Relationship between CEC apoptosis and plasma VEGF. Individual data points are shown for all normal (solid symbols, n = 8) and sickle (open symbols, n = 16) donors in whom we simultaneously measured plasma VEGF (in picograms per milliliter) and CEC apoptosis (in percentage of CEC positive by TUNEL and morphology). Brackets show the mean ± SD for all samples tested in the course of these studies for either apoptosis (n = 13 normal and 22 sickle) or VEGF level (n = 15 normal and 21 sickle).