Browsing by Issue Date, starting with "1998-09"
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- A model for signal transduction during gamete release in the fucoid alga Pelvetia compressaPublication . Pearson, Gareth; Brawley, S. H.Fucoid algae release gametes into-seawater following an inductive light period (potentiation), and gamete expulsion from potentiated receptacles of Pelvetia compressa began about 2 min after a light-to-dark transition. Agitation of the medium reversed potentiation, with an exponential time course completed in about 3 h. Light regulated two signaling pathways during potentiation and gamete expulsion: a photosynthetic pathway and a photosynthesis-independent pathway in which red light was active but blue light was not. Uptake of K+ appears to have an important role in potentiation, because a 50% inhibition of potentiation occurred in the presence of the tetraethylammonium ion, a K+-channel blocker. A central role of anion channels in the maintenance of potentiation is suggested by the premature release of gametes in the light when receptacles were incubated with inhibitors of slow-type anion channels. An inhibitor of tyrosine kinases, tyrphostin A63, also inhibited potentiation. A model for gamete release from P. compressa is presented that proposes that illumination results in the accumulation of ions (e.g. K+) throughout the cells of the receptacle during potentiation, which then move into the extracellular matrix during gamete expulsion to generate osmomechanical force, resulting in gamete release.
- Apoio ao planeamento de viagens em transportes públicosPublication . Correia, Marisol B.; Mamede, NunoApresenta-se um sistema informático que elabora planos de viagens para pessoas utilizando transportes públicos e que escolhe os melhores de entre esses planos, em função dos critérios indicados pelo utilizador, como sejam, o tempo de duração da viagem, o preço dos bilhetes e a qualidade dos transportes.