Here are the biggest percentage gainers and losers in pre-market trading among companies with a market cap between $50 million and $750 million:

Biggest percentage gainers:

• Aceto Corp. (Nasdaq:ACET), up 13% after the distributor of chemically derived pharmaceuticals, biopharmaceuticals, specialty chemicals and crop protection products posted fiscal third-quarter earnings Friday morning that trumped the consensus on Wall Street and posted sales that increased 29.5% from the year-ago quarter.
• Obagi Medical Products, Inc. (Nasdaq:OMPI), up 9%.
• True Religion Apparel, Inc. (Nasdaq:TRLG), up 8%, after first-quarter results trumped the consensus on Wall Street and the designer jean manufacturer raised its 2008 guidance.

Biggest percentage losers:

• NGAS Resources, Inc. (Nasdaq:NGAS), down 8% after the natural gas exploration and production company reported first-quarter revenues after Thursday’s close that fell below the Street’s view.
• Vision-Sciences Inc. (Nasdaq:VSCI), down 6%.
• Exactech Inc. (Nasdaq:EXAC), down 5% after the producer of bone and joint restoration products said this morning that it has gone back to the equity markets and sold 877,391 shares of its stock at $23.00 per share for gross proceeds of approximately $20.2 million.

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