Among the companies with shares expected to actively trade in Wednesday's session are Synaptics Inc. (SYNA), Mistras Group Inc. (MG) and Ambit Biosciences Corp. (AMBI).

Touchscreen-technology company Synaptics raised its fourth-quarter sales guidance, citing higher-than-expected revenue from mobile products. Shares climbed 13% to $40.51 premarket.

Mistras cut its earnings outlook for the full fiscal year amid weaker-than-expected demand. Shares of the infrastructure-testing company fell 13% to $17.69 in premarket trading.

Ambit Biosciences said based on positive data from the Phase 2 ACE study of quizartinib for patients with relapsed or refractory acute myeloid leukemia, as well as ongoing discussions with the Food and Drug Administration, the company is planning to initiate a Phase 3 clinical trial in early 2014. Shares rose 10% to $7.50 in light premarket trading.

 
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AeroVironment Inc. (AVAV) swung to a fiscal fourth-quarter loss as the company reported much lower revenue from drones. However, its per-share loss of four cents beat analysts' expectations.

Apogee Enterprises Inc.'s (APOG) fiscal first-quarter earnings surged as the industrial-glass manufacturer continues to benefit from a recovery in the U.S. commercial-construction market.

Apollo Group Inc.'s (APOL) fiscal third-quarter profit shrank 40% as the for-profit education company faced weaker enrollment and restructuring costs. But shares rose 2.6% after hours to $19.88 as the company boosted its full-year income expectations.

BlueLinx Holdings Inc. (BXC) has begun exploring strategic options for five of its distribution centers that includes possible sales or closures, as part of a restructuring plan that also will involve a realignment of its headquarters resources.

Cinedigm Digital Cinema Corp. (CIDM) said it plans to offer shares of its Class A stock. The digital-content distributor didn't say how many shares it plans to sell. The company had 48.4 million shares outstanding as of June 11.

Pawn-store operator First Cash Financial Services Inc. (FCFS) cut its full-year outlook and also offered second-quarter guidance below analyst expectations, pointing to continued negative volatility in the price of gold and the Mexican peso.

Home BancShares Inc. (HOMB) and Liberty Bancshares Inc. have agreed to merge in a $280 million cash and stock deal, a move that significantly increases Home BancShares's deposit-market share in Arkansas.

Las Vegas Sands Corp. (LVS) said Chief Financial Officer Kenneth J. Kay will be stepping down effective July 31, but will continue to aid the company in a six-month transition.

Moody's Investors Service lifted the ratings outlook for Mattress Firm Holding Corp. (MFRM) to positive from stable, on the expectation that the bedding retailer's operating performance will likely continue to improve despite macroeconomic uncertainty.

Standard & Poor's Ratings Services lowered its rating on Quicksilver Resources Inc. (KWK) further into junk territory, saying it doesn't believe the oil-and-gas explorer will be able to remedy its unsustainable leverage.

Parexel International Corp. (PRXL) offered revenue guidance for fiscal 2014 that was below analysts' estimates, while affirming its prior view for the current quarter and current fiscal year.

SandRidge Energy Inc. (SD) has appointed Eddie LeBlanc as its new chief financial officer, succeeding James Bennett, who was recently named the oil-and-gas producer's chief executive.

Smith & Wesson Holding Corp.'s (SWHC) fiscal fourth-quarter earnings more than doubled amid continued strong demand that resulted in double digit sales growth and higher margins.

Synnex Corp.'s (SNX) fiscal second-quarter earnings fell 10% as higher costs and expenses masked increased revenue at the information-technology distributor.

Moody's Investors Service raised its outlook on United Rentals Inc. (URI), as it expects the equipment-rental company's operating performance to continue to improve.

Write to Anna Prior at anna.prior@dowjones.com

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