Cytokinesis in Animal Cells

Abstract

This chapter discusses the processes that accomplish cytoplasmic division in animal cells. Recognition of the importance of cytokinesis came with the acceptance of the cell theory, and early attention was focused upon identification of the physical mechanism and determination of the role of visible cell parts. The results of experimentation, biophysical analysis, and ultrastructural study of mitotically dividing animal cells support the concept of a common basic mechanism. The mitotic apparatus normally establishes the division mechanism, but pairs of cytasters, sperm asters, and asters detached from the spindle can induce furrows in eggs. Moreover, furrow establishment depends upon a specific geometrical relationship between the mitotic apparatus and the equator. No special geometrical relationship between the mitotic apparatus and the poles is required. The circumstances of furrow establishment and the properties and behavior of the furrow region indicate that the difference arises by an increase in equatorial tension rather than by polar relaxation. Data from direct analysis of the biophysical properties of the furrow surface are meager. There is no clear understanding of the way in which any of the ultrastructural elements, thus far described, contribute to the observable events in living, dividing cells.