Response of the Cortical Cytoskeleton of Paramecium caudatum to Merotomy

Abstract

Summary Changes occurring within 2 min of merotomy in the cortical cytoskeleton of fragments cut from Paramecium caudatum were studied in thin sections. None of the microtubular components of the cortical cytoskeleton showed alterations suggestive of functional reorganization of microtubules and attributable to the mechanical damage made to the cell. Marked changes, however, were found in the amount and distribution of the infraciliary lattice. The bands of microfilaments were thicker and the meshes between them were reduced. This thickened layer penetrated deep into the wound under a newly-formed plasma membrane. The granulofibrillar meshwork, which fills the polygonal ridges in an intact cortex, was completely disorganized in fragments. Its remnants were always found in association with the plasma membrane or alveolar membranes. Cross-striated bands of microfilaments were retained only at the margin of the wound where they were attached to alveolar debris. Kinetodesmal fibrils maintained their integrity but their regular pattern of longitudinal bands was disturbed. The epiplasm (membrane skeleton) in the remnants of alveolar membranes was preserved and found also in some regions of the newly-formed plasma membrane. Little information is available on the chemical composition of these microfilamentous components and their function could only be the object of speculations. For instance the character of changes in the infraciliary lattice might suggest that its thickening was due to polymerization of new microfilaments which, together with wound contraction, were involved in the process of healing.