Fig. 2. (A) PMA induced a time-dependent remodelling of actin in HUVECs. Cells were treated with PMA for over a 6-hour period and stained with rhodamine-phalloidin to visualise F-actin. Upon addition of PMA, stress fibres rapidly disappeared and were found greatly reduced at 30 minutes when F-actin dots became detectable. Podosomes remained visible up to 3 hours and then progressively disappeared. At 6 hours, podosomes were not detectable and stress fibres had returned. Bar, 10 µm. (B) PMA-induced individual podosomes and rosettes. HUVECs were treated with PMA for 1 hour. F-actin was labelled with rhodamine-phalloidin. High-magnification images show the presence of individual podosomes and clusters of podosomes defined as rosettes. Bar, 10 µm. (C) Quantitation of the experiment described in A. Cells showing either individual podosomes or rosettes were counted after treatment with PMA; data are presented as percentage of the total population. Error bars represent the mean ± s.d. of three independent experiments where approximately 200 cells per coverslip were counted.