Emergence and characterization of nonadherent cells.

(A) Time-lapse images of cells in a special incubation chamber were acquired by a digital camera and analyzed by Analysisdocu software (Soft Imaging Systems, Leidenfelden, Germany). At hour 0 of culture, the cell morphology was characterized by pseudopodia and buds. After 4 hours, the cells began to retract their pseudopodia and become more spherical. Cells that were destined to divide then began to enlarge. After 14 hours and 15 minutes of culture, a cell division was observed (arrow). (B) Raster electron micrograph (original magnification, × 2000) shows that NA cells are spherical and lack pseudopodia. (C) A representative flow cytometric analysis of surface CD34 and CD133 expression on NA cells (n = 6) derived by stimulation of 6-week-old adherent cells with SCF for 72 hours. Cells were incubated with an isotype-matched control mouse antibody (i). No NA cells expressed CD34 (ii), but a subset expressed CD133 (iii).