O'Sullivan Corp., a low-profile manufacturing company based in Winchester, Va., became the region's highest-profit stock last week after it accepted a $191 million buyout offer from Geon Co. of Cleveland.

O'Sullivan makes the plastics used in car interiors, turning out miles of vinyl that cover dashboards and door panels of cars made by Ford Motor Co., General Motors Corp. and some of their competitors. Geon, which calls itself the world's largest maker of plastic compounds, is moving up the supply chain by acquiring companies that turn its raw plastics into the higher-value semi-finished sheet goods.

Geon agreed to pay O'Sullivan $12.25 per share, instantly boosting the price of O'Sullivan stock from less than $9 to $12.06 1/4.

The unexpected awakening of the sleepy O'Sullivan stock and gains by several other stocks that ordinarily don't do much helped push up The Washington Post-Bloomberg regional stock index by 2 1/2 points, its biggest one-week gain in several months. The index represents stocks of more than 220 public companies in the District, Maryland and Virginia.

Shares of UOL Publishing Inc., a McLean company that teaches classes over the Internet, climbed more than $1 after the firm announced two contracts for employee-training services.

Primus Telecommunications Group Inc., also of McLean, issued a series of announcements that lifted its stock by nearly $5. The big news was that Primus, an international telephone, data and Internet service, expects to reach $1 billion in revenue this year, a year ahead of schedule. Two recent acquisitions in Canada helped speed revenue growth.

On the downside, shares of Metro Information Services Inc., a Virginia Beach computer consulting firm, dropped more than $4.50 after analysts from two firms cut their ratings on the company's stock.