Fig. 2. Life cycle of MTs visualized in centrosome-containing CHO cytoplasts. (A) Time-lapse sequence shows selected panels from life histories of four MTs. (B) Two MTs (colored blue and red) were nucleated at the centrosome (at 3 seconds and 39 seconds, respectively) and persistently grew towards the cell margin. These MTs underwent transition to shortening only after they arrived at the cell margin (arrowheads: red MT, at 102 seconds; blue MT at 120 seconds). The length of the blue MT is greater than the red MT because it grew in a curved path and along the cell margin before beginning to shorten. (C) Two MTs (colored yellow and green) were initially tracked while near the cell margin. These MTs showed repeated episodes of growth and shortening near the membrane and the green MT eventually underwent a shortening excursion back to the centrosome. Numbers in the top-left corners indicate time in seconds. Bar, 5 µm. Life history plots constructed as indicated in Fig. 1 legend.