John K. Castle, president and chief operating...

John K. Castle, president and chief operating officer of Donaldson, Lufkin & Jenrette since 1979, was elected to the additional post of chief executive at the New York-based brokerage firm. He succeeds Richard H. Jenrette, who will remain chairman.

The company recently announced plans to be acquired by New York-based Equitable Life Assurance Society of the United States.