Running on Empty: No Oxygen Needed!

The green sea turtle

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Take a deep breath in. Now breathe out. Each time we breathe, oxygen enters the bloodstream to keep our organs alive and working. When oxygen can’t get to our body’s tissues, they begin to fail. This is true of all organs, but most of all the brain. In conditions like stroke and cardiac arrest—when the heart suddenly stops working—loss of oxygen and nutrients damages cells in the brain. Often, even the best-case scenario is bleak. People who survive these conditions may be permanently disabled, making it difficult to walk, talk or work. In the worst case, people die from extensive brain damage.

Researchers have tried tirelessly to create new therapies and drugs that make the brain resistant to damage caused by oxygen deprivation. In the process of inventing new treatments, scientists—including those that specialize in comparative physiology—are trying to learn from animals that already have brains that can survive without oxygen. Comparative physiology is a branch of physiology that, in part, studies how different animals survive in environments that usually injure or kill humans.

In looking to nature, there are several animals that can get by with little to no oxygen for long periods of time. Examples include naked mole rats that spend their lives in burrows with very low oxygen and turtles that hibernate through the winter in ponds covered by a sheet of ice. Other animals, such as the hooded seal, don’t live in low-oxygen environments full-time but may need to survive temporary loss of oxygen while they look for food. These seals can dive underwater for up to an hour without a single breath of air while they hunt for their dinner.

These amazing feats may make us wonder how animals are able to survive without an element that’s essential to keeping the human brain alive. So far, researchers have discovered a number of strategies that animals use to protect the brain in low-oxygen environments. Some of these include shutting down the connections between nerve cells to protect the brain and changing the kind of fuel the brain uses to make energy to minimize brain damage.

Animals may use one or a combination of these different strategies depending on their particular situation. Their behavior tells us that nature has already found solutions for diseases that damage the human brain. Observing the habits of animals gives physiologists new perspectives on how we might fix problems that threaten our health and lives. I, for one, am excited to learn what new and important findings animals will teach us next.

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Joe Santin, PhD, is an assistant professor in the department of biology at the University of North Carolina-Greensboro.

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