14,411 research outputs found
Ras/Raf-1/MAPK pathway mediates response to tamoxifen but not chemotherapy in breast cancer patients
<b>Purpose</b>: The expression and activation of the Ras/Raf-1/mitogen-activated protein kinase (MAPK) pathway plays an important role in the development and progression of cancer, and may influence response to treatments such as tamoxifen and chemotherapy. In this study we investigated whether the expression and activation of the key components of this pathway influenced clinical outcome, to test the hypothesis that activation of the MAPK pathway drives resistance to tamoxifen and chemotherapy in women with breast cancer.
<b>Experimental Design</b>: Breast tumors from patients at the Glasgow Royal Infirmary and others treated within the BR9601 trial were analyzed for expression of the three Ras isoforms, total Raf-1, active and inactive forms of Raf-1 [pRaf(ser338) and pRaf(ser259), respectively], MAPK, and phospho-MAPK using an immunohistochemical approach. Analyses were done with respect to disease free-survival and overall survival.
<b>Results</b>: Expression and activation of the Ras pathway was associated with loss of benefit from treatment with tamoxifen but not chemotherapy. Overexpression of pRaf(ser338) was associated with shortened disease-free and overall survival time in univariate analyses. Multivariate analysis suggested pRaf(ser338) was independent of known prognostic markers in predicting outcome following tamoxifen treatment (<i>P</i>=0.03).
<b>Conclusion</b>: This study suggests that activation of the Ras pathway predicts for poor outcome on tamoxifen but not chemotherapy, and identifies pRaf(ser338) as a potential marker of resistance to estrogen receptor–targeted therapy. In addition, it suggests that expression of pRaf(ser338) could identify patients for whom tamoxifen alone is insufficient adjuvant systemic therapy, but for whom the addition of chemotherapy may be of benefit
A similarity-based approach to perceptual feature validation
Which object properties matter most in human perception may well vary according to sensory modality, an important consideration for the design of multimodal interfaces. In this study, we present a similarity-based method for comparing the perceptual importance of object properties across modalities and show how it can also be used to perceptually validate computational measures of object properties. Similarity measures for a set of three-dimensional (3D) objects varying in shape and texture were gathered from humans in two modalities (vision and touch) and derived from a set of standard 2D and 3D computational measures (image and mesh subtraction, object perimeter, curvature, Gabor jet filter responses, and the Visual Difference Predictor (VDP)). Multidimensional scaling (MDS) was then performed on the similarity data to recover configurations of the stimuli in 2D perceptual/computational spaces. These two dimensions corresponded to the two dimensions of variation in the stimulus set: shape and texture. In the human visual space, shape strongly dominated texture. In the human haptic space, shape and texture were weighted roughly equally. Weights varied considerably across subjects in the haptic experiment, indicating that different strategies were used. Maps derived from shape-dominated computational measures provided good fits to the human visual map. No single computational measure provided a satisfactory fit to the map derived from mean human haptic data, though good fits were found for individual subjects; a combination of measures with individually-adjusted weights may be required to model the human haptic similarity judgments. Our method provides a high-level approach to perceptual validation, which can be applied in both unimodal and multimodal interface design
Correlated X-ray and Optical Variability in Mkn 509
We present results of a 3 year monitoring campaign of the Seyfert 1 galaxy
Markarian 509, using X-ray data from the Rossi X-ray Timing Explorer (RXTE) and
optical data taken by the SMARTS consortium. Both light curves show significant
variations, and are strongly correlated with the optical flux leading the X-ray
flux by 15 days. The X-ray power spectrum shows a steep high-frequency slope of
-2.0, breaking to a slope of -1.0 at at timescale of 34 days. The lag from
optical to X-ray emission is most likely caused by variations in the accretion
disk propagating inward.Comment: 13 pages, 3 figures. Accepted for publication in the Astrophysical
Journa
Evaluation of a follow-up programme after curative resection for colorectal cancer
Frequent liver imaging can detect liver metastases from colorectal cancer at an asymptomatic stage. © 1999 Cancer Research Campaig
The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. II. Evidence for High Luminosity in Holmberg II ULX
This is the second of two papers examining Spitzer Infrared Spectrograph
(IRS) observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here
we perform detailed photoionization modeling of the infrared lines. Our
analysis suggests that the luminosity and morphology of the [O IV] 25.89 m
emission line is consistent with photoionization by the soft X-ray and far
ultraviolet (FUV) radiation from the accretion disk of the binary system and
inconsistent with narrow beaming. We show that the emission nebula is
matter-bounded both in the line of sight direction and to the east, and
probably radiation-bounded to the west. A bolometric luminosity in excess of
10 erg s would be needed to produce the measured [O IV] flux. We
use modeling and previously published studies to conclude that shocks likely
contribute very little, if at all, to the high-ionization line fluxes observed
in the Holmberg II ULX. Additionally, we find that the spectral type of the
companion star has a surprisingly strong effect on the predicted strength of
the [O IV] emission. This finding could explain the origin of [O IV] in some
starburst systems containing black hole binaries.Comment: Accepted by Ap
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Space charge behaviour in epoxy laminates under high constant electric field
The development of space charge in insulating materials is one of the main causes of their electrical ageing. The pulsed electro-acoustic method is often used to determine space charge distribution, but the signal analysis in the case of laminate structures is much more complex to analyse. In this paper the authors describe and use a simulated signal in order to study laminates made of epoxy resin and fibre mat. The relatively large conductivity of the fibres compared with that of the resin seems to produce a rapid charge dissociation and recombination in the fibres. Under voltage the presence of fibres close to an electrode seems to promote charge injection
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