SAPK mediates homeostatic and developmental outcomes in TSC and embryos after stimulation by several stressors. It is not yet understood how dose- and time-dependent effects are enzymatically integrated by stem cells in the embryo. But, recent results suggest that for two stressors, hyperosmolar sorbitol and benzopyrene, homeostatic events occur over a broad range of concentrations, but cell accumulation and developmental (differentiation) effect occur at higher doses that begin at a shared common minimum threshold dose. [Wang et al. 2005, 2009; Xie et al. 2006b, 2007a, 2007b, 2008; Zhong et al. 2007; submitted].