BMPC-rich elutriation fraction from healthy human blood cultured in DMEM-20% FCS. Cells were fixed, stained with anti-BMPR 1A antibody (see Methods), and analyzed on days 3, 5, 8, and 11. BMPCs were determined by morphology (fibroblast-like [hatched bars] or big cells [filled bars]) and immunoperoxidase staining. Results are presented as the means of total number of cells in six individual images. ×400. Computer image analysis (AnalySIS).