1,720,972 research outputs found
The interplay between mitochondrial protein and iron homeostasis and its possible role in ageing
No full textFree (labile or chelatable) iron is extremely redox-active and only represents a small fraction of the total mitochondrial iron population. Several studies have shown that the proportion of free iron increases with age, leading to increased Fenton chemistry in later life. It is not clear why free iron accumulates in mitochondria, but it does so in parallel with an inability to degrade and recycle damaged proteins that causes loss of mitochondrial protein homeostasis (proteostasis). The increase in oxidative damage that has been shown to occur with age might be explained by these two processes. While this accumulation of oxidative damage has often been cited as causative to ageing there are examples of model organisms that possess high levels of oxidative damage throughout their lives with no effect on lifespan. Interestingly, these same animals are characterised by an outstanding ability to maintain correct proteostasis during their entire life. ROS can damage critical components of the iron homeostasis machinery, while the efficacy of mitochondrial quality control mechanisms will determine how detrimental that damage is. Here we review the interplay between iron and organellar quality control in mitochondrial dysfunction and we suggest that a decline in mitochondrial proteostasis with age leaves iron homeostasis (where several key stages are thought to be dependent on proteostasis machinery) vulnerable to oxidative damage and other age-related stress factors. This will have severe consequences for the electron transport chain and TCA cycle (among other processes) where several components are acutely dependent on correct assembly, insertion and maintenance of iron-sulphur clusters, leading to energetic crisis and death. © 2014 Elsevier Inc
Regulation of lifespan by the mitochondrial electron transport chain: reactive oxygen species-dependent and reactive oxygen species-independent mechanisms
No full textSignificance: Aging is a consequence of the accumulation of cellular damage that impairs the capacity of an aging organism to adapt to stress. The Mitochondrial Free Radical Theory of Aging (MFRTA) has been one of the most influential ideas over the past 50 years. The MFRTA is supported by the accumulation of oxidative damage during aging along with comparative studies demonstrating that long-lived species or individuals produce fewer mitochondrial reactive oxygen species and have lower levels of oxidative damage. Recent Advances: Recently, however, species that combine high oxidative damage with a longer lifespan (i.e., naked mole rats) have been described. Moreover, most of the interventions based on antioxidant supplementation do not increase longevity, as would be predicted by the MFRTA. Studies to date provide a clear understanding that mitochondrial function regulates the rate of aging, but the underlying mechanisms remain unclear. Critical Issues: Here, we review the reactive oxygen species (ROS)-dependent and ROS-independent mechanisms by which mitochondria can affect longevity. We discuss the role of different ROS (superoxide, hydrogen peroxide, and hydroxyl radical), both as oxidants as well as signaling molecules. We also describe how mitochondria can regulate longevity by ROS-independent mechanisms. We discuss alterations in mitochondrial DNA, accumulation of cellular waste as a consequence of glyco- and lipoxidative damage, and the regulation of DNA maintenance enzymes as mechanisms that can determine longevity without involving ROS. Future Directions: We also show how the regulation of longevity is a complex process whereby ROS-dependent and ROS-independent mechanisms interact to determine the maximum lifespan of species and individuals
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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