1,720,956 research outputs found
Myelin in the Central Nervous System: Structure, Function, and Pathology
Get PDFOligodendrocytes generate multiple layers of myelin membrane around axons of the central nervous system to enable fast and efficient nerve conduction. Until recently, saltatory nerve conduction was considered the only purpose of myelin, but it is now clear that myelin has more functions. In fact, myelinating oligodendrocytes are embedded in a vast network of interconnected glial and neuronal cells, and increasing evidence supports an active role of oligodendrocytes within this assembly, for example, by providing metabolic support to neurons, by regulating ion and water homeostasis, and by adapting to activity-dependent neuronal signals. The molecular complexity governing these interactions requires an in-depth molecular understanding of how oligodendrocytes and axons interact and how they generate, maintain, and remodel their myelin sheaths. This review deals with the biology of myelin, the expanded relationship of myelin with its underlying axons and the neighboring cells, and its disturbances in various diseases such as multiple sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. Furthermore, we will highlight how specific interactions between astrocytes, oligodendrocytes, and microglia contribute to demyelination in hereditary white matter pathologies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dissertation for the award of the degree "Doctor rerum naturalium" Division of Mathematics and Natural Sciences of the Georg-August-Universität Göttingen
Get PDFMyelin is a multi-layered membrane wrapped around axons. It allows fast nerve
conduction and provides the axon with trophic support. In the central nervous sys-
tem (CNS), oligodendrocytes form multiple myelin sheaths. Thus, a single oligo-
dendrocyte has to coordinate the generation of numerous myelin segments on dif-
ferent axons. A cellular model of myelin sheath generation has been provided, but
the molecular mechanisms of multiple aspects of myelination such as initiation, lat-
eral growth and termination are still elusive. During myelination, the inner leaflet is
actively growing by adding new membrane layers to the sheath. At the same time,
the sheath is growing laterally and the outer layers are starting to compact. The ad-
hesion molecules forming the paranodal Caspr/Cntn1/Nfasc155 complex are essen-
tial for the formation of the Nodes of Ranvier (gaps inbetween individual sheaths),
but whether they might play a role in guiding myelin growth and wrapping is not
known.
In this study, we combined high-resolution live imaging with newest ultra-structure
resolving 3D electron microscopy techniques to assess the role of the mayor axon-
glial adhesion factors. We sequentially reduced internodal (Mag) and paranodal
(Caspr/Cntn1/Nfasc155) adhesion in zebrafish by Crispr/Cas9 gene editing and in
mice by crossbreeding of established mutant lines. Zebrafish mutants exhibited
myelinated cell bodies, decreased sheath length, impaired sheath growth dynamics
and double myelinated sheaths. Consistent with the zebrafish data, double mutants
in mice showed hypomyelination, reduced sheath length and split myelin sheaths.
The split myelin sheaths could be identified as either overgrown double myelin
segments or aberrant wrapping by a divided, misguided inner tongue, that we call
"inside-out-wrapping". In our model we propose, that axon-oligodendroglial ad-
hesion is essential for lateral growth, precise wrapping and correct targeting of the
myelin sheath. This results do not only provide new insights into myelin biology,
but may also have implications for our understanding of myelin formation in neu-
rological diseases
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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