The Sensex at the Bombay Stock Exchange rose 42 points to 17,193 in early trade, this morning, on covering-up of short positions by speculators for end-of-the-monthly expiry in the derivatives segment. But the Sensex later gave up all its gains, in very volatile trade, and stood just 2 points in negative territory, at 17,149 in afternoon trade, a short while ago.Elsewhere, reversing initial gains, key stock indices in Japan, China, Singapore, South Korea and Taiwan were down by between 0.1 percent and 0.5 percent, today. Over on Wall Street, the Dow Jones Industrial Average had gained 0.7 per cent in yesterday's trade