Showing papers on "Nucleolar chromatin published in 1984"
TL;DR: It is concluded that the extent of psoralen-crosslinking in chromatin DNA is diagnostic for the structure of undistorted chromatin, as well as for the chromatin in the non-transcribed spacer of the ribosomal DNA.
110 citations
TL;DR: The use of nucleolar silver staining in plant cells in conditions of impaired transcription, either natural (quiescent cells) or induced (actinomycin D, ethidium bromide and cordycepin treatments), shows that nucleoli with very low transcription rates, compared with controls, contain similar amounts of argyrophilic proteins, as well as the same structural location.
17 citations
TL;DR: It is demonstrated by use of a Feulgen-like ammine-osmium staining procedure that, depending on the state of growth, more or less fibres of decondensed DNA emanating from the intra-nucleolar chromatin ramify and unravel within the central nucleolar core to be transcribed.
Abstract: In embryonic cell-line derivative KCo of Drosophila melanogaster, the nucleolus, like most nucleoli, contains a small proportion of ribosomal DNA (1–2% of the total nucleolar DNA) The ribosomal DNA is virtually the only active gene set in the nucleolus and is found among long stretches of inactive supercoiled heterochromatic segments We have demonstrated by use of a Feulgen-like ammine-osmium staining procedure that, depending on the state of growth, more or less fibres of decondensed DNA emanating from the intra-nucleolar chromatin (which is in continuity with the nucleolus-associated chromatin) ramify and unravel within the central nucleolar core to be transcribed The nucleolus expands or contracts with the variation of activity and could belong to a supramolecular matricial structure such as is shown after extraction of the nuclei After a long period of exposure to high doses of actinomycin D, the central nucleolar core became an homogeneous fibrous structure that could be interpreted as an aggregate of protein skeletal elements The mechanism of repression and derepression of the nucleolar chromatin could thus be explained by a mechanism involving in part a sub-nucleolar structure We propose a schematic organization of the nucleolar chromatin in KCo cells of Drosophila and discuss it in relation with other nucleolar organizations
11 citations
TL;DR: The data presented here suggest that nucleolar-associated chromatin is highly enriched in protein "A", and the regional differentiation in the eukaryotic chromatin, therefore, may involve qualitative changes in the histone composition.
10 citations
TL;DR: The distribution of calcium within the plasmodium is discussed in relation to the assembly of the mitotic spindle and the regulation of cell motility and calcium binding sites along the cytoplasmic surface of the plasma membrane are identified.
Abstract: Plasmodia of the acellular slime mold, Physarum polycephalum, were treated with an osmium tetroxide fixative containing potassium pyroantimonate to precipitate calcium and thereby localize calcium binding sites and sites of increased calcium concentration. Dense calcium pyroantimonate precipitates were detected within the nucleoli. The distribution of these precipitates during interphase and mitosis coincides with the distribution of the unique minichromosomes in Physarum, i.e., the numerous short pieces of extrachromosomal nucleolar chromatin containing segments of amplified DNA coding for ribosomal RNA. Calcium pyroantimonate precipitates were
9 citations