Myocardial Cells To Synchronize The Rhythm Of The Experimental Observations And Kinetic Study

The normal activity of life depends on rhythmic beating of the heart. However, the beating of heart is not of the uniformity but complex and nonlinear. People know that cardiac beating rhythms exhibit complex characteristics in multiple levels. In the whole heart, the fluctuation of rhythm which is adjusted by nerve and body fluid is endogenesis, and exhibits the characteristics of chaos. When units of conduction of heart's excitement mismatch, the rhythm will be turbulenced, such as the ectopic rhythm and arrhythmia. For the pace-making rhythm, the synchronized rhythms of cells in sinoatrial node are diverse, because they are heterogeneity. The diversity of pacemaker rhythm is the essential reason for the complex rhythm in the whole heart. In a word, it's necessary to study the synchronized pace-making rhythm. That the beating rhythm of single cardiac myocyte was unstable and exhibited bigger coefficient of variation was discovered in the previous experiment. It's difficult to find the recognizable and general rules. In normal solution, the synchronized beating rhythms of cultured cardiac cells exhibit periodic rhythms including period 1, period 2 and period 3, periodic rhythm with intermittency, integer multiple rhythms and non-periodic rhythms and so on. The procedure of the formation of synchronized process from single cells to network were studied in several cells whose behaviors were changed from non-synchronized rhythms to synchronized rhythms in a large scale network in previous studies. But the research method could not acquire the details in procedure to form synchronization. In this study, the network composed of two or three interfacing cells are employed to study the procedure of synchronized rhythms through the observation of the procedure from non-synchronized rhythm to synchronized rhythm in the cells. In addition, the dynamics of synchronized period 1 rhythm observed in the network composed of cultured cardiac cells are simulated in a mathematical network, and employed to interpret the periodic pace-making rhythms of heart.The beating rhythms of two or three cultured single cardiac myocytes were recorded by light density on workstation of living cells. The synchronized rhythms of networks exhibited diversity including synchronous period 1 rhythms, using calcic fluorescence recording method. Synchronous period 1 rhythms exhibited non-complete synchronization and weak phase difference. The results are as follow:1. With the increases of cultured time as well as coupling strength, independent rhythms of two or three myocytes became synchronous rhythms. 2. The synchronized rhythms are diversity in starting synchronization.3. The changes of beating rhythm from independence to synchronization are complex and of diversity. For example, in network composed of two myocytes, some of beatings became synchronization while others were independent firstly, and then all beatings became synchronous. In networks composed of three myocytes, beating rhythms of two myocytes achieved synchronization firstly, and then rhythms of three cells acquired synchronization.4. The synchronized rhythms were stabilized in period rhythm almostly with increasing of cultured time and the number of cells in networks.5. Similar synchronized rhythms can be simulated in a network composed of heterogeneous cells, which is described by Morris-Lecar model with different parameters and with neighboring coupling manner when the parameters are far from the bifurcation Hopf points.6. If the coupling strength is much stronger, the phase difference between different cells is much lower, but the value is not zero. Noise can slightly increase the phase difference, but the synchronous behavior is influenced little. The phase difference increases slightly when noise density is increased.The results not only gave changing characteristics during the procedure of forming synchronous rhythm, but also provided experimental demonstration of rhythm synchronization in life system. The simulation results imply that coupling strength leads to synchronization and heterogeneity of cells and noise lead to phase difference. The results provided theoretical interpretation of the synchronized period 1 rhythm, helpful to recognize the normal pace-making rhythm of heart.