title: Quantitative estimation of nucleolar cistrons (rDNA) in proliferating normal and tumor cells.
abstract: The saturating hybridization levels of DNA with rRNA (hereafter abbreviated as rDNA/DNA) in adult liver, bone marrow, and fetuses in Long-Evans rats were 0.042, 0.036, and 0.029 approximately 0.033%, respectively, showed a lower level in rapidly growing tissues. We consider that the lower rDNA/DNA in rapidly growing tissues might be due to the replication of rDNA in the late S phase, or in other words, to the depression of rDNA/DNA in each S phase. Based on these findings, the relative levels of rDNA per G1 geome were estimated in cells of these normal tissues and 4 diploid tumors by multiplying rDNA/DNA and DNA/genome. By this procedure, rDNA/genome was shown to be constant in normal G1 cells, while a 31 approximately 48% increase was found in the tumor cell genome. Direct measurement of rDNA in synchronized #2 trisomy leukemia cells confirmed the replication of rDNA in the late S phase, with a 21.4% increase of rDNA per G1 genome.
mesh_terms: D000818:Animals; D001853:Bone Marrow; D002417:Cattle; D002453:Cell Cycle; D002466:Cell Nucleolus / Q000032:analysis*; D002478:Cells, Cultured; D002875:Chromosomes / Q000032:analysis; D004247:DNA / Q000378:metabolism*; D004261:DNA Replication; D004273:DNA, Neoplasm / Q000378:metabolism*; D005260:Female; D005333:Fetus; D005796:Genes; D008099:Liver; D008297:Male; D051379:Mice; D009693:Nucleic Acid Hybridization; D012335:RNA, Ribosomal / Q000235:genetics*; D051381:Rats
chemical_list: D004273:DNA, Neoplasm; D012335:RNA, Ribosomal; D004247:DNA