1,721,023 research outputs found
FUNCTION OF NAD GLYCOHYDROLASE IN ADP-RIBOSE UPTAKE FROM NAD BY HUMAN ERYTHROCYTES
No full textThe function of the ectoenzyme NAD glycohydrolase (NADase) in ADP-ribose uptake from extracellular NAD was studied in human erythrocytes that express relatively high NADase activity (adult erythrocytes) and erythrocytes expressing very low activity (newborn erythrocytes). The rates of ADP-ribose uptake from NAD in human erythrocytes were correlated with their NADase activities. In contrast, there was no significant difference in the rates of ADP-ribose uptake among these cells when incubated with ADP-ribose. These results indicate that ecto-NADase may have a role as supplier of ADP-ribose for its uptake into the cells and that the cleavage of NAD by NADase is necessary for the ADP-ribose uptake by human erythrocytes. From ADP-ribose uptake studies at 37-degrees-C a K(m) of 0.7 +/- 0.05 muM and a V(max) of 2.04 +/- 0.1 pmol/min per mul cell water was found for the uptake of [H-3]ADP-ribose. The thiol-reactive reagents p-chloromercuribenzene sulfonic acid and N-ethylmaleimide inhibited the uptake ADP-ribose with IC50 values of 50 +/- 4 and 750 +/- 25 mM, respectively. Since efflux of [H-3]ADP-ribose was negligible, the ADP-ribose transport system appears to be unidirectional. The unidirectionality was supported by the evidence that transported ADP-ribose was rapidly degraded to AMP which is impermeable to the membrane.
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
Significance of ecto-cyclase activity of CD38 in insulin secretion of mouse pancreatic islet cells
No full textCyclic ADP-ribose (cADPR), a product of CD38, has a second messenger role for in intracellular Ca2+ mobilization from microsomes of pancreatic islets as well as from a variety of other cells. ADP-ribosylation of CD38 by ecto-mono ADP-ribosyltransferase in activated T cells results in apoptosis as well as inactivation of its activities. We, therefore, examined the effect of ADP-ribosylation of CD38 in mouse pancreatic islet cells. NAD-dependent inactivation and ADP-ribosylation of CD38, intracellular concentrations of cADPR and Ca2+ and insulin secretion were measured following incubation of mouse pancreatic islet cells with NAD, ADP-ribosylation of CD38 inactivated its ecto-enzyme activities, and abolished glucose-induced increase of cADPR production, intracellular concentration of Ca2+, and insulin secretion. Taken together, ecto-cyclase activity of CD38 to produce intracellular cADPR seems to be indispensable for insulin secretion. (C) 2001 Academic Press.
NF-κB-dependent lymphocyte hyperadhesiveness to synovial fibroblasts by hypoxia and reoxygenation:: potential role in rheumatoid arthritis
No full textHypoxia/reoxygenation has been incriminated as a major factor in the pathogenesis of ischemia/reperfusion injury in various ischemic diseases such as rheumatoid arthritis (RA). In this study, we have investigated the effect of hypoxia/ reoxygenation on the expression of intercellular adhesion molecule-1 (ICAM-1) in synovial fibroblasts and adherence of lymphocytes to synovial fibroblasts. Hypoxia/reoxygenation strongly activated nuclear factor-kappaB (NF-kappaB) in synovial fibroblasts to the levels produced by phorbol 12-myristate 13-acetate and caused lymphocyte hyperadhesiveness to synovial fibroblasts as well as up-regulation of ICAM-1, both of which were completely blocked by a NF-kappaB antagonist (pyrrolidine dithiocarbamate). These results indicate that hypoxia/reoxygenation has a major role in sequestration of inflammatory cells to synovium. mediated by the activation of NF-kappaB. Our data suggest that hypoxia/ reoxygenation could be an important target for the development of new, therapeutic strategies in RA. J. Leukoc. Biol. 73: 525-529; 2003.
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