As Europe's financial system looks increasingly precarious, the U.S. Federal Reserve allowed central banks of other countries to exchange their currency for American dollars, which the banks have had trouble raising from anxious investors. Central banks will then be able to lend the dollars out to investors. The coordinated move buoyed stocks around the world, with the European and Asian markets generally out of the red. In Japan, the Nikkei closed up 2.2 percent. It's the first time the Fed has swapped dollars with European banks since the worst periods of the 2008 financial crisis.