Giving up most of its initial gains, the Sensex at the Bombay Stock Exchange stood just 4 points in positive territory, at 18,749, in volatile afternoon trade, a short while ago. Earlier in the morning, however, the Sensex had opened with a gain of 80 points, or 0.4 per cent, at 18,825, after some encouraging quarterly corporate results, and mostly rising Asian markets. The 30-share Sensex had climbed over 500 points in the previous two trading sessions.Stock markets in Japan, Hong Kong, Taiwan, Singapore and Indonesia had gained between 0.2 percent and 1.2 percent, today. The US Dow Jones Industrial Average ended 1.1 per cent higher in yesterday's trade.