Skierczynski B A, Usami S, Chien S, Skalak R
Department of Applied Mechanics and Engineering Science, University of California, San Diego, La Jolla 92093-0412.
J Biomech Eng. 1993 Nov;115(4B):503-9. doi: 10.1115/1.2895531.
A novel experimental method of producing and observing the active motion of polymorphonuclear leukocytes (PMNs) using a micropipette technique has been recently developed (Usami et al., 1992). The present paper develops a quantitative theory for the chemoattractant gradients and cell locomotion observed in these experiments. In previous experimental methods (e.g., the Boyden chamber, the Zygmond chamber and the Dunn chamber) for study chemotaxis of leukocytes, fibroblasts, and PMNs, the exact nature of the concentration gradient of the chemoattractant is unknown. The cells may themselves modify the local gradient of the chemoattractant. In experiments using the micropipette, an internal source of chemoattractant provides well-defined boundary and initial conditions which allow the computation of the chemoattractant concentration gradient during the active locomotion of the PMNs. Since the cell completely fills the pipette lumen, convection is limited to the motion of the cells themselves. In coordinates moving with cell, it is assumed that diffusion is the only mechanism of mass transport of the chemoattractant (fMLP). Computations of the fMLP concentration during locomotion of the cell were carried out for a range of rates of fMLP binding by the receptors expressed on the front face of the cell membrane. The results show that the front face of the cell is subjected to increasing fMLP concentration during the cell motion. The sequence of events involve receptor binding of fMLP, signal transduction, polymerization of the cell cytoskeleton at the membrane of the front face, spatially dependent adhesion to the pipette wall, and localized contraction of the cytoskeleton. This sequence of events leads to the steady locomotion of the leukocytes in the micropipette. The computation of the distribution of the fMLP concentration during cell locomotion with constant velocity in micropipette experiments shows that the cell is exposed to increasing concentration of fMLP. This suggests that chemotaxis maybe induced by temporal gradient of an attractant.
最近开发了一种使用微量移液器技术产生并观察多形核白细胞（PMNs）主动运动的新型实验方法（宇佐美等人，1992年）。本文针对在这些实验中观察到的趋化因子梯度和细胞运动建立了一种定量理论。在以前用于研究白细胞、成纤维细胞和PMNs趋化性的实验方法（例如，Boyden小室、Zygmond小室和Dunn小室）中，趋化因子浓度梯度的确切性质是未知的。细胞本身可能会改变趋化因子的局部梯度。在使用微量移液器的实验中，趋化因子的内部来源提供了明确的边界条件和初始条件，这使得在PMNs主动运动过程中能够计算趋化因子浓度梯度。由于细胞完全充满移液器内腔，对流仅限于细胞自身的运动。在随细胞移动的坐标系中，假定扩散是趋化因子（fMLP）质量传输的唯一机制。针对细胞膜正面表达的受体对fMLP的一系列结合速率，进行了细胞运动过程中fMLP浓度的计算。结果表明，在细胞运动过程中，细胞正面受到的fMLP浓度不断增加。这一系列事件包括fMLP与受体的结合、信号转导、细胞正面膜处细胞骨架的聚合、与移液器壁的空间依赖性粘附以及细胞骨架的局部收缩。这一系列事件导致白细胞在微量移液器中稳定运动。在微量移液器实验中对细胞以恒定速度运动期间fMLP浓度分布的计算表明，细胞暴露于不断增加的fMLP浓度中。这表明趋化性可能是由吸引剂的时间梯度诱导的。
