title: Tissue and sex differences in the expression of nucleoli in mouse somatic cells.
abstract: In Mus musculus, the nucleolus organizer regions (NORs), or sites of ribosomal RNA-encoding genes, map at three chromosomal pairs. A silver procedure was modified to stain nucleoli in interphasic somatic cells of mice. The number of nucleoli per cell nucleus was determined in squashed cells of kidney, liver and pancreas obtained from male and female mice. In liver and pancreas cells the average number of nucleoli per cell was 4.84 and 4.66, respectively, and only 2.83 in kidney cells (p < 0.001). Less than 8% of pancreas cells and about 15% of liver cells contained more than 6 nucleoli per cell, which was the maximum expected number. In addition, the number of nucleoli per cell was significatively different (p < 0.01) when male and female liver or pancreas cells (not kidney cells) were compared. In both cases, female cells presented more nucleoli than the respective male cells. Assuming that the available NORs are the same, the variable number of nucleoli in the examined cell types would be the consequence of a tissue specific NOR regulation. The apparent influence of sex on this regulation is noted.
authors.affiliation: Department of Cell Biology and Genetics, Faculty of Medicine, University of Chile, Santiago.
authors.forename: S
authors.initials: S
authors.lastname: Berríos
authors.forename: J
authors.initials: J
authors.lastname: Koifman
authors.forename: R
authors.initials: R
authors.lastname: Fernández-Donoso
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000502:physiology*; D002874:Chromosome Mapping; D005260:Female; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D009697:Nucleolus Organizer Region / Q000502:physiology*; D009928:Organ Specificity / Q000502:physiology; D012727:Sex Characteristics; D016622:Silver Staining