In situ recording of the mechanical behaviour of cells in the chick embryo.

The changes of viscosity in different regions of the intact living early chick embryo were recorded by a new sensitive and non-invasive technique. In the heart, the very first yet invisible mechanical activity has been clearly detected and its further differentiation followed. In other regions, especially in the Hensen's node, spontaneous slow and oscillating mechanical activity has been observed. It has been shown that the undifferentiated embryonic tissue can as well respond to electrical, mechanical or chemical stimulations. The recorded changes have been interpreted as manifestations of the cell mechanical work i.e. active tension, cell shaping or movement. The technique represents a new tool for physiological and pharmacological studies of the undifferentiated embryonic cells and the early morphogenetic phenomena.