Defining myoblast population kinetics by live cell imaging. Individual EGFP-expressing myoblasts were studied as in Figure 2 using manual counting. Differentiation medium (DM) was added ± IGF-I (R3-IGF-I [2 nM]), as indicated. (A) Effect of IGF-I on total cell number. (B) Effect of IGF-I on the frequency of cell division (DM 234 divisions; IGF-I 344 divisions). (C) Effect of IGF-I on myoblast death (DM 208 deaths; IGF-I 154 deaths). For A to C, blue depicts control cells and red, myoblasts incubated with IGF-I. For B and C, the number of cells exhibiting a specific trait at a given time is plotted on the y-axis.