1,720,962 research outputs found
Inhibition of the mevalonate pathway in C. elegans: Consequences and implications
No full textThe mevalonate pathway in human is responsible for the synthesis of cholesterol and other important biomolecules such as coenzyme Q (a component of the electron transport chain in mitochondria), dolichols (important for N-linked glycosylation of proteins) and isoprenoids (important for the membrane association of small GTPases). This thesis concerns novel findings about the effect of statin on the mevalonate pathway using C. elegans as a model organism. Statins are cholesterol-lowering drugs that inhibit HMG-CoA reductase, which is the rate- limiting enzyme of the mevalonate pathway, hence limiting the synthesis of cholesterol and other products from this pathway. C. elegans is a particularly powerful model to study the effect of statin on the non-cholesterol outputs of the mevalonate pathway because this pathway is well conserved in worms except for the key fact that the enzymes required for the synthesis of cholesterol are absent. We characterized a hmgr-1(tm4368) mutant, which lacks HMG-CoA reductase, and showed that its phenotypes recapitulate the effect of statin on C. elegans but in a more severe form. We also showed that inhibition of protein prenylation is a critical consequence of mevalonate pathway inhibition in C. elegans. Since inhibition of the mevalonate pathway, via statins or hmgr-1 mutation causes growth arrest and sterility, it is relatively easy to screen for resistant mutant. We screened ∼150,000 mutagenized haploid genomes and isolated four statin-resistant mutants that carried gain-of- function mutations in atfs-1, a positive regulator of the mitochondrial-unfolded protein response (UPRmt). Interestingly, preinduction of this response using ethidium bromide or paraquat in wild type worms or mammalian cells also conferred resistance to statin. Our observations suggest that statin resistance through maintenance of mitochondrial homeostasis is conserved among species, and that the lethal effect of statins in C. elegans are caused primarily through impaired protein prenylation leading to mitochondria dysfunction. We also isolated an additional statin-resistant mutant that carried a partial loss-of-function mutation in nduf-7, which encodes a key component of the mitochondrial transport chain complex1 (ETC-1). This mutation also activates the UPRmt and prolonged life span through production of ROS. Interestingly, the gene ced-4 is required for lifespan extension in the nduf-7(et19) mutant but not for UPRmt induction or resistance to statin. Keywords: C. elegans, mevalonate, atfs-1, UPRmt, prenylation, nduf-7, ced-4. ISBN: 978-91-628-9514-
Inhibition of the mevalonate pathway in C. elegans: Consequences and implications
No full textThe mevalonate pathway in human is responsible for the synthesis of cholesterol and other important biomolecules such as coenzyme Q (a component of the electron transport chain in mitochondria), dolichols (important for N-linked glycosylation of proteins) and isoprenoids (important for the membrane association of small GTPases). This thesis concerns novel findings about the effect of statin on the mevalonate pathway using C. elegans as a model organism.
Statins are cholesterol-lowering drugs that inhibit HMG-CoA reductase, which is the rate- limiting enzyme of the mevalonate pathway, hence limiting the synthesis of cholesterol and other products from this pathway. C. elegans is a particularly powerful model to study the effect of statin on the non-cholesterol outputs of the mevalonate pathway because this pathway is well conserved in worms except for the key fact that the enzymes required for the synthesis of cholesterol are absent. We characterized a hmgr-1(tm4368) mutant, which lacks HMG-CoA reductase, and showed that its phenotypes recapitulate the effect of statin on C. elegans but in a more severe form. We also showed that inhibition of protein prenylation is a critical consequence of mevalonate pathway inhibition in C. elegans.
Since inhibition of the mevalonate pathway, via statins or hmgr-1 mutation causes growth arrest and sterility, it is relatively easy to screen for resistant mutant. We screened ∼150,000 mutagenized haploid genomes and isolated four statin-resistant mutants that carried gain-of- function mutations in atfs-1, a positive regulator of the mitochondrial-unfolded protein response (UPRmt). Interestingly, preinduction of this response using ethidium bromide or paraquat in wild type worms or mammalian cells also conferred resistance to statin. Our observations suggest that statin resistance through maintenance of mitochondrial homeostasis is conserved among species, and that the lethal effect of statins in C. elegans are caused primarily through impaired protein prenylation leading to mitochondria dysfunction.
We also isolated an additional statin-resistant mutant that carried a partial loss-of-function mutation in nduf-7, which encodes a key component of the mitochondrial transport chain complex1 (ETC-1). This mutation also activates the UPRmt and prolonged life span through production of ROS. Interestingly, the gene ced-4 is required for lifespan extension in the nduf-7(et19) mutant but not for UPRmt induction or resistance to statin.
Keywords: C. elegans, mevalonate, atfs-1, UPRmt, prenylation, nduf-7, ced-4. ISBN: 978-91-628-9514-
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
- …
