Prolonged Culture of Diploid Human Cells

Forty-four strains of human cells derived chiefly from skin, thyroid, and amnion were maintained for periods up to 9 months and 26 passages (average life span, 4 months). The doubling time for fibroblasts was about 4–5 days. No significant alteration in chromosome complement nor (in female strains) in sex chromatin incidence occurred. Cytoplasmic inclusions or nuclear abnormalities occurred in a few strains. All strains, if not otherwise terminated, underwent spontaneous degeneration, characterized by the accumulation of fine granules on the cell surfaces. No cases of spontaneous transformation occurred.