ARTICLE

THE FINE STRUCTURE OF THE NUCLEOLUS IN MITOTIC DIVISIONS OF CHINESE HAMSTER CELLS IN VITRO

¹ From the Section of Cytology, Department of Biology, The University of Texas M. D. Anderson Hospital and Tumor Institute, Houston, Texas

The nucleolus of Chinese hamster tissue culture cells (strain Dede) was studied in each stage of mitosis with the electron microscope. Mitotic cells were selectively removed from the cultures with 0.2 per cent trypsin and fixed in either osmium tetroxide or glutaraldehyde followed by osmium tetroxide. The cells were embedded in both prepolymerized methacrylate and Epon 812. Thin sections of interphase nucleoli revealed two consistent components; dense 150-A granules and fine fibrils which measured 50 A or less in diameter. During prophase, distinct zones which were observed in some interphase nucleoli (i.e. nucleolonema and pars amorpha) were lost and the nucleoli were observed to disperse into smaller masses. By late prophase or prometaphase, the nucleoli appeared as loosely wound, predominantly fibrous structures with widely dispersed granules. Such structures persisted throughout mitosis either free in the cytoplasm or associated with the chromosomes. At telophase, those nucleolar bodies associated with the chromosomes became included in the daughter nuclei, resumed their compact granular appearance, and reorganized into an interphase-type structure.

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• Azum-Gelade, M., Noaillac-Depeyre, J, Caizergues-Ferrer, M, Gas, N (1994). Cell cycle redistribution of U3 snRNA and fibrillarin. Presence in the cytoplasmic nucleolus remnant and in the prenucleolar bodies at telophase. J. Cell Sci. 107: 463-475 [Abstract]  

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