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Tension corticale et positionnement du fuseau dans l’ovocyte de souris
No full textMeiotic divisions are highly asymmetric divisions in size, generating a big cell, the oocyte, and two tiny cells, the polar bodies. This asymmetry is ensured by the migration of the first meiotic spindle to the closest cortex. This migration does not depend on microtubules but on Myosin-II and an F-actin meshwork nucleated by cooperation of straight filament nucleators Formin-2 and Spire1/2. Preliminary studies in the lab described a thickening of the F-actin cortex during spindle migration, but paradoxically cortical tension, a physical parameter describing the stiffness of the cell, drops during spindle migration. I have shown that this thickening is required for spindle migration and nucleated by the branched actin nucleator Arp2/3, under the control of the Mos/MAPK pathway. Furthermore, it promotes the decrease in cortical tension by triggering the delocalization of Myosin-II from the oocyte cortex, which is crucial for spindle migration. Finally, I have shown that the drop in cortical tension is an amplificatory mechanism to the initial unbalance of forces (due to a slight off-centered position of the nucleus) triggering the motion of the spindle.Les divisions méiotiques sont très asymétriques en taille et génèrent une très grosse cellule, l'ovocyte, et deux petites cellules, les globules polaires. Cette asymétrie est permise par la migration du fuseau lors de la première division jusqu'au cortex le plus proche. Cette migration ne dépend pas des microbutules mais de la Myosin-II et d'un réseau de filaments d'actine nucléé par la coopération des nucléateurs de filaments droits Formin-2 et Spire1/2. Des observations préliminaires effectuées au laboratoire ont décrit un épaississement du cortex d'actine pendant la migration du fuseau, mais pourtant il avait été montré que la tension corticale, un paramètre décrivant la rigidité de l'ovocyte, diminue pendant la migration du fuseau. J'ai montré que cet épaississement est indispensable à la migration du fuseau et est nucléé par le nucléateur de filaments branchés Arp2/3, sous le contrôle de la voie Mos/MAPK. De plus, il provoque la diminution de la tension corticale en délocalisant la Myosin-II, ce qui est indispensable à la migration du fuseau. Finalement, j'ai montré que le chute de tension est un mécanisme d'amplification du déséquilibre des forces présent initialement (grâce au léger décentrage du noyau) qui déclenche la migration du fuseau
Tension corticale et positionnement du fuseau dans l’ovocyte de souris
No full textMeiotic divisions are highly asymmetric divisions in size, generating a big cell, the oocyte, and two tiny cells, the polar bodies. This asymmetry is ensured by the migration of the first meiotic spindle to the closest cortex. This migration does not depend on microtubules but on Myosin-II and an F-actin meshwork nucleated by cooperation of straight filament nucleators Formin-2 and Spire1/2. Preliminary studies in the lab described a thickening of the F-actin cortex during spindle migration, but paradoxically cortical tension, a physical parameter describing the stiffness of the cell, drops during spindle migration. I have shown that this thickening is required for spindle migration and nucleated by the branched actin nucleator Arp2/3, under the control of the Mos/MAPK pathway. Furthermore, it promotes the decrease in cortical tension by triggering the delocalization of Myosin-II from the oocyte cortex, which is crucial for spindle migration. Finally, I have shown that the drop in cortical tension is an amplificatory mechanism to the initial unbalance of forces (due to a slight off-centered position of the nucleus) triggering the motion of the spindle.Les divisions méiotiques sont très asymétriques en taille et génèrent une très grosse cellule, l'ovocyte, et deux petites cellules, les globules polaires. Cette asymétrie est permise par la migration du fuseau lors de la première division jusqu'au cortex le plus proche. Cette migration ne dépend pas des microbutules mais de la Myosin-II et d'un réseau de filaments d'actine nucléé par la coopération des nucléateurs de filaments droits Formin-2 et Spire1/2. Des observations préliminaires effectuées au laboratoire ont décrit un épaississement du cortex d'actine pendant la migration du fuseau, mais pourtant il avait été montré que la tension corticale, un paramètre décrivant la rigidité de l'ovocyte, diminue pendant la migration du fuseau. J'ai montré que cet épaississement est indispensable à la migration du fuseau et est nucléé par le nucléateur de filaments branchés Arp2/3, sous le contrôle de la voie Mos/MAPK. De plus, il provoque la diminution de la tension corticale en délocalisant la Myosin-II, ce qui est indispensable à la migration du fuseau. Finalement, j'ai montré que le chute de tension est un mécanisme d'amplification du déséquilibre des forces présent initialement (grâce au léger décentrage du noyau) qui déclenche la migration du fuseau
Tension corticale et positionnement du fuseau dans l’ovocyte de souris
No full textMeiotic divisions are highly asymmetric divisions in size, generating a big cell, the oocyte, and two tiny cells, the polar bodies. This asymmetry is ensured by the migration of the first meiotic spindle to the closest cortex. This migration does not depend on microtubules but on Myosin-II and an F-actin meshwork nucleated by cooperation of straight filament nucleators Formin-2 and Spire1/2. Preliminary studies in the lab described a thickening of the F-actin cortex during spindle migration, but paradoxically cortical tension, a physical parameter describing the stiffness of the cell, drops during spindle migration. I have shown that this thickening is required for spindle migration and nucleated by the branched actin nucleator Arp2/3, under the control of the Mos/MAPK pathway. Furthermore, it promotes the decrease in cortical tension by triggering the delocalization of Myosin-II from the oocyte cortex, which is crucial for spindle migration. Finally, I have shown that the drop in cortical tension is an amplificatory mechanism to the initial unbalance of forces (due to a slight off-centered position of the nucleus) triggering the motion of the spindle.Les divisions méiotiques sont très asymétriques en taille et génèrent une très grosse cellule, l'ovocyte, et deux petites cellules, les globules polaires. Cette asymétrie est permise par la migration du fuseau lors de la première division jusqu'au cortex le plus proche. Cette migration ne dépend pas des microbutules mais de la Myosin-II et d'un réseau de filaments d'actine nucléé par la coopération des nucléateurs de filaments droits Formin-2 et Spire1/2. Des observations préliminaires effectuées au laboratoire ont décrit un épaississement du cortex d'actine pendant la migration du fuseau, mais pourtant il avait été montré que la tension corticale, un paramètre décrivant la rigidité de l'ovocyte, diminue pendant la migration du fuseau. J'ai montré que cet épaississement est indispensable à la migration du fuseau et est nucléé par le nucléateur de filaments branchés Arp2/3, sous le contrôle de la voie Mos/MAPK. De plus, il provoque la diminution de la tension corticale en délocalisant la Myosin-II, ce qui est indispensable à la migration du fuseau. Finalement, j'ai montré que le chute de tension est un mécanisme d'amplification du déséquilibre des forces présent initialement (grâce au léger décentrage du noyau) qui déclenche la migration du fuseau
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
Tension corticale et positionnement du fuseau dans l’ovocyte de souris
No full textMeiotic divisions are highly asymmetric divisions in size, generating a big cell, the oocyte, and two tiny cells, the polar bodies. This asymmetry is ensured by the migration of the first meiotic spindle to the closest cortex. This migration does not depend on microtubules but on Myosin-II and an F-actin meshwork nucleated by cooperation of straight filament nucleators Formin-2 and Spire1/2. Preliminary studies in the lab described a thickening of the F-actin cortex during spindle migration, but paradoxically cortical tension, a physical parameter describing the stiffness of the cell, drops during spindle migration. I have shown that this thickening is required for spindle migration and nucleated by the branched actin nucleator Arp2/3, under the control of the Mos/MAPK pathway. Furthermore, it promotes the decrease in cortical tension by triggering the delocalization of Myosin-II from the oocyte cortex, which is crucial for spindle migration. Finally, I have shown that the drop in cortical tension is an amplificatory mechanism to the initial unbalance of forces (due to a slight off-centered position of the nucleus) triggering the motion of the spindle.Les divisions méiotiques sont très asymétriques en taille et génèrent une très grosse cellule, l'ovocyte, et deux petites cellules, les globules polaires. Cette asymétrie est permise par la migration du fuseau lors de la première division jusqu'au cortex le plus proche. Cette migration ne dépend pas des microbutules mais de la Myosin-II et d'un réseau de filaments d'actine nucléé par la coopération des nucléateurs de filaments droits Formin-2 et Spire1/2. Des observations préliminaires effectuées au laboratoire ont décrit un épaississement du cortex d'actine pendant la migration du fuseau, mais pourtant il avait été montré que la tension corticale, un paramètre décrivant la rigidité de l'ovocyte, diminue pendant la migration du fuseau. J'ai montré que cet épaississement est indispensable à la migration du fuseau et est nucléé par le nucléateur de filaments branchés Arp2/3, sous le contrôle de la voie Mos/MAPK. De plus, il provoque la diminution de la tension corticale en délocalisant la Myosin-II, ce qui est indispensable à la migration du fuseau. Finalement, j'ai montré que le chute de tension est un mécanisme d'amplification du déséquilibre des forces présent initialement (grâce au léger décentrage du noyau) qui déclenche la migration du fuseau
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
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