Tesla Motors fell as investors considered the ramifications of three of its Model S electric cars catching fire during the past month.
Western Refining gained after it said it would buy a controlling stake in Northern Tier Energy for about $775 million.
Symantec declined after Macquarie downgraded the stock to neutral from outperform following the departure of the security-software provider's president of products and services.
Vanda Pharmaceuticals surged after an FDA panel recommended approval of its sleep-disorder drug for the blind.
Sarepta Therapeutics plummeted after the FDA raised doubt about its experimental muscle dystrophy drug, calling the application premature.
GlaxoSmithKline fell after its experimental heart-disease treatment failed a late-stage clinical trial.
NRG Energy dropped after the company lowered its earnings guidance for the year and reduced its forecast for next year.
Heartland Express climbed after the trucking firm agreed to acquire Gordon Trucking for about $300 million.
Qualcomm jumped as Jefferies began coverage with a buy rating and a price target of $80 due to strength in its licensing business.
Amedisys fell after the home-healthcare provider reported a quarterly loss, largely due to a $150 million charge for a tentative settlement of an investigation by the Department of Justice.
Xerox rose after adding $500 million to its buyback plan.
Regal Entertainment and Cinemark Holding gained after Jefferies upgraded both film makers to buy from neutral.
Yingli Green Energy Holding fell after the Chinese solar-panel manufacturer reported a wider-than-expected loss.
Dean Foods declined after the milk processor cut its full-year adjusted earnings forecast.
(Read More: See CNBC's Market Insider Blog)
—By CNBC's Rich Fisherman.
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