Tokyo stocks opened lower Wednesday, weighed down by selling of some exporters on a stronger yen against the U.S. dollar and overnight falls on Wall Street. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 293.83 points, or 0.77 percent, from Tuesday to 37,769.09. The broader Topix index was down 15.57 points, or 0.58 percent, at 2,654.97. On the top-tier Prime Market, decliners were led by mining, insurance, and oil and coal product issues. At 9 a.m., the dollar fetched 145.32-33 yen compared with 145.19-29 yen in New York and 146.55-57 yen in Tokyo at 5 p.m. Tuesda…