Lulu Miller

A stint as lion tamer in Hollywood got Steven Austad interested in animal biology. And soon he turned from training animals to studying them. He's now chair of the biology department at the University of Alabama at Birmingham, where his research focuses on aging.

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DAVID GREENE, HOST:

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MARY LOUISE KELLY, HOST:

Mike Marsella was a really competitive guy, a champion cross-country runner in high school. He got a running scholarship to college. Then a car hit him while he was riding a moped. He was left in a coma, with brain damage. And when his mind changed, his running changed, too.

Would he ever be Mike Marsella again? And would he ever run a four-minute mile?