Tokyo stocks opened slightly up Tuesday, tracking overnight gains on Wall Street, although advances were limited as investors continued to lock in gains after a recent surge of the Nikkei index. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 127.89 points, or 0.31 percent, from Friday to 41,318.57. The broader Topix index was up 14.76 points, or 0.51 percent, at 2,909.32. Japanese financial markets were closed Monday for a national holiday. On the top-tier Prime Market, gainers were led by insurance, securities and mining issues. At 9 a.m., the U.S. dollar fetched …