1,720,959 research outputs found
The involvement of transition metal ions on iron-dependent lipid peroxidation
Full text linkThe metals iron (Fe) and copper (Cu) are considered trace elements, and the metals cobalt (Co) and nickel (Ni) are known as ultra-trace elements, considering their presence in low to very low quantity in humans. The biologic activity of these transition metals is associated with the presence of unpaired electrons that favor their participation in redox reactions. They are part of important enzymes involved in vital biologic processes. However, these transition metals become toxic to cells when they reach elevated tissue concentrations and produce cellular oxidative damage. Phospholipid liposomes (0.5 mg/ml, phosphatidylcholine (PC)/phosphatidylserine (PS), 60/40) were incubated for 60 min at 37°C with 25 μM of Fe2+ in the absence and in the presence of Cu2+, Co2+, and Ni2+ (0-100 μM) with and without the addition of hydrogen peroxide (H 2O2, 5-50 μM). Iron-dependent lipid peroxidation in PC/PS liposomes was assessed by thiobarbituric acid-reactive substances (TBARS) production. Metal transition ions promoted lipid peroxidation by H 2O2 decomposition and direct homolysis of endogenous hydroperoxides. The Fe2+-H2O2-mediated lipid peroxidation takes place by a pseudo-second order process, and the Cu 2+-mediated process by a pseudo-first order reaction. Co2+ and Ni2+ alone do not induce lipid peroxidation. Nevertheless, when they are combined with Fe2+, Fe2+-H2O 2-mediated lipid peroxidation was stimulated in the presence of Ni2+ and was inhibited in the presence of Co2+. The understanding of the effects of transition metal ions on phospholipids is relevant to the prevention of oxidative damage in biologic systems. © 2009 Springer-Verlag.Fil: Repetto, Marisa Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Ferrarotti, Nidia Fatima. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Bioquímica Clínica; ArgentinaFil: Boveris, Alberto Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentin
Rat Brain Damage due to Iron and Copper Toxicity
Full text linkBrain damage is associated to oxidative stress in iron (Fe) and copper (Cu) overloads in rats, in a dose- and time-dependent accumulation of the metals in the organ. The generation of singlet oxygen in brain measured in vivo by in situ chemiluminescence indicates that Fe and Cu overloads increased phospholipid and protein oxidation, and decreased non enzymetic endogenous antioxidants content in the organ, mainly glutathione (GSH). These results fit with a Fenton/ Haber-Weiss type reaction between iron, copper and endogenously produced superoxide anion (O2 •-) and hydrogen peroxide (H2 O2 ) to yield hydroxyl radical (OH•), as well as reactions involving thiol groups of GSH and proteins.Fil: Musacco Sebio, Rosario Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Saporito Magriñá, Christian Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Ferrarotti, Nidia Fatima. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Acosta, Juan Manuel. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Boveris, Alberto Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Repetto, Marisa Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentin
Time course and mechanism of brain oxidative stress and damage for redox active and inactive transition metals overload
Full text linkThe objective of this work was to study the in vivo time course of biochemical processes of oxidative damage in the brain of Sprague-Dawley rats that received an acute overload of the redox active metals iron (Fe) and copper (Cu), and the redox inactive cobalt (Co) and nickel (Ni). Oxidative stress indicators (phospholipid and protein oxidation), glutathione (GSH), antioxidant enzymes and NADPH oxidase activities, and the plasma inflammatory cytokine (IL-6) were measured. The results showed that in brain oxidative mechanisms for both sets of metal are different, however in both cases are irreversible. The mechanism for Fe and Cu oxidative damage is mediated by the generation of the free radical hydroxyl (Fenton reaction and homolytic cleavage of hydroperoxides). Two events of antioxidant protection prior to oxidation of phospholipids and proteins by Fe and Cu are considered. The first process is the use of GSH and the second is the increased activity of the Cu, Zn-SOD and catalase enzymes. The oxidative mechanism for metal redox inactive is the consumption of GSH, NADPH oxidase activation and inflammatory response mediated by IL-6. Co increased protein oxidation as a result of the inflammatory process. Ni produced increments of phospholipid oxidation and SOD activity.Fil: Ferrarotti, Nidia Fatima. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Musacco Sebio, Rosario Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Saporito Magriñá, Christian Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Acosta, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Repetto, Marisa Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentin
Brain oxidative stress in the chronic overloads of iron and copper in rats.
No full textMale rats of 80–90 g that were fed 42 days with a commercial rodent diet of 2780 kcal/100 g and received chronic overloads of either Fe(II) or Cu(II) in the drinking water. The two metals produced brain oxidative stress and damage with marked increases in the indicators of oxidative processes: in vivo brain surface chemiluminescence (the sensitive organ non-invasive assay for oxidative free radical reactions), and the ex vivo processes of phospholipid peroxidation and protein oxidation. Brain redox imbalance was also indicated by marked decreases in the cellular indicators of oxidative metabolic stress: reduced glutathione (GSH) content and reduced/oxidized glutathione ratio (GSH/GSSG). Brain decreased GSH content has a central role in the biochemical oxidative processes associated with Fe and Cu chronic damage. The understanding of biochemical oxidative imbalances in the rat brain with chronic Fe(II) or Cu(II) overloads may be useful for the establishment of pharmacological therapies for human pathologies associated to Fe and Cu cellular imbalances.Fil: Musacco Sebio, Rosario Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Ferrarotti, Nidia Fatima. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Lairion, Fabiana Norma. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Saporito Magriñá, Christian Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Fuda, Julián Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Fisicomatemática. Cátedra de Física; ArgentinaFil: Torti, Horacio Emilio. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Fisicomatemática. Cátedra de Física; ArgentinaFil: Boveris, Alberto Antonio. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Repetto, Marisa Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; Argentin
Redox dyshomeostasis in the experimental chronic hepatic overloads with iron and copper
No full textMale rats of 80–90 g were overloaded with either Fe(II) or Cu(II) for 42 days by high concentrations of FeCl2 or CuSO4 in the drinking water. The animals were fed with a commercial rodent diet of 2780 kcal/100 g. Both metal treatments led to a liver redox imbalance and dyshomeostasis with oxidative stress and damage and the concomitant enhancement of oxidative processes as indicated by in vivo surface liver chemiluminescence, the sensitive and organ non-invasive assay for oxidative free radical reactions, and by ex vivo determined processes of phospholipid peroxidation and protein oxidation. In parallel, marked decreases in the antioxidant defense were observed. Liver reduced glutathione (GSH) content and the reduced/oxidized glutathione ratio (GSH/GSSG) were early indicators of oxidative metabolic disturbance upon the metal overloads. Thus, GSH plays a central role in the defense reactions involved in the chronic toxicity of Fe and Cu. Chronic overloads of Fe or Cu in rats afford an experimental animal model of hemochromatosis and of Wilson's disease, respectively. These two animal models could be useful in the study and development of the beneficial effects of pharmacological interventions in the two human diseases.Fil: Musacco Sebio, Rosario Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Ferrarotti, Nidia Fatima. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Bioquímica Clínica; ArgentinaFil: Saporito Magriñá, Christian Martín. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Fuda, Julián Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Fisicomatemática. Cátedra de Física; ArgentinaFil: Torti, Horacio Emilio. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Fisicomatemática. Cátedra de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Lairión, Fabiana. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química General e Inorgánica; ArgentinaFil: Boveris, Alberto Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica; ArgentinaFil: Repetto, Marisa Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentin
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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