Transformation, remodeling and dissociation of achromatic fibres by butyric acid in mitoses of cleaving eggs. Effects of associated antitubulin substances.

A mM solution of butyric acid transforms the achromatic apparatus of segmentation mitoses: asters are reduced or suppressed, cytokinesis is inhibited before mitosis, spindle fibers are broken and fan out progressively in the equatoria; region becoming radially oriented instead of axially. The results are either: 1) hollow fibrillar systems, 2) radiating spindle systems, apparently pluripolar, 3) dissociated fibrillar systems, depending on the phase of the mitotic cycle in which the butyric acid acted. Colchicine 2.5 X 10-3 M and vincaleukoblastine 2 X 10-4 M cause the depolarized nuclei and mitoses to migrate towards the animal cortex and the furrows, if they are administered before the abnormal systems produced by butyric acid are fully formed. Once formed, these systems are usually unchanged by administration of these drugs. Thus their formation appears to depend on microtubule assembly, since colchicine and VLB can prevent it.