1,720,970 research outputs found
Identification and partial characterization of cAMP-phosphodiesterases in the ciliate Euplotes raikovi.
Get PDFIn the ciliate Euplotes raikovi, two specific isoforms of cAMP- dependent phosphodiesterases were identified, one in the soluble and the other in the particulate fraction of the cell. Their activity was shown to be stimulated by Mg2+, insensitive to Ca2+ and cGMP, and scarcely inhibited by theophylline and 3-isobutyl-1-methyl-xanthine. They appear to be related to some phosphodiesterases of class II of other unicellular organisms in their biochemical features, and their enzymatic activity is up-regulated by elevation of intracellular cAMP level similarly to PDE-4 isoforms of mammals
Cross-talk between the autocrine (mitogenic) pheromone loop of the ciliate Euplotes raikovi and the intracellular cyclic AMP concentration
Get PDFCell type-specific protein signals, called pheromones, are constitutively secreted by Euplotes raikovi and bound back in autocrine fashion, with a positive effect on the vegetative (mitotic) cell growth. In cells growing suspended with their secreted pheromone, it was found that any interruption of this autocrine signaling loop was immediately followed by an effective enhancement of the basal intracellular cyclic AMP (cAMP) level. To establish a cause-effect relationship between these pheromone-induced variations in the cytoplasmic cAMP level and cell growth, cells ready to pass from a resting stage to a new growth cycle were conditioned either to incorporate a cAMP analog resistant to phosphodiesterase degradation, or to utilize cAMP released (following cell irradiation) from incorporated “caged” cAMP. Cells responded at every induced increase in their basal cAMP level by markedly decreasing their commitment to start a new growth cycle. It was deduced that the autocrine signaling of E. raikovi pheromones involves cAMP as inhibitor of its mitogenic activity
A Novel Protein Kinase from the Ciliate Euplotes raikovi with Close Structural Identity to the Mammalian Intestinal and Male-Germ Cell Kinases: Characterization and Functional Implications in the Autocrine Pheromone Signaling Loop
No full textIn the free-living ciliate Euplotes raikovi, we identified (and designated as Er-MAPK1) a protein kinase of 631 amino acids, that appears to be constantly phosphorylated in cells which are in growth stage and interact in autocrine fashion with their water-soluble signal pheromones. Er-MAPK1 is specified by a gene that requires aþ1 translational frame-shift to be expressed. Its amino-terminal region represents a canonical catalytic domain and carries an activation loop distinctive of the mitogenactivated protein kinases, with the Thr-Asp-Tyr motif deputed to be site of double phosphorylation. In contrast, the carboxy-terminal region appears to be structurally unique. It shows a strongly basic amino acid composition, is very rich in glycine repetitions, and contains a bipartite signal for translocation of Er-MAPK1 into the nucleus
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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