1,721,104 research outputs found
Synaptic protein phosphorylation changes in animals exposed to neurotoxicants during development
No full textProtein phosphorylation represents a key process by which neuronal function is regulated by first messengers interacting with extracellular membrane receptors. Protein kinases transfer the phosphate group from ATP to neuron specific proteins and phosphatases, catalyzing the removal of the phosphate group, shut off the signal by restoring the reactive form of the protein. These phosphorylation processes seem to be particularly important in long-term changes which follow sustained activation of neurons. Particular importance has been given to the Calcium/phospholipid-dependent protein kinase (PKC) as the molecular mechanism in synaptic plasticity associated with learning and memory. We have studied the changes of PKC activity in an animal model of impaired cognitive functions as a consequence of an exposure during embryonic life to an antimitotic agent, methylazoxy-methanol acetate (MAM). Treatment at gestational day (GD) 15 results in offspring showing a dose-dependent reduction in the size of cortex and hippocampus. When adult, these animals show impairments in several tests for learning and memory. In hippocampal slice preparations from MAM-treated rats, Long-Term Potentiation could not be induced in the CA1 region, the area affected by the treatment. However, in the hippocampal dentate gyrus, an area not affected by the treatment, LTP could be induced. Moreover, these animals show area-specific changes in the phosphorylation state of the protein B-50/GAP-43, a well characterized neuron specific substrate for PKC. By changing the time of MAM exposure, i.e. at GD19, a different pattern of brain damage occurs and this results both in a different pattern in behavior and B-50 phosphorylation. All these data indicate that changes in protein phosphorylation of specific substrates for PKC are markers of alteration in synaptic plasticity associated with neurotoxic insults to the developing CNS
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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