Chapter 26 Cellular oscillators and biological timing: the role of proteins and Ca2+

Abstract

Publisher Summary In the control of growth and reproduction, biological timing mechanisms as well as peptidergic neurons and endocrine cells play important roles, and the timing of sleep and waking in mammals depends on a circadian oscillator in each of the bilateral suprachiasmatic nuclei (SCN) of the hypothalamus. This chapter describes what is presently known about three oscillators, two of which are ultradian (Ca 2+ oscillations and the cell division cycle). Circadian cycles of activity are commonplace in multicellular animals and unicellular eukaryotes as are circadian cycles of photosynthesis, petal movements, and streaming in plant cells, for example, time of day measurement is in bird navigation. In poikilotherms, biological clocks would be useless as timing devices, if they respond passively, as biochemical machines, to environmental temperature changes. Cyclin appears to be the master oscillator. Investigations into the biochemical basis of the circadian oscillation are in their infancy. However, much more needs to be learned about the genes and proteins that are expressed during a circadian cycle before common patterns among different phyla will reveal what has been conserved in the course of evolution.