1,720,969 research outputs found
Inhibitory effect of NAD(P)H : quinone oxidoreductase on autoxidation of 6-hydroxydopa and 6-hydroxydopamine
No full text6-Hydroxydopa and 6-hydroxydopamine undergo autoxidation in the presence of molecular oxygen giving rise to the corresponding p-quinones. NAD(P)H:quinone oxidoreductase (QR) purified from Glycine max showed that it inhibited autoxidation of 6-hydroxydopa and 6-hydroxydopamine. The inhibition of autoxidation of 6-hydroxydopa was greater than B-hydroxydopamine. QR had a potentiated effect in preventing 6-hydroxydopa oxidation in the presence of catalase and superoxide dismutase. Reduced glutathione increased protective effect when incubated with QR on both 6-hydroxydopa and B-hydroxydopamine. Homogenized tissues from rat brain also showed to inhibit 6-hydroxydopa autoxidation. Our observations suggest a possible role for brain NAD(P)H:quinone oxidoreductase in protection of neurons from the toxic effect of quinones
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
Proteomic analysis of muscle tissue from gilthead sea bream (Sparus aurata, L.) farmed in offshore floating cages
No full textCharacterization of the muscle tissue proteome is key to many aspects of fish aquaculture, encompassing physiology, growth, food safety, seafood authentication and quality, traceability and shelf-life. In this study, a 2D-PAGE-MS study was performed on gilthead sea bream (Sparus aurata, L) muscle tissue along the production cycle in four offshore floating cage plants and two repopulation lagoons located in different areas of Sardinia, Italy. The aim of this study was to accomplish systematic characterization of the gilthead sea bream muscle proteome, and to gather data about its variability in physiological conditions occurring in both farmed and wild fish. In general, a relatively stable protein expression pattern was observed in farmed sea bream muscle compared to other more dynamic tissue proteomes, such as liver. However, several statistically significant variations in abundance of some proteins and their isoforms were detected, related to growth and environmental factors. Among these, parvalbumins, troponins, and Wap65 showed variations according to fish length and water temperature. Interestingly, the ratio of structural proteins versus glycolytic enzymes was also observed to change during the production cycle, showing an increase with fish length. In order to assess whether the farming conditions were able to induce alterations in the muscle proteome, farmed and wild fish were subjected to a differential proteomics analysis. The data gathered in this study indicate that the protein expression profile of muscle tissue is comparable in wild and maricultured gilthead sea breams of commercial size, supporting the view that farming in offshore floating cages might favor proper muscle tissue development, and therefore enable the production of higher quality fish. In conclusion, this work describes the detailed characterization of the sea bream muscle proteome, and provides a number of insights on its size and environment-related variability. (C) 2010 Elsevier B.V. All rights reserved
Effect of NAD(P)H:quinone oxidoreductase on tyrosinase-mediated oxidation of opioid neuropeptides Leu-enkephalin and Met-enkephalin
No full textIn vitro experiments are reported showing that NAD(P)H:(quinone acceptor) oxidoreductase (QR), purified from Glycine max seedlings, reduces Leu- and Met-enkephalin-tyrosinase oxidation products, in the presence of NADH or NADPH. QR was not capable to catalyze the reduction of N-acetyl-dopaquinone formed by the action of mushroom tyrosinase on N-acetyl-L-tyrosine, while it was able to reduce dopachrome. The results support the hypothesis that QR can inhibit the formation of melanin-like compounds, as catalyzed by the action of tyrosinase on Leu-enkephalin and Met-enkephalin. It is proposed that, in the presence of NAD(P)H as the electron donor, the inhibition occurs by the specific conversion of the dopachrome-derivative into the reduced precursor, leucodopachrome-derivative
A hydroxyquinone with amine oxidase activity: preparation and properties
No full textThe preparation and some properties of a hydroxyquinone showing an amine oxidase-like activity are described. The compound, 2-hydroxy-5-methyl-1,4-benzoquinone, oxidizes a wide range of primary amines, both benzylic and non-benzylic, at the expenses of molecular oxygen in the presence of Cu 2+ ions, and reacts with hydrazine derivatives leading to stable, inactive adducts. This behaviour is similar to that of 2,4,5-trihydroxyphenylalanine quinone-containing amine oxidases and therefore the present compound could be a useful model to understand the reaction mechanism of those enzymes
Purification and characterization of an NAD(P)H: quinone oxidoreductase from Glycine max seedlings
No full textAn NAD(P)H:(quinone acceptor) oxidoreductase (EC 1.6.99.2) was purified from Glycine max seedlings by means of chromatographic procedures. After 1371-fold purification, the enzyme showed a single band in IEF corresponding to an isoelectric point of 6.1. A single band was also found in native-PAGE both by; activity staining and Coomassie brilliant blue staining. The molecular mass determined in SDS-PAGE was 21900 Da, while in HPLC gel-filtration it was 61000 Da. The NAD(P)H:quinone oxidoreductase was able to use NADH or NADPH as the electron donor. Among the artificial quinones which are reduced by this enzyme, 6-hydroxydopa- and 6-hydroxydopamine-quinone are of particular interest because of their neurotoxic effects
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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