The Sensex at the Bombay stock Exchange rose 48 points, or 0.2 per cent, to 17,270 in opening deals, this morning, on selective buying by funds and retail investors. But the Sensex later gave up all its initial gains, in volatile trade, and stood 51 points, or 0.3 per cent in negative territory, at 17,172 a short while ago. The 30-share Sensex has lost more than 375 points in the past two trading sessions. Other regional stock markets in Japan, China, Hong Kong, Indonesia, Singapore and Taiwan were trading mixed.