Wouter-Jan Rappel

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Adaptation in signaling systems, during which the output returns to a fixed baseline after a change in the input, often involves negative feedback loops and plays a crucial role in eukaryotic chemotaxis. We determined the dynamical response to a uniform change in chemoattractant concentration of a eukaryotic chemotaxis pathway immediately downstream from G(More)
OBJECTIVES We hypothesized that human atrial fibrillation (AF) may be sustained by localized sources (electrical rotors and focal impulses), whose elimination (focal impulse and rotor modulation [FIRM]) may improve outcome from AF ablation. BACKGROUND Catheter ablation for AF is a promising therapy, whose success is limited in part by uncertainty in the(More)
Many eukaryotic cells, including Dictyostelium discoideum amoebae, fibroblasts, and neutrophils, are able to respond to chemoattractant gradients with high sensitivity. Recent studies have demonstrated that, after the introduction of a chemoattractant gradient, several chemotaxis pathway components exhibit a subcellular reorganization that cannot be(More)
Bicoid is a morphogen that sets up the anterior-posterior axis in early Drosophila embryos. Although the form of the Bicoid profile is consistent with a simple diffusion/degradation model, the observed length scale is much larger than should be expected based on the measured diffusion rate. Here, we study two possible mechanisms that could, in principle,(More)
Accurate cell division in Escherichia coli requires the Min proteins MinC, MinD, and MinE as well as the presence of nucleoids. MinD and MinE exhibit spatial oscillations, moving from pole to pole of the bacterium, resulting in an average MinD concentration that is low at the center of the cell and high at the poles. This concentration minimum is thought to(More)
INTRODUCTION The perpetuating mechanisms for human atrial fibrillation (AF) remain undefined. Localized rotors and focal beat sources may sustain AF in elegant animal models, but there has been no direct evidence for localized sources in human AF using traditional methods. We developed a clinical computational mapping approach, guided by human atrial tissue(More)
We develop a computational model, based on the phase-field method, for cell morphodynamics and apply it to fish keratocytes. Our model incorporates the membrane bending force and the surface tension and enforces a constant area. Furthermore, it implements a cross-linked actin filament field and an actin bundle field that are responsible for the protrusion(More)
We present results of experiments on the dynamics of Dictyostelium discoideum in a novel setup which constrains cell motion to a plane. After aggregation, the amoebae collect into round “pancake” structures in which the cells rotate around the center of the pancake. To provide a mechanism for the self-organization of the Dictyostelium cells, we have(More)
Electrical waves circulating around an obstacle in cardiac tissue are subject to a generic oscillatory instability. In a one-dimensional ring geometry this instability can produce both quasiperiodic and spatiotemporally chaotic oscillations while in a two-dimensional sheet of cardiac tissue it can lead to spiral wave breakup. We present a control scheme to(More)
Cell migration is a pervasive process in many biology systems and involves protrusive forces generated by actin polymerization, myosin dependent contractile forces, and force transmission between the cell and the substrate through adhesion sites. Here we develop a computational model for cell motion that uses the phase-field method to solve for the moving(More)