title: Further ultrastructural studies on lymphocytic micronuclei.
abstract: The ultrastructural changes of ring-shaped nucleoli in human blood lymphocytes produced with actinomycin D were compared with naturally occurring modification of ring-shaped nucleoli and micronucleoli in mouse thymic lymphocytic. Similarly to those in other nucleoli, these changes were characterized by the segregation of nucleolar components, appearance of very dense granular and fibrillar components, formation of dense plaques as well as dense nucleolar caps and nucleolar fragmentation. In addition, some of the observed changes were specific for the ring-shaped nucleoli i. e. formation of horse shoe-like and beaded nucleoli with the segregation of RNP components in the nucleolar peripheral ring. Some of the nucleolar changes produced with actinomycin D were also similar to the naturally occurring ultrastructural characteristics of micronucleoli in small mouse thymic lymphocytes.
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000187:drug effects / Q000648:ultrastructure*; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000648:ultrastructure; D003609:Dactinomycin / Q000494:pharmacology; D003852:Deoxyribonucleoproteins / Q000378:metabolism; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000648:ultrastructure*; D051379:Mice; D008805:Mice, Inbred A; D008854:Microscopy, Electron; D009697:Nucleolus Organizer Region / Q000187:drug effects / Q000648:ultrastructure*; D012261:Ribonucleoproteins / Q000378:metabolism
chemical_list: D003852:Deoxyribonucleoproteins; D012261:Ribonucleoproteins; D003609:Dactinomycin