The effect of cell passage number and serum starvation on telomerase
activity. Telomerase activity was measured in protein extracts (0.5
μg) from adult fibroblast (AF) (passage 4) and FF (passage 1) cell
lines (A) and in protein extracts (0.25 μg) from
bovine ES-like cells (passage 8) and FF (passage 1) cell lines
(C), with the use of the TRAP assay. Heat-inactivated
(HI) control, positive 293 cell extract control (+), and negative lysis
buffer control (−), are displayed. (B–F) Densitometric
analyses of TRAP reaction products displaying the relative telomerase
activities between bovine cell samples. Telomerase activity was
measured in protein extracts (0.25 μg) from (E) bovine
ES cell-like cells and (F) FFs at early passage (EP)
(passages 8 and 1, respectively) and late passage (LP) (passages 34 and
24, respectively) and early-passage cells after increasing incubation
times under serum starvation (SS) conditions (24 h, 48 h, 5 days,
10 days). Asterisks (*) denote significant differences
(P < 0.05) between mean telomerase activities.