by Editor T. DiPerri) The investigation of erythrocyte deformability changes during cell ageing might give one insight on circulatory behaviour of young and old red blood cells. Erythrocytes of healthy subjects of both sexes had been separatel) into 3 fractions of increasing age on a Percoll discontinous density gradient and their different age has been tested by pyruvate kinase (PK) and glucose-6-phosphate dehydrogenase (G6PD) activities. Each fraction, free of leucocytes, suspended to 10%

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... atocrit, was filtered through Nuclepore filters 5 micron diameter; erythrocytes lying on filters were observed by Scanning Electron microscopy. Erythrocyte deformability has shown small decrease from middle aged cells to old and youngest ones.