The sickle-unsickle cycle: a cause of cell fragmentation leading to permanently deformed cells.

We are reporting in vitro observations of sickle-unsickle transformation of freely suspended single cells (HbSS) induced by oxygenation-deoxygenation. The events were recorded by cinematography (phase optics, 16 mm cinematography). In addition, cells were fixed after progressive increments of oxygenation for subsequent scanning-beam electron microscopy. These studies seem to warrant the following conclusions regarding HbSS erythrocytes: (1) There is variability in the propensity to sickling of cells seemingly subjected to the same environment. (2) Repetitive sickling of a single cell does not result in identical sickle deformities. (3) Disk to sickle to disk transformation may occur without apparent membrane loss or distortion or may be accompanied by the shedding of microspherules or by the loss of microspherules and permanent cell deformation. (4) Red cell “flicker” normally seen by phasecontrast cinemicrophotography disappears early in the sickling process and recurs during unsickling. (5) Sickling and unsickling as visually detected required 10-15 sec.