Schmid-Schoenbein G W, Fung Y C, Zweifach B W
Circ Res. 1975 Jan;36(1):173-84. doi: 10.1161/01.res.36.1.173.
To determine the shear force acting on a white blood cell sticking to the endothelium of a blood vessel, the flow field about a single white blood cell in a venule was determined by hign-speed motion picture photomicrography. The force acting on the white blood cell was then calculated according to the principles of fluid mechanics. In this paper, the calculation was made using an experimentally determined dimensionless shear force coefficient obtained from a kinematically and dynamically similar model. The large physical model of the hemodynamic system could be easily instrumented, and the shear force acting on the model cell and the flow field around it were measured. The data were then used to calculate a shear force coefficient. On the basis of dynamic similarity, this shear force coefficient was applied to the white blood cell in the venule. The shear force coefficient was strongly influenced by the hematocrit, so in vivo hematocrits were measured from electron micrographs. It was found that in the venules of the rabbit omentum a white blood cell sticking to the endothelial wall was subjected to a shear force in the range of 4 times 10--5 dynes to 234 times 10--5 dynes; the exact value depended on the size and motion of the white blood cell, the size of the blood vessel, the velocity of the blood flow, and the local hematocrit, which varied between 20% and 40% in venules of about 40 mum in diameter. The contact area between the white blood cell and the endothelial cell was estimated, and the shear stress was found to range between 50 dynes/cm-2 and 1060 dynes/cm-2. The normal stress of interaction between the white blood cell and the endothelium had a maximum value that was of the same order of magnitude as the shear stress. The accumulated relative error of the experimental procedure was about 49%. The instantaneous shear force was a random function of time because of random fluctuations of the hematocrit.
为了确定作用于黏附在血管内皮上的白细胞的剪切力，通过高速运动显微摄影术测定了微静脉中单个白细胞周围的流场。然后根据流体力学原理计算作用于白细胞的力。在本文中，计算是使用从运动学和动力学相似模型获得的实验确定的无量纲剪切力系数进行的。血液动力学系统的大型物理模型易于安装仪器，测量作用于模型细胞及其周围流场的剪切力。然后使用这些数据计算剪切力系数。基于动态相似性，将该剪切力系数应用于微静脉中的白细胞。剪切力系数受血细胞比容的强烈影响，因此从电子显微照片测量体内血细胞比容。发现在兔网膜的微静脉中，黏附在内皮壁上的白细胞受到的剪切力范围为4×10⁻⁵达因至234×10⁻⁵达因；确切值取决于白细胞的大小和运动、血管大小、血流速度以及局部血细胞比容，在直径约40μm的微静脉中，血细胞比容在20%至40%之间变化。估计了白细胞与内皮细胞之间的接触面积，发现剪切应力范围为50达因/厘米²至1060达因/厘米²。白细胞与内皮之间相互作用的法向应力的最大值与剪切应力处于同一数量级。实验过程的累积相对误差约为49%。由于血细胞比容的随机波动，瞬时剪切力是时间的随机函数。
