University of Lisbon

About: University of Lisbon is a education organization based out in Lisbon, Lisboa, Portugal. It is known for research contribution in the topics: Population & Context (language use). The organization has 19122 authors who have published 48503 publications receiving 1102623 citations. The organization is also known as: Universidade de Lisboa & Lisbon University.

A gene-expression signature to predict survival in breast cancer across independent data sets

Abstract: Prognostic signatures in breast cancer derived from microarray expression profiling have been reported by two independent groups. These signatures, however, have not been validated in external studies, making clinical application problematic. We performed microarray expression profiling of 135 early-stage tumors, from a cohort representative of the demographics of breast cancer. Using a recently proposed semisupervised method, we identified a prognostic signature of 70 genes that significantly correlated with survival (hazard ratio (HR): 5.97, 95% confidence interval: 3.0-11.9, P = 2.7e-07). In multivariate analysis, the signature performed independently of other standard prognostic classifiers such as the Nottingham Prognostic Index and the 'Adjuvant!' software. Using two different prognostic classification schemes and measures, nearest centroid (HR) and risk ordering (D-index), the 70-gene classifier was also found to be prognostic in two independent external data sets. Overall, the 70-gene set was prognostic in our study and the two external studies which collectively include 715 patients. In contrast, we found that the two previously described prognostic gene sets performed less optimally in external validation. Finally, a common prognostic module of 29 genes that associated with survival in both our cohort and the two external data sets was identified. In spite of these results, further studies that profile larger cohorts using a single microarray platform, will be needed before prospective clinical use of molecular classifiers can be contemplated.

Discovery of a magma chamber and faults beneath a Mid-Atlantic Ridge hydrothermal field

Abstract: Crust at slow-spreading ridges is formed by a combination of magmatic and tectonic processes, with magmatic accretion possibly involving short-lived crustal magma chambers The reflections of seismic waves from crustal magma chambers have been observed beneath intermediate and fast-spreading centres, but it has been difficult to image such magma chambers beneath slow-spreading centres, owing to rough seafloor topography and associated seafloor scattering In the absence of any images of magma chambers or of subsurface near-axis faults, it has been difficult to characterize the interplay of magmatic and tectonic processes in crustal accretion and hydrothermal circulation at slow-spreading ridges Here we report the presence of a crustal magma chamber beneath the slow-spreading Lucky Strike segment of the Mid-Atlantic Ridge The reflection from the top of the magma chamber, centred beneath the Lucky Strike volcano and hydrothermal field, is approximately 3 km beneath the sea floor, 3-4 km wide and extends up to 7 km along-axis We suggest that this magma chamber provides the heat for the active hydrothermal vent field above it We also observe axial valley bounding faults that seem to penetrate down to the magma chamber depth as well as a set of inward-dipping faults cutting through the volcanic edifice, suggesting continuous interactions between tectonic and magmatic processes

Dynamic association of RNA-editing enzymes with the nucleolus

Abstract: ADAR1 and ADAR2 are editing enzymes that deaminate adenosine to inosine in long double stranded RNA duplexes and specific pre-mRNA transcripts. Here, we show that full-length and N-terminally truncated forms of ADAR1 are simultaneously expressed in HeLa and COS7 cells owing to the usage of alternative starting methionines. Because the N-terminus of ADAR1 contains a nuclear export signal, the full-length protein localizes predominantly in the cytoplasm, whereas the N-terminally truncated forms are exclusively nuclear and accumulate in the nucleolus. ADAR2, which lacks a region homologous to the N-terminal domain of ADAR1, localizes exclusively to the nucleus and similarly accumulates in the nucleolus. Within the nucleolus, ADAR1 and ADAR2 co-localize in a novel compartment. Photobleaching experiments demonstrate that, in live cells, ADAR1 and ADAR2 are in constant flux in and out of the nucleolus. When cells express the editing-competent glutamate receptor GluR-B RNA, endogenous ADAR1 and ADAR2 de-localize from the nucleolus and accumulate at sites where the substrate transcripts accumulate. This suggests that ADAR1 and ADAR2 are constantly moving through the nucleolus and might be recruited onto specific editing substrates present elsewhere in the cell.

Spectroscopic metallicities for planet-host stars: Extending the samples

Abstract: We present stellar parameters and metallicities for 29 planet-host stars, as well as for a large volume-limited sample of 53 stars not known to be orbited by any planetary-mass companion. These stars add to the results presented in our previous series of papers, providing two large and uniform samples of 119 planet-hosts and 94 “single” stars with accurate stellar parameters and [Fe/H] estimates. The analysis of the results further confirms that stars with planets are metal-rich when compared with average field dwarfs. Important biases that may compromise future studies are also discussed. Finally, we compare the metallicity distributions for single planet-hosts and planet-hosts in multiple stellar systems. The results show that a small difference cannot be excluded, in the sense that the latter sample is slighly overmetallic. However, more data are needed to confirm this correlation.