High-frequency electric fields can be used to induce deformation of red blood cells. In the temperature domain T = 0 degrees to -15 degrees C (supercooled suspension) and for 25 degrees C this paper examines for human erythrocytes (discocytes, young cell population suspended in a low ionic strength solution with conductivity sigma(25 degrees) = 154 microS/cm) in a sinusoidal electric field (nu = 1 MHz, E0 = 0-18 kV/cm) the following properties and effects as a function of field strength and temperature: 1) viscoelastic response, 2) (shear) deformation (steady-state value obtained from the viscoelastic response time), 3) stability (by experimentally observed breakdown of cell polarization and hemolysis), 4) electrical membrane breakdown and field-induced hemolysis (theoretical calculations for ellipsoidal particles), and 5) mechanical hemolysis. The items 2-4 were also examined for the frequency nu = 100 kHz and for a nonionic solution of very low conductivity (sigma(25 degrees) = 10 microS/cm) to support our interpretations of the results for 1 MHz. Below 0 degrees C with decreasing temperature the viscoelastic response time tau(res)(T) for the cells to reach steady-state deformation values d(infinity,E) increases and the deformation d(infinity,E)(T) decreases strongly. Both effects are especially high for low field strengths. The longest response time of approximately 30 s was obtained for -15 degrees C and small deformations. For 1 MHz the cells can be highly elongated up to 2.3 times their initial diameter a0 for 25 degrees and 0 degrees C, 2.1a0 for -10 degrees C and still 1.95a0 for -15 degrees C. For T > or = 0 degrees C the deformation is limited by hemolysis of the cells, which sets in for E0(lysis)(25 degrees) approximately 8 kV/cm and E0(lysis)(0 degrees) approximately 14 kV/cm. These values are approximately three times higher than the corresponding calculated critical field strengths for electrically induced pore formation. Nevertheless, the observed depolarization and hemolysis of the cells is provoked by electrical membrane breakdown rather than by mechanical forces due to the high deformation. For the nonionic solution, where no electrical breakdown is expected in the whole range for E0, the cells can indeed be deformed to even higher values with a low hemolytic rate. Below 0 degrees C we observe no hemolysis at all, not even for the frequency 100 kHz, where the cells hemolyze at 25 degrees C for the much lower field strength E0(lysis) approximately 2.5 kV/cm. Obviously, pore formation and growth are weak for subzero temperatures.

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The final four lines on page 970 were repeated on page 971. Also, the final five lines on page 973 were repeated on page 974. The following text was missing at the beginning of page 973. 5. Measuring uncertainties and comparison with known data The accuracy of the method depends on the following uncertainties.

To evaluate temperature-dependent stretching experiments of biological cells down to sub-zero temperatures in a high-frequency electric field, knowledge of the electrical parameters of the suspension is necessary. A measuring system was developed to determine the relative permittivity ε r (f , T ) and the ionic conductivity γ (f , T ) of supercooled aqueous solutions and suspensions in the frequency range 0.1-2 MHz. A parallel-plate capacitor was used in connection with an impedance analyser and a cryostat. The errors caused by the cables needed between analyser and cooled capacitor were minimized. Field homogenization within the measuring space is realized by correcting the reference potential at the guard ring. The starting capacitance at each temperature was reproduced by testing the 0 • C value after re-assembling the capacitor. Damaging of the capacitor by ice formation is prevented. For testing, a comparison was made with literature data and first measurements of supercooled aqueous solutions.