48 research outputs found
The Fundamental Plane for cluster E and S0 galaxies
We have analyzed the Fundamental Plane (FP) for a sample of 226 E and S0
galaxies in ten clusters of galaxies. For photometry in Gunn r the best fitting
plane is log r_e=1.24 log sigma - 0.82 log _e + cst. The scatter is 0.084 in
log r_e. The slope of the FP is not significantly different from cluster to
cluster. The residuals of the FP correlate weakly with the velocity dispersion
and the surface brightness. Thus, to avoid biases of derived distances the
galaxies need to be selected in a homogeneous way. The FP has significant
intrinsic scatter. No other structural parameters like ellipticity or isophotal
shape can reduce the scatter significantly. The Mg_2-sigma relation differs
slightly from cluster to cluster. Galaxies in clusters with lower velocity
dispersions have systematically lower Mg_2. With the current stellar population
models, it is in best agreement with our results regarding the FP if the
offsets are mainly caused by differences in metallicity. Most of the distances
that we derive from the FP imply small peculiar motions, <1000km/s. The zero
point of the FP must therefore be quite stable. The residuals from the
Mg_2-sigma relation may be used to flag galaxies with deviant populations, and
possibly to correct the distance determinations for the deviations.Comment: 20 pages, gzipped PostScript, 14 figures included. Accepted for
publication in MNRA
Evolution of Galaxy morphologies in Clusters
We have studied the evolution of galaxian morphologies from ground-based,
good-seeing images of 9 clusters at z=0.09-0.25. The comparison of our data
with those relative to higher redshift clusters (Dressler et al. 1997) allowed
us to trace for the first time the evolution of the morphological mix at a
look-back time of 2-4 Gyr, finding a dependence of the observed evolutionary
trends on the cluster properties.Comment: 4 pages with 2 figures in Latex-Kluwer style. To be published in the
proceedings of the Granada Euroconference "The Evolution of
Galaxies.I-Observational Clues
Surface photometry of WINGS galaxies with GASPHOT
Aims. We present the B-, V- and K-band surface photometry catalogs obtained
running the automatic software GASPHOT on galaxies from the WINGS cluster
survey having isophotal area larger than 200 pixels. The catalogs can be
downloaded at the Centre de Donnees Astronomiques de Strasbourg (CDS). Methods.
We outline the GASPHOT performances and compare our surface photometry with
that obtained by SExtractor, GALFIT and GIM2D. This analysis is aimed at
providing statistical information about the accuracy generally achieved by the
softwares for automatic surface photometry of galaxies. Results. For each
galaxy and for each photometric band the GASPHOT catalogs provide the
parameters of the Sersic law best-fitting the luminosity profiles. They are:
the sky coordinates of the galaxy center (R:A:; DEC:), the total magnitude (m),
the semi-major axis of the effective isophote (Re), the Sersic index (n), the
axis ratio (b=a) and a flag parameter (QFLAG) giving a global indication of the
fit quality. The WINGS-GASPHOT database includes 41,463 galaxies in the B-band,
42,275 in the V-band, and 71,687 in the K-band. We find that the bright
early-type galaxies have larger Sersic indices and effective radii, as well as
redder colors in their center. In general the effective radii increase
systematically from the K- to the V- and B-band. Conclusions. The GASPHOT
photometry turns out to be in fairly good agreement with the surface photometry
obtained by GALFIT and GIM2D, as well as with the aperture photometry provided
by SExtractor. The main advantages of GASPHOT with respect to other tools are:
(i) the automatic finding of the local PSF; (ii) the short CPU time of
execution; (iii) the remarkable stability against the choice of the initial
guess parameters. All these characteristics make GASPHOT an ideal tool for
blind surface photometry of large galaxy samples in wide-field CCD mosaics.Comment: 14 pages, 9 figure
Isosteviol Has Beneficial Effects on Palmitate-Induced α-Cell Dysfunction and Gene Expression
BACKGROUND: Long-term exposure to high levels of fatty acids impairs insulin secretion and exaggerates glucagon secretion. The aim of this study was to explore if the antihyperglycemic agent, Isosteviol (ISV), is able to counteract palmitate-induced α-cell dysfunction and to influence α-cell gene expression. METHODOLOGY/PRINCIPAL FINDINGS: Long-term incubation studies with clonal α-TC1-6 cells were performed in the presence of 0.5 mM palmitate with or without ISV. We investigated effects on glucagon secretion, glucagon content, cellular triglyceride (TG) content, cell proliferation, and expression of genes involved in controlling glucagon synthesis, fatty acid metabolism, and insulin signal transduction. Furthermore, we studied effects of ISV on palmitate-induced glucagon secretion from isolated mouse islets. Culturing α-cells for 72-h with 0.5 mM palmitate in the presence of 18 mM glucose resulted in a 56% (p<0.01) increase in glucagon secretion. Concomitantly, the TG content of α-cells increased by 78% (p<0.01) and cell proliferation decreased by 19% (p<0.05). At 18 mM glucose, ISV (10(-8) and 10(-6) M) reduced palmitate-stimulated glucagon release by 27% (p<0.05) and 27% (p<0.05), respectively. ISV (10(-6) M) also counteracted the palmitate-induced hypersecretion of glucagon in mouse islets. ISV (10(-6) M) reduced α-TC1-6 cell proliferation rate by 25% (p<0.05), but ISV (10(-8) and 10(-6) M) had no effect on TG content in the presence of palmitate. Palmitate (0.5 mM) increased Pcsk2 (p<0.001), Irs2 (p<0.001), Fasn (p<0.001), Srebf2 (p<0.001), Acaca (p<0.01), Pax6 (p<0.05) and Gcg mRNA expression (p<0.05). ISV significantly (p<0.05) up-regulated Insr, Irs1, Irs2, Pik3r1 and Akt1 gene expression in the presence of palmitate. CONCLUSIONS/SIGNIFICANCE: ISV counteracts α-cell hypersecretion and apparently contributes to changes in expression of key genes resulting from long-term exposure to palmitate. ISV apparently acts as a glucagonostatic drug with potential as a new anti-diabetic drug for the treatment of type 2 diabetes
Matrix Metalloproteinases in Cytotoxic Lymphocytes Impact on Tumour Infiltration and Immunomodulation
To efficiently combat solid tumours, endogenously or adoptively transferred cytotoxic T cells and natural killer (NK) cells, need to leave the vasculature, traverse the interstitium and ultimately infiltrate the tumour mass. During this locomotion and migration in the three dimensional environment many obstacles need to be overcome, one of which is the possible impediment of the extracellular matrix. The first and obvious one is the sub-endothelial basement membrane but the infiltrating cells will also meet other, both loose and tight, matrix structures that need to be overridden. Matrix metalloproteinases (MMPs) are believed to be one of the most important endoprotease families, with more than 25 members, which together have function on all known matrix components. This review summarizes what is known on synthesis, expression patterns and regulation of MMPs in cytotoxic lymphocytes and their possible role in the process of tumour infiltration. We also discuss different functions of MMPs as well as the possible use of other lymphocyte proteases for matrix degradation
Prediction of second neurological attack in patients with clinically isolated syndrome using support vector machines
The aim of this study is to predict the conversion from clinically isolated syndrome to clinically definite multiple sclerosis using support vector machines. The two groups of converters and non-converters are classified using features that were calculated from baseline data of 73 patients. The data consists of standard magnetic resonance images, binary lesion masks, and clinical and demographic information. 15 features were calculated and all combinations of them were iteratively tested for their predictive capacity using polynomial kernels and radial basis functions with leave-one-out cross-validation. The accuracy of this prediction is up to 86.4% with a sensitivity and specificity in the same range indicating that this is a feasible approach for the prediction of a second clinical attack in patients with clinically isolated syndromes, and that the chosen features are appropriate. The two features gender and location of onset lesions have been used in all feature combinations leading to a high accuracy suggesting that they are highly predictive. However, it is necessary to add supporting features to maximise the accuracy. © 2013 IEEE
Helical Propensity in an Intrinsically Disordered Protein Accelerates Ligand Binding
Many intrinsically disordered proteins fold upon binding to other macromolecules. The secondary structure present in the well-ordered complex is often formed transiently in the unbound state. The consequence of such transient structure for the binding process is, however, not clear. The activation domain of the activator for thyroid hormone and retinoid receptors (ACTR) is intrinsically disordered and folds upon binding to the nuclear coactivator binding domain (NCBD) of the CREB binding protein. A number of mutants was designed that selectively perturbs the amount of secondary structure in unbound ACTR without interfering with the intermolecular interactions between ACTR and NCBD. Using NMR spectroscopy and fluorescence-monitored stopped-flow kinetic measurements we show that the secondary structure content in helix1 of ACTR indeed influences the binding kinetics. The results thus support the notion of preformed secondary structure as an important determinant for molecular recognition in intrinsically disordered proteins.De två första författarna delar första författarskapet.</p