Embryonic development, telomerase activity, and gene expression. (A) Development rate of cloned embryos of BFs, BBFs, and BTBFs. Reconstructed embryos' fusion, cleavage, and blastocyst formation rates were estimated one hour after electric fusion, on day 2, and on day 7, respectively. (B) Among the blastocysts in each group, bastocyst formation ratio was differently observed on Day 7 and Day 8. (C) The cell number of the blastocysts in each group was counted after differential staining, and the ICM/TE ratio was calculated. (D) Telomerase activities were measured in control cell lines (passage 5 (BF5), passage 20 (BF20), BBF lines (passage 20 (BBF20), passage 40 (BBF40)), BBBF lines (passage 20 (BTBF20), passage 40 (BTBF 60)). In the BTBF60, telomerase activity was detected in the highest level. (E) p53 gene expression by quantitative RT-PCR was measured in various cell passages of BFs, BBFs, and BTBFs. (BFs: Primary cultured bovine fibroblasts, BBFs: Bmi-1-introduced bovine fibroblasts, BTBFs, Bmi-1+hTert-introduced bovine fibroblasts).