C-Banding studies on australian hylid frogs: secondary constriction structure and the concept of euchromatin transformation

King, Max

doi:10.1007/bf00286300

Cited by 153 publications

(134 citation statements)

References 28 publications

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“…The fact that this phenomenon has been observed exclusively in lampbrush chromosomes of amphibian oocytes seems to preserve the traditionally accepted hypothesis that silver specifically stains NOR sites in mammalian mitotic chromosomes (see King, 1980), but our finding that not only NORs but also heterochromatic blocks in E. algirus are silver stainable refutes this assumption.…”

Section: Discussionsupporting

confidence: 86%

Cytogenetic peculiarities in the Algerian hedgehog: silver stains not only NORs but also heterochromatic blocks

et al. 1995

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Hedgehogs belong to one of the several mammalian taxa in which karyotype differences are based on variations in heterochromatin content. Furthermore, the number and location of nucleolar organizer regions (NORs) can also vary widely. In the present study these cytogenetic features were investigated in the Algerian hedgehog, Erinaceus (Aethechinus) algirus. The heterochromatin and NOR distribution patterns in the karyotype of this species are new among hedgehogs, whereas the euchromatic regions, including their G-band pattern, are similar to those reported by others. In addition, silver staining revealed a cytogenetic feature exclusive to the heterochromatic blocks of E. algirus: their silver staining with standard cytogenetic procedures. Because no similar phenomenon has been described previously in a mammalian species, several hypotheses about the significance and specificity of silver staining to NOR sites are discussed. Finally, the existence of different types of heterochromatin in the species analysed here, lead us to propose that what hedgehogs have inherited from their common ancestor is a mechanism which permits the accumulation of heterochromatin on specific chromosomes, rather than the heterochromatin itself.

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Section: Discussionsupporting

confidence: 86%

Cytogenetic peculiarities in the Algerian hedgehog: silver stains not only NORs but also heterochromatic blocks

et al. 1995

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“…Thus, this NOR could be considered as a strictly latent NOR in P. cucullata similar to those described by King (1980) rDNA, they could also be considered as latent NORs. However, these sites coincide with some telomeric regions and it may be argued that the rDNA probe cross-hybridize with (G+C) sequences as those demonstrated in the telomeres of many species of eukaryotes (Allshire et a!., 1989).…”

Section: Discussionsupporting

confidence: 61%

Latent NORs in the species Pycnogaster cucullata (Orthoptera)

et al. 1990

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The chromosomal location of the ribosomal cistrons 18 + 26S and 5S has been determined in spermatocytes of two cytological races of Pycnogaster cucullata by in situ hybridization using molecular probes from both types of rDNA. A comparative analysis with previous results suggested the existence of more 18+ 26S rDNA sites than active NORs as shown by silver impregnation, but 58 rDNA sites are outside the NORs. Thus, different categories of latent NORs have been shown in this specialised cell type which are discussed in relation to the evolutionary process of differentiation in this species.

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“…On the other hand, there are several cases in amphibians in which secondary constrictions of variable appearance are frequently found which cannot be stained by silver (King, 1980). As King noted, these variable constrictions are presumably analogous to the cold-induced despiralised constrictions of Rudak and Callan (1976).…”

Section: Discussionmentioning

confidence: 97%

A study of the Ag-staining significance in mitotic NOR's

1988

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The biological significance of nucleoli and mitotic Ag-staining NOR's has been the cause of controversy for several years. Whereas several authors state or assume a direct correlation between transcriptional activity and Ag-staining, others deny this hypothesis or claim a correlation between Ag-staining and decondensation of the NOR chromatin. Our results show that a decondensed state of the NOR chromatin is necessary but not sufficient to permit silver impregnation, allowing us to conclude that transcriptional NOR activity in the previous interphase is additionally required for silver staining.

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C-Banding studies on australian hylid frogs: secondary constriction structure and the concept of euchromatin transformation

Cited by 153 publications

References 28 publications

Cytogenetic peculiarities in the Algerian hedgehog: silver stains not only NORs but also heterochromatic blocks

Cytogenetic peculiarities in the Algerian hedgehog: silver stains not only NORs but also heterochromatic blocks

Latent NORs in the species Pycnogaster cucullata (Orthoptera)

A study of the Ag-staining significance in mitotic NOR's

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