1,721,000 research outputs found
The septal-hippocampal cholinergic pathway: Role in antagonism of pentobarbital anesthesia and regulation by various afferents
No full textEarlier studies have demonstrated that pentobarbital reduces the turnover rate of acetylcholine (ACh) in hippocampus and that this effect may be mediated via the septal-hippocampal cholinergic pathway. Moreover, the narcosis associated with the administration of pentobarbital may be reversed by intraseptal injection of such chemically diverse compounds as bicuculline, a potent γ-aminobutyric acid antagonist; thyrotropin-releasing hormone, a neuroactive tripeptide; and kainic acid, a rigid analog of glutamate. To determine whether or not these three compounds modulate the metabolism of ACh in hippocampus, they have been injected intraseptally in pentobarbital-pretreated rats and the turnover rate of ACh has been determined by gas chromatography-mass fragmentography. Pentobarbital produces a dose-dependent decrease in the turnover rate of ACh in cortex and hippocampus but not in striatum. The effect appears to be maximum at 30 min and returns to normal within 15 min of recovering the righting reflex. Slow local infusion of either bicuculline or thyrotropin-releasing hormone into the septum reverses the pentobarbital-induced narcosis and antagonizes the pentobarbital-induced decrease in the hippocampal turnover rate of ACh. Administration of kainic acid into the lateral, but not the medial, septum reduces specifically the glutamic acid decarboxylase activity in the ipsilateral septum without altering the choline acetyltransferase activity or the turnover rate of ACh in the hippocampus. Moreover, kainic acid injected into the lateral septum antagonizes the pentobarbital narcosis and reverses the pentobarbital-induced decrease in the ACh turnover rate in the ipsilateral hippocampus, but not in the contralateral hippocampus. It appears that all three compounds antagonize the pentobarbital-induced decrease in hippocampal ACh turnover rate and the pentobarbital narcosis by modulating neurons in the lateral septum, presumably through an action on the GABAergic interneurons
Increase in Exogenous Choline Fails to Elevate the Content or Turnover Rate of Cortical, Striatal, or Hippocampal Acetylcholine
No full textAbstract: The present experiments were designed to test whether increasing the availability of choline to rat brain increases the rate of acetylcholine synthesis in that organ. The content of choline and acetylcholine and the turnover rate of acetylcholine in striatum, hippocampus, and cerebral cortex were measured following changes in dietary choline, intraperitoneal choline, or intravenous infusion of choline. Increasing plasma choline caused some increase in tissue choline but did not increase acetylcholine levels nor acetylcholine turn‐over rate in any of the areas of brain studied. Indeed, in hippocampus, choline decreased the turnover rate of acetylcholine. Copyright © 1982, Wiley Blackwell. All rights reserve
Increased choline availability fails to increase acetylcholine turnover rate in rat brain areas
No full textCheney, D. L. and Seyfarth, R. M. — How Monkeys See the World. Inside the Mind of Another Species. University of Chicago Press, Chicago, 1990
No full textBourlière François. Cheney, D. L. and Seyfarth, R. M. — How Monkeys See the World. Inside the Mind of Another Species. University of Chicago Press, Chicago, 1990. In: Revue d'Écologie (La Terre et La Vie), tome 46, n°3, 1991. pp. 293-294
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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