Cortical wound healing in the amphibian egg: an electron microscopical study

Abstract

Changes following injury of the animal pole cortex of fertilized uncleaved eggs of Xenopus laevis were studied with the electron microscope. In the course of the healing process the egg surface bordering the exovate protruding from a tear wound is thrown into folds. Pigment granules aggregate in the region below the edges of the damaged area. Concomitantly filament arrays come into being there. Fuzzy material is present in a diffuse and in a condensed form. It coats the membrane in the region of the surface folds as well as membrane surfaces inside the exovate. Parts of the exovate surface are in the form of so-called “crenelated layer.” Probably this layer has a transitory sealing function and is homologous to the “new membrane” formed in wounded amoebae (18). The morphological alterations are interpreted as manifestations of membrane growth, active or passive contraction of filament arrays, and cytoplasmic coagulation. In this context Holtfreter's concept of a “surface coat” and his interpretation of cortical wound healing is reexamined.