QUANTITATIVE-EVALUATION OF ERYTHROCYTE VISCOELASTIC PROPERTIES FROM DIFFRACTOMETRIC DATA - APPLICATIONS TO HEREDITARY SPHEROCYTOSIS AND HEMOGLOBINOPATHIES

A numerical process is proposed to evaluate viscoelastic properties of mammalian erythrocyte membranes from diffractometric data obtained wi th the Erythrodeformeter (1). The numerical process is based on an ide alized model of the cell response to the applied fluid shear stress as suming that the tank treading motion start lags the start of the shear stress field by several milliseconds. Photometric readings performed on the elliptical diffraction pattern generated by the shear elongated cells and photometrically recorded curves of creep and recovery of ce lls, are used in the calculations of theological properties, averaged over several millions of cells. Results obtained from different hemato logical disorders are presented and compared with those obtained from healthy donors, showing significative differences that are in accordan ce with the type and the state of the corresponding disease. Computed values representative of the elastic modulus of normal cells agree ver y well with those ones determined with the micropipette technique (2) while retardation time, and consequently values of surface viscosity, obtained by the diffractometric technique are somewhat smaller than th e ones obtained by the shape recovery in micropipettes.