Shares of LaBranche ( LAB) were among the NYSE's losers Friday, tumbling 21% after the specialist trading firm warned of a big second-quarter loss.

The company sees a loss of about $23 million, with an operating loss of about $5 million, or 8 cents a share. LaBranche also said its loss would include noncash costs of about $17 million related to a decline in the estimated fair value of the restricted shares of NYSE Group ( NYX) that it owns. The company attributed the operating loss to a decline in principal trading revenue in its specialist and market-making business. LaBranche expects to post principal trading revenue of about $20 million, down significantly from the $47 million it posted during the year-earlier quarter. "These lower principal trading results were due to adverse market conditions in May and June 2006," the company said. Shares were trading down $2.65 to $9.79.

3M ( MMM) slid 7% after the consumer and industrial conglomerate warned that second-quarter earnings would miss its previous guidance. The company continues to expect earnings of $1.14 to $1.17 a share, but that now includes one-time gains of 8 cents to 10 cents a share. Without the one-time items, earnings would be below earlier guidance. On the top line, 3M sees revenue of about $5.7 billion. Analysts polled by Thomson First Call project second-quarter earnings of $1.17, excluding the one-time items, and revenue of $5.71 billion. "This second quarter performance was impacted in large part by lower than expected sales volumes and higher than anticipated new capacity start-up costs in the optical systems division, a part of 3M's display and graphics business segment," the company said.

For all of 2006, 3M anticipates earnings of $4.55 to $4.65 a share, including the one-time gains of 8 cents to 10 cents a share. Analysts project earnings of $4.66 a share. Shares were down $5.96 to $75.43.

Shares of RadioShack ( RSH) soared 18% after the company named Julian Day as its new chairman and chief executive. Day, who previously held leadership roles at Kmart, Sears Holdings ( SHLD), and Safeway ( SWY), will replace Claire Babrowski, who had been serving as CEO on an interim basis since February. Shares of the consumer electronics retailer recently changed hands at $16.21, up $2.45.

UAP Holding ( UAPH) slid 10% after the distributor of agricultural products posted its first-quarter results and cut its full-year earnings guidance. For the period ended May 28, the company earned $58.3 million, or $1.11 a share, on revenue of $1.4 billion. The single analyst forecast called for earnings of $1 a share on revenue of $1.45 billion. "This was a challenging quarter but we are pleased with our ability to work with our customers to meet their needs while creating value for our shareholders," UAP said. A year earlier, the company earned $49.4 million, or 94 cents a share, on revenue of $1.36 billion.

UAP Holding projects full-year earnings of $1.25 to $1.40 a share, before items, down from an earlier forecast of $1.40 to $1.50 a share. Three analysts have an average estimate for earnings of $1.47 a share. Shares were down $2.12 to $19.82.

Shares of AmerUs Group ( AMH) rose 6% after the life insurance and annuity products company confirmed that it is in talks to be acquired by British insurance company Aviva. AmerUs, which said there can be no assurance that a transaction would occur, won't provide an update on the discussions until they are concluded. Shares were trading up $3.45 to $65.96.

NYSE volume leaders included Advanced Micro Devices ( AMD) down 47 cents to $23.36; Qwest ( Q), down 37 cents to $7.96; Corning ( GLW), down $1.07 to $22.17; Ford ( F), up 11 cents to $6.70; EMC ( EMC), down 2 cents to $11.05; and Exxon Mobil ( XOM), up 6 cents to $63.53.

Nasdaq volume leaders included Intel ( INTC), down 10 cents to $18.75; Microsoft ( MSFT), down 10 cents to $23.38; Oracle ( ORCL), up 25 cents to $14.75; Sun Microsystems ( SUNW), down 8 cents to $3.92; Cisco Systems ( CSCO), down 19 cents to $19.44; Sirius Satellite Radio ( SIRI), down 13 cents to $4.40; PMC-Sierra ( PMCS), down $1.34 to $7.70; Level 3 Communications ( LVLT), up 12 cents to $4.39; Apple Computer ( AAPL), down 59 cents to $55.18; and JDSU ( JDSU), down 2 cents to $2.35.