MIGRATING CELLS - LIVING LIQUID-CRYSTALS

Two conditions are necessary to built up a condensated state out of el ementary units: (i) interaction between the elementary units and (ii) motion of the elementary units. A new type of liquid crystal is found by using migrating cells (human granulocytes) as elementary units. The se cells show no interaction or a weak repulsion at high calcium conce ntration (2.5 nM). But at low calcium concentration (< nM) the cells a ttract other and form a polar nematic liquid crystal. First, the machi ne for the directed movement is investigated phenomenologically. The d irection of migration is guided by a cellular automatic controller. It can be characterized by two machine coefficients: (i) the response of the automatic controller is proportional to the strength of the extra cellular guiding field times a cellular machine coefficient, and (ii) the random movement is induced by stochastic processes in the cellular machinery. These cellular stochastic processes are equivalent to the thermal motion of inert particles. The analogy to the Boltzmann statis tics is evident. In the next step, the cell-cell communication is inve stigated. During one machine cycle, the cell can release metabolic mol ecules which attract other cells via chemotaxis. Galvanotaxis is anoth er mechanism for the cell-cell interaction since every cell is surroun ded by an electric field. The distance dependent cell-cell interaction is determined from the pair correlation function.