ISSN:
1615-6102
Schlagwort(e):
Anti-phase locking
;
Calcium diffusion
;
Shuttle streaming
;
Physarum polycephalum
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
Notizen:
Summary Shuttle streaming in an isolated strand ofPhysarum plasmodium requires the isometric tensions at each end to oscillate with a constant phase difference, preferably 180°. The stability of in-phase (IP)- and anti-phase (AP)-locked states of an oscillating strand is studied in terms of two diffusion-coupled oscillators, whose frequencies are determined by their total calcium levels. Anti-phase locking is generated by oscillatory frequency modulations, which occur when the difference in total calcium levels oscillates through zero. The anti-phase-locked state is generated when diffusive coupling is small, the initial difference in free calcium levels exceeds a minimum value, and the initial difference in total calcium levels is small. It is shown that these conditions are maintained. The stabilities of phase-locked states can be exchanged following an imposed transfer of free calcium between the ends. The AP→IP transition occurs for all sufficiently large transfers, whereas IP→AP conversion occurs only in a narrow range of amount transferred when the oscillator receiving calcium is near minimum value for its free calcium level. The in-phase-locked state is always stable when diffusive coupling is large: this occurs for small volumes of cytoplasm and creates the required internal phase coherence. The relationship of these results to recent experiments onPhysarum is discussed.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01378991
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