Wisconsin Public Service Corp., Green Bay, hired Northern Trust Global Investments as an S&P 400 index manager running a $25 million portfolio for its $625 million defined benefit plan. The hiring was in conjunction with the termination of an active midcap growth manager for performance reasons, said Jerry Myers, director-trust investments and treasury. The active portfolio totaled $45 million and the remaining $20 million was allocated to existing managers. He would not name the terminated manager. Trustees have yet to determine whether to search for an active manager, but may consider doing so in the future, Mr. Myers said. Becker Burke assisted with the search.