The top after-market NASDAQ Stock Market gainers are: Polycom, Mentor Graphics, ZST Digital Networks, EZCORP, and Stein Mart. The top after-market NASDAQ Stock Market losers are: Radio One, Asia Entertainment & Resources, Pool Corp., Penn National Gaming, Universal Display, Cymer, and Rambus.

Gainers

Polycom, Inc. (PLCM) stock jumped 8.02 percent to $56.06 in the after-market trading, as its first quarter earnings and revenue exceeded Street view. Adjusted profit was $43 million or 48 cents a share, up from $25 million or 29 cents a share last year. Revenue grew to $344 million from $276 million. Analysts had expected profit of 42 cents a share on revenue of $337.80 million. Polycom attributed the growth to good demand for its video and voice services in main markets such as U.S. and Europe, and robust improvement in emerging markets such as India and China, which rank among the fastest growing economies.

Mentor Graphics Corp. (MENT) stock grew 4.93 percent to $14.90 in the after-market trading.

ZST Digital Networks, Inc. (ZSTN) stock gained 4.10 percent to $2.79 in the after-market trading. The Rosen Law Firm, P.A. said it is investigating potential securities claims against ZST Digital resulting from allegations that the company may have issued materially false financial statements and information to investors. On April 21, a market analyst published a news report revealing a number of red flags of fraud at ZST Digital.

Namely, in connection with the company’s fiscal 2009 and 2008 financial results, the report states that SEC filings report revenues hundreds of times of what is reported to the Chinese regulators and the filings show that the company paid zero tax in China, but reported substantial amounts to the SEC. The report also identifies a number of other allegations indicating that the company has misled investors about its customers. These revelations shocked the market, and caused the price of the company’s stock to fall on April 22.

Separately, the law firm of Dyer & Berens LLP said it has initiated its own investigation concerning losses suffered by certain ZST Digital investors. On April 21, a market analyst published a news report highlighting what he contended were numerous red flags, questionable business claims and “compelling evidence of fraud” at the company. The analyst concluded: I believe that ZST Digital Networks … provided false representation of its business relations and reported substantially exaggerated revenue and income to [the] SEC. On these claims, the company’s stock price plummeted nearly 40 percent on unusually high volume.

EZCORP Inc. (EZPW) stock increased 3.83 percent to $31.15 in the after-market trading, as its second quarter earnings and revenue exceeded Street view. Profit was $31.8 million or 63 cents a share, up from $23.8 million or 48 cents a share last year. Revenue rose to $213.2 million from $176.6 million. Analysts had expected profit of 57 cents a share on revenue of $199.67 million.

EZCORP raised its fiscal 2011 adjusted earnings guidance to $2.55 a share from previous forecast of $2.40 a share, while Street predict $2.42 a share. The company said the new guidance includes the acquisition of the Cash Converters Ltd.'s franchise rights in Canada which closed on April 8th and the acquisition of the 15 Mister Money stores expected to close in early May. Ezcorp also said it plans to purchase 30 percent of Cash Converters' shares it does not already own for about $70 million, upping its stake to 53 percent. The transaction is expected to close in the fourth quarter.

Stein Mart Inc. (SMRT) stock rose 2.77 percent to $10.77 in the after-market trading.

Losers

Radio One Inc. (ROIAK) stock plunged 19.26 percent to $2.18 in the after-market trading.

Asia Entertainment & Resources Ltd. (AERL) stock fell 12.30 percent to $7.20 in the after-market trading.

Pool Corp. (POOL) stock tumbled 6.60 percent to $37.34 in the after-market trading. Loss for the first quarter narrowed to $638,000 or 1 cent a share from $6.11 million or 12 cents a share last year. Sales grew to $312.9 million from $269.8 million. Analysts had expected a loss of 8 cents a share on revenue of $286.83 million. The company said the sales growth reflects favorable weather conditions throughout most southern markets, continued market share gains and somewhat higher consumer discretionary expenditures as a result of improved economic conditions compared last year.

The company raised its fiscal 2011 earnings guidance to range of $1.35 to $1.45 a share from previous forecast of $1.27 to $1.35 a share, while Street analysts predict $1.33 a share. We anticipate more modest sales growth for the remainder of 2011. Nonetheless, we are making good progress executing on every facet of our business and have plenty of momentum on our side as we enter the heart of the season. Based on our sales expectations for the full year and our ability to leverage our infrastructure, we expect to realize high profit growth rates with a contribution margin of about 20 percent, said Manuel Perez de la Mesa, Chief Executive Officer of Pool Corp.

Penn National Gaming Inc. (PENN) stock tumbled 6.60 percent to $37.34 in the after-market trading.

Universal Display Corp. (PANL) stock slid 6.39 percent to $53.60 in the after-market trading. The company announced advances in the performance of its UniversalP2OLED solution-processible, phosphorescent OLED material systems for use with solution-based manufacturing processes. OLED manufacturers are evaluating manufacturing techniques, like ink-jet printing, as additional paths for the cost-effective production of large-area OLED displays and lighting panels. These developments were announced at the International Display Manufacturing Conference (IDMC 2011), held April 18 to 21 at the Taipei International Convention Center in Taipei, Taiwan.

Separately, Plextronics said its Plexcore OC NQ ink has been integrated into Universal Display Corp.'s P2OLED solution-processed, phosphorescent OLED technology to assist in achieving lower operating voltage and longer lifetime in test devices.

Cymer Inc. (CYMI) stock declined 5.99 percent to $49.25 in the after-market trading, despite its better-than-expected first quarter results. Profit was $28.8 million or 94 cents a share, up from $16 million or 53 cents a share. Revenue rose to $154.4 million from $113.8 million. Analysts had expected profit of 81 cents a share on revenue of $150.68 million. The company expects second quarter revenue of about $157 million, while Street predicts $156.60 million.

Rambus Inc. (RMBS) stock decreased 4.90 percent to $19.60 in the after-market trading, as it posted a loss for the first quarter. Loss was $4.2 million or $0.04 a share, compared to a profit of $150.9 million or $1.28 a share last year. Adjusted earnings fell to $10.2 million or $0.09 a share from $134.3 million or $1.14 a share last year. Revenue plunged 61 percent to $62.5 million. The year-ago quarter revenues included revenue recognized from agreements signed with Samsung.