STATISTICAL MECHANICS OF LIVING STATE

本研究的目的是提取一些表征生命状态的力学性质。为此，我们研究了从游离细胞聚集体中再生水螅的过程。游离细胞最初是一个无序的系统，它不像多细胞动物那样处于生命状态。随着时间的推移，组成细胞开始相互关联，最终形成一个处于生命状态的系统，这个转变是由多个过程组成的，其中我们阐明了以下事实：（1）动物首先通过细胞分选过程形成内部和外部细胞层。本文对细胞分选机理进行了实验研究，并利用基于微分粘附的物理模型进行了模拟，发现了两者的差异，提出了一个新的研究方向。（2）细胞分选完成后，细胞的头部、脚部等结构基本定型。在这个过程中，测量了细胞的运动，发现细胞的运动并不是为了产生结构，而是细胞的作用被重新确定。（3）测定了水螅再生所需的最小组织尺寸，并用扩散-反应机制等多种因素解释了临界尺寸。

The aim of the research project is to extract some statistics-mechanical properties which characterize living states.For this aim we studied regeneration process of hydra from dissociated cell aggregate.A dissociated cell is initially a disorganized system which is not in a living state as a multi-cellular animal.As the time elapses,the constitute cells start having correlation and finally forms a system which is in a living state.This transition is composed of various processes among which we clarified the following facts;(1)An animal first forms an internal and an external cell layer by cell sorting process. The mechanism of cell sorting was experimentally investigated and simulated by a physical model based on differential adhesivily.The difference of the two found proposed a new future problem. (2)After the cell sorting process was finished,the structures such as head and foot were formal. The motion of the cells were measured during this process.It was found that the cells do not essentially move to produce structure,but that the role of cells is newly determined. (3)Minimum tissue size required to regenerate a hydra was measured.The critical size was explained by several factors including a diffusion-reaction mechanism.