Tokyo stocks opened sharply higher Wednesday following overnight gains on Wall Street and the U.S. dollar’s rise to a six-year high against the yen that triggered strong demand for export-oriented shares. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 482.64 points, or 1.77 percent, from Tuesday to 27,706.75. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was up 25.22 points, or 1.30 percent, at 1,958.96. Gainers were led by securities house, electric appliance and transportation equipment issues. At 9 a.m., the dollar fetched 121.3…