Continuum mechanical model of leukocytes during protopod formation.
Continuum mechanical model of leukocytes during protopod formation.
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原生动物形成过程中白细胞的连续力学模型。
DOI：
10.1115/1.3138448
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Skalak,R
中科院分区：
文献类型：
--
作者：
Schmid-Schönbein,GW;Skalak,R
提出了一种新的白细胞原足伸展的连续介质力学理论。原生生物的形成是一个活跃的过程，它是变形虫在基质上置换的基础。当白细胞附着在底物上和自由悬浮在血浆中时，都可能形成原足。因此，所需的能量来自电池本身。原足类没有颗粒和其他细胞器，它们具有细小的纤维状超微结构，并被细胞膜覆盖。它们以大约5μm/分钟的速度生长，直到长度达到4-5μm。在此期间，颗粒通过布朗运动通过原足底部重新进入。微吸管实验表明，白细胞中的原生质具有粘弹性，而原足更坚硬，表现出弹性行为。我们提出了一个基于细胞内肌动蛋白基质聚合的连续统理论，该聚合导致凝胶具有择优取向。它是由Ca++通过细胞膜的局部区域内流而触发的，聚合反应沿着聚合原始体底部的界面发生。当细胞质通过界面时，它既受到由于颗粒排除而产生的体积应变，也受到由于肌动蛋白分子排列而产生的剪切应变。聚合提供了一种导致原足突起和细胞变形的活动力。原足类的底部位于界面上未聚合的细胞质上。由于外部的质液和细胞膜，如果它不被拉紧，提供的阻力很小，原足动物的投射继续向外进行，膜同时展开。另一方面，在渗透膨胀的细胞中，膜在张力下提供相当大的阻力，肌动蛋白聚合向内进行。建立了一般方程组，并讨论了一些特解。
A new continuum mechanical theory for protopod extension in leukocytes is developed. Protopod formation is an active process which is the basis for amoeboid displacement on substrates. Leukocytes may form protopods both when adhering to a substrate and when freely suspended in plasma. Therefore the required energy is derived from the cell itself. Protopods are depleted of granules and other organelles, they have a fine fibrillar ultrastructure, and they are covered by a cell membrane. They grow at about 5 μm/min until they reach a length of 4–5 μm. A period of protopod retraction follows during which granules re-enter via the protopod base by Brownian motion. Micropipette experiments have indicated that the protoplasm in the leukocyte has viscoelastic properties, whereas the protopod is stiffer and shows elastic behavior. We propose a continuum theory based on the polymerization of the actin matrix in the cell which results in gelation with a preferred orientation. It is triggered by influx of Ca++across local regions of the cell membrane and the polymerization occurs along an interface at the base of the polymerized protopod. As cytoplasm passes through the interface it is subject both to a volumetric strain due to exclusion of granules and a shear strain due to alignment of actin molecules. The polymerization provides an active force leading to projection of the protopod and cell deformation. The base of the protopod rests on the unpolymerized cytoplasm along the interface. As the external plasma medium and the cell membrane, if it is not stretched taut, offer little resistance, the projection of the protopod proceeds outward with simultaneous unfolding of the membrane. On the other hand, in osmotically swollen cells the membrane offers considerable resistance as it is under tension and the actin polymerization proceeds inward. A general set of equations are formulated and some special solutions are discussed.