108 research outputs found
Calcitonin receptor-like receptor is expressed on gastrointestinal immune cells
Background/Aims: Pharmacological and morphological studies suggest that the gut mucosal immune system and local neuropeptide-containing neurones interact. We aimed to determine whether gut immune cells are targets for calcitonin gene-related peptide (CGRP), which has potent immune regulatory properties. Methods: Using density gradient centrifugation, rat lamina propria mononuclear cells (LP-MNCs) and intra-epithelial lymphocytes (IELs) were isolated. RT-PCR was employed for the detection of mRNA of rat calcitonin receptor-like receptor (CRLR), which is considered to represent the pharmacologically defined CGRP receptor-1 subtype, as well as mRNA of the receptor activity-modifying proteins, which are essential for CRLR function and determine ligand specificity. A radioreceptor assay was employed for the detection of specific CGRP binding sites. Results: RT-PCR and DNA sequencing showed that LP-MNCs and IELs express CRLR. Incubation of isolated LP-MNCs with radiolabelled alphaCGRP revealed the existence of specific binding sites for CGRP. Conclusion: These novel data indicate that mucosal immune cells of the rat gut are a target for CGRP and provide significant evidence that CGRP functions as an immune regulator in the gut mucosa. Copyright (C) 2002 S. Karger AG, Basel
Ion acceleration from laser-driven electrostatic shocks
Multi-dimensional particle-in-cell simulations are used to study the
generation of electrostatic shocks in plasma and the reflection of background
ions to produce high-quality and high-energy ion beams. Electrostatic shocks
are driven by the interaction of two plasmas with different density and/or
relative drift velocity. The energy and number of ions reflected by the shock
increase with increasing density ratio and relative drift velocity between the
two interacting plasmas. It is shown that the interaction of intense lasers
with tailored near-critical density plasmas allows for the efficient heating of
the plasma electrons and steepening of the plasma profile at the critical
density interface, leading to the generation of high-velocity shock structures
and high-energy ion beams. Our results indicate that high-quality 200 MeV
shock-accelerated ion beams required for medical applications may be obtained
with current laser systems.Comment: 33 pages, 12 figures, accepted for publication in Physics of Plasma
Laser-driven shock acceleration of monoenergetic ion beams
We show that monoenergetic ion beams can be accelerated by moderate Mach
number collisionless, electrostatic shocks propagating in a long scale-length
exponentially decaying plasma profile. Strong plasma heating and density
steepening produced by an intense laser pulse near the critical density can
launch such shocks that propagate in the extended plasma at high velocities.
The generation of a monoenergetic ion beam is possible due to the small and
constant sheath electric field associated with the slowly decreasing density
profile. The conditions for the acceleration of high-quality, energetic ion
beams are identified through theory and multidimensional particle-in-cell
simulations. The scaling of the ion energy with laser intensity shows that it
is possible to generate MeV proton beams with state-of-the-art 100
TW class laser systems.Comment: 13 pages, 4 figures, accepted for publication in Physical Review
Letter
Improved Filters for Angular Filter Refractometry
Angular filter refractometry is an optical diagnostic that measures absolute
contours of line-integrated density gradient by placing a filter with
alternating opaque and transparent zones in the focal plane of a probe beam,
which produce corresponding alternating light and dark regions in the image
plane. Identifying transitions between these regions with specific zones on the
angular filter (AF) allows the line-integrated density to be determined, but
the sign of the density gradient at each transition is degenerate and must be
broken using other information about the object plasma. Additional features
from diffraction in the filter plane often complicate data analysis. In this
paper, we present an improved AF design that uses a stochastic pixel pattern
with a sinusoidal radial profile to minimize unwanted diffraction effects in
the image caused by the sharp edges of the filter bands. We also present a
technique in which a pair of AFs with different patterns on two branches of the
same probe beam can be used to break the density gradient degeneracy. Both
techniques are demonstrated using a synthetic diagnostic and data collected on
the OMEGA EP laser
A complementary compact laser based neutron source
Several experiments of neutron generation using high intensity laser sources,
with a power exceeding 10^19W/cm^2 via TNSA (Target Normal Sheath Acceleration)
or other similar methods, have been performed in the past years in different
laboratories. However, so far there is no one running neutron source based on
such a technology. In the framework of the Conceptual Report Design of a new
accelerator in the Eupraxia project we are studying the possibility to have a
laser-based neutron source, not only by TNSA but also from self-injection
schemes. We focus our attention on the applications in cultural heritage
studies as well also on the complementary role that such a source can have in
the framework of large facilities devoted to radiation production.Comment: 4 pages, two figures, 3rd European Advanced Accelerators Concept
Collisionless shock acceleration of narrow energy spread ion beams from mixed species plasmas using 1 m lasers
Collisionless shock acceleration of protons and C ions has been
achieved by the interaction of a 10 W/cm, 1 m laser with a
near-critical density plasma. Ablation of the initially solid density target by
a secondary laser allowed for systematic control of the plasma profile. This
enabled the production of beams with peaked spectra with energies of 10-18
MeV/a.m.u. and energy spreads of 10-20 with up to 3x10 particles within
these narrow spectral features. The narrow energy spread and similar velocity
of ion species with different charge-to-mass ratio are consistent with
acceleration by the moving potential of a shock wave. Particle-in-cell
simulations show shock accelerated beams of protons and C ions with
energy distributions consistent with the experiments. Simulations further
indicate the plasma profile determines the trade-off between the beam charge
and energy and that with additional target optimization narrow energy spread
beams exceeding 100 MeV/a.m.u. can be produced using the same laser conditions.Comment: Accepted for publication in Physical Review Accelerators and Beam
Potential link between the Sphingosine-1-Phosphate (S1P) system and defective alveolar macrophage phagocytic function in Chronic Obstructive Pulmonary Disease (COPD)
We previously reported that alveolar macrophages from patients with chronic obstructive pulmonary disease (COPD) are defective in their ability to phagocytose apoptotic cells, with a similar defect in response to cigarette smoke. The exact mechanisms for this defect are unknown. Sphingolipids including ceramide, sphingosine and sphingosine-1-phosphate (S1P) are involved in diverse cellular processes and we hypothesised that a comprehensive analysis of this system in alveolar macrophages in COPD may help to delineate the reasons for defective phagocytic function.We compared mRNA expression of sphingosine kinases (SPHK1/2), S1P receptors (S1PR1-5) and S1P-degrading enzymes (SGPP1, SGPP2, SGPL1) in bronchoalveolar lavage-derived alveolar macrophages from 10 healthy controls, 7 healthy smokers and 20 COPD patients (10 current- and 10 ex-smokers) using Real-Time PCR. Phagocytosis of apoptotic cells was investigated using flow cytometry. Functional associations were assessed between sphingosine signalling system components and alveolar macrophage phagocytic ability in COPD. To elucidate functional effects of increased S1PR5 on macrophage phagocytic ability, we performed the phagocytosis assay in the presence of varying concentrations of suramin, an antagonist of S1PR3 and S1PR5. The effects of cigarette smoking on the S1P system were investigated using a THP-1 macrophage cell line model.We found significant increases in SPHK1/2 (3.4- and 2.1-fold increases respectively), S1PR2 and 5 (4.3- and 14.6-fold increases respectively), and SGPL1 (4.5-fold increase) in COPD vs. controls. S1PR5 and SGPL1 expression was unaffected by smoking status, suggesting a COPD "disease effect" rather than smoke effect per se. Significant associations were noted between S1PR5 and both lung function and phagocytosis. Cigarette smoke extract significantly increased mRNA expression of SPHK1, SPHK2, S1PR2 and S1PR5 by THP-1 macrophages, confirming the results in patient-derived macrophages. Antagonising SIPR5 significantly improved phagocytosis.Our results suggest a potential link between the S1P signalling system and defective macrophage phagocytic function in COPD and advise therapeutic targets.Jameel Barnawi, Hai Tran, Hubertus Jersmann, Stuart Pitson, Eugene Roscioli, Greg Hodge, Robyn Meech, Rainer Haberberger, Sandra Hodg
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