Stochastic Simulation Of Excitation-contraction Coupling

工作总结由于与Clara Franzini-Armstrong的广泛合作，我们已经获得了关于兔窦房结细胞细胞器和兰尼定受体分布的广泛统计数据。这些数据表明，我们的3D随机SANC模型的参数需要进行广泛的修改。自从上一份报告以来，我们已经找到了一种方法来做到这一点，以便该模型继续预测与观察一致的定性行为。然而，EM数据不足以确定兰尼定受体在细胞表面的临界分布。我们已经使用超分辨率SIM显微镜进行了广泛的成像，并开发了能够三维重建Ryanodine受体簇的位置和大小的软件，这将直接用于模型中。最终，我们希望开发基于单个细胞形状的3D坐标系。我们已经开发了一种软件，可以在模拟和实验记录中检测、分类和跟踪3D+时间的钙释放事件。这导致了对作为肾上腺素能刺激的函数在模型中发生传播的方式的新理解，并发现实验记录中的释放事件比之前怀疑的要多得多。我们已经开始研究窦房结内细胞的异质性，无论是在分离的细胞中，还是在小鼠整个窦房结标本的高空间和时间分辨率图像中。这导致了一种假设，即一些起搏细胞可能在静止状态下处于静止状态，并在肾上腺素能(战斗或逃跑)刺激的条件下被招募。我们最近开始与乔治华盛顿大学合作分离人类窦房结细胞，这是一个未知的领域，我们希望能够建立病态窦房结综合征等心率调节疾病的模型，并揭示随着年龄增长心率储备下降的机制。在下一个项目阶段，我们预计将修改模型以考虑人类窦房结，这一信息现在来自心脏移植的实验。根据科学顾问委员会的建议，我们正致力于将我们广泛的建模软件转换为可供其他研究人员使用的形式。

SUMMARY OF WORK As a result of extensive collaboration with Clara Franzini-Armstrong we have obtained extensive statistical data on the distribution of organelles and ryanodine receptors in rabbit siono-atrial node cells. These data indicated that the parameters of our 3D stochastic SANC model need to be extensively revised. Since the last report we have found a way to do this so that the model continues to predict qualitative behavior consistent with observations. Hwoever, the EM data are not sufficient to define the critical distribution of ryanodine receptors on the cell surface. We have done extensive imaging using ultra-resolution SIM microscopy, and have developed software that enables 3D reconstruction of the location and size of ryanodine receptor clusters, which will be used directly in the model. Eventually, we hope to develop 3D coordinate systems based on the shape of individual cells. We have developed software that an detect, classify and track calcium release event in 3D+time, both in simulations and in experimental records. This has led to new understanding of the way that propagation occurs in the model as a function of adrenergic stimulation, and to the discovery that there are many more release events in experimental records than previously suspected. We have begun studies of heterogeneity of cells within the sinus node, both in isolated cells and in high space and time resolution images of whole sinus node preparations from mouse. This has led to the hypothesis that some pacemaker cells may be quiescent at rest and be recruited under conditions of adrenergic (fight-or-flight) stimulation. We have recently initiated a collaboration with George Washington University to isolate human sino-atrial node cells, which is uncharted territory and we hope will lead to the ability to model diseases of heart-rate regulation such as sick-sinus syndrome, as well as shed light on the mechanism of decline of heart rate reserve with aging. In the next program period we anticipate revising the modeling to consider human sinus node, which information is now arriving from experiments on cardiac explants. As advised by the Board of Scientific Counselors, we are undertaking to translate our extensive modeling software into a form that can be used by other investigators.