1,721,033 research outputs found
Independent Epileptiform Discharge Patterns in the Olfactory and Limbic Areas of the In Vitro Isolated Guinea Pig Brain During 4-Aminopyridine Treatment
No full textCarriero G, Uva L, Gnatkovsky V, Avoli M, de Curtis M. Independent epileptiform discharge patterns in the olfactory and limbic areas of the in vitro isolated guinea pig brain during 4-aminopyridine treatment. J Neurophysiol 103: 2728-2736, 2010. First published March 10, 2010; doi: 10.1152/jn.00862.2009. In vitro studies performed on brain slices demonstrate that the potassium channel blocker 4-aminopyridine (4AP, 50 mu M) discloses electrographic seizure activity and interictal discharges. These epileptiform patterns have been further analyzed here in a isolated whole guinea pig brain in vitro by using field potential recordings in olfactory and limbic structures. In 8 of 13 experiments runs of fast oscillatory activity (fast runs, FRs) in the piriform cortex (PC) propagated to the lateral entorhinal cortex (EC), hippocampus and occasionally to the medial EC. Early and late FRs were asynchronous in the hemispheres showed different duration [1.78 +/- 0.51 and 27.95 +/- 4.55 (SD) s, respectively], frequency of occurrence (1.82 +/- 0.49 and 34.16 +/- 6.03 s) and frequency content (20-40 vs. 40-60 Hz). Preictal spikes independent from the FRs appeared in the hippocampus/EC and developed into ictal-like discharges that did not propagate to the PC. Ictal-like activity consisted of fast activity with onset either in the hippocampus (n = 6) or in the mEC (n = 2), followed by irregular spiking and sequences of diffusely synchronous bursts. Perfusion of the N-methyl-D-aspartate receptor antagonist 2-amino-5-phosphonopentanoic acid (100 mu M) did not prevent FRs, increased the duration of limbic ictal-like discharges and favored their propagation to olfactory structures. The AMPA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (50 mu M) blocked ictal-like events and reduced FRs. In conclusion, 4AP-induced epileptiform activities are asynchronous and independent in olfactory and hippocampal-entorhinal regions. Epileptiform discharges in the isolated guinea pig brain show different pharmacological properties compared with rodent in vitro slices
Does interictal activity sustain seizures and epileptogenesis?
No full textInterictal spiking is seen in the EEG of epileptic patients betweenseizures. To date, the roles played by interictal events in seizureoccurrence and in epileptogenesis remain elusive. While interictalspikes may herald the onset of electrographic seizures, experimentaldata indicate that hippocampus-driven interictal events preventseizure precipitation. Even less clear than the role of interictalevents in seizure occurrence is whether and how interictal spikescontribute to epileptogenesis. Thus, while plastic changes withinlimbic neuronal networks may result from ongoing interictal activity,experimental evidence supports the view that epileptogenesisis accompanied by a decrease in hippocampus-driven interictalactivity
GABAergic synchronization in the limbic system and its role in the generation of epileptiform activity
No full textGABA is the main inhibitory neurotransmitter in the adult forebrain, where it activates ionotropic type A and metabotropic type B receptors. Early studies have shown that GABA(A) receptor-mediated inhibition controls neuronal excitability and thus the occurrence of seizures. However, more complex, and at times unexpected, mechanisms of GABAergic signaling have been identified during epileptiform discharges over the last few years. Here, we will review experimental data that point at the paradoxical role played by GABA(A) receptor-mediated mechanisms in synchronizing neuronal networks, and in particular those of limbic structures such as the hippocampus, the entorhinal and perirhinal cortices, or the amygdala. After having summarized the fundamental characteristics of GABA(A) receptor-mediated mechanisms, we will analyze their role in the generation of network oscillations and their contribution to epileptiform synchronization. Whether and how GABA(A) receptors influence the interaction between limbic networks leading to ictogenesis will be also reviewed. Finally, we will consider the role of altered inhibition in the human epileptic brain along with the ability of GABA(A) receptor-mediated conductances to generate synchronous depolarizing events that may lead to ictogenesis in human epileptic disorders as well. (C) 2011 Published by Elsevier Ltd
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
“Promozione dell’allattamento al seno” in M. De Curtis e V. Carnielli, “La Nutrizione del neonato”, Editeam, Cento (Fe), 2006
No full textBlood-brain barrier preservation in the in vitro isolated guinea pig brain preparation
No full textThe morphofunctional preservation of the blood-brain barrier (BBB) was evaluated in the isolated guinea pig brain maintained in vitro by arterial perfusion. Electron microscopy evaluation after 5 hr in vitro demonstrated that cerebral capillaries and BBB specializations in this preparation retain features compatible with structural integrity. BBB-impermeable and -permeable atropine derivatives arterially perfused to antagonize carbachol-induced fast oscillatory activity confirmed the functional preservation of the BBB in vitro. To study BBB function further, changes in extracellular K+ concentration during arterial perfusion of a high-K+ solution were measured with K+-sensitive electrodes positioned in the cortex and, as control, at the brain venous outlet, where the solution perfused through the brain arterial system was collected. After 5 hr in vitro, the [K+]o values measured during high-K+ perfusion in the piriform and entorhinal cortices were 5.02 ± 0.17 mM (mean ± SE) and 5.2 ± 0.21 mM, respectively (n = 6). Coperfusion of the high-K+ solution with the Na+/K+ pump blocker ouabain (10 M; n = 4) induced consistently spreading depression preceded by a rise in [K+]o. Finally, sporadic, isolated spots of extravasation of the fluorescent marker fluorescein isothiocyanate (FITC)-dextran preferentially circumscribed to deep cortical layers was observed in brains perfused with FITC-dextran after 5 hr in vitro. The study demonstrates that the in vitro isolated guinea pig brain is viable for studying cerebrovascular interactions and BBB permeability of compounds active in the central nervous system
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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