1,720,973 research outputs found
L-carnitine protects mammalian cells from chromosome aberrations but not from inhibition of cell proliferation induced by hydrogen peroxide.
No full textL-carnitine is a small essential molecule indispensable in fatty acid metabolism and required in several biological pathways regulating cellular homeostasis. Despite considerable progress in understanding of L-carnitine biosynthesis and metabolism, very few data are reported concerning the protective role of L-carnitine from oxidative stress-induced DNA damage that is known to be a factor in cell transformation and tumourigenesis. In order to detect the capability of L-carnitine to protect mammalian cells from oxidative stress-induced chromosomal effects, we analysed chromosome aberrations in mitotic CHO cells, which represent an appropriate cytogenetic model to study compounds that enhance cell protection against externally induced DNA damage. We chose H2O2 as an inducer of oxidative stress. Our results demonstrate for the first time a marked and reproducible reduction of H2O2-induced chromosome damage involving an L-carnitine-mediated capacity to buffer intracellular formation of reactive oxygen species (ROS). Furthermore, by studying the mitotic index and cell cycle progression, we also demonstrated that this protective effect is highly specific, since L-carnitine itself was not able to prevent the inhibition of cell growth caused by H2O2
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
Carnitine prevents clastogenic effects induced by hydrogen peroxide in mammalian cells
No full textCarnitine is a small essential molecule that regulates the substrate flux and energy balance across cell membranes by modulating both the transport of long-chain fatty acids into mitochondria and their subsequent β-oxidation. Although humans are capable to synthesize it endogenously, approximately 75% of body carnitine sources come from diet and particularly from food of animal origin such as meat, poultry, fish and dairy products. Due to its intrinsic interaction with the bioenergetics processes, carnitine plays an important role in diseases associated with metabolic compromise, especially mitochondria-related disorders. It has been reported that administration of carnitine by diet or at pharmacological doses can have significant benefit in several physiopathological situations such as ischemia, myocardial injury and neurodegenerative diseases, but there is no data on the possible protective role of carnitine against other oxidative stress-induced pathologies associated with an altered chromosome stability such as cancer. Therefore, we analysed the potential capability of carnitine to protect mammalian cells from genetic instability induced by H2O2, using Chinese Hamster Ovary (CHO) cells as a mammalian cell model having a stable karyotype and the chromosome aberration test as genetic end point. Our results showed that in the absence of carnitine H2O2 induced a high and dose-depend-ent induction of structural chromosome aberrations in the concentration range 0.1-0.4 mM whereas at the same H2O2 doses, a pre-treatment with 4 mM carnitine produced a strong decrease either of the percent of cells with aberrations or of the aberration frequency. The observed carnitine-mediated prevention of H2O2-induced chromosome aberrations reaches almost the control value in the cultures treated with 0.1 mM of H2O2 thus evidencing a reduction of about 70%. These data, together with preliminary results showing that carnitine is not able to protect cells from the inhibition of cell growth caused by H2O2, suggest that carnitine protects mammalian cells from H2O2–induced clastogenic damage and this effect is reproducible and highly specific
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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