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首页> 美国卫生研究院文献>The Journal of Physiology >A velocity-dependent shortening depression in the development of the force-velocity relation in frog muscle fibres.
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A velocity-dependent shortening depression in the development of the force-velocity relation in frog muscle fibres.

机译：青蛙肌肉纤维中力-速度关系发展中的一种与速度有关的缩短凹陷。

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During the onset of activation in isolated frog muscle fibres the development of the force-velocity (T-V) relation was determined by imposing single and double ramp releases. The experiments were performed at 3.5-6 degrees C or 19-22 degrees C and at a starting sarcomere length of about 2.25 micron. A velocity- and time-dependent shortening deactivation was shown to exist during the development of contraction. It was found that, early during the tetanus rise, at submaximal levels of activation, the values of T (the steady force exerted by the muscle fibres at any velocity of shortening V lower than V0) were significantly affected by previous conditioning shortening. Conditioning shortening at lower speeds led to potentiation of T and, at higher speeds, to depression. Both these effects were independent of the amount of shortening and, in addition, were not present at the tetanus plateau. At each given time or isometric tension throughout the tetanus rise the values of T. normalized for those determined at the same velocities at the tetanus plateau, were found to be inversely correlated with the actual velocities of shortening. The slope of this relation (a measure of the velocity-dependent shortening deactivation) decreased exponentially with time, attaining, in six fibres at low temperature, 10% of its initial value within 26-73 ms. The results may be explained in terms of a cross-bridge model of contraction by assuming that the rate of development of activation is controlled by the rate of release of the Ca2+ as well as by the velocity at which the muscle fibres are allowed to shorten and in turn by the actual number of attached cross-bridges.
机译：在孤立的青蛙肌肉纤维激活过程中，通过施加单斜率和双斜率释放来确定力-速（T-V）关系的发展。实验在3.5-6摄氏度或19-22摄氏度，起始肌节长度约为2.25微米下进行。收缩过程中存在速度依赖和时间依赖的缩短减活作用。已经发现，在破伤风上升的早期，在次最大的激活水平下，T的值（在任何低于V0的缩短速度下由肌肉纤维施加的稳定力）都受到先前的调节缩短的影响。低速条件下的起酥油缩短会导致T增强，高速条件下会导致抑郁。这两种作用均与缩短的时间无关，此外，在破伤风高原上也不存在。在整个破伤风上升期间的每个给定时间或等轴测张力下，发现在破伤风高原以相同速度确定的标准化T.值与缩短的实际速度成反比。这种关系的斜率（一种与速度有关的缩短失活的量度）随时间呈指数下降，在低温下的六根光纤在26-73毫秒内达到其初始值的10％。可以通过跨桥收缩模型来解释结果，方法是假设激活的发展速率受Ca2 +释放速率以及肌肉纤维缩短和收缩的速度控制。依次按实际连接的跨桥数量。

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