1,720,991 research outputs found
Structure and functioning of the germinal niche in a Lophotrochozoan, the Pacific oyster Crassostrea gigas
No full textL’huître creuse Crassostrea gigas est un mollusque hermaphrodite alternatif dont le cycle dereproduction est annuel. Sa gamétogenèse est soutenue par des réserves énergétiques, stockées dansun tissu conjonctif de réserve entourant la gonade. Des travaux antérieurs ont montré l’implication dusystème insuline dans ce processus liant étroitement alimentation, énergie stockée et gamétogenèse.Le fonctionnement des étapes précoces de gamétogenèse reste encore méconnu chez l’huître. Cetravail a permis d’identifier les cellules germinales souches (GSC) et les progéniteurs potentiels en sebasant sur une approche d’histologie quantitative couplée au marquage des cellules germinales par unanticorps homologie anti-Oyvlg (Oyster vasa-like gene). Certains éléments constitutionnels de la nichegerminale ont également été identifiés, notamment la présence d’une cellule somatique associée à lacellule germinale souche potentielle qui présente un marquage par un anticorps hétérologue anti-BMP2/4. En amont de l’étude concernant la régulation des étapes précoces de gamétogenèse par lesvoies des insulines, le criblage in silico des bases de données a permis d’identifier des ligands, unrécepteur et de nombreux effecteurs du signal insuline conservés chez C. gigas. Six IRPs (InsulinRelated Peptides) ont été caractérisés ce qui a permis de retracer l’histoire évolutive des IRPs chez lesmollusques. D’après leur profil d’expression en qPCR et HIS, Cg-mip123 et Cg-ilp sont susceptiblesd’être impliqués dans le contrôle de la reproduction. Ces IRPs peuvent se lier à un récepteur CIR (C.gigas Insulin Receptor) dont la séquence complète a été décrite. Les acteurs des voies de signalisationde l’insuline sont également conservés chez l’huître et exprimés dans la gonade. Pour aller plus loin surle rôle de ces IRPs dans les étapes précoces de gamétogenèse, un conditionnement alimentaire (à jeunvs alimentés en Isochrysis galbana) a été réalisé sur des huîtres en première gamétogenèse. Lesrésultats de ce conditionnement montrent que l’apport nutritif augmente la différenciation des GSCainsi que les proliférations goniales. L’implication du signal insuline dans ce contrôle devra êtreprécisée.The Pacific oyster Crassostrea gigas is an alternative hermaphrodite mollusc with an annualreproduction cycle. Its gametogenesis is supported by energy reserves, store in a conjunctive storagetissue surrounding the gonad. Previous studies have shown the insulin system involvement in thisprocess closely connecting diet, energy reserves and gametogenesis. The functioning of earlygametogenetic stages stays unknown in the oyster. This work allows the identification of putative germstem cells (GSC) et progenitors on the basis of histological quantitative approach combined with agerm cells labelling by homologous antibody against Oyvlg (Oyster vasa-like gene). The maincomponents of the germinal niche have also been identified including a somatic cell, associated to theputative germ stem cell, with a heterologous antibody against BMP2/4 labelling. Above the study ofthe early gametogenetic stages regulation by insulin signalling, the genomic and transcriptomic-widescreening allows the identification of ligands, receptor et several effectors conserved in C. gigas. SixIRPs (Insulin Related Peptides) have been characterized which inform about the evolutionary history ofmolluscan IRPs. According to the expression profiles, in qPCR and ISH, Cg-mip123 and Cg-ilp may beinvolved in the reproduction process. These IRPs are able to bind the CIR (C. gigas Insulin Receptor)receptor whose sequence has been described. The insulin signalling effectors are also conserved in C.gigas and expressed in the gonad. To better understand the involvement of IRPs in the early stagesfunctioning, a food conditioning (unfed vs fed with Isochrysis galbana) has been done with oysters intheir first gametogenesis. The results showed that nutrient intake increases GSC and gonial mitosis.The involvement of insulin signalling has to be clarified
Lexicon of histological structures found in the ovaries and during the oogenesis of the four-spot megrim, Lepidorhombus boscii (Risso, 1810)
No full textLexicon describing, in depth, the cellular structures found within the Four-spot megrim's ovaries, and during the oogenesis
Lexicon of histological structures found in the ovaries and during the oogenesis of the megrim, Lepidorhombus whiffiagonis (Walbaum, 1792)
No full textLexicon describing, in depth, the cellular structures found within the megrim's ovaries, and during the oogenesis
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
ETUDE DU METABOLISME DU GLYCOGENE CHEZ L'HUITRE CREUSE CRASSOSTREA GIGAS. IMPACT SUR LA REPRODUCTION ET LES MORTALITES ESTIVALES
No full textCAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF
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
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