808 research outputs found
BCP crystals increase prostacyclin production and upregulate the prostacyclin receptor in OA synovial fibroblasts: potential effects on mPGES1 and MMP-13
SummaryObjectiveTo investigate the potential involvement of prostacyclin in basic calcium phosphate (BCP) crystal-induced responses in osteoarthritic synovial fibroblasts (OASF).MethodsOASF grown in culture were stimulated with BCP crystals. Prostacyclin production was measured by enzyme immunoassay. Expression of messenger RNA (mRNA) transcripts was assessed by real-time polymerase chain reaction (PCR). Expression of prostacyclin synthase (PGIS) and the prostacyclin (IP) receptor was measured. The effects of iloprost, a prostacyclin analogue, on expression of genes implicated in osteoarthritis such as microsomal prostaglandin E2 synthase 1 (mPGES1) and matrix metalloproteinases (MMPs) were also studied. FPT inhibitor II, a farnesyl transferase inhibitor, was used to antagonize iloprost-induced responses.ResultsBCP crystal stimulation led to a five-fold increase in prostacyclin production in OASF compared to untreated cells. This induction was attenuated by cyclooxygenase (COX)-2 and COX-1 inhibition at 4 and 32h, respectively. PGIS and IP receptor transcripts were constitutively expressed in OASF. BCP crystals upregulated IP receptor expression two-fold. While iloprost diminished BCP crystal-stimulated IP receptor upregulation, the inhibitory effect of iloprost was blocked by the farnesyl transferase inhibitor. In addition, iloprost upregulated mPGES1 and downregulated MMP-13 expression in BCP crystal-stimulated OASF, effects that were not influenced by the farnesyl transferase inhibitor.ConclusionsThese data showed for the first time that BCP crystals can increase prostacyclin production and upregulate expression of the IP receptor in OASF. The potential of prostacyclin to influence BCP crystal-stimulated responses was supported by the effects of iloprost on the expression of the IP receptor, mPGES1 and MMP-13. These data demonstrate the potential involvement of prostacyclin in BCP crystal-associated osteoarthritis (OA) and suggest that inhibition of PG synthesis with non-steroidal anti-inflammatory drugs may have both deleterious and beneficial effects in BCP crystal-associated OA
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Savannah River Restart Peer Evaluation Program final examination report
During the period of August 13, 1990 through September 6, 1991 the Savannah River Peer Evaluation Program was administered during three distinct phases to 73 certified Central Control Room Operators, Central Control Room Supervisors, and Shift Technical Engineers assigned to the K Reactor, on the Savannah River Site (SRS). This program was conceived and developed by the Department of Energy (DOE) and it's implementation satisfies recommendations made by the Defense Nuclear Facilities Safety Board. The review identified both strengths and weaknesses of the procedures and personnel
Dielectrophoresis of charged colloidal suspensions
We present a theoretical study of dielectrophoretic (DEP) crossover spectrum
of two polarizable particles under the action of a nonuniform AC electric
field. For two approaching particles, the mutual polarization interaction
yields a change in their respective dipole moments, and hence, in the DEP
crossover spectrum. The induced polarization effects are captured by the
multiple image method. Using spectral representation theory, an analytic
expression for the DEP force is derived. We find that the mutual polarization
effects can change the crossover frequency at which the DEP force changes sign.
The results are found to be in agreement with recent experimental observation
and as they go beyond the standard theory, they help to clarify the important
question of the underlying polarization mechanisms
Temperature dependence of the energy of a vortex in a two-dimensional Bose gas
We evaluate the thermodynamic critical angular velocity Omega_c(T) for
creation of a vortex of lowest quantized angular momentum in a strictly
two-dimensional Bose gas at temperature T, using a mean-field two-fluid model
for the condensate and the thermal cloud. Our results show that (i) a
Thomas-Fermi description of the condensate badly fails in predicting the
particle density profiles and the energy of the vortex as functions of T; and
(ii) an extrapolation of a simple Thomas-Fermi formula for Omega_c(0) is
nevertheless approximately useful up to T = 0.5 T_c.Comment: 9 pages, 4 figure
Density profile of a strictly two-dimensional Bose gas at finite temperature
We study a Bose-condensed gas at finite temperature, in which the particles
of the condensate and of the thermal cloud are constrained to move in a plane
under radial harmonic confinement and interact via strictly two-dimensional
collisions. The coupling parameters are obtained from a calculation of the
many-body T-matrix and decreases as temperature increases through a dependence
on the chemical potential and on the occupancy of excited states. We discuss
the consequences on the condensate fraction and on the density profiles of the
condensed and thermal components as functions of temperature, within a
simplified form of the two-fluid model.Comment: 12 pages, 4 figure
Feshbach resonance in a strictly two-dimensional atomic Bose gas
We discuss the atom-atom scattering problem across a Feshbach resonance in a
two-dimensional dilute Bose gas at zero temperature, in the limit where the
s-wave scattering length exceeds the width of the vertical confinement. We
determine a tunable coupling-strength parameter and by controlling it we
evaluate how the condensate wave function spreads out with increasing atom-atom
repulsions. We also discuss the stability of the condensate in the
magnetic-field regime where the coupling has become attractive.Comment: 9 pages, 1 figur
Fast Transition between High-soft and Low-soft States in GRS 1915+105: Evidence for a Critically Viscous Accretion Flow
We present the results of a detailed analysis of RXTE observations of class
which show an unusual state transition between high-soft and low-soft
states in the microquasar GRS 1915+105. Out of about 600 pointed RXTE
observations, the source was found to exhibit such state transition only on 16
occasions. An examination of the RXTE/ASM data in conjunction with the pointed
observations reveals that these events appeared as a series of quasi-regular
dips in two stretches of long duration (about 20 days during each occasions)
when hard X-ray and radio flux were very low. The X-ray light curve and
color-color diagram of the source during these observations are found to be
different from any reported so far. The duration of these dips is found to be
of the order of a few tens of seconds with a repetition time of a few hundred
seconds. The transition between these dips and non-dips which differ in
intensity by a factor of ~ 3.5, is observed to be very fast (~ a few seconds).
It is observed that the low-frequency narrow QPOs are absent in the power
density spectrum (PDS) of the dip and non-dip regions of class and the
PDS is a power law in 0.1 - 10 Hz frequency range. There is a remarkable
similarity in the spectral and timing properties of the source during the dip
and non-dip regions in these set of observations. These properties of the
source are distinctly different from those seen in the observations of other
classes. This indicates that the basic accretion disk structure during both dip
and non-dip regions of class is similar, but differ only in intensity.
To explain these observations, we invoke a model in which the viscosity is very
close to critical viscosity and the shock wave is weak or absent.Comment: Replaced with correct figures, Jour. of Astrophysics and Astronomy
(accepted
Coastal landslide monitoring at Aldbrough, East Riding of Yorkshire, UK.
The paper describes results to date of an ongoing monitoring study of coastal ‘soft cliff’ recession at the British Geological Survey (BGS)’s ‘Coastal Landslide Observatory’ (CLO) on the east coast of England at Aldbrough, East Riding of Yorkshire, UK. The cliffed site, part of the 50 km long Holderness coast, consists of glacial deposits, and is one of the most rapidly eroding coastlines in Europe. This rapid rate of erosion provides an ideal opportunity for observation and process understanding because it facilitates the collection of data over periods of time encompassing significant new landslide events at the same location. The results of two approaches are reported: firstly terrestrial LiDAR surveying (TLS) and secondly the installation of instrumented boreholes. The aim of the research is to combine these to investigate the role of landslides and their pre-conditioning factors and the influence of geology, geotechnics, topography and environmental factors on cliff recession. To date, an average recession rate of 1.8 m per year and a maximum rate of 3.4 m per year have been recorded for the site. The establishment of the CLO and its conceptual geological / geotechnical model are described in a related article (Hobbs et al. 2019a)
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