CORTICAL SHELL-LIQUID CORE MODEL FOR PASSIVE FLOW OF LIQUID-LIKE SPHERICAL CELLS INTO MICROPIPETS
CORTICAL SHELL-LIQUID CORE MODEL FOR PASSIVE FLOW OF LIQUID-LIKE SPHERICAL CELLS INTO MICROPIPETS
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DOI：
10.1016/s0006-3495(89)82659-1
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发表时间：
1989-07-01
影响因子：
3.4
通讯作者：
EVANS, E
中科院分区：
文献类型：
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作者：
YEUNG, A;EVANS, E
许多非贴壁细胞以球体形式存在于悬浮液中，当被吸入移液管时，在质膜包膜的固定表面积限制内像液体一样连续变形。释放后，这些细胞最终恢复其球形。因此，移液管抽吸测试提供了一种有用的方法来测定此类细胞的表观粘度。为此，我们分析了类液体模型单元在恒定吸入压力下无惯性地流入管中的情况。该细胞被建模为由独特的皮质壳封装的均匀液体核心。分析方法采用变分方法，最大限度地减少由皮质壳运动方程定义的边界条件的误差，其中试验函数是液体核心内部流场的精确解。对于具有持续张力的各向异性液体皮层的特殊情况，我们确定了对流量的通用预测，该流量由超压（高于皮层张力建立的阈值）和核心粘度（入口动态阻力的倒数）之比缩放。结果取决于移液管与细胞大小的比率以及表征皮层中的粘性流阻力与细胞质核心内部的粘性流阻力之比的参数。当移液管尺寸接近细胞外段直径时，进入速率显着增加。皮层中的粘性耗散对小尺寸管的入口流阻有很大影响，但对大管影响不大。这表明，在足够的实验分辨率下，用不同尺寸的移液管测量细胞进入流量可以确定皮层与细胞的耗散比以及细胞质核心的表观粘度。
Many nonadherent cells exist as spheres in suspension and when sucked into pipets, deform continuously like liquids within the fixed surface area limitation of a plasma membrane envelope. After release, these cells eventually recover their spherical form. Consequently, pipet aspiration test provides a useful method to assay the apparent viscosity of such cells. For this purpose, we have analyzed the inertialess flow of a liquid-like model cell into a tube at constant suction pressure. The cell is modeled as a uniform liquid core encapsulated by a distinct cortical shell. The method of analysis employs a variational approach that minimizes errors in boundary conditions defined by the equations of motion for the cortical shell where the trial functions are exact solutions for the flow field inside the liquid core. For the particular case of an anisotropic liquid cortex with persistent tension, we have determined universal predictions for flow rate scaled by the ratio of excess presure (above the threshold established by the cortical tension) and core viscosity which is the reciprocal of the dynamic resistance to entry. The results depend on pipet to cell size ratio and a parameter that characterizes the ratio of viscous flow resistance in the cortex to that inside the cytoplasmic core. The rate of entry increases markedly as the pipet size approaches the outer segment diameter of the cell. Viscous dissipation in the cortex strongly influences the entry flow resistance for small tube sizes but has little effect for large tubes. This indicates that with sufficient experimental resolution, measurement of cell entry flow with different-size pipets could establish both the cortex to cell dissipation ratio as well as the apparent viscosity of the cytoplasmic core.