[Morphomechanical Factors in Gastrulation Process and Differentiation of Embryonic Tissue of Xenopus laevis].

Effect of mechanical stretch on the differentiation of axial anlages and Chordin gene expression was studied in sandwich explants prepared from embryonic tissues of Xenopus laevis at the early gastrula stage in two variants: with dissected or intact dorso-medial region. In the first case, convergent cell movements were suppressed and properly organized axial organs (notochord and somites) were almost completely absent. However, they developed if the explants of such type were artificially stretched in the ventro-dorsal direction.

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

A quantitative study of changes in the shape of cells of double explants of the tectum of gastrule blastocoele of the spur-toed frog within the first four hours after the artificial bending of explants has been performed. It was found that, on the concave (contracted) side of explants, epithelial cells stretch out, and the apical surface of many of these cells contracts, whereas on the convex (stretched) side they remain isodiometric. The maximal difference between the values of the apical index of epithelial cells located on the concave and convex sides was observed after 4 h of the cultivation of explants.

[Changes in topology and geometry of the embryonic epithelium of Xenopus during relaxation of mechanical tension].

The paper presents the results of statistical evaluation of the changes of cellular apex connections, apical angles, and apical indices of ventral cells of the epiectodermal gastrula of Xenopus during the first HC-four hours after the relaxation of mechanical tension. In the unrelaxed epithelium, an overwhelming majority of cells have three apical connections, apical angles close to 120 degrees, and apical indices around one (isodiametric cells); after relaxation, the number of cells with more than three connections, the number of apical angles deviating substantially from 120 degrees, and the percentage of columnar cells with high apical index increase. Apices with more than three connections tend to gather in enclosed groups, forming a smooth line of cell walls.