© 1978 by The Society for Integrative and Comparative Biology
Fine Structural Analysis of Animal Cell Surfaces: Membranes and Cell Surface Topography
Department of Biology, California State University Northridge, California 91330
Current research on the mechanism of transmembrane regulation of topographic modulation at the cell surface is described for the sea urchin egg and Sarcoma 180 ascites tumor cells of Swiss Webster white mice. The transmembrane system is characterized in terms of three components: glycocalyx, membrane, and cytofibrillar structures. The importance of membrane molecular architecture per se relative to the other surface components is assessed in terms of freeze fracture analysis of both cell types as well as concanavalin A (ConA)-mediated long term agglutination, cytochalasin B effects, and other drug-induced changes at Sarcoma 180 cell surfaces. A quantitative and qualitative assessment of intramembranous particle (IMP) sizes and density distributions reveals intrinsic structural changes of the fusing membranes at cortical reaction during sea urchin egg fertilization and also with the post-fertilized accumulation of surface microvilli. Comparable changes in IMP are noted for microvillus retraction and membrane smoothing in Sarcoma 180 cells under a variety of experimental conditions. On the other hand, chemical perturbation of S-180 cell surfaces reveals a rather non-ubiquitous, though identifiable, involvement of microfilaments and no microtubule involvement in these topographic changes. These observations suggest that the plasma membrane is a dynamic structure poised between "restrictive" and "less restrictive" states of fluidity or deformability and, hence, is a determinant component in topographic change.