Brokaw C J
Division of Biology, California Institute of Technology, Pasadena 91125, USA.
Cell Motil Cytoskeleton. 1996;33(1):6-21. doi: 10.1002/(SICI)1097-0169(1996)33:1<6::AID-CM2>3.0.CO;2-C.
The effect of altered viscous resistance on flagellar bending has been reexamined, utilizing ATP-reactivated sperm flagella from Ciona and newer methods that resolve metachronous and synchronous components of microtubule sliding and allow the examination of bend initiation as well as bend propagation. Large changes in amplitude and wavelength of bend propagation occur with little change in bend initiation parameters, other than frequency, indicating that bend initiation and bend propagation are regulated by quite different mechanisms. At increased viscosity, reduced amplitude of propagating bends, measured as metachronous shear amplitude, is associated with both reduced amplitude during bend initiation and amplitude adjustment after bends begin to propagate. This combination of effects was seen previously when reduced amplitudes were induced by increased salt concentration, and it was suggested to be caused by an imbalance between active moments and viscous resistances. However, in contrast to the results at increased salt concentrations, which involved significant reduction in bend curvature and little reduction in wavelength, increased viscosity causes very little change in curvature and causes a major reduction in wavelength. This difference can be explained by a model of flagellar bending in which inner arm dyneins have primary responsibility for maintaining bend curvature and outer arm dyneins have primary responsibility for performing work against viscous resistances. Both sets of dyneins would be inhibited by increased salt concentration, but increased viscous resistance would be irrelevant to the operation of inner arm dyneins.
利用来自海鞘的ATP再激活精子鞭毛以及更新的方法，重新研究了粘性阻力改变对鞭毛弯曲的影响。这些新方法可以分辨微管滑动的异时性和同步性成分，并允许检查弯曲起始以及弯曲传播。除频率外，弯曲起始参数变化不大的情况下，弯曲传播的幅度和波长会发生很大变化，这表明弯曲起始和弯曲传播受截然不同的机制调节。在粘度增加时，以异时性剪切幅度衡量的传播弯曲幅度减小，这与弯曲起始期间幅度减小以及弯曲开始传播后的幅度调整有关。当盐浓度增加导致幅度减小时，也曾出现过这种综合效应，有人认为这是由主动力矩和粘性阻力之间的不平衡引起的。然而，与盐浓度增加时的结果不同，盐浓度增加时弯曲曲率显著降低而波长降低很少，而粘度增加时曲率变化很小，但波长会大幅降低。这种差异可以通过鞭毛弯曲模型来解释，在该模型中，内臂动力蛋白主要负责维持弯曲曲率，外臂动力蛋白主要负责克服粘性阻力做功。两组动力蛋白都会受到盐浓度增加的抑制，但粘性阻力增加与内臂动力蛋白的运作无关。
