Tokyo stocks tumbled in the morning session of Tuesday, with the Nikkei index ending nearly 400 points lower influenced by the yen's appreciation against the U.S. dollar and weaker-than-expected U.S. manufacturing data. The 225-issue Nikkei Stock Average dropped 382.54 points, or 2. 62 percent, from Monday to end the morning at 14,236.59, after slumping to as low as 14,121.05, the lowest intraday level since early November. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was down 37.03 points, or 3.10 percent, at 1, 159.29. All of the 33 industry indexes fell, with the nonferrous metal, machinery and mining sectors leading the way.