 studi nickel carcinogenesi fraction nickel ultracentrifug supernat lung liver dextran gel chromatographi chromatograph fraction perform ultracentrifug supernat homogen rat lung liver column dextran gel sephadex g-100 major proport nickel tissu supernat demonstr firmli bound macromolecular constitu acut chronic inhal carcinogen level nickel carbonyl predomin increas concentr nickel observ macromolecular fraction find consist previou demonstr nickel purifi prepar ribonucl acid rna rat tissu observ increas concentr nickel high-molecular weight rna lung liver inhal nickel carbonyl 