Membrane potential fluctuations of human T-lymphocytes have fractal characteristics of fractional brownian motion

Abstract

The voltage across the cell membrane of human T-lymphocyte cell lines was recorded by the whole cell patch clamp technique. We studied how this voltage fluctuated in time and found that these fluctuations have fractal characteristics. We used the Hurst rescaled range analysis and the power spectrum of the increments of the voltage (sampled at 0.01-sec intervals) to characterize the time correlations in these voltage fluctuations. Although there was great variability in the shape of these fluctuations from different cells, they all could be represented by the same fractal form. This form displayed two different regimes. At short lags, the Hurst exponent H = 0.76 +/- 0.05 (SD) and, at long lags, H = 0.26 +/- 0.04 (SD). This finding indicated that, over short time intervals, the correlations were persistent (H > 0.5), that is, increases in the membrane voltage were more likely to be followed by additional increases. However, over long time intervals, the correlations were antipersistent (H < 0.5), that is, increases in the membrane voltage were more likely to be followed by voltage decreases. Within each time regime, the increments in the fluctuations had characteristics that were consistent with those of fractional Gaussian noise (fGn), and the membrane voltage as a function of time had characteristics that were consistent with those of fractional Brownian motion (fBm).

Hurst Analysis Applied to the Study of Single Calcium-activated Potassium Channel Kinetics

“…The rescaled range analysis was also used by Churilla et al (1996) to study the #uctuations of the membrane potential of human T-lymphocytes. They showed that the phenomenon has the fractal characteristics of a fractional Brownian motion.…”

“…In cellular biology, the rescaled range analysis has been used to analyse records in time produced by the mechanical motions of cells growing in tissue culture (Giaever & Keese, 1989) and one of us applied the R/S analysis to the study of patch clamp records of the membrane potential #uctuations of human T-lymphocytes (Churilla et al, 1996). Here the R/S analysis is applied to study calcium-activated potassium channels of Leydig cells.…”

Comparison of spectral and entropic measures for surface electromyography time series: A pilot study

“…This crossover implies a transition from an absence of correlations in the signal to antipersistence behavior. Similar transitions from short-to long-time behavior have been observed for other physiological time series [16][17]. Because the mean square displacement is related to the entropy S of the signal, S ~ ln Δ (where ln denotes the natural logarithm), the plateau value can be used to characterize the sEMG signal [15].…”

Power-Law Behavior of Beat-Rate Variability in Monolayer Cultures of Neonatal Rat Ventricular Myocytes

“…26,27 Moreover, electrophysiological studies showed the presence of fractal characteristics in the oscillations of the membrane potential. 28 Also, it was shown that, while isolated cardiac cells beat stochastically, fractal patterns of activity establish when a large number of cells are electrically coupled and synchronize. 29 Finally, it is feasible that other processes, such as biochemical reactions, protein synthesis, or gene expression, contribute to the observed variations in beat rate.…”