Here are Wednesday’s biggest percentage gainers and losers, along with top volume leaders, among companies with a market cap between $50 million and $750 million:

Biggest percentage gainers:

• BCSB Bankcorp, Inc. (Nasdaq:BCSBD), up 81.3% to $11.35 after the Baltimore-based bank holding company reported net income of $0.1 million for the six months ended March 31, versus a loss of $3.2 million a year earlier. The increase was primarily due to losses sustained in 2007 from the balance sheet restructuring, partially offset by recoveries on dishonored checks.
• China Architectural Engineering, Inc. (AMEX:RCH), up 39.1% to $8.26 after posting a twofold increase in first-quarter profit.
• China Automotive Systems, Inc. (Nasdaq:CAAS), up 25% to $6.85 after the China-based supplier of power steering systems and components announced that its first-quarter profit more than doubled.

Biggest percentage losers:

• Young Innovations, Inc. (Nasdaq:YDNT), down 15.8% to $17.65 despite no significant news.
 • U.S. Shipping Partners L.P. (NYSE:USS), down 14.4% to $7.02 after Moody’s lowered its debt rating on the petroleum and chemical shipper. Along with other debt ratings, Moody’s cut USS Shipping Partners’ corporate family and probability of default ratings to Caa3 from Caa1. USS shares are already down about 45% since Monday after the Edison, N.J.-based firm reported that it swung to a first-quarter loss.
• Community Valley Bancorp (Nasdaq:CVLL), down 10.5% to $9.16 despite no major announcements.

Volume leaders:

• Emcore Corp. (Nasdaq:EMKR), 5.2 million shares traded compared with average of 2.1 million shares.
• China Architectural Engineering, Inc. (AMEX:RCH), 4.8 million shares traded compared with average of 168,700 shares.
• UCBH Holdings, Inc. (Nasdaq:UCBH), 4.8 million shares traded versus average of 3.4 million shares.