Evans E, Yeung A
Department of Pathology, University of British Columbia, Vancouver, Canada.
Biophys J. 1989 Jul;56(1):151-60. doi: 10.1016/S0006-3495(89)82660-8.
Continuous deformation and entry flow of single blood granulocytes into small caliber micropipets at various suction pressures have been studied to determine an apparent viscosity for the cell contents and to estimate the extent that dissipation in a cortical layer adjacent to the cell surface contributes to the total viscous flow resistance. Experiments were carried out with a wide range of pipet sizes (2.0-7.5 microns) and suction pressures (10(2)-10(4) dyn/cm2) to examine the details of the entry flow. The results show that the outer cortex of the cell maintains a small persistent tension of approximately 0.035 dyn/cm. The tension creates a threshold pressure below which the cell will not enter the pipet. The superficial plasma membrane of these cells appears to establish an upper limit to surface dilation which is reached after microscopic "ruffles" and "folds" have been pulled smooth. With aspiration of cells by small pipets (less than 2.7 microns), the limit to surface expansion was derived from the maximal extension of the cell into the pipet; final areas were measured to be 2.1 to 2.2 times the area of the initial spherical shape. For suctions in excess of a threshold, the response to constant pressure was continuous flow in proportion to excess pressure above the threshold with only a small nonlinearity over time until the cell completely entered the pipet (for pipet calibers greater than 2.7 microns). With a theoretical model introduced in a companion paper, (Yeung, A., and E. Evans., 1989, Biophys. J. 56:139-149) the entry flow response versus pipet size and suction pressure was analyzed to estimate the apparent viscosity of the cell interior and the ratio of cortical flow resistance to flow resistance from the cell interior. The apparent viscosity was found to depend strongly on temperature with values on the order of 2 x 10(3) poise at 23 degrees C, lower values of 1 x 10(3) poise at 37 degrees C, but extremely large values in excess of 10(4) poise below 10 degrees C. Because of scatter in cell response, it was not possible to accurately establish the characteristic ratio for flow resistance in the cortex to that inside the cell; however, the data showed that the cortex does not contribute significantly to the total flow resistance.
研究了单个血液粒细胞在不同抽吸压力下持续变形并流入小口径微量移液器的过程，以确定细胞内容物的表观粘度，并估计与细胞表面相邻的皮层中的耗散对总粘性流动阻力的贡献程度。使用了多种移液器尺寸（2.0 - 7.5微米）和抽吸压力（10² - 10⁴达因/平方厘米）进行实验，以研究进入流动的细节。结果表明，细胞的外皮层维持着约0.035达因/平方厘米的小持续张力。该张力产生一个阈值压力，低于此压力细胞不会进入移液器。这些细胞的表面质膜似乎为表面扩张设定了一个上限，在微观的“褶皱”和“折叠”被拉平后达到该上限。用小移液器（小于2.7微米）抽吸细胞时，表面扩张的极限由细胞进入移液器的最大延伸确定；最终面积测量为初始球形面积的2.1至2.2倍。对于超过阈值的抽吸，对恒定压力的响应是与阈值以上的过剩压力成比例的连续流动，随着时间的推移只有很小的非线性，直到细胞完全进入移液器（对于移液器口径大于2.7微米）。利用在一篇相关论文中引入的理论模型（Yeung, A., and E. Evans., 1989, Biophys. J. 56:139 - 149），分析了进入流动响应与移液器尺寸和抽吸压力的关系，以估计细胞内部的表观粘度以及皮层流动阻力与细胞内部流动阻力的比值。发现表观粘度强烈依赖于温度，在23℃时约为2×10³泊，在37℃时较低值为1×10³泊，但在低于10℃时超过10⁴泊的极高值。由于细胞响应的离散性，无法准确确定皮层与细胞内部流动阻力的特征比值；然而，数据表明皮层对总流动阻力的贡献不大。
