Complementation in heterokaryons derived from a thymidine kinase deficient cell line and senescent human diploid cells
Norwood, T.H.; Rabinovitch, P.S.; Zeigler, C.J.
Federation Proceedings 38(5): 1868-1872
1979
ISSN/ISBN: 0014-9446 PMID: 428567 Document Number: 143136
Incorporation of [3H]thymidine was observed in both parental nuclei in heterokaryons resulting from the fusion of post-mitotic, "senescent" human diploid cells and a thymidine kinase-deficient murine cell line (3T3der-4E). The senescent nuclei displayed a sudden increase of activity approximately 4--6 hours after fusion. A moderate increase of thymidine incorporation was observed in 3T3der-4E cells cocultivated with but not fused to senescent cells, consistent with metabolic cooperation. Chromosome preparations of cultures fixed approximately 24 hr after fusion revealed the presence of hybrid metaphase cells containing almost the entire human complement. All of the identifiable human chromosomes were bi-armed, suggesting that the senescent nuclei were stimulated to reinitiate replicative DNA synthesis rather than repair synthesis in these heterokaryons.