1,721,129 research outputs found
Chromosomal Organization, Evolutionary Relationship, and Expression of Zebrafish GnRH Family Members
No full textExpression Pattern of nos1 in the Developing Nervous System of Ray-Finned Fish
No full textFish have colonized nearly all aquatic niches, making them an invaluable resource to understand vertebrate adaptation and gene family evolution, including the evolution of complex neural networks and modulatory neurotransmitter pathways. Among ancient regulatory molecules, the gaseous messenger nitric oxide (NO) is involved in a wide range of biological processes. Because of its short half-life, the modulatory capability of NO is strictly related to the local activity of nitric oxide synthases (Nos), enzymes that synthesize NO from L-arginine, making the localization of Nos mRNAs a reliable indirect proxy for the location of NO action domains, targets, and effectors. Within the diversified actinopterygian nos paralogs, nos1 (alias nnos) is ubiquitously present as a single copy gene across the gnathostome lineage, making it an ideal candidate for comparative studies. To investigate variations in the NO system across ray-finned fish phylogeny, we compared nos1 expression patterns during the development of two well-established experimental teleosts (zebrafish and medaka) with an early branching holostean (spotted gar), an important evolutionary bridge between teleosts and tetrapods. Data reported here highlight both conserved expression domains and species-specific nos1 territories, confirming the ancestry of this signaling system and expanding the number of biological processes implicated in NO activities
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
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
Zebrafish gsdf mutant provides a disease model for human polycystic ovary syndrome
No full textSingle page posterPolycystic ovary syndrome (PCOS) is the most frequent problem when a couple comes to a fertility clinic. PCOS in women includes the accumulation of premature oocytes in ovaries. We discovered that zebrafish lacking activity of the gsdf gene (gonad soma derived factor) due to gene editing (TALENS) mimic the pathology of PCOS. Homozygous gsdf mutants have delayed differentiation of the bi-potential gonad to ovary or testes during gonad development accumulation of young oocytes, elevated androgen, premature loss of fertility, obesity, and inappropriate expression of genes for lipid metabolism and insulin. We conclude that the gsdf mutant in zebrafish provides a disease model for human PCOS and suggests pathways for potential therapies
Sex Determination in Zebrafish: Genetics of Sex and wnt4a
Get PDFEffective reproduction is essential for species survival. Sexual reproduction depends upon functional gonads and reproductive ducts. Zebrafish (Danio rerio) is a popular model organism, but the genetic basis of zebrafish sex determination, gonad development, and reproductive tract development are not fully understood, and understanding this basis could inform about the evolutionary conservation of these genes and the use of zebrafish to investigate and treat reproductive diseases. In chapter I, I give a overview of sex determination systems, gonad development, and reproductive duct development in mammals and fish, and ask how sex is determined and how reproductive ducts develop in zebrafish. In chapter II, I used genome wide association studies (GWAS) to investigate if the genetic basis of sex determination in a variety of zebrafish strains -- two ‘wild-type’ strains cultured for about 30 years in the lab, and four ‘natural’ strains, wild-type strains isolated directly or recently from nature in India -- and identified a sex-associated region on zebrafish chromosome 4 in natural zebrafish strains that was lacking in the lab strains. In chapter III, I investigated whether or not wnt4a is important for zebrafish ovarian development, and found that wnt4a is expressed in the early bipotential gonad and that loss of wnt4a results in male-biased sex ratios, indicating that wnt4a is important for zebrafish ovarian development. In chapter IV, I investigated whether or not wnt4a is important for male reproductive duct development, and found that loss of wnt4a slows the formation of male reproductive ducts and prevents the male fused ducti deferens from connecting to the genital orifice in zebrafish males. Results further showed that wnt4a is expressed in tissue around the site where this connection should occur before and after the connection is formed, revealing a novel wnt4a phenotype in zebrafish that hasn’t been seen thus far, and indicating that wnt4a is necessary for proper male reproductive duct development in zebrafish.
This dissertation contains both published and unpublished co-authored material
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