Maintaining the upward trend, the Sensex at the Bombay Stock Exchange was trading 316 points in the positive territory at 18,164 in afternoon trade, when reports last came in.After gaining almost 100 points in last two trading sessions, the 30-share index shot up by 209 points in opening trade today, to regain the 18,000 level. The rise was attributed to sustained buying by funds and retailers on better-than-expected quarterly earnings by corporates.In a similar fashion, the wide-based Nifty of the National Stock Exchange was trading 99 points up at 5,515.In Asia, Hong Kong's Hang Seng Index rose by 0.09 per cent, while Japan's Nikkei Index by 1 per cent in early trade. The Dow Jones Industrial Average ended higher by 0.03 per cent yesterday.