Document Detail

Circadian oscillators, cell cycles, and singularities: light perturbations of the free-running rhythm of cell division in Euglena.
MedLine Citation:
PMID:  3837018     Owner:  NLM     Status:  MEDLINE    
The free-running circadian rhythm of cell division in the algal flagellate, Euglena gracilis (Z) was perturbed by 3-h light signals of varying intensities imposed at different circadian times (CT). Light pulses within the range of 700 to 7,500 lux were found to yield the same 'strong' (Type 0) phase response curve (PRC) comprising both advance and delay phase shifts as great as 15 h. Dark signals generated a PRC of reduced amplitude with very little, if any, phase advance being observed. Light perturbations of lower intensity, however, elicited quite different responses if applied at a quite specific circadian time: A 40- to 400-lux pulse given at approximately CT 0 (late subjective night) induced total arrhythmicity, and the culture reverted to asynchronous, exponential growth. Different degrees of arrhythmicity were induced by the same low-intensity perturbations (I*) given slightly before or after this sensitive phase point (T*), but if imposed at other circadian times, they generated normal type 0 phase resetting. The demonstration of the existence of this critical pulse (T*, I*) provides further evidence that the cell division cycle of Euglena (and presumably other microorganisms) is regulated by a circadian oscillator and, in particular, by one having limit cycle dynamics.
J R Malinowski; D L Laval-Martin; L N Edmunds
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology     Volume:  155     ISSN:  0174-1578     ISO Abbreviation:  J. Comp. Physiol. B, Biochem. Syst. Environ. Physiol.     Publication Date:  1985  
Date Detail:
Created Date:  1986-09-16     Completed Date:  1986-09-16     Revised Date:  2009-06-08    
Medline Journal Info:
Nlm Unique ID:  8413200     Medline TA:  J Comp Physiol B     Country:  GERMANY, WEST    
Other Details:
Languages:  eng     Pagination:  257-67     Citation Subset:  IM    
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MeSH Terms
Biophysical Phenomena
Cell Cycle
Cell Division*
Circadian Rhythm*
Euglena / cytology*
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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