The binding of cations to the surfaces of cells from early chick blastoderms

Cells of the early chick blastoderms are either preparing for or undergoing regulated morphogenetic movements which culminate in the formation of a three-layered embryo. Information on the changes in the physical-chemical properties of cell surfaces may help in the understanding of this process. The binding of magnesium, manganese, strontium, barium and lanthanum to surfaces of early embryonic cells was estimated by the changes induced by these cations in the cells' electrophoretic mobilities (EPM). Cells show a positive EPM at concentrations of MgCl2 and MnCl2 at 3 X 10(-2) M while SrCl2 and BaCl2 were not able to reverse the cells' charge at concentrations up to 6 X 10(-2) M. CaCl3 reversed the cells' EPM at concentrations as low as 5 X 10(-3) M. Our results suggest that the surfaces of early embryonic cells have a high affinity for Mg and Mn. This is indicated by a reversal of polarity which cannot be detected in cells of differentiating or adult tissues at the cation concentrations used in these experiments.