The yen fell to its lowest level since 1986 against the US dollar on Wednesday, leaving currency markets on alert for any sign of intervention by Japanese authorities to shore up the beleaguered currency. USDJPY traded at 160.39 yen, a level last seen in December 1986, as the wide interest rate gap between the two countries continued to weigh on Japan's currency. Analysts say traders are testing the resolve of Japan's Treasury and central bank, which spent $62 billion in late April and early May to prop up the currency as it fell above 160. “If the underlying dynamics don't change...