1,721,055 research outputs found
A Question of Identity: Genes that Distinguish Motoneurons from Interneurons
No full textThe question of how a single cell can grow, divide, and ultimately acquire a distinct function within an adult animal is central to the field of developmental biology. An elegant way to address this question is by studying the specification of a specific cell type, for example, vertebrate motoneurons. For an animal to be able to move and behave appropriately, individual motoneurons (MNs) must correctly innervate specific muscles. For this to happen, MNs must first be specified and then must differentiate into distinct subtypes, each of which is classified in part by the muscle it innervates. MN subtype specification is dependent on both the acquisition of MN-specific characteristics as well as the failure to acquire characteristics specific to interneurons, cells that only innervate other neurons. The entire process of specification is initiated in progenitor cells and relies on the correct spatial and temporal expression of specific genes.
Previous work in various vertebrate models has identified some of the key genes involved in MN specification, most notably transcription factors such as olig2, nkx6s, lhxs, mnxs, and islet1. In this dissertation, I use the zebrafish model to demonstrate novel roles in MN specification for two of these families of transcription factors - the lhxs and the mnxs. I provide evidence that both lhx3 and lhx4 are necessary for normal MN and ventral interneuron (IN) development and work by preventing MNs from expressing IN-specific characteristics. I also show that mnx1, mnx2a, and mnx2b are necessary in MNs both to promote the acquisition of some MN subtype-specific characteristics and to prevent the acquisition of some IN-specific characteristics and appear to be working in part through interactions with islet1. Finally, I identify an intermediate filament gene, inab, as being expressed in a subset of zebrafish MNs and a ventral IN and as having a potential role in the axon outgrowth of a specific MN subtype. Together, this work provides evidence for a mechanism of MN specification dependent on the expression of genes that both promote aspects of MN fate and inhibit aspects of IN fate.
This dissertation includes previously unpublished co-authored material
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
PRECLINICAL SCREENING OF A POTENTIALLY THERAPEUTIC COMPOUND TO TEST RESCUE OF RETINAL DEGENERATION IN A ZEBRAFISH MODEL OF USHER TYPE 1F
Get PDFUsher syndrome (USH) is a genetic disorder that affects 4 to 17 people per 100,000 worldwide. Usher syndrome type 1 (USH1), the most severe form of USH, is characterized by hearing and balance disorders at birth, and a progressive loss of vision beginning in childhood. Usher syndrome type 1F (USH1F), a subcategory of USH1, is caused by mutations in the PCDH15 gene. Mutations in PCDH15 that prematurely terminate the information encoded in the gene lead to truncated versions of the protocadherin-15 protein (PCDH15). This reduced or absent PCDH15 protein function leads to structural abnormalities in the hair cells of the inner ear and photoreceptors in the eye. We used a zebrafish model of USH1F to investigate whether hexafluoro, an antioxidant compound, can improve vision or retinal pathology in fish with impaired Pcdh15 protein function. We used an optokinetic response (OKR) assay to test whether hexafluoro-treated mutants showed improved vision compared to control fish, and examined photoreceptor cell integrity and survival in treated and untreated mutants. We found that hexafluoro improved visual function in USH1F mutant fish, and showed potential for reducing photoreceptor cell death. Our data indicate that hexafluoro has a stabilizing effect on retinal defects in zebrafish USH1F models, which are comparable to the early stages of human USH1F pathology, and provide proof of principle for expanding the effects of this and other drugs on zebrafish models of USH
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
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