Nalan Imamoglu

Condensed chromatin surface and NORs surface enhancement in mitogen-stimulated lymphocytes of Down syndrome patients

Mitogen-stimulated lymphocytes of 20 Down syndrome (DS) patients with regular trisomy 21 contain more condensed chromatin surface (11.28 +/- 2.64 % of the total nuclear surface: mean +/- SD) and more nucleolus organiser regions surface (13.21 +/- 3.45 %) than that of 12 healthy controls: (8.84 +/- 2.23 and 9.12 +/- 2.33 %, reciprocally). The source of this peculiarity has been investigated. A computer program was designed for the planimetric measurement of the condensed chromatin surface (CCs)/ total nuclear surface(TNs) and the nucleolus organiser regions surface (NORss) /TNs proportions in interphase nuclei. CCs/TNs and NORss/TNs of 100 maximally activated nuclei (MANs) were measured for each patient and control case. The difference was found highly significant (P<0.01). Nuclei with a diameter of >/= 17 micrometer measured on the slide (in flattened state) were considered as maximally activated nuclei (MANs). NORss/TNs enhancement and fluorescent in situ hybridisation (FISH) studies in MANs of DS patients indicate that this phenomenon is due to the over-expression (or lack of downregulative mechanism) of NORs (rDNA) to some extent, including the NOR of the supernumerary chromosome 21. No statistical difference was observed between 12 healthy controls and 5 Robertsonian translocation type of DS Patients (where the two involved NORs are missing) when the two parameters were considered.

Evaluation of the Nucleolar Organizer Regions in Alzheimer’s Disease

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder in middle and late age. Ribosomal RNA (rRNA) genes are located in the nucleolus (nucleolar organizer regions = NORs). There are increased deposits of β-amyloid protein in the brains of the patients with AD and aged individuals with Down’s syndrome (DS). The β-amyloid gene is located in the acrocentric chromosome 21 that is responsible for rRNA synthesis. Therefore, it is possible that there is a relationship between ribosomal genes and AD. Objective: To investigate the activities of ribosomal genes of AD patients by comparing the activities of NORs in AD patients and healthy controls with the silver-staining method. Methods: NOR surface/the total nucleus surface proportions in interphase nuclei, and silver stainability and satellite association (SA) of acrocentric chromosomes in the metaphases of cultivated lymphocytes of 20 AD patients and 20 healthy controls (10 elderly and 10 young) were evaluated. Results: A decrease in NOR surface/total nucleus surface proportions has been observed in the interphase nucleus of AD patients when compared with elderly controls (p = 0.035). When compared with the sizes of Ag+ segments of acrocentric chromosomes of AD patients and control groups, the Ag-staining size 1 of the chromosome 22 of AD patients was found to be more increased than that of the young controls (p = 0.018). There was no statistically significant difference between AD patients and control groups regarding the number of Ag+ acrocentric chromosomes, Ag+ chromosome 21 and SA frequency (p > 0.05). It has been found that there is only a slight increase in the total number of chromosomes in SA in AD patients when compared with elderly controls (p = 0.05). Conclusion: The decrease in NOR surface/total nucleus surface proportions of AD patients may indicate a reduction in the activity of the ribosomal genes of these patients.

NOR expression increases on metaphase chromosomes of down syndrome lymphocytes in concordance with mitogen concentration in culture medium

Regulation of nucleolus organizer region (NOR) expression in trisomy 21 (Down syndrome [DS]) cells is not fully explained. This work compared NOR expression on metaphase chromosomes in gradiently stimulated lymphocytes from DS patients with those from healthy controls.

Investigation of micronucleus frequencies in lymphocytes of inhabitants environmentally exposed to chrysotile asbestos

Abstract Exposure to asbestos minerals has been associated with a wide variety of adverse health effects including lung cancer, pleural mesothelioma, and cancer of other organs. Many of the regions of Turkey have asbestos deposits. People in Doğanlı village – one of these regions – have been environmentally exposed to chrysotile asbestos since they were born. In this study the effects of asbestos on micronucleus (MN) frequencies of inhabitants exposed to chrysotile asbestos have been examined. Thirty subjects who had been environmentally exposed to chrysotile asbestos and living in Doğanlı village, and 25 controls were studied to assess the MN frequency. The control group was selected from healthy individuals with no exposure to asbestos and living in similar geographic conditions to Doğanlı village. Peripheral blood samples were collected from each subject and cultured for MN assay. Cytochalasin-B was added to lymphocyte cultures for evaluation of MN in binucleated (BN) cells. The differences between those exposed to chrysotile asbestos and controls were not statistically significant in terms of BN cells with MN (p > 0.05). There was not a significant relationship between MN frequencies and age, sex, smoking, both in chrysotile asbestos-exposed subjects and in controls (p > 0.05). Although the detection of calcified pleural plaques found in the inhabitants has indicated environmental exposure to chrysotile asbestos, our results show that chrysotile asbestos was not an inducer of MN in subjects exposed to chrysotile asbestos.

Age-Dependent Decreases in Mitogen-Stimulation Level and RNA Content in Peripheral Blood Mononuclear Cells of Down Syndrome Patients

The aim of the present study was to determine whether or not the phytohemagglutinin (PHA)‐activated proliferation and average RNA content in peripheral blood mononuclear cells (PBMC) of Down syndrome (DS) patients change with age.

Increased micronucleus frequency after oral administration of cadmium in dogs.

Cadmium (Cd) is a toxic heavy metal that has been classified as a human carcinogen by the International Agency for Research on Cancer. The genotoxic effects of cadmium oxide (CdO) were investigated in cultured dog lymphocytes after a short-term oral CdO administration by the micronucleus (MN) test. The dogs were given 10 mg CdO/kg body weight per day for 3 and 28 d, respectively group I (n=7) and group II (n=6). Blood samples were collected at the beginning of feeding and at 4 and 29 d after Cd administration and cultured for 72 h. Whereas no significant increase in the MN frequency in group I was observed (p=0.398), a significant MN induction with CdO was found in group II (p=0.028) when compared with initial MN frequencies of dogs in both groups. Our results suggest that CdO might be directly and/or indirectly genotoxic after a monthly oral administration of CdO in dogs.

Nuclear AgNOR protein enhancement in nucleoplasms of peripheral blood lymphocytes of babies/children with Down syndrome.

Down syndrome (DS) is one of the most common chromosomal disorders. The factors contributing to the mental retardation together with other defects in this syndrome have not been fully explained. Individuals with DS have extra rRNA gene family since they carry an extra chromosome 21. The few reports available are on the relationship between the nucleolus organizer regions (NORs) and DS phenotype. The in vivo regulation of NORs expression on the extra chromosome 21 is not completely understood. Previous studies have shown that nucleoli of lymphocytes from infants (mostly neonates) with DS contain more in vivo and in vitro nucleolar AgNOR proteins when compared with healthy infants. The objective of this study is to compare the in vivo nuclear AgNOR protein level in nucleoplasms (also called as karyoplasm) of nonstimulated peripheral blood lymphocytes from babies/children with DS and healthy controls. Peripheral blood samples obtained from 20 babies/children with DS and 20 matched healthy controls were smeared on clean glass slides and then AgNOR staining was performed. The AgNOR protein level in nucleoplasms of lymphocytes from both groups was calculated using a computer program. Nearly 100 interphase nuclei per individual were analysed. Average nuclear AgNOR protein levels in nucleoplasms of lymphocytes from babies/children with DS were found to be significantly higher than those of the controls (P < 0.001). On the basis of our present results, we propose that the increase of nuclear AgNOR protein in in vivo conditions may contribute to the formation of DS phenotypes. Microsc. Res. Tech. 79:133–139, 2016.

THE IMPORTANCE OF NUCLEOLAR ORGANIZER REGIONS IN PEDIATRIC ACUTE LYMPHOBLASTIC LEUKEMIA

The silver-staining of the nucleolar organizer regions (AgNORs) was performed in patients with acute lymphoblastic leukemia (ALL) to verify the role of cell proliferation in predicting complete remission and survival. Bone-marrow aspiration smears of 20 pediatric cases with ALL were stained with argyrophilic method during the diagnosis, remission, and 3rd, 6th, 9th, and 12th months after remission. The mean NORs count (NORsc) and the mean of (nucleolar organizer regions surface/total nuclear surface × 100) value (NORss/TNs) for each case were calculated. At diagnosis, the NORsc and NORss/TNs value for the whole series were 3.30 ± 0.86 and 4.77 ± 1.15, respectively. In complete remission, NORsc and NORss/TNs values were 1.23 ± 0.20 and 3.45 ± 0.87, respectively and the differences were statistically highly significant (p <. 001). The most important parameters of prognostic factors that effect diagnosis NORss/TNs and NORsc values were found to be FAB morphology and leukocyte count according to the multivariant analysis test. AgNORs analysis is a suitable method to assess cell proliferation in bone marrow aspirate and can predict complete remission, remission duration, and survival in pediatric ALL patients.