Expression Of Nucleolar Organizer Regions Research Articles

Curcumin-mediated decrease in the expression of nucleolar organizer regions in cervical cancer (HeLa) cells

Curcumin, the major yellow-orange pigment of turmeric derived from the rhizome of Curcuma longa, is a highly pleiotropic molecule with the potential to modulate inflammation, oxidative stress, cell survival, cell secretion, homeostasis and proliferation. Curcumin, at relatively high concentrations, was repeatedly reported to be a potent inducer of apoptosis in cancer cells and thus considered a promising anticancer agent. In the present paper, the effects of low concentrations of curcumin on human cervical cancer (HeLa) cells were studied. We found curcumin-mediated decrease in the cell number and viability, and increase in apoptotic events and superoxide level. In contrast to previously shown curcumin cytotoxicity toward different cervical cancer lines, we observed toxic effects when even as low as 1μM concentration of curcumin was used. Curcumin was not genotoxic to HeLa cells. Because argyrophilic nucleolar protein (AgNOR protein) expression is elevated in malignant cells compared to normal cells reflecting the rapidity of cancer cell proliferation, we evaluated curcumin-associated changes in size (area) and number of silver deposits. We showed curcumin-induced decrease in AgNOR protein pools, which may be mediated by global DNA hypermethylation observed after low concentration curcumin treatment. In summary, we have shown for the first time that curcumin at low micromolar range may be effective against HeLa cells, which may have implications for curcumin-based treatment of cervical cancer in humans.

Cadmium-induced changes in genomic DNA-methylation status increase aneuploidy events in a pig Robertsonian translocation model

Although cadmium is a well-established human carcinogen, the mechanisms by which it induces cancer are poorly understood. It is suggested that cadmium-mediated carcinogenesis may include the modulation of gene expression and signal-transduction pathways, interference with antioxidant enzymes, inhibition of DNA repair and DNA methylation, and induction of apoptosis. Nevertheless, no predominant mechanism playing a role in metal-induced carcinogenesis has been reported. In the present study, we used a pig Robertsonian translocation model, which is a cross between a wild boar and domestic pig resulting in Robertsonian translocation (37,XX,der15;17 or 37,XY,der15;17), to determine the role of cadmium sulfate in the modulation of genomic DNA-methylation status and the induction of aneuploidy. We found a cadmium-mediated increase in aneuploidy within chromosome group A and C, but not within chromosome group D containing the translocated chromosome der15,17 which indicates that translocated chromosome is not more prone to chromosomal aberrations than are other chromosomes. We suggest that cadmium-induced aneuploidy (up to 5-μM concentration) may be mediated by global DNA hypermethylation as monitored with HPLC and 5-mdC immunostaining. In addition, the cyto- and genotoxic potential of cadmium was evaluated. Cadmium sulfate was able to induce apoptosis, inhibit cell-proliferative status and expression of nucleolar organizer regions (NORs), and increase oxidative DNA damage (8-oxoG content).

Oxidant-induced decrease of the expression of nucleolar organizer regions in pig lymphocytes can be useful for monitoring the cellular effects of oxidative stress

The technique of silver staining of nucleolar organizer regions (AgNORs) was chosen to estimate the transcriptionally active metaphase and interphase nucleolar organizer regions (NORs) in pig peripheral blood lymphocytes exposed to oxidative agents in vitro. The quantitative analysis of AgNORs was performed by using the counting method and the morphometric method. We found that hydrogen peroxide and 2,2′-azobis-(2-amidinopropane)-dihydrochloride (AAPH) induced a concentration-dependent decrease in NORs activity – in the case of metaphase the NORs activity was exclusively seen on chromosome pairs 8 – which can be considered as another estimate of cellular oxidative stress. Moreover, biomarkers of cyto- and genotoxicity, such as the percentage of apoptotic and necrotic cells, the nuclear division index (NDI) and formation of micronuclei (MN) were used to measure harmful effects provoked by the agents tested.

The activity of nucleolar organizer regions of human bone marrow cells studied with silver staining. II. Acute leukemia

The activity of nucleolar organizer regions (NOR) in chromosomes and interphase nuclei of bone marrow cells from 11 adult patients with acute lymphoblastic leukemia (ALL), 35 patients with acute nonlymphoblastic leukemia (ANLL), and eight healthy donors has been studied with silver nitrate staining. PHA-stimulated lymphocytes of the same individuals were used as standards of the maximum silver-staining patterns for each person. In 90% of patients with acute leukemia the average number of Ag+NOR in metaphases was lower when compared with that of PHA-stimulated lymphocytes. A variable expression of NOR was observed within the cell population and between individual patients. The populations tested showed high heterogeneity in relation to the content of Ag-negative mitoses. Ag+NOR per metaphase and the content of Ag-negative mitoses in bone marrow did not differ between patients with ALL and ANLL. Differences in the staining pattern in leukemic cells are discussed.

Expression of ribosomal cistrons of human chromosomes at high resolution.

The expression of ribosomal cistrons in the nucleolar organizer regions (NORs) has been studied with high resolution banding in the acrocentric chromosomes of 10 normal individuals. It was found that if a particular chromosome did not stain with silver nitrate at metaphase, then it did not stain at prophase either. Therefore, it is concluded that some of the acrocentric chromosomes have variable expression of NORs.

Nucleolar organizer regions inBiomphalaria andBulinus snails

A method is described for the demonstration of nucleolar organizer regions (NORs) in freshwater snails and is applied to the study of one tetraploid and several diploid populations ofBulinus. We present evidence of dosage compensation with respect to the expression of NORs in that diploids and tetraploids both exhibit only 1 pair of NOR-bearing chromosomes.