Tokyo stocks opened lower Wednesday, tracking an overnight fall of the U.S. Nasdaq index, with some export-oriented issues losing ground after the yen strengthened against the U.S. dollar overnight. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 157.15 points, or 0.59 percent, from Tuesday to 26,590.99. The broader Topix index was down 9.51 points, or 0.51 percent, at 1,868.75. On the top-tier Prime Market, decliners were led by service, air transportation and transportation equipment issues. At 9 a.m., the dollar fetched 126.71-76 yen compared with 126.80-90 yen i…