Cellular deformability: a possible determinant of the normal release of maturing erythrocytes from the bone marrow.

membrane which separates marrow hematopoietic cords from sinuses. Shape and nuclear rigidity are the most important determinants of rigidity in these immature cells. The marrow reticulocyte, with its distinctive clover-leaf configuralion, still manifests significant intrinsic rigidity of its membrane and possibly underlying cytoplasm, which may be important to its normal retention in the bone marrow. However, further maturation is accompanied by a progressive decrease in membrane stiffness and, hence, resistance to traversing the micropipette. These results are interpreted to suggest that cellular deformability may be an important determinant of normal release of maturing erythrocytes from the bone marrow.