RESUMO
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.
Assuntos
Relógios Biológicos/fisiologia , Membrana Celular/fisiologia , Potenciais da Membrana/fisiologia , Modelos Biológicos , Bombas de Próton/fisiologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/fisiologia , Relógios Biológicos/efeitos da radiação , Membrana Celular/efeitos da radiação , Simulação por Computador , Relação Dose-Resposta à Radiação , Campos Eletromagnéticos , Ativação do Canal Iônico/fisiologia , Ativação do Canal Iônico/efeitos da radiação , Potenciais da Membrana/efeitos da radiação , Proteínas de Membrana/metabolismo , Bombas de Próton/efeitos da radiação , Doses de Radiação , Saccharomyces cerevisiae/efeitos da radiaçãoRESUMO
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.
