LOMA LINDA, Calif. (AP) — Dr. Leonard Bailey, who in 1984 transplanted a baboon heart into a tiny newborn dubbed "Baby Fae" in a pioneering operation that sparked both worldwide acclaim and condemnation, has died. He was 76.

Bailey died Sunday after a long battle with cancer, said a statement from Loma Linda University Health, the nonprofit organization that runs the hospital 60 miles (nearly 97 kilometers) from downtown Los Angeles where Bailey worked for more than four decades.

Baby Fae — whose real name was Stephanie Fae Beauclair — was born premature with a congenital heart defect called hypoplastic left heart syndrome.

"At that time, babies born with certain kinds of exotic heart disease weren't even treated — they were set aside to die. And they uniformly did that," Bailey recounted in an interview with a Loma Linda publication in 2007. "I had encountered some of those babies. We tried various things to see if we could prolong their lives. Mostly we prolonged their dying, maybe by a few days. But we had no success at all in saving them."

Bailey and others had been experimenting with cross-species transplants in the laboratory.

With no human infant heart available for transplant, Bailey decided on a radical procedure: when Baby Fae was 12 days old, he transplanted the tiny heart of a baboon into her body.

Baby Fae died 21 days later but the operation was seen as a pioneering scientific advance.

"Baby Fae helped absolutely transform the landscape of pediatric heart transplants, generating unprecedented levels of public awareness," Loma Linda said on its website. "People everywhere learned of the pressing need for infant organ donation. In addition, an entire generation of students was inspired to follow in Dr. Bailey's footsteps and become pediatric surgeons."

But animal rights activists saw it as unethical and ghoulish.

"The hate mail and threats poured in for a long time, so much so that the ... police wanted us to let them open our mail and things like that," Bailey recalled.

The year after Baby Fae's operation, Bailey performed the first successful human infant-to-infant heart transplant.

Bailey went on to perform nearly 400 infant heart transplants at Loma Linda, where he was a professor and surgeon-in-chief at Loma Linda University Children's Hospital.

"His work also propelled Loma Linda University Health to become the world's leading pediatric heart transplant center and led to innovations that enable surgeons to repair certain complex congenital heart defects instead of patients having to undergo a transplant," the organization said.

Bailey is survived by his two sons, Brooks and Connor, and two grandchildren.