Take a look at some of Monday's midday movers:
Twitter moved higher after its co-founders, Jack Dorsey and Evan Williams, along with CEO Richard Costolo, all said they have no plans to sell any of their company shares.
General Motors gained ground. The automaker said the heads of its communications and human resources divisions would be leaving the company.
Citigroup climbed after reporting better-than-expected quarterly earnings.
WebMD Health soared after the health information provider said it expected its first-quarter results to top its earlier forecast, due in part to an improvement in sales.
Edwards Lifesciences gained and Medtronic fell after Edwards Lifesciences won a preliminary injunction limiting the sale of Medtronic's CoreValve system. A federal jury in 2010 found the system infringed on a patent held by Edwards.
J.M. Smucker rose on news it raised its share repurchase plan by five million shares.
Walgreen moved higher. The Financial Times reported the drugstore chain is under pressure from a group of shareholders to consider relocating to Europe to gain tax benefits.
Yahoo! gained ground after SunTrust upgraded the stock to buy from neutral, with a $40 price target, citing valuation.
Orbitz Worldwide rose after the online travel company named Scott Forbes as its non-executive chairman, replacing Jeff Clarke, who resigned.
Nabors Industries advanced after the oilfield services and drilling company said it would separate the roles of chairman and CEO after the tenure of CEO Anthony Petrello ends. It will also limit severance payments for executives.
Bebe Stores moved higher after Janney Montgomery Scott upgraded the stock to buy from neutral.
Stratasys climbed after Goldman Sachs began coverage with a buy rating and $146 price target.
3D Systems fell after Goldman began coverage with a neutral rating and $63 price target.
Pandora Media rose after SunTrust began coverage with a buy rating and $34 price target.
Xerox moved higher after Piper Jaffray repeated an overweight rating, saying the stock is a compelling "old stock" play.
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—By CNBC's Rich Fisherman.
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