Pollack G H, Tirosh R, Brozovich F V, Lacktis J W, Jacobson R C, Tameyasu T
Adv Exp Med Biol. 1984;170:765-86. doi: 10.1007/978-1-4684-4703-3_74.
The observation that sarcomeres shorten in steps has proved controversial. On the one hand, the phenomenon implies that the contractile process cannot be based on a molecular mechanism that behaves in a random manner: The fact that the steps and pauses characterize the kinetics of large volumes of tissue implies that the elements comprising such volumes must stop and pause synchronously. On the other hand, since current contractile models do not anticipate synchronized behavior, there has been considerable speculation that the phenomenon might not be a genuine feature of contraction, but an instrument-based artifact. We present here a review of observations made with four methods that have been brought to bear on the question. All four show discrete, synchronized contractile behavior. The observation of steps with multiple independent methods implies either that each technique harbors its own " gremlin " that generates spurious steps and pauses of a similar nature, or that the phenomenon is genuine. Finally, some consistent properties of the distribution of step size are considered with respect to possible molecular models.
肌节分步缩短这一现象一直存在争议。一方面，该现象意味着收缩过程不可能基于随机行为的分子机制：步骤和停顿表征大量组织动力学这一事实表明，构成此类组织的元件必须同步停止和停顿。另一方面，由于当前的收缩模型并未预期到同步行为，因此人们大量推测该现象可能并非收缩的真实特征，而是基于仪器的假象。我们在此对用四种方法进行的观察结果进行综述，这些方法已被用于研究该问题。所有四种方法均显示出离散的、同步的收缩行为。用多种独立方法观察到步骤意味着要么每种技术都存在自身的“小捣蛋鬼”，它会产生性质类似的虚假步骤和停顿，要么该现象是真实的。最后，针对可能的分子模型考虑了步长分布的一些一致特性。
