INVESTOR FIRMS HAVE 25.5 PCT OF SYMBION <SYMB> A group of affiliated firms led by Warburg, Pincus Capital Co L.P., a New York venture capital and investment partnership, said it has acquired 1,920,527 shares of Symbion Inc, or 25.5 pct of the total outstanding. In a filing with the Securities and Exchange Commission, the Warburg Pincus group said it bought the stake for investment purposes. Although the group said it is considering buying more shares of Symbion, it said it has no plans to seek control of the company.