1,721,001 research outputs found
John Logan Smith N696 Plane, A
No full textA N696 Plane with the words John Logan Smith written on it.https://digitalcommons.usf.edu/gandy_commercial/1267/thumbnail.jp
John Logan Smith N696 Plane, B
No full textA N696 Plane with the words John Logan Smith written on it.https://digitalcommons.usf.edu/gandy_commercial/1268/thumbnail.jp
Expression and inhibitor studies of Ca2+-ATPases
No full textMany compounds inhibit the function of the Ca'^-ATPase of the sarcoplasmic reticulum (SERCA). These are generally hydrophobic compounds containing -OH groups. Curcumin is shown to be an inhibitor of the Ca^'-ATPase. Studies of the effects of mixtures of inhibitors show that 2,5-di(propyI)-l,4-benzohydroquinone and 2,5-di(fg/7- butyl)-] ,4-benzohydroquinone (BHQ) bind to the same site on the ATPase, but that the binding site for BHQ is separate lErom that for butylatedhydroxy toluene, ellagic acid, diethylstilbestrol (DBS), curcumin and nonylphenol, and that the binding site for curcumin is separate fi-om that 6)r ellagic acid and DES. The presence of BHQ, DES, ellagic acid and nonylphenol increase the a@inity of the ATPase for curcumin, suggesting that binding of one inhibitor results in a change in the ATPase to a conformation with higher affinity for the second inhibitor. In QT-6 cells curcumin prevents the release of calcium normally seen on addition of the Ca'-ATPase inhibitor trilobilide, suggesting that curcumin blocks the inositol sensitive calcium release channel (IP3R). In sarcoplasmic reticulum it was shown that curcumin reduces the rate of slippage on the Ca"-ATPase and so increases calcium accumulation into SR vesicles, despite being an inhibitor of ATPase function. SERCA and SERCA-GFP have been expressed in Cos-7 cells. A chimera between SERCA and a Ca"-ATPase from Heliothis virescens, HVSERCA, showed higher levels of expression in Cos-7 cells than HVSERCA. SERCA and HVSERCA have been expressed in S.cerexnsiae and comparative inhibitor studies using this system have shown that trilobilide inhibits SERCA but not HVSERCA, whereas BHQ inhibits both of these pumps.</p
Curcumin, a molecule that inhibits the Ca2+-ATPase of sarcoplasmic reticulum but increases the rate of accumulation of Ca2+
No full textCurcumin, an important inhibitor of carcinogenesis, is an inhibitor of the ATPase activity of the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum (SR). Inhibition by curcumin is structurally specific, requiring the presence of a pair of -OH groups at the 4-position of the rings. Inhibition is not competitive with ATP. Unexpectedly, addition of curcumin to SR vesicles leads to an increase in the rate of accumulation of Ca2+, unlike other inhibitors of the Ca2+-ATPase that result in a reduced rate of accumulation. An increase in the rate of accumulation of Ca2+ is seen in the presence of phosphate ion, which lowers the concentration of free Ca2+ within the lumen of the SR, showing that the effect is not passive leak across the SR membrane. Rather, simulations suggest that the effect is to reduce the rate of slippage on the ATPase, a process in which a Ca2+-bound, phosphorylated intermediate releases its bound Ca2+ on the cytoplasmic rather than on the lumenal side of the membrane. The structural specificity of the effects of curcumin on ATPase activity and on Ca2+ accumulation is the same, and the apparent dissociation constants for the two effects are similar, suggesting that the two effects of curcumin could follow from binding to a single site on the ATPase. <br/
Evidence for a global inhibitor-induced conformation change on the Ca2+-ATPase of sarcoplasmic reticulum from paired inhibitor studies
No full textThe Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum is inhibited by a variety of hydrophobic, hydroxy-containing molecules. A kinetic method has been used to study competition between binding of pairs of inhibitors to the ATPase. The presence of 2,5-di-tert-butyl-1,4-dihydroxybenzene (BHQ) decreases the affinity of the ATPase for 2,5-dipropyl-1,4-dihydroxybenzene (PHQ), suggesting that PHQ and BHQ bind to the same site on the ATPase. In contrast, the presence of BHQ increases the affinity of the ATPase for curcumin and vice versa. This suggests that BHQ and curcumin bind to separate sites on the ATPase and that binding of the first inhibitor to the ATPase results in a change to a conformation with higher affinity for the second inhibitor. This is consistent with previous experiments with BHQ and thapsigargin suggesting a conformation change on inhibitor binding, E2 + I E2I E2AI, with E2AI having a higher affinity for the second inhibitor than E2. The affinity for BHQ is also increased by binding of diethylstilbesterol, ellagic acid, or nonylphenol, and the affinity for curcumin is also increased by ellagic acid. These results showing that binding of a variety of inhibitors of very different structures all result in a general increase in inhibitor affinity point to a global conformational change on the Ca2+-ATPase caused by inhibitor binding, as well as any local, inhibitor-specific changes in conformation
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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