OHIO MATTRESS <OMT> BUYS SEALY OF MICHIGAN Ohio Mattress Co said that its Ohio-Sealy Mattress Manufacturing Co unit completed its previously announced acquisition of Sealy Mattress Co of Michigan Inc. In addition, the company said Sealy Inc, of which its owns 82 pct, redeemed the outstanding Sealy stock held by Michigan Sealy, thus increasing the company's stake in Sealy to 93 pct.