Transient dielectro-deformations of erythrocyte governed by time variation of cell ionic state.

The possibility is shown to monitor the transient ionic state and volume of erythrocyte suspended in low ionic strength solution (LISS) by registration of the dielectro-deformation (DD) of a cell. The adequate theoretical basis is developed. Possible registration modes are considered analytically and numerically using the theory of dielectro-deformation of erythrocytes developed previously.

Stationary deformations of erythrocytes by high-frequency electric field.

The theory of erythrocyte deformation by high-frequency (HF) electric field, based on ellipsoidal approximation for cell shape, is developed. Various possible deformational regimes of cell elongation by the field are analyzed, depending on the relation between the bending and the shear deformations of cell membrane and the magnitudes of corresponding mechanical stresses arising. The role of mechanical, electrical, and geometrical parameters of erythrocyte in formation of various parts of deformational curves (cell length-field strength) is elucidated, including the initial part and the geometrical saturation region. The measurements of the stationary elongation curves of erythrocytes by Krueger and Thom [Biophys. J. 73 (1997) 2653] are analyzed quantitatively. The shape of the measured curves is described exactly by the theory for the whole range of field strengths and temperatures used. The temperature-dependent values of erythrocyte volume and cytoplasmic conductivity are obtained from this description in the range (- 15-25 degrees C).

Spontaneous and forced oscillations of cell membrane of normal human erythrocytes: absence of resonance frequencies in a range of 0.03-500 Hz.

The spectra of natural oscillations of human erythrocyte cell membranes were studied experimentally and theoretically. The measurements were carried out at room temperature for both single normal cells and erythrocyte rouleaux in a range of 0.03-500 Hz. The spectra were measured at a resolution better than 1% using two techniques: registration of spontaneous membrane oscillations induced by thermal agitation in the surrounding medium and registration of the amplitude-frequency characteristics of the forced oscillations of erythrocyte elongation induced by a high-frequency electric field with the amplitude harmonic modulation. The spectra measured by both techniques had no resonance frequencies and decreased monotonically with the frequency increase. These results are confirmed by the theory developed for the extracellular excitation mechanisms of membrane oscillations. The spectra of active oscillatory biomechanical processes were measured for comparison. These processes are ciliary beating of human bronchial epithelium and ciliary beating and artificial periodic contractions of the cytoplasm of the ciliate Spirostomum ambiguum. The quality of the resonance lines of the order of 10-20 registered may serve as estimates for the line width in search of the resonance oscillations in erythrocytes induced by active cell processes.