Yang P, Tameyasu T, Pollack G H
Department of Bioengineering, University of Washington, Seattle 98195, USA.
Biophys J. 1998 Mar;74(3):1473-83. doi: 10.1016/S0006-3495(98)77859-2.
Single relaxed myofibrils of bumblebee flight muscle were subjected to motor-imposed ramp-length changes. The image of the striations was projected onto a linear photodiode array, and sarcomere length was computed as the spacing between centroids of contiguous A-bands. Centroid position was determined by integrating the respective A-band intensity peak and computing the location at which the area on one side was equal to the other. The resulting trace of centroid to centroid span versus time was stepwise, with periods of rapid shortening alternating with periods of pause. An alternative nondiscrete sensor gave similar steps. If thick filament length remains constant, stepwise sarcomere length changes imply that length changes in the connecting filament must be stepwise. Thus, shortening of the connecting filament occurs as a sequence of discrete events rather than as a continuous event.
对大黄蜂飞行肌的单个松弛肌原纤维施加由运动引起的斜坡长度变化。条纹图像投射到线性光电二极管阵列上，肌节长度计算为相邻A带质心之间的间距。质心位置通过对相应A带强度峰值进行积分并计算一侧面积等于另一侧的位置来确定。由此得到的质心到质心跨度随时间的轨迹是阶梯状的，快速缩短期与停顿期交替出现。另一种非离散传感器给出了类似的阶梯。如果粗丝长度保持不变，肌节长度的阶梯状变化意味着连接丝的长度变化也必须是阶梯状的。因此，连接丝的缩短是一系列离散事件而非连续事件。
