The Sensex at the Bombay Stock Exchange rose 73 points, or 0.4 per cent, to 18,511 in opening trade, this morning, on fresh buying by funds and retail investors, amid positive Asian bourses. Later, after rising more than a hundred points at one stage, the Sensex gave up most of its gains, to stand just 18 points, or 0.1 percent in positive territory, at 18,455 in volatile afternoon trade, a short while ago. The Sensex had lost over 600 points in the previous four trading sessions.Stock markets in Japan, China, South Korea, Hong Kong, Indonesia and Singapore had gained between 0.1 percent and 1 percent, today, after benign inflation data from China. The US Dow Jones Industrial Average ended 0.3 per cent higher in yesterday's trade.