[The morphological criteria and proposed mechanisms of cortical contractility in oocytes of the clawed toad].

It is proposed to consider certain states of the cortical actin cytoskeleton corresponding to various stages of oocyte maturation as morphological criteria of the cortical contractility during progesterone-induced oocyte maturation. In the definitive oocyte, the cortical microfilaments form an anisotropic network, while in the mature egg, they form an isotropic disorganized network and, at the moment of contraction, bundles. Factors of the actin cytoskeleton transformation are discussed: actin-binding proteins, protein kinases, and bivalent ions. The data are given on the presence and distribution of the actin-binding protein vinculin in the cortex of the oocyte.