A National Gypsum shareholder has filed suit...

A National Gypsum shareholder has filed suit against the Dallas-based company, charging that its proposed $1.1-billion leveraged buy-out is “grossly inadequate and to the detriment of shareholders” . . . Phoenix-based United Bancorp of Arizona said its stockholders have approved the previously reported acquisition of the firm by Union Bancorp of Los Angeles for about $335 million . . . The St. Louis Post-Dispatch reported that Trans World Airlines has reached an agreement with the Air Line Pilots Assn. under which the pilots will make concessions worth about $100 million in 1986 . . . Monsanto said that 2,340 of its U.S. salaried employees elected to take early retirement under a special incentive program announced in October . . . National Medical Enterprises reported that Fairview Community Hospitals’ board of trustees has approved a joint-venture plan to construct a 100-unit retirement complex in Burnsville, Minn. . . . Westates Airlines has halted operations at the Sonoma County Airport after a five-month attempt at daily passenger flights to and from Los Angeles.