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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)
Many eukaryotic cells are able to crawl on surfaces and guide their motility based on environmental cues. These cues are interpreted by signaling systems which couple to cell mechanics; indeed membrane protrusions in crawling cells are often accompanied by activated membrane patches, which are localized areas of increased concentration of one or more(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)
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)
OBJECTIVES The authors sought to study mechanisms to explain why single premature atrial complexes (PACs) from the pulmonary veins (PVs) may initiate human atrial fibrillation (AF). BACKGROUND Theoretically, single PACs may initiate AF if the rate response of action potential duration (APD) restitution has a slope >1. However, human left atrial APD(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)
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. This vortex state persists for many hours and we have explicitly verified that the motion(More)
Intracellular compartmentalization of second messengers can lead to microdomains of elevated concentration that are thought to be involved in ensuring signaling specificity. Most experimental evidence for this compartmentalization involves the second messenger adenosine monophosphate (cAMP), which is degraded by phosphodiesterases (PDEs). One possible way(More)
We address the striking coexistence of localized waves ('pulses') of different lengths which was observed in recent experiments and full numerical simulations of binary-mixture convection. Using a set of extended Ginzburg-Landau equations, we show that this multiplicity finds a natural explanation in terms of the competition of two distinct, physical(More)
Morphogens are proteins, often produced in a localized region, whose concentrations spatially demarcate regions of differing gene expression in developing embryos. The boundaries of gene expression are typically sharp and the genes can be viewed as abruptly switching from on to off or vice versa upon crossing the boundary. To ensure the viability of the(More)