The Sensex at the Bombay Stock Exchange gained 70 points, or 0.4 per cent, to 17,632, in early trade, today, on fresh buying by investors, amid encouraging quarterly results announced by oil major, ONGC. But later, the Sensex gave up all its initial gains, on mild selling pressure, to stand 75 points, or 0.4 percent in negative territory, at 17,488 in afternoon deals a short while ago.Other Asian markets in Japan, Singapore, South Korea, China, Hong Kong, and Indonesia were trading mixed, today, on euro-zone debt worries. But over on Wall Street, the Dow Jones Industrial Average had gained 0.7 per cent, overnight. MM/1330hrs