Fischer Thomas M, Korzeniewski Rafal
Department of Physiology, Rheinisch Westfälische Technische Hochschule Aachen University, Aachen, Germany.
Department of Physiology, Rheinisch Westfälische Technische Hochschule Aachen University, Aachen, Germany.
Biophys J. 2015 Mar 24;108(6):1352-1360. doi: 10.1016/j.bpj.2015.01.028.
Red cells suspended in solutions much more viscous than blood plasma assume an almost steady-state orientation when sheared above a threshold value of shear rate. This orientation is a consequence of the motion of the membrane around the red cell called tank-treading. Observed along the undisturbed vorticity of the shear flow, tank-treading red cells appear as slender bodies. Their orientation can be quantified as an angle of inclination (θ) of the major axis with respect to the undisturbed flow direction. We measured θ using solution viscosities (η0) and shear rates (γ˙) covering one and three orders of magnitude, respectively. At the lower values of η0, θ was almost independent of γ˙. At the higher values of η0, θ displayed a maximum at intermediate shear rates. The respective maximal values of θ increased by ∼10° from 10.7 to 104 mPas. After accounting for the absent membrane viscosity in models by using an increased cytoplasmic viscosity, their predictions of θ agree qualitatively with our data. Comparison of the observed variation of θ at constant γ˙ with model results suggests a change in the reference configuration of the shear stiffness of the membrane.
悬浮于比血浆粘性大得多的溶液中的红细胞，当剪切速率高于阈值时被剪切，会呈现出几乎稳定的取向。这种取向是红细胞周围膜的运动（称为“坦克履带式运动”）的结果。沿剪切流未受干扰的涡度观察，进行“坦克履带式运动”的红细胞呈现为细长体。它们的取向可以量化为长轴相对于未受干扰流动方向的倾斜角（θ）。我们分别使用涵盖一个和三个数量级的溶液粘度（η0）和剪切速率（γ˙）来测量θ。在较低的η0值时，θ几乎与γ˙无关。在较高的η0值时，θ在中等剪切速率下出现最大值。θ的各自最大值从10.7到104毫帕秒增加了约10°。通过使用增加的细胞质粘度来考虑模型中不存在的膜粘度后，它们对θ的预测在定性上与我们的数据一致。在恒定γ˙下观察到的θ变化与模型结果的比较表明，膜剪切刚度的参考构型发生了变化。
