M&A news and quarterly updates provided some of the catalysts behind the most actively traded stocks on Monday.
Shares of Nokia gained in heavy trading on Monday after the world's largest mobile phone maker raised its market share forecast for the second quarter. Nokia expects to widen its lead on rival Motorola by working off excess inventory, which limited gains in the first quarter.
"We believe that this improvement in inventories, largely a flushing out of excess Motorola devices in the channel, is a positive for the handset industry in general," said Prudential analyst Inder Singh. "We were already modeling a slight increase in second- and third-quarter market share for Nokia, and today's announcement could mean some possible upside to second-quarter numbers."
Viasys Healthcare shares surged more than 30% after the company agreed to be acquired by Cardinal Health for about $1.5 billion.
Advanced Micro Devices rose more than 4% after American Technology Research upgraded the stock to "buy" from "sell," predicting the chipmaker will win a laptop deal with Toshiba and increase its business with Dell.
"We are looking for AMD to continue to gain share in the notebook space," said analyst Jim Freedman.
Tiny drugmaker Critical Therapeutics rocketed to gains of 55% after the U.S. Food and Drug Administration approved marketing partner Dey's Perforomist, an emphysema and chronic bronchitis treatment. The company will co-market the drug in the U.S. but awaits an FDA decision on its experimental asthma treatment Zyflo.
On the losing side, shares of Mylan Laboratories fell sharply amid a huge jump in volume after the company said it will buy Merck KGaA's generic drug business for $6.6 billion in cash.
"Although we like the boldness of the move, we also feel Mylan will be under pressure until visible and measurable successes are achieved -- and that will take time," said Cowen analyst Ken Cacciatore.