Cultures of chick heart fibroblasts were perfused with the chelating agent ethylenediaminetetraacetic acid (EDTA). Cellular responses were observed under phase optics and recorded by time-lapse cinemicrography.

In interphasic fibroblasts, EDTA induces cellular contraction followed by continuous protrusion and retraction of ectoplasmic blebs ("surface bubbling"), formation of motile vermiform processes, and production of rotatory ectoplasmic swellings. The contraction and surface bubbling closely resemble the metaphase contraction and "anaphase bubbling" normally displayed by cultured fibroblasts.

In dividing cells, EDTA does not affect metaphases, but anaphase bubbling appears and persists; telophasic expansion and migration of daughter cells are prevented. Initiation of new mitoses occurs during and after exposure to EDTA.

No cellular responses are induced by calcium, magnesium, or ferrous chelates of EDTA. The EDTA elects are completely reversible on removal of the chelating agent, resulting in the restoration of the normal interphasic cell form and the normal expansion and migration of mitotic products.

The EDTA effects are interpreted to result from the chelation and removal of divalent cations from the cell surface. Possible relations to surface activities observed in normal mitosis are considered, and an hypothesis is presented regarding the role of the developing spindle in cation transfer.

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