1,720,957 research outputs found
Mechanisms underlying age-related defects in the mammalian oocyte: potential deleterious effects of methylglyoxal, a reactive dicarbonyl compound
No full textTatone C., Carbone M., Heizenrieder T., Gualtieri R., Eichenlaub-Ritter U. Mechanisms underlying age-related defects in the mammalian oocyte: potential deleterious effects of methylglyoxal, a reactive dicarbonyl compound University of L’Aquila, Dept of Health Sciences, L’Aquila (Italy) University of Bielefeld, Faculty of Biology, Gene Technolo/Microbiol, Bielefeld (Germany) University of Naples “Federico II”, Dept of Structural and Functional Biology, Naples (Italy) Methylglyoxal (MG) is a reactive dicarbonyl compound physiologically produced by various metabolic pathways. It causes inhibition of proliferation, and mitochondrial respiration,and increases reactive oxygen species, apoptosis and formation of advanced glycation end-products. Recent findings revealed a reduced MG scavenging efficiency in aged mouse ovaries. Therefore, we have investigated potential deleterious effects of MG on female gametes by exposing denuded (DO) and cumulus enclosed (COC) mouse oocytes from adult outbred mice (MF1,CD1) to 50-300M MG during in vitro maturation (IVM) for 16h or 19h. MG negatively affected the rate of polar body formation in both CEO and DO at 16h, with a more pronounced effect in DO. Oocytes with normal metaphase-II spindles decreased from about 73% (control) to 18% after 16h maturation in 75M MG. Moreover, oocytes in ana/telophase-I or with unaligned chromosomes were about three-to four-fold more abundant in the MG-exposed than in the control group. When maturation was prolonged to 19h MG-exposed oocytes exhibited normal appearing spindles and aligned chromosomes and increased PB rate. Time lapse analysis by polarisation microscopy confirmed that MG induced a pronounced meiotic delay. There was no increase in hyperploidy in the MG-exposed oocytes after 19h-IVM, while about 70% of meiosis I arrested oocytes had unaligned chromosomes at 16h-IVM suggesting that young oocytes are capable of dealing with a disturbance by MG by prolonging the spindle assembly checkpoint and progressing to meiosis II only when chromosomes are properly aligned and attached. CEO staining with JC-1 dye showed that MG was capable to induce changes in cytoplasmic localization of high polarized mitochondria. Furthermore, the number of foci of histone gamma H2AX increased in the nuclei of GV-arrested oocytes exposed for 5h to 75M MG, consistent with induction of DNA damage by MG. In accordance, TUNEL assay revealed about 30% apoptosis rate in CEO exposed to 300M MG. In conclusion, the present results indicate that MG may be one of the factors, which act synergistically to cause age-related changes in the ovarian and/or follicle microenvironment resulting in high susceptibility to meiotic errors and reduced developmental potential of aged oocytes
Effects of methylglyoxal-induced carbonyl stress on mitochondrial distribution and GSH-dependent redox potential in mouse oocytes
No full textTatone C, Heizenrieder T, Di Emidio G, Treffon P, Seidel T, Eichenlaub-Ritter U. Effects of methylglyoxal-induced carbonyl stress on mitochondrial distribution and GSH-dependent redox potential in mouse oocytes. Human Reproduction. 2011;26(Suppl.):I165
Utilizzo di una sonda molecolare sensibile allo stato redox per lo studio del danno mitocondriale in ovociti di mammifero
No full textEffects of methylglyoxal-induced carbonyl stress on mitochondrial distribution and GSH-dependent redox potential in mouse oocytes
No full text
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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