Modelling a tethered mammalian sperm cell undergoing hyperactivation
Modelling a tethered mammalian sperm cell undergoing hyperactivation
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DOI：
10.1016/j.jtbi.2012.05.035
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发表时间：
2012-09-21
影响因子：
2
通讯作者：
Gaffney, E. A.
中科院分区：
文献类型：
--
作者：
Curtis, M. P.;Kirkman-Brown, J. C.;Gaffney, E. A.
哺乳动物精子鞭毛的搏动模式可分为两种不同类型。第一种是对称波沿着鞭毛向下传播，精子细胞具有净线性推进力。第二，过度活跃，波形被归类为有力的不对称波的较高的振幅，较低的波数和频率传播下来的鞭毛导致高度弯曲的轨迹。后一种节拍模式是获能过程的一部分，精子在此过程中为穿透透明膜和与卵子融合做准备。超活化通常被观察到开始作为精子逃逸上皮和纤毛结合内形成的峡部区域的女性输卵管，导致在文献中推测，这种波形是机械重要的精子逃逸。因此，我们探讨了机械超激活拴系精子的影响，集中在牛顿流体。使用阻力理论模型，我们证明，超活化确实可以产生的力量，拉精子远离拴系点，因此超活化的精子细胞结合到上皮表面不需要总是被它的鞭毛推动。更一般地说，由拴系鞭毛产生的力的方向是不敏感的拍频和详细的鞭毛响应的减少取决于在拴系点的结合的性质。此外，波形的不对称性和振幅的增加增强了拴系的鞭毛开始拉扯其绑定的趋势。同样的是普遍预测是真实的减少鞭毛拍的波数，但不是普遍如此，强调鞭毛力产生的动态复杂性。最后，从实验数据中得出的定性观察人类精子绑定到切除的女性生殖道也被提出，并发现与理论预测是一致的。(C)2012爱思唯尔有限公司保留所有权利。
The beat patterns of mammalian sperm flagella can be categorised into two different types. The first involves symmetric waves propagating down the flagellum with a net linear propulsion of the sperm cell. The second, hyperactive, waveform is classified by vigorous asymmetric waves of higher amplitude, lower wavenumber and frequency propagating down the flagellum resulting in highly curved trajectories. The latter beat pattern is part of the capacitation process whereby sperm prepare for the prospective penetration of the zona pellucida and fusion with the egg. Hyperactivation is often observed to initiate as sperm escape from epithelial and ciliary bindings formed within the isthmic regions of the female oviducts, leading to a conjecture in the literature that this waveform is mechanically important for sperm escape. Hence, we explore the mechanical effects of hyperactivation on a tethered sperm, focussing on a Newtonian fluid. Using a resistive force theory model we demonstrate that hyperactivation can indeed generate forces that pull the sperm away from a tethering point and consequently a hyperactivated sperm cell bound to an epithelial surface need not always be pushed by its flagellum. More generally, directions of the forces generated by tethered flagella are insensitive to reductions in beat frequency and the detailed flagellar responses depend on the nature of the binding at the tethering point. Furthermore, waveform asymmetry and amplitude increases enhance the tendency for a tethered flagellum to start tugging on its binding. The same is generally predicted to be true for reductions in the wavenumber of the flagellum beat, but not universally so, emphasising the dynamical complexity of flagellar force generation. Finally, qualitative observations drawn from experimental data of human sperm bound to excised female reproductive tract are also presented and are found to be consistent with the theoretical predictions. (C) 2012 Elsevier Ltd. All rights reserved.