The Nikkei stock index climbed Monday morning after U.S. shares advanced late last week, but gains were limited due to growing caution following the market’s recent sharp rises. The 225-issue Nikkei Stock Average rose 87.43 points, or 0.21 percent, from Friday to 40,999.80. The broader Topix index was down 3.86 points, or 0.13 percent, at 2,880.32. On the top-tier Prime Market, gainers were led by precision instrument and pharmaceutical issues, while marine transportation and insurance issues led decliners. The U.S. dollar dropped to the lower 160 yen zone, weighed down by prospects for early …