507 research outputs found
Ten-Color flow cytometry reveals distinct patterns of expression of CD124 and CD126 by developing thymocytes
<p>Abstract</p> <p>Background</p> <p>We have developed a 12-parameter/10-color flow cytometric staining method for the simultaneous detection and characterization of 21 mouse thymocyte subpopulations that represent discreet stages of T cell development. To demonstrate the utility of this method, we assessed cytokine receptor expression on mouse thymocyte subsets. These experiments revealed distinct patterns of surface expression of receptors for the cytokines IL-4 and IL-6.</p> <p>Results</p> <p>The IL-4 receptor α chain (CD124) was highly expressed on the earliest thymocyte subsets, then downregulated prior to T cell receptor β-selection and finally upregulated in the CD4/CD8 double positive cells prior to positive selection. The IL-6 receptor α chain (CD126) showed a different pattern of expression. It was expressed on the most mature subsets within the CD4 and CD8 single positive (SP) compartments and was absent on all other thymocytes with the exception of a very small cKit<sup>-</sup>CD4<sup>-</sup>CD8<sup>- </sup>population. Intracellular staining of SP thymocytes for phosphorylated STAT-1 demonstrated that IL-6 signaling was confined to the most mature SP subsets.</p> <p>Conclusions</p> <p>This 12-parameter staining methodology uses only commercially available fluorochrome-coupled monoclonal antibodies and therefore could be employed by any investigator with access to a 4-laser flow cytometer. This novel staining scheme allowed us to easily phenotype thymocyte subpopulations that span across development, from the early thymic progenitors (ETPs) to the most mature subsets of the CD4 and CD8 single positive populations.</p
Shallow decay phase of GRB X-ray afterglows from relativistic wind bubbles
The postburst object of a GRB is likely to be a highly magnetized, rapidly
rotating compact object (e.g., a millisecond magnetar), which could produce an
ultrarelativistic electron-positron-pair wind. The interaction of such a wind
with an outwardly expanding fireball ejected during the burst leads to a
relativistic wind bubble (RWB). We numerically calculate the dynamics and
radiative properties of RWBs and use this model to explain the shallow decay
phase of the early X-ray afterglows observed by Swift. We find that RWBs can
fall into two types: forward-shock-dominated and reverse-shock-dominated
bubbles. Their radiation during a period of seconds is
dominated by the shocked medium and the shocked wind, respectively, based on
different magnetic energy fractions of the shocked materials. For both types,
the resulting light curves always have a shallow decay phase. In addition, we
provide an example fit to the X-ray afterglows of GRB 060813 and GRB 060814 and
show that they could be produced by forward-shock-dominated and
reverse-shock-dominated bubbles, respectively. This implies that, for some
early afterglows (e.g., GRB 060814), the long-lasting reverse shock emission is
strong enough to explain their shallow decay phase.Comment: 5 pages, 4 figures, Accepted for Publication in A&
UV/Optical Emission Accompanying Gamma-ray Burst
We discuss the possible simultaneously UV/optical emission accompanying
Gamma-ray bursts (GRBs). We show that as long as the intrinsic spectrum of GRB
can extend to 10 GeV or higher, there is a large amount of relativistic
pairs generated due to the annihilation of the soft rays with
the very energetic photons, which dominates over the electrons/positrons
associated with the fireball, no matter the fireball is highly magnetized or
not (For the highly magnetized fireball, the magnetic field is ordered, the
high linear polarization of the multi-wavelength emission is expected). We find
that these pairs can power an UV flash with
magnitude, and the corresponding optical emission can be up to magnitude. Such bright UV emission can be detected by
the upcoming satellite Swift, planned for launch in early 2004. The behavior of
the optical-UV spectrum () differs significantly from
that of the reverse shock emission (, ), which is a signature of the emission accompanying with GRB. The
mild optical emission can be detected with the ROTSE-IIIa telescope system, if
the response to the GRB alert is fast enough.Comment: 5 pages, no figures. MNRAS in pres
The very early afterglow powered by the ultra-relativistic mildly magnetized outflows
In the Poynting Flux dominated outflow (the initial ratio of the
electromagnetic energy flux to the particle energy flux ) model
for Gamma-ray bursts, nearly half of the internally dissipated magnetic energy
is converted into the prompt ray energy emission and the rest is
converted into the kinetic energy of the outflow. Consequently, at the end of
the ray burst, decreases significantly ( or
even smaller). We numerically investigate the very early reverse shock emission
powered by such mildly magnetized outflows interacting with medium--uniform
interstellar medium (ISM) or stellar wind (WIND). We show that for
and typical parameters of Gamma-ray bursts, both the
ISM-ejecta interaction and the WIND-ejecta interaction can power very strong
optical emission ( magnitude or even brighter).
Similar to the very early afterglow powered by the non-magnetized ejecta
interacting with the external medium, the main difference between the
ISM-ejecta interaction case and the WIND-ejecta interaction case is that,
before the reverse shock crosses the ejecta, the R-band emission flux increases
rapidly for the former, but for the latter it increases only slightly. (The
abstract has been shortened). We suggest that the linear polarization detection
of the early multi-wavelength afterglow is highly needed to see whether the
outflows powering GRBs are magnetized or not.Comment: 8 pages, 3 figures, A&A in pres
Intragenic suppressors of temperature-sensitive rne mutations lead to the dissociation of RNase E activity on mRNA and tRNA substrates in Escherichia coli
RNase E of Escherichia coli is an essential endoribonuclease that is involved in many aspects of RNA metabolism. Point mutations in the S1 RNA-binding domain of RNase E (rne-1 and rne-3071) lead to temperature-sensitive growth along with defects in 5S rRNA processing, mRNA decay and tRNA maturation. However, it is not clear whether RNase E acts similarly on all kinds of RNA substrates. Here we report the isolation and characterization of three independent intragenic second-site suppressors of the rne-1 and rne-3071 alleles that demonstrate for the first time the dissociation of the in vivo activity of RNase E on mRNA versus tRNA and rRNA substrates. Specifically, tRNA maturation and 9S rRNA processing were restored to wild-type levels in each of the three suppressor mutants (rne-1/172, rne-1/186 and rne-1/187), while mRNA decay and autoregulation of RNase E protein levels remained as defective as in the rne-1 single mutant. Each single amino acid substitution (Gly→Ala at amino acid 172; Phe → Cys at amino acid 186 and Arg → Leu at amino acid 187) mapped within the 5′ sensor region of the RNase E protein. Molecular models of RNase E suggest how suppression may occur
Amine functionalization of cholecyst-derived extracellular matrix with generation 1 PAMAM dendrimer
This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Biomacromolecules, copyright © American Chemical Society after peer review. To access the final edited and published work, see http://pubs.acs.org/doi/pdf/10.1021/bm701055k.A method to functionalize cholecyst-derived extracellular matrix (CEM) with free amine groups was established in an attempt to improve its potential for tethering of bioactive molecules. CEM was incorporated with Generation-1 polyamidoamine (G1 PAMAM) dendrimer by using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide and N-hydroxysuccinimide cross-linking system. The nature of incorporation of PAMAM dendrimer was evaluated using shrink temperature measurements, Fourier transform infrared (FTIR) assessment, ninhydrin assay, and swellability. The effects of PAMAM incorporation on mechanical and degradation properties of CEM were evaluated using a uniaxial mechanical test and collagenase degradation assay, respectively. Ninhydrin assay and FTIR assessment confirmed the presence of increasing free amine groups with increasing quantity of PAMAM in dendrimer-incorporated CEM (DENCEM) scaffolds. The amount of dendrimer used was found to be critical in controlling scaffold degradation, shrink temperature, and free amine content. Cell culture studies showed that fibroblasts seeded on DENCEM maintained their metabolic activity and ability to proliferate in vitro. In addition, fluorescence cell staining and scanning electron microscopy analysis of cell-seeded DENCEM showed preservation of normal fibroblast morphology and phenotype
A Toy Model for Magnetized Neutrino-Dominated Accretion Flows
In this paper, we present a simplified model for magnetized
neutrino-dominated accretion flow (NDAF) in which effect of black hole (BH)
spin is taken into account by adopting a set of relativistic correction factor,
and the magnetic field is parameterized as \beta, the ratio of the magnetic
pressure to the total pressure. It is found that the disc properties are
sensitive to the values of the BH spin and \beta, and more energy can be
extracted from NDAF for the faster spin and lower \beta.Comment: 4 pages, 3 figures, accepted for publication in Science in China
Series
QCD Corrections to QED Vacuum Polarization
We compute QCD corrections to QED calculations for vacuum polarization in
background magnetic fields. Formally, the diagram for virtual loops
is identical to the one for virtual loops. However due to
confinement, or to the growth of as decreases, a direct
calculation of the diagram is not allowed. At large we consider the
virtual diagram, in the intermediate region we discuss the role of
the contribution of quark condensates \left and at the
low-energy limit we consider the , as well as charged pion
loops. Although these effects seem to be out of the measurement accuracy of
photon-photon laboratory experiments they may be relevant for -ray
burst propagation. In particular, for emissions from the center of the galaxy
(8.5 kpc), we show that the mixing between the neutral pseudo-scalar pion
and photons renders a deviation from the power-law spectrum in the
range. As for scalar quark condensates \left and
virtual loops are relevant only for very high radiation density
and very strong magnetic fields of order .Comment: 15 pages, 4 figures; Final versio
High potency silencing by single-stranded boranophosphate siRNA
In RNA interference (RNAi), double-stranded short interfering RNA (ds-siRNA) inhibits expression from complementary mRNAs. Recently, it was demonstrated that short, single-stranded antisense RNA (ss-siRNA) can also induce RNAi. While ss-siRNA may offer several advantages in both clinical and research applications, its overall poor activity compared with ds-siRNA has prevented its widespread use. In contrast to the poor gene silencing activity of native ss-siRNA, we found that the silencing activity of boranophosphate-modified ss-siRNA is comparable with that of unmodified ds-siRNA. Boranophosphate ss-siRNA has excellent maximum silencing activity and is highly effective at low concentrations. The silencing activity of boranophosphate ss-siRNA is also durable, with significant silencing up to 1 week after transfection. Thus, we have demonstrated that boranophosphate-modified ss-siRNA can silence gene expression as well as native ds-siRNA, suggesting that boranophosphate-modified ss-siRNAs should be investigated as a potential new class of therapeutic agents
Gravitational radiation from gamma-ray bursts as observational opportunities for LIGO and VIRGO
Gamma-ray bursts are believed to originate in core-collapse of massive stars.
This produces an active nucleus containing a rapidly rotating Kerr black hole
surrounded by a uniformly magnetized torus represented by two counter-oriented
current rings. We quantify black hole spin-interactions with the torus and
charged particles along open magnetic flux-tubes subtended by the event
horizon. A major output of Egw=4e53 erg is radiated in gravitational waves of
frequency fgw=500 Hz by a quadrupole mass-moment in the torus. Consistent with
GRB-SNe, we find (i) Ts=90s (tens of s, Kouveliotou et al. 1993), (ii)
aspherical SNe of kinetic energy Esn=2e51 erg (2e51 erg in SN1998bw, Hoeflich
et al. 1999) and (iii) GRB-energies Egamma=2e50 erg (3e50erg in Frail et al.
2001). GRB-SNe occur perhaps about once a year within D=100Mpc. Correlating
LIGO/Virgo detectors enables searches for nearby events and their spectral
closure density 6e-9 around 250Hz in the stochastic background radiation in
gravitational waves. At current sensitivity, LIGO-Hanford may place an upper
bound around 150MSolar in GRB030329. Detection of Egw thus provides a method
for identifying Kerr black holes by calorimetry.Comment: to appear in PRD, 49
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