The fine structure of a nucleolar constituent

Recher, L.; Whitescarver, J.; Briggs, L.

doi:10.1016/s0022-5320(69)80052-3

Cited by 112 publications

(22 citation statements)

References 16 publications

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“…Aside from the ribosomal genes, one of the major components of the fibrillar center is an argyrophilic protein (16,(30)(31)(32).…”

Section: Resultsmentioning

confidence: 99%

Association of ribosomal genes in the fibrillar center of the nucleolus: a factor influencing translocation and nondisjunction in the human meiotic oocyte.

Mirre¹,

Hartung²,

Stahl³

1980

Proc. Natl. Acad. Sci. U.S.A.

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Prophase I of meiosis was studied in the human oocyte obtained from 16-to 24-week-old fetuses. Electron microscopy and silver staining showed that, at pachytene, the ribosomal genes belonging to several chromosomes are gathered in the same nucleolar fibrillar center, where they are embedded in an argyrophilic protein. The nucleolus showed spontaneous segregation of its components due to temporary inactivation of the ribosomal genes. The fibrillar center, separated from the other nucleolar components, was penetrated at midpachytene by chromatin fibers containing rDNA emanating from one to three nucleolar bivalents. Thus, the ribosomal genes from 4-12 chromatids are temporarily juxtaposed inside the same structure. Such a structural arrangement is completely different from that observed in the pachytene-stage mouse oocyte, where two independent and active nucleoli, each displaying its own fibrillar center, were formed on the bivalents containing paired ribosomal genes. These different structural patterns' are correlated with the high frequency of nondisjunction in the human oocyte and the relative infrequency of such in the mouse oocyte. The pattern observed in the human oocyte may be a cause of translocations.Chromosomal anomalies due to meiotic nondisjunction are the most frequent cause of human spontaneous abortions (1-4). In contrast, aneuploidy is seldom observed in mouse embryos (5). This difference is explained by the very low incidence (<1.0%) of nondisjunction during the first meiotic division of mouse oocytes (6). Chromosomes containing a nucleolus organizer are involved in about 40% of human lethal trisomies (7). In Down syndrome, the extra chromosome 21 originates, in most cases, as a result of nondisjunction during the first meiotic division of the oocyte (8-10). These data suggest that, at prophase I of human meiosis, a structural arrangement may exist favoring the failure of disjunction of chromosome 21 and other nucleolus-organizer-containing chromosomes. The nucleolar association of several bivalents at pachytene has been described previously (11), but the techniques used gave no information about the part of the nucleolus involved in the association and the possible entanglement of the chromosomal and nucleolar structures. This paper describes a comparative study of the behavior of nucleolus-organizer-containing chromosomes at prophase I of meiosis in the human and the mouse oocyte that was made in an attempt to elucidate the nature of these structural arrangements.MATERIALS AND METHODS Materials. Eight human fetal ovaries taken at 16-24 weeks of pregnancy and eight ovaries from Swiss OF1 mouse embryos taken at the 18th day of pregnancy were used.Silver Staining of the Nucleolar Organizer Region. After isolation and spreading (12), the human germ cells were stained (13) by treatment with 50% silver nitrate solution at 60-700C for 6 min followed by treatment with ammoniacal silver/3% neutralized formalin, pH 5-6. Electron Microscopy. The ovaries were cut into 1-mm3 pieces and fixed by ...

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“…Aside from the ribosomal genes, one of the major components of the fibrillar center is an argyrophilic protein (16,(30)(31)(32).…”

Section: Resultsmentioning

confidence: 99%

Association of ribosomal genes in the fibrillar center of the nucleolus: a factor influencing translocation and nondisjunction in the human meiotic oocyte.

Mirre¹,

Hartung²,

Stahl³

1980

Proc. Natl. Acad. Sci. U.S.A.

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“…Although the morphological features of nucleoli can vary widely in different cell types and in different metabolic states, three major components are usually distinguished (1): the granular component, the dense fibrillar component, and the "fibrillar centers." The latter usually appear as small islets of rounded structures of relatively low contrast embedded in the dense fibrillar component (1,3,4).…”

mentioning

confidence: 99%

Localization of RNA polymerase I in interphase cells and mitotic chromosomes by light and electron microscopic immunocytochemistry.

Scheer¹,

Rose²

1984

Proc. Natl. Acad. Sci. U.S.A.

299

164

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Rabbit antibodies to RNA polymerase I from a rat hepatoma have been used to localize the enzyme in a variety of cells at the light and electron microscopic level. In interphase cells the immunofluorescence pattern indicated that polymerase I is contained exclusively within the nucleolus. That this fluorescence, which appeared punctated rather than uniform, represented transcriptional complexes of RNA polymerase I and rRNA genes was suggested by the observation that it was enhanced in regenerating liver and in a hepatoma and was markedly diminished in cells treated with actinomycin D. Electron microscopic immunolocalization using gold-coupled second antibodies showed that transcribed rRNA genes are located in, and probably confined to, the fibrillar centers of the nucleolus. In contrast, the surrounding dense fibrillar component, previously thought to be the site of nascent prerRNA, did not contain detectable amounts of polymerase I. During mitosis, polymerase I molecules were detected by immunofluorescence microscopy at the chromosomal nucleolus organizer region, indicating that a considerable quantity of the enzyme remains bound to the rRNA genes. From this we conclude that rRNA genes loaded with polymerase I molecules are transmitted from one cell generation to the next one and that factors other than the polymerase itself are involved in the modulation of transcription of DNA containing rRNA genes during the cell cycle.

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“…In nucleoli studied through the electron microscopy the presence of ribonucleoproteins (RNPs) with a fibrillar structure, a granular component and an occasional nucleolar vacuole are clearly visualized (Recher et al 1969, Moreno Diaz de la Espina et al . 1980.…”

mentioning

confidence: 99%

Visualization of nucleolar organizing regions in nucleoli of interphase plant cells.

Vieira¹,

Queiroz²,

Viegas³

1990

CYTOLOGIA

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The fine structure of a nucleolar constituent

Cited by 112 publications

References 16 publications

Association of ribosomal genes in the fibrillar center of the nucleolus: a factor influencing translocation and nondisjunction in the human meiotic oocyte.

Association of ribosomal genes in the fibrillar center of the nucleolus: a factor influencing translocation and nondisjunction in the human meiotic oocyte.

Localization of RNA polymerase I in interphase cells and mitotic chromosomes by light and electron microscopic immunocytochemistry.

Visualization of nucleolar organizing regions in nucleoli of interphase plant cells.

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