10 research outputs found
An Essential Role for Katanin p80 and Microtubule Severing in Male Gamete Production
Katanin is an evolutionarily conserved microtubule-severing complex implicated in multiple aspects of microtubule dynamics. Katanin consists of a p60 severing enzyme and a p80 regulatory subunit. The p80 subunit is thought to regulate complex targeting and severing activity, but its precise role remains elusive. In lower-order species, the katanin complex has been shown to modulate mitotic and female meiotic spindle dynamics and flagella development. The in vivo function of katanin p80 in mammals is unknown. Here we show that katanin p80 is essential for male fertility. Specifically, through an analysis of a mouse loss-of-function allele (the Taily line), we demonstrate that katanin p80, most likely in association with p60, has an essential role in male meiotic spindle assembly and dissolution and the removal of midbody microtubules and, thus, cytokinesis. Katanin p80 also controls the formation, function, and dissolution of a microtubule structure intimately involved in defining sperm head shaping and sperm tail formation, the manchette, and plays a role in the formation of axoneme microtubules. Perturbed katanin p80 function, as evidenced in the Taily mouse, results in male sterility characterized by decreased sperm production, sperm with abnormal head shape, and a virtual absence of progressive motility. Collectively these data demonstrate that katanin p80 serves an essential and evolutionarily conserved role in several aspects of male germ cell development
Percian approches to filmic perception
Ce travail ambitionne de prĂ©senter les directions dans lesquelles peut s'Ă©laborer une rĂ©flexion sĂ©miotique peircienne sur la perception filmique. Partant dâune analyse de la « rencontre Peirce/Deleuze » dans CinĂ©ma I et II et des grandes lignes des phĂ©nomĂ©nologies sĂ©miotiques de lâimage chez Deleuze, Bergson et Peirce, je propose une (rĂ©)vision du concept dâiconicitĂ©, mais aussi dâindexicalitĂ©, Ă la lumiĂšre dâune sĂ©miotique de la perception filmique. En mâappuyant sur la thĂ©orie peircienne de la perception, je discute les types de perception que lâart filmique peut vĂ©hiculer, ainsi que leurs dimensions pĂ©dagogico-cognitives.This thesis wants to present the main directions of a Peircian semiotic reflection about filmic perception. Beginning with an analysis of the the Deleuzian application of Peircian semiotics in the Cinema I and II and of the main features of the semiotic phĂ©nomĂ©nologies in Deleuze, Bergson and Peirce, I present a (re)vision of the concept of iconicity, but also of indexicality, in the light of a semiotic of filmic perception. Leaning on the Peircian theory of perception I discuss the types of perception that filmic art is able to communicate, along with their pedagogical-cognitive dimensions
Perception, Dreams, Films: Iconicity and Indexicality in Peirce's Theory of Perception
Chronologically speaking, Charles S. Peirce (1839-1914) could have mentioned the technique of film in the context of his phenomenological, or as he called them, phaneroscopic theories. But when he compared the human percepts to âmoving pictures accompanied by sounds and feelingsâ in 1905 (MS 939 : 24), Peirce did not speak of the cinema. However, his investigations in the fields of cognition and phenomenology show relevant intersections with major concepts and problems of filmic perception theory. The present article aspires to investigate Peircian philosophy and film theory through some of their common concepts. The question will be raised as to whether the filmic viewing situation can be understood as a genuine perceptual situation in the Peircian sense. In a first step, I will give an analysis of Peirceâs theory of perception. In contrast to the majority of interpretations of the latter, which emphasize its iconic character, I shall argue for a perceptual process where iconicity is not the starting point but rather the outcome of it. This will imply an analysis of the roles of iconicity and indexicality in perception and of their relation to cinemaâs âimpression of realityâ. Despite the phenomenological realism of cinematic images, the nature of what the viewer actually perceives is not as obvious as one might be tempted to think. Finally, an interpretation of filmic images as âdiagrams of perceptionâ will open up to some pedagogical dimensions of film viewing.Dâun point de vue historique, Charles S. Peirce (1839-1914) aurait pu parler de la technique cinĂ©matographique dans le contexte de ses thĂ©ories phĂ©nomĂ©nologiques, ou, pour reprendre son propre terme, phanĂ©roscopiques. Mais en comparant, en 1905, les percepts humains Ă des âimages en mouvement accompagnĂ©es par des sons et des sentimentsâ (MS 939 : 24), Peirce ne parlait pas du cinĂ©ma. Ceci dit, ses investigations dans le champ de la cognition et de la phĂ©nomĂ©nologie prĂ©sentent des intersections importantes avec des concepts et problĂ©matiques majeurs de la thĂ©orie de la perception filmique. Cet article aspire Ă examiner la thĂ©orie peircienne et la thĂ©orie filmique Ă travers quelques uns de leurs concepts communs. En outre, il sera question de dĂ©terminer si regarder un film constitue une situation perceptuelle authentique au sens peircien. Dans un premier temps je donnerai une analyse de la thĂ©orie peircienne de la perception. Contrairement Ă la majoritĂ© des interprĂ©tations de cette derniĂšre, qui soulignent principalement son caractĂšre iconique, je vais argumenter pour un processus perceptuel oĂč lâiconicitĂ© nâest pas le point de dĂ©part mais plutĂŽt le rĂ©sultat. Cela impliquera une analyse des rĂŽles de lâiconicitĂ© et de lâindexicalitĂ© dans la perception et leur relation avec lâeffet dââimpression de rĂ©alitĂ©â au cinĂ©ma. Or, malgrĂ© le rĂ©alisme phĂ©nomĂ©nologique des images filmiques, la nature de ce que perçoit le spectateur nâest pas aussi Ă©vidente quâon pourrait le croire. Enfin, une interprĂ©tation des images filmiques comme des âdiagrammes de perceptionâ ouvrira vers une dimension pĂ©dagogique du visionnage de films
LâiconicitĂ© filmique. Un mĂ©talangage de la perception ?
Dans quelle mesure peut-on comprendre le langage iconique des images filmiques comme un mĂ©talangage des formes de la perception ? Le cinĂ©ma dispose dâune orientation iconique bilatĂ©rale : ses images en mouvement contiennent Ă la fois une instance perceptive percevable et des objets en mouvement percevables. Tandis que dans la perception naturelle aucune rĂ©fĂ©rence aux formes de la perception nâest possible, puisque le sujet percevant occupe une place constitutive dans la relation interne quâil entretient avec le monde perçu, lâart filmique visualise et donc externalise cette relation interne de la perception en mettant le spectateur devant une phĂ©no-technique dont le statut rĂ©aliste se rapproche Ă©normĂ©ment de la rĂ©alitĂ© de la perception humaine. Nous dĂ©montrerons dans cet article que la thĂ©orie peircienne des diagrammes permet une conciliation entre interprĂ©tation iconique et mĂ©talangage. Nous allons Ă©galement voir, Ă travers une redĂ©finition du concept de mĂ©talangage, que les effets du mĂ©talangage filmique rĂ©sultent non seulement de la nature cognitive de ses signes, mais aussi dâune dĂ©structuration pragmatique. LâexpĂ©rience filmique est lâexemple vivant dâun mĂ©talangage qui, sans faire usage dâune logique dâordre supĂ©rieur, est dotĂ© dâune expressivitĂ© pĂ©dagogique de force presque inquiĂ©tante.In which way can the iconic language of filmic images be understood as a metalanguage of the forms of perception? Cinema provides a bilateral iconic orientation: its moving images contain likewise a perceivable perceiving instance and perceivable perceived qualities. Whereas no reference to the forms of perception is possible in natural perception â since the perceiving subject occupies a constitutive place in the internal relation, which it maintains with the perceived worldâ filmic art can visualise, thus externalise this internal relation of perception by putting the spectator in front of a pheno-technique whose realism is very close to the reality of human perception. In this article I will try to show how the peircian theory of diagrams makes it possible to conciliate iconic interpretation with metalanguage. Moreover, via a redefinition of the concept of metalanguage, I will outline that the effects of filmic metalanguage not only result from the cognitive nature of its signs but also from a pragmatic de-structuration. Filmic experience is the living example of a metalanguage that, without using higher order logic, has a pedagogical expressivity of an almost disquieting force
Que peut le métalangage ?
Le présent numéro a bénéficié du concours de Marc Bonhomme, Claudio Paolucci, et Alessandro Zinna. Le comité de direction les remercie chaleureusement