Classe de Ciências

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Functional purification of the monocarboxylate transporter of the yeast Candida utilis

Plasma membranes of the yeast, Candida utilis, were solubilized with octyl-b-D- lucopyranoside and a fraction enriched in the lactate carrier was obtained with DEAE-Sepharose anion- exchange chromatography, after elution with 0.4 M NaCl. The uptake of lactic acid into proteoliposomes, containing the purified protein fraction and cytochrome c oxidase, was dependent on a proton-motive force and the transport specificity was consistent with the one of C. utilis intact cells. Overall, we have obtained a plasma membrane fraction enriched in the lactate carrier of C. utilis in which the transport properties were preserved. Given the similarities between the lactate transport of C. utilis and the one of mammalian cells, this purified system could be further explored to screen for specific lactate inhibitors, with potential therapeutic applications

Ética e Edição do Genoma

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O reconhecimento da Universidade

Em nome da Universidade do Minho e também em meu nome pessoal a todos saudo e endereço os meus gratos cumprimentos.Começo por agradecer à Organização desta cerimónia que, através do nosso muito querido Prof. Lúcio Craveiro, Presidente do Conselho Cultural, com toda a gentileza que todos lhe reconhecem, me convidou a participar nesta mesa, em substituição do Magnífico Reitor que não pode estar aqui presente

Classe de Ciências

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Uma perspetiva da cultura integrada na formação de futuros médicos

A cultura é um dos pilares e um dos bens mais sublimes de qualquer sociedade. Ela está na base das nossas raízes, introduzindo-nos no universo da humanidade, e é através dela que vamos construindo a nossa individualidade, autonomia e personalidade. Os nossos comportamentos são aqui fundamentais, e hoje, porventura mais do que nunca, o progresso da humanidade está intimamente associado à “emergência da cultura na sociedade”

Freeze tolerance of the yeast Torulaspora delbrueckii : cellular and biochemical basis

The freeze-stress responses to prolonged storage at - 20 °C in Torulaspora delbrueckii PYCC5323 were investigated. In this yeast no loss of cell viability was observed for at least 120 days during freezing at - 20ºC, whereas a loss of 80% was observed in a commercial baker's yeast after 15 days. In the former strain, freeze resistance was dependent on an adaptation process. The primary cell target of freeze stress was the plasma membrane, preservation of it’s integrity being related with a lower increase of lipid peroxidation and with higher resistance to H2O2, but not with intracellular trehalose concentration.Fundação para a Ciência e a Tecnologia (FCT) - grant (PRAXIS XXI/BD/21543/99)

Growth culture conditions and nutrient signaling modulating yeast chronological longevity

The manipulation of nutrient-signaling pathways in yeast has uncovered the impact of environmental growth conditions in longevity. Studies using calorie restriction show that reducing glucose concentration of the culture media is sufficient to increase replicative and chronological lifespan (CLS). Other components of the culture media and factors such as the products of fermentation have also been implicated in the regulation of CLS. Acidification of the culture media mainly due to acetic acid and other organic acids production negatively impacts CLS. Ethanol is another fermentative metabolite capable of inducing CLS reduction in aged cells by yet unknown mechanisms. Recently, ammonium was reported to induce cell death associated with shortening of CLS. This effect is correlated to the concentration of added to the culture medium and is particularly evident in cells starved for auxotrophy-complementing amino acids. Studies on the nutrient-signaling pathways regulating yeast aging had a significant impact on aging-related research, providing key insights into mechanisms that modulate aging and establishing the yeast as a powerful system to extend knowledge on longevity regulation in multicellular organisms.This work was supported by Fundação para a Ciência e Tecnologia (FCT), Portugal Grant PTDC/AGR-ALI/102608/2008. J. Santos received a fellowship from FCT (SFRH/BD/33314/2008)

Ammonium-dependent shortening of CLS in yeast cells starved for essential amino acids is determined by the specific amino acid deprived, through different signaling pathways

Ammonium (NH4(+)) leads to chronological life span (CLS) shortening in Saccharomyces cerevisiae BY4742 cells, particularly evident in cells starved for auxotrophy-complementing amino acids (leucine, lysine, and histidine) simultaneously. Here, we report that the effect of NH4(+) on aging yeast depends on the specific amino acid they are deprived of. Compared with no amino acid starvation, starvation for leucine alone or in combination with histidine resulted in the most pronounced NH4(+)-induced CLS shortening, whereas starvation for lysine, alone or in combination with histidine resulted in the least sensitivity to NH4(+). We also show that NH4(+)-induced CLS shortening is mainly mediated by Tor1p in cells starved for leucine or histidine but by Ras2p in cells starved for lysine, and in nonstarved cells. Sch9p protected cells from the effect of NH4(+) under all conditions tested (starved or nonstarved cells), which was associated with Sch9p-dependent Hog1p phosphorylation. Our data show that NH4(+) toxicity can be modulated through manipulation of the specific essential amino acid supplied to cells and of the conserved Ras2p, Tor1p, and Sch9p regulators, thus providing new clues to the development of environmental interventions for CLS extension and to the identification of new therapeutic targets for diseases associated with hyperammonemia.This work was supported by FCT, Portugal, Grant PTDC/AGR-ALI/102608/2008

Ammonium Is Toxic for Aging Yeast Cells, Inducing Death and Shortening of the Chronological Lifespan

Here we show that in aging Saccharomyces cerevisiae (budding yeast) cells, NH4+ induces cell death associated with shortening of chronological life span. This effect is positively correlated with the concentration of NH4+ added to the culture medium and is particularly evident when cells are starved for auxotrophy-complementing amino acids. NH4+-induced cell death is accompanied by an initial small increase of apoptotic cells followed by extensive necrosis. Autophagy is inhibited by NH4+, but this does not cause a decrease in cell viability. We propose that the toxic effects of NH4+ are mediated by activation of PKA and TOR and inhibition of Sch9p. Our data show that NH4+ induces cell death in aging cultures through the regulation of evolutionary conserved pathways. They may also provide new insights into longevity regulation in multicellular organisms and increase our understanding of human disorders such as hyperammonemia as well as effects of amino acid deprivation employed as a therapeutic strategy