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 susp ension over the frequency range 10 Hz to 10 MHz were collected at various s tages of its development. The uncleaved egg showed a dielectric dispersion with a narrow distribution of relaxation times. After the first cleavage, t he dielectric spectra were mainly composed of two subdispersions. In the cl eavage process, up to the morula stage, changes in the spectra were quantit atively simulated by the 'cell-aggregate' model in which the embryo is rega rded as a concentrated suspension of shell-spheres that correspond to the b lastomeres (i.e. the cells within the embryo). In the stages from the morul a 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 expansio n of the blastocoel (i.e. the central cavity in the embryo) using the 'vesi cle-inclusion' model that is a cell aggregate covered with a less conductin g shell corresponding to the outermost layer of tightly interconnected cell s.