Determination of time-dependent shape changes in red blood cells

A kinetic method for detecting changes in red blood cell shape with time resolution on the order of seconds is described. The definition of shape index (SI) and the experimental conditions under which the measurements should be conducted are given, and the relationship between SI and morphological index, which is often used to quantitatively assess red blood cell morphology, is established. Further, we show that the method can be used to assess shape changes under a variety of experimental conditions known to cause major perturbations in the morphology of red blood cells (such as addition of lysolecithin or chlorpromazine) and to detect changes in shape during chemical fixation for observation with microscopy. We report here that the ability of glutaraldehyde to fix red blood cells without additional alteration in shape strongly depends on the morphology that is being fixed and the initial state of the cells.