On Assignment released first-quarter results that sent its stock up 8.5 percent Thursday. The Calabasas staffing company reported net income of $22.4 million (42 cents a share) for the quarter ended March 31, compared to net income of $17.4 million (33 cents) for the same quarter a year ago. Revenue climbed 7.6 percent to $627 million. “A renewed focus by customers on work being performed by domestic labor and the continued adoption of our delivery/development model has permitted us to once again report solid results,” Chief Executive Peter Dameris said in a statement. “As we look forward, economic and legislative factors remain positive and we continue to invest in and alter our divisions’ operating strategies to deliver higher growth.” On Assignment (ASGN) reported results after market close Wednesday. Shares closed Thursday up $4.18, or 8.5 percent, to $53.67 on the New York Stock Exchange.