Document Detail

Effect of changing the light/dark schedule, the time of onset of the light or dark period, or the daylength, on rhythms of epidermal cell proliferation.
MedLine Citation:
PMID:  3266106     Owner:  NLM     Status:  MEDLINE    
Rhythms of labeling and mitotic indices were studied in the hindlimb epidermis of the anuran tadpole Rana pipiens under different light/dark (LD) cycles and daylengths in order to examine the role of the various parameters of the lighting regimen in setting the periods of the rhythms and the timing of the cell proliferation peaks. Altering the time of, or inverting, the 12 h light period on a 24 h day resulted in phase shifting of basically bimodal circadian rhythms with peaks in the light and dark. Thus the cell proliferation rhythms were entrained to the LD cycle. These rhythms also entrained to noncircadian schedules since they lengthened on a 15L:15D cycle and shortened on a 9L:9D cycle, although the bimodal characteristic of a peak in the light and a peak in the dark remained. Studies of 18L:6D and 6L:18D cycles in which either the time of onset of light or dark was changed relative to the 12L:12D control indicated that the onset of dark may regulate the timing of the labeling index peaks while the onset of light may determine the time of occurrence of mitotic index peaks. Control of the timing of labeling and mitotic index peaks by different parameters of the LD cycle suggests a mechanism for cell cycle regulation by the environmental lighting schedule. Analysis of the rhythms on all the cycles studied suggested that labeling index rhythms equal the length of, or twice the length of, the dark period. Mitotic index rhythms equal the daylength or a multiple of the length of the dark period.
M L Wright; Y M Myers; S T Karpells; C A Skibel; M B Clark; M L Fieldstad; I J Driscoll
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Chronobiology international     Volume:  5     ISSN:  0742-0528     ISO Abbreviation:  Chronobiol. Int.     Publication Date:  1988  
Date Detail:
Created Date:  1989-04-28     Completed Date:  1989-04-28     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8501362     Medline TA:  Chronobiol Int     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  317-30     Citation Subset:  IM    
Biology Department, College of Our Lady of the Elms, Chicopee, MA 01013.
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MeSH Terms
Cell Cycle
Cell Division
Circadian Rhythm*
Epidermis / cytology*
Mitotic Index
Rana pipiens

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

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