Tokyo stocks opened sharply higher Thursday, with the Nikkei index briefly hitting a 34-year high above the 35,000 threshold, lifted by gains of exporter and technology issues on a weaker yen and Wall Street rises overnight. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 499.44 points, or 1.45 percent, from Wednesday to 34,941.16. The broader Topix index was up 36.99 points, or 1.51 percent, at 2,481.47. On the top-tier Prime Market, gainers were led by transportation equipment, securities house and insurance issues. At 9 a.m., the U.S. dollar fetched 145.71-74 yen…