1,720,990 research outputs found
Preferential potentiation of fast-releasing synaptic vesicles by cAMP at the calyx of Held
No full textQuantitative analysis of calcium-dependent vesicle recruitment and its functional role at the calyx of held synapse
No full textRecruitment of release-ready vesicles at synapses is one of the important factors, which determine dynamic properties of signaling between neurons in the brain. It has been shown that the rate of vesicle recruitment is accelerated by strong synaptic activity. An elevated concentration of calcium ions in the presynaptic terminal ([Ca2+]i) has been proposed to be responsible for this effect. However, the precise relationship between [Ca2+]i and recruitment has not been established yet, and the functional consequences of accelerated recruitment during synaptic activity have not been quantified experimentally. To probe the intracellular Ca2+ dependence of vesicle recruitment and to examine its functional role during trains of action potential (AP)-like stimuli, we monitored [Ca2+]i and synaptic responses simultaneously with paired recordings at the calyx of Held synapse. We found that a distinct, rapidly releasing vesicle pool is replenished with a rate that increases linearly with [Ca2+]i, without any apparent cooperativity. The slope factor for this increase is ∼1 pool/(μm·s). Blocking Ca2+-dependent recruitment specifically with a calmodulin binding peptide revealed that the steady-state EPSCs during 100 Hz AP-like trains were maintained through this Ca2+-dependent recruitment mechanism. Using a simple model of vesicle dynamics, we estimated that the recruitment rate accelerated 10-fold during the steady-state compared with the rate at resting [Ca2+]i. We could also demonstrate an approximate sixfold increase in release probability (facilitation) during the initial 5–15 AP-like stimuli of such trains in our experimental condition, regardless of EPSC depression
Multivesicular release differentiates the reliability of synaptic transmission between the visual cortex and the somatosensory cortex.
Full text linkNeurons in layer 4 (L4) of the cortex play an important role in transferring signals from thalamus to other layers of the cortex. Understanding the fundamental properties of synaptic transmission between L4 neurons helps us gain a clear picture of how the neuronal network in L4 cooperates to process sensory information. In the present study, we have determined the underlying parameters that govern synaptic strength, such as quantal size, size of readily releasable vesicle pool, and release probability (Pr) of excitatory synaptic connections within L4 of the visual cortex (V1) and the somatosensory cortex (S1) in mice. Although only a single vesicle is released per release site under physiological conditions at V1 synapses, multivesicular release (MVR) is observed at S1 synapses. In addition, we observed a saturation of postsynaptic receptors at S1 synapses. Other synaptic properties are similar in both cortices. Dynamic clamp experiments suggest that higher Pr and MVR at S1 synapses lower the requirement of the number of synaptic inputs to generate postsynaptic action potentials. In addition, the slower decay of synaptic current and the intrinsic membrane properties of the postsynaptic neuron also contribute to the reliable transmission between S1 neurons.</jats:p
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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