New membrane formation and intercellular communication in the early Xenopus embryo. II. Theoretical analysis.

In conjunction with a previous analysis of the electrical networks formed by the Xenopus embryo during development from the 2-cell stage to the 16-cell stage, some theoretical aspects are investigated. A computer simulation method for the derivation of the specific membrane resistances from the measured equivalent resistances between different compartments of a multicellular biological system is described in detail. The interdependence of the equivalent junctional and nonjunctional resistances, and the possible role of the blastocoel in intercellular communication are analyzed. Assuming that no direct pathways exist between nonadjacent cells, the equivalent junctional and nonjunctional resistances, as well as the resulting coupling ratios are calculated for all pairs of cells in the 4-cell, 8-cell and 16-cell embryo. Previous studies on electrotonic coupling in the early Xenopus embryo are discussed.