PHYSIOLOGIC 24-HOUR PERIODICITY IN HUMAN 



BEINGS AND MICE, THE LIGHTING REGIMEN 



AND DAILY ROUTINE' 



FRANZ HALBERG, ERNA HALBERG, CYRUS P. BARNUM 



and JOHN J. BITTNER 

 The Division of Cancer Biology, Department of Pathology and the 

 Department of Physiologic Chemistry, University of Minnesota, 

 Minneapolis, and the Cambridge State School and Hospital, Cam- 

 bridge, Minnesota 



Among the various characteristics of a given periodic function, we 

 want to measure, of course, its period, amplitude, and phase. The 

 omission of such measurements is hardly a matter of choice; it is a 

 problem of practicability, which often can be overcome. It may be 

 appropriate, therefore, to allude first to the uses (and limitations) of 

 the periodogram technique, as it can be applied to biologic wave 

 analysis. Some illustrative results may stimulate endeavors for improv- 

 ing the measurement of cyclic characteristics in physiologic work 

 beyond the application of periodograms, which serve herein merely as 

 first approximations. Periodograms will then be applied to the study of 

 daily periodicity, as it occurs in blinded animals, apparently in the ab- 

 sence of photic effects. Thereafter, we shall turn to basic mechanisms, 

 which maintain certain rhythms in an "aperiodic" environment: inter 

 alia, the adrenal cycle and a periodic sequence of events in the cell. 

 Thus we shall set the stage for exploring a broad field of photic effects, 

 exerted at different levels of mammalian organization. It will become 

 apparent that certain phase relations of 24-hr periodic functions are 

 critically controlled by the environment, while the period of the same 

 phenomena is relatively independent of light and temperature. Most of 

 the data will describe mice, but the studies were carried out with man 

 in mind, and findings on human beings will be included. For several 



1 Supported by the Elsa U. Pardee Foundation, the Department of Public 

 Welfare, State of Minnesota, the American Cancer Society, the U. S. Public 

 Health Service, the Graduate School at the University of Minnesota, and the 

 United States Testing Company, Hoboken, New Jersey. 



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