Cell cleavage model based on active microfilaments contraction

The current experiments suggest that the asters of themitotic apparatus determine the position of the contractile ring duringcytokinesis. Ultrastructural observation indicates that microfilaments arebound to the cortex with cross bridges. Microfilaments initially randomlyorientate and homogeneously distribute on the membrane. At late anaphase,the microfilaments distribution at the equator plane is changed from randomand uniform to aligned parallel. In the present study, on the basis ofZinemanas and Nir's hydrodynamics model, a new model was constructed tostimulate the relationship between the active microfilaments redistributionby biochemical stimulus from the MA asters and cytokinesis. The effectivecoefficient m due to biochemical stimulus was incorporatedinto the model, and the distribution function c is modifiedto move with the plasma membrane motion. In the model, it is assumed thatthe biochemical stimulus from the asters inhibit the formation of activefilaments through a very simple kinetic scheme; the reorientation of activemicrofilaments follows the cytoplasm flow; the motion of active filamentsfollows the plasma membrane's motion due to passive deformation. Thecell-division is driven by the anisotropic tension of surface. The surfacetension consists of two parts: one is the contractile force of the activefilaments paralleling to their symmetry axis, the other is the passivedeformation tension of the membrane by cytoplasm flowing. The numericalresults showed that the active filaments by redistribution due tobiochemical stimulus and actively contraction may play a crucial role incell division. Compared with Zinemanas and Nir's model, the results of ourmodel are more correspondent with the Hiramoto's experimental results.