Studies on the surface of chick blastoderm cells. II. Electron microscopy of surface binding characteristics

The surfaces of cells from the early embryo of the chick were examined with the electron microscope using histochemical techniques in order to determine the distribution of cell surface material. The use of lanthanum nitrate as a stain for protein‐polysaccharide showed that in whole embryos the surface layer was present in areas of close membrane apposition, but relatively sparse where the membranes bounded large intercellular spaces. On cells freshly dissociated with EDTA, this technique demonstrated a very uniform layer over the surface, possibly indicating some redistribution. Close examination of the lanthanum stained material in whole embryos revealed the presence of periodicities about 180 Å in diameter. In correlation with a progressive reduction of electrophoretic mobility, demonstrated previously, from embryonic stage 1 to stage 5, some decrease in the affinity of the surface for lanthanum and colloidal iron was observed.