The Effects of Actinomycin D and Acth on Circadian Steroidogenesis of Hamster Adrenals

Abstract

Rhythmicity is predominant in nature. Sunrise is followed by sunset in a highly predictable periodic sequence. Living organisms are known to be influenced by such periodically occurring phenomena. De Mairan, as early as 1729, observed leaf movements of plants and found these variations to be coincident to the solar period. His observations have been confirmed by other workers as Pfeffer, Bunning, Kalmus and Kleitman. An animal's activity pattern has been called diurnal or nocturnal again in relation to the environmental photo- period of the animal. | A biorhythm is any regularly recurring change in some biological process, whether it takes place in a cell, tissue, organ, organism or population. Such biorhythms are classified as exogenous or endogenous in origin (Bunning, 1964; Aschoff, 1960; Sollberger, 1965). | Environmental factors which induce or synchronize rhythmic processes are called Zeitgebers (Aschoff, 1960) or Synchronizers (Halberg, 1954). These may be overt cues such as light and temperature or more subtle geophysical factors such as electrostatic and magnetic force fields (Brown, 1960, 1965).