The Sensex at the Bombay Stock Exchange was trading a mammoth 436 points in the negative territory at 16,629 a short while ago. In opening trade, the Sensex lost nearly 300 points, amid panic selling in markets worldwide following the US Federal Reserve's warning that the outlook for the world's largest economy is grim.In a similar fashion, the wide-based National Stock Exchange Nifty index was trading 134 points in the red at 4,999 points.In the Asian region, Japan's Nikkei index was trading 2.12 per cent lower, while Hong Kong's Hang Seng Index tumbled by 4.11 per cent in early trade today. The US Dow Jones Industrial Average closed 2.49 per cent lower in yesterday's trade.