Futrelle R P, Traut J, McKee W G
J Cell Biol. 1982 Mar;92(3):807-21. doi: 10.1083/jcb.92.3.807.
The motion of cells in the aggregation phase of Dictyostelium discoideum development is complex. To probe its mechanisms we applied precisely timed (+/- 1 s) and positioned (+/-2 micrometers) pulses of cyclic AMP to fields of cells of moderate density using a micropipette. We recorded cell behavior by time lapse microcinematography and extracted cell motion data from the film with our Galatea computer system. Analysis of these data reveals: (a) Chemotaxis lasts only about as long as the cyclic AMP signal; in particular, brief pulses (approximately 5 s) do not induce chemotaxis. (b) Chemotactic competence increases gradually from within an hour after the initiation of development (starvation) to full competence at approximately 15 h when aggregation begins under our conditions. (c) Cell motion reverses rapidly (within 20 s) when the external gradient is reversed. There is no refractory period for motion. We present a new description of the process of aggregation consistent with our result and other recent findings. (d) The behavioral response to cyclic AMP includes a phenomenon we call "cringing." In a prototypical cringe the cell speed drops within 3 s after a brief cyclic AMP stimulus, and the cell stops and rounds and then resumes motion after 25 s. (e) The development of the speed response in cringing as the cells age closely parallels the development of the cyclic AMP-induced light-scattering response of cells in suspension. (f) Cringing occurs in natural populations during weak oriented movement. The computerized analysis of cell behavior proves to be a powerful technique which can reveal significant phenomena that are not apparent to the eye even after repeated examination of the film.
盘基网柄菌发育聚集阶段细胞的运动是复杂的。为了探究其机制，我们使用微量移液器向中等密度的细胞场施加精确计时（±1秒）和定位（±2微米）的环磷酸腺苷脉冲。我们通过延时显微电影摄影记录细胞行为，并使用我们的加拉泰亚计算机系统从胶片中提取细胞运动数据。对这些数据的分析揭示：（a）趋化作用持续的时间仅与环磷酸腺苷信号持续的时间大致相同；特别是，短暂脉冲（约5秒）不会诱导趋化作用。（b）趋化能力从发育开始（饥饿）后一小时内逐渐增加，在我们的条件下，当聚集开始时约15小时达到完全趋化能力。（c）当外部梯度反转时，细胞运动会迅速反转（在20秒内）。运动没有不应期。我们提出了一个与我们的结果和其他近期发现一致的聚集过程的新描述。（d）对环磷酸腺苷的行为反应包括一种我们称为“畏缩”的现象。在典型的畏缩中，细胞在短暂的环磷酸腺苷刺激后3秒内速度下降，细胞停止并变圆，然后在25秒后恢复运动。（e）随着细胞老化，畏缩中速度反应的发展与悬浮细胞中环磷酸腺苷诱导的光散射反应的发展密切平行。（f）在自然群体中，畏缩发生在微弱的定向运动期间。细胞行为的计算机化分析被证明是一种强大的技术，它可以揭示即使在反复查看胶片后肉眼也不明显的重要现象。
