title: [Characteristics of Actinomycin D-induced segregation of a "noncanonical" nucleolus of the sea urchin Paracentrotus lividus].
abstract: The structure of a "noncanonical" nucleolus of vitellogenic oocytes in the sea urchin Paracentrotus lividus was studied using the inhibitor of transcription actinomycin D. In the control cells, the nucleolus consists of two separated structural subdomains: the dense fibrillar-granular peripheral area and the fibrillar central area. The nucleolus did not contain subdomains corresponding to the fibrillar center and dense fibrillar component of "typical" nucleoli. After treatment with actinomycin D, numerous argyrophilic granules appeared in the karyoplasm, the intranucleolar DNA became compact, and the nucleolar material was segregated into two or three separated zones, the residual peripheral area being the densest and largest. Lesser zones had a decreased electron density and contained argyrophilic proteins and, apparently, the nucleolar organizer material. These results suggest that, for normal rRNA expression and processing, the presence of structural subdomains in the nucleolus, such as fibrillar complexes and a dense fibrillar component, is not essential.
authors.affiliation: Belozersky Research Institute of Physicochemical Biology, Moscow State University, Vorob'evy gory, Moscow, 119899 Russia.
authors.forename: E V
authors.initials: EV
authors.lastname: Sheval'
authors.forename: P V
authors.initials: PV
authors.lastname: Gulak
authors.forename: I I
authors.initials: II
authors.lastname: Kireev
authors.forename: E M
authors.initials: EM
authors.lastname: Chudinova
authors.forename: D
authors.initials: D
authors.lastname: Fais
authors.forename: F
authors.initials: F
authors.lastname: Dzhangutstsa
authors.forename: V I
authors.initials: VI
authors.lastname: Poliakov
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000187:drug effects* / Q000648:ultrastructure*; D003609:Dactinomycin / Q000494:pharmacology*; D005260:Female; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects*; D012617:Sea Urchins
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D003609:Dactinomycin
vernacular_title: Osobennosti segregatsii "nekanonicheskogo" iadryshka ootsitov morskogo ezha Paracentrotus lividus, indytsirovannoi deistviem Aktinomitsina D.