Nitella fluctuation and instability in the membrane potential near threshold
Biophysical Journal
|July 1, 1980
Summary
Nitella internodal cells exhibit critical oscillations and repetitive firing, suggesting a hard-mode instability. This phase transition in an open system is linked to metabolic feedback and electrogenic pumps.
Area of Science:
- Cellular electrophysiology
- Non-equilibrium thermodynamics
- Plant cell biophysics
Background:
- Investigating phase transitions in open systems far from thermal equilibrium is crucial for understanding biological complexity.
- Nitella internodal cells serve as a model system for studying membrane potential dynamics and excitability.
Purpose of the Study:
- To examine the phase transition in Nitella internodal cells as an example of non-equilibrium systems.
- To characterize the membrane potential fluctuations and their spectral properties during excitation.
Main Methods:
- Analysis of membrane potential fluctuations using power density spectrum.
- Observation of critical oscillations and repetitive firing under varying current stimuli.
- Measurement of membrane impedance.
Main Results:
- A bulge in the power spectrum (<1 Hz) at resting state shifted to a peak (~0.03 Hz) at depolarized states near threshold.
- Critical oscillations and repetitive firing were observed, with frequencies aligning with the spectral peak.
- No corresponding peak in membrane impedance was found in the frequency range of voltage spectral peaking.
Conclusions:
- The observed phenomena suggest a hard-mode instability in Nitella internodal cells.
- The spectral peak is likely attributed to an electrogenic pump modulated by metabolic feedback from photosynthesis.
- This study provides insights into non-equilibrium phase transitions in biological systems.
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