1,231 research outputs found
Precessing jets from a moving source and bright X-ray filaments in galaxy clusters
We present hydrodynamical calculations carried out with the 3D yguazu-a code
of a precessing jet model, which interacts with a plane parallel wind. This
scenario describes an extragalactic jet, in which the jet source is in motion
with respect to the surrounding intra-cluster medium. From the numerical
results, synthetic emission maps and spectra in X-ray band were obtained. We
compare these predictions with observations of the radio jets emanating from
the radio-galaxy 4C 26.42 (in the Abell 1795 galaxy cluster). We find that the
general morphology of the radio jets can be described by a point-symmetric
precessing jet system interacting with a plane parallel wind (i.e., the
intra-cluster medium flowing past the galaxy). We also find that our synthetic
X-ray emission maps reproduce the observed large scale structures (with sizes
of the order of tens of kpc).Comment: Accepted for publication in A&A - 7 Pages, 6 figure
The giant H-alpha/X-ray filament in the cluster of galaxies A1795
The cluster of galaxies A1795 hosts a 46 kpc-long filament at its core, which
is clearly visible in the light of H-alpha and X-ray emission. We present
optical slit spectroscopy and deeper Chandra X-ray data of the filament. The
optical spectra reveal that the the bulk of the filament is quiescent (with
sigma < 130 km/s), although considerable velocity structure is apparent around
the powerful radio source in the central cluster galaxy, where a direct
interaction is occurring between the radio plasma and the surrounding
intracluster medium. The filament contains a clump of UV/blue continuum halfway
along its length, which we resolve into a chain of at least 5 distinct knots
using archival HST images; the optical spectrum of this clump confirm it to be
mostly comprised of O stars. It is well-removed from the central galaxy and
radio source, and is most likely an example of a group of young star clusters
condensing directly from the cooling gas in the filament. The observed spatial
offset between these knots of star formation and the peak in the optical line
emission confirms that the massive star formation is most unlikely to be
responsible for the bulk of the observed emission-line luminosity in the
filament. Some other (as yet undetermined) source of energy is required to
power and maintain the optical line-emission, yet it must not completely impede
the cooling of the X-ray gas within the filament to form the star clusters.Comment: 21 pages 14 figures; full resolution copy of paper available at
http://www-xray.ast.cam.ac.uk/~csc/a1795.htm
Emission-Line Properties of the Optical Filaments of NGC 1275
Extended nebular filaments are seen at optical wavelengths in NGC 1275, the
central galaxy in the Perseus cluster. The agents responsible for the
excitation of these filaments remain poorly understood. In this paper we
investigate possible mechanisms for powering the filaments, using measurements
from an extensive spectroscopic data set acquired at the Lick Observatory 3-m
Shane telescope. The results show that the filaments are in an extremely low
ionization and excitation state. The high signal-to-noise ratio of the spectra
allows us to measure or place sensitive upper limits on weak but important
diagnostic lines. We compare the observed line intensity ratios to the
predictions of various ionization models, including photoionization by an
active galactic nucleus, shock heating, stellar photoionization, and
photoionization by the intracluster medium. We also investigate possible roles
for cluster extreme-ultraviolet emission, and filtering of cluster soft X-ray
emission by an ionized screen, in the energetics of the filaments. None of
these mechanisms provides an entirely satisfactory explanation for the physical
state of the nebulae. Heating and ionization by reconnection of the
intracluster magnetic field remains a potentially viable alternative, which
merits further investigation through Faraday rotation studies.Comment: Accepted for publication in Ap
Injectable gellan gum hydrogels with autologous cells for the treatment of rabbit articular cartilage defects
In this work, the ability of gellan gum hydrogels coupled with autologous cells to regenerate rabbit full-thickness articular
cartilage defects was tested. Five study groups were defined: (a) gellangumwith encapsulated chondrogenic predifferentiated rabbit adipose
stem cells (ASCþGF); (b) gellan gum with encapsulated nonchondrogenic predifferentiated rabbit adipose stem cells (ASC); (c) gellan gum
with encapsulated rabbit articular chondrocytes (AC) (standard control); (d) gellan gum alone (control); (e) empty defect (control). Fullthickness
articular cartilage defects were created and the gellangum constructs were injected and left for 8 weeks. The macroscopic aspect of
the explants showed a progressive increase of similarity with the lateral native cartilage, stable integration at the defect site, more
pronouncedly in the cell-loaded constructs. Tissue scoring showed that ASCþGF exhibited the best results regarding tissue quality
progression. Alcian blue retrieved similar results with a better outcome for the cell-loaded constructs. Regarding real-time PCR analyses,
ASCþGF had the best progression with an upregulation of collagen type II and aggrecan, and a downregulation of collagen type I. Gellan
gum hydrogels combined with autologous cells constitute a promising approach for the treatment of articular cartilage defects, and adipose
derived cellsmayconstitute a valid alternative to currently used articular chondrocytes.J. T. Oliveira acknowledge the Portuguese Foundation for Science and Technology (FCT) for his grant (SFRH/BD17135/2004). The authors thank the medical and technical staff of the Institute for Biomedical Sciences Abel Salazar (ICBAS) of the University of Porto, Portugal and the Institute for Health and Life Sciences (ICVS) of the University of Minho, Portugal. The authors also thank Dr. Patricia Malafaya, Cristina Correia, and Rui Pereira, for their help with the histological scoring. This work was carried out under the scope of the European NoE EXPERTISSUES, and partially supported by the European Project HIPPOCRATES
Influenza nucleoprotein delivered with aluminium salts protects mice from an influenza virus that expresses an altered nucleoprotein sequence
Influenza virus poses a difficult challenge for protective immunity. This virus is adept at altering its surface proteins, the proteins that are the targets of neutralizing antibody. Consequently, each year a new vaccine must be developed to combat the current recirculating strains. A universal influenza vaccine that primes specific memory cells that recognise conserved parts of the virus could prove to be effective against both annual influenza variants and newly emergent potentially pandemic strains. Such a vaccine will have to contain a safe and effective adjuvant that can be used in individuals of all ages. We examine protection from viral challenge in mice vaccinated with the nucleoprotein from the PR8 strain of influenza A, a protein that is highly conserved across viral subtypes. Vaccination with nucleoprotein delivered with a universally used and safe adjuvant, composed of insoluble aluminium salts, provides protection against viruses that either express the same or an altered version of nucleoprotein. This protection correlated with the presence of nucleoprotein specific CD8 T cells in the lungs of infected animals at early time points after infection. In contrast, immunization with NP delivered with alum and the detoxified LPS adjuvant, monophosphoryl lipid A, provided some protection to the homologous viral strain but no protection against infection by influenza expressing a variant nucleoprotein. Together, these data point towards a vaccine solution for all influenza A subtypes
In vitro comparison of the effects of rough and polished stem surface finish on pressure generation in cemented hip arthroplasty
Background and purpose High pressures around implants can cause bone lysis and loosening. We investigated how pressures are generated around cemented femoral stems
Performance of new gellan gum hydrogels combined with human articular chondrocytes for cartilage regeneration when subcutaneously implanted in nude mice
Gellan gum is a polysaccharide that has been recently proposed by our group for cartilage tissueengineering
applications. It is commonly used in the food and pharmaceutical industry and has
the ability to form stable gels without the use of harsh reagents. Gellan gum can function as a
minimally invasive injectable system, gelling inside the body in situ under physiological conditions
and efficiently adapting to the defect site. In this work, gellan gum hydrogels were combined with
human articular chondrocytes (hACs) and were subcutaneously implanted in nude mice for 4 weeks.
The implants were collected for histological (haematoxylin and eosin and Alcian blue staining),
biochemical [dimethylmethylene blue (GAG) assay], molecular (real-time PCR analyses for collagen
types I, II and X, aggrecan) and immunological analyses (immunolocalization of collagen types I and
II). The results showed a homogeneous cell distribution and the typical round-shaped morphology
of the chondrocytes within the matrix upon implantation. Proteoglycans synthesis was detected by
Alcian blue staining and a statistically significant increase of proteoglycans content was measured
with the GAG assay quantified from 1 to 4 weeks of implantation. Real-time PCR analyses showed a
statistically significant upregulation of collagen type II and aggrecan levels in the same periods. The
immunological assays suggest deposition of collagen type II along with some collagen type I. The
overall data shows that gellan gum hydrogels adequately support the growth and ECM deposition
of human articular chondrocytes when implanted subcutaneously in nude mice.J. T. Oliveira would like to acknowledge the Portuguese Foundation for Science and Technology (FCT) for his grant (SFP,H/BD17135/2004). The authors would like to thank the patients at Hospital de S. Marcos, Braga, Portugal, for the donation of the biological samples and the medical staff for their help and support. The authors would also like to thank the Institute for Health and Life Sciences (ICVS), University of Minho, Braga, Portugal, for allowing the use of their research facilities. This work was carried out under the scope of European NoE EXPERTISSUES (Project No. NMP3-CT-2004-500283) and partially supported by the European Project HIPPOCRATES (No. STRP 505758-1)
Tumour necrosis factor gene polymorphism: a predictive factor for the development of post-transplant lymphoproliferative disease
Epstein–Barr virus-positive post-transplant lymphoproliferative disease (PTLD) is a potentially lethal complication of iatrogenic immunosupression after transplantation. Predicting the development of PTLD allowing early and effective intervention is therefore of importance. Polymorphisms within cytokine genes are implicated in susceptibility to, and progression of, disease however the published data are often conflicting. We undertook investigation of polymorphic alleles within cytokine genes in PTLD and non-PTLD transplant cohorts to determine risk factors for disease.
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Methods:
SSP-PCR was used to analyse single nucleotide polymorphism within tumour necrosis factor (TNF)-α, interleukin- 1, -6, -10 and lymphotoxin-α genes. The TNF-α levels were measured by standard enzyme-linked immuno-absorbant assay.
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Results:
We show an association between variant alleles within the TNF-α promoter (−1031C (<i>P</i>=0.005)); −863A (<i>P</i>=0.0001) and TNF receptor I promoter regions (−201T (<i>P</i>=0.02)); −1135C (<i>P</i>=0.03) with the development of PTLD. We also show an association with TNF-α promoter haplotypes with haplotype-3 significantly increased (<i>P</i>=0.0001) and haplotype-1 decreased (P=0.02) in PTLD patients compared to transplant controls. Furthermore, we show a significant increase (<i>P</i>=0.02) in the level of TNF-α in PTLD patient plasma (range 0–97.97 pg ml<sup>−1</sup>) compared to transplant controls (0–8.147 pg ml<sup>−1</sup>), with the highest levels found in individuals carrying the variant alleles.
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Conclusion:
We suggest that genetic variation within TNF-α loci and the level of plasma cytokine could be used as a predictive risk factor for the development of PTLD
Parsec-scale Properties of Brightest Cluster Galaxies
We present new VLBI observations at 5 GHz of a complete sample of Brightest
Cluster Galaxies (BCGs) in nearby Abell Clusters (distance class <3). Combined
with data from the literature, this provides parsec-scale information for 34
BCGs. Our analysis of their parsec scale radio emission and cluster X-ray
properties shows a possible dichotomy between BCGs in cool core clusters and
those in non cool core clusters. Among resolved sources, those in cool core
clusters tend to have two-sided parsec-scale jets, while those in less relaxed
clusters have predominantly one-sided parsec-scale jets. We suggest that this
difference could be the result of interplay between the jets and the
surrounding medium. The one-sided structure in non cool core clusters could be
due to Doppler boosting effects in relativistic, intrinsically symmetric jets;
two-sided morphology in cool core clusters is likely related to the presence of
heavy and mildly relativistic jets slowed down on the parsec-scale. Evidence of
recurrent activity are also found in BCGs in cool core clusters.Comment: 20 pages, 10 figures, accepted for publication in A&
KDM6A Regulates Cell Plasticity and Pancreatic Cancer Progression by Non-Canonical Activin Pathway
BACKGROUND & AIMS: Inactivating mutations of KDM6A, a histone demethylase, were frequently found in pancreatic ductal adenocarcinoma (PDAC). We investigated the role of KDM6A in PDAC development.
METHODS: We performed a pancreatic tissue microarray analysis of KDM6A protein levels. We used human PDAC cell lines for KDM6A knockout and knockdown experiments. We performed Bru-seq analysis to elucidate the effects of KDM6A loss on global transcription. We performed studies with Ptf1a(Cre); LSL-Kras(G12D); Trp53(R172H/+); Kdm6a(fl/fl or fl/Y), Ptf1a(Cre); Kdm6a(fl/fl or fl/Y), and orthotopic xenograft mice to investigate the impacts of Kdm6a deficiency on pancreatic tumorigenesis and pancreatitis.
RESULTS: Loss of KDM6A was associated with metastasis in PDAC patients. Bru-seq analysis revealed upregulation of the epithelial-mesenchymal transition pathway in PDAC cells deficient of KDM6A. Loss of KDM6A promoted mesenchymal morphology, migration, and invasion in PDAC cells in vitro. Mechanistically, activin A and subsequent p38 activation likely mediated the role of KDM6A loss. Inhibiting either activin A or p38 reversed the effect. Pancreas-specific Kdm6a-knockout mice pancreata demonstrated accelerated PDAC progression, developed a more aggressive undifferentiated type PDAC, and increased metastases in the background of Kras and p53 mutations. Kdm6a-deficient pancreata in a pancreatitis model had a delayed recovery with increased PDAC precursor lesions compared to wild-type pancreata.
CONCLUSIONS: Loss of KDM6A accelerates PDAC progression and metastasis, most likely by a non-canonical p38-dependant activin A pathway. KDM6A also promotes pancreatic tissue recovery from pancreatitis. Activin A might be utilized as a therapeutic target for KDM6A-deficient PDACs
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