Changes in the shape of epithelial embryonic cells of the spur-toed frog upon deformation of the cell layer

A quantitative study was made of changes in the shape of cells in double explants of the blastocoel roof of the clawed frog gastrula within the first four hours after artificial bending of explants. It was found that, on the concave (contracted) side of explants, epithelial cells stretched out, and in many of them the apical surface contracted, whereas on the convex (stretched) side the cells remained isodiametric. The maximal difference in the apical index between epithelial cells located on the concave and convex sides was observed after 2 h of explant cultivation; by 2 h the artificially produced curvature of the explant further increased. Endocytosis on the concave side was more active than on the convex side. Experiments with inhibitors modulating the behavior of the actomyosin complex showed that unimpeded functioning of myosin II is more important for the apical contraction and elongation of cells than proper structural organization of the actin backbone.