1,720,957 research outputs found
GLUCOCORTICOIDS DEPRESS ACTIVITY-DEPENDENT EXPRESSION OF BDNF MESSENGER-RNA IN HIPPOCAMPAL-NEURONS
No full textGlucocorticoid hormones are important regulators of brain development and ageing, and can impair the capacity of hippocampal neurones to survive various neurological insults. Here we show that dexamethasone, a synthetic glucocorticoid, prevents activity-dependent increases of brain-derived neurotrophic factor (BDNF) mRNA in cultures of rat hippocampal neurones. In situ hybridization was used to evaluate the levels of BDNF mRNA. Up-regulation of BDNF mRNA triggered by depolarization with high potassium, or exposure to the glutamate receptor agonist kainic acid, resulted both from higher levels of expression in neurones and from new recruitment of cells. These data suggest that the known ability of glucocorticoids to exacerbate neuronal injury following ischaemia and other metabolic insults could be due to antagonism of regulatory mechanisms governing neurotrophin levels in the brain
COLOCALIZATION OF LOW-AFFINITY AND HIGH-AFFINITY NGF RECEPTORS ON PC12 CELLS, C6 GLIOMA-CELLS AND DORSAL-ROOT GANGLION NEURONS
No full textThe biological responsiveness of neural cells to nerve growth factor (NGF) appears to require expression and ligand binding to both the low-affinity NGF receptor (LNGFR) and the proto-oncogene product trk, the latter being a receptor tyrosine kinase. Immunolocalization of the LNGFR and the high-affinity component of the NGF receptor, trk (HNGFR) was studied by electron microscopic morphometric analysis on cultured PC12 pheochromocytoma cells, C6 glioma cells and neonatal rat dorsal root ganglia neurons using a double immunogold labeling technique. Two receptor-specific antibodies, anti-LNGFR monoclonal antibody 192-IgG and a polyclonal antibody against the 14 carboxy-terminal amino acids of the Trk protein, were utilized in conjunction with immunoglobulin conjugated to colloidal gold particles of different sizes. All cells treated with NGF (50 ng/ml) displayed significant colocalization of LNGFR/HNGFR-like immunoreactivity. Gold particles associated with LNGFR (LNGFR-like immunoreactivity) were frequently seen near 2 or 3 (or more) particles delineating the HNGFR on all cell surfaces. Positive Trk-like immunoreactivity (HNGFR) thus seems to localize in close proximity to LNGFRs in at least these cell types
INTERACTION OF GANGLIOSIDE GM1 WITH THE B-SUBUNIT OF CHOLERA-TOXIN MODULATES INTRACELLULAR FREE CALCIUM IN SENSORY NEURONS
No full textThe B subunit of cholera toxin, which binds specifically to GM1 ganglioside on cell surfaces, has previously been shown to modulate intracellular calcium levels and growth in several cell types. To explore a role for such changes in calcium in the growth regulatory function of cell-associated GM1 in neurons, dissociated neurons from chicken embryonic day 8 dorsal root ganglia were exposed to the B subunit. To enhance sensitivity to B subunit, some neurons were also enriched with added GM1 (100 microM) and then exposed to B subunit. Incubation of naive cultures with 1 microgram/ml of the B subunit was sufficient to produce modest increases in intracellular free calcium above basal levels in a minor percentage of cells for at least 5 min, as measured by fura-2 fluorescence imaging. Pretreatment of the cells with GM1 for 48 hr increased even further the elevations in intracellular free calcium and the percentage of responding neurons observed after B subunit exposure. These increases in intracellular calcium required the presence of external Ca2+, but were not inhibited by calcium channel blockers. Such changes in calcium were accompanied by fine alterations in morphology affecting mostly the branching of neurites and were more pronounced in the presence of GM1. However, the morphological changes did not result in altered neurofilament protein expression. Immunogold electron microscopy using anti-choleragenoid depicted extensive aggregations of immunoreactive gold particles on neuronal surfaces, which were more extensive in cells treated with GM1. The results demonstrate that cell incorporated GM1 may modulate calcium fluxes, perhaps accounting for the growth regulatory functions of GM1 in both neuronal and other cell types
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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