Dielectrospectroscopic monitoring of early embryogenesis in single frog embryos

Dielectric spectroscopy has been used to monitor the early embryogenesis of frog (Xenopus laevis) eggs. The dielectric spectra of a single egg in suspension over the frequency range 10 Hz to 10 MHz were collected at various stages of its development. The uncleaved egg showed a dielectric dispersion with a narrow distribution of relaxation times. After the first cleavage, the dielectric spectra were mainly composed of two subdispersions. In the cleavage process, up to the morula stage, changes in the spectra were quantitatively simulated by the 'cell-aggregate' model in which the embryo is regarded as a concentrated suspension of shell-spheres that correspond to the blastomeres (i.e. the cells within the embryo). In the stages from the morula to the blastula, the changes in the dielectric spectra were explained as due to a reduction in the size of the blastomere accompanied by an expansion of the blastocoel (i.e. the central cavity in the embryo) using the 'vesicle-inclusion' model that is a cell aggregate covered with a less conducting shell corresponding to the outermost layer of tightly interconnected cells.