8,9 What this nonlinearity

means is that when any one mediator is increased or decreased, there are compensatory changes in the other mediators that depend on time course and level of change of each of the mediators. Unfortunately, we cannot measure all components of this system simultaneously, and must rely on measurements of only a few of them in any one study. Yet the nonlinearity Inhibitors,research,lifescience,medical must be kept in mind in interpreting the results. Stress in the natural world The operation of allostasis in the natural world provides some insight into how animals use this response to their own benefit or for the benefit of the species. As an example of allostasis, in spring, a sudden snowstorm causes stress to birds and disrupts mating, and stress hormones are pivotal in directing the birds to suspend reproduction, to find a source of food, and to relocate to a better mating site, or at Inhibitors,research,lifescience,medical least to delay reproduction until the weather improves.10 As an example of Z-VAD-FMK cell line allostatic load, bears preparing to hibernate for the winter Inhibitors,research,lifescience,medical eat large quantities of food and put on body fat to act as an energy source during the winter.11 This accumulation of fat is used, then, to survive the winter and provide food for gestation of young; this is in contrast to the fat accumulation that occurs in bears that are captive in zoos and eating too much, partially out

of boredom, while not exercising.4 The accumulation of fat under these latter conditions can be called “allostatic overload,” referring Inhibitors,research,lifescience,medical to a condition that is associated with pathophysiology. However, allostatic overload

can also have a useful purpose for the preservation of the species, such as In migrating salmon or the marsupial mouse, which die of excessive stress after mating- the stress, and allostatic Inhibitors,research,lifescience,medical load, being caused for salmon, In part, by the migration up the rapidly flowing rivers, but also because of physiological changes that represent accelerated aging.12-14 The result is freeing up food and other resources for the next generation. In the case of the marsupial mouse, it is only the males that die after mating, due apparently to a response to mating that reduces the binding protein, corticosteroid-binding globulin (CBG), for glucocorticoids and renders them much more active throughout the body.15 Being “stressed out”, especially sleep deprivation and its during consequences The common experience of being “stressed out” has as its core the elevation of some of the key systems that lead to allostatic load- Cortisol, sympathetic activity, and proinflammatory cytokines, with a decline in parasympathetic activity. Nowhere is this better illustrated than for sleep deprivation, which is a frequent result of being “stressed out.” Sleep deprivation produces an allostatic overload that can have deleterious consequences.