Tokyo stocks opened higher Wednesday, led by buying in tech shares after U.S. semiconductor giant Nvidia Corp. became the world’s most valuable company amid robust demand for artificial intelligence technology. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 275.96 points, or 0.72 percent, from Tuesday to 38,758.07. The broader Topix index was up 12.74 points, or 0.47 percent, at 2,728.50. On the top-tier Prime Market, gainers were led by insurance, mining and machinery issues. At 9 a.m., the U.S. dollar fetched 157.87-88 yen compared with 157.83-93 yen in New York …