Mathematics Department, Tulane University, 6823 St Charles Ave., New Orleans, LA 70118, USA.
J Theor Biol. 2011 Aug 21;283(1):203-16. doi: 10.1016/j.jtbi.2011.05.036. Epub 2011 Jun 7.
Hyperactivation in mammalian sperm is characterized by highly asymmetrical waveforms and an increase in the amplitude of flagellar bends. It is important for the sperm to be able to achieve hyperactivated motility in order to reach and fertilize the egg. Calcium (Ca(2+)) dynamics are known to play a large role in the initiation and maintenance of hyperactivated motility. Here we present an integrative model that couples the CatSper channel mediated Ca(2+) dynamics of hyperactivation to a mechanical model of an idealized sperm flagellum in a 3-d viscous, incompressible fluid. The mechanical forces are due to passive stiffness properties and active bending moments that are a function of the local Ca(2+) concentration along the length of the flagellum. By including an asymmetry in bending moments to reflect an asymmetry in the axoneme's response to Ca(2+), we capture the transition from activated motility to hyperactivated motility. We examine the effects of elastic properties of the flagellum and the Ca(2+) dynamics on the overall swimming patterns. The swimming velocities of the model flagellum compare well with data for hyperactivated mouse sperm.
哺乳动物精子的超激活特征表现为高度不对称的波形和鞭毛弯曲幅度的增加。精子能够实现超激活运动对于到达并使卵子受精非常重要。钙（Ca(2+)）动力学在超激活运动的启动和维持中起着重要作用。在这里，我们提出了一个整合模型，将 CatSper 通道介导的超激活 Ca(2+)动力学与理想化精子鞭毛在 3-d 粘性、不可压缩流体中的力学模型耦合。力学力是由于被动刚度特性和主动弯曲矩引起的，这些弯曲矩是鞭毛长度上局部 Ca(2+)浓度的函数。通过在弯曲矩中引入不对称性来反映轴丝对 Ca(2+)的响应不对称性，我们捕捉到了从激活运动到超激活运动的转变。我们研究了鞭毛弹性特性和 Ca(2+)动力学对整体游泳模式的影响。模型鞭毛的游动速度与超激活的小鼠精子数据非常吻合。
