Liquid nitrogen storage and human chromosome composition of human-mouse hybrid cells

The human chromosome complement of eight human-mouse hybrid cell strains was studied with fluorescent banding before and after rejuvenation of these cells from liquid nitrogen storage. The karyotype remained essentially stable in several cell strains, while in others both human and mouse chromosomes were lost. A third group demonstrated loss of only human chromosomes. The loss of particular human chromosomes after the rejuvenation process was shown to be statistically significant in four of the eight hybrid cell strains. These preliminary results suggest that karyotypic constancy cannot be assumed in human-mouse hybrid cells subjected to rejuvenation from liquid nitrogen storage.