Figure 2. A method for calculating jSR... | Rockefeller University Press

Figure 2.

$Figure 2. A method for calculating jSR release fluxes from spark records. (A) A simplified diagram illustrating the relative sizes of the T-tubules, jSR, network SR (nSR), myofilaments (myo), and a typical microscope PSF that blurs the Ca2+ signals. (B) By using spherical geometry for the model, the computational complexity is greatly reduced while still retaining the volume fractions and concentrations of each component that contribute to Ca2+ fluxes. Effectively, the spatial geometries of each component are spread over each computational compartment, making transport from the jSR isotropic at the length scale of interest (200 nm). The center element is dedicated to the dyadic space (including the jSR with CSQ; Kong et al., 2013), and all other compartments include reaction and diffusion fluxes in the cytosol and SR as indicated in the bottom part of the figure. Having calculated the spatial Fluo-4 and Fluo-5N signals, these are blurred by convolution with the microscope PSF, and the resulting signal is fitted to typical Ca2+ sparks by altering the time course of the jSR permeability change basis function (Kong et al., 2013). Because large numbers of simulations are performed to allow the release waveform to converge, efficiency in solving the discretized transport equations after microscope blurring is important.$

A method for calculating jSR release fluxes from spark records. (A) A simplified diagram illustrating the relative sizes of the T-tubules, jSR, network SR (nSR), myofilaments (myo), and a typical microscope PSF that blurs the Ca²⁺ signals. (B) By using spherical geometry for the model, the computational complexity is greatly reduced while still retaining the volume fractions and concentrations of each component that contribute to Ca²⁺ fluxes. Effectively, the spatial geometries of each component are spread over each computational compartment, making transport from the jSR isotropic at the length scale of interest (200 nm). The center element is dedicated to the dyadic space (including the jSR with CSQ; Kong et al., 2013), and all other compartments include reaction and diffusion fluxes in the cytosol and SR as indicated in the bottom part of the figure. Having calculated the spatial Fluo-4 and Fluo-5N signals, these are blurred by convolution with the microscope PSF, and the resulting signal is fitted to typical Ca²⁺ sparks by altering the time course of the jSR permeability change basis function (Kong et al., 2013). Because large numbers of simulations are performed to allow the release waveform to converge, efficiency in solving the discretized transport equations after microscope blurring is important.