Morphological studies on the enucleation of colchicine-treated L-929 cells

Treatment of mammalian cells that are growing in monolayer culture with 2 μg/ml of colchicine for 48 hr induces fragmentation of the nucleus, a process termed micronucleation. If these treated cells are centrifuged in medium containing 10 μg/ml of cytochalasin B, the individual karyomeres are removed in a single strand. Once removed, each karyomere and its associated cytoplasm has been termed a "microcell" [Ege and Ringertz (1974) Exp. Cell Res. 87, 378] or "microkaryoplast" [Shay and Clark (1975) 33rd Annu. Proc. Electron Microscopy Soc. Amer., p. 306]. Each microkaryoplast contains a small amount of decondensed chromatin surrounded by a nuclear envelope, a thin band of cytoplasm containing ribosomes and mitochondria and limited by an intact plasma membrane. This procedure provides a means of obtaining part of the genome of a cell packaged in such a way that allows its introduction into another cell without damage and may provide useful information for the study of nuclear-cytoplasmic interactions.