Showing papers by "University of Coimbra published in 1997"
TL;DR: There is a relationship between antioxidant potency and the total phenolic groups content in each extract, and Methanolic extracts are more potent as scavengers of peroxyl and superoxide radicals than the ethyl ether extracts.
Abstract: The antioxidant activities of methanol and ethyl ether extracts obtained from Thymus zygis, collected during the flowering or non-flowering period, were evaluated and compared. To investigate this potential, extracts were tested on their capacity to react with diphenylpicrylhydrazyl (DPPH) in a homogeneous medium, and to inhibit Fe2+/ascorbate-induced membrane lipid peroxidation, as estimated by the formation of thiobarbituric acid-reactive substances (TBARS). Although methanol extracts reduce DPPH radicals more efficiently than ethyl ether extracts, suggesting a potent radical scavenger activity, the ethyl ether extracts were found to be most active in inhibiting lipid peroxidation in sarcoplasmic reticulum (SR) membranes. In addition, both extracts present peroxyl and superoxide radical scavenging activities. Peroxyl radicals were generated by the water soluble 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) azoinitiator, and the scavenging activities of the extracts were measured by the inhibition of cis-parinaric acid (PnA) fluorescence decay in SR. Superoxide radicals were generated either by an enzymatic or a non-enzymatic system, and the scavenger ability was evaluated by the inhibition of nitroblue tetrazolium reduction. Methanolic extracts are more potent as scavengers of peroxyl and superoxide radicals than the ethyl ether extracts. Apparently, there is a relationship between antioxidant potency and the total phenolic groups content in each extract.
805 citations
18 May 1997
TL;DR: In this article, a noninvasive approach, based on the computer-aided monitoring of the stator current Park's vector, is introduced for detecting inter-turn stator winding faults in operating three-phase induction machines.
Abstract: The subject of on-line detection and location of inter-turn short circuits in the stator windings of three-phase induction motors is discussed, and a noninvasive approach, based on the computer-aided monitoring of the stator current Park's vector, is introduced. Experimental results, obtained by using a special fault producing test rig, demonstrate the effectiveness of the proposed technique, for detecting inter-turn stator winding faults in operating three-phase induction machines. On-site tests conducted in a power generation plant, using the diagnostic instrumentation system developed, are also reported.
297 citations
TL;DR: It is found that addition of PEG-PE to the membrane of pH-sensitive liposomes composed of cholesteryl hemisuccinate and dioleoylphosphatidylethanolamine confers steric stability to these vesicles, which may be useful for the intracellular delivery in vivo of highly negatively charged molecules.
242 citations
TL;DR: 16S rRNA gene sequencing showed that the isolates constitute two species and that these species are distinct from the other species of the genus Deinococcus, and that the fatty acids of these new species are primarily branched-chain fatty acids.
Abstract: Strains of Deinococcus geothermalis sp. nov. were isolated from the hot spring and runoff at Agnano, Naples, Italy, and from the hot spring at Sao Pedro do Sul in central Portugal, while strains of Deinococcus murrayi sp. nov. were isolated from the hot springs at Sao Pedro do Sul, Sao Gemil, and Alcafache in central Portugal. The strains of D. geothermalis and D. murrayi produce orange-pigmented colonies and have an optimum growth temperature of about 45 to 50°C. The type strains of the two new species are extremely gamma radiation resistant. The fatty acids of these new species are primarily branched-chain fatty acids. The two new species can be distinguished from each other by the lower pH range of D. geothermalis than of D. murrayi, by their fatty acid compositions, and by several biochemical parameters, including the ability of D. geothermalis to grow in minimal medium without yeast extract. 16S rRNA gene sequencing also showed that the isolates constitute two species and that these species are distinct from the other species of the genus Deinococcus. The type strain of D. geothermalis is AG-3a (= DSM 11300), and the type strain of D. murrayi is ALT-1b (= DSM 11303).
233 citations
TL;DR: It is proposed to explore the assumption that the dimension of active genomes, which are primarily a function of the required genetic information to build up an organism, are proportional to the relative contents of DNA in different organisms.
181 citations
TL;DR: An appropriately designed controlled-release drug delivery system can be a major advance towarb solving problems concerning the targeting of a drug to a specific organ or tissue and controlling the release of the drug.
Abstract: An appropriately designed controlled-release drug delivery system can be a major advance towarb solving problems concerning the targeting of a drug to a specific organ or tissue and controlling the...
167 citations
TL;DR: In this paper, an analytical technique that allowed the identification of 12 phenolic acids in honey samples, with emphasis on those phenolics acids which are markers of the botanical origin, was described.
Abstract: In this work we described an analytical technique that allowed the identification of 12 phenolic acids in honey samples, with emphasis on those phenolics acids which are markers of the botanical origin. After optimization of the HPLC conditions, this was applied to the phenolic acids analysis of 20 Erica sp. (heather) and 20 Lavandula stoechas (lavander) portuguese honeys. A close correlation between the phenolic acids patterns and the botanical origin of honey has been found. Erica sp. honeys are characterized by ellagic, p-hydroxybenzoic, syringic and o-coumaric acids, and Lavandula stoechas honeys by gallic acid.
140 citations
TL;DR: In this article, three European estuaries were compared with respect to the dynamics between autotrophic components under the MUST-project: The Mondego River (M) (Portugal), Roskilde Fjord (R) (Denmark) and Venice Lagoon (V) (Italy).
131 citations
TL;DR: In this article, an approach based on flavonoid/phenolics profiles derived from high pressure liquid chromatography is demonstrated to be more precise and informative than traditional microscopy, providing a convenient means for identifying the contributing pollens, and for characterising bee pollens in terms of their predominant constituent pollens.
Abstract: Bee pollen is a mix of bee-collected floral pollens which varies widely in composition. A systematic method for characterising bee pollens in terms of their constituent pollens is needed in view of the growing phytotherapeutic interest in bee pollen products. Studies involving three bee pollen samples collected from Portugal and New Zealand are reported. An approach based on flavonoid/phenolics profiles derived from high pressure liquid chromatography is demonstrated to be more precise and informative than traditional microscopy. This method provides a convenient means for identifying the contributing pollens, and for characterising bee pollens in terms of their predominant constituent pollens.
The flavonoid/phenolics profiles obtained in the course of this work also highlight other observations of interest. For example: bees are shown to be highly selective pollen gatherers from the finding that bee pollens comprise pollen from only a few of the available species; pollen from only one floral source is found in each bee pollen pellet; and flavonoids are normally found as glycosides in pollens but are shown to occur naturally as aglycones in Eucalyptus globulus pollen. Two of these aglycones, tricetin and 3-O-methylquercetin, are reported as pollen constituents for the first time. © 1997 John Wiley & Sons, Ltd.
125 citations
TL;DR: A review of chemical-induced cytotoxic responses that are manifested as interference with mitochondrial metabolism and bioenergetics, gene regulation, or signal transduction in the form of apoptosis and altered cell cycle control can be found in this article.
121 citations
TL;DR: The combined data show that betaxolol is a neuroprotective agent and attenuates the effects on the retina induced by raising the intraocular pressure to simulate an ischaemic insult as may occur in glaucoma.
TL;DR: In this paper, the authors identify condicoes that can be used to convert a conceituacao e pratica dos direitos humanos of a localismo globalizado.
Abstract: Objetiva-se identificar as condicoes que tornem possivel converter a conceituacao e pratica dos direitos humanos de um "localismo globalizado" num projeto emancipatorio e cosmopolita. Argumenta-se que essa e uma questao que so pode ser adequadamente enfrentada da otica da "hermeneutica diatopica" proposta neste artigo.
TL;DR: The quickest path problem arises when transmitting a given amount of data between two given nodes of a network, a lead time and a capacity being assigned to each arc in the network are considered.
TL;DR: Results indicate that glutamate toxicity on PC12 cells results from the inhibition of cystine uptake with consequent GSH depletion and oxidative stress, suggesting that antioxidants may reduce the cellular damage in pathologic conditions associated with excessive glutamate release.
TL;DR: This study shows that the tendency to form aggregates among the four studied proteins correlates with their known amyloidogenic potential, which could perturb the structure and/or stability of the monomeric species leading initially to the formation of soluble aggregates and at a later stage to insoluble amyloids fibrils.
TL;DR: In this paper, the voltammetric behavior of the pyrimidine bases thymine and cytosine is studied using a glassy carbon electrode. And the effect of ultrasound is mainly to enhance transport of electroactive species and to clean the electrode in situ.
TL;DR: This study sequenced in 45 unrelated individuals from Bioko and 50 from São Tomé, two islands in the Gulf of Guinea that have had very different settlement patterns and strengthens the genetic approach to unravel past demographic events.
Abstract: The hypervariable segment I of the control region of the mtDNA was sequenced in 45 unrelated individuals from Bioko and 50 from Sao Tome, two islands in the Gulf of Guinea that have had very different settlement patterns: Bioko was colonized around 10000 BP, while Sao Tome was first settled by the Portuguese, who brought African slaves to the island. Two different patterns of sequence variation are evident and are also clearly a consequence of their very different demographic histories. The Bubi present a low genetic diversity and it is likely that the island was colonized by a small number of individuals with small later migration. Sao Tomeans might be considered a subset of a mainland African population relocated to the island. They present high genetic diversity with a high number of sequences being shared with many continental populations. This study, with knowledge of the population history in island populations, strengthens the genetic approach to unravel past demographic events.
TL;DR: In this article, an analytical sensitivity analysis and optimization implementation for cable-stayed bridge design is described, which is based on the Vax/VMS version of the Modulef code [1 MODULEF Reference Guide.
TL;DR: It is shown that expression of cardosin A is highly restricted to the pistils, and that the enzyme accumulates mainly in protein storage vacuoles of the stigmatic papillae, as well as in flower senescence.
Abstract: The function of aspartic proteinases (EC 3.4.23) present in flowers of Cynara species is still unknown. Cardosin A, as a highly abundant aspartic proteinase from Cynara cardunculus L., a relative of the artichoke, is synthesised as a zymogen and subsequently undergoes proteolytic processing, yielding the mature and active enzyme. Here we report the study of the expression and localization of cardosin A, as a first approach to address the question of its physiological relevance. A polyclonal antibody specific for cardosin A was raised against a synthetic peptide corresponding to an amino acid sequence of the enzyme. This antibody was used to study the organ-specific, tissue-specific and subcellular localization of cardosin A by immunoblotting, tissue printing and immunogold electron microscopy. The results showed that expression of cardosin A is highly restricted to the pistils, and that the enzyme accumulates mainly in protein storage vacuoles of the stigmatic papillae. Cardosin A is also present, although much less abundantly, in the vacuoles of the cells of the epidermis of the style. In view of these results, the possible physiological roles of cardosin A are discussed, namely an involvement in defense mechanisms or pollen-pistil interaction, as well as in flower senescence.
TL;DR: In this paper, Δ5-7-oxosteroids are efficiently prepared from Δ5steroids with t-BuOOH and a copper catalyst, either Cu(II) and Cu(I) salts or Cu metal; selectivity in the presence of a secondary alcohol is observed.
TL;DR: The present results suggest that, in hippocampal glutamatergic nerve terminals, adenosine A1 receptor activation partly inhibits P/Q- and other non-identified types of Ca2+ channels.
TL;DR: The macrocyclic ligand DO2A (1,4,7,10-tetraazacyclodododecane-1,7-bis(acetic acid) was prepared and used as a building block for four new macro cyclic ligands having mixed side-chain chelating groups and was found to be more stable than the corresponding Mg(II) complexes.
Abstract: The macrocyclic ligand DO2A (1,4,7,10-tetraazacyclododecane-1,7-bis(acetic acid)) was prepared and used as a building block for four new macrocyclic ligands having mixed side-chain chelating groups. These ligands and their complexes with Mg(II), Ca(II), and Ln(III) were studied extensively by potentiometry, high-resolution NMR, and water proton relaxivity measurements. The protonation constants of all compounds compared well with those of other cyclen-based macrocyclic ligands. All Ca(II) complexes were found to be more stable than the corresponding Mg(II) complexes. Trends for the stabilities of the Ln(III) complexes are discussed and compared with literature data, incorporating the effects of water coordination numbers, Ln(III) contraction, and the nature of the side chains and the steric hindrance between them. (1)H NMR titrations of DO2A revealed that the first and second protonations take place preferentially at the secondary ring nitrogens, while the third and fourth involved protonation of the acetates. (17)O NMR shifts showed that the DyDO2A(+) complex had two inner-sphere water molecules. Water proton spin-lattice relaxation rates for the GdDO2A(+) complex were also consistent with water exchange between bulk water and two inner-sphere Gd(III) coordination positions. Upon formation of the diamagnetic complexes of DO2A (Ca(II), Mg(II), La(III), and Lu(III)), all of the macrocyclic ring protons became nonequivalent due to slow conformational rearrangements, while the signals for the acetate CH(2) protons remained a singlet.
TL;DR: The new species represented by strains GY-1T and Gy-5 can be distinguished from the other species of the genus Meiothermus by biochemical characteristics, fatty acid composition, DNA-DNA reassociation values, and 16S ribosomal DNA sequence.
Abstract: Strains of Meiothermus cerbereus sp. nov. were isolated from the hot springs within the Geysir geothermal area of Iceland. The strains of Meiothermus cerbereus produce red-orange-pigmented colonies, have an optimum growth temperature of about 55°C, and have higher levels of 3-OH fatty acids than the strains of the other species of the genus Meiothermus. These strains, unlike all other strains of the species of the genus Meiothermus examined previously, require cysteine, thiosulfate, or thioglycolate for growth in liquid Thermus medium, but not in the corresponding medium solidified with agar. Several strains belonging to Meiothermus silvanus, isolated from Geysir, also required reduced sulfur compounds for growth in liquid medium, leading to the hypothesis that this requirement is not a taxonomic characteristic of the new species. The new species represented by strains GY-1T and GY-5 can be distinguished from the other species of the genus Meiothermus by biochemical characteristics, fatty acid composition, DNA-DNA reassociation values, and 16S ribosomal DNA sequence. The type strain for Meiothermus cerbereus is GY-1 (= DSM 11376).
TL;DR: In this article, a Nafion-coated mercury thin-film working electrode is placed in a specially designed small-volume sonovoltammetric cell, where the preparation and curing procedure for the Nafions film on a glassy carbon electrode substrate as well as ultrasound-enhanced mercury deposition through the nafion film are optimized.
Abstract: The high mass transport caused by ultrasonic radiation in the preconcentration of trace metal species in anodic stripping voltammetry (ASV), leads to an order of magnitude enhancement in sensitivity. A Nafion-coated mercury thin-film working electrode is placed in a specially designed small-volume sonovoltammetric cell. The preparation and curing procedure for the Nafion film on a glassy carbon electrode substrate as well as ultrasound-enhanced mercury deposition through the Nafion film are optimized. The resulting electrode assembly is stable under ultrasonic irradiation. Optical microscopy observations show the formation of closely spaced mercury droplets of micrometer dimensions under the Nafion film. The performance characteristics of ultrasound-enhanced ASV at the Nafion-coated mercury thin-film electrode are studied in detail. The detection limit obtained for lead and cadmium test species is 3 × 10-11 M (30 s preconcentration in the presence of ultrasound). A relative standard deviation of 1.2% is o...
TL;DR: As the target of the nitroimidazole action was the DNA, the damage caused to DNA on the electrode surface by a reduction product of this drug could be detected in situ.
Abstract: The newly developed DNA-biosensor is a very promising tool for the investigation and study of the action of drugs specifically designed to interact with DNA. In this work the electrochemical reduction of nitroimidazole drugs was studied in the presence of DNA immobilized onto the surface of a glassy carbon electrode. This enabled preconcentration of the drug onto the electrode surface, which was then electrochemically reduced to the corresponding hydroxylamine which followed by reoxidation give the nitroso compound and subsequently an azoxycompound. Moreover, as the target of the nitroimidazole action was the DNA, the damage caused to DNA on the electrode surface by a reduction product of this drug could be detected in situ.
TL;DR: In this article, the electroanalytical performance at three electrodes: DNA-modified glassy carbon electrode, mercury thin film electrode and glassy carhon electrode, for the study of the electrochemical reduction of metronidazole is compared.
Abstract: The electroanalytical performance at three electrodes: DNA-modified glassy carbon electrode, mercury thin film electrode and glassy carhon electrode, for the study of the electrochemical reduction of metronidazole is compared. All three electrodes showed a similar trend in the reduction mechanism for metronidazole, dependent on pH in the acid and neutral region and independent in alkaline media, although there was a shift in the peak potentials to more negative values when a bare glassy carhon electrode was used compared to the other two. Besides the advantage of using a solid electrode for the reduction of metronidazole, the DNA-modified glassy carbon electrode enables a lower detection limit of l.0pM owing to the preconcentration of the drug on the electrode surface, which is not the case for the mercury thin film or bare glassy carhon electrodes.
TL;DR: It is concluded that oxidative stress causes long‐lasting modifications of the glutamate/D‐[3H]aspartate transport system (or systems), such as oxidation of protein sulfhydryl (SH) groups, which can be recovered by some antioxidants.
Abstract: In the present study we analyzed how oxidative stress conditions induced by ascorbate/ Fe2+ affect the excitatory amino acid (EAA) transport systems in cultured chick retina cells. The uptake of D-...
TL;DR: In this article, the effect of ultrasound on the simultaneous adsorption of guanine and guanosine was studied in detail, and the number of electrons involved in the electro-oxidation process was found to be two.
Book Chapter•
01 Jan 1997TL;DR: In this article, a multicriteria approach is considered for the optimization of a box-girder bridge, with constraints on maximum stresses, minimum stresses in stays and deflections under dead load condition.
Abstract: Box-girder decks are very effective solutions for long span cable-stayed bridges, due to their high torsional stiffness and streamlined profile, which usually lead to a good aerodynamic behaviour. A study on the optimization of such structural system is presented in this paper. The deck is modelled through the assembly of planes of plate-membrane elements. A multicriteria approach is considered for the optimization itself, with constraints on maximum stresses, minimum stresses in stays and deflections under dead load condition. Two illustrative examples are shown.
TL;DR: Thiophenes 1 were treated with m-chloroperbenzoic acid under BF(3) under Et(2)O catalysis to afford thiophene S-monoxides and show a high pi-facial selectivity, a fact that can be explained by the Cieplak-effect.
Abstract: Thiophenes 1 were treated with m-chloroperbenzoic acid (m-CPBA) under BF(3).Et(2)O catalysis to afford thiophene S-monoxides. These could be reacted in situ as intermediary species with a number of dienophiles to provide arenes (with alkynes as dienophiles) or 7-thiabicyclo[2.2.1]hept-2-ene 7-oxides (with alkenes as dienophiles). It was also possible to isolate thiophene S-monoxides in solution and to cycloadd them in a second step. In either way it could be shown that the use of BF(3).Et(2)O enhances the yields of the oxidative cycloaddition of thiophenes considerably. Moreover a greater variety of dienophiles (29a, 29b, 29c) could be reacted with thiophenes than in the case of the noncatalyzed reaction. All cycloadditions catalyzed by BF(3).Et(2)O give only a single diastereoisomer as cycloadduct. The reactions show a high pi-facial selectivity, a fact that can be explained by the Cieplak-effect. Without added dienophiles, 2-methylthiophene (1e) gave a single dimer (36) of 2-methylthiophene S-monoxide, whereas 2,5-dimethylthiophene (1a) gave three dimers (32a-c). In the case of tetrasubstituted thiophenes, thiophene S-monoxides (e.g., 31b and 31c) could be isolated in substance.