Colchicine Effects on Microtubules and Membrane Movements in the Cytoproct-to-Cytopharnyx Region of Paramecium Caudatum

Abstract

Microtubules, within the past decade, have received a great deal of interest from numerous investigators. Occurring in almost all eucaryotic cells (Slautterbach, 1963; Porter, 1966), these organelles have been implicated in many cell processes. They appear to function in the development and maintenance of cell form (Byers and Porter, 1964; Arnold, 1966), appearing, for example, in the frame- work of cilia and flagella and in the cortical ridges of ciliates and flagellates (Sommer, 1965; Allen, 1967), in neurons (Peters and Vaughn, 1967; Porter, 1966), and in the mitotic spindle (Kane, 1967). In morphology, microtubules have a tubular cross-section. They are 210-250 A in diameter (Tilney, 1968) and can be resolved into 12-13 protofilaments which in turn can be resolved into rows of globular subunits about 40 A wide (Grimston and Klug, 1966; Kieffer, et al., 1966). In negatively stained preparations, microtubules tend to break rather than bend under excessive stress.