Model approach to the analysis of effects of modulated electromagnetic radiation of animal cells

摘要

Frequency-dependent modifications of intracellular free calcium concentration ([Ca~(2+)]_i) in neutrophils exposured to modulated extremely high frequency electromagnetic radiation were analysed using a special mathematical model for [Ca~(2+)]_i oscillations. The model took into account the activation of Ca~(2+) influx into the cell by cytosolic Ca~(2+)-induced Ca~(2+) release from intracellular stores. The calcium channels of plasma membrane were chosen as a target for the influence of harmonic signal and additive noise in the model. the model simulation showed that in response to modulating signal, the rise in [Ca~(2+)]_i has frequency dependence and phase dependence in relation to the moment of chemical stimulation. The phase-frequency dependence of the effect was observed at a certain sequence of delivery of chemical stimulus and modulating signal to the cell. At intensities of modulating signals exceeding the threshold, a rise in [Ca~(2+)]_i, reaching a level of more than 50% of the initial level, was observed at a frequency of about 1 Hz and in the phase range of 0.3-2.5 radians. The effect was found only at high intensities of chemical stimulus. The additive noise introduced into the system qualitatively and quantitatively the phase-frequency characteristics of the cell response to the modulating signal. An increase in noise intensity resulted in a displacement of the average frequency of the band of rise in [Ca~(2+)]_i and then the emergence of a set of bands with a greater Q-factors. The analysis of dynamics of the nonlinear system in terms of the stability theory showed that, as the intensity of chemical stimulus increase,the system transits by means of a series of bifurcations from regular to chaotic, and then to oscillations, induced by a modulating harmonic signal. The boundary of the transition of oscillations from chaotic to induced ones corresponds to a specific threshold of the intensity of chemical stimulus for the significant rise in [Ca~(2+)]_i in response to the modulating signal. The results of the model analysis are in good correspondence with the experimental data obtained earlier, namely, with the effects of modulated extremely high-frequency electromagnetic rediation on neutrophils, which were observed only in the presence of Ca~(2+) in extracellular and at high concentrations of calcium ionophore A23187. Thus as the characteristic frequency of the quasiperiodic process of calcium signalling in the cell coincides with the frequency of external field, a narrow-band rise in [Ca~(2+)]_i is observed, which can result in a modification of the functional activity of the cell.