4,334 research outputs found
Uptake and intra-inclusion accumulation of exogenous immunoglobulin by Chlamydia-infected cells
<p>Abstract</p> <p>Background</p> <p>Obligate intracellular pathogens belonging to the <it>Chlamydiaceae </it>family possess a number of mechanisms by which to manipulate the host cell and surrounding environment. Such capabilities include the inhibition of apoptosis, down-regulation of major histocompatability complex (MHC) and CD1/d gene expression, and the acquisition of host-synthesized nutrients. It is also documented that a limited number of host-derived macromolecules such as β-catenin and sphingomyelin accumulate within the inclusion.</p> <p>Results</p> <p>This report provides evidence that immunoglobulin, inherently present in the extracellular environment <it>in vivo </it>and <it>in vitro</it>, enters infected cells and accumulates within the chlamydial inclusion. Using epi-fluorescent and confocal microscopy, this selective uptake of Ig is shown to occur among human leukocytes <it>in vivo </it>as well as cells cultured <it>in vitro</it>. These findings were confirmed by detection of IgG in the lysate of infected cells by western blot hybridization. Sequestered antibodies appear to be present during the entire course of the chlamydial developmental cycle and are distributed throughout this compartment. IgG pre-labeled with fluorescein, when added to the supernatant of infected cell cultures, was also imported and readily visualized. Accumulation of these molecules within the inclusion and the failure of bovine serum albumin or F(ab')<sub>2 </sub>fragments to accumulate in a similar manner suggests the process of entry is specific for intact IgG molecules and not a result of pinocytosis, diffusion, or any other mass endocytic event.</p> <p>Conclusion</p> <p>Sequestration of a host cell-derived protein within the chlamydial inclusion, although unexpected, is not an unprecedented occurrence. However, selective accumulation of an exogenous host protein, such as extracellular IgG, has not been previously reported in connection with chlamydial infections. The selectivity of this process may indicate that this uptake plays an important role in pathogen physiology or virulence during infection and the phenomenon itself may give rise to novel diagnostic and therapeutic approaches.</p
Collective excitation of a Bose-Einstein condensate by modulation of the atomic scattering length
We excite the lowest-lying quadrupole mode of a Bose-Einstein condensate by
modulating the atomic scattering length via a Feshbach resonance. Excitation
occurs at various modulation frequencies, and resonances located at the natural
quadrupole frequency of the condensate and at the first harmonic are observed.
We also investigate the amplitude of the excited mode as a function of
modulation depth. Numerical simulations based on a variational calculation
agree with our experimental results and provide insight into the observed
behavior.Comment: Submitted to PR
Antibody-Based Ticagrelor Reversal Agent in Healthy Volunteers.
BACKGROUND: Ticagrelor is an oral P2Y12 inhibitor that is used with aspirin to reduce the risk of ischemic events among patients with acute coronary syndromes or previous myocardial infarction. Spontaneous major bleeding and bleeding associated with urgent invasive procedures are concerns with ticagrelor, as with other antiplatelet drugs. The antiplatelet effects of ticagrelor cannot be reversed with platelet transfusion. A rapid-acting reversal agent would be useful.
METHODS: In this randomized, double-blind, placebo-controlled, phase 1 trial, we evaluated intravenous PB2452, a monoclonal antibody fragment that binds ticagrelor with high affinity, as a ticagrelor reversal agent. We assessed platelet function in healthy volunteers before and after 48 hours of ticagrelor pretreatment and again after the administration of PB2452 or placebo. Platelet function was assessed with the use of light transmission aggregometry, a point-of-care P2Y12 platelet-reactivity test, and a vasodilator-stimulated phosphoprotein assay.
RESULTS: Of the 64 volunteers who underwent randomization, 48 were assigned to receive PB2452 and 16 to receive placebo. After 48 hours of ticagrelor pretreatment, platelet aggregation was suppressed by approximately 80%. PB2452 administered as an initial intravenous bolus followed by a prolonged infusion (8, 12, or 16 hours) was associated with a significantly greater increase in platelet function than placebo, as measured by multiple assays. Ticagrelor reversal occurred within 5 minutes after the initiation of PB2452 and was sustained for more than 20 hours (P\u3c0.001 after Bonferroni adjustment across all time points for all assays). There was no evidence of a rebound in platelet activity after drug cessation. Adverse events related to the trial drug were limited mainly to issues involving the infusion site.
CONCLUSIONS: In healthy volunteers, the administration of PB2452, a specific reversal agent for ticagrelor, provided immediate and sustained reversal of the antiplatelet effects of ticagrelor, as measured by multiple assays. (Funded by PhaseBio Pharmaceuticals; ClinicalTrials.gov number, NCT03492385.)
Critical behavior of thermopower and conductivity at the metal-insulator transition in high-mobility Si-MOSFET's
This letter reports thermopower and conductivity measurements through the
metal-insulator transition for 2-dimensional electron gases in high mobility
Si-MOSFET's. At low temperatures both thermopower and conductivity show
critical behavior as a function of electron density which is very similar to
that expected for an Anderson transition. In particular, when approaching the
critical density from the metallic side the diffusion thermopower appears to
diverge and the conductivity vanishes. On the insulating side the thermopower
shows an upturn with decreasing temperature.Comment: 4 pages with 3 figure
Bounds on the force between black holes
We treat the problem of N interacting, axisymmetric black holes and obtain
two relations among physical parameters of the system including the force
between the black holes. The first relation involves the total mass, the
angular momenta, the distances and the forces between the black holes. The
second one relates the angular momentum and area of each black hole with the
forces acting on it.Comment: 13 pages, no figure
Three-body recombination rates near a Feshbach resonance within a two-channel contact interaction model
We calculate the three-body recombination rate into a shallow dimer in a gas
of cold bosonic atoms near a Feshbach resonance using a two-channel contact
interaction model. The two-channel model naturally describes the variation of
the scattering length through the Feshbach resonance and has a finite effective
range. We confront the theory with the available experimental data and show
that the two-channel model is able to quantitatively describe the existing
data. The finite effective range leads to a reduction of the scaling factor
between the recombination minima from the universal value of 22.7. The
reduction is larger for larger effective ranges or, correspondingly, for
narrower Feshbach resonances.Comment: 9 pages, 7 figure
Dielectrophoresis-Driven Spreading of Immersed Liquid Droplets
In recent years electrowetting-on-dielectric (EWOD) has become an effective tool to control partial wetting. EWOD uses the liquid−solid interface as part of a capacitive structure that allows capacitive and interfacial energies to adjust by changes in wetting when the liquid−solid interface is charged due to an applied voltage. An important aspect of EWOD has been its applications in micro fluidics in chemistry and biology and in optical devices and displays in physics and engineering. Many of these rely on the use of a liquid droplet immersed in a second liquid due to the need either for neutral buoyancy to overcome gravity and shield against impact shocks or to encapsulate the droplet for other reasons, such as in microfluidic-based DNA analyses. Recently, it has been shown that nonwetting oleophobic surfaces can be forcibly wetted by nonconducting oils using nonuniform electric fields and an interface-localized form of liquid dielectrophoresis (dielectrowetting). Here we show that this effect can be used to create films of oil immersed in a second immiscible fluid of lower permittivity. We predict that the square of the thickness of the film should obey a simple law dependent on the square of the applied voltage and with strength dependent on the ratio of difference in permittivity to the liquid-fluid interfacial tension, Δε/γLF. This relationship is experimentally confirmed for 11 liquid−air and liquid−liquid combinations with Δε/γLF having a span of more than two orders of magnitude. We therefore provide fundamental understanding of dielectrowetting for liquid-in-liquid systems and also open up a new method to determine liquid−liquid interfacial tensions
Modulation of LISA free-fall orbits due to the Earth-Moon system
We calculate the effect of the Earth-Moon (EM) system on the free-fall motion
of LISA test masses. We show that the periodic gravitational pulling of the EM
system induces a resonance with fundamental frequency 1 yr^-1 and a series of
periodic perturbations with frequencies equal to integer harmonics of the
synodic month (9.92 10^-7 Hz). We then evaluate the effects of these
perturbations (up to the 6th harmonics) on the relative motions between each
test masses couple, finding that they range between 3mm and 10pm for the 2nd
and 6th harmonic, respectively. If we take the LISA sensitivity curve, as
extrapolated down to 10^-6 Hz, we obtain that a few harmonics of the EM system
can be detected in the Doppler data collected by the LISA space mission. This
suggests that the EM system gravitational near field could provide an absolute
calibration for the LISA sensitivity at very low frequencies.Comment: 15 pages, 5 figure
- …