Browsing by Author "Martins, H."
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- An attempt to use CIE Lab digital colour to study sediment profiles from the Alvor estuary, South PortugalPublication . Veiga-Pires, C.; Mestre, Nélia; Moura, Delminda; Martins, H.; Boski, T.The study of estuarine sedimentary records is of great interest for paleo-environmental and paleo-climatologic reconstructions, because they represent environments that are sensitive to sea level and climatic variations, and also because they are characterized high sedimentary rates. However, due to the price and time needed to analyze the geochemical composition of sediments, it is very difficult to obtain profiles with a high resolution needed toanswer present scientific problems. In the present work, we report results obtained by applying solid-state spectrophotometry on cores from the Alvor's estuary (Algarve), which allows acquiring almost continous, high resolution, digital colour profiles. CIE Labcolour data, obtained with a Colortron spectrophotometer in there cores, were to geochemical sediment characteristics using multivariate statistical analyses.(...)
- Postglacial organic carbon accumulation in coastal zones-A possible cause for varying atmospheric CO2 levels: preliminary data from SW PortugalPublication . Boski, T.; Moura, Delminda; Correia, Victor; Martins, H.; Veiga-Pires, C.; Camacho, Sarita; Wilamowski, A.We report the preliminary data on organic carbon accumulation rates which are being determined in the infill sequences of several estuaries, in the coastal fringe of Algarve (S Portugal). The so far analysed sedimentary sequences of Guadiana River estuary represent the time span from ca 10000 yr. cal BP to present. The obtained data indicate that until ca 7000 yr. cal BP, i.e. during the period of fast sea level rise, organic carbon accumulated at an average rate ranging from 160 to 320 gm yr . In the Middle and Upper Holocene, when the sea level rise was not exceeding 25cm/century the organic carbon accumulation rate dropped to an average value of ca 50 gm yr . The analysis of gas bubble content from ice cores indicates that the atmospheric CO concentration evolved during the last glacial/interglacial transition, from 180 ppv minimum during the LGM to the 270 ppmV preindustrial level. Considering that the terrestrial particulate organic matter is an essential fertiliser of the ocean, it is postulated that enhanced burial of POM in the coastal areas during the period of fast postglacial sea level rise is responsible for decrease of primary productivity in the open ocean and consequent transfer of 200 Gt. ofCto the atmosphere.
- Vanadate oligomers: in vivo effects in hepatic vanadium accumulation and stress markersPublication . Gândara, Ricardo M. C.; S. Soares, Sandra; Martins, H.; Gutiérrez-Merino, Carlos; Aureliano, M.The formation of vanadate oligomeric species is often disregarded in studies on vanadate effects in biological systems, particularly in vivo, even though they may interact with high affinity with many proteins. We report the effects in fish hepatic tissue of an acute intravenous exposure (12, 24 h and 7 days) to two vanadium(V) solutions, metavanadate and decavanadate, containing different vanadate oligomers administered at sub-lethal concentration (5 mM; 1 mg/kg). Decavanadate solution promotes a 5-fold increase (0.135 ± 0.053 lg V 1 dry tissues) in the vanadium content of the mitochondrial fraction 7 days after exposition, whereas no effects were observed after metavanadate solution administration. Reduced glutathione (GSH) levels did not change and the overall reactive oxygen species (ROS) production was decreased by 30% 24 h after decavanadate administration, while for metavanadate, GSH levels increased 35%, the overall ROS production was depressed by 40% and mitochondrial superoxide anion production decreased 45%. Decavanadate intoxication did not induce changes in the rate of lipid peroxidation till 12 h, but later increased 80%, which is similar to the increase observed for metavanadate after 24 h. Decameric vanadate administration clearly induces different effects than the other vanadate oligomeric species, pointing out the importance of taking into account the different vanadate oligomers in the evaluation of vanadium(V) effects in biological systems.
- Vanadium and cadmium in vivo effects in cardiac muscle: metal accumulation and oxidative stress markersPublication . S. Soares, Sandra; Martins, H.; Gutiérrez-Merino, Carlos; Aureliano, M.Several biological studies associate vanadium and cadmium with the production of reactive oxygen species (ROS), leading to lipid peroxidation and antioxidant enzymes alterations. The present study aims to analyse and compare the oxidative stress responses induced by an acute intravenous exposure (1 and 7 days) to a sub-lethal concentration (5 mM) of two vanadium solutions, containing different vanadate noligomers (n=1–5 or n=10), and a cadmium solution on the cardiac muscle of the marine teleost Halobatrachus didactylus (Lusitanian toadfish). It was observed that vanadium is mainly accumulated in mitochondria (1.33±0.26 μM), primarily when this element was administrated as decameric vanadate, than when administrated as metavanadate (432±294 nM), while the highest content of cadmium was found in cytosol (365±231 nM). Indeed, decavanadate solution promotes stronger increases in mitochondrial antioxidant enzymes activities (catalase: +120%; superoxide dismutase: +140%) than metavanadate solution. On contrary, cadmium increases cytosolic catalase (+111%) and glutathione peroxidases (+50%) activities. It is also observed that vanadate oligomers induce in vitro prooxidant effects in toadfish heart, with stronger effects induced by metavanadate solution. In summary, vanadate and cadmium are differently accumulated in blood and cardiac subcellular fractions and induced different responses in enzymatic antioxidant defence mechanisms. In the present study, it is described for the first time the effects of equal doses of two different metals intravenously injected in the same fish species and upon the same exposure period allowing to understand the mechanisms of vanadate and cadmium toxicity in fish cardiac muscle.
- Vanadium distribution following decavanadate administrationPublication . S. Soares, Sandra; Martins, H.; Aureliano, M.An acute exposure of two vanadate solutions— metavanadate and decavanadate—containing different vanadate oligomers, induces different patterns of subcellular vanadium distribution in blood plasma, red blood cells (RBC), and cardiac muscle subcellular fractions of the fish Sparus aurata (gilthead seabream). The highest amount of vanadium was found in blood plasma 1 h after (5 mM) intravenous vanadate administration (295 € 64 and 383 € 104 lg V/g dry tissue, for metavanadate and decavanadate solutions, respectively), being 80-fold higher than in RBC. After 12 h of administration, the amount of vanadium in plasma, as well as in cardiac cytosol, decreased about 50%, for both vanadate solutions. During the period between 1 and 12 h, the ratio of vanadium in plasma/vanadium in RBC increased from 27 to 128 for metavanadate, whereas it remains constant (77) for decavanadate. Both vanadium solutions were primarily accumulated in the mitochondrial fraction (138 € 0 and 195 € 34 ng V/g dry tissue for metavanadate and decavanadate solutions, respectively, after 12 h exposure), rather than in cytosol. The amount of vanadium in cardiac mitochondria was twofold higher than in cytosol, earlier for metavanadate (6 h) than for decavanadate (12 h). It is concluded that, in fish cardiac muscle, the vanadium distribution is dependent on the administration of decameric vanadate, with vanadium being mainly distributed in plasma, before being accumulated into the mitochondrial fraction.
- Vanadium distribution, lipid peroxidation and oxidative stress markers upon decavanadate in vivo administrationPublication . S. Soares, Sandra; Martins, H.; Duarte, Rui O.; Moura, José J. G.; Coucelo, Josefina; Gutiérrez-Merino, Carlos; Aureliano, M.The contribution of decameric vanadate species to vanadate toxic effects in cardiac muscle was studied following an intravenous administration of a decavanadate solution (1 mM total vanadium) in Sparus aurata. Although decameric vanadate is unstable in the assay medium, it decomposes with a half-life time of 16 allowing studying its effects not only in vitro but also in vivo. After 1, 6 and 12 h upon decavanadate administration the increase of vanadium in blood plasma, red blood cells and in cardiac mitochondria and cytosol is not affected in comparison to the administration of a metavanadate solution containing labile oxovanadates. Cardiac tissue lipid peroxidation increases up to 20%, 1, 6 and 12 h after metavanadate administration, whilst for decavanadate no effects were observed except 1 h after treatment (+20%). Metavanadate administration clearly differs from decavanadate by enhancing, 12 h after exposure, mitochondrial superoxide dismutase (SOD) activity (+115%) and not affecting catalase (CAT) activity whereas decavanadate increases SOD activity by 20% and decreases ( 55%) mitochondrial CAT activity. At early times of exposure, 1 and 6 h, the only effect observed upon decavanadate administration was the increase by 20% of SOD activity. In conclusion, decavanadate has a different response pattern of lipid peroxidation and oxidative stress markers, in spite of the same vanadium distribution in cardiac cells observed after decavanadate and metavanadate administration. It is suggested that once formed decameric vanadate species has a different reactivity than vanadate, thus, pointing out that the differential contribution of vanadium oligomers should be taken into account to rationalize in vivo vanadate toxicity.