Presence Of Nucleolar Organizer Regions Research Articles

A new multiple sex chromosome system X1X1X2X2/X1Y1X2Y2 in Siluriformes: cytogenetic characterization of Bunocephalus coracoideus (Aspredinidae).

We analyzed one Bunocephalus coracoideus population from the Negro River basin using cytogenetic techniques. The results showed a diploid number of 42 chromosomes in both sexes, with the karyotypic formula4m+14sm+24a and fundamental number (FN)=60 for females and the formula5m+14sm+23a and FN=61 for males, constituting an X1X1X2X2/X1Y1X2Y2 multiple sex chromosome system. The constitutive heterochromatin is distributed in the pericentromeric regions of most of the chromosomes, except for the sex chromosomes, of which the X1, X2, and Y1 chromosomes were euchromatic and the Y2 chromosome was partially heterochromatic. 18S rDNA mapping confirmed the presence of nucleolar organizer regions on the short arms of the fifth chromosomal pair for both sexes. The 5S rDNA is present in the terminal regions of the short arms on the 2nd, 10th, and 12th pairs and on the X2 chromosome of both sexes; however, we observed variations in the presence of these ribosomal cistrons on the Y1 chromosome, on which the cistrons are pericentromeric, and on the Y2 chromosome, on which these cistrons are present in the terminal portions of the short and long arms. Telomeric sequences are located in the terminal regions of all of the chromosomes, particularly conspicuous blocks on the 10th and 12th pairs and internal telomeric sequences in the centromeric regions of the 1st, 6th, and 9th pairs for both sexes. This work describes an new sex chromosomes system for the Siluriformes and increases our genetic knowledge of the Aspredinidae family.

Karyotypic variation in Rhinophylla pumilio Peters, 1865 and comparative analysis with representatives of two subfamilies of Phyllostomidae (Chiroptera)

The family Phyllostomidae belongs to the most abundant and diverse group of bats in the Neotropics with more morphological traits variation at the family level than any other group within mammals. In this work, we present data of chromosome banding (G, C and Ag-NOR) and Fluorescence In Situ Hybridization (FISH) for representatives of Rhinophylla pumilio Peters, 1865 collected in four states of Brazil (Amazonas, Bahia, Mato Grosso and Pará). Two karyomorphs were found in this species: 2n=34, FN=64 in populations from western Pará and Mato Grosso states and 2n=34, FN=62 from Amazonas, Bahia, and northeastern Pará and Marajó Island (northern). Difference in the Fundamental Number is determined by variation in the size of the Nucleolar Organizer Region (NOR) accompanied with heterochromatin on chromosomes of pair 16 or, alternatively, a pericentric inversion. The C-banding technique detected constitutive heterochromatin in the centromeric regions of all chromosomes and on the distal part of the long arm of pair 15 of specimens from all localities. FISH with a DNA telomeric probe did not show any interstitial sequence, and an 18S rDNA probe and silver staining revealed the presence of NOR in the long arm of the pair 15, associated with heterochromatin, and in the short arm of the pair 16 for all specimens. The intra-specific analysis using chromosome banding did not show any significant difference between the samples. The comparative analyses using G-banding have shown that nearly all chromosomes of Rhinophylla pumilio were conserved in the chromosome complements of Glossophaga soricina Pallas, 1766, Phyllostomus hastatus Pallas, 1767, Phyllostomus discolor Wagner, 1843 and Mimon crenulatum Geoffroy, 1801, with a single chromosomal pair unique to Rhinophylla pumilio (pair 15). However, two chromosomes of Mimon crenulatum are polymorphic for two independent pericentric inversions. The karyotype with 2n=34, NF=62 is probably the ancestral one for the other karyotypes described for Rhinophylla pumilio.

Biogeographical karyotypic variation of Rhinophylla fischerae (Chiroptera: Phyllostomidae) suggests the occurrence of cryptic species

The genus Rhinophylla Peters, 1865 (Carolliinae: Phyllostomidae) com- prises three species: R. pumilio Peters, 1865, R. fi scherae Carter, 1966 and R. alethina Handley, 1966. Only the fi rst two species have been cytogenetically studied to date. Previous studies on specimens of Rhinophylla fi scherae from two populations from East of Andes (Colombia) showed the karyotype with 2n=34 and FN=56. In this pa- per, we report the results of cytogenetic analysis of six specimens of Rhinophylla fi scherae from Brazil. Probably chromosomal differences can be found among the populations because of the geographic distance. Metaphase chromosomes were ob- tained in the fi eld by direct extraction of bone marrow. The metaphases were ana- lyzed by conventional staining, G- and C-banding, NOR-staining and FISH with telo- meric probes. Rhinophylla fi scherae has 2n=38 and Fundamental Number FN=68, with small amounts of constitutive heterochromatin in the centromeric regions of the chromosomes and the long arm of pair 16. Fluorescence in situ hybridization using telomeric probes did not show any interstitial sequences. Hybridization with human 18S and 28S rDNA probes and silver staining revealed the presence of Nucleolar Organizer Regions at the long arms of pairs 16 and 18. The pattern of G-banding showed that this population had a huge chromosome variation compared with pre- vious studies on specimens of Rhinophylla fi scherae. The chromosomal differences among populations that have been morphologically classifi ed as R. fi suggest that this species should be considered a cryptic species complex, and that the popu- lations from different geographical regions analyzed to date should be considered species of this complex, where the chromosomal rearrangements had key importance.

Evaluation of argyrophilic nucleolar organizer regions in oral tumor progression

The aim of this study was to compare the presence of nucleolar organizer regions (NORs) in normal oral mucosa, dysplasia and microinvasive carcinoma. All histological specimens were reviewed according to the modified classification and staging system for oral leukoplakia described by van-der-Waal et al. [Oral Oncol. 36 (2000) 264]. NOR quantification was performed with an image analyzer after staining by the argyrophilic nucleolar region technique. The morphometric results were statistically different for normal mucosa, dysplasia and microinvasive carcinoma. It was concluded that an increase of NOR activity follows the disease progression and may reflect the degree of cellular proliferation and malignancy.

Chromosome polymorphism in Salmo trutta morpha lacustris from Poland, Wdzydze Lake population: Variation in the short arm length of chromosome eleven

A population of Salmo trutta m. lacustris from Lake Wdzydze was karyotyped using C-banding and fluorochrome staining techniques. The chromosome number was 2n = 80, and the chromosome arm number (NF) was 100-102. Variation in the size of the short arm of chromosome pair eleven was observed: the presence of heterochromatin on this arm was confirmed by C-banding and DAPI staining. Chromomycin A3 and silver stainings revealed the presence of nucleolar organizer region (NOR) on this arm. Additional CMA3-positive regions were observed on two acrocentric chromosomes. The polymorphism of chromosome pair eleven observed in Salmo trutta m. lacustris probably resulted from deletions or multiplications of heterochromatin connected to NOR. The karyotype and observed polymorphism of the NOR-bearing chromosome pair was the same as observed in other ecological forms of Salmo trutta.

Nucleolar organizer regions in meningiomas

Paraffin sections of 305 meningeal tumours were analysed for the presence of nucleolar organizer region (Ag-NOR) in the neoplastic cells, using a one step silver-colloidal staining method. The mean (+/- SEM) Ag-NOR counts were 2.73 +/- 0.21 for atypical and 2.91 +/- 0.18 for papillary variants of meningioma. In meningotheliomatous and transitional variants of meningioma, the mean Ag-NOR counts were 1.41 +/- 0.34 and 1.38 +/- 0.31, respectively. The recurrence rates were significantly higher in atypical meningiomas than in other histopathological variants (p < 0.05). Differences in the mean Ag-NOR numbers between meningothelial and transitional variants in their primary and recurrent tumours were not significantly different (p > 0.05). The results of this study indicates that estimation of Ag-NORs can be applied in predicting the aggressive clinical behaviour of primary meningeal tumours.

Distribution of chromosomal polymorphisms in three subspecies of squirrel monkeys (genus &lt;i&gt;Saimiv&lt;/i&gt;&lt;i&gt;i&lt;/i&gt;)

The presence of nucleolar organizer regions (NORs) and C-band polymorphisms has been examined in three subspecies of squirrel monkeys, Saimiri sciureus sciureus, S. boliviensis boliviensis, and S. boliviensis peruviensis. Pericentric inversions in chromosomes 15 and 16 were also examined in the three groups. Chromosome 15 was acrocentric in S. s. sciureus and submetacentric in S.b. boliviensis and S.b. peruviensis. Chromosome 16 was acrocentric in S.s. sciureus and S.b. boliviensis while being submetacentric in S.b. peruviensis. There was a significant difference in the distribution of the C-band polymorphisms on chromosomes 5 and 14 in the three groups, as determined by Chi-square analysis, while no difference was observed in the distribution of the NOR polymorphism on chromosome 2. The NOR polymorphism and the interstitial C-band polymorphism of chromosome 14 were found in all three groups; the C-band polymorphism of chromosome 5 was found only in S.s. sciureus. Twelve pedigreed families were examined. Pedigree analyses were consistent with codominant inheritance of each polymorphism. The results of these cytogenetic studies in squirrel monkeys are pertinent to genetic management and research protocols.