Lighting schedule shifts prolong survival of enucleated Acetabularia
Berger, S.; Schweiger, H.G.; Halberg, F.
Progress in Clinical and Biological Research 341b: 699-705
1990
ISSN/ISBN: 0361-7742 PMID: 2217361 Document Number: 3481
Much work has dealt with rhythms in unicells, including Acetabularia mediterranea and even bacteria. It seems likely that multiple mechanisms are involved in unicells, as in mammals. Acetabularia offers the opportunity to study the effect of schedule shifts of the lighting regimen upon unidentified mechanisms in an isolated cytoplasm, in the absence of the nucleus. At this level, a loss of vitality may (but must not) occur following enucleation, for reasons unknown to us. When it occurs, this loss of vitality can be counteracted to some extent, though not fully, by lighting regimen shifts. The data conclusively show that lighting regimen shifts need not be harmful, even at the level of an isolated cytoplasm, and suggest further that under certain conditions they can be beneficial. Various Drosophila mutants have also been tested for the effect of environmental cycles; as compared to all other mutants, an increased longevity, under all conditions examined, was reported for the fly which appeared to be 'arrhythmic'. The age at the first shift is not controlled. There are limitations to the work here reported, which was set up in a different context for the study of growth rather than mortality. The numbers of cells investigated sufficed for the former purpose, but allow only overall inferences with respect to mortality. Further work will have to clarify whether some shifts may be beneficial whereas others may be harmful. The reasons why vitality was lowered by enucleation in one study but not in another will have to be elucidated. The point remains, however, that changes in rhythms which almost certainly are responses to changes in lighting regimen can add to (rather than subtract from) vitality. This problem has attracted much earlier attention in various species since one of us (FH) started experimental work and found a detrimental effect in one of two groups but no deficit in another group subjected to shifts for a lifetime. Not only certain schedule shifts, but even exposure to continuous light, a condition which also leads to rhythm alterations, can prolong life in male hamsters with inherited heart disease. Any cytoplasmic mechanisms of this effect can be uniquely studied in further work along the lines here reported on the isolated cytoplasm of Acetabularia mediterranea.
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