The Bombay Stock Exchange benchmark Sensex gained over 127 points in opening trade on Wednesday on the back of bargain buying by funds and retail investors, ignoring a weak trend overseas. The 30-share index, which lost nearly 400 points in the previous three sessions, rose by 127 points to 16,859 in the first few minutes of trade on Wednesday. In a similar fashion, the wide-based National Stock Exchange Nifty index moved up by 37 points, to 5,073.10 in the first few minutes of trade.