Nikkei opened 1.63 percent higher Wednesday, following overnight gains on Wall Street stimulated by solid U.S. factory orders report. At 9:15 a.m., the 225-issue Nikkei Stock Average gained 195.74 points, or 1.63 percent, from Tuesday to 12,199.17. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was up 8.00 points, or 0.81 percent, to 999. 34.