Researchers found a protein in human umbilical cord plasma improved learning and memory in older mice, but there's no indication it would work in people.
Decades ago, scientists surgically attached pairs of rats to each other and noticed that old rats tended to live longer if they shared a bloodstream with young rats.
It was the beginning of a peculiar and ambitious scientific endeavor to understand how certain materials from young bodies, when transplanted into older ones, can sometimes improve or rejuvenate them.
