Royal D, Royal M, Italiano J, Roberts T, Soll D R
Department of Biological Sciences, University of Iowa, Iowa City 52242, USA.
Cell Motil Cytoskeleton. 1995;31(3):241-53. doi: 10.1002/cm.970310307.
Computer-assisted methods have been employed to obtain a high resolution description of pseudopod expansion, cellular translocation, and the subcellular dynamics of MSP fiber complexes in the motile sperm of the nematode Ascaris suum. Although Ascaris sperm translocating in a straight line or along a curved path do not retract their pseudopod or significantly alter pseudopod shape, they move in a cyclic fashion, with an average period between velocity peaks of 0.35 +/- 0.05 min, which is independent of the forward velocity of sperm translocation. Expansion is confined to a central zone at the distal edge of the pseudopod for sperm translocating in a straight line and to a left-handed or right-handed lateral zone in the direction of turning, for sperm translocating along a curved path. For cells translocating in a straight line, the branch points and kinks of MSP fiber complexes move in a retrograde direction in relation to the substratum at an average velocity of 11 microns per min which is independent of the forward velocity of sperm translocation. The distal (anterior) end of a fiber complex, however, moves distally at the speed of sperm translocation when it emanates from the expansion zone, but when it is displaced to a nonexpanding surface of the pseudopod, it stops moving distally. When a cell is anchored to the substratum and is, therefore, nonmotile, the velocity of fiber complexes moving in a retrograde direction doubles. The unique aspects of pseudopod and MSP fiber complex dynamics in Ascaris are compared to the dynamics of pseudopod formation and actin filament dynamics in traditional actin-based amoeboid cells, and the treadmill model for MSP polymerization is reassessed in light of the discovery that fiber complex branch points move proximally (posteriorly) at a fixed rate.
计算机辅助方法已被用于获得对线虫猪蛔虫活动精子中伪足扩张、细胞移位以及MSP纤维复合体亚细胞动力学的高分辨率描述。尽管沿直线或沿曲线路径移动的猪蛔虫精子不会缩回其伪足或显著改变伪足形状，但它们以循环方式移动，速度峰值之间的平均周期为0.35±0.05分钟，这与精子移位的前进速度无关。对于沿直线移动的精子，扩张局限于伪足远端边缘的中央区域；对于沿曲线路径移动的精子，扩张局限于转向方向的左手或右手侧向区域。对于沿直线移动的细胞，MSP纤维复合体的分支点和扭结相对于基质以平均每分钟11微米的逆行速度移动，这与精子移位的前进速度无关。然而，纤维复合体的远端（前端）从扩张区发出时，以精子移位的速度向远端移动，但当它移动到伪足的非扩张表面时，它停止向远端移动。当细胞锚定在基质上因而不活动时，沿逆行方向移动的纤维复合体的速度加倍。将猪蛔虫伪足和MSP纤维复合体动力学的独特方面与传统基于肌动蛋白的变形虫细胞中伪足形成的动力学和肌动蛋白丝动力学进行了比较，并根据纤维复合体分支点以固定速率向近端（后端）移动这一发现，重新评估了MSP聚合的跑步机模型。
