1,720,955 research outputs found
Different hepatic uptake of tetra- and di-bromosulfophthalein in rat: Role of hydrophobicity, binding to plasma proteins and affinity for plasma membrane carrier protein.
No full textThe relative role of hydrophobicity, binding to plasma proteins and affinity for one of the plasma membrane transport proteins in the hepatic uptake of 3,4,5,6-tetra- (BSP) and 3,6-di- (DBSP) bromosulfophthalein was investigated in the rat. In terms of physicochemical characteristics, the two molecules show different pKa values and degrees of hydrophobicity, as determined from the n-octanol:water partition coefficient. In the intact animal, the plasma clearance and the plasma removal rate after a dose of 1.5 mumol/kg i.v. were significantly (P < 0.001) faster for BSP than DBSP, while no difference was found in the plasma distribution volume. The dissociation constant (Kd) of the high affinity binding sites of plasma proteins also differed for the two anions, being significantly lower for BSP than DBSP (0.95 +/- 0.02 vs 1.44 +/- 0.14 microM, P < 0.001). [35S]BSP uptake by liver plasma membrane vesicles was saturable with an apparent Km of 5.20 +/- 0.80 microM, and was competitively inhibited by DBSP (Ki 18.2 +/- 1.2 microM) indicating a common uptake system. The Kd value for binding of the organic anions to purified bilitranslocase, a plasma membrane protein involved in the electrogenic transport of pthaleins, was also significantly lower for BSP than DBSP (1.10 +/- 0.12 vs 3.02 +/- 0.27 microM, N = 3, P < 0.001), indicating a higher affinity of the former ligand for the carrier protein. No difference was observed in the capacity of the high affinity binding sites (32 +/- 3 vs 33 +/- 3 nmol/mg protein, BSP and DBSP, respectively). These data indicate that BSP and DBSP are two different cholephilic organic anions which share a common uptake mechanism, at least partly mediated by bilitranslocase. The greater affinity of BSP than DBSP for the carrier protein may account for the faster plasma disappearance rate of BSP observed in vivo, in spite of the higher plasma protein binding
Reversal of ethinylestradiol induced cholestasis by Epomediol in rat. The role of liver plasma membrane fluidity.
No full textEpomediol (EPO) is a synthetic terpenoid compound shown to be active in increasing bile flow and some enzymatic activities of liver plasma membranes in the rat. The possible effect of EPO treatment in the ethinyl-estradiol (EE) induced cholestasis in the rat was investigated by measuring the hepatic transport of sulfobromophthalein (BSP) (plasma clearance and biliary secretion) and bile flow. Liver plasma membrane fluidity was also determined by the steady state fluorescence polarization (P) of diphenylhexatriene (DPH). EE administration (5 mg/kg s.c. for 5 days) was followed by a significant, comparable reduction (P less than 0.001) in BSP plasma clearance and biliary excretion and in bile flow. Intraperitoneal administration of EPO (100 mg/kg) to EE-treated rats restored both parameters of BSP transport, as well as bile flow, to control values. Liver plasma membrane fluidity was markedly (P less than 0.01) decreased by EE administration with a concomitant reduction (P less than 0.01) in Na+/K+-ATPase activity. EPO administration significantly increased membrane fluidity to values higher either to cholestatic (P less than 0.05) or control (P less than 0.05) animals. On the contrary, EPO did not influence Na+/K+-ATPase activity in either EE-treated or control animals. These data indicate that EPO fully reverses the impairments of BSP transport and bile flow induced by EE, possibly by reversing the decrease in liver plasma membrane fluidity induced by the synthetic estrogen. On the contrary, the EE-mediated decrease in Na+/K+-ATPase activity was not reversed by EPO
Bilitranslocase is the protein responsible for the electrogenic movement of sulfobromo-phthalein in plasma membrane vesiscles from rat liver: immuno chemical evidence using mono and poly clonal antibodies
No full textMonoclonal antibodies raised against bilitranslocase, may display either inhibitory or enhancing activity on the electrogenic transport of sulfobromophthalein, evoked in rat liver plasma-membrane vesicles by the addition of valinomycin in the presence of K+. In both cases, the target protein is identified with a 37 kDa band in SDS-mercaptoethanol gel electrophoresis of solubilized membranes. The electrophoretically homogeneous protein isolated by ion-exchange chromatography, corresponds in all respects to the 37 kDa protein band of bilitranslocase, obtained in the past by different techniques. Using this protein as antigen, a polyclonal monospecific antibody preparation has been obtained. As expected, the antibody preparation inhibits the electrogenic movement of sulfobromophthalein in plasma membrane vesicles from rat liver. It is concluded that the 37 kDa protein of bilitranslocase is at least a necessary component of the transport system involved in the sulfobromophthalein movement in plasma 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
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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