Individual rules for trail pattern formation in Argentine ants (Linepithema humile)

We studied the formation of trail patterns by Argentine ants exploring an empty arena. Using a novel imaging and analysis technique we estimated pheromone concentrations at all spatial positions in the experimental arena and at different times. Then we derived the response function of individual ants to pheromone concentrations by looking at correlations between concentrations and changes in speed or direction of the ants. Ants were found to turn in response to local pheromone concentrations, while their speed was largely unaffected by these concentrations. Ants did not integrate pheromone concentrations over time, with the concentration of pheromone in a 1 cm radius in front of the ant determining the turning angle. The response to pheromone was found to follow a Weber's Law, such that the difference between quantities of pheromone on the two sides of the ant divided by their sum determines the magnitude of the turning angle. This proportional response is in apparent contradiction with the well-established non-linear choice function used in the literature to model the results of binary bridge experiments in ant colonies (Deneubourg et al. 1990). However, agent based simulations implementing the Weber's Law response function led to the formation of trails and reproduced results reported in the literature. We show analytically that a sigmoidal response, analogous to that in the classical Deneubourg model for collective decision making, can be derived from the individual Weber-type response to pheromone concentrations that we have established in our experiments when directional noise around the preferred direction of movement of the ants is assumed.Comment: final version, 9 figures, submitted to Plos Computational Biology (accepted

Cyclic Nucleotide Phosphodiesterases and Compartmentation in Normal and Diseased Heart

International audienceCyclic nucleotide phosphodiesterases (PDEs) degrade the second messengers cAMP and cGMP, thereby regulating multiple aspects of cardiac function. This highly diverse class of enzymes encoded by 21 genes encompasses 11 families which are not only responsible for the termination of cyclic nucleotide signalling, but are also involved in the generation of dynamic microdomains of cAMP and cGMP controlling specific cell functions in response to various neurohormonal stimuli. In myocardium, the PDE3 and PDE4 families are predominant to degrade cAMP and thereby regulate cardiac excitation-contraction coupling. PDE3 inhibitors are positive inotropes and vasodilators in human, but their use is limited to acute heart failure and intermittent claudication. PDE5 is particularly important to degrade cGMP in vascular smooth muscle, and PDE5 inhibitors are used to treat erectile dysfunction and pulmonary hypertension. However, these drugs do not seem efficient in heart failure with preserved ejection fraction. There is experimental evidence that these PDEs as well as other PDE families including PDE1, PDE2 and PDE9 may play important roles in cardiac diseases such as hypertrophy and heart failure. After a brief presentation of the cyclic nucleotide pathways in cardiac cells and the major characteristics of the PDE superfamily, this chapter will present their role in cyclic nucleotide compartmentation and the current use of PDE inhibitors in cardiac diseases together with the recent research progresses that could lead to a better exploitation of the therapeutic potential of these enzymes in the future

Analysis of the key elements of FFAT-like motifs identifies new proteins that potentially bind VAP on the ER, including two AKAPs and FAPP2.

Two phenylalanines (FF) in an acidic tract (FFAT)-motifs were originally described as having seven elements: an acidic flanking region followed by 6 residues (EFFDA-E). Such motifs are found in several lipid transfer protein (LTP) families, and they interact with a protein on the cytosolic face of the ER called vesicle-associated membrane protein-associated protein (VAP). Mutation of which causes ER stress and motor neuron disease, making it important to determine which proteins bind VAP. Among other proteins that bind VAP, some contain FFAT-like motifs that are missing one or more of the seven elements. Defining how much variation is tolerated in FFAT-like motifs is a preliminary step prior to the identification of the full range of VAP interactors

SJC 2004 | Rouen

L'Inde et le politique Séminaire Jeunes Chercheurs, 18/11/2004 La Maison de l'Université, Mont-Saint-Aignan Organisation : Virginie CHASLES, Elsa CHAVINIER, Anne-Cécile HOYEZ Partenaires : Université de Rouen, CEIAS-EHESS Présentation Les évènements récents (forum social, élections…) invitent à faire le point à la fois sur la politique et le politique en Inde. Ce travail de réflexion se justifie d’autant plus que les médias occidentaux nous transmettent une vision quelque peu restrictive du p..

Impact et utilisation des données scientifiques dans la mise en øeuvre des prises en charge de l'obésité de l'adulte : entre volonté et difficultés empiriques

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Comparative study of daily energy expenditure measured by physical activity questionnaire (QAPSE) and physical fitness (VO 2max) in the elderly

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Comprendre la non-adhésion à l'activité physique après un diagnostic de cancer pour mieux accompagner les patients Partie I : Comprendre la non-adhésion à une pratique régulière d'activité physique

International audienceCet article présente un cadre conceptuel à l'interface des dimensions physiologiques et psychologiques (le 'syndrome des 3H' ou processus de 'sédentarisme') permettant de rendre compte des processus de non-engagement qui maintiennent certains patients atteints de cancer en dehors de la pratique régulière d'activité physique (AP) ou de programmes d'AP. Dans cette première partie, nous avons montré comment la dynamique des interactions entre les ressources physiques mobilisables par la personne et le rapport que la personne entretient avec l'AP permet d'éclairer ces processus