Updated from 4:05 p.m. EDTWheeling-Pittsburgh ( WPSC) was higher after raising its second-quarter operating income guidance to about $19 million, roughly $8 million above its previous forecast. The steel company attributed the improved forecast to strong revenue resulting from increased selling prices and lower-than-expected costs. The company expects to announce its second quarter results on Aug. 8. Shares gained $2.14, or 10.8%, to $21.97. Ballard Power Systems ( BLDP) gained after the Canadian fuel-cell company narrowed its second-quarter loss. Revenue totaled $15.1 million, up from $9 million a year ago. The company posted a loss of $17.3 million, or 15 cents a share, compared with a loss of $29.5 million, or 24 cents a share, a year ago. Analysts were expecting a loss of 16 cents a share on sales of $14 million. Shares gained 41 cents, or 7.3%, to $6. Buffalo Wild Wings ( BWLD) stumbled as the restaurant operator offered disappointing third-quarter earnings guidance. In the second quarter, the company earned $2.4 million, or 28 cents a share, compared with $1.9 million, or 22 cents a share, a year ago. Revenue totaled $62.2 million, up 29% from a year ago. Analysts were looking for earnings of 28 cents a share on $59.9 million in revenue. Looking ahead, Buffalo Wild Wings said it anticipated third-quarter revenue of about $65 million to $66 million, with earnings ranging from 28 cents to 31 cents. Wall Street is looking for earnings of 32 cents on revenue of $63.5 million. Shares traded down $4.43, or 11.4%, to $34.57. Taser International's ( TASR) shares slid after the maker of stun guns missed analysts' expectations. Revenue increased 23% to $16.2 million. The company earned $1.5 million, or 2 cents a share, compared with $497,117, or 1 cent a share, a year ago. Wall Street was looking for earnings of 3 cents a share on revenue of $16.1 million. Shares fell $1.20, or 14.1%, to $7.30.