Nikkei tumbled Tuesday, as investors fear over Italy\'s uncertainty. The 225-issue Nikkei Stock Average closed down 263.71 points, or 2.26 percent, from Monday at 11,398.81. The broader Topix index of all First Section issues on the Tokyo Stock Exchange fell 13.93 points, or 1.42 percent, to 966.77. The decliners were precision equipment makers, steel makers and metal products producers, while gainers were real estate, fishery and forestry, and sea transport companies. The turnover was about 2,212 billion yen (about 24.07 billion U. S. dollars).