Cord Blood Stem Cell TransplantationFetal BloodUmbilical CordHematopoietic Stem Cell TransplantationTransplantation ChimeraTransplantation, HomologousGraft vs Host DiseaseTransplantation ConditioningHematologic NeoplasmsHistocompatibility TestingTissue DonorsGraft SurvivalHematopoietic Stem CellsBlood BanksAntigens, CD34Spinal CordBone Marrow TransplantationTreatment OutcomeInfant, NewbornMice, SCIDUmbilical VeinsUmbilical ArteriesStem Cell TransplantationMice, Inbred NODPregnancySpinal Cord InjuriesCells, CulturedBlood CellsTransplantation, HeterologousCell DifferentiationFlow CytometryWhole-Body Irradiation