An investment group that includes Mesa Asset...

An investment group that includes Mesa Asset Co., a unit of Mesa Petroleum, reported in an SEC filing that it has lowered its stake in Unocal to 11.6% . . . Horizon Air, Seattle, said it will be deferring payment of its current quarterly dividend on its cumulative convertible exchangeable preferred stock, pending an amendment to its articles of incorporation . . . Short interest on the New York Stock Exchange rose by 24.6 million shares in the month ended March 14 . . . Nynex Corp. said it has declared a 2-for-1 stock split and raised its quarterly dividend on current shares to $1.74 from $1.60, both payable May 1 to shareholders of record March 31.