MODEL FOR MICRO-STRUCTURE IN CILIATED ORGANISMS
MODEL FOR MICRO-STRUCTURE IN CILIATED ORGANISMS
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DOI：
10.1017/s0022112072001612
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发表时间：
1972-01-01
影响因子：
3.7
通讯作者：
BLAKE, J
中科院分区：
文献类型：
--
作者：
BLAKE, J
提出了改进的纤毛流体运动模型。提出了一种理论，该理论通过在一个平面表面上分布并一端附着在一个平面表面上的一系列柔韧的细长体来模拟有机体的纤毛。细长的身体被限制以类似于微生物蛋白藻、草履虫和胸膜臂的纤毛的模式移动。速度场由沿每个细长体中心线的力奇点分布（斯托克斯流）表示。分布在平面上的所有纤毛对速度场的贡献加起来，得到一个流效应，这反过来意味着生物体的推进力。由此，我们可以对这三种生物通过纤毛亚层的平均速度场进行建模。我们发现，在生物体内的一个参考系中，生物表面附近的速度很小——只有纤毛长度的一半——但从那时起，它迅速增加到接近推进速度的速度。这是因为纤毛的跳动模式；在有效（“力量”）划水时，他们以接近刚体旋转的方式划水，但在恢复划水时，他们靠近墙。回流（“反流”）被发现发生在具有抗塑性异时性的生物体中（即草履虫和胸膜臂虫）。梯度反转的发生，而不是回流，最近已被实验证实（Sleigh & Aiello 1971）。从这个分析中得到的其他重要的物理值是力，关于纤毛基部的弯矩和工作速率。我们发现，对于反塑性同时性，纤毛在推进方向上施加的力在有效冲程期间是大而正的，而在恢复冲程期间是小而负的。然而，恢复的持续时间比有效的持续时间长，所以在一个周期的纤毛搏动所施加的力是非常小的。弯矩遵循与推进方向上的力分量相似的模式，在抗塑性同时性的有效行程中较大。在辛同时（即欧帕利纳）中，当弯曲波沿纤毛传播时，力和弯矩的大小最大。工作速率表明草履虫和胸膜臂虫的有效冲程比恢复冲程消耗更多的能量，而蛋白藻在弯曲波传播过程中消耗的能量更大。
Improved models for the movement of fluid by cilia are presented. A theory which models the cilia of an organism by an array of flexible long slender bodies distributed over and attached at one end to a plane surface is developed. The slender bodies are constrained to move in similar patterns to the cilia of the microorganisms Opalina, Paramecium and Pleurobrachia.The velocity field is represented by a distribution of force singularities (Stokes flow) along the centre-line of each slender body. Contributions to the velocity field from all the cilia distributed over the plane are summed, to give a streaming effect which in turn implies propulsion of the organism. From this we have been able to model the mean velocity field through the cilia sublayer for the three organisms. We find that, in a frame of reference situated in the organism, the velocity near the surface of the organism is very small – up to one half the length of the cilium – but it increases rapidly to near the velocity of propulsion from then on. This is because of the beating pattern of the cilia; they beat in a near rigid-body rotation during the effective (‘power’) stroke, but during the recovery stroke move close to the wall. Backflow (‘reflux’) is found to occur in the organisms exhibiting antiplectic metachronism (i.e. Paramecium and Pleurobrachia). The occurrence of gradient reversal, but not backflow, has recently been confirmed experimentally (Sleigh & Aiello 1971).Other important physical values that are obtained from this analysis are the force, bending moment about the base of a cilium and the rate of working. It is found, for antiplectic metachronism, that the force exerted by a cilium in the direction of propulsion is large and positive during the effective stroke whereas it is small and negative during the recovery stroke. However, the duration of the recovery stroke is longer than the effective stroke so the force exerted over one cycle of a ciliary beat is very small. The bending moment follows a similar pattern to the component of force in the direction of propulsion, being larger in the effective stroke for antiplectic metachronism. In symplectic metachronism (i.e. Opalina) the force and bending moment are largest in magnitude when the bending wave is propagated along the cilium. The rate of working indicates that more energy is consumed in the effective stroke for Paramecium and Pleurobrachia than in the recovery stroke, whereas in Opalina it is found to be large during the propagation of the bending wave.