Tokyo stocks were lower Thursday morning as investor caution over heavyweight chip-related stocks fueled selling ahead of an earnings release from a major Taiwanese semiconductor firm later in the day. The 225-issue Nikkei Stock Average fell 235.37 points, or 0.60 percent, from Wednesday to 38,944.93. The broader Topix index was down 0.50 point, or 0.02 percent, at 2,690.16. The U.S. dollar briefly weakened to the lower 149 yen range, as traders sold the dollar after the pair tracked close to the 150 yen line, analysts said. The yen had been sold in recent days on prospects the United States w…