Figure 1.
Flowchart of cellular automaton simulation.
Figure 2.
Multi-tissue, isometric contractility thought experiments.
A) Isometric arrangement with tissues A–E in series. B) The hydrodynamic pressure chamber equivalent of A, where all chambers communicate through fluid filled channels. Tissues are rigidly attached below, but attached to a moveable piston at the top. C) The tissues are isometrically arranged in a circle, in analogy with A. Pulleys are between tissues, and the pulleys are supported by rigid bars. D) A schematic of the human uterus in cross section. Intrauterine pressure replaces the pulleys and rigid bars of C, and the hydrodynamics correspond with B. In both B and D, each tissue senses the same pressure.
Table 1.
Summary of variables.
Table 2.
Values for input settings.
Figure 3.
A. Simulation results using the default values.
See Table 2 for complete set of input values. B. The action potential multiplier was changed to 2 from 3, simulating nifedipine exposure (all other input values remained the same as in A). C. The action potential multiplier was reduced further to 1.5, simulating increasing the nifedipine concentration.
Figure 4.
Simulation of a different “patient” using different seed values for anatomy sensitivity (1474) and action potential threshold (2500).
Action potential multiplier is changed from 1.5 (A), to 2 (B), to 4 (C), to 8 (D), simulating increasing exposure to oxytocin.
Figure 5.
A. Simulation using the same seed values as in figure 4, and midrange parameter values.
The periods between contractions varies only slightly. B, C, and D. Regional activities immediately prior to the 4th, 5th, and 6th contractions, respectively. Each of the three contractions has a different apparent pacemaker (arrow).
Figure 6.
Simulation of single tissue, isometric contractility experiment.
Seeds and Weibull parameters were specifically selected for the anatomy sensitivity to be near 1 (0.991), and the action potential threshold to be low (0.558). A. Minimum pressure set above action potential threshold (0.6) reveals repetitive contractions. B. Minimum pressure set below threshold (0.55) reveals no repetitive contractions, even though the initial pressure is above threshold.
Figure 7.
Two tissues linked end-to-end in isometric contractility experiment.
A. Simulation where both tissues express repetitive contractions, but the tissues are contracting out-of-phase. B. Out-of-phase contractions experimentally recorded from two rat myometrial tissue strips demonstrating alternating contraction pattern corresponding to A (from ref. 16). “L” is the bioelectrical activity of the left tissue strip; “R” is the bioelectrical activity of the right tissue strip. C. Simulation after increasing the starting pressure, but keeping all other input values the same as in A, reveals in-phase contractions. D. Returning the starting pressure to the value in A, but decreasing the refractory duration also couples the tissue into an in-phase pattern.
Figure 8.
pseudo-Montevideo units are calculated from peak pressures and the total number of contractions expressed in 300 time steps.
The number of rows (i) and columns (j) is varied, but otherwise the input values are the same as in Fig. 3B. As the total number of regions changes, the pseudo-Montevideo units (solid line) vary in a complex manner, expressing a peak between 18 and 30 regions. The mean of the total sensitivity (filled circles) is approximated from the anatomy sensitivity and the action potential threshold of all the regions. Because these values are pseudorandomly selected for each region, there is a slight variation of the mean total sensitivity, especially for 4 to 8 regions. But for 10 regions and above, the fall in pseudo-Montevideo units cannot be explained by changes of the total sensitivity.