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Ultrastructural Study of the Persistence of Colchicine-induced Cytological Changes in Harding-Passey Melanoma¹

Department of Anatomy, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada

Electron microscopic observations were undertaken on Harding-Passey melanoma in control tumors, colchicinetreated tumors, and tumors that were passed through five transplantations in mice subsequent to colchicine treatment.

The untreated Harding-Passey melanoma tumor was composed of pleomorphic cells the cytoplasm of which contained tubulovesicular mitochondria and numerous free and membrane-attached ribosomes. Type A virus particles were observed in both mitotic and interphase cells. Colchicine-treated tumors exhibited several typical colchicine mitotic cells arrested in metaphase. A most significant feature of the colchicine administration was the appearance of microfilaments in both interphase and mitotic cells, a feature not observed in cells of the untreated tumor.

Electron microscopy of colchicine-treated tumors carried through five transplantations at biweekly intervals revealed the presence of microfilaments in tissues fixed at each of the transplantations.

It therefore appears that the cytological effects of colchicine resulting in the appearance of filaments in melanocytes of the Harding-Passey melanoma are more enduring than they were initially presumed to be.

¹ Supported in part by the National Cancer Institute of Canada and the Medical Research Council of Canada.

² To whom requests for reprints should be addressed, at Department of Anatomy, School of Medicine, 730 William Ave., Winnipeg, Manitoba, Canada R3E OW3.

Received 2/14/77. Accepted 10/11/77.