1,720,961 research outputs found
Suscettibilità dei tessuti di animali ipertiroidei allo stress ossidativo in vivo. Ruolo dei mitocondri nello stress ossidativo indotto dall'esercizio acuto nel muscolo scheletrico di animali ipertiroidei.
No full textEffect of T3 on metabolic response and oxidative stress in skeletal muscle from sedentary and trained rats
No full textWe investigated whether swim training modifies the effect of T3-induced hyperthyroidism on metabolism and oxidative damage in rat muscle. Respiratory capacities, oxidative damage, levels of antioxidants, and susceptibility to oxidative challenge of homogenates were determined. Mitochondrial respiratory capacities, H2O2 release rates, and oxidative damage were also evaluated. T3-treated rats exhibited increases in muscle respiratory capacity, which were associated with enhancements in mitochondrial respiratory capacity and tissue mitochondrial protein content in sedentary and trained animals, respectively. Hormonal treatment induced muscle oxidative damage and GSH depletion. Both effects were reduced by training, which also attenuated tissue susceptibility to oxidative challenge. The changes in single antioxidant levels were slightly related to oxidative damage extent, but the examination of parameters affecting the susceptibility to oxidants indicated that training was associated with greater effectiveness of the muscle antioxidant system. Training also attenuated T3-induced increases in H2O2 production and, therefore, oxidative damage of mitochondria by lowering their content of autoxidizable electron carriers. The above results suggest that moderate training is able to reduce hyperthyroid state-linked tissue oxidative damage, increasing antioxidant protection and decreasing the ROS flow from the mitochondria to the cytoplasmic compartment
Role of mitochondria in exercise - induced oxidative stress in skeletal muscle from hyperthyroid rats
No full textTri-iodothyronine treatment differently affects liver metabolic response and oxidative stress in sedentary and trained rats
No full textWe investigated whether swim training modifies the effects of tri-iodothyronine (T3) treatment on the metabolic response and oxidative damage of rat liver. Respiratory capacities, oxidative damage, levels of antioxidants, and susceptibility to oxidative challenge of liver homogenates were determined. Mitochondrial respiratory capacities, rates of H2O2 release, and oxidative damage were also evaluated. Training modified most of the measured parameters in both thyroid states, although the extent of changes was higher in hyperthyroid preparations. T3 treatment enhanced homogenate respiratory capacity, which was further enhanced by training despite the decrease in mitochondrial respiratory capacity. Hormonal treatment also induced liver oxidative damage and glutathione depletion, and increased tissue susceptibility to oxidative challenge. These effects were lower in trained animals. The extensive oxidative damage found in liver homogenates from hyperthyroid sedentary rats was due to low tissue antioxidant protection and high mitochondrial H2O2 production rate, which were increased and decreased respectively by animal training. The training effect on H2O2 production was associated with lower oxidative damage and susceptibility to Ca2+-induced swelling of mitochondria. Measurements with respiratory inhibitors indicated that the differences in H2O2 release in hyperthyroid groups were due to differences in mitochondrial content of autoxidizable electron carrier located at Complex III. We conclude that moderate training is able to reduce hyperthyroid state-linked cellular and subcellular oxidative damage in liver increasing its antioxidant defenses and decreasing the mitochondrial generation of reactive oxygen species
Vitamin E attenuates cold-induced rat liver oxidative damage reducing H2O2 mitochondrial release.
No full textVitamin E is a major chain-breaking antioxidant which is able to reduce liver oxidative damage without modifying aerobic capacity in T3-treated rats. We investigated whether vitamin E has similar effects in hyperthyroid state induced by cold exposure. Cold exposure increased aerobic capacity and O2 consumption in homogenates and mitochondria and tissue mitochondrial protein content. Vitamin E did not modify aerobic capacity and mitochondrial protein content of cold liver, but increased ADP-stimulated respiration of liver preparations.
Succinate-supported H2O2 release rates were increased by cold during basal and stimulated respiration, whereas the pyruvate/malate-supported ones increased only during basal respiration. Vitamin administration to cold-exposed rats decreased H2O2 release rates with both substrates during basal respiration. This effect reduced ROS flow from mitochondria to cytosol, limiting liver oxidative damage. Cold exposure also increased mitochondrial capacity to remove H2O2, which was reduced by vitamin treatment, showing that the antioxidant also lowers H2O2 production rate. The different effects of cold exposure and vitamin treatment on H2O2 generation were also found in the presence of respiration inhibitors. Although this can suggest that the cold and vitamin induce opposite changes in mitochondrial content of autoxidizable electron carriers, it is likely that vitamin effect is due to its capacity to scavenge superoxide radical. Finally, vitamin E reduced mitochondrial oxidative damage and susceptibility to oxidants, and prevented Ca2+-induced swelling elicited by cold. In the whole, our results suggest that vitamin E is able to maintain aerobic capacity and attenuate oxidative stress of hepatic tissue in cold-exposed rats modifying mitochondrial population characteristics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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