Pattern of nucleolar organizer region activity during male meiosis in Callicrania seoanei (Orthoptera) as analyzed by silver staining: evidences for a possible reactivation in the period between the two meiotic divisions

Genome ◽  
1987 ◽  
Vol 29 (3) ◽  
pp. 516-518 ◽  
Author(s):  
J. Santos ◽  
C. Sentis ◽  
J. Fernandez-Piqueras
Keyword(s):  
Key Words ◽  
Silver Staining ◽  
Transcriptional Activity ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Male Meiosis ◽  
Positive Material ◽  
Ribosomal Cistrons ◽  
Early Spermatid

Silver staining of spermatocytes and early spermatid nuclei from the neo XY race of the Tettigonioid species Callicrania seoanei reveals an active nucleolar organizer region (NOR) located proximally in a medium-sized bivalent. Ag-positive material was present at the NOR in all stages of male meiosis. However, the results obtained indicate that transcriptional activity of ribosomal cistrons (rDNA) is not maintained throughout spermatogenesis, but that NOR reactivation might occur in the period between the two meiotic divisions in addition to the more general postmeiotical reactivation in the early spermatid nuclei. Key words: NOR activity, silver staining, male meiosis, Callicrania seoanei (Orthoptera).

Sequential silver staining and in situ hybridization reveal a direct association between rDNA levels and the expression of homologous nucleolar organizing regions: a hypothesis for NOR structure and function

1998 ◽  
Vol 111 (10) ◽  
pp. 1433-1439
Author(s):  
F. Zurita ◽  
R. Jimenez ◽  
M. Burgos ◽  
R.D. de la Guardia
Keyword(s):  
Transcription Factors ◽  
In Situ Hybridization ◽  
Silver Staining ◽  
Organizer Region ◽  
Nucleolar Organizer ◽  
Interindividual Variation ◽  
Nucleolar Organizer Regions ◽  
Single Pair ◽  
Ribosomal Cistrons

We have developed a procedure for sequential silver staining and in situ hybridization to analyze the relationship between the amount of rDNA present in nucleolar organizer regions, as estimated by in situ hybridization, and their level of expression, as estimated by the silver signal. For simplicity we used cells from the insectivorous mole Talpa occidentalis, which have a single pair of nucleolar organizer regions in chromosome pair 3. The relative content of ribosomal cistrons was also related to the hierarchy of activation of the nucleolar organizer regions present in this chromosomal pair. Statistical analyses demonstrated that both the relative level of expression and the activation hierarchy depended mainly on the number of ribosomal cistrons in nucleolar organizer regions. We propose a functional two-step hypothesis, which is consistent with most known data concerning interchromosomal, intercellular and interindividual variation in a number of plant and animal species, including Talpa occidentalis. In step one, the first available transcription factors bind randomly to the ribosomal promoters, such that larger nucleolar organizer regions are more likely to recruit them. In the second step the remaining transcription factors are recruited in a cooperative way, thus completing activation of one nucleolar organizer region, before the next one becomes active.

Metaphase association of mammalian chromosomes

Genome ◽  
1987 ◽  
Vol 29 (6) ◽  
pp. 807-810
Author(s):  
U. Mayr-Wohlfart ◽  
S. Adolph ◽  
Ch. Klett ◽  
H. Hameister
Keyword(s):  
Key Words ◽  
Chromosomal Localization ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Association Behavior ◽  
Per Se ◽  
Ectopic Pairing

The association behavior of chromosomes bearing nucleolar organizer region (NOR) and (or) C-heterochromatin in metaphase plates was analyzed. Different species with an informative chromosomal localization of NOR and C-heterochromatin were evaluated. Several examples indicate that the well-known metaphase association is not due to NORs or NOR activity per se. Other mechanisms such as ectopic pairing are responsible for the association. These types of pairing seem to be enhanced by the chromatin-decondensing effect of nearby NOR activity. Key words: NOR, C-heterochromatin, metaphase association.

scholarly journals Genome restructuring in rye affects the expression, organization and disposition of homologous rDNA loci

2002 ◽  
Vol 115 (14) ◽  
pp. 2839-2846
Author(s):  
Ana D. Caperta ◽  
Nuno Neves ◽  
Leonor Morais-Cecílio ◽  
Rui Malhó ◽  
Wanda Viegas
Keyword(s):  
Silver Staining ◽  
Organizer Region ◽  
Expression Patterns ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Parental Origin ◽  
Metaphase Chromosomes ◽  
Structural Variant ◽  
Sequence Recognition ◽  
Rdna Loci

The standard rye cultivar `Imperial' and a structural variant carrying an intact 1R chromosome and two telocentric 1R chromosomes (short and long arms)were used to investigate expression patterns of homologous rDNA loci, and the influence of chromosome structural change on their interphase organisation and relative disposition. Sequential silver staining and in situ hybridization with the rDNA probe pTa71, established a correspondence between the expression and organization patterns of rDNA domains in metaphase and interphase cells. In most cells of the cultivar Imperial, nucleolar organizer region (NOR)silver staining on metaphase chromosomes with equivalent numbers of rDNA genes revealed a size heteromorphism between homologous rDNA loci, resulting from their differential expression. NOR heteromorphism in the structural variant line was significantly reduced. The preferential activity of one NOR over its homologue was found to be random within cells and independent of parental origin. Nucleotypic modifications mediated by changes in the 1R chromosome structure include increased proximity between homologous rDNA loci in interphase, and an increase in the frequency of cells with intra-nucleolar ribosomal condensed chromatin. These results seem to indicate a `sequence recognition' process for the regulation of homologous loci.

Molecular cloning and characterization of an unusually large intergenic spacer from the Nor-B2 locus of hexaploid wheat

Genome ◽  
1996 ◽  
Vol 39 (2) ◽  
pp. 288-292 ◽  
Author(s):  
R. K. Sardana ◽  
R. B. Flavell
Keyword(s):  
Key Words ◽  
Ribosomal Dna ◽  
Hexaploid Wheat ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Intergenic Spacer ◽  
Nucleolar Organizer ◽  
Spacer Length ◽  
Spacer Length Variants

An allelic rDNA variant from the Nor-B2 locus of 'Bezostaya' wheat that forms an especially active nucleolus was cloned and characterized. It carries an unusually large intergenic spacer compared with rDNA units in most other wheat genotypes. The additional intergenic length is in the array of 135-bp A repeats and not in other internal repeats. These A repeats have sequences nearly identical to other A repeats described for other alleles. It is suggested therefore that the more active Nor-B2 locus of 'Bezostaya' may be due to the constituent rDNA units possessing a larger array of A repeats. Key words : ribosomal DNA, nucleolar organizer region, A and B repeats, allelic, spacer length variants.

scholarly journals Silver staining of the nucleolar organizer regions (NORs) on Lowicryl and cryo-ultrathin sections.

1985 ◽  
Vol 33 (5) ◽  
pp. 389-399 ◽  
Author(s):  
F J Moreno ◽  
D Hernandez-Verdun ◽  
C Masson ◽  
M Bouteille
Keyword(s):  
Silver Staining ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Enzymatic Digestion ◽  
Rnase A ◽  
Micrococcal Nuclease ◽  
Nucleolar Organizer Regions ◽  
Step Procedure ◽  
Ultrathin Sections

Nucleolar organizer region (NOR) silver staining was applied to sections of fixed material. A positive reaction on cryo-ultrathin sections was found as well as on semithin and ultrathin Lowicryl sections. Repeatable staining that was easy to control was obtained by a one-step procedure after aldehyde-Carnoy fixation. Fixation of the material by formaldehyde and glutaraldehyde alone in cacodylate buffer also maintained reaction selectivity when ammonium chloride was used after fixation. Enzymatic digestion by pronase, RNase A, DNase I, or micrococcal nuclease was applied to ultrathin Lowicryl sections. Pronase digestion removed the silver-stained proteins, whereas digestion by the nucleases did not. A routine procedure is proposed for easy NOR silver staining of sections that preserves a good tissue ultrastructure and is also compatible with cytochemical and immunological investigations.

scholarly journals Preliminary investigation on the variation of the nucleolar organizer region in the breeding chinchilla karyotype

2016 ◽  
Vol 72 (6) ◽  
pp. 373-377 ◽  
Author(s):  
Marta Kuchta-Gładysz ◽  
Agnieszka Otwinowska-Mindur ◽  
Piotr Niedbała ◽  
Olga Szeleszczuk ◽  
Joanna Głowacka
Keyword(s):  
Silver Staining ◽  
Organizer Region ◽  
Preliminary Investigation ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
Silver Deposit ◽  
Nor Polymorphism ◽  
The Mean ◽  
Class Iv

The objective of this study was to determine the variation in the number and size of nucleolar organizer regions (NOR) in the chinchilla karyotype. The study was performed with 12 standard chinchillas of two different lines. NORs were visualized on chromosome preparations by Ag-NOR silver staining. Four NOR size classes (I-IV) were determined on the basis of the results obtained, ranging from 0.070 (class I) to 0.229 (class IV). The mean NOR size was 0.144 µm² (SD=0.031 µm²) and fell within class II (from 0.101 to 0.150 µm²). Differences in the relative silver deposit area between the NOR-bearing pair of chromosomes were significant for 3 animals (P < 0.01) and for 1 animal (P < 0.05). The mean number of NORs in the animals ranged from 1.4 to 2.0 (SD=0.00–0.55). It was lower for chinchillas from central Poland (1.53±0.50) compared to those from southern Poland (1.68±0.48), with no significant differences (P > 0.05). The variation observed in the NOR size and number in the chinchilla karyotype indicates the occurrence of NOR polymorphism in the population.

scholarly journals The Role of Argyrophilic Nucleolar Organizer Region (AgNOR) Study in Cytological Evaluation of Fluids, Especially for Detection of Malignancy

2012 ◽  
Vol 10 (1) ◽  
pp. 34-39 ◽  
Author(s):  
S Karki ◽  
A Jha ◽  
G Sayami
Keyword(s):  
Silver Staining ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Staining Technique ◽  
Nucleolar Organizer Regions ◽  
Serous Effusion ◽  
Malignant Cells ◽  
Associated Proteins ◽  
Malignant Effusions

Background Serous effusion smears reported as “suspicious for malignancy” pose problems in clinical management. Silver staining for argyrophilic nucleolar organizer regions (AgNOR) has proved useful in making a cytopathologic differential diagnosis between benign and malignant cells. Nucleolar organizer regions(NORs) are loops of DNA located in acrocentric chromosomes. These NORs are visualized by silver staining technique that recognizes these argyrophilia associated proteins which are increased in malignancy. Objective This study aimed to distinguish reactive mesothelial cells from malignant cells in serous effusions using these NORs. Methods A total of 174 serous effusions received at the Department of Pathology, TUTH, during a period of one year were included in the study. Smears were studied by conventional Papanicolaou and Giemsa stains. AgNOR counts, variation in size and dispersion of AgNOR dots in smears were graded and compared in malignant and non-malignant effusions. Results Mean AgNOR counts of 10.43±0.73 and 10.21±0.51 in malignant peritoneal and pleural effusions, respectively, were significantly (p<0.0001) greater as compared with counts of 2.12±0.54 and 2.11±0.54 in non-malignant effusions. The AgNORs were irregular in shape in malignant effusions whereas they were comparatively larger, single dots in benign effusions. AgNOR size and dispersion were of higher grade in significantly greater proportion of malignant as compared with non malignant effusions (p<0.0001). Of the cytologically suspicious samples, nine were in the malignant range and one was in the benign range. Conclusion AgNOR study appears to be clinically useful as an additional diagnostic tool for use in serous effusion when the cytologic diagnosis is difficult. KATHMANDU UNIVERSITY MEDICAL JOURNAL  VOL.10 | NO. 1 | ISSUE 37 | JAN - MAR 2012 | 44-47 DOI: http://dx.doi.org/10.3126/kumj.v10i1.6913

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