1,720,956 research outputs found
Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning.
No full textBACKGROUND and AIMS: Ischemic preconditioning has been proved effective in
reducing ischemia/reperfusion injury during liver surgery. However, the
mechanisms involved are still poorly understood. Here, we have investigated the
role of phosphatidylinositol 3-kinase (PI3K) in the signal pathway leading to
hepatic preconditioning.
METHODS: PI3K activation was evaluated in isolated rat hepatocytes preconditioned
by 10-minute hypoxia followed by 10-minute reoxygenation.
RESULTS: Hypoxic preconditioning stimulated
phosphatidylinositol-3,4,5-triphosphate production and the phosphorylation of
PKB/Akt, a downstream target of PI3K. Conversely, PI3K inhibition by wortmannin
or LY294002 abolished hepatocyte tolerance against hypoxic damage induced by
preconditioning. PI3K activation in preconditioned hepatocytes required the
stimulation of adenosine A 2A receptors and was mimicked by adenosine A 2A
receptors agonist CGS21680. In the cells treated with CGS21680, PI3K activation
was prevented either by inhibiting adenylate cyclase and PKA with, respectively,
2,5-dideoxyadenosine and H89 or by blocking Galphai-protein and Src tyrosine
kinase with, respectively, pertussis toxin and PP2. H89 also abolished the
phosphorylation of adenosine A 2A receptors. However, the direct PKA activation
by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated
adenosine A 2A receptors may activate PI3K by coupling it with Galphai-protein
through Src. We also observed that, by impairing PI3K-mediated activation of
phospholypase Cgamma (PLCgamma), wortmannin and LY294002 blocked the downstream
transduction of preconditioning signals via protein kinase C (PKC) delta/
isozymes.
CONCLUSIONS: PI3K is activated following hepatocyte hypoxic preconditioning by
the combined stimulation of adenosine A 2A receptors, PKA, Galphai protein, and
Src. By regulating PKC-/delta-dependent signals, PI3K can play a key role in the
development of hepatic tolerance to hypoxia/reperfusion
Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning
No full textBACKGROUND & AIMS: Ischemic preconditioning has been proved effective in reducing ischemia/reperfusion injury during liver surgery. However, the mechanisms involved are still poorly understood. Here, we have investigated the role of phosphatidylinositol 3-kinase (PI3K) in the signal pathway leading to hepatic preconditioning.
METHODS: PI3K activation was evaluated in isolated rat hepatocytes preconditioned by 10-minute hypoxia followed by 10-minute reoxygenation.
RESULTS: Hypoxic preconditioning stimulated phosphatidylinositol-3,4,5-triphosphate production and the phosphorylation of PKB/Akt, a downstream target of PI3K. Conversely, PI3K inhibition by wortmannin or LY294002 abolished hepatocyte tolerance against hypoxic damage induced by preconditioning. PI3K activation in preconditioned hepatocytes required the stimulation of adenosine A 2A receptors and was mimicked by adenosine A 2A receptors agonist CGS21680. In the cells treated with CGS21680, PI3K activation was prevented either by inhibiting adenylate cyclase and PKA with, respectively, 2,5-dideoxyadenosine and H89 or by blocking Galphai-protein and Src tyrosine kinase with, respectively, pertussis toxin and PP2. H89 also abolished the phosphorylation of adenosine A 2A receptors. However, the direct PKA activation by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated adenosine A 2A receptors may activate PI3K by coupling it with Galphai-protein through Src. We also observed that, by impairing PI3K-mediated activation of phospholypase Cgamma (PLCgamma), wortmannin and LY294002 blocked the downstream transduction of preconditioning signals via protein kinase C (PKC) delta/ isozymes.
CONCLUSIONS: PI3K is activated following hepatocyte hypoxic preconditioning by the combined stimulation of adenosine A 2A receptors, PKA, Galphai protein, and Src. By regulating PKC-/delta-dependent signals, PI3K can play a key role in the development of hepatic tolerance to hypoxia/reperfusion
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
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
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