Antibody against tubulin from porcine brain was used to evaluate the immunological cross reactivity of tubulin from a variety of animal and plant cells. Indirect immunofluorescence microscopy revealed microtubule-containing structures including cytoplasmic microtubules, spindle microtubules, cilia and fIagella. Thus tubulin from diverse species of both mammals and plants show immunological cross-reactivity with tubulin from porcine brain. Results obtained by immunofluorescence microscopy are whenever possible compared with previously known ultrastructural results obtained by electron microscopy.

Immunofluorescence microscopy using antibody against actin has been used to study the expression of microfilamentous material in cells of a cloned mouse 3T3 line during cytochalasin A (CA) induced cell contraction. A conspicuous modification of the structure of the microfilament bundles is observed. Actin containing rod-like elements can be visualized both by phase contrast and immunofluorescence microscopy. These actin containing rods are of rather defined length (approximate length 5 μm) and seem to be derived as subunits from the original microfilament bundles. In some cells the rods were in the same orientation as the microfilament bundles in control cells, whereas other cells showed scattered arrangements. The phenomenon suggests intrafibrillar periodical heterogeneity in the microfilament bundles.

Structures binding an antibody against tubulin from porcine brain were localized in the giant anastral mitotic apparatus of endosperm cells of the monocotyledonous plant, Leucojum aestivum, by indirect immunofluorescence microscopy. Both continuous and chromosomal spindle fibers were strongly stained. Postive fluorescence was also noted in polar cap regions and, in prometaphase stages, to some extent at the fragmented nuclear envelope. Intermingling and branching of subfiber elements was frequently noted.