A 16-month-old baby boy remained in critical condition at UCLA Medical Center as doctors searched for a donor liver that he needs as a transplant to stay alive. Marcus Serna's ordeal began when he contracted non-infectious hepatitis five weeks ago, according to his mother, Martha Serna of Los Angeles. The baby was transferred Thursday from the Kaiser Medical Center in Los Angeles to the pediatric intensive-care unit at UCLA, and a nationwide computer-assisted search for a donor organ of the right size and type began. The baby's family, meanwhile, has maintained a vigil at the hospital, hoping a donor can be found before it is too late. "We're still hoping and praying," Serna said, "but it's getting up against time. We'd appreciate prayer."