Nucleoli, micronucleoli, and nucleolus-like structures in human oocytes at meiotic prophase I studied by the silver-NOR technique

Abstract

Meiotic nuclei preparations obtained from human fetal ovaries were studied with the silver-NOR technique. At leptotene, the NOR’s were located at the periphery of the nucleoli. The mean number of NOR’s per nucleus was 6.4. Moreover, 2–12 micronucleoli, each containing an Ag-positive zone, were observed. At pachytene, each nucleolus was divided into two zones, one of which was Ag-positive. The mean number of Ag-positive zones was 2.1 per nucleus. The subterminal region of the short arm of nucleolar bivalents was in contact with the argyrophilic nucleolar zone. In most cells, micronucleoli were dispersed between the bivalents. A single rounded body which stained heavily with silver was consistently observed. At early diplotene, the NOR’s separated, appearing again as distinct rounded Ag-positive structures embedded in the peripheral part of the nucleoli. The silver-stained round body was still visible. Eight to twelve micronucleoli were observed. At a more advanced stage of diplotene, the number of micronucleoli increased, varying from 20 to 50 per nucleus. These observations suggest that the micronucleoli, already visible at the leptotene stage, are the morphological expression of an early transcription of amplified rDNA. The biological significance of the Ag-positive round body remains obscure, but the consistency of its appearance suggests that it has a specific function somehow related to nucleolar proteins.

Primary and secondary nucleolar organiser regions during spermatogenesis in the genus Pycnogaster

“…Secondary nucleoli can be clearly differentiated from other silver precipitates which have been previously described in the literature such as round bodies, dense bodies, Agtdroplets or micronucleoli (Takanari et aL, 1982;Hartung et a!., 1983;Loidl and Greilhuber, 1983;Gosalvez eta!., 1986). Secondary nucleoli, as in the case of primary ones, are seen attached to precise chromosomal locations and also their meiotic behaviour is similar to that of the standard primary nucleoli although both cycles are out of phase.…”

Development of silver stained structures during spermatogenesis in different genera of Formicidae

“…In them, the original prophasic nucleolus desintegrates but a secondary nucleolar activity begins at diplotene (Loidl & Greilhuber, 1983). However, Gos~dvez et al (1986) have suggested that these Ag-positive structures and others such as the extranucleolar spherule (round body) that Hartung et al (1983) observed in human oocytes or the 'dense bodies' reported in Chinese hamster (Takanari et al, 1982) seem to have a different nature and so, different meiotic behaviour. As mentioned at the beginning of this paper, there are marked modifications in the process of spermatogenesis in ants because the males are haploids.…”

Sequential study of synaptonemal complexes in mouse spermatocytes by light and electron microscopy

“…We have also studied the morphology and evolution of the nucleolar bodies, following the criteria defined by Hartung et al (1983).…”