The Sensex at the Bombay Stock Exchange opened with a small loss of 16 points, at 16,508, on Wednesday morning, amid a mixed trend in the regional bourses. Later, the Sensex remained range bound, and stood a slim 33 points, or 0.2 per cent in negative territory, at 16,491 in afternoon deals, a short while ago.Other Asian markets in Japan, Indonesia, Taiwan, Singapore, South Korea, China and Hong Kong were trading mixed, as concerns returned about Europe's ability to tackle its debt problems.