324 research outputs found
Temperature-dependence of microtubule dynamics across Xenopus species
Eukaryontische Zellen besitzen ein Zytoskelett, ein zellulĂ€res Netzwerk aus Biopolymeren. Unter diesen Biopolymeren sind die Mikrotubuli weitgehend konserviert. Diese aus Tubulin aufgebauten Filamente sind dynamisch und wechseln zwischen Phasen des Wachstums und der Schrumpfung. Die genauen Mechanismen, die die dynamische InstabilitĂ€t der Mikrotubuli bestimmen, werden noch erforscht. Die Allgegenwart von Mikrotubuli wirft die Frage auf, wie sie in verschiedenen thermischen Umgebungen konservierte Funktionen ausfĂŒhren können.
Um dieser Fragestellung nachzugehen, habe ich verwandte Froscharten mit unterschiedlich temperierten LebensrĂ€umen untersucht: Xenopus laevis (16-22 °C), Xenopus borealis (19-23 °C) und Xenopus tropicalis (22-30 °C). Um zu untersuchen, ob sich die biochemischen Eigenschaften von Tubulin und die Dynamik der Mikrotubuli bei den drei Arten an die Temperatur angepasst hat, habe ich die Methoden der Tubulin-AffinitĂ€tsreinigung und die temperaturgesteuerte TIRF-Mikroskopie zur Rekonstitution der Mikrotubuli-Dynamik kombiniert. Dabei habe ich festgestellt, dass bei einer Temperatur von 25°C die Wachstumsgeschwindigkeit der Mikrotubuli im Bezug zur thermischen Nische der einzelnen Arten negativ korreliert. Die Verwendung der Arrhenius-Gleichung zum Vergleich der Aktivierungsenergie der Mikrotubuli-Polymerisation fĂŒr jede Spezies ergab, dass die freie Energie des Tubulins umso höher ist, je kĂ€lter die thermische Nische der Spezies ist. Die Mikrotubuli von X. laevis und X. borealis zeigten eine lĂ€ngere Lebensdauer und wurden hĂ€ufiger zerstört als die von X. tropicalis. Die Tubuline von X. laevis und X. borealis sind phosphoryliert, im Gegensatz zu X. tropicalis. Die Ergebnisse zeigen, dass sich Xenopus Tubulin und die Dynamik der Mikrotubuli an die Temperatur angepasst haben. Kalt lebende Arten kommen mit der niedrigeren Energie des Milieus zurecht, durch verbessertes Wachstum und StabilitĂ€t.Eukaryotic cells hold a cytoskeleton, a cellular network of biopolymers. Among the filaments of the cytoskeleton, microtubules are widely conserved. Built from tubulin, those filaments are dynamic, alternating between phases of growth and shrinkage. The biochemical properties of tubulin shape the dynamic behavior of microtubules, which is crucial for many cellular processes. The precise mechanisms determining microtubule dynamic instability are still under investigation. The ubiquity of microtubules raises the question of how they can perform conserved functions within various thermal environments. To address this, I turned to closely related frog species living at different temperatures, Xenopus laevis (niche: 16-22°C), Xenopus borealis (19-23°C) and Xenopus tropicalis (22-30°C). To probe whether the biochemical properties of tubulin and microtubule dynamics adapted to temperature across those three species, I combined tubulin affinity purification and temperature-controlled TIRF microscopy of in vitro reconstitution of microtubule dynamics. I found that at 25°C, the microtubule growth velocity inversely correlates with the thermal niche of each species. Adjusting temperature to each speciesâ endogenous condition modulates the growth rate differences across species. Using the Arrhenius equation to compare the activation energy of microtubule polymerization for each species suggested that the colder the thermal niche of the species, the higher the free energy of its tubulin.
Microtubules from the cold-adapted species X. laevis and X. borealis have longer lifetimes and rescue more often than those of X. tropicalis, both at 25°C and at each speciesâ endogenous condition. X. laevis and X. borealis tubulins are phosphorylated, contrary to X. tropicalis. My results show that Xenopus tubulin and microtubule dynamics have adapted to temperature. Cold-living species cope with the lower energy of the milieu by facilitating growth and stability
Honte et pauvreté
Cet article analyse les liens entre le sentiment de honte et la situation sociale de pauvreté. Suite à sa pratique d'éducateur de rue et de sociologue, l'auteur a pris conscience de l'importance de la honte chez les jeunes. Il a alors entrepris une analyse critique de 600 histoires de vie, à partir desquelles il a analysé la symptomatologie de la névrose de classe qui caractérise un conflit dont la genÚse est à la fois psychosociale, et qui concerne les personnes qui changent de classe sociale ou de culture. La honte joue un rÎle important dans l'apparition de ce type de névrose, en particulier pour les personnes issues de milieux défavorisés. Cet article est la synthÚse de ce travail.This article analyzes the links between the sense of shame and poverty's social reality. As a sociologist and as a social worker dealing with street kids, the author came to recognize the widespread shame that exists among youth. Following this, he undertook the critical analysis of 600 life histories. He analyzed the symptomatology of class neurosys which characterizes conflict. According to the author, this type of conflict has psychosocial origins and involves those people who undergo a change in culture or in social class. The sense of shame plays a major role in the emergence of this type of neurosys, particularly regarding people coming from underpriveledged environments. This article is a synthesis of the author's experiences
La NGP : Nouvelle gestion paradoxante
Le New public management (NPM) ou Nouvelle gestion publique (NGP) produit une pression psychologique intense sur les travailleurs. Ce phĂ©nomĂšne, que lâon a vu se dĂ©velopper dâabord dans les entreprises privĂ©es puis dans les entreprises publiques, apparaĂźt aujourdâhui dans le secteur non marchand comme les hĂŽpitaux, les administrations, les collectivitĂ©s locales, les institutions Ă©ducatives ou sociales. Dans ce contexte, la question de la santĂ© mentale au travail devient prĂ©gnante. La multiplication des symptĂŽmes dĂ©pressifs, le sentiment gĂ©nĂ©ralisĂ© de harcĂšlement, lâhyperactivitĂ©, lâĂ©puisement professionnel et le dĂ©veloppement de suicides sur le lieu de travail sont autant de symptĂŽmes dâun malaise profond. Les causes de ce phĂ©nomĂšne sont multiples. Cet article met lâaccent sur le processus de transformation des organisations en systĂšmes paradoxants qui mettent les travailleurs devant des injonctions paradoxales. Ă partir dâune situation clinique travaillĂ©e dans un groupe dâimplication et de recherche, il dĂ©crit les diffĂ©rents Ă©lĂ©ments qui caractĂ©risent la mise en place de ces systĂšmes, les consĂ©quences pour ceux qui les vivent, en particulier ses effets sociopsychiques. Enfin, il Ă©voque les rĂ©actions dĂ©fensives quâils provoquent et les mĂ©canismes de dĂ©gagement individuels et collectifs.The New Public Management approach creates a severe psychological stress on workers. This phenomena appeared firstly in the private business sector and further on in public services. It develops now in the non-profit sector, hospitals, public administrations, local community associations, educational and social institutions. It is in this context that mental health issues come to be pervasive. A growing serious ill-being takes place at work, shown through an increasing number of depressive symptoms, a generalized climate of harassment at work, hyperactivity, burn out cases and an increase of suicides in the workplace. Causes are numerous. This paper stresses the very process of change leading to what can be called âparadox makingâ organization system. The different elements involved in the implementation of this kind of system with its sociopsychical impacts on people are illustrated from an analysis of a clinical group experience, a research and self-involvement seminar. Finally, responses to this situation come to be defensive reactions and freeing individual and collective strategies
Titrimetric method based on potentiometric titration to evaluate redox couples in wine and polyphenols
Polyphenols are electroactive compounds, each molecule having reductive (Rd) and oxidative forms (Ox) due to the presence of several phenolic hydroxyls. Direct study of Rd/Ox forms was conducted using potentiometric titration in two steps: First, a complete reduction of the polyphenol Rd/Ox couples by titanium III chloride TiCl3 (100 % Rd), and then, oxidative titration by dichlorophenolindophenol DCPIP (100 % Ox). The second curve represents the totality of polyphenol couples titration with, for each couple, a characteristic E0 point representing the equilibrium between the concentration of Rd and Ox forms (Rd/Ox = 1). This value was typical for each polyphenol. We conducted several preliminary experiments with a model polyphenol (catechin) to establish the analysis conditions. The titration solution concentration was N/10 in HCl N and N/20 in water for TiCl3 and DCPIP respectively. The concentration of this solution diminished very rapidly, i.e. within 24 h for TiCl3 and DCPIP (under nitrogen and in darkness) and regularly needed a fresh preparation. To control the consistency and precision of the method we performed a few tests on pure products (e.g. hydroquinone/quihydrone, Fe III, Fe II, Cu II) permitting comparison between theoretical and experimental E0 values. Our result indicated less than 5 % variation and curves with a high reproducibility.
Noblesse et haine de classe
L'histoire de BĂ©rangĂšre, participante Ă un groupe de recherche et d'implication sur le thĂšme roman familial et trajectoire sociale, montre les sentiments que suscite la noblesse aujourd'hui : haine, colĂšre, fascination... Elle-mĂȘme est peu consciente des rĂ©actions qu'entraĂźne le rĂ©cit de son enfance et la façon dont elle a incorporĂ© les habitus de son milieu. Le souvenir de la violence sociale passĂ©e est une " mĂ©moire vive ", qui perdure Ă travers les gĂ©nĂ©rations quand bien mĂȘme les rapports entre classes ne sont plus de mĂȘme nature.This article explains what happened in a training group betweenBĂ©rangĂšre, who is of noble descent, and the other participants, who are members of the lower class. In this kindof training group, entitled social career and family tales, people are asked toprepare and tell their life story. BerangĂšre's storyillustrates that, in France, even today, nobility gives rise to feelings ofhate, anger, fascination... She is unaware, when telling her life story, how much she is a product ofher social class, with its specific culture and values, and the effect thishas on the other participants. The social violence of class struggleremains alive in the collectivememory even though it is no longer of the same relevance as in the past, and tends to be transmitted from one generation to another
Sociologia clĂnica e saĂșde mental
The project âRecovery and life projectâ has a double objective: i. propose to the employees and residents of Maison Saint-Dominique (MSD - MontrĂ©al/CanadĂĄ), an in-depth work on his âfamily history and social trajectoryâ, under the guidance of clinical sociology, ii. develop an action research to evaluate this experiment as an alternative perspective on mental health, to be disseminated and compared other practices in the field of mental health. The article presents, in the first moment, the approach, its theoretical and methodological foundations. In the second moment, it reports the way in which the participants carried out the proposal and the perceived effects from their testimonies. The approach illustrates the interest in developing a clinic of complexity within the domain of mental health.Le projet âRĂ©tablissement et projet de vieâ a un double objectif: i. proposer aux intervenants et aux rĂ©sidents de la Maison Saint-Dominique (MSD - MontrĂ©al/Canada), un travail approfondi sur leur âroman familial et trajectoire socialeâ, dans lâorientation de la sociologie clinique; ii. dĂ©velopper une recherche-action pour Ă©valuer cette expĂ©rimentation en tant quâapproche alternative en santĂ© mentale, la diffuser et la confronter Ă dâautres pratiques dans le domaine de la santĂ© mentale. Le texte qui suit prĂ©sente, dans un premier temps, la dĂ©marche, ses soubassements thĂ©oriques et mĂ©thodologiques. Dans un deuxiĂšme temps, il rend compte de la façon dont les participants lâont mis en Ćuvre et les effets perceptibles Ă partir de leurs tĂ©moignages. La dĂ©marche illustre lâintĂ©rĂȘt de dĂ©velopper une clinique de la complexitĂ© dans le domaine de la santĂ© mentale.Le projet âRĂ©tablissement et projet de vieâ a un double objectif: i. proposer aux intervenants et aux rĂ©sidents de la Maison Saint-Dominique (MSD - MontrĂ©al/Canada), un travail approfondi sur leur âroman familial et trajectoire socialeâ, dans lâorientation de la sociologie clinique; ii. dĂ©velopper une recherche-action pour Ă©valuer cette expĂ©rimentation en tant quâapproche alternative en santĂ© mentale, la diffuser et la confronter Ă dâautres pratiques dans le domaine de la santĂ© mentale. Le texte qui suit prĂ©sente, dans un premier temps, la dĂ©marche, ses soubassements thĂ©oriques et mĂ©thodologiques. Dans un deuxiĂšme temps, il rend compte de la façon dont les participants lâont mis en Ćuvre et les effets perceptibles Ă partir de leurs tĂ©moignages. La dĂ©marche illustre lâintĂ©rĂȘt de dĂ©velopper une clinique de la complexitĂ© dans le domaine de la santĂ© mentale
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