Browsing by Issue Date, starting with "2003-12"
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- Inhibition of mouse liver respiration by Chelidonium majus isoquinoline alkaloidsPublication . Barreto, Maria do Carmo; Pinto, Ruy Eugénio; Arrabaça, João Daniel; Pavão, Maria LeonorThe alkaloids from Chelidonium majus L. which had a significant inhibitory effect in mitochondrial respiration were those which contain a positive charge due to a quaternary nitrogen atom, i.e., chelerythrine, sanguinarine, berberine and coptisine, both with malate+glutamate or with succinate as substrates. When malate+glutamate was used as substrate, chelerythrine and berberine, which contain methoxy groups, were particularly more active, since they had a strong effect even at low concentrations. In submitochondrial particles, berberine and coptisine had a marked inhibitory effect on NADH dehydrogenase activity but practically no effect on succinate dehydrogenase activity, whereas chelerythrine and sanguinarine inhibited more strongly succinate dehydrogenase than NADH dehydrogenase, which is in agreement with the results found for mitochondrial respiration. Protopine and allocryptopine, which did not inhibit mitochondrial respiration, strongly inhibited NADH dehydrogenase in submitochondrial particles, but had no effect on succinate dehydrogenase activity.
- A importância da microscopia electrónica no estudo taxonómico do recife algal fóssil da Prainha.Publication . Neto, Ana I.; Amen, Rui G.; Azevedo, José M. N.
- Diagnosis of Enzyme Inhibition Based on the Degree of InhibitionPublication . Antunes, Fernando; Marinho, Helena Susana; Barreto, Maria do Carmo; Pavão, Maria Leonor; Pinto, Ruy EugénioIn this work, a method for the diagnosis of kinetic inhibition, based on the dependence of the degree of inhibition (s) on the inhibitor concentration [1] and on the substrate concentration [S], is presented. Because the degree of inhibition is a ratio between rates, kinetic data are normalized by the introduction of an internal control-the rate of the uninhibited reaction. Therefore, the error associated with the kinetic measurements decreases and less experimental measurements are necessary to achieve the diagnosis. The process described, which uses graphical and/or non-linear fitting procedures, allows distinguishing between 20 different kinds of inhibition, including not only linear and hyperbolic, but also parabolic and rational 2,2 inhibitions. Rational 2,2 indicates a new type of inhibition corresponding to an incomplete parabolic inhibition, i.e. mechanistically it corresponds to an inhibitor that binds to two inhibition sites producing enzymatic complexes that are still active. In spite of its comprehensiveness, the diagnosis process is greatly facilitated by the division of the diagnosis of the inhibition in a step-by-step procedure, where only two rival models are evaluated in each step. In the non-linear fittings, the choice between rival models uses a test based on information statistics theory, the Akaike information criterion test, in order to penalize complex models that tend to be favoured in fittings. Finally, equations that allow the determination of inhibition kinetic constants were also deduced. The formalism presented was tested by examining inhibition of acid phosphatase by phosphate (a linear competitive inhibitor).
- Life history of Colpomenia sinuosa (Scytosiphonaceae, Phaeophyceae) in the Azores.Publication . Toste, Marisa F.; Parente, Manuela I.; Neto, Ana I.; Fletcher, Robert L.Colpomenia sinuosa (Mertens ex Roth) Derbès and Solier (Scytosiphonaceae, Phaeophyceae) is a common species on the rocky intertidal shores of the Azores, where reproductive gametophytes occur throughout the year. Life-history studies of this species were carried out in culture, and both sexual and asexual reproduction were observed. Anisogamous gametes fused to form zygotes. The zygotes gave rise to a filamentous prostrate sporophyte generation bearing unilocular sporangia, under both short-day and long-day conditions at 15 and 22° C, and to both unilocular and plurilocular sporangia, under the lower temperature condition. Unispores developed into gametophytes, and plurispores gave rise to filamentous sporophytes. Asexual reproduction was carried out by unfused female gametes and asexual plurispores produced from the same gametophyte. Unfused gametes developed into filamentous prostrate sporophytes producing unilocular sporangia in both culture conditions, and unispores released from the sporangia gave rise to gametophytes. Asexual plurispores from field gametophytes, under both culture conditions, developed directly into new gametophytes. The species exhibited three types of life history: a heteromorphic, diplohaplontic; a heteromorphic, monophasic (both with alternation between the erect and filamentous prostrate thalli); and a monomorphic, monophasic.
- Fourierentwicklung gewisser EisensteinreihenPublication . Funk, MatthiasEisenstein desenvolveu, no século XIX, uma via alternativa para descrever as funções trigonométricas, que geralmente são explicadas através da função exponencial. As funções alternativas aí usadas foram designadas como Séries de Eisenstein. Hoje em dia, estas servem como ferramenta importante na teoria das funções modulares, que, por sua vez, tiveram um papel central na demonstração do último teorema de Fermat. Encontramos as Séries de Eisenstein no método de Selberg-Rankin e no espectro de certas funções. Em 1940, Selberg conseguiu descrever os coeficientes de Fourier de uma Série de Eisenstein, que forma uma função periódica no plano superior complexo. Quando generalizamos este plano superior complexo numa dimensão n (conhecida como plano de Siegel), obtemos n+1 classes diferentes de Séries de Eisenstein, que também são periódicas e possuem, portanto, um desenvolvimento numa Série de Fourier, cujos coeficientes foram totalmente desconhecidos até que Krieg encontrou uma solução para o caso de n=2. Mas o caminho utilizado não funciona para n2. No âmbito da tese de doutoramento, conseguiu-se encontrar uma descrição em funções conhecidas para todos os coeficientes de uma destas n+1 classes da Série de Eisenstein. Parte dos coeficientes são nulos. Entre alguns dos restantes existem uma correlação funcional.
- A new species of the genus Aphrodes Curtis from the Azores (Hemiptera, Cicadellidae)Publication . Quartau, José A.; Borges, Paulo A. V.As a result of an ecological project on the existing native laurel forests (laurisilva) in the Azores, Aphrodes hamiltoni n. sp. was collected using the pitfall technique. The new species was always found beneath the surface litter of these woods and on the following islands: S. Maria, S. Miguel, Terceira, S. Jorge, Pico, Faial and Flores. It appears as an endemic species for the Azores, being readily distinguished from all remaining taxa within Aphrodes Curtis by the typical spines in the apical part of the aedeagus. Compared with other endemic Azorean arthropods sampled recently, Aphrodes hamiltoni n. sp. is a common species not particularly under threat and appears as a good indicator of sites rich in endemic arthropods. Consequently, the new species will be highly valued in monitoring programmes to evaluate the conservation status of the native forests of the Azores.