Persisting circadian oscillations in enzyme activity in non-dividing cultures of Euglena.
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Acid Phosphatase↗
Biomedical subjects
F M Sulzman
Publications and source records attributed to F M Sulzman.
Cellular autonomy of the Gonyaulax circadian clock.
Because of the long term persistence of free-running circadian rhythms in populations of unicells, several investigators have considered, but not demonstrated, a possible role for intercellular interaction in maintaining synchrony between individual cells. The experiments described here were designed to test more critically the possibility that there is interaction between cells, including those possessing only small phase differences. None was detected; the bioluminescent glow of the mixed cultures matched the algebraic sum of the independent control cultures.
Animals↗
Are ultradian and circadian rhythms in renal potassium excretion related?
Spectral and band-pass analyses of renal potassium excretion time series demonstrated the presence of significant ultradian periodicities. These rhythms and their relationships to circadian rhythms were examined under varying conditions, with and without external (LD cycle) or internal (plasma cortisol) Zeitgebers. The results showed that ultradian rhythms appear to be independent endogenous oscillations. They seem related to circadian periodicities in that they demonstrated several characteristics of subharmonic synchronization in the entrained state, and underwent detuning and amplitude diminution with the removal of controlling Zeitgebers. Ultradian rhythms play a more prominent role in the absence of strong external or internal time cues. They may be important in the formation and stabilization of circadian timekeeping or may represent some dissociated state of elements in the circadian system.
Adrenalectomy↗