Morphological changes in differential interference contrast microscopy of cultured nascent reticulocytes. Aliquots of cultured nascent reticulocytes were concentrated by centrifugation, and wet mount preparations in tissue culture medium were prepared at the times shown. Biconcave cells are shown as arrows in the 86-hour cells and as arrowheads in the 110-hour cells. RBC is a wet mount preparation of blood erythrocytes from a normal mouse. Magnification, × 390.