title: Nucleologenesis in Trypanosoma cruzi.
abstract: Nucleolar assembly is a cellular event that requires the synthesis and processing of ribosomal RNA, in addition to the participation of pre-nucleolar bodies (PNBs) at the end of mitosis. In mammals and plants, nucleolar biogenesis has been described in detail, but in unicellular eukaryotes it is a poorly understood process. In this study, we used light and electron microscopy cytochemical techniques to investigate the distribution of nucleolar components in the pathway of nucleolus rebuilding during closed cell division in epimastigotes of Trypanosoma cruzi, the etiologic agent of American trypanosomiasis. Silver impregnation specific for nucleolar organizer regions and an ethylenediaminetetraacetic acid regressive procedure to preferentially stain ribonucleoprotein revealed the conservation and dispersion of nucleolar material throughout the nucleoplasm during cell division. Furthermore, at the end of mitosis, the argyrophilic proteins were concentrated in the nucleolar organizer region. Unexpectedly, accumulation of nucleolar material in the form of PNBs was not visualized. We suggest that formation of the nucleolus in epimastigotes of T. cruzi occurs by a process that does not require the concentration of nucleolar material within intermediate nuclear bodies such as mammalian and plant PNBs.
authors.affiliation: 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México.
authors.forename: Tomás
authors.initials: T
authors.lastname: Nepomuceno-Mejía
authors.affiliation: 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México.
authors.forename: Reyna
authors.initials: R
authors.lastname: Lara-Martínez
authors.affiliation: 2Department of Molecular Biology and Biotechnology,Biomedical Research Institute,National Autonomous University of Mexico,México Cd. Mx. 04510,México.
authors.forename: Roberto
authors.initials: R
authors.lastname: Hernández
authors.affiliation: 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México.
authors.forename: María de Lourdes
authors.initials: Mde L
authors.lastname: Segura-Valdez
authors.affiliation: 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México.
authors.forename: Luis F
authors.initials: LF
authors.lastname: Jiménez-García
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000502:physiology; D002467:Cell Nucleus / Q000502:physiology*; D008938:Mitosis; D012335:RNA, Ribosomal / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000166:cytology* / Q000502:physiology*
chemical_list: D012335:RNA, Ribosomal
keywords: Trypanosoma cruzi; closed mitosis; nucleolar assembly; nucleolus; pre-nucleolar bodies