Resumen de Dynamics of the membrane potential: studies of the membrane potential of jurkat cells using wavelet and wavelet bispectral analysis
Fluctuations are fundamental for living organisms. They arguably result from interactions with the complex, and unpredictable environment, and can often be manifested as temporal variability. The cell must continually resist the external variations in the osmotic pressure by continuous adjustments in the intracellular concentrations. This happens through a highly specialised network of membrane transporters, and is manifested in the dynamics of the membrane potential. The aim of the work presented here is to provide understanding and insight into the dynamics of the free-running membrane potential in non-excitable cells, based on experimental data. In order to achieve this, first the quantitative comparisons of the average values of the membrane potential and their standard deviations recorded in various conditions are made. The analysis is further extended through the use of the wavelet transform to investigate the time and frequency components of the signal. This work is the first to report an intermittent oscillations in the membrane potential around frequency of 8 mHz but also around frequencies of 0.03, 0.05 or 0.09 Hz. To further understand this dynamics from univariate time series, time-reversibility is investigated and a novel wavelet-bispectral density analysis is developed. The wavelet-bispectral density allows for a formal quantitative, not merely qualitative interpretation of the results of wavelet-bispectral analysis. Finally, the newly developed auto-wavelet-bispectral analysis is applied to the recordings of the membrane potential. These indicate possible nonlinear couplings between different oscillatory modes in the cellular membrane potential.
