The Biochemical Stimulus And Mechanical Behavior Coupling Under The Process Of Eukaryote Division

Cell is the basis unit of all living organisms, which can reproduce itself exactly. Mitosis is a process of nuclear division in which replicated DNA molecules of each chromosome are faithfully partitioned into two nuclei. Mitosis is usually accompanied by cytokinesis, a process by which a dividing cell splits into two, partitioning the cytoplasm into two packages. Meanwhile cell changes of disease or carcinoma might be occurred during the phase. Cellular reproduction is more than just a mean of reproducing cells; it is the basis for reproducing more organisms through the formation of cellular gametes. As an important research field of cell biomechanics, cell division is getting increasing interests.Since the study of cell function generally requires the use of considerable instrumentation, the investigator is physically removed from the subject being studied. The analysis results of experiments are limited by investigators' knowledge structure. To a large degree, cells are like tiny black boxes. All investigators have developed many ways to probe the boxes, but they are always groping in an area that cannot be fully illumined. The general mechanism of cell division remains uncertain. In this paper, on the basis of detailed studies on lots of information about mitosis and cytokinesis, a new biomechanics model has been established aiming to obtain a reasonable understanding the relation between the transfer of biochemical stimulus and mechanical action of cytokinesis. The main works are as follows:1. A model of cell membrane received biochemical stimulus from the asters of the mitotic apparatus was established. At first, the length of astral microtubules was assumed to obey a normal distribution. Second, the condition about receivedbiochemical stimulus was that the length of microtubules is longer than the distance between the aster and the point. Third, the stimulus density was modified by excluding the part that microtubules from an aster reach the opposite cell surface over the spindle area.2. A model was constructed to simulate the relationship between the membrane phospholipid redistribution and polymerization of cytoskeleton. In this model, gradients of stimulus density and diffusion drive phospholipid motion on the surface. The numerical results showed that phospholipid accumulation near equator plane triggers the initial formation of contractile -ring.3. Considering the cytoplasm and cell environment as Newtonian fluid with Viscosity μ and μ', the cytoplasm fluid was simplified as Stokes fluid with low Reynolds number. For numerical calculation, the governing equations were converted into boundary integral equations for boundary velocity and force.4. Mooney-Rivlin material model was used to describe the constitutive relation of cell membrane. In the model, the membrane confines the cytoskeleton and bring microfilaments into motion.5. The redistribution and reorientation of microfilaments model was constructed. During cytokinesis, the microfilaments was reoriented due to the flow of cytoplasm. The microfilament only exerts a time-dependent contractile force parallel to their symmetry axis. Therefore the cortical tension depends both on microfilaments active contract and membrane passive deformation. The anisotropic cortical tension is provided for finishing the cytokinesis.6. Under the boundary conditions of no-slide on the interface, the points with same spatial coordinates in membrane, microfilament and cytoplasm respectively have same velocity, and so the coupling models can be resolved.These numerical results strongly suggested that this model describes cytokinesis process closely and comprehensively.