Narrow Results

Cells are continuously subjected to noisy internal and external environments. Though cellular functions are carried on quite reliably under such noise, they can also result in fluctuations of parameters of the various biochemical processes and cause the dynamics of the reaction pathway to change. To show the varied effects of noisy environment on cellular dynamics, we consider a model cell containing a minimal biochemical pathway that exhibits a wide array of dynamical behaviors – from equilibrium, simple limit cycles and higher periodics, birhythmicity, complex oscillations and chaos - that are observed in many cellular functions. We show that, even under constant parameters, small fluctuations in the variables (i.e., substrate concentrations) can facilitate switching of the dynamics between oscillatory states with very different amplitudes and frequencies. The final temporal behavior of the pathway is unpredictable for the range of parameters where birhythmicity is observed. Parametric noise can mask the original dynamics of the pathway in the birhythmic state, though considerable robustness in dynamics is seen in the presence of noise for other values of parameters. Thus we show that the cellular dynamics can exhibit both robust and non-robust behavior in noisy environment for different parameters in the same pathway.

Honey bee nectar foragers returning to the hive experience a delay as they search for a receiver bee to whom they transfer their material. In this paper I describe the simulation of the "threshold rule" (Seeley, 1995) which relates the magnitude of this search delay to the probability of performing a recriutment dance — waggle dance, tremble dance, or no dance. Results show that this rule leads to self-organised near-optimal worker allocation in a fluctuating environment, is extremely robust, and operates over a wide range of parameter values. The reason for the robustness appears to be the particular sytem of feedbacks that operate within the system.