Northwest Airlines has arranged a $500-million loan with 10 Japanese banks and a French bank to help finance its acquisition of Republic Airlines, according to Northwest officials . . . Coldwell Banker Institutional Real Estate Services reported that it will open its first East Coast office on June 1 in New York City . . . An underwriting group led by BankAmerica Capital Markets Group won a competitive bid for $21.2 million of certificates of participation bonds issued by the regents of the University of California . . . RB Industries reported that an agreement in principle has been reached to sell its five RB Furniture stores in Dallas to Daniel P. Selznick of San Diego for undisclosed terms . . . Members of the Communications Workers of America in secret ballot elections across the country voted overwhelmingly to authorize a strike against AT&T if an agreement on a new contract is not reached by May 31 . . . Harrah's Hotels & Casinos will lay off about 180 employees and transfer another 70 in all levels as part of a major staff reduction, the company said.