Membrane oscillator

In a recent review, it was pointed out that membrane oscillations can be produced by stretch, ischemia, hypoxia, cooling, drugs (catecholamines, digitalis, Ca +, Ba +, aconitine, veratrine), elevated PCo2> alterations in the electrolyte content of superfusion solutions, and spontaneously... 

Chay, T.R. J. Keizer. 1983. Minimal model for membrane oscillations in the pancreatic p-cell. Biophys. J. 42 181-90. 

Naparstek, A., D. Thomas S.R. Caplan. 1973. An experimental enzyme-membrane oscillator. Biochim. Biophys. Acta 323 643-6. 

Finally, in this section, possible frequencies for the excitation of coherent vibrations should be considered. Originally special reference was made to membrane oscillations as their high polarization will then yield coherent electric oscillations (cf. Ref. 7, with earlier literature). Since the thickness of a membrane is about 10" cm and its elastic constant is equivalent to a velocity of sound of about lO cm/s, a frequency of the order of 10 Hz was expected, corresponding to electromagnetic waves in the millimeter region. When based on proteins or DNA, however, both higher and lower frequencies may be expected. 

T. Hill and Y. Chen, Cooperative Effects in Models of Steady-State Transport Across Membranes Oscillating Phase Transition, Proc. Natl Acad. Scl USA 66(1), 189-196 (1970). 

A periodic and chaotic membrane oscillations have been observed in case of membrane doped by DOPH [19, 20]. After 30 min, a thick opaque di-oleyl phosphate (DOPH/oleyl alcohol/water (D/OAV) emulsion appears on the low-pressure surface of the membrane. The growth of this gel-like layer triggers a dramatic rise in the electrical resistance of the membrane and consequently oscillation in membrane potential. Chaotic behaviour appears as a part of periodic-chaotic sequence, also quite commonly associated with chaos. However fair amount of noise appears during membrane oscillations (Fig. 11.5) creating doubt regarding the existence of deterministic chaos. It has been shown that aperiodic behaviour in the system by way of a period-doubling sequence of bifurcation [19]. 

In the former case, we had considered electro-osmotic-driven oscillations at fixed value of current while AP was allowed to vary, on account of which membrane resistance could vary. An interesting case of electro-kinetic oscillations also occurs when AP is fixed, and the resistance varies due to progressive thickness of the emulsion on the membrane surface and the oscillations occur around the steady state corresponding to / = 0. Such electric potential oscillations, in a number of cases using DOPH-doped membranes have been reported [16, 19]. Chaotic oscillations in membrane oscillator have been reported and analysed from the angle of non-linear dynamics. 

Biological and physiological systems are typical complex systems, which provide examples of aperiodicity and chaos [1-7]. Aperiodic cardiac oscillations are reflected in ECG for different cases of arrhythmia Fig. (12.1). Similarly, chaotic, aperiodic and noisy oscillations are observed in EEC in specific cases as shown in Fig. (12.2). Closely allied with chemical oscillations are membrane oscillations which have considerable relevance in physiological processes including neurological and cardiac disorders in the context of detection and control. 

Then we investigated whether the water-oxidizing enzyme of the lyophilized PS II membranes is modified by lyophllization or not. The lyophilized PS II membranes on the paper disk were preilluminated by 10 flashes in Hepes buffer and incubated in the dark for 5 min at 25 "C. After the preillumination the oxygen evolution of the lyophilized membranes oscillated as the control PS II membranes did (Fig. 1). Moreover, the miss-hit (a, 0.16) and double-hit (yS, 0.11) probabilities and Si/(l +Sj ), 0.73, for the oxygen evolution pattern of the lyophilized and preilluminated PS II... 

The initial motivation for studying membrane oscillators was to understand biological processes [6-8]. Model synthetic systems have been constmcted that are simpler than the biological systems they were intended to mimic, and the goal has been to isolate key principles using pared down designs. As often occurs with model systems, however, synthetic membrane oscillators exhibit their own peculiar behaviors, leading to new lines of study. 

For some years, we have entertained the possibility that autonomous membrane oscillations can be used to drive rhythmic release of drugs and hormones in an... 

The teorell membrane oscillator as a mechano-electric transducer. J. Memh. Bid., 11, 197-216. 

Neurons stimulated by sinusoidal currents exhibit a synchronized response to the driving cycle, consisting of a train of repetitive action potentials as the bursting cells which rhythmically show self-sustained membrane oscillations accompanied by burst of repetitive impulses. The typical pattern of frequency change in response to a sinusoidal stimulus is graphically illustrated in Fig. 4. 

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