Body cells change gears to use less oxygen under stress and crises conditions such as a heart attack or stroke, researchers at Johns Hopkins discovered.

Too little oxygen kills cells by compromising the mitochondria ? the powerhouses that run them. When oxygen is scarce, cells adjust by replacing one protein with an energy-efficient substitute “specialized to keep the motor running smoothly even as it begins to run out of gas,” said Dr. Gregg Semenza, professor of pediatrics and director of the vascular biology program in the Institute for Cell Engineering at Johns Hopkins.