Nucleolar Organizer Research Articles

Arjirofilik Nükleolar Organize Edici Bölgeler Non ST Elevasyonlu Miyokard İnfarktüsünde Hipoksik Yanıtın Yeni bir Belirteci Olabilir mi?

Objective: Non-ST elevation myocardial infarction (NSTEMI) is a type of acute coronary syndrome and its’ incidence is similarly high to ST-elevation myocardial infarction. Nucleolar organizing regions (NORs) are located of the secondary structure of acrocentric chromosome and composed of proteins and ribosomal DNA (rDNA) some of which are argyrophilic. We aimed to investigate the change of AgNOR proteins, which increase in hypoxia, in patients with NSTEMI.
 Methods: A total of 125 participants, 63 patients with NSTEMI and 62 volunteers without any acute coronary syndrome were included in the study. Echocardiography was performed and both mean AgNOR Number and total AgNOR area/total nuclear area (TAA/TNA) were detected for each individuals.
 Results: The mean AgNOR number and TAA/TNA ratio were significantly higher in the NSTEMI group than control (p

The Effect of Thelison Use in The Etiology of Lung Disorders among Homeless People

Background: Thelison, the adhesive synthetic material that bind surface together, is widely used in industry and domestic purpose along with epoxy, glue and putty. The aim of this study was to detect the effect of thelison use in the etiology of lung disorders among homeless people in Khartoum State, Sudan.Materials and method: This was a descriptive cross sectional study conducted in homeless people in Khartoum State.Sputum smears samples from 80 alcohol fixed homeless thelison user were collected. After the collection of the sample, Argyrophilic Nucleolar Organizer Region (AgNOR) technique and papanicolaou (PAP) stains were applied to each sample. A questionnaire to obtain essential data about respondents was also provided for each participant.Results: Participant’s ages range was 10-37, while the mean age was 17. The range of participants duration of use per years was 1-10, while the mean was 3 years. Number of thelesion dose use per day was ranged between 1-10, while the mean was 5 years. The majority of participants (80%) showed no cellular change and 20 % showed chronic inflammation. Results showed that 31 of the study population were males (77.5%), while the female population of the study was 9 (22.5%). The mean of AgNoR score was ranged between 1-4, while the mean AgNOR score was 1. AgNoR showed insignificant association with gender, duration and number of thelesion dose used per day (p>0.05), but showed significant association with cytomorhpological and age (p<0.05).Conclusion: AgNoR score showed insignificant association with gender, duration and number of thelesion dose used per day (p>0.05), but showed significant association with cytomorhpological and age (p<0.05).Keywords: AgNoRs score, cytological changes, sputum, homeless thelison users

Argyrophilic Nucleolar Organizer Regions as New Biomarkers in ST-Elevation Myocardial Infarction.

(1) Background: ST-elevation myocardial infarction (STEMI) is an inflammatory disease in which neutrophils, macrophages, and lymphocytes accumulate in the ischemic myocardium and have important functions. Nucleolar-organizing regions (NORs) are the site of the ribosomal genes composed of ribosomal DNA and proteins. We aimed to evaluate AgNOR proteins, which have never been studied in patients with STEMI in the literature. (2) Methods: A total of 140 participants (75 with STEMI and 65 volunteers without any diagnosis of acute coronary syndrome) were included in this study. Echocardiography was carried out, and mean AgNOR number and total AgNOR area/total nuclear area (TAA/TNA) were evaluated for all individuals. (3) Results: The mean AgNOR number and TAA/TNA ratio were significantly higher in the STEMI group than the control (p < 0.001). Statistically significant relations between both TAA/TNA ratio and mean AgNOR number and interventricular septal thickness, fasting blood sugar, creatinine, HDL, hemoglobin (g/dL), WBC (µL/mL), monocytes, neutrophils, and neutrophil/lymphocyte ratio were detected (p < 0.05). Moreover, a statistically significant relation between LDL (mg/dL) and mean AgNOR number (p = 0.005) was detected. (4) Conclusion: Both AgNOR protein amounts increase depending on the hypoxia that occurs in STEMI. The AgNOR proteins may thus be promising markers in STEMI.

First record of the spatial organization of the nucleosome-less chromatin of dinoflagellates: The nonrandom distribution of microsatellites and bipolar arrangement of telomeres in the nucleus of Gambierdiscus australes (Dinophyceae).

Dinoflagellates are a group of protists whose exceptionally large genome is organized in permanently condensed nucleosome-less chromosomes. In this study, we examined the potential role of repetitive DNAs in both the structure of dinoflagellate chromosomes and the architecture of the dinoflagellate nucleus. Non-denaturing fluorescent in situ hybridization (ND-FSH) was used to determine the abundance and physical distribution of telomeric DNA and 16 microsatellites (1- to 4-bp repeats) in the nucleus of Gambierdiscus australes. The results showed an increased relative abundance of the different microsatellite motifs with increasing GC content. Two ND-FISH probes, (A)20 and (AAT)5 , did not yield signals whereas the remainder revealed a dispersed but nonrandom distribution of the microsatellites, mostly in clusters. The bean-shaped interphase nucleus of G. australes contained a region with a high density of trinucleotides. This nuclear compartment was located between the nucleolar organizer region (NOR), located on the concave side of the nucleus, and the convex side. Telomeric DNA was grouped in multiple foci and distributed in two polarized compartments: one associated with the NOR and the other peripherally located along the convex side of the nucleus. Changes in the position of the telomeres during cell division evidenced their dynamic distribution and thus that of the chromosomes during dinomitosis. These insights into the spatial organization of microsatellites and telomeres and thus into the nuclear architecture of G. australes will open up new lines of research into the structure and function of the nucleosome-less chromatin of dinoflagellates.

Nucleolar organizer region proteins enhancement in nucleoplasm’s of renal tubular cells is an indication of kidney impairment in Leishmania-infected dogs

Hyperactivation of tubular cells contributes for the progression of kidney lesions. The exacerbated expression of immunological proteins and ribosomal DNA (rDNA) transcriptional activity are observed in tubular cells. This intensified expression results in more prominent hypertrophic changes and is often accompanied by increased expression of factors involved in different phases of ribosomal biosynthesis, such as the nucleolar organizer regions (NOR). The aim of this study was to evaluate whether there is an association between NOR proteins, renal impairment, and clinical status in Leishmania-infected dogs (CanL). Forty-five dogs with CanL and six uninfected controls were assessed in this study. PCR was performed to detect parasites’ nucleic acids in kidney. Histopathological analyses were performed in kidney fragments, and NOR was detected by Ag stain (AgNOR). Leishmania-infected dogs showed more intense inflammation and collagen deposition compared with uninfected controls. Biochemical alterations were observed only in Leishmania-infected dogs. AgNORs per cell were significantly higher in clinically affected dogs and higher histopathological lesion score was observed in Leishmania-infected dogs. Positive correlations between number of NORs per cell in medullary region and histopathological lesion score were observed. Furthermore, AgNOR expression, intensity of renal lesions, and clinical sigs was associated in Leishmania-infected dogs. We propose that the detection of AgNOR proteins could be used to better estimate the kidney tubular damage at the time of examination in Leishmania-infected dogs as a marker to estimate renal impairment in dogs with CanL.

Nucleolar and Coiled-Body Phosphoprotein 1 Is Associated With Stemness and Represents a Potential Therapeutic Target in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and lacks approved specific targeted therapies. One of the major reasons why TNBC is difficult to treat is the high proportion of cancer stem cells within the tumor tissue. Nucleolus is the location of ribosome biogenesis which is frequently overactivated in cancer cells and overactivation of ribosome biogenesis frequently drives the malignant transformation of cancer. Nucleolar and coiled-body phosphoprotein 1 (NOLC1) is a nucleolar protein responsible for nucleolus organization and rRNA synthesis and plays an important role in ribosome biogenesis. However, the correlation of NOLC1 expression with patient prognosis and its value as a therapeutic target have not been evaluated in TNBC. In the current study, based on bioinformatics analysis of the online databases, we found that the expression of NOLC1 was higher in breast cancer tissues than normal tissues, and NOLC1 was expressed at a higher level in TNBC than other subtypes of breast cancer. GSEA analysis revealed that stemness-related pathways were significantly enriched in breast cancer with high NOLC1 gene expression. Further analyses using gene expression profiling interactive analysis 2 (GEPIA2), tumor immune estimation resource (TIMER) and search tool for retrieval of interacting genes/proteins (STRING) demonstrated that NOLC1 was significantly associated with stemness in both all breast cancer and basal-like breast cancer/TNBC patients at both gene and protein levels. Knockdown of NOLC1 by siRNA decreased the protein level of the key stemness regulators MYC and ALDH and inhibited the sphere-forming capacity in TNBC cell line MDA-MB-231. Univariate and multivariate Cox regression analyses demonstrated that NOLC1 was an independent risk factor for overall survival in breast cancer. PrognoScan and Kaplan-Meier plotter analyses revealed that high expression of NOLC1 was associated with poor prognosis in both all breast cancer and TNBC patients. Further immunohistochemical analysis of breast cancer patient samples revealed that TNBC cells had a lower level of NOLC1 in the nucleus compared with non-TNBC cells. These findings suggest that NOLC1 is closely associated with the stemness properties of TNBC and represents a potential therapeutic target for TNBC.

Nucleolar Organizer Regions as Transcription-Based Scaffolds of Nucleolar Structure and Function.

Eukaryotic genomes maintain multiple copies of ribosomal DNA gene repeats in tandem arrays to provide sufficient ribosomal RNAs to make ribosomes. These DNA repeats are the most highly transcribed regions of the genome, with dedicated transcriptional machinery to manage the enormous task of producing more than 50% of the total RNA in a proliferating cell. The arrays are called nucleolar organizer regions (NORs) and constitute the scaffold of the nucleolar compartment, where ribosome biogenesis occurs. Advances in molecular and cellular biology have brought great insights into how these arrays are transcribed and organized within genomes. Much of their biology is driven by their high transcription level, which has also driven the development of unique methods to understand rDNA gene activity, beginning with classic techniques such as silver staining and Miller spreads. However, the application of modern methodologies such as CRISPR gene editing, super-resolution microscopy, and long-read sequencing has enabled recent advances described herein, with many more discoveries possible soon. This chapter highlights what is known about NOR transcription and organization and the techniques applied historically and currently. Given the potential for NORs to impact organismal health and disease, as highlighted at the end of the chapter, the field must continue to develop and apply innovative analysis to understand genetic, epigenetic, and organizer properties of the ribosomal DNA repeats.

Bionomics and Karyotypic analysis of two species of Caccobius (Scarabaeinae: Scarabaeidae: Coleoptera) detected by standard staining, C-banding and AgNOR-banding

Out of 16 species of caccobius available in India, 9 are found in Haryana and 6 in Kurukshetra. The Karyotypic characterisation of two species of Caccobius, C. ultor and C. vulcanus belonging to subfamily Scarabaeinae was undertaken using standard staining, silver staining and C-banding. Both of the species were comprised of 20 chromosomes in karyotype with meioformula, 9AA+Xyp. Modal chromosome number and meta-, submeta- centric nature revealed the conservative nature of the subfamily Scarabaeinae. The analysis of constitutive heterochromatin (CH) revealed small centromeric bands in spermatogonial metaphase and small blocks located in the terminal regions of dumb bell shaped bivalents in metaphase I. At the pachytene stage of prophase I, silver staining revealed dense spots associated with nucleolar organizer regions. In addition to this, the Chiasma frequency and terminalisation coefficient were also calculated, illustrating the close relationship of Caccobius ultor and C. vulcanus with other Scrabaeinae species. In beetles as well as in other insects, the chromosome structure, pattern of constitutive heterochromatin distribution, and position of the nucleolar organizer region are all key factors in speciation.

Karyotype variability in six Amazonian species of the family Curimatidae (Characiformes) revealed by repetitive sequence mapping.

Fishes of the Curimatidae family represent one of the most important freshwater ichthyofauna groups of Central and South America, with 117 recognized species distributed in eight genera. In this study, six species - Curimata inornata, Curimatella dorsalis, and Psectrogaster falcata collected from the Lower Araguaia River, Pará, Brazil; Curimata vittata, Curimatella meyeri, and Psectrogaster rutiloides collected from the Catalão Lake, Amazonas, Brazil - were cytogenetically analyzed, investigate the occurrence and distribution of repetitive DNA classes in the karyotypes. All species had 2n=54 metacentric/submetacentric chromosomes. Despite the conservative diploid number, we observed variations in the karyotypic structure among species. Ribosomal DNA (rDNA) 18S and 5S were found in single or multiple sites, with the first report of synteny in Curimatella dorsalis, and the occurrence of several interstitial telomeric sequences (ITSs) in species of the genera Curimatella and Psectrogaster. Interspecific karyotypic diversity both concerning structure and location/position of the nucleolar organizer regions (NOR) and ribosomal DNA, suggesting the occurrence of several non-Robertsonian rearrangements driving the evolution of this family.

Role of Ki-67 and Argyrophilic Nucleolar Organiser Region (AgNoR) Counts in Squamous Cell Carcinoma

Role of Ki-67 and Argyrophilic Nucleolar Organiser Region (AgNoR) Counts in Squamous Cell Carcinoma

Evaluation of antitumoral effect of mistletoe fruit extract on Ehrlich ascites tumor cells with muse cell analyzer and argyrophilic nucleolar organizer region staining method

Abstract Introduction Mistletoe has been used alone or as a complementary therapy in the treatment of different diseases for years. In this study, the antitumoral effect of mistletoe fruit extract on Ehrlich ascites tumor (EAT) cells was evaluated. Materials and Methods EAT cells from preformed stock mice were transferred to culture dishes containing 5-fluorouracil (5-FU) and mistletoe extracts at different doses (100, 200, 400, and 800 μg/ml). These cells were incubated at 37 °C in an environment with 95% humidity and 5% CO2. At the end of the incubations, the apoptosis status of the cells, cell cycle, mitochondrial membrane potential, and proliferation status with the argyrophilic (Ag) nucleolar organizer region staining (NORs) method were evaluated. Results As a result, it was observed that the mistletoe fruit extract and 5-FU induce apoptosis of EAT cells. It was concluded that the 5-FU substance arrests the cell cycle at the G0/G1 stage, while the mistletoe arrests the cell cycle at the S and G2/M stages. The depolarization rate of the mistletoe treated cells was higher. As a result of the evaluation made with the AgNORs method, it was seen that mistletoe and 5-FU could be effective in reducing the proliferation of EAT cells. Conclusions It was seen that mistletoe fruit extract could be effective in stimulating the apoptosis and depolarization of cancer cells. The results of other studies in the literature and our study support each other. It was concluded that the mistletoe plant may be useful in cancer treatment.

AgNOR patterns and configurations in adult acute leukemia patients

The number of argyrophilic nucleolus organizer regions (AgNOR) is related to the proliferative activity of cells and the degree of neoplastic transformation. The surface area of AgNOR depending on nuclear structure may be a predictor of tumor recurrence, while research into acute leukemias is scarce. The aim of the study was to determine whether the assessment of AgNOR parameters is useful in the differentiation of acute leukemias and, together with cytogenetic changes, would allow for a quick evaluation of the risk group. The AgNOR structures were analyzed in terms of the shape, surface area and distribution in bone marrow blast cells in patients with acute leukemias. We observed significant differences in the AgNOR structures, simple, compound and complex patterns between acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Complex structures were more numerous in ALL than in AML patients. There were significant differences in the distribution of AgNOR configuration among various cytogenetic AML risk groups. We observed a significant difference in the mean number of AgNOR between ALL-T and ALL-B. We detected diversity in the AgNOR structures and pattern map in AML and ALL. Thus, presentation of a variety of AgNOR configurations is innovative and can be a useful method of differentiating patients with acute leukemia types and cytogenetic risk.

Personal Perspectives on Plant Ribosomal RNA Genes Research: From Precursor-rRNA to Molecular Evolution.

The history of rDNA research started almost 90 years ago when the geneticist, Barbara McClintock observed that in interphase nuclei of maize the nucleolus was formed in association with a specific region normally located near the end of a chromosome, which she called the nucleolar organizer region (NOR). Cytologists in the twentieth century recognized the nucleolus as a common structure in all eukaryotic cells, using both light and electron microscopy and biochemical and genetic studies identified ribosomes as the subcellular sites of protein synthesis. In the mid- to late 1960s, the synthesis of nuclear-encoded rRNA was the only system in multicellular organisms where transcripts of known function could be isolated, and their synthesis and processing could be studied. Cytogenetic observations of NOR regions with altered structure in plant interspecific hybrids and detailed knowledge of structure and function of rDNA were prerequisites for studies of nucleolar dominance, epistatic interactions of rDNA loci, and epigenetic silencing. In this article, we focus on the early rDNA research in plants, performed mainly at the dawn of molecular biology in the 60 to 80-ties of the last century which presented a prequel to the modern genomic era. We discuss – from a personal view – the topics such as synthesis of rRNA precursor (35S pre-rRNA in plants), processing, and the organization of 35S and 5S rDNA. Cloning and sequencing led to the observation that the transcribed and processed regions of the rRNA genes vary enormously, even between populations and species, in comparison with the more conserved regions coding for the mature rRNAs. Epigenetic phenomena and the impact of hybridization and allopolyploidy on rDNA expression and homogenization are discussed. This historical view of scientific progress and achievements sets the scene for the other articles highlighting the immense progress in rDNA research published in this special issue of Frontiers in Plant Science on “Molecular organization, evolution, and function of ribosomal DNA.”

Changes in the contour of karyology and histoarchitecture of the primary respiratory organ in the fish Oreochromis mossambicus (Peters, 1852) inhabiting the polluted estuarine ecosystem

The wetland ecosystem (WE) is subject to pollution by many anthropogenic activities, including domestic and industrial effluents. These effluents may contain toxic heavy metals that can interact within the aquatic ecosystem and have a capacity to disturb the metabolic activities, histological profile, and genetic structure and functions in aquatic species inhabiting the environment. The present study observed the karyological and histological alterations in gills of the freshwater fish, Mozambique tilapia, Oreochromis mossambicus in two different sublethal concentrations (1% and 3%) of heavy metals in 7, 15, and 30 days of experimental periods. The heavy metals induced various structural damages such as ring chromosome, sister chromatid exchange, acrocentric association region, condensed chromosomal morphology, heterochromatin region, and nucleolar organizer region in the chromosomes of O. mossambicus treated with 1% and 3% sublethal concentrations of water sample collected from Pallikaranai wetland ecosystem. Gills exposed to 1% and 3% effluent exhibited several variations in the respiratory surfaces of gill arches or lamellae in the light and scanning microscopical study. The gills exposed to 1% concentration for 30 days showed marked necrosis, and the secondary lamellae showed the lamellar membrane's dissolution. Exposure of gills to raw effluent in the field condition was observed in the presence of Cd, Pb, Cr, Cu, and Zn. Thus, this present study shows the environmental deterioration by heavy metal pollution on the structure of the gills in tilapia.

45S rDNA Repeats of Turtles and Crocodiles Harbor a Functional 5S rRNA Gene Specifically Expressed in Oocytes.

In most eukaryotic genomes, tandemly repeated copies of 5S rRNA genes are clustered outside the nucleolus organizer region (NOR), which normally encodes three other major rRNAs: 18S, 5.8S, and 28S. Our analysis of turtle rDNA sequences has revealed a 5S rDNA insertion into the NOR intergenic spacer in antisense orientation. The insertion (hereafter called NOR-5S rRNA gene) has a length of 119 bp and coexists with the canonical 5S rDNA clusters outside the NOR. Despite the ∼20% nucleotide difference between the two 5S gene sequences, their internal control regions for RNA polymerase III are similar. Using the turtle Trachemys scripta as a model species, we showed the NOR-5S rDNA specific expression in oocytes. This expression is concurrent with the NOR rDNA amplification during oocyte growth. We show that in vitellogenic oocytes, the NOR-5S rRNA prevails over the canonical 5S rRNA in the ribosomes, suggesting a role of modified ribosomes in oocyte-specific translation. The orders Testudines and Crocodilia seem to be the only taxa of vertebrates with such a peculiar rDNA organization. We speculate that the amplification of the 5S rRNA genes as a part of the NOR DNA during oogenesis provides a dosage balance between transcription of all the four ribosomal RNAs while producing a maternal pool of extra ribosomes. We further hypothesize that the NOR-5S rDNA insertion appeared in the Archelosauria clade during the Permian period and was lost later in the ancestors of Aves.

Genetic implications of a biological invasion: Chromosomal and DNA barcode monomorphism in Old World populations of Colorado potato beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

Once introduced into new area, invasive species can be expected to have low genetic diversity due to the founder effect. Here we tested this prediction using cytogenetic and molecular analysis of Armenian and Belarusian populations of Colorado potato beetle Leptinotarsa decemlineata (Say, 1824) and by comparing the results with those of native (North America) and those introduced into Europe. This revealed that the karyotype of males from Armenia and Belarus is remarkably conserved with 2n = 35 (34 + X0), n = 17AA + X0; and includes a pair of large acrocentric chromosomes. Thus, these populations belong to the so-called acrocentric chromosome race of the Colorado potato beetle. At diakinesis there are clearly visible argentophilic signals, probably NORs (the nucleolus organizer regions) present on some autosomal bivalents, while the X chromosome was homogenously argentophilic during different stages of meiosis. C-banding revealed a small amount of constitutive heterochromatin weakly visible in the pericentromeric regions of some chromosomes. Analysis of the DNA-barcode fragment of the gene cytochrome c oxidase subunit I (COI) revealed a single haplotype (we call it "the European haplotype") and lack of inter-population variability in all the samples collected from different locations in Armenia and Belarus. The comparison of our karyological and molecular data with that available in the literature and GenBank shows that all the populations studied from the Old World are monomorphic with respect to karyotype and the mitochondrial DNA-barcode. We assume that (1) the presence of acrocentric chromosomes in the karyotype and (2) the European haplotype of mitochondrial genome are the ancestral states for all populations in the Old World and inherited from the New World invaders who colonized Europe 100 years ago. New World populations are polymorphic with respect to karyotype and mitochondrial genes; however, the European haplotype has not yet been found in America. We believe that in the future it will be found in North America, which will shed light on the origin of populations of this dangerous pest in Eurasia.

May Argyrophilic Nucleolar Organizer Regions Be Used as a Biomarker for the Detection of the Degree of Ischemic Damage Instead of Tunel in Testicular Torsion?

Background and Objectives: It is of great importance to obtain information about the severity of ischemic damage and duration of testicular torsion for an effective treatment strategy. Nucleolar-organizing regions (NORs) are sites of the ribosomal genes composed of ribosomal DNA and proteins. Post-silver staining NORs are termed “AgNOR”. Since AgNORs clearly reveals the self-renewal potential of cells damaged in ischemic events, we performed the current study. Materials and Methods: The study was carried out in four groups as control, sham, early, and late T/D. In the surgical groups, testes were corrected after a 4-h ischemia period. Testicular tissue samples were taken on the third day after detorsion in group 1, 2, 3, and on the tenth day after detorsion in group 4. TUNEL and silver stainings were applied to all samples. Results: The differences were significant among the groups for both mean AgNOR number and total AgNOR area/total nuclear area (TAA/TNA). Moreover, the differences between control and early torsion-detorsion (T/D), between control and late T/D, between sham and early T/D, between sham and late T/D, and between early T/D and late were statistically significant for AgNOR amount. Furthermore, statistically significant differences among the groups for an average number of apoptotic cells per tubule and the percentage of apoptotic tubule values were detected. Discussion: The apoptotic index gives the ratio of cells that are damaged and will die in a programmed way and cells that remain intact, rather than show the viability of the returning testicle. However, by measuring cells that regenerate with AgNOR, we can show not only those that survive but also cells that can repair themselves. Conclusion: AgNOR proteins are usable for the early observation of ischemic injury levels. The amount of AgNOR protein can enlighten us about the extent of testicular damage after T/D treatment. It may also help the physician in the development of effective treatment strategies for cases.

Karyotype Record for the Morphologically Derived, Rarely Collected, Freshwater Fish Ellopostoma mystax (Cypriniformes, Cobitoidea, Ellopostomatidae)

Freshwater fishes of the superfamily Cobitoidea are a species-rich group that are present in virtually every river in Europe and Asia. Three of the nine recognized families show massive karyotype reconstructions, including several independent cases of polyploidy, indicating cytogenetic evolution correlated with their diversification. We herein present the karyotype of a member of the monogeneric family Ellopostomatidae, a very rarely collected and morphologically highly enigmatic Southeast Asian representative of the Cobitoidea. The analyzed specimen of Ellopostoma mystax from southern Thailand had a diploid chromosome number of 2n = 48, with karyotype composed of three pairs of metacentric (m), 19 pairs of submeta- to subtelocentric (sm, st), and two pairs of acrocentric (a) chromosomes. Six pairs of sm to st chromosomes bore CMA3-positive sites either in pericentromeric positions or formed CMA3-positive p arms of the carrier chromosomes. Nucleolar organizing regions (NORs) as visualized by silver (Ag) impregnation were situated on the entire length of the shorter arms of the second largest sm to st pair of chromosomes; these corresponding sites also stained CMA3-positive. When compared with other families of Cobitoidea, the karyotype of Ellopostoma reveals a rather plesiomorphic composition, suggesting that the strong derivation of Ellopostoma based on morphology only was not accompanied by a cytogenetic derivation.

Comparative Cytogenetics Analysis Among Peckoltia Species (Siluriformes, Loricariidae): Insights on Karyotype Evolution and Biogeography in the Amazon Region.

Peckoltia is widely distributed genus in the Amazon and Orinoco basins and the Guiana Shield, containing 18 valid species, and distinct morphotypes still needing description in the scientific literature due to its great taxonomic complexity. This study performed a comparative chromosomal analysis of two undescribed Peckoltia species (Peckoltia sp. 3 Jarumã and Peckoltia sp. 4 Caripetuba) from the Brazilian Amazon using conventional chromosome bands methods and in situ localization of the repetitive DNA (5S and 18S rRNA and U1 snRNA genes and telomeric sequences). Both species presented 2n = 52 but differed in their karyotype formula, probably due to inversions or translocations. The nucleolus organizer regions (NORs) showed distal location on a probably homeologous submetacentric pair in both species, besides an extra signal in a subtelocentric chromosome in Peckoltia sp. 4 Caripetuba. Heterochromatin occurred in large blocks, with different distributions in the species. The mapping of the 18S and 5S rDNA, and U1 snDNA showed differences in locations and number of sites. No interstitial telomeric sites were detected using the (TTAGGG)n probes. Despite 2n conservationism in Peckoltia species, the results showed variation in karyotype formulas, chromosomal bands, and locations of repetitive sites, demonstrating great chromosomal diversity. A proposal for Peckoltia karyotype evolution was inferred in this study based on the diversity of location and number of chromosomal markers analyzed. A comparative analysis with other Peckoltia karyotypes described in the literature, their biogeography patterns, and molecular phylogeny led to the hypothesis that the derived karyotype was raised in the left bank of the Amazon River.

Determination of the Relationship Among Cell Proliferation, Metabolic Activity and Stage of Pregnancy by AgNORs as Markers in Bovine Placenta

Nucleolus Organizer Regions (NORs) are defined as nucleolar components containing argyrophilic proteins selectively stained by silver methods (AgNORs). Several investigations have shown the AgNOR quantity and area represent a valuable parameter of cell kinetics, since they reflect the level of activity and cellular proliferation. This article addresses an evaluation of the functional activity and relation between days of pregnancy and proliferative capacity of trophoblastic mononucleate and binucleate cells from bovine placentomes. Both the number and size of AgNORs were determined in different phases of gestation by silver nitrate staining in conventional histological slides. The results showed a significant increase (from 1 to 12 AgNORs) in the number of AgNORS per trophoblastic mononucleate cell in the 3rd trimester, with predominance of 4-6 AgNORs/cell. In the 1st and 2nd trimesters, the number ranged between 1 and 9 AgNORs/cell, with predominance of 1-3 AgNORs. No significant differences were observed between the 2nd and 3rd trimesters, but in the first, in binucleate cells (19-27 and 10-18 AgNORs/cell, respectively) - this number was higher than the one registered in trophoblastic mononucleate cells in the same period. Thus, AgNORs can be used as markers of the proliferative placental cell cycle and established a relation between number of AgNORs and days of gestation. This relation can be used for diagnoses and prognoses of several placental pathologies, including pregnancy losses from manipulated embryos.