The first objective of the proposed research is to quantify the relationship between structural design and functional performance of the respiratory system. The PI's testing a hypothesis of economic design of biological systems. He will use an integrated systems approach, considering: all levels of transport of oxygen from the environment to the target organelles, the mitochondria; and the steps in transport of fuel from the capillaries to the mitochondria. This should help to define the factors that limit muscular work, and to determine those steps in the transport of oxygen and fuel, if any, where there is a built-in redundancy or safety factor. These studies should also make it possible to draw conclusions: about the importance of genetic determination of design at the organelle, cell, organ and system level; and about the potential for functional and structural adjustment in response to training or damage from injury or disease. The second objective is to test the hypothesis that desert animals possess special adaptations for dramatically reducing their food requirements when they are faced with prolonged shortages of food during droughts. Metabolic rate is affected by dietary energy intake in all mammals, including humans. It seems likely the dramatic changes proposed for desert animals will be simply an "exaggerated" response of general physiological mechanisms. Thus, our studies may provide important new insights into this response and its modulation in humans.
