Karyotype plasticity in crickets: Numerical, morphological, and nucleolar organizer region distribution pattern of Anurogryllus sp.

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assignment of Rfp-Y to the chicken major histocompatibility complex/NOR microchromosome and evidence for high-frequency recombination associated with the nucleolar organizer region.

Rfp-Y is a second region in the genome of the chicken containing major histocompatibility complex (MHC) class I and II genes. Haplotypes of Rfp-Y assort independently from haplotypes of the B system, a region known to function as a MHC and to be located on chromosome 16 (a microchromosome) with the single nucleolar organizer region (NOR) in the chicken genome. Linkage mapping with reference populations failed to reveal the location of Rfp-Y, leaving Rfp-Y unlinked in a map containing >400 markers. A possible location of Rfp-Y became apparent in studies of chickens trisomic for chromosome 16 when it was noted that the intensity of restriction fragments associated with Rfp-Y increased with increasing copy number of chromosome 16. Further evidence that Rfp-Y might be located on chromosome 16 was obtained when individuals trisomic for chromosome 16 were found to transmit three Rfp-Y haplotypes. Finally, mapping of cosmid cluster III of the molecular map of chicken MHC genes (containing a MHC class II gene and two rRNA genes) to Rfp-Y validated the assignment of Rfp-Y to the MHC/NOR microchromosome. A genetic map can now be drawn for a portion of chicken chromosome 16 with Rfp-Y, encompassing two MHC class I and three MHC class II genes, separated from the B system by a region containing the NOR and exhibiting highly frequent recombination.

Histologic grading and nucleolar organizer regions in oral squamous cell carcinomas

OBJECTIVE: The purposes of this study were to histologically assess different types of oral squamous cell carcinoma and the silver-binding nucleolar organizer region (AgNOR) morphology in neoplastic cells, as well as to quantify the number of AgNORs in each type of carcinoma in order to relate AgNOR count and histologic grading. MATERIAL AND METHODS: Twenty-eight cases of oral squamous cell carcinoma were divided into 4 groups, namely well-differentiated, moderately differentiated, poorly differentiated, and undifferentiated. For NOR study, 3-µm-thick sections were stained with 50% aqueous silver nitrate solution. The predominant microscopic pattern of NORs was determined. Quantitative analyses of NORs were obtained of all cells present on each histological field using a 0.025 mm² eyepiece graticule. Different histological fields were analyzed until the total number of NORs was 120 cells for each tumor. Kruskall-Wallis test was applied to compare the groups of sample data at a significance level of p=0.05. RESULTS: The mean number of AgNORs per nucleus was 3.20 for the well-differentiated group, 5.33 for the moderately differentiated one, 8.27 for the poorly differentiated one, and 10.08 for the undifferentiated one. AgNOR count was significantly different (p<0.05) among all of the studied groups. CONCLUSION: AgNOR staining technique seems to be a useful diagnostic tool since differences in AgNOR numeric values can be identified in the different types of oral squamous cell carcinoma. This technique is easy to handle and inexpensive, thus justifying its large use in histopathology.

Variability of the nucleolar organizer activity in human lymphocytes via Ag-staining.

Chromosomes with Ag staining that varies from one metaphase to the other can be distinguished from those with an Ag-staining that is the same in all metaphases. The intercellular variation of an Ag-NOR can be attributed to many different factors. Whatever the importance of technical factors, they do not seem to account for the large variations in Ag-staining which were observed for each ac. This suggests the existence of a natural intercellular variability of the NOR's activity. The variation of the Ag-stainability of a given NOR, the diversity of Ag-stainings observed on the ten ac of one individual and the differences that exist between individuals raise the question of the existence of a compensation of activity between nucleolar organizers. The study, for each individual, of the mean sum of staining per metaphase reveals that this value is not absolutely constant from one individual to another; in the carriers of Robertsonian fusions it is smaller than in chromosomally normal individuals. The analysis of the transmission shows that inactive NORs remain inactive and that active NORs present a variation in the activity from one generation to the next.

Argyrophilic nucleolar organizer regions (AgNORs) in odontogenic myxoma (OM) and ameloblastic fibroma (AF)

Ten cases of odontogenic myxoma (OM) and six cases of ameloblastic fibroma (AF) were subjected to comparative analysis by the AgNOR technique, in order to determine a possible difference in cell proliferation index between these lesions. The mean AgNOR number of the mesenchymal component of AF was compared with its epithelial component and the difference was not found to be statistically significant. The mean AgNOR index of the AF group was significantly higher than that of the OM group. Moreover, the mesenchymal component of AF demonstrated increased AgNOR numbers compared with that of OM (P<0.05). These results suggest that the epithelial and mesenchymal components of AF may have similar cell proliferative activity. However, the cell proliferative index of this lesion seems to be higher than that of OM.

Heteropicnotic chromatin and nucleolar activity in meiosis and spermiogenesis of Limnogonus aduncus (Heteroptera, Gerridae): a stained nucleolar organizing region that can serve as a model for studying chromosome behavior.

Males of Limnogonus aduncus were found to have the sex chromosome system X0 and chromosome number 2n = 23 (22A + X0). Testis cells were stained with lacto-acetic orcein and silver nitrate so that changes in the morphology and degree of staining of the heteropicnotic chromatin and the nucleolar material could be observed during meiosis and spermiogenesis. These structures share the same nuclear position and could be seen until almost the end of spermiogenesis. A chromosome region stained with silver nitrate was indicative of a nucleolar organizing region (NOR), which is rarely detected in Heteroptera with this technique. The NOR is located at one end of a single member of an autosome pair. The finding of this stained region enabled us to observe that the telomeric association of sister chromatids that characterizes the Heteroptera does not include the chromosome ends, where NORs are located; we also observed in anaphase that the chromosome end through which it is pulled to the pole is the one containing the NOR. Another observation was that the single nucleolar body present in the cells at anaphase never goes to the cell pole that does not receive the NOR. We conclude that L. aduncus is a good model for cytogenetic studies involving nucleolar activity and also may be useful for studying the mechanisms of activation and inactivation of kinetic activity at the chromosome ends. Although the chromosomes of Heteroptera are known to be holocentric, whether kinetic activity is restricted to one or involves both chromosome ends is still not well understood.

Evaluation of argyrophilic nucleolar organizer regions in oral tumor progression

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Phyllodes tumors of the breast: Correlation of nucleolar organizer regions with histopathological malignancy grading, flow cytometric DNA analysis and clinical outcome

To examine whether nucleolar organizer regions detected by argyrophilia (Ag-NOR counts) can be used as a prognostic indicator in phyllodes tumors of the breast, and to compare its usefulness with that of DNA flow cytometric analysis, 28 cases of breast phyllodes tumors (including 15 benign, two borderline and 11 malignant tumors) were subjected to Ag-NOR staining and counting as well as DNA flow cytometric analysis. S-phase fraction and DNA ploidy analysis showed useful trends for improving outcome predictions in malignant phyllodes tumors. However, high Ag-NOR counts were significant in predicting survival status (P = 0.013) and reached near statistical significance in predicting survival times (P = 0.07). In predicting survival status, results for Ag-NOR counts were significantly better than those for ploidy analysis (P = 0.02) and S-phase fraction (P < 0.01). Only S-phase fraction was significantly predictive of survival times (P = 0.025). It is concluded that Ag-NOR counts and DNA flow cytometric analysis, easily performed using paraffin sections, give information that can improve predictions made by histopathological classification. Ag-NOR counts are significant in predicting survival in the presence of histopathological features of malignancy.

Cytogenetic and identification of the nucleolus organizer region in Heliconia bihai (L.) L.

The genus Heliconia is not much studied and the number of existing species in this genus is still uncertain. It is known that this number relies between 150 to 250 species. In Brazil, about 40 species are native and known by many different names. The objective of this paper was to characterize morphometrically and to identify the NOR (active nucleolus organizer regions) by Ag-NOR banding of chromosomes of Heliconia bihai (L) L. Root meristems were submitted to blocking treatment in an amiprofos-methyl (APM) solution, fixed in methanol-acetic acid solution for 24 hours, at least. The meristems were washed in distilled water and submitted to enzymatic digestion with pectinase enzyme. The slides were prepared by dissociation of the root meristem, dried in the air and also on hot plate at 50°C. Subsequently, some slides were submitted to 5% Giemsa stain for karyotype construction and to a solution of silver nitrate (AgNO3) 50% for Ag-NOR banding. The species H. bihai has 2n = 22 chromosomes, 4 pairs of submetacentric chromosomes and 7 pairs of metacentric chromosomes, and graded medium to short (3.96 to 0.67 μM), with the presence of active NOR in pairs 1 and 2 and interphase cells with 2 nucleoli. These are the features of a diploid species.

Accentuated polymorphism of heterochromatin and nucleolar organizer regions in Astyanax scabripinnis (Pisces, Characidae): tools for understanding karyotypic evolution

Astyanax scabripinnis has been considered a species complex because it presents high karyotypic and morphological variability among its populations. In this work, individuals of two A. scabripinnis populations from different streams in the same hydrographic basin were analyzed through C-banding and AgNOR. Although they present distinct diploid numbers, they show meta and submetacentric chromosome groups highly conserved (numerically and morphologically). Other chromosomal characteristics are also shared by both populations, as the pattern of constitutive heterochromatin distribution (large blocks in the telomeric regions of subtelocentric and acrocentric chromosomes) and some nucleolar chromosomes. Inter-individual variations both in the number and size of heterochromatic blocks, and in the number and localization of NORs were verified in the studied populations, characterizing them as polymorphics for these regions. The mechanisms involved in the dispersion of heterochromatin and NORs through the karyotypes, as well as the possible events related to the generation of polymorphism of those regions are discussed. Furthermore, relationships between these populations and within the context of the scabripinnis complex are also approached.

Karyotype characterization, constitutive heterochromatin and nucleolus organizer regions of Paranaita opima (Coleoptera, Chrysomelidae, Alticinae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)