Showing papers by "James Sneyd published in 1998"
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01 Jan 19982,212 citations
TL;DR: The properties of traveling waves in simple reaction-diffusion equations in which the diffusing species is buffered are studied, and it is shown that stationary buffers cannot eliminate traveling waves.
Abstract: Traveling waves of calcium are widely observed under conditions where the free calcium is heavily buffered. It is thus of considerable physiological interest to determine the precise effects that buffers have on the properties of traveling waves. Since calcium waves are widely believed to be the result of the reaction and diffusion of calcium, we study the properties of traveling waves in simple reaction-diffusion equations in which the diffusing species is buffered. For the buffered bistable equation we derive a constraint on the model parameters in order for a traveling wave of excitation to exist, and we show that stationary buffers cannot eliminate traveling waves. When the buffer is of low affinity, a constant effective diffusion coefficient may be defined, but no effective diffusion coefficient can be defined for high affinity buffers. We derive an approximate expression for the wave speed, show numerically that this approximation applies for both high and low affinity buffers, and hence derive an a...
84 citations
TL;DR: A passive diffusion of IP3, but not Ca2+, through gap junctions remains the preferred hypothesis for the mechanism underlying mechanically-stimulated intercellular calcium waves and Ca2+ oscillations.
58 citations
TL;DR: In the calcium wave model, it is shown numerically that the spiral period is first a decreasing, then an increasing, function of the intercellular permeability, and hypothesise that this is because the curvature of the spiral core is unimportant at low permeability.
50 citations
TL;DR: A putative causal link between an increase in the corticotroph Ca2+ current and action potential generation is demonstrated and the model is reduced to one with three equations, the behaviour of which was found to correspond well with that of the full model.
34 citations
TL;DR: A method of single-wavelength calcium imaging, in which the dye concentration is estimated from ratiometric fluorescence image pairs acquired at regular intervals during the recording period that furthermore includes a correction for the changing dye concentration in the calculation of [Ca2+].
25 citations
TL;DR: In this article, spiral waves in a model of Ca2+ dynamics in the Xenopus laevis oocyte were modeled by simulating the release of inositol 1,4,5-trisphosphate (IP3), a common experimental protocol.
Abstract: We study spiral waves in a model of Ca2+ dynamics in the Xenopus laevis oocyte. Spiral waves in the model were initiated by simulating the release of inositol 1,4,5-trisphosphate (IP3), a common experimental protocol. No artificial heterogeneities needed to be imposed on the system for the spontaneous formation of spiral waves. Increasing the size of the IP3 additions caused a decrease in the rotation period, and the breakup of the spiral wave, irregular spatiotemporal patterns occurred. Similar disorganized patterns are sometimes seen experimentally; based on our simulations we predict that a simple experimental procedure may be sufficient to reproduce unstable spiral waves.
18 citations