The top after-market NASDAQ stock market gainers are: Magma Design Automation, Transcept Pharmaceuticals, Merge Healthcare, Yahoo and Exide Technologies. The top after-market NASDAQ stock market losers are: Semtech, Sonus Networks, Digital Generation, Prospect Capital and Connecticut Water Service.

Gainers

Magma Design Automation Inc. (LAVA) stock jumped 26.79 percent to $7.25 in after-market trading. Synopsys Inc. (SNPS) said it agreed to buy Magma Design Automation for $7.35 per share in cash, resulting in a transaction value of about $507 million net of cash and debt acquired. The boards of directors of both companies have unanimously approved the transaction. In the event the merger closes as expected in the second calendar quarter of 2012, Synopsys anticipates the merger to modestly add to its adjusted earnings per share in its fiscal 2012. Synopsys plans to fund the acquisition with a combination of cash and debt, with the specifics to be determined at the time of close.

Transcept Pharmaceuticals, Inc. (TSPT) stock climbed 12.57 percent to $7.88 in after-market trading. The company said Purdue has exercised its option to commercialize Intermezzo in the U.S. Purdue intends to launch Intermezzo in the second quarter of 2012 and to invest about $100 million to support sales and marketing during the first year of commercialization. On Nov. 23, the U.S. Food Drug Administration approved Intermezzo (zolpidem tartrate) sublingual tablet C-IV for use as needed for the treatment of insomnia when a middle-of-the-night awakening is followed by difficulty returning to sleep. Intermezzo is not indicated for the treatment of middle-of-the-night insomnia when the patient has fewer than 4 hours of bedtime remaining before the planned time of waking. Middle-of-the-night awakening with difficulty falling back to sleep is a common sleep problem and Intermezzo was the first and is the only prescription sleep aid approved for dosing in the middle of the night to treat this form of insomnia.

Merge Healthcare Inc. (MRGE) stock grew 10.86 percent to $6 in after-market trading. The shares closed Wednesday's regular trading up 4.64 percent at $5.41.

Yahoo Inc. (YHOO) stock gained 6.41 percent to $16.72 in after-market trading. Blackstone Group and Bain Capital are preparing a bid for all of Yahoo with Asian partners in a deal that could value the Internet company at about $25 billion, according to Reuters, citing people familiar with the matter. The potential bid by the consortium, which would include China's Alibaba Group and Japan's Softbank Corp , has not yet been finalized. Alibaba, whose primary interest is in buying back a 40 percent stake owned by Yahoo, is keeping its options open and said it has not decided whether to participate in a bid for all of Yahoo. A bid for Yahoo at more than $20 per share would mean a deal value of about $25 billion based on 1.24 billion shares outstanding, potentially making it the largest leveraged buyout in recent years, according to Reuters.

Exide Technologies (XIDE) stock increased 5.32 percent to $2.77 in after-market trading.

Losers

Semtech Corp. (SMTC) stock fell 4.53 percent to $22.15 in after-market trading. Adjusted profit for the third quarter was $35.04 million or $0.52 per share, up from $30.43 million or $0.47 per share last year. Sales rose marginally to $123.94 million from $123.13 million. Analysts had expected profit of $0.46 per share on revenue of $123.03 million. Looking ahead into the fourth quarter, the company expects adjusted earnings of $0.27 to $0.33 per share and sales of $102 million to $108 million, while Wall Street predicts profit of $0.43 per share on revenue of $117.71 million. The company also said its board of directors approved increasing the existing stock repurchase authorization by $50 million. Prior to the raise, the company had $20 million balance in the authorization implemented in March 2008 and amended in August 2011.

Sonus Networks Inc. (SONS) stock declined 4.10 percent to $2.50 in after-market trading. The shares closed Wednesday's regular trading up 5.67 percent at $2.61.

Digital Generation Inc. (DGIT) stock decreased 4.06 percent to $11.59 in after-market trading. The shares closed down 0.85 percent at $11.60 on Wednesday.

Prospect Capital Corp. (PSEC) stock declined 3.77 percent to $8.93 in after-market trading. The shares closed Wednesday's regular trading up 3.11 percent at $9.28.

Connecticut Water Service Inc. (CTWS) stock decreased 3.65 percent to $28 in after-market trading. The shares closed up 5.03 percent at $29 on Wednesday.