B Poljsak1, S Ribarič2, I Milisav3. 1. Laboratory of Oxidative Stress Research, Faculty of Health Sciences, University of Ljubljana, Zdravstvena pot 5, SI-1000 Ljubljana, Slovenia. 2. Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia. 3. Laboratory of Oxidative Stress Research, Faculty of Health Sciences, University of Ljubljana, Zdravstvena pot 5, SI-1000 Ljubljana, Slovenia; Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia. Electronic address: irina.milisav@mf.uni-lj.si.
Abstract
Yin and Yang concept emphasizes the reciprocal and interrelated nature; neither is sufficient, both are needed to sustain the overall balance of the living system. Changing the balance, by implementing deficiency or excess of one of them, upsets the equilibrium (homeostasis) of the whole system. PURPOSE: In this opinion article intermittent exposure is presented as the stimulus for development and evolutionary conservation of circadian rhythm, an endogenous, entrainable oscillation of approximately 24 h, to counteract/balance the cells' natural tendency to attenuate their response during long-term exposure to different endogenous substances. RESULTS: The concept of Yin and Yang duality is an allegory on which the avoidance of attenuation of the cells' responses hypothesis is presented as an explanation for the circadian rhythmicity, which is integrated in all human cells, with the exception of stem and cancer cells. CONCLUSIONS: We hypothesize, that circadian rhythmicity has evolved, during evolution, into a mechanism that prevents disruption of the organism's negative-feedback-loop homeostasis.
Yin and Yang concept emphasizes the reciprocal and interrelated nature; neither is sufficient, both are needed to sustain the overall balance of the living system. Changing the balance, by implementing deficiency or excess of one of them, upsets the equilibrium (homeostasis) of the whole system. PURPOSE: In this opinion article intermittent exposure is presented as the stimulus for development and evolutionary conservation of circadian rhythm, an endogenous, entrainable oscillation of approximately 24 h, to counteract/balance the cells' natural tendency to attenuate their response during long-term exposure to different endogenous substances. RESULTS: The concept of Yin and Yang duality is an allegory on which the avoidance of attenuation of the cells' responses hypothesis is presented as an explanation for the circadian rhythmicity, which is integrated in all human cells, with the exception of stem and cancer cells. CONCLUSIONS: We hypothesize, that circadian rhythmicity has evolved, during evolution, into a mechanism that prevents disruption of the organism's negative-feedback-loop homeostasis.