RESUMEN
We report on harmonic generation by budding yeast cells (Saccharomyces cerevisiae, 10(8) cells/ml) in response to sinusoidal electric fields with amplitudes ranging from zero to 5 V/cm in the frequency range 10-300 Hz. The cell-generated harmonics are found to exhibit strong amplitude and frequency dependence. Sodium metavanadate, an inhibitor of the proton pump known as H+-ATPase, and glucose, a substrate of H+-ATPase, are found to increase harmonic production at low amplitudes while reducing it at large amplitudes. This P-type proton pump can be driven by an oscillatory transmembrane potential, and its nonlinear response is believed to be largely responsible for harmonic production at low frequencies in yeast cells. We find that the observed harmonics show dramatic changes with time and in their field and frequency dependence after perturbing the system by adding an inhibitor, substrate, or membrane depolarizer to the cell suspension.
Asunto(s)
Relojes Biológicos/fisiología , Membrana Celular/fisiología , Potenciales de la Membrana/fisiología , Modelos Biológicos , Bombas de Protones/fisiología , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/fisiología , Relojes Biológicos/efectos de la radiación , Membrana Celular/efectos de la radiación , Simulación por Computador , Relación Dosis-Respuesta en la Radiación , Campos Electromagnéticos , Activación del Canal Iónico/fisiología , Activación del Canal Iónico/efectos de la radiación , Potenciales de la Membrana/efectos de la radiación , Proteínas de la Membrana/metabolismo , Bombas de Protones/efectos de la radiación , Dosis de Radiación , Saccharomyces cerevisiae/efectos de la radiaciónRESUMEN
We report on harmonic generation by budding yeast cells in response to a sinusoidal electric field, which is seen to be minimal when the field amplitude is less than a threshold value. Surprisingly, sodium metavanadate, an inhibitor of P-type ATPases reportedly responsible for nonlinear response in yeast, reduces the threshold field amplitude, increasing harmonic generation at low amplitudes while reducing it at large amplitudes, whereas the addition of glucose dramatically increases the production of even harmonics. Finally, a simple model is proposed to interpret the observed behavior.
Asunto(s)
Adenosina Trifosfatasas/fisiología , Adenosina Trifosfatasas/efectos de la radiación , Membrana Celular/fisiología , Membrana Celular/efectos de la radiación , Activación del Canal Iónico/fisiología , Activación del Canal Iónico/efectos de la radiación , Modelos Biológicos , Simulación por Computador , Relación Dosis-Respuesta en la Radiación , Campos Electromagnéticos , Conformación Proteica/efectos de la radiación , ATPasas de Translocación de Protón/fisiología , ATPasas de Translocación de Protón/efectos de la radiación , Dosis de Radiación , Saccharomyces cerevisiae/fisiología , Saccharomyces cerevisiae/efectos de la radiaciónRESUMEN
Reactions between metals and chloride solutions have been shown to exhibit magnetic field fluctuations over a wide range of size and time scales. Power law behavior observed in these reactions is consistent with models said to exhibit self-organized criticality. Voltage fluctuations observed during the dissolution of magnesium and aluminum in copper chloride solution are qualitatively similar to the recorded magnetic signals. In this paper, distributions of voltage and magnetic peak sizes, noise spectra, and return times are compared for both reactions studied.
RESUMEN
Sudden bursts of chemical activity, displaying avalanche-like behavior, have been observed in reactions between metals and liquid electrolytes by measuring the time-dependent chemomagnetic fields with a high-T(c) SQUID. The observed intermittent chemomagnetic field pulses exhibit power-law behavior in the distributions of peak sizes, noise spectra, and return-time distributions. Such power-law behavior provides evidence for self-organized criticality occurring in the form of "chemical avalanches" over a wide range of size and time scales.