Tokyo stocks opened higher Thursday, supported by the overnight rise of the U.S. Dow Jones index, but gains were limited as investors mostly took to the sidelines ahead of more earnings reports from major Japanese companies. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 69.63 points, or 0.18 percent, from Wednesday to 38,272.00. The broader Topix index was up 9.31 points, or 0.34 percent, at 2,715.74. On the top-tier Prime Market, gainers were led by insurance, bank, and glass and ceramic product issues. At 9 a.m., the U.S. dollar fetched 155.38-39 yen compared wi…