liver transplantation (OLT). The patient was negative for the hepatitis B surface antigen (HBsAg) and positive for the anti-hepatitis B surface antibody (anti-HBs) prior to and one and a half months following the OLT. Due to reactivation of hepatitis C, treatment with interferon-alpha and Ribavirin started two months following the OLT and resulted in a sustained virological response. We performed a liver biopsy because a biochemical response was not achieved. Surprisingly, liver pathology showed HBsAg-positive hepatocytes with a lobular hepatitis feature, which had been negative in the liver biopsy specimen obtained one and a half months post-OLT. High titers of both HBsAg and HBeAg were detected, while anti-HBs antibodies were not found. Tests for IgM anti-hepatitis B core antibody and anti-delta virus antibodies were negative. The serum HBV DNA titer was over 1×107 copies/mL. A sequencing analysis showed no mutation in the "a" determinant region, but revealed a mixture of wild and mutant strains at an overlapping region of the S and P genes (S codon 213 (Leu/Ile); P codons 221 (Phe/Tyr) and 222 (Ala/Thr)). These findings suggest that de novo hepatitis B can develop in patients with HCV infection during the post-OLT period despite the presence of protective anti-HBs
Rapid clearance of cellular debris by microglia limits secondary neuronal cell death after brain injury in vivo
Moderate or severe traumatic brain injury (TBI) causes widespread neuronal cell death. Microglia, the resident macrophages of the brain, react to injury by migrating to the lesion site, where they phagocytose cellular debris. Microglial phagocytosis can have both beneficial (e.g. debris clearance) and detrimental (e.g. respiratory burst, phagoptosis) consequences. Hence, whether the overall effect of microglial phagocytosis after brain injury in vivo is neuroprotective or neurotoxic is not known. Here, we establish a system with which to carry out dynamic real-time analyses of the mechanisms regulating cell death after brain injury in vivo. We show that mechanical injury to the larval zebrafish brain induces distinct phases of primary and secondary cell death. Excitotoxicity contributes to secondary cell death in zebrafish, reflecting findings from mammals. Microglia arrive at the lesion site within minutes of injury, where they rapidly engulf dead cells. Importantly, the rate of secondary cell death is increased when the rapid removal of cellular debris by microglia is reduced pharmacologically or genetically. In summary, our results provide evidence that microglial debris clearance is neuroprotective after brain injury in vivo
Single Spin Asymmetry in Polarized Proton-Proton Elastic Scattering at GeV
We report a high precision measurement of the transverse single spin
asymmetry at the center of mass energy GeV in elastic
proton-proton scattering by the STAR experiment at RHIC. The was measured
in the four-momentum transfer squared range \GeVcSq, the region of a significant interference between the
electromagnetic and hadronic scattering amplitudes. The measured values of
and its -dependence are consistent with a vanishing hadronic spin-flip
amplitude, thus providing strong constraints on the ratio of the single
spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated
by the Pomeron amplitude at this , we conclude that this measurement
addresses the question about the presence of a hadronic spin flip due to the
Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure
Beam energy dependent two-pion interferometry and the freeze-out eccentricity of pions in heavy ion collisions at STAR
We present results of analyses of two-pion interferometry in Au+Au collisions
at = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV measured in the
STAR detector as part of the RHIC Beam Energy Scan program. The extracted
correlation lengths (HBT radii) are studied as a function of beam energy,
azimuthal angle relative to the reaction plane, centrality, and transverse mass
() of the particles. The azimuthal analysis allows extraction of the
eccentricity of the entire fireball at kinetic freeze-out. The energy
dependence of this observable is expected to be sensitive to changes in the
equation of state. A new global fit method is studied as an alternate method to
directly measure the parameters in the azimuthal analysis. The eccentricity
shows a monotonic decrease with beam energy that is qualitatively consistent
with the trend from all model predictions and quantitatively consistent with a
hadronic transport model.Comment: 27 pages; 27 figure
Measurements of and Production in + Collisions at = 200 GeV
We report measurements of charmed-hadron (, ) production cross
sections at mid-rapidity in + collisions at a center-of-mass energy of
200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the
hadronic decays , and their charge conjugates,
covering the range of 0.62.0 GeV/ and 2.06.0 GeV/ for
and , respectively. From this analysis, the charm-pair production cross
section at mid-rapidity is = 170 45
(stat.) (sys.) b. The extracted charm-pair cross section is
compared to perturbative QCD calculations. The transverse momentum differential
cross section is found to be consistent with the upper bound of a Fixed-Order
Next-to-Leading Logarithm calculation.Comment: 15 pages, 16 figures. Revised version submitted to Phys. Rev.
Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC
Local parity-odd domains are theorized to form inside a Quark-Gluon-Plasma
(QGP) which has been produced in high-energy heavy-ion collisions. The local
parity-odd domains manifest themselves as charge separation along the magnetic
field axis via the chiral magnetic effect (CME). The experimental observation
of charge separation has previously been reported for heavy-ion collisions at
the top RHIC energies. In this paper, we present the results of the beam-energy
dependence of the charge correlations in Au+Au collisions at midrapidity for
center-of-mass energies of 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV from the STAR
experiment. After background subtraction, the signal gradually reduces with
decreased beam energy, and tends to vanish by 7.7 GeV. The implications of
these results for the CME will be discussed.Comment: 6 pages, 4 figures, accepted by Phys. Rev. Lett (more model
comparisons have been added in version 2
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