1,721,004 research outputs found
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
Establishment and maintenance of the germinal niche in the dogfish Scyliorhinus canicula and functional analysis of potential therapeutics factors
No full textLes Chondrichtyens sont des espèces d’intérêt de par leur position phylogénétique à la base des Vertébrés. Au cours de cette thèse réalisée sur un petit requin, la petite roussette, l’étude des protéines Nanos, essentielles pour le maintien de la lignée germinale chez les Ostéichtyens, a mis en évidence la présence de deux protéines Nanos1 (1A et 1B) chez les Chondrichtyens, résultant d’une duplication du gène en amont des Gnathostomes. Chaque paralogue a révélé des profils d’expression spécifiques suggérant une spécification génique. De plus, la niche des spermatogonies souches (SSCs) a été mieux caractérisée et de nouveaux marqueurs de pluripotence tels que SSEA4 et Sox2 ont été détectés dans les SSCs potentielles chez cette espèce. Une culture primaire enrichie en spermatogonies de la zone germinative a montré une hétérogénéité d’expression des facteurs de SSC analysés (GFRα1, SSEA4, POU2, Nanos1A, Nanos1B, c-Kit), suggérant une hétérogénéité des cellules souches et/ou des progéniteurs. Afin de valider le caractère souche de ces cellules en culture, un test fonctionnel de transplantation a été initié. Le développement de cette technologie, pour la première fois chez un Chondrichtyen, ouvre de nouvelles perspectives en termes de préservation de ces espèces. Enfin, la recherche de facteurs à potentiel thérapeutique au niveau testiculaire chez la petite roussette a permis l’identification d’un peptide capable de réguler la glycémie et l’insulinémie de souris présentant un diabète de type 2, mais son mode d’action reste à explorer. L’ensemble des résultats confirme l’intérêt de la petite roussette pour l’étude évolutive de la niche germinale, essentielle au maintien de la gamétogenèse, et la recherche de molécules à potentiel thérapeutique.Chondrichthyes are species of interest because of their phylogenetic position at the base of the Vertebrates. In this thesis, based on a small shark, the small spotted dogfish, the study of Nanos proteins, essential for the maintenance of the germ line in Osteichthyes, showed the presence of two Nanos1 proteins (1A and 1B) in Chondrichthyes, resulting from a gene duplication upstream of the Gnathostomata. Each paralog revealed specific expression profiles suggesting a gene specification. In addition, the spermatogonial stem cells (SSCs) niche was better characterized and new pluripotency markers such as SSEA4 and Sox2 were detected in potential SSCs in this species. A primary culture of the germinative zone enriched in spermatogonia showed a heterogeneity of expression of the analysed SSC factors (GFRα1, SSEA4, POU2, Nanos1A, Nanos1B, c-Kit), suggesting heterogeneity of stem cells and / or progenitors. In order to validate the stemness potential of these cells in culture, a functional transplantation test was initiated. The development of this technology, for the first time in a Chondrichthyes, opens new perspectives in terms of preservation of these species. Finally, the search of potential therapeutic factors in the dogfish testis led to the identification of a peptide able to regulate blood glucose and insulin levels in mice presenting type 2 diabetes, but its mode of action remains to be explored. All the results confirm the interest of the small spotted dogfish for the evolutionary study of the germinal niche, essential to the maintenance of gametogenesis, and the search for molecules with therapeutic potential
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
Regulation paracrine de la fonction testiculaire chez la roussette (Scyliorhinus canicula L.): developpement d'un modele experimental
No full textSIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 81420 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Evolution of GnRH and glycoprotein hormone systems in endocrine and paracrine controls of spermatogenesis in the catshark, Scyliorhinus canicula
No full textLa spermatogenèse est un processus hautement spécialisé de prolifération et de différenciation cellulaire conduisant à la production de spermatozoïdes haploïdes à partir de cellules souches spermatogoniales diploïdes. Chez les Gnathostomes, les fonctions testiculaires sont principalement contrôlées de façon endocrine par l’axe hypothalamo-hypophyso-gonadique (HHG) impliquant notamment les GnRHs hypothalamiques et les hormones gonadotropes, FSH et LH, dont l’émergence s’est produite à la racine des Vertébrés cartilagineux. De plus, des fonctions paracrines des GnRHs et de la thyrostimuline ont été explorées au niveau gonadique chez des Vertébrés osseux. L’objet de cette thèse était de caractériser les régulations endocrines et paracrines de la spermatogenèse médiées par les GnRHs et les hormones gonadotropes chez un modèle Élasmobranche, la roussette Scyliorhinus canicula. Ce travail a été étendu à la caractérisation de GPA2 et GPB5, constituant la thyrostimuline, qui correspondent aux orthologues des ancêtres moléculaires des sous-unités des hormones glycoprotéiques. Dans ce travail, l’évolution du protéome testiculaire au cours de la spermatogenèse de S. canicula a été décrite, les neuropeptides GnRHs, les hormones glycoprotéiques FSH, LH, TSH, GPA2 et GPB5, et leurs récepteurs associés ont fait l’objet d’analyses in silico et d’expressions dans différents tissus avec un focus au cours de la spermatogenèse. Il a été observé une expression à tous les stades de la spermatogenèse de fshr, lhr et des récepteurs aux GnRHs au niveau germinale et sertolien, de tshr et gpb5 au niveau sertolien et de gpa2 au niveau germinal, avec des abondances plus importantes associées aux stades spermatides. Ce travail a été complété par des tests fonctionnels in vitro qui ont montré que FSHR pouvait être activé par FSH et LH, LHR uniquement par LH, et que GPB5-GPA2 pouvait activer les trois récepteurs FSHR, LHR et TSHR, suggérant ainsi un rôle paracrine de la thyrostimuline au niveau testiculaire. L’ensemble de ce travail permet de proposer un modèle de régulation de la spermatogenèse chez les Élasmobranches qui associe des hormones endocrines, avec les GnRHs et gonadotropines circulantes, et des hormones paracrines, avec GPA2, GPB5 et les stéroïdes. Ce modèle apparaît cohérent et intermédiaire dans l’évolution des systèmes régulateurs de la spermatogenèse qui seraient passés d’une régulation paracrine prépondérante chez les Bilatériens non-Vertébrés à une régulation endocrine prépondérante chez les Vertébrés osseux avec la mise en place de l’axe hypothalamo-hypophyso-gonadique.Spermatogenesis is a highly specialized process of cell proliferation and differentiation leading to the production of haploid spermatozoa from diploid spermatogonial stem cells. In Gnathostomes, testicular functions are mainly controlled by the endocrine hypothalamic-pituitary-gonadal (HHG) axis, involving hypothalamic GnRHs and the gonadotropic hormones FSH and LH, which emerged at the root of cartilaginous vertebrates. In addition, paracrine functions of GnRHs and thyrostimulin have been explored at the gonadic level in bony vertebrates. The aim of this thesis was to characterize the endocrine and paracrine regulation of spermatogenesis exerted by GnRHs and gonadotropic hormones in an Elasmobranch model, the catshark Scyliorhinus canicula. This work has been extended to the characterization of GPA2 and GPB5, constituting thyrostimulin, which correspond to orthologs of the molecular ancestors of glycoprotein hormone subunits. In this work, the evolution of the testicular proteome during spermatogenesis in S. canicula was described, and the neuropeptides GnRHs, the glycoprotein hormones FSH, LH, TSH, GPA2 and GPB5, as well as their associated receptors were studied by in silico and expression analyses in different tissues, with a focus on spermatogenesis. Expressions were observed at all stages of spermatogenesis for fshr, lhr and GnRH receptors associated at germinal and sertolian levels, for tshr and gpb5 at sertolian level and for gpa2 at germinal level, with higher abundances associated with spermatid stages. This work was complemented by in vitro functional tests which showed that FSHR could be activated by FSH and LH, LHR only by LH, and that GPB5-GPA2 could activate all three receptors FSHR, LHR and TSHR, suggesting a paracrine role for thyrostimulin at the testicular level. Taken together, this work proposes a model for the regulation of spermatogenesis in Elasmobranchs that combines endocrine hormones, with circulating GnRHs and gonadotropins, and paracrine hormones, with GPA2, GPB5 and steroids. This model appears consistent and intermediate in the evolution of spermatogenesis regulating systems, which has shift from predominantly paracrine regulation in non-vertebrate bilaterians to predominantly endocrine regulation in bony vertebrates, with the establishment of the hypothalamic-pituitary-gonadal axis
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
Dissociation and identification of intact seminiferous lobules from the testis of the dogfish (Scyliorhinus canicula)
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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
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