Browsing by Issue Date, starting with "2005-01"
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- Urine as a social signal in the Mozambique tilapia (Oreochromis mossambicus)Publication . Almeida, O. G.; Miranda, A.; Frade, P.; Hubbard, P. C.; Barata, E. N.; Canario, A.V.M.
- Up-regulated genes during in vitro mineralization of Sparus aurata osteoblast-like cellsPublication . Fonseca, Vera Alexandra Garcia; Cancela, Leonor; Laizé, VicentVertebrate bone formation involves numerous and complex mechanisms and despite many studies, essentially performed in mammals, most of them remain largely unclear. Few in vitro studies, all in mammalian systems, have identified various genes differentially expressed during mineralization but no data is available yet from lower vertebrates. In the present study, it was used the recently developed Sparus aurata osteoblast-like cell line VSa16 to construct a cDNA subtractive library (control vs. mineralizing conditions) aimed at the identification of genes associated with fish in vitro mineralization. Suppression Subtractive Hybridization (SSH) combined with Mirror Otientation Selection (MOS) identified 194 cDNA clones representing 20 different up-regulated osteoblast-related genes. Among them, four were related to calcium mechanisms: osteopontin-like (SaOP-like), S100-like (SaS100-like), mucin-like (SaMUC) and transgelin2 (SaTGL2). The full length cDNA of SaOP-like (2138 bp) and SaS100-like (8648 bp) was obtained by RACE-PCR. SaOP-like and SaS100-like relative gene expression was analysed in 1) larvae and juvenile fish representing different developmental stages, 2) a broad selection of adult tissues, and 3) cell lines derived from bone and cartilage recently developed in our laboratory. Op-like Was shown to be expressed essentially in calcified tissues and to be important for late stages of mineralization. In contrary, SIOO-like was ubiquitously expressed and found to be important at early stage of larval development. The role of the proteins encoded by these two genes in the process of mineralization is likely to be related to their capacity of binding calcium and hydroxyapatite cxystals.
- Mkp3 is a negative feedback modulator of Fgf8 signaling in the mammalian isthmic organizerPublication . Echevarria, D; Martinez, S; Marques, S; Lucas-Teixeira, V; Belo, JAThe pivotal mechanisms that govern the correct patterning and regionalization of the distinct areas of the mammalian CNS are driven by key molecules that emanate from the so-called secondary organizers at neural plate and tube stages. FGF8 is the candidate morphogenetic molecule to pattern the mesencephalon and rhombencephalon in the isthmic organizer (IsO). Recognizable relevance has been given to the intracellular pathways by which Fgf8 is regulated and modulated. In chick limb bud development, a dual mitogen-activated protein kinase phosphatase-3 (Mkp3) plays a role as a negative feedback modulator of Fgf8 signaling. We have investigated the role of Mkp3 and its functional relationship with the Fgf8 signaling pathway in the mouse IsO using gene transfer microelectroporation assays and protein-soaked bead experiments. Here, we demonstrate that MKP3 has a negative feedback action on the MAPK/ERK-mediated FGF8 pathway in the mouse neuroepithelium. (C) 2004 Elsevier Inc. All rights reserved.
- High-resolution permeability determination and two-dimensional porewater flow in sandy sedimentPublication . Rocha, C; Forster, S; Koning, E; Epping, EA new, inexpensive method is proposed to measure permeability in natural sandy sediment with high spatial resolution. This methodology allows for a reconstruction of the vertical permeability anisotropy in natural sediments, with a depth resolution of a few millimeters. Thus, the possible intrusion depth of advective flow over the water-sediment interface of sandy sediments can be deduced. Shipboard measurements on five natural sandy sediment cores taken from North Sea sediments are used to demonstrate that both the direction and magnitude of the second-order permeability tensor can be calculated from direct measurements using this method. This presents a major improvement over previous methods particularly in the context of quantifying flow and reaction in permeable sediments.
- Revisão de literatura sobre produtividade: evolução de conceitos e medidasPublication . Torres, Miguel MatosEste estudo tem por objectivo analisar a volução do conceito de produtividade e dos instrumentos utilizados para a sua medida. Nele se apresenta uma revisão de literatura, para a qual se realizou uma investigação aos contributos de autores que estudaram a rodutividade. Depois da introdução, identificam-se três fases nos estudos sobre produtividade. Na secção 2 apresenta-se uma revisão de literatura até aos anos 80 do século passado, período que corresponde ao entendimento dos conceitos de um ponto de vista normativo (o que deve ser). Na secção 3, investigam-se trabalhos publicados dos anos 80 e os dos anos 90 que anunciam o que é a produtividade. Na secção 4, descrevem-se os estudos mais recentes, dedicados à gestão da produtividade. Na conclusão releva-se algumas linhas de ligação entre as diferentes fases, assim como possíveis tendências de evolução futura.
- Philosophy of research in accounting and finance : a critical reflexionPublication . Peixinho, Rúben; Coelho, LuísExistent taxonomies in accounting and finance are based on different ontological and epistemological positions. We state that, despite the inexistence of a right perspective as well as a proper research method within these domains, a reflection about such issues is crucial for the development of high-quality research. Several reasons justify this reflection. On the one hand, it is well-established that the research process is dependent on researcher’s assumption about the nature of reality. On the other hand, the clear definition of researchers’ philosophical perspective facilitates the understanding of their work by the remaining academic community. This paper aims at clarifying some of these issues in the accounting and finance domains. The paper also presents a two-dimension map describing the main characteristics regarding two extreme philosophical perspectivesthat constitute the basis of several taxonomies in accounting and finance research.