The development of avian red cell shape

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Abstract
Immature erythrocytes of pigeons and chickens change from a spherical to a flat form following the final mitotic division during development. In vitro studies provide evidence that initial changes in shape are influenced by conditions that affect availability of oxygen. Transformation to a flat form occurred most rapidly at 37°C, a temperature that results in deoxygenation of hemoglobin in erythrocytes of the bone marrow. The maximum rate of transformation occurred at pH 6.5, a pH which favors deoxygenated hemoglobin. Oxygen inhibited the transformation in shape at 37 °C and resulted in a reversion of shape, from flat to spherical. Flattening and deoxygenation of hemoglobin are highly correlated. Precursor erythrocytes in plasma clot culture were observed microscopically. The cell stages identified in sequence were: (1) the “n‐2” dark cells, apparently lacking hemoglobin. These cells divided to form “n‐1” cells which synthesized hemoglobin as they matured. The “n‐1” cells divided, forming spherical daughter “n” cells which flattened within 60 minutes after mitosis.