1,720,986 research outputs found
A new and sensitive fluorimetric method for the determination of aminoquinolines binding and internalization in human RBC
No full textMetabolic modification of erythrocytes in malaria : modulation of G3PDH activity and Tyr-phosphorilation of Band 3 in human erytrhrocytes treated with FP IX
No full textNovel 4-aminoquinolines : determination of binding and internalization by a new fluorimetric method and effects on human RBC
No full textEffect of circulating free heme on plasma arginase activity and L-arginine cellular influx
No full textSevere falciparum malaria is associated with high levels of free heme [Fe(III)-protoporphyrin IX, FP], hypoargininemia and low nitric oxide (NO). Hypoargininemia can be partially explained by the increased level of plasma arginase due to the disease-induced hemolysis, but its precise cause is unknown.
Objectives. Investigate whether FP can affect the membrane transport of arginine (ARG) and/or the activity of plasma or red blood cell (RBC) arginase, therefore limiting ARG bioavailability for NO production.
Design and Methods. ARG transport was evaluated in RBC by measurement of influx of radiolabeled ARG and resolved into the saturable transport components y+ and y+L by selective inhibition with 2 mM N-ethylmaleimide or 1 mM leucine. respectively. Arginase activity was evaluated after pre-treatment of RBC or cell-free extract with FP in different experimental conditions and expressed as mol urea produced/gr Hb.
Results. FP impairs the influx of ARG into RBC in a dose dependent manner with a more pronounced effect on the transport system y+L. FP-treated RBC show an enhancement of the arginase activity but experiments performed in different experimental conditions have shown that arginase activation is not simply related to oxidative modifications induced by the porphyrin
Conclusions: impairment of ARG influx and activation of arginase could limit ARG availability for NO production by RBC NOS. Additionally, release of a more active arginase by damaged RBC during intravascular hemolysis could worsen hypoargininemia, reducing ARG availability for NO production also in endothelial cells
Modulation of L-Arginine metabolism and bioavailability by free plasma heme
No full textSevere falciparum malaria is associated with high levels of free heme [Fe(III)-protoporphyrin IX, FP], hypoargininemia and low nitric oxide (NO). Hypoargininemia can be partially explained by the increased level of plasma arginase due to the disease-induced hemolysis, but its precise cause is unknown.
The aim of this work was to investigate whether FP can affect the membrane transport of arginine (ARG) and/or the activity of plasma and red blood cell (RBC) arginase, therefore limiting ARG bioavailability for NO production.
Design and Methods. ARG transport was evaluated in human RBC by measurement of influx of radiolabeled ARG and resolved into the saturable transport components y+ and y+L by selective inhibition of the two systems with 2 mM N-ethylmaleimide or 1 mM leucine. respectively. Arginase activity was evaluated after pre-treatment of RBC or cell-free extract with FP in different experimental conditions and expressed as mol urea produced/gr Hb.
Results. FP impairs the influx of ARG into RBC in a dose dependent manner with a more pronounced effect on the transport system y+L. FP-treated RBC show an enhancement of the arginase activity. Experiments performed in different experimental conditions have shown that arginase activation is not simply related to oxidative modifications induced by the porphyrin
Conclusions: impairment of ARG influx and activation of arginase could limit ARG availability for NO production by RBC NOS. Additionally, release of a more active arginase by damaged RBC during intravascular hemolysis could worsen hypoargininemia, reducing ARG availability for NO production also in endothelial cells
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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