1,071 research outputs found
Sortilin Is Upregulated in Osteoarthritis-Dependent Cartilage Calcification and Associated with Cellular Senescence.
Osteoarthritis (OA) is a chronic joint disease characterized by articular cartilage calcification, loss of articular cartilage, bone changes, pain, and disability. Cartilage calcification is one hallmark of OA and is predominantly caused by basic calcium crystals formed due to an imbalance of the pyrophosphate pathway. Sortilin is a transmembrane protein that contributes to vascular calcification in atherosclerosis by externalizing alkaline phosphatase (ALP)-containing vesicles. Calcification in atherosclerosis and osteoarthritis has been associated with cellular senescence. The aim of this study was to investigate the potential role of sortilin and senescence in osteoarthritis-dependent cartilage calcification. Osteoarthritic cartilage from human knee joints was collected after joint replacement, and samples were analyzed by immunohistochemistry and quantitative RT-PCR analysis. Human chondrocytes were treated with osteogenic medium for up to 21 days to induce calcification. Western blots for sortilin and ALP, as well as an ALP activity assay, were performed. Human chondrocytes were treated with mitomycin C to induce senescence, and sortilin expression was quantified at the protein and gene levels. Sections of knee joints from a murine model of osteoarthritis were stained for sortilin and p16 and analyzed by immunohistochemistry. Treatment of wild-type chondrocytes using an osteogenic medium similar to human chondrocytes was performed. Osteoarthritic cartilage from mouse and human knee joints showed an increased number of sortilin and p16-positive chondrocytes compared to healthy cartilage. This observation was corroborated by increased gene expression of sortilin and p16 in mild and moderate osteoarthritic cartilage samples. To investigate the mechanism of sortilin regulation, human chondrocytes were treated with osteogenic medium to induce calcification. Sortilin protein levels and expression were increased after 7 days of stimulation, whereas ALP levels and activity were upregulated after 21 days of stimulation. Similar observations were made in a murine osteoarthritis model. Mechanistically, senescent chondrocytes induced by mitomycin C showed an upregulation of sortilin and ALP gene expression compared to non-senescent chondrocytes. Our data indicate that sortilin and ALP are upregulated during cartilage calcification, which is associated with chondrocyte senescence and thus might contribute to the pathogenesis of osteoarthritis. Cellular senescence seems to induce sortilin expression
Visual orbit for the low-mass binary Gliese 22 AC from speckle interferometry
Based on 14 data points obtained with near-infrared speckle interferometry
and covering an almost entire revolution, we present a first visual orbit for
the low-mass binary system Gliese 22 AC. The quality of the orbit is largely
improved with respect to previous astrometric solutions. The dynamical system
mass is 0.592 +- 0.065 solar masses, where the largest part of the error is due
to the Hipparcos parallax. A comparison of this dynamical mass with
mass-luminosity relations on the lower main sequence and theoretical
evolutionary models for low-mass objects shows that both probably underestimate
the masses of M dwarfs. A mass estimate for the companion Gliese 22 C indicates
that this object is a very low-mass star with a mass close to the hydrogen
burning mass limit.Comment: Accepted by Astronomy and Astrophysics, 6 pages, 2 figure
Orbital motion in T Tauri binary systems
Using speckle-interferometry we have carried out repeated measurements of
relative positions for the components of 34 T Tauri binary systems. The
projected separation of these components is low enough that orbital motion is
expected to be observable within a few years. In most cases orbital motion has
indeed been detected. The observational data is discussed in a manner similar
to Ghez et al. (1995). However, we extend their study to a larger number of
objects and a much longer timespan. The database presented in this paper is
valuable for future visible orbit determinations. It will yield empirical
masses for T Tauri stars that now are only poorly known. The available data is
however not sufficient to do this at the present time. Instead, we use short
series of orbital data and statistical distributions of orbital parameters to
derive an average system mass that is independent of theoretical assumptions
about the physics of PMS stars. For our sample this mass is 2.0 solar masses
and thus in the order of magnitude one expects for the mass sum of two T Tauri
stars. It is also comparable to mass estimates obtained for the same systems
using theoretical PMS evolutionary models.Comment: Accepted by Astronomy and Astrophysic
A Search for Close Binaries in the Rho Ophiuchus Star-Forming Region
We have carried out a new, near-infrared speckle imaging survey of 19 members
of the young stellar population in the nearby (d=140 pc), Rho Ophiuchi cloud
core. Results for four binary and one newly discovered triple system are
reported. Data for all known multiple systems among the pre-main-sequence
population of Rho Oph are tabulated. We define a "restricted binary fraction",
Fbr, and a "restricted companion fraction", Fcr, as counting only those systems
most detectable in the present and previous high-resolution near-infrared
imaging surveys, having separations between 0.1-1.1 arcsec and K-band magnitude
differences, Delta K < 3. Analysis of all the available multiplicity data
results in updated values of Fbr=Fcr=24%+/-11% for the Ophiuchus
pre-main-sequence population. These values are consistent with the values in
the Taurus star-forming region, and Fcr is in excess by a factor of 2 relative
to the Main Sequence at the 1-sigma level.Comment: 21 pages, 6 figures, 4 table
Infrastructure for Detector Research and Development towards the International Linear Collider
The EUDET-project was launched to create an infrastructure for developing and
testing new and advanced detector technologies to be used at a future linear
collider. The aim was to make possible experimentation and analysis of data for
institutes, which otherwise could not be realized due to lack of resources. The
infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture
Mass ratios of the components in T Tauri binary systems and implications for multiple star formation
Using near-infrared speckle interferometry we have obtained resolved
JHK-photometry for the components of 58 young binary systems. From these
measurements, combined with other data taken from literature, we derive masses
and particularly mass ratios of the components. We use the J-magnitude as an
indicator for the stellar luminosity and assign the optical spectral type of
the system to the primary. On the assumption that the components within a
binary are coeval we can then place also the secondaries into the HRD and
derive masses and mass ratios for both components by comparison with different
sets of current theoretical pre-main sequence evolutionary tracks. The
resulting distribution of mass ratios is comparatively flat for M(2)/M(1) >
0.2, but depends on assumed evolutionary tracks. The mass ratio is neither
correlated with the primary's mass or the components' separation. These
findings are in line with the assumption that for most multiple systems in T
associations the components' masses are principally determined by fragmentation
during formation and not by the following accretion processes. Only very few
unusually red objects were newly found among the detected companions. This
finding shows that the observed overabundance of binaries in the Taurus-Auriga
association compared to nearby main sequence stars should be real and not the
outcome of observational biases related to infrared observing.Comment: accepted by Astronomy and Astrophysics, contains extensive tables and
figures that will only be published electronically at CDS (in total: 34
pages, 11 figures
Long-term (trophic) purinergic signalling: purinoceptors control cell proliferation, differentiation and death
The purinergic signalling system, which uses purines and pyrimidines as chemical transmitters, and purinoceptors as effectors, is deeply rooted in evolution and development and is a pivotal factor in cell communication. The ATP and its derivatives function as a 'danger signal' in the most primitive forms of life. Purinoceptors are extraordinarily widely distributed in all cell types and tissues and they are involved in the regulation of an even more extraordinary number of biological processes. In addition to fast purinergic signalling in neurotransmission, neuromodulation and secretion, there is long-term (trophic) purinergic signalling involving cell proliferation, differentiation, motility and death in the development and regeneration of most systems of the body. In this article, we focus on the latter in the immune/defence system, in stratified epithelia in visceral organs and skin, embryological development, bone formation and resorption, as well as in cancer. Cell Death and Disease (2010) 1, e9; doi:10.1038/cddis.2009.11; published online 14 January 201
Motherhood in childhood: addressing reproductive health hazards among adolescent married women in India
Quantification of growth factors in allogenic bone grafts extracted with three different methods
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