Merrill Lynch Securities Co. on Saturday became...

Merrill Lynch Securities Co. on Saturday became the first of six U.S. and British firms scheduled to begin trading on the Tokyo Stock Exchange, ending a 36-year-old monopoly by Japanese companies over the world’s second-largest stock exchange . . . Litton Microwave Cooking Products, a division of Litton Industries, will move its operations from Plymouth, Minn., to Memphis, Tenn., transferring about 70 employees and laying off 355 . . . Boeing Co. announced the completion of its previously reported purchase of De Havilland Aircraft of Canada from the Canadian government . . . Varian Associates said it is reducing the work force of its microwave tube division in Palo Alto by 6%, or about 100 employees . . . Dart & Kraft reported the completion of the sale of its Kitchenaid operations to Whirlpool for $150 million in cash, subject to post-closing audit adjustments.