How Much of Stress Do We Need?
The G1 phase of the cell cycle determines if a cell is to differentiate or not. During this phase, the cell develops protuberances(cilia) which sense the environment, effect movement and in turn stimulate autophagy(nerve and muscle cells are much elongated from these protuberances). Levels of Nrf2, which lower levels of free radicals, fall in this pro-differentiation state. The longer the G1 the more likely the switch to differentiation from cell cycling. When there is transient fall in energy resources or growth factors, there will be less proliferation and more pro-differentiation, and when those resources later become available, more pronounced differentiation will take place. Transient spike in psychological, physical or nutritional stress will cause the engagement of the 5-phosphate pentose pathway that yields the anti-oxidant NADPH, and as well produces intermediates for protein synthesis. This promotes cellular prolif...