1,720,982 research outputs found
Functional differences in steroid sulfate uptake of organic anion transporter 4 (OAT4) and organic anion transporting polypeptide 2B1 (OATP2B1) in human placenta
No full textHuman trophoblasts depend on the supply of external precursors such as dehydroepiandrosterone-3-sulfate (DHEA-S) and 16 alpha-OH-DHEA-S for synthesis of estrogens. Recently, we have characterized the uptake of DHEA-S by isolated mononucleated trophoblasts and identified different transporter polypeptides involved in this process. Immunohistochemistry of 1st and 3rd trimester placenta detected organic anion transporter4 (OAT4) and organic anion transporting polypeptide 2B1 (OATP2B1, former name OATP-B) in cytotrophoblast membranes and at the basal surface of the syncytiotrophoblast, indicating that both transporter polypeptides are involved in placental uptake of foetal derived steroid sulfates. In the present study we have characterized and compared the kinetics of DHEA-S and estrone sulfate (E1S) uptake by these transporters stably expressed in FlpIn (TM)-HEK293 cells using the Flp recombinase-mediated site-specific recombination. Uptake of EIS by OAT4- and OATP2B1-transfected cells was highly increased compared to the non-transfected cells. In contrast, DHEA-S uptake was only highly increased in OAT4 (40 times), but only weakly enhanced in OATP2B1 cells. The uptake of DHEA-S and E, S by OAT4 was partly Na+-dependent (about 50%), whereas uptake of DHEA-S by OATP2B1 was Na+-independent. Kinetic analysis of the initial uptake rates of El S by OAT4 and OATP2B1 gave very similar values for K-m (about 20 mu M) and V-max (about 600 pmol/(min x mg protein)). In contrast, the affinity of DHEA-S towards OATP2B1 was about 10 times lower (Km > 200 mu M) then for OAT4 (K-m = 29 mu M). Our results suggest different physiological roles of the two transporter polypeptides in placental uptake of foetal derived steroid sulfates. OATP2B1 seems not to be involved in de novo synthesis of placental estrogens but may contribute to the clearance of estrogen sulfates from foetal circulation. (C) 2008 Elsevier Ltd. All rights reserved
1 Student Project: Replication of Buchanan, Summerville, Reb, & Lehmann (2016, JDM, Study 3)
No full textThis project is part of the Hagen Cumulative Science Project and replicates Buchanan, J., Summerville, A., Lehmann, J., & Reb, J. (2016). The Regret Elements Scale: Distinguishing the affective and cognitive components of regret. Judgment and Decision Making, 11(3), 275–28
1 Student Project: Replication of Buchanan, Summerville, Reb, & Lehmann (2016, JDM, Study 3)
No full textThis project is part of the Hagen Cumulative Science Project and replicates Buchanan, J., Summerville, A., Lehmann, J., & Reb, J. (2016). The Regret Elements Scale: Distinguishing the affective and cognitive components of regret. Judgment and Decision Making, 11(3), 275–28
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
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