Rapid assembly of a polar network architecture drives efficient actomyosin contractility

Actin network architecture and dynamics play a central role in cell contractility and tissue morphogenesis. RhoA-driven pulsed contractions are a generic mode of actomyosin contractility, but the mechanisms under- lying how their specific architecture emerges and how this architecture supports the contractile function of the network remain unclear. Here we show that, during pulsed contractions, the actin network is assembled by two subpopulations of formins: a functionally inactive population (recruited) and formins actively partici- pating in actin filament elongation (elongating). We then show that elongating formins assemble a polar actin network, with barbed ends pointing out of the pulse. Numerical simulations demonstrate that this geometry favors rapid network contraction. Our results show that formins convert a local RhoA activity gradient into a polar network architecture, causing efficient network contractility, underlying the key function of kinetic con- trols in the assembly and mechanics of cortical network architectures

Régulation traductionnelle en réponse à la fécondation et en conditions perturbées dans l'embryon d'oursin

Translation is a critical step in gene expression regulation. In sea urchin embryos, fertilization induces an increase in protein synthesis, which depends mainly on the translation of maternal messenger RNAs. This protein synthesis is essential for the first cell cycles. Embryonic development of the sea urchin is an excellent model for studying translational control. In this thesis, translational regulation in sea urchin embryos was studied in two situations: the physiological context of fertilization and the context of apoptosis induction. We first examined the regulatory mechanisms involved in protein synthesis after fertilization. Initiation is one of the limiting steps of translation. In this context, the initiation factor eIF2 plays a key role. eIF2 is responsible for bringing the initiator methionine to the ribosome. When the alpha subunit of eIF2 is phosphorylated, global protein synthesis is inhibited and the selective translation of certain mRNAs is stimulated. In the sea urchin unfertilized eggs, eIF2alpha is physiologically phosphorylated and fertilization induces its dephosphorylation. By microinjecting a variant mimicking the phosphorylated state of eIF2alpha into the unfertilized eggs, we showed that dephosphorylation of eIF2alpha is required for the first mitotic division in the sea urchin. We were interested in the relationship between the phosphorylation of eIF2alpha and induction of apoptosis in the sea urchin. Indeed, the translation of mRNAs encoding proteins pro- or anti-apoptotic directly influences cell survival. The sea urchin has the molecular tool kit for apoptotic induction. Exposing embryos to MMS, a DNA-damaging agent, causes phosphorylation of eIF2alpha and apoptosis activation. In this situation, we found that the GCN2 kinase is involved in the phosphorylation of eIF2alpha. In order to study how the translational machinery modulates the polysomal recruitment, we analyzed the translatome in response to fertilization and after exposure to MMS. We conducted deep sequencing of transcripts that are present in polysomes. Analysis of these transcripts, following annotation, will allow a better understanding of the genes regulatory network at the translational level during fertilization and the induction of apoptosis in sea urchin embryos.La traduction est une étape critique de la régulation de l'expression des gènes. Chez l'oursin, la fécondation induit une augmentation de la synthèse protéique, qui dépend essentiellement de la traduction d'ARN messagers maternels. Cette synthèse protéique est indispensable au déroulement des cycles cellulaires du développement précoce. Le développement embryonnaire de l'oursin constitue ainsi un modèle de choix pour étudier la régulation de la traduction. Dans le cadre de cette thèse, le contrôle de la traduction a été étudié chez l'oursin dans deux situations : le contexte physiologique de la fécondation et le contexte de l'induction de l'apoptose. Nous nous sommes interrogés d'abord sur les mécanismes régulateurs impliqués dans la synthèse protéique après fécondation. L'une des étapes limitantes de la traduction est l'initiation. Dans ce cadre, le facteur d'initiation eIF2 joue un rôle clé. eIF2 est responsable de l'apport de la méthionine initiatrice au niveau du ribosome. Lorsque la sous-unité alpha d'eIF2 est phosphorylée, la synthèse protéique globale est inhibée et la traduction sélective de certains ARNm est stimulée. Dans les ovules non fécondés d'oursin, eIF2alpha est physiologiquement phosphorylé et la fécondation provoque sa déphosphorylation. En micro-injectant dans les ovules non fécondés un variant d'eIF2alpha mimant l'état phosphorylé, nous avons montré que la déphosphorylation d'eIF2alpha est nécessaire pour la première division mitotique chez l'oursin. Nous nous sommes intéressés au lien entre la phosphorylation d'eIF2alpha et l'induction de l'apoptose chez l'oursin. En effet, la traduction d'ARNm codant pour des protéines pro- ou anti- apoptotiques influence directement la survie des cellules. L'embryon d'oursin possède la machinerie nécessaire pour le déclenchement de l'apoptose, après induction par l'agent génotoxique MMS. Le traitement au MMS des embryons provoque la phosphorylation d'eIF2alpha. Dans cette situation, nous avons trouvé que la kinase GCN2 est impliquée dans la phosphorylation d'eIF2alpha. En fin, dans le but d'étudier comment la machinerie traductionnelle module le recrutement polysomal, nous avons analysé le traductome en réponse à la fécondation et après le traitement au MMS. Nous avons effectué une approche de séquençage à haut-débit des transcrits purifiés par gradients de polysomes. L'analyse de ces transcrits nous permettra d'appréhender le réseau des gènes régulés au niveau traductionnel lors de la fécondation et de l'induction de l'apoptose dans les embryons d'oursin

Laser In Dental Medicine. The Psychological Impact In Privat Practice

The aim of these study is to use the laser anaesthesia, a non-contact technique, in the minimal invaziv treatment of the profound and medium carrious lesions, at different erbium laser parameters. Material and method: The study group included 68 patiens with ages between 6 and 20; a two-year study (january 2006 – november 2008) performed in a private practice. The carious lesions treatment was performed with a saphire G6 erbium laser tip. Both laser anaesthesia techniques were used, assessing the patients dental anxiety with Hamilton Anxiety Scale and the intraoperatory sensitivity with the Wong-Baker FACES Pain Rating Scale. Results: Before chosing the anaesthesia techniques, 73% of the subjects were diagnosticated with moderate anxiety and a rigid, fear face; 20% severe symptoms, with distracted, tearful face and 7% of the patients had mild anxiety with a happy face. At the end of the treatment, 61,1% of the children and young adults with moderate symptoms of anxiety had a happy, hurts a little bit face; and those with severe anxiety had an indifferent face

Régulation traductionnelle en réponse à la fécondation et en conditions perturbées dans l embryon d oursin

La traduction est une étape critique de la régulation de l'expression des gènes. Chez l'oursin, la fécondation induit une augmentation de la synthèse protéique, qui dépend essentiellement de la traduction d'ARN messagers maternels et qui est indispensable au déroulement des cycles cellulaires embryonnaires. Dans le cadre de cette thèse, le contrôle de la traduction a été étudié chez l'oursin dans deux situations : le contexte physiologique de la fécondation et le contexte de l'induction de l'apoptose. L'une des étapes limitantes de la traduction est l'initiation, qui fait intervenir le facteur d'initiation eIF2, responsable de l'apport de la méthionine initiatrice au niveau du ribosome. Lorsque la sous-unité a d'eIF2 est phosphorylée, la synthèse protéique globale est inhibée et la traduction sélective d'ARNm est stimulée. Dans les ovules non fécondés d'oursin, eIF2a est physiologiquement phosphorylé et la fécondation provoque sa déphosphorylation. En microinjectant dans les ovules un variant d'eIF2a mimant l'état phosphorylé, nous avons montré que la déphosphorylation d'eIF2a est nécessaire pour la première division mitotique chez l'oursin. Nous nous sommes intéressés au lien entre la phosphorylation d'eIF2a et l'induction de l'apoptose chez l'oursin. La traduction d'ARNm codant pour des protéines pro- ou anti- apoptotiques influence directement la survie des cellules. Le traitement au MMS provoque la phosphorylation d'eIF2a par la kinase GCN2, et induit ainsi l'apoptose dans les embryons. En fin, dans le but d'étudier comment la machinerie traductionnelle module le recrutement polysomal, nous avons analysé le traductome en réponse à la fécondation et après le traitement au MMS, par une approche de séquençage à haut-débit. L'analyse des transcrits nous permettra d'appréhender le réseau des gènes régulés au niveau traductionnel lors de la fécondation et de l'induction de l'apoptose dans les embryons d'oursin.Translation is a critical step in gene expression regulation. In sea urchin embryos, fertilization induces an increase in protein synthesis, which depends mainly on the translation of maternal messenger RNAs. This protein synthesis is essential for the first cell cycles. In this thesis, translational regulation in sea urchin embryos was studied in two situations: the physiological context of fertilization and the context of apoptosis induction. Initiation is one of the limiting steps of translation. In this context, the initiation factor eIF2 plays a key role. eIF2 is responsible for bringing the initiator methionine to the ribosome. When the a subunit of eIF2 is phosphorylated, global protein synthesis is inhibited and the selective translation of certain mRNAs is stimulated. In the sea urchin unfertilized eggs, eIF2a is physiologically phosphorylated and fertilization induces its dephosphorylation. By microinjecting a variant mimicking the phosphorylated state of eIF2a into the unfertilized eggs, we showed that dephosphorylation of eIF2a is required for the first mitotic division in the sea urchin. We were interested in the relationship between the phosphorylation of eIF2a and induction of apoptosis in the sea urchin. Indeed, the translation of mRNAs encoding proteins pro- or anti-apoptotic directly influences cell survival. Exposing embryos to MMS, a DNA-damaging agent, causes phosphorylation of eIF2a and apoptosis activation. We found GCN2 kinase involved in the phosphorylation of eIF2a in this situation. Finally, we analyzed the translatome in response to fertilization and after exposure to MMS. We conducted deep sequencing of transcripts that are present in polysomes. Analysis of these transcripts, following annotation, will allow a better understanding of the genes regulatory network at the translational level during fertilization and the induction of apoptosis in sea urchin embryos.RENNES1-BU Sciences Philo (352382102) / SudocROSCOFF-Observ.Océanol. (292393008) / SudocSudocFranceF

Analysis of empirical parametrization and microscopical studies of deuteron-induced reactions

A review of deuteron-induced reaction analyses is carried out paying due consideration to reaction cross-section parametrization as well as theoretical models associated to the deuteron interaction process. The key role of direct interactions, i.e., breakup, stripping and pick-up processes is stressed out by the comparison of data with theoretical and evaluation predictions, including the latest TENDL-2017 library

Cell cycle arrest and activation of development in marine invertebrate deuterostomes

International audienc

Analysis of empirical parametrization and microscopical studies of deuteron-induced reactions

A review of deuteron-induced reaction analyses is carried out paying due consideration to reaction cross-section parametrization as well as theoretical models associated to the deuteron interaction process. The key role of direct interactions, i.e., breakup, stripping and pick-up processes is stressed out by the comparison of data with theoretical and evaluation predictions, including the latest TENDL-2017 library

Role of the direct processes in low-energy deuteron interactions

An extended analysis of the key role of direct interactions, i.e., breakup, stripping and pick-up processes, has been carried out for deuteron-induced reactions. Particular comments concern the deuteron breakup which is the dominant mechanism involved in surrogate reactions on heavy nuclei, around the Coulomb barrier

The Cardiovascular Effects of Cocoa Polyphenols—An Overview

Cocoa is a rich source of high-quality antioxidant polyphenols. They comprise mainly catechins (29%–38% of total polyphenols), anthocyanins (4% of total polyphenols) and proanthocyanidins (58%–65% of total polyphenols). A growing body of experimental and epidemiological evidence highlights that the intake of cocoa polyphenols may reduce the risk of cardiovascular events. Beyond antioxidant properties, cocoa polyphenols exert blood pressure lowering activity, antiplatelet, anti-inflammatory, metabolic and anti-atherosclerotic effects, and also improve endothelial function. This paper reviews the role of cocoa polyphenols in cardiovascular protection, with a special focus on mechanisms of action, clinical relevance and correlation between antioxidant activity and cardiovascular health