Free energy of cell differentiation

Abstract

The rigid polarity of the coelentrate, hydra, has been examined based on the pattern of cell types found along the body column. The distribution of several cell types was determined by direct counts from histological sections. Treating the individual cell types as separate thermodynamic phases, the distribution of cell types was analyzed using a thermodynamic free energy function. (A steady state free energy function is derived to deal with cell differentiation.) Based on the analysis of the distribution of cell types with the free energy function, it is concluded that cell differentation in hydra is accompanied by mass flow of the components, which are responsible for cell differentiation and/or changes in the free energy of the cell as it is transformed from a precursor to a differentiated cell. The presence of marked differences in cell concentrations at the body extremities is explained as being due to the presence of gradients of growth factors and the continual movement of cells toward the body extremities.