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Results for “Nucleolus Organizer Region”

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At least 19 recordsLinked to original sources
PubMed1978

Evidence for the inheritance of silver-stained nucleolus organizer regions.

The inheritance of nucleolus organizer regions (NORs) was investigated by examining the degree of silver-staining in individual acrocentric chromosomes in two successive generations. The study was undertaken in six Down's syndrome children and their respective parents. Quinacrine fluorescent polymorphisms were used to identify individual acrocentrics and to determine which of the child's acrocentrics were informative as to parental homologue of origin. Of the 66 acrocentrics in the six children, 31 were informative. The correlation between the degree of silver=staining in the child's chromosomes and the respective parental chromosomes of origin was highly significant (P less than 0.001), with a correlation coefficient of 0.90. The results suggest that the degree of Ag-AS staining is characteristic for a particular chromosome and that this characteristic is an inherited property.

Cell Nucleolus↗
PubMed1998

[Functional morphology of nucleolus organizer regions of chromosomes and nucleoli in human multiple myeloma cell lines. I. Variation of the morphology and silver staining of nucleolus organizer regions of chromosomes in RMPI 8226 and U 266 cell lines with different level of differentiation of during 7 days after cell passage].

The morphology and Ag-staining of nucleoli in human multiple myeloma cell lines RPMI 8226 and U 266, distinguished from each other in the differentiation degree, were quantitatively studied, and the production of immunoglobulins or their fragments by the line cells was evaluated throughout 7 days after cell seeding. The less differentiated cell line RPMI 8226 and the high differentiated cell line U 266 were revealed to differ in both the initial level of immunoglobulin production and dynamics of immunoglobulin accumulation in culture medium. The total number of Ag-stained nucleolar-organizer regions (AgNORs) per nucleus in cells RPMI 8226 was significantly higher than in cells U 266 in all times after seeding of the cells. In both cell lines changes in the quantity and shape of nucleoli and also in the total number of AgNORs per nucleus and pattern of AgNORs distribution within nucleoli correlated with the cell cycle phase. Relationships between morphofunctional changes in nucleoli and the differentiation degree and proliferative activity of the cells, and also between the number of Ag-positive nucleolar-organizing metaphase chromosomes and the functional activity of interphase AgNORs are discussed.

Cell Differentiation↗
PubMed2004

Nucleolus organizing regions and semi-persistent nucleolus during meiosis in Spartocera fusca (Thunberg) (Coreidae, Heteroptera).

The Coreidae are cytogenetically characterized by possessing holokinetic chromosomes and a pre-reductional type of meiosis. The modal diploid chromosome number of the family is 21, with a pair of m chromosomes and an XO/XX sex chromosome determining system. Spartocera fusca presents 2n=23/24=20+2m+XO/20+2m+XX (male/female). Meiosis follows the general pattern described for heteropterans, with a diffuse stage after pachytene and a particular chromosome arrangement at both metaphase plates. S. fusca presents some cytogenetic peculiarities: the X chromosome shows a secondary constriction in a medial position, which is not a nucleolus organizing region. It has been revealed by in situ hybridization with a rDNA probe that the NOR is localized at the telomeric region of one autosomal pair. Furthermore, during the meiosis of three specimens of S. fusca a semi-persistent nucleolus was detected from early meiotic prophase until telophase II; the presence of this semi-persistent nucleolus together with the long diffuse stage detected in the specimens suggest that a continuous biosynthetic activity is required for spermiogenesis. These observations could be related to differences in the environmental, and therefore, physiological conditions of the analyzed individuals.

Animals↗
PubMedDate not supplied

[The functional characteristics of the chromosomal nucleolus organizer regions of patients with endometrial cancer].

The nucleolus organizer region activity and the level of acrocentric chromosome association in cultured peripheral blood lymphocytes was studied in patients with endometrial glandular hyperplasia and endometrial cancer. The number of active nucleolus organizer regions and the frequency of 13 and 21 acrocentric chromosome associations was higher in patients with endometrial cancer.

Adult↗
PubMed1979

Conservation of nucleolus organizer regions during evolution in sheep, goat, cattle and aoudad.

There are ten nucleolus organizer regions (NORs) in domestic sheep (Ovis aries L.). cattle (Bos taurus L.), goat (Capra hircus L.) and aoudad (Ammotragus lervia Blyth) and these are located terminally on chromosomes with homologous (G-banding patterns. The similarity in number of nucleolus organizer regions in these species may indicate that their ribosomal DNA regions are infrequently involved in exchange events which could lead to different numbers of active nucleolus organizer regions. Other possible explanations of the conservation of number of nucleolus organizer regions in these species are discussed. The homology of NOR location in these species supports the idea that the Bovidae karyotype tends to be fairly stable apart from changes due to centric fusion events.

Animals↗
PubMed2001

Ribosomal genes in Coregonid fishes (Coregonus lavaretus, C. albula and C. peled) (Salmonidae): single and multiple nucleolus organizer regions.

Major rDNA loci, i.e. nucleolus-organizing regions (NORs), were assigned using chromomycin-A3 (CMA3) staining followed by sequential silver (Ag) staining and in situ hybridization (ISH) with a rDNA probe to the chromosomes of the European whitefish (Coregonus lavaretus), the peled (Coregonus peled) and the vendace (Coregonus albula), three closely related coregonine salmonid fishes. One pair of NOR-bearing chromosomes was found in the peled karyotype. Multichromosomal, but stable, locations of rDNA sites on three pairs of chromosomes were observed in the European whitefish karyotype. Multichromosomal polymorphic locations, both in site and number, were observed in the karyotype of the vendace. Several Ag-, CMA3- and ISH-positive regions were found which defined up to seven cytotypes of five NOR-bearing chromosomes. All positive Ag-NORs detected corresponded both to rDNA-ISH- and CMA3-positive signals, which suggests extensive structural polymorphism in the locations of rDNA sites. Stable NOR sites were found at the same location on both homologous elements of the chromosome no. 9 in all individuals, while the remaining NORs were quite variable between individuals, and often present in heterozygous condition. The apparently similar and parallel evolutionary rDNA differentiation patterns in the subfamilies Coregoninae and Salmoninae (family Salmonidae) are observed and discussed.

Animals↗
PubMed1994

[Value of nucleolus organizer regions (AgNORs) in dermatologic oncology].

Nucleolus-organizing regions (Ag-NORs) are silver-stained loops of DNA transcribing to ribosomal RNA. Quantitative analysis helps to differentiate normal tissue from malignant tissue and can be used for diagnosis in several kinds of tumours. The analysis of AgNORs can also be used in dermatopathology for diagnostic and prognostic purposes. Apart from skin tumours such as basal, cell carcinomas and squamous cell carcinomas, this technique is of interest principally for melanocytic lesions. Benign naevi can be distinguished from malignant melanomas by simple counting of the AgNOR dots. For the differentiation of dysplastic naevi, Spitz naevi and malignant melanomas, this parameter alone is not sufficient. By combination of several AgNOR parameters (number, size, pattern of dispersal) only, significant differentiation could be achieved. The prognostic value of AgNORs remains to be examined.

Basal Cell Carcinoma↗
PubMed1994

Immunodetection of the ribosomal transcription factor UBF at the nucleolus organizer regions of fish cells.

A human autoimmune serum to nucleolus organizer regions (NORs) has been used to localize these structures at the light microscopic level in carp and trout tissue culture cells. In interphase cells, the immunofluorescence pattern indicates that the NORs autoantigens are contained exclusively within the nucleolus of carp epithelial (EPC) and trout gonad (RTG) cells. This fluorescence is punctuate rather than uniform, and presumably represents transcriptional complexes of ribosomal DNA. During mitosis, the autoantigens are detected by immunofluorescence microscopy at the chromosomal nucleolus organizer regions of condensed chromosomes, indicating that a considerable quantity of the molecule(s) remains bound to the ribosomal RNA genes. The major nucleolus autoantigen, defined in mammals as the upstream ribosomal binding factor (UBF), has been identified on immunoblots as a 90 kDa protein in extracts from fish cell lines and tissues. Thus, NORs appear to function as nucleation centers for ribosomal RNA together with a complex set of well-conserved protein factors, such as UBF. Our results suggest evolutionary conservation from fish to mammals with respect to ribosomal RNA biosynthesis driven by RNA polymerase I.

Animals↗
PubMed1988

Spontaneous in vitro neoplastic evolution of cultured Chinese hamster cells. Nucleolus organizing region activity.

Silver staining to demonstrate active nucleolus organizing regions (NORs) was performed at four different stages of the spontaneous tumorigenic progression in vitro of Chinese hamster WCHE/5 cells. The number of active NORs increased for fully transformed, highly tumorigenic, late passage cells. The increase of NOR material was due to additional NOR-bearing chromosomes or chromosome arms, i.e., trisomy 5, trisomy 8, and the marker chromosome i(3q). Intermediate stages of the neoplastic evolution showed changing patterns of NOR activity, but not an overall increase. We postulate that the increase of active rDNA enhances cell growth and provides undefined selective advantage, and that this supports our previous conclusion that selectable karyotype changes provide competitive advantages rather than being essential for neoplastic evolution in vitro.

Animals↗
PubMed1986

Ectopic nucleolus organizer regions (NORs) in human testicular tumors.

Investigation of nucleolus organizer regions (NORs) in hematopoietic malignancies has indicated that the distribution and rearrangement of these regions may be more important in malignant tissues than is their number. In one of the few studies thus far reported on NORs in human solid tumors, we describe here Ag-NORs in a group of human testicular germ-cell tumors and the corresponding patients. Four of seven malignancies demonstrated consistent ectopic NORs; explanations could include chromosomal rearrangement (insertion?) or derepression of preexisting inactive NORs.

Animals↗
PubMed1981

Familial silver staining patterns of human nucleolus organizer regions (NORs).

The silver staining patterns of the nucleolus organizer regions (NORs), an indication of rDNA transcriptional activity, were studied in metaphases from lymphocyte cultures of 20 karyotypically normal members of three families selected for a large sibling number or a monozygotic twin pair. Quinacrine polymorphic markers and bands were used to identify the acrocentrics and to determine their parental origin. A comparison of the silver staining frequencies among siblings and between parent and child indicated no significant differences for any acrocentric in the twin pairs and significant differences (P less than .05) for only one of the 20 acrocentrics segregating in each of two families. These two acrocentrics had short stalks with very small silver deposits (AgNORs). The mean size of the AgNOR, based on a relative score, was not significantly different (P greater than .05) for each homolog between the twin pair and in approximately 70% of the acrocentrics shared by members of the one family analyzed. The frequency with which a particular chromosome was silver stained demonstrated a significant correlation (r2 = .732) with the size of AgNOR. There was a close correlation (r2 = .609) between stalk length and the size of the AgNOR. We conclude that the frequency of silver staining and the mean size of the AgNOR are characteristics inherent in a particular chromosome carried from one generation to the next.

Cells, Cultured↗
PubMed1976

Detection of nucleolus organizer regions in chromosomes of human, chimpanzee, gorilla, orangutan and gibbon.

Nucleolus organizer regions were detected by the Ag-AS silver method in fixed metaphase chromosomes from human and primates. In the human, silver was deposited in the secondary constriction of a maximum of five pairs of acrocentric chromosomes: 13, 14, 15, 21 and 22. The chimpanzee also had five pairs of acrocentric chromosomes stained, corresponding to human numbers 13, 14, 18, 21 and 22. A gibbon had a single pair of chromosomes with a secondary constriction, which corresponded to the nucleolus organizer region. In each case the Ag-AS method detected the sites which have been shown by in situ hybridization to contain the ribosomal RNA genes. An orangutan had eight pairs of acrocentric chromosomes stained with Ag-AS, probably corresponding to human numbers 13, 14, 15, 18, 21 and 22, plus two others. Two gorillas had silver stain over two pairs of small acrocentric chromosomes and at the telomere of one chromosome 1. The larger gorilla acrocentric chromosomes had no silver stain although they all had secondary constrictions and entered into satellite associations.

Animals↗
PubMed1975

The location of the nucleolus organizer regions in Drosophila hydei.

The positions of the nucleolus organizer regions in metaphase chromosomes of Drosophila hydei were detected by in situ hybridization experiments. In agreement with earlier conclusions the nucleolus of the X chromosome was found to originate in a terminal region of the heterochromatic arm. The Y chromosome contains two nucleolus organizers, one in a terminal postion of the long arm, and the other in the short arm. The implications with respect to the evolution of the Y chromosome are discussed.

Animals↗
PubMed1980

Inheritance of Ag-stainability of the nucleolus organizer regions in domestic sheep, Ovis aries.

One of the nucleolus organizer regions of sheep is located on chromosome 25, which forms one arm of a Robertsonian translocation chromosome (t3). By mating sheep heterozygous and homozygous for the t3 chromosome, and with various Ag-staining frequencies and deposit sizes, the heritability of the Ag-stainability could be determined. The inheritance of Ag-stainability was studied in 54 sheep in five pedigree groups. It was shown that the Ag-staining of a NOR is a heritable property. Matings of animals heterozygous for Ag-stainability provided an estimate of recombination frequency of the short arm of t3.

Animals↗
PubMed1980

Abundance of protein-bound sulfhydryl and disulfide groups at chromosomal nucleolus organizing regions: a cytochemical study on the selective silver staining of NORs.

Silver stainability of the chromosomal nucleolus organizing regions that contain the structural genes for ribosomal RNA can be abolished by proteolytic and oxidative treatments. Histone extraction has no effect. This indicates that reducing groups of non-histone chromosomal proteins are responsible for silver staining. Treatment with fluorescent sulfhydryl and disulfide specific reagents followed by silver staining demonstrates coincidence of silver dots and brightly fluorescent spots at the short arms of human acrocentric chromosomes where ribosomal RNA-genes are located. After treatment with cupric sulfite reagent in the presence of urea fluorescence and silver staining was no longer possible. Silver staining has been reported to be associated with ribosomal RNA-gene activity. Acrocentric chromosomes that are negative in silver staining also lack the brightly fluorescent spots. Therefore, we conclude that an abundance of protein-bound sulfhydryl and disulfide groups occur at nucleolar organizing regions with active genes. Differentially fluorescing spots could not be observed after staining with fluorescamine. So, either the sulfhydryl reagents used in this study are much more sensitive than fluorescamine to study protein distributions in cytological preparations, or our observations point to a local accumulation of some specific protein(s) rich in sulfhydryls. The presence of many sulfhydryl and disulfide groups at the nucleolus organizing regions seems suggestive of a great flexibility of protein(s) by transition of sulfhydryl groups to disulfide bridges and vice versa at these highly active regions of the genome.

Cells, Cultured↗
PubMed1990

Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae.

The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text.

Animals↗
PubMed1989

Differential silver-positive nucleolus organizer region activity in normal and malignant murine tissues.

Transcriptionally active nucleolus organizer regions (NORs) were analyzed using a silver-staining technique. The levels of silver-positive NOR activity for normal murine bone marrow and thymus cells were established, and significant differences in ribosomal RNA gene activity were observed. When tumor cells originating from these two tissue types were also studied, significant differences were seen not only between the normal and malignant tissues, but between the two tumor types as well. These differences in ribosomal RNA gene activity with respect to cell type and malignancy may be useful diagnostically.

Animals↗
PubMed1987

The effect of pH on silver staining of nucleolus organizer regions.

The effect of pH on silver staining of the nucleolus organizer regions (NORs) of human chromosomes has been investigated between pH 6.5 and 12.0. Nonvolatile mixtures of ethanolamine and ethanolammonium nitrate replaced the ammonia of standard procedures. The optimal NOR staining obtained at pH 3.5 by the silver staining procedure of Howell and Black served as a standard; this procedure stained all ten NORs in 90% of mitoses. Similar NOR staining was found in 75% of mitoses stained at pH 11.7 or 11.8, but only in 10-15% of mitoses stained between pH 11.6 and 10.0. Between pH 10.0 and 9.0 NOR staining was incomplete, and between pH 8.5 and 6.5 there was no NOR staining.

Chromosome Banding↗