666 research outputs found
Dibutyryl cytidine 3′:5′-cyclic monophosphate; an inhibitor of A23187-stimulated macrophage leukotriene B4 synthesis
db-cCMP inhibits A23187-stimulated TXB2 and LTB4 synthesis by rat carrageenin-elicited peritoneal macrophages in vitro
Effects of short- and long-term feeding of L-carnitine and congeners on the production of eicosanoids from rat peritoneal leucocytes
The effect of short- and long-term feeding with L-carnitine, L-acetyl carnitine and L-propionyl carnitine on the production of eicosanoids front in vitro stimulated carrageenan-induced rat peritoneal macrophages was investigated. Both young (4 weeks) and old (18 months) rats were used. A lower number of cells was isolated from the peritonea of treated than control young rats after 4 d feeding, but after 60 d no differences were observed. A similar reduction in cell number was found when old animals were given L-acetyl carnitine or L-propionyl carnitine (acutely) or L-acetyl carnitine or L-carnitine (chronically). Plasma carnitine levels were higher in young rats given carnitine both chronically and acutely. Carnitine derivatives were without effect. In contrast, levels of total carnitine in the plasma of old rats given L-carnitine and L-acetyl carnitine for 4 d and 60 d were higher than in controls. There was no correlation between total plasma carnitine level and effects on prostaglandin, thromboxane and leukotriene B4 (LTB4) production. In young rats the most important changes were observed in relation to the production of prostacyclin (PGI2), measured as 6 keto-prostaglandin Flα. Prostacyclin production was higher in the groups given carnitine or its derivatives. The net result of the changes in PGI2 was that the 6 keto-prostaglandin F1α: thromboxane B2 and the 6 keto-prostaglandin Flα:LTB4 ratios tended to be higher in cells from young animals following short-term feeding with L-carnitine. When young rats were given carnitine compounds for 60 d PGI2 production was lower in cells from L-acetyl carnitine- and L-propionyl carnitine-fed animals. The net result of the changes in PGI2 was that the 6 keto-prostaglandin F1α: thromboxane B2 and the 6 keto-prostaglandin F1α:LTB4 ratios were lower in cells from animals fed with carnitine compounds. In old rats the PGI2 production was lower after short-term feeding with carnitine compounds and was higher after long-term feeding. LTB4 production was lower after L-carnitine and L-acetyl carnitine treatment for 4 d and also lower after 60 d treatment with L-acetyl carnitine. The net results of the changes in PGI2 were that the 6 keto-prostaglandin F1α: thromboxane B2 and the 6 keto-prostaglandin F1α:LTB4 ratios were lower after short-term feeding of all three compounds and higher after the long-term treatment with L-acetyl carnitine and L-propionyl carnitine in old rats. By long-term treatment with low-dose aspirin of patients with heart failure and claudication, the 6 keto-prostaglandin F1α: thromboxane B2 ratio is positively increased, which is a beneficial cardioprotective effect. The mechanism of action of carnitine in heart failure and claudication could also be achieved by an increase of this ratio. Our results suggest that elderly patients could be treated chronically by carnitine to obtain this beneficial effect
Coupled trace element and Sr-Nd-(Pb) isotopes in olivine-hosted melt inclusions from the Mariana arc
The Mariana arc forms part of the 2500 km Izu–Bonin–Mariana arc system caused by westward subduction of the Pacific Plate beneath the Philippine Sea Plate over the last ~45 Myr. The magmatism produced in this comparatively simple arc setting records a moderate flux of fluids and sediments from the downgoing plate, however, the low MgO (<6 wt.%) of the lavas imply that magma mixing, crystal fractionation and crustal assimilation mask the primitive melt compositions. Olivine-hosted melt inclusions (MIs), in contrast, provide access to melt trapped deep in the magmatic plumbing system allowing more precise determination of the nature and quantity of recycled components. Here we analyse coupled trace element and Sr-Nd(-Pb) isotope compositions of olivine-hosted MIs in five samples from four islands within the Central Island province: Agrigan (AGR2, AGR6), Pagan (PAG3), Guguan (GUG6) and Sarigan (SAG1). Bulk rock MgO contents range from 4 to 5.7 wt.% [1]. We specifically target melt inclusions in olivine phenocrysts with the highest fortsterite content (Fo = Mg/(Mg+Fe)*100): AGR: 80-86; PAG: 76-81; GUG: 76-88; SAG: 84-88 mol%. Trace element contents and ratios of the selected MIs record marked differences between islands and show larger variability compared to published bulk rock and MI compositions [2]. Ba/La and Th/Nb or La/Sm ratios – indicators of slab fluids versus sediment melts, respectively – confirm that Guguan inclusions are dominated by a fluid component whereas Agrigan and Sarigan reflect a larger sediment contribution. Pagan inclusions show intermediate compositions and a restricted range indicating the influence of both fluids and sediments. Sr-Nd-(Pb) isotope compositions of individual and pooled melt inclusions will be determined by wet chemistry and TIMS techniques using 10^13 Ω amplifier technology [3] to further identify and quantify the recycled components. [1] Elliott et al. (1997). Journal of Geophysical Research, 102: 14991-15019. [2] Kent & Elliott (2002). Chemical Geology, 183: 263-286. [3] Koornneef et al. (2019). Nature Communications 10, 323
Testing Lorentz invariance of dark matter
We study the possibility to constrain deviations from Lorentz invariance in
dark matter (DM) with cosmological observations. Breaking of Lorentz invariance
generically introduces new light gravitational degrees of freedom, which we
represent through a dynamical timelike vector field. If DM does not obey
Lorentz invariance, it couples to this vector field. We find that this coupling
affects the inertial mass of small DM halos which no longer satisfy the
equivalence principle. For large enough lumps of DM we identify a (chameleon)
mechanism that restores the inertial mass to its standard value. As a
consequence, the dynamics of gravitational clustering are modified. Two
prominent effects are a scale dependent enhancement in the growth of large
scale structure and a scale dependent bias between DM and baryon density
perturbations. The comparison with the measured linear matter power spectrum in
principle allows to bound the departure from Lorentz invariance of DM at the
per cent level.Comment: 42 pages, 9 figure
Field testing for toxic algae with a microarray: initial results from the MIDTAL project
One of the key tasks in the project MIDTAL (MIcroarrays for the Detection of Toxic ALgae) is to demonstrate the applicability of microarrays to monitor harmful algae across a broad range of ecological niches and toxic species responsible for harmful algal events. Water samples are collected from a series of sites used in national phytoplankton and biotoxin monitoring programmes across Europe. The samples are filtered; the rRNA is extracted, labelled with a fluorescent dye and applied to a microarray chip. The signal intensity from >120 probes previously spotted on the chip is measured and analysed. Preliminary results comparing microarray signal intensities with actual field counts are presented
Integrated microsphere planar lightwave circuits
Multicomponent glass microspheres self-assembled on optical waveguides combine tailored optical properties with strong light/material interaction potentially leading to compact low-power photonic devices. Progress and prospects for microsphere/waveguide integration will be described
Field testing for toxic algae with a microarray: initial results from the MIDTAL project
One of the key tasks in MIDTAL (MIcroarrays for the Detection of Toxic ALgae) is to demonstrate
the applicability of microarrays to monitor harmful algae across a broad range of ecological niches
and toxic species responsible for harmful algal events. Water samples are collected from a series of
sites used in national phytoplankton and biotoxin monitoring across Europe. The samples are filtered;
rRNA is extracted, labelled with a fluorescent dye and applied to a microarray chip. The signal
intensity from >120 probes previously spotted on the chip is measured and analysed. Preliminary
results comparing microarray signal intensities with actual field counts are presented.VersiĂłn del edito
Origins of the Ambient Solar Wind: Implications for Space Weather
The Sun's outer atmosphere is heated to temperatures of millions of degrees,
and solar plasma flows out into interplanetary space at supersonic speeds. This
paper reviews our current understanding of these interrelated problems: coronal
heating and the acceleration of the ambient solar wind. We also discuss where
the community stands in its ability to forecast how variations in the solar
wind (i.e., fast and slow wind streams) impact the Earth. Although the last few
decades have seen significant progress in observations and modeling, we still
do not have a complete understanding of the relevant physical processes, nor do
we have a quantitatively precise census of which coronal structures contribute
to specific types of solar wind. Fast streams are known to be connected to the
central regions of large coronal holes. Slow streams, however, appear to come
from a wide range of sources, including streamers, pseudostreamers, coronal
loops, active regions, and coronal hole boundaries. Complicating our
understanding even more is the fact that processes such as turbulence,
stream-stream interactions, and Coulomb collisions can make it difficult to
unambiguously map a parcel measured at 1 AU back down to its coronal source. We
also review recent progress -- in theoretical modeling, observational data
analysis, and forecasting techniques that sit at the interface between data and
theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue
connected with a 2016 ISSI workshop on "The Scientific Foundations of Space
Weather." 44 pages, 9 figure
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