Political extremist Lyndon H. LaRouche Jr. has been moved to the Federal Medical Center in Rochester, Minn., to complete a 15-year sentence for mail fraud and conspiracy. LaRouche, 66, will be a resident of the medical-surgical unit. That usually is reserved for medical inmates, but more than half those at the medical center are inmates who have no health problems. Medical center officials said they could not comment on whether LaRouche was in Rochester for treatment. Daryl Kosiak, public information officer at the medical center, said inmates without health problems work at the prison in such areas as maintenance and food service.