Biological rhythms cAMP oscillations

Some of the main examples of biological rhythms of nonelectrical nature are discussed below, among which are glycolytic oscillations (Section III), oscillations and waves of cytosolic Ca + (Section IV), cAMP oscillations that underlie pulsatile intercellular communication in Dictyostelium amoebae (Section V), circadian rhythms (Section VI), and the cell cycle clock (Section VII). Section VIII is devoted to some recently discovered cellular rhythms. The transition from simple periodic behavior to complex oscillations including bursting and chaos is briefly dealt with in Section IX. Concluding remarks are presented in Section X. 

The onset of cAMP oscillations in Dictyostelium as a model for the ontogenesis of biological rhythms... 

These results are of general significance for the study of biological rhythms as they show how the continuous variation of certain control parameters can lead to the emergence of a rhythm in the course of development of an organism. Here, the level of certain proteins augments once the amoebae begin to synthesize the components of their intercellular communication system after starvation. As soon as the concentration of the cAMP receptor and the activity of enzymes such as adenylate cyclase and phosphodiesterase reach a critical value, oscillations appear spontaneously. Rinzel Baer (1988) have shown, however, that a certain delay separates the time at which the parameters cross their bifurcation values and the moment at which oscillations... 

Many models for biochemical oscillations rely on positive feedback, as illustrated in this book by the case of glycolytic (chapter 2), cAMP (chapter 5) or (chapter 9) oscillations. Instabilities can, nevertheless, also arise from negative regulation. Together with the models discussed in chapter 10 for the mitotic oscillator in embryonic cells, for which a combination of positive and negative feedback may contribute to periodic behaviour, the model for circadian oscillations in the period protein in Drosophila supports the view that negative feedback is at the core of some of the most important biological rhythms. 

Goldbeter, A. J.L. Martiel. 1988. Developmental control of a biological rhythm the onset of cAMP oscillations in Dictyostelium cells. In From Ghemical to Biological Organization. M. Markus, S. Muller G. Nicolis, eds. Springer, Berlin, pp. 248-54. 

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