Experimental Modification of the Temporal Aspects of the Serum-Induced Cell Cycle in the Cultured Adult Rabbit Lens

Abstract

The adult rabbit lens in organ culture has been used as a model system for studies on the control of cell division in an organized tissue. Freshly isolated lenses, placed immediately in culture media containing serum (M-199-S) undergo a series of characteristic changes in macromolecular synthesis (RNA, protein, DNA) and ultrastructure which herald the onset of mitosis. In the present experiments lenses were preincubated 24 h in a non-stimulating medium which maintains the central epithelial cells in their normal non DNA synthesis proliferating state. They were then transferred to M-199-S. Preincubation for 24 h in the non-stimulating medium decreases the time required between the addition of serum and the initiation of and mitosis, and increases the degree of synchrony with which the cells enter DNA synthesis. It also shortens the time required for the serum-induced increase in RNA production and ribosome formation. Serum-induced ribosome formation in preincubated lenses is relatively intense (as compared with freshly-isolated lenses). The acceleration of serum effects on macromolecular synthesis and mitosis is discussed in terms of the effects of preincubation on the G-0-1 → G-1 transition