UnitedHealth Group (NYSE: UNH) is still in acquisition mode. Two weeks ago its OptumRx subsidiary announced a $1.0 billion deal for pharmacy benefits manager Catamaran Corp. (NASDAQ: CTRX). Last week, another subsidiary, Optum, reached a deal for MedExpress, a privately held chain of full-service neighborhood medical centers in 11 states. Financial terms were not disclosed, but MedExpress plans to open another 25 to 30 centers in 2015. Optum plans to integrate its care management and clinical programs with MedExpress’ services.