Updated from 4:25 p.m. EST

Stocks ended higher as several high-profile acquisitions convinced investors that corporate America was shaking off its doldrums.

The

Dow Jones Industrial Average gained 81 points, or 0.82%, to 9892, while the

Nasdaq was up 34 points, or 1.75%, to 19878, and the

S&P 500 was gaining 11 points, or 1%, to 1134.

In the day's biggest deal,

Amgen

(AMGN) - Get Report

said it will buy rival

Immunex

(IMNX)

for cash and stock worth about $30 a share, or $16 billion altogether. The acquisition would give Amgen, already the world's biggest biotech company, access to Immunex's rheumatoid arthritis treatment Enbrel. Amgen gained $3.38, or 6.03%, to $59.41 while Immunex tacked on $3.45, or 13.5% to $29.07.

Also Monday,

Vivendi

(V) - Get Report

confirmed it will exchange cash and stock worth $10.3 billion for the entertainment assets of

USA Networks

(USAI) - Get Report

. The deal calls for the establishment of a new company, Vivendi Universal Entertainment, to be headed by USA chief Barry Diller. Vivendi closed up $3.23, or 6.6%, to $52.18 while USA Networks added 95 cents to $24.77.

A bidding war broke out over the weekend for

P&O Princess Cruise Lines

(POC)

, which previously agreed to a friendly merger with fellow cruise operator

Royal Caribbean

(RCL) - Get Report

.

Carnival

(CCL) - Get Report

entered the fray with a hostile $4.5 billion offer that P&O rejected, citing among other things greater "regulatory risk" in Europe and the U.S. P&O's shares rose $1.26 to $22.30, while Royal Caribbean's stock lost $1.94 to $14.39. Carnival was off 43 cents to $26.87.

The yen touched a three-year low against the dollar and two-year low against the euro after a Japanese government official's comment suggested the country wouldn't support the currency at current levels. The yen "is in a phase to correct its level, which was too strong" given the economic outlook, Japanese Vice Finance Minister Haruhiko Kuroda said, according to

Bloomberg

.

European stocks rose sharply, with London's FTSE 100 up 1.5% to 5136 and Germany's Xetra DAX up 3.5% to 5080. In Japan, the Nikkei fell 1.8% to 10,323, while Hong Kong's Hang Seng was unchanged at 11,466.

In London, crude oil futures were down about 2% after OPEC said planned production cuts might be delayed.

At 4 p.m. EST Treasury issues were weaker with the 10-year note off 4/32 to 98 15/32, yielding 5.20%.