Figure 3.

Telomerase activity in 12-day-old embryos and fibroblast cultures established from the embryos. (A) The activity present in fibroblast cultures after two or four passages. Lanes 1 and 2 controls; lane 1, PCR reaction with TS and ACX primers but no input from the telomerase extension reaction; lane 2, buffer rather than extract was used in the telomerase extension reaction; lanes 3–7, tissue and cell cultures samples from embryo 1; lanes 8–12, tissue and cell cultures samples from embryo 2; lanes 13–17, over exposure of lanes 3–7. Lanes 3, 5, 8,10, 13, and 15, extracts were made directly from embryo tissue. Lanes 4, 6, 9, 11, 14, and 16, extracts were made from embryonic fibroblast cultures after two passages. Lanes 7, 12, and 17, extracts were made from embryonic fibroblasts after four passages. +, Pretreatment with RNase A; −, no RNase A treatment. (B) The activity present in embryo cells 4 hr after isolation. Lane 1, extract was made directly from embryo tissue. Lane 2, extract was made from the population of cells that had not adhered to the tissue culture dishes after a 4-hr incubation. Lane 3, extract was made from the population of cells that had attached to the tissue culture dish after 4 hr.