The Nikkei index ended sharply lower Friday, logging its biggest point drop since June 2016, as a spike in the yields of U.S. and Japanese long-term bonds triggered concern about market stability and possible changes to monetary easing.The 225-issue Nikkei Stock Average ended down 1,202.26 points, or 3.99 percent, from Thursday at 28,966.01, falling below the 29,000 line for the first time since Feb. 5. The broader Topix index of all First Section issues on the Tokyo Stock Exchange finished 61.74 points, or 3.21 percent, lower at 1,864.49.The U.S. dollar moved around the 106 yen line, caugh…READ FULL ARTICLE