Transitional Hospitals Corp. is a target of a Justice Department investigation into possible Medicare fraud involving laboratory tests performed under a partnership between Damon Corp. and a dialysis unit once owned by Transitional, according to a company statement. . . . Florida’s $2-billion college tuition prepayment trust fund will divest tobacco holdings from its investment portfolio. The fund holds $12.8 million of tobacco stock and corporate notes, accounting for less than 1% of its total value. Of that, $11.5 million is in Philip Morris Cos. and $1.3 million is in American Brands Inc. . . . American Express Co. and Microsoft Corp. unveiled an online travel-reservations system aimed at corporate travelers.