The Nikkei stock index extended its losses Wednesday afternoon, falling more than 2 percent, as exporters were hit by the yen’s appreciation against the U.S. dollar. The Nikkei fell below 35,500 in the late afternoon. The U.S. dollar slid to an eight-month low in the upper 140 yen zone after a speech by a Bank of Japan policymaker was interpreted as showing a positive stance on raising interest rates.