Some exciting news, as reported by the Wall Street Journal, might make you glad that human blood is a renewable resource: "Giving old mice blood from young ones makes them smarter and improves such functions as exercise capacity, according to reports from two research teams that point to new ways to study and potentially treat diseases of aging. In one study, researchers at Stanford University and the University of California, San Francisco found that blood transfusions from young mice reversed cognitive effects of aging, improving the old mice's memory and learning ability. The report was published Sunday in the journal Nature Medicine. Two other reports appearing in Science from researchers at Harvard University found that exposing old mice to a protein present at high levels in the blood of young mice and people improved both brain and exercise capability. An earlier report by some of the same researchers linked injections of the protein to reversal of the effects of aging on the heart. ... What isn't known from all this research, said Buck Institute's Dr. [Brian] Kennedy, is whether young blood might also increase the life span of mice and, if so, what such implications for humans might be."