A Study of Certain General Conditions Leading to the Differentiation of Cells.

Abstract

In previous articles 1 , 2 I have given evidence to show that heart muscle cells may show a variety of reactions and changes in the tissue culture. It was shown further that each of these various forms of reactions and changes is a response of the cell to a given environment.

Under certain conditions these cells may stretch out from the fragment as an otherwise inactive syncytium. Again they are seen in other cultures migrating out as large mononuclear cells. Under other conditions they separate, flatten on the surface of the medium, grow actively, divide by mitoses and resemble actively growing mesenchyme or sarcoma cells. In other cultures they migrate from the fragment as single spindle-shape, mesenchyme-like cells and they have been seen to differentiate into rhythmically contracting cells. These latter cells have been removed from the environment suitable for such activity to one suitable for growth and division, and have changed from contracting cells to cells which flatten on the surface of the medium, grow actively and divide by mitosis.

A careful study of the condition suitable for these various activities has shown that the growing cells are cells flattened against a film of material which flows out from the fragment over the surface of the medium. The syncytia which stretch out from the fragments and the migrating spindle shaped heart muscle cells are cells which migrate directly into the clotted plasmatic medium from fragments which do not disintegrate and throw out a surface film. The large mononuclear cells are cells migrating into a clot of plasma which fails to coagulate to fibrin and serum but which is undergoing slow dissolution. The contracting cells are cells which are either stretched through the serum of the coagulated plasma clot between well formed fibrin fibrils and a surface film of material which has spread out from the fragment, or cells which are stretched through the serum between the fragment itself and the ends of fibrin fibrils.