Unscheduled DNA synthesis in cells of different shape in fibroblast cultures from donors of various ages.

Human fibroblast cultures derived from normal donors of different ages were examined for the proportion of spindle-shaped, sail-shaped, and large pleomorphic cells which constitute the cultures, and the capacities of these cells for unscheduled DNA synthesis (UDS). The large pleomorphic cells were most abundant in all cultures, followed in abundance by the sail-shaped and spindle-shaped cells. Major changes in the occurrence of the cells of different shape with increased donor age were not apparent, although the abundance of spindle-shaped cells decreased slightly with donor age. The large pleomorphic and sail-shaped cells exhibited similar UDS which was consistently greater than that of the spindle-shaped cells. No major changes in UDS were observed for either type of cell with increased donor age.