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This research surveys the impact of the « relation with learning » on the evolution of scientific conceptions among gymnasium pupils. According to Charlot and Chevallard, learning mobilizes the « relation with learning ».Our results confirm that it exists a positive correlation between these two parameters: profiles indicating a positive relation with learning – namely Utilitarian Profile (U) and Pleasure Profile (P) – reinforce in the short run the evolution of science conceptions.These data show with statistic values that the « relation with learning » may influence science learning and have a positive impact on its dynamic.; Cette étude traite de l’incidence du « rapport à l’apprendre » sur l’évolution des conceptions scientifiques chez des collégiens. Elle entend tester l’hypothèse de Charlot et Chevallard selon laquelle l’entrée dans l’apprentissage requiert de prendre en compte le rapport qu’ont les apprenants sur l’apprendre.Nos résultats confirment une corrélation positive entre les deux paramètres : les profils « Utilitariste » (U) et « Plaisir » (P) – caractéristiques d’un rapport favorable au savoir - renforcent à court terme l’évolution des conceptions scientifiques.Ces données montrent statistiquement que le facteur “rapport à l’apprendre” peut influencer l’apprentissage des notions scientifiques et avoir une incidence bénéfique sur sa dynamique.

International audience; The functional effects of the anti-G21V antibody directed against the second extracellular loop of human heart S-HT4 receptors can differ when the receptors are expressed in different cell lines. Here, we extend these studies to show variation in the responses of 5-HT4(g) receptors to the antibody within the same expression system. In a previous report no effect of the anti-G21V antibodies had been shown upon 5-HT4(g) receptors expressed in CHO cells. Here the same antibodies alone or when added before 5-HT had a functional "inverse-agonist like" effect upon 5-HT4(g) receptors expressed in a separate line of CHO cells. Although these CHO cells showed a lower efficacy of cAMP production evoked by 5-HT than the previous report they express a similar hS-HT4(g) receptor density. Inhibition of either phosphodiesterases or Gi proteins had no effect upon the action of the antibody. Conformational states of the 5-HT4 receptor and/or equilibrium between different states of receptors may then determine the functional effect of antibodies against this receptor. (c) 2006 Elsevier Inc. All rights reserved.

The initial objective of this work was to examine the effects of an antibody (Anti-G21V) directed against the second extracellular loop of human heart 5-HT4 receptors expressed in Chinese hamster ovary (CHO) cells. The antibody anti-G21V had no effect upon either basal cAMP-or 5-HT-evoked increases in cAMP in CHO cells, whereas it had shown an agonist-like effect in COS-7 cells. Analysis of agonist fractions of h5-HT4(e) receptors in CHO and COS-7 cells revealed that equilibrium constant could underlie the different responses of the receptor toward the anti-G21V antibody. Therefore, different expression systems could give rise to functional differences in 5-HT4 receptor behavior.

International audience; In human atrial myocytes, serotonin rather than sympathetic, stimulation is more frequently associated with atrial fibrillation. So does the arrhythmogenic effect of serotonin result from the mechanism of action of the receptor or the context of its action upon cardiac myocytes? The capacity of agonists to produce cAMP followed the sequence 5-HT < Iso < Forskolin to increase ICaL with 5-HT = Iso = Forskolin. The simultaneous application of threshold concentrations of 5-HT and Iso maximally increased ICaL. We will show that the effect of 5-HT upon human atrial myocytes is an imbalance between low production of cAMP and maximal activation of ICaL.

National audience

National audience