1,720,976 research outputs found
Neuronal decay of functional and degeneration are prevented by processes secondary to membrane preservation
No full textREVERSIBILITY AND PREVENTION OF INTRASPINAL PEPTIDERGIC LOSS CAUSED BY SCIATIC-NERVE LESIONS
No full textWe have investigated the reversibility and prevention of peptidergic losses in the lumbar spinal cord caused by permanent resection of sciatic nerve. The lesion triggers a series of degenerative events involving the substance P sensory input as well as metenkephalin interneurons of the substantia gelatinosa. The degenerative processes are evident 10 days after sciatic nerve lesion and are gradually reversible as shown by radioimmunoassay and quantitative immunocytochemistry. Recovery begins 30 days postlesioning and full restoration is observed at 90 days. Serotonin (5-HT) turnover is markedly affected by sciatic nerve lesion as soon as 24 hr postlesioning, when 5-HT metabolism is enhanced, returning to control levels just preceding the peptide alterations; 5-HT metabolism then undergoes a transient period of hypoactivity which correlates with the beginning of the peptidergic restorative processes. Altogether these results, with previous observations showing that 5-HT depletion prevents metenkephalin interneurons degeneration triggered by the lesion (Di Giulio et al.: J Neurosci Res 18:443-448, 1987), suggest a role for 5-HT in the synaptic plasticity of the substantia gelatinosa of the spinal cord. The administration of gangliosides (10 or 50 mg/kg) to sciatic-nerve-lesioned animals fully prevented the metenkephalinergic degeneration without affecting the degenerative atrophy of the lesioned substance P sensory input
High opioid doses inhibit whereas low doses enhance neuritogenesis in PC12 cells
No full textExposure to opiates affects brain development, cell growth as well as in vitro cell differentiation [33,34]. Perinatal treatment with morphine has been reported to impair neuronal plasticity after neonatal lesion with 5,7-dihydroxytryptamine (5,7-DHT) [8]. This study has investigated the use of mu, delta and kappa opioid receptor ligands to examine the selective receptor mediated inhibition of PC12 neurite formation. Morphine and D-Ala(2),D-Leu(5)-enkephalin (DADLE) had a comparable inhibitory potency with a maximal effect at 1 mM concentration, while both naltrexone and naltrindole antagonized their effect at only 10 nM. D-Ala(2)-MePhe(4),Gly-ol(5)-enkephalin (DAMGO) showed only a transient inhibitory effect. The administration of 10 nM guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) prevented morphine inhibition. It is suggested that opiate inhibition of neuritogenesis may be mediated by a receptor with delta-like characteristics coupled to G proteins. On the other hand, the activation of this receptor with morphine at a very low concentration (1 pM) actually enhanced nerve growth factor (NGF) neurite promoting activity
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
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