HISTOCHEMICAL AND ULTRASTRUCTURAL STUDIES ON HELA CELL CULTURES EXPOSED TO SPINDLE INHIBITORS WITH SPECIAL REFERENCE TO THE INTERPHASE CELL

Mammalian cells of the HeLa (S3) strain, when exposed to spindle inhibitors, have been found to undergo several morphological transformations during interphase as well as during mitosis. Some of these have been studied both histochemically and ultrastructurally. The lysosomes, represented by the multivesicular bodies in HeLa cells, form clusters and become circumferentially disposed instead of occupying the polarized juxtanuclear position characteristic of these organelles. In the electron microscope it is seen that they have acquired a dense osmiophilic core that is separated from the bounding unit membrane by an electron lucent halo. The Golgi apparatus fragments under the influence of spindle inhibitors and also takes up a circumferential distribution in a pattern similar to that of the lysosomes. On the ultrastructural level, no significant modifications in this organelle are seen. Also noted in the interphase cell are numerous 60-80 Å fibrils coursing through the cytoplasm as well as a paucity of spindle our microtubules. A striking similarity has been pointed out between the behavior of the lysosomes in the drugtreated interphase cell and the untreated, normal mitotic cell. A possible explanation of some of the changes noted has been given in terms of an interruption of protoplasmic flow resulting from the disappearance of microtubules.