Oxygen regulation in biological systems

Introduction Oxygen is a fascinating molecule. Much of the animal kingdom depends on it for survival, yet it is also a poison. Humans and other animals must inhabit environments with varied availability of oxygen, and either through necessity or choice, can be acutely exposed to hypoxia or hyperoxia. Furthermore, both cellular hypoxia and oxidative stress have been identified as major factors in the development of multiple pathological states. These considerations provided the impetus for a call for papers in this journal, entitled Oxygen as a Regulator of Biological Systems. Herein, I discuss some of the recent advances in this field identified in the pages of American Journal of Physiology ? Regulatory, Comparative and Integrative Physiology. Rather than provide detailed descriptions of the findings described in these articles, I attempt to highlight the critical new concepts that have arisen, in the hope that the interested reader will go to the original sources.