1,720,962 research outputs found
Purinergic glio-endothelial coupling during neuronal activity: role of P2Y1 receptors and eNOS in functional hyperemia...
No full textImpairment of moment-tomoment adjustment of cerebral blood flow (CBF) via neurovascular coupling is thought to play a critical role in the genesis of cognitive impairment associated with aging and pathological conditions associated with accelerated cerebromicrovascular aging (e.g., hypertension, obesity). Although previous studies demonstrate that endothelial dysfunction plays a critical role in neurovascular uncoupling in these conditions, the role of endothelial NO mediation in neurovascular coupling responses is not well understood. To establish the link between endothelial function and functional hyperemia, neurovascular coupling responses were studied in mutant mice overexpressing or deficient in endothelial NO synthase (eNOS), and the role of P2Y1 receptors in purinergic glioendothelial coupling was assessed. We found that genetic depletion of eNOS (eNOS-/-) and pharmacological inhibition of NO synthesis significantly decreased the CBF responses in the somatosensory cortex evoked by whisker stimulation and by administration of ATP. Overexpression of eNOS enhanced NO mediation of functional hyperemia. In control mice, the selective and potent P2Y1 receptor antagonist MRS2179 attenuated both whisker stimulation-induced and ATP-mediated CBF responses, whereas, in eNOS-/- mice, the inhibitory effects of MRS2179 were blunted. Collectively, our findings provide additional evidence for purinergic glio-endothelial coupling during neuronal activity, highlighting the role of ATP-mediated activation of eNOS via P2Y1 receptors in functional hyperemia
The Role Of Long-Chain Polyunsaturated Fatty Acids And Resveratrol In Brain Nutrition: From Brain Development To Aging
Get PDFNutrients play a key role in central nervous system (CNS) development during fetal and early postnatal life, and their depletions can have devastating physiological results. One class of nutrients these nutrients are long-chain polyunsaturated fatty acids (LCPUFA), specifically docosohexaenoic acid (DHA) and arachidonic acid (ARA). These lipids accumulate rapidly in the CNS, and although neonates are able to produce them from precursors at low rates, optimal development depends on preformed sources from human breast milk or formula. We report a descriptive meta-analysis that considered 106 studies of humauin breast milk and found that mean (±SD) concentration of DHA in breast milk (by weight) is 0.32 ± 0.22% and that of AA is 0.47 ± 0.13%. This comprehensive analysis of breast-milk LCPUFA indicates a broad range of these lipids worldwide and serves as a guide for infant feeding. Dietary components with unknown or potentially deleterious effects remain important to characterize. While epidemiological data has implicated the role of trans fatty acid in increasing risk factors for heart disease, studies show that isolated trans fatty acids do not show atherogenic effects and remain difficult to accurately detect in mammalian tissues. We report these fatty acids in samples from patients with histologically-confirmed Alzheimer’s disease and normal aged subjects and show differences to be nonsignificant. The distributions of these trans fatty acids are consistent with their origin from diets that are a composite of dairy and partially hydrogenated vegetable oil trans sources. While a number of factors combine to result in decreased function and cognition in aging humans, the hypotheses that oxidation plays a major role in aging has garnered much attention. While many antioxidant-derived plant compounds have provided promise against aging in animal models, resveratrol, a grape polyphenol, has received significant attention for its antioxidant properties and action as a calorie-restriction mimetic. We fed dietary resveratrol to wild-type and transgenic Alzheimer’s Disease mice and show a number of targets specific to the pathophysiology of Alzheimer’s, specifically transthyretin, drebrin, and glycogen synthase kinase-3, are positively influenced. These data suggest new mechanisms whereby this polyphenol putatively exerts protective effects in aging and beyond
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
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