The number of silver-staining NORs (rDNA) in lymphocytes of newborns and its relationship to human development

Mild cognitive impairment is associated with low copy number of ribosomal genes in the genomes of elderly people

Introduction: Mild cognitive impairments (MCI) accompanying aging are associated with oxidative stress. The ability of cells to respond to stress is determined by the protein synthesis level, which depends on the ribosomes number. Ribosomal deficit was documented in MCI. The number of ribosomes depends, together with other factors, on the number of ribosomal genes copies. We hypothesized that MCI is associated with low rDNA CN in the elderly person genome.

Materials and Methods: rDNA CN and the telomere repeat (TR) content were determined in the DNA of peripheral blood leukocytes of 93 elderly people (61–91 years old) with MCI and 365 healthy volunteers (16–91 years old). The method of non-radioactive quantitative hybridization of DNA with biotinylated DNA probes was used for the analysis.

Results: In the MCI group, rDNA CN (mean 329 ± 60; median 314 copies, n = 93) was significantly reduced (p < 10^–15) compared to controls of the same age with preserved cognitive functions (mean 412 ± 79; median 401 copies, n = 168) and younger (16–60 years) control group (mean 426 ± 109; median 416 copies, n = 197). MCI is also associated with a decrease in TR DNA content. There is no correlation between the content of rDNA and TR in DNA, however, in the group of DNA samples with rDNA CN > 540, TR content range was significantly narrowed compared to the rest of the sample.

Conclusion: Mild cognitive impairment is associated with low ribosomal genes copies in the elderly people genomes. A low level of rDNA CN may be one of the causes of ribosomal deficit that was documented in MCI. The potential possibilities of using the rDNA CN indicator as a prognostic marker characterizing human life expectancy are discussed.

Evidence for nucleolar dysfunction in Alzheimer's disease

The nucleolus is a dynamically changing organelle that is central to a number of important cellular functions. Not only is it important for ribosome biogenesis, but it also reacts to stress by instigating a nucleolar stress response and is further involved in regulating the cell cycle. Several studies report nucleolar dysfunction in Alzheimer's disease (AD). Studies have reported a decrease in both total nucleolar volume and transcriptional activity of the nucleolar organizing regions. Ribosomes appear to be targeted by oxidation and reduced protein translation has been reported. In addition, several nucleolar proteins are dysregulated and some of these appear to be implicated in classical AD pathology. Some studies also suggest that the nucleolar stress response may be activated in AD, albeit this latter research is rather limited and requires further investigation. The purpose of this review is to draw the connections of all these studies together and signify that there are clear changes in the nucleolus and the ribosomes in AD. The nucleolus is therefore an organelle that requires more attention than previously given in relation to understanding the biological mechanisms underlying the disease.

Copy Number of Human Ribosomal Genes With Aging: Unchanged Mean, but Narrowed Range and Decreased Variance in Elderly Group

Introduction: The multi-copied genes coding for the human 18, 5.8, and 28S ribosomal RNA (rRNA) are located in five pairs of acrocentric chromosomes forming so-called rDNA. Human genome contains unmethylated, slightly methylated, and hypermethylated copies of rDNA. The major research question: What is the rDNA copy number (rDNA CN) and the content of hypermethylated rDNA as a function of age?

Materials and Methods: We determined the rDNA CN in the blood leukocyte genomes of 651 subjects aged 17 to 91 years. The subjects were divided into two subgroups: “elderly” group (E-group, N = 126) – individuals over 72 years of age (the age of the population’s mean lifetime for Russia) and “non-elderly” group (NE-group, N = 525). The hypermethylated rDNA content was determined in the 40 DNA samples from the each group. The change in rDNA during replicative cell senescence was studied for the cultured skin fibroblast lines of five subjects from NE-group. Non-radioactive quantitative dot- and blot-hybridization techniques (NQH) were applied.

Results: In the subjects from the E-group the mean rDNA CN was the same, but the range of variation was narrower compared to the NE-group: a range of 272 to 541 copies in E-group vs. 200 to 711 copies in NE-group. Unlike NE-group, the E-group genomes contained almost no hypermethylated rDNA copies. A case study of cultured skin fibroblasts from five subjects has shown that during the replicative senescence the genome lost hypermethylated rDNA copies only.

Conclusion: In the elderly group, the mean rDNA CN is the same, but the range of variation is narrower compared with the younger subjects. During replicative senescence, the human fibroblast genome loses hypermethylated copies of rDNA. Two hypotheses were put forward: (1) individuals with either very low or very high rDNA content in their genomes do not survive till the age of the population’s mean lifetime; and/or (2) during the aging, the human genome eliminates hypermethylated copies of rDNA.

Reduction of the argyrophilic nucleolar organizing region associated protein synthesis with age in buccal epithelial cells of healthy individuals

BACKGROUND

Nucleolus organizer regions (NORs) consist of the rRNA coding gene family (rDNA) in the cell nucleus. The argyrophilic proteins are selectively stained with silver nitrate and bind these regions. It was reported that NOR (rDNA) activity decreases in human lymphocytes, fibroblasts and bone marrow with age. However, to our knowledge there have not been any studies related to the NORs in oral epithelial cells of healthy individuals.

AIM

Our aim is to detect any correlation between age and Total AgNOR area/Total nucleus area (TAA/TNA) values in buccal epithelial cells of healthy individuals.

METHODS

Oral epithelial cells from 50 healthy individuals (age range of 2-80 years old) were spread onto a clean glass slide, air dried and fixed. Then the AgNOR staining protocol was performed on these cells. TAA/TNA ratio and AgNOR dots were calculated using software. From each person 50 oral epithelial cells were evaluated.

RESULTS

Statistically significant correlations were found between mean TAA/TNA values and age (Rsq = 0.534, p < 0.001 for linear and Rsq = 0.728, p < 0.0001 for polynominal regression), and between AgNOR number and age (Rsq = 0.621, p < 0.001 for linear and Rsq = 0.693, p < 0.0001 for polynominal regression).

CONCLUSION

There is a significant correlation between age and AgNOR amount (ribosome biosynthesis rate) in buccal epithelial cells of healthy individuals. AgNORs in buccal epithelial cells may be used for detection of age.

Aging Process in Chromatin of Animals

The aging process is a variable, stochastic and pleiotropic phenomenon which is regulated by different environmental and genetic factors. The age-associated changes, which occur at the molecular and cellular levels and disturb biological homeostasis, may directly or indirectly contribute to aging, causing apoptosis or cellular senescence and consequently leading to the death of the organism. In this context, it is particularly interesting to observe changes in somatic cell chromatin. In the present paper, we summarized the knowledge on the biological aspects of aging with special consideration of age-related changes in chromatin like DNA damage, shortening telomeres or age-related changes in methylation of DNA.

AgNOR status in Down's syndrome infants and a plausible phenotype formation hypothesis

Down's syndrome (DS) or trisomy 21 is the most frequent genetic birth defect associated with mental retardation. Although DS has been known for more than a 100 years and its chromosomal basis recognized for half a century (1959), the underlying patho-mechanisms for the phenotype formation remain elusive and cannot be fully explained by simple gene dosage effect. The general consensus is that the extra chromosome 21 genes perturb the global metabolism of the body cells. Our experiments show that the most prominent metabolic perturbation occurs during ribosome biogenesis in the cells of DS babies/infants. In humans, ribosomal RNA (rRNA) gene families or nucleolar organizer regions (NORs) are localized at the secondary constriction (on the satellite stalks) of five pairs of acrocentric chromosomes (13, 14, 15, 21 and 22) and their activities are evaluated specifically either in metaphase or interphase through a procedure known as AgNOR or silver staining. Our successive AgNOR studies, supported by RNA and nuclear protein measurement, show that cells from DS infants produce more ribosomes than expected, accounting for the extra set of active rRNA gene family (1/6-1/11) situated on the extra chromosome 21. Thus, the presence of an extra chromosome 21 stimulates a global increase in ribosome biogenesis in cooperation with other NOR-bearing chromosomes, causing unnecessary rRNA and ribosomal proteins synthesis compared to controls. Following the description of NORs, AgNOR, AgNOR-proteins, AgNOR measurement and our experimental results, we propose that the extra RNA and protein synthesis can cause a fundamental handicap to DS infants, contributing to the formation of DS phenotypes, due to the wasted energy in producing unnecessary macromolecules, including energy (GTP)-dependent transport of the excessive ribosomes from the nucleus to the cytoplasm.

Studies on argyrophilic nucleolar organizer regions (AgNORs) in a spontaneous mammary gland ductal carcinoma of a captive rhesus monkey

A spontaneous mammary gland ductal carcinoma was diagnosed in a 13-year-old female captive rhesus monkey (Macaca mulatta). The expression of argyrophilic nucleolar organizer regions (AgNORs) was studied to investigate the correlation between the histologic invasiveness and cell proliferation activity assay for predicting the biologic behavior of this tumor type. The results of this study show that the AgNOR size in tumor cells reflect the degree of malignancy when compared with the pattern of peripheral blood lymphocytes of the same individual. This is the first study showing a significant AgNOR feature of a malignant breast tumor in a rhesus monkey and it longs to provide additional diagnostic tool in tumor pathology.

Preferential loss of 5S and 28S rDNA genes in human adipose tissue during ageing

Loss of genomic rDNA has been associated with cellular and organismal ageing. The rDNA locus in humans comprises multiple copies of the 5.8S, 28S and 18S genes. Aim of the present study was to test the effect of aging on the copy number of the three rDNA genes individually in post-mitotic human tissue. We utilized real time polymerase chain reaction relative quantification to measure the copy number of 5.8S, 28S and 18S rDNA genes individually. We obtained adipose tissue from 120 male individuals aged from 9 to 94 years. The available data of each subject corresponding to the time of tissue sampling included: age, height, weight and calculated body mass index. Each rDNA gene was directly tested with Pearson correlation against age and body mass index. We found a significant negative correlation of the gene copy of 5.8S (P < 0.001) and 28S (P < 0.003) with age. Interestingly 18S gene copy displayed a different pattern with no statistically significant correlation with age. Conversely, we observed a significant negative correlation of the 18S gene copy with body mass index (P = 0.004) and a marginally non-significant negative correlation of the 5.8S (P = 0.097) gene copy with body mass index. In summary our results indicate that the rDNA recombination events in humans can be differentially targeted and regulated in response to ageing and/or fat accumulation. The proposed model generates possible implications regarding the effects of each rDNA gene loss in cell function as well as the mechanism of recombination targeting.

In memoriam Bernard Strehler--genomic instability in ageing: a persistent challenge

Genomic instability comprises a broad spectrum of mutational alterations in the genome, such as point mutations in DNA, microsatellite expansions or contractions, amplifications and deletions of DNA sequences, gene rearrangements and structural or numerical chromosomal aberrations. A substantial body of data demonstrates an increase of genomic instability during normal ageing. This includes cytogenetic changes; loss of rDNA; formation of extrachromosomal circular DNA species; loss of telomeric repeats; increased microsatellite instability; as well as point mutations and deletions in global nuclear and mitochondrial DNA. Evidence has accumulated supporting a causative role of genomic instability in ageing. Genomic instability can be counteracted by a number of proteins including antioxidant enzymes, the WRN protein (deficient in Werner syndrome), telomerase, poly(ADP-ribose) polymerase-1 and a range other others, as well as by multi-protein systems such as DNA mismatch repair, base-excision repair and nucleotide-excision repair. Important research tasks for the future will be to elucidate how and what extent the various expressions of genomic instability contribute to the ageing process and to understand the molecular mechanisms and regulation of the above factors and pathways involved in limiting the induction of ageing-associated genomic instability.

Age-related changes in cellular activity in human submandibular glands as evaluated by argyrophilic nucleolar organizer regions

OBJECTIVE

To examine the age-related changes in cellular activity of epithelial components of human submandibular glands, evaluated on the basis of argyrophilic nucleolar organizer regions (AgNORs).

DESIGN

Epithelial components of human submandibular glands were divided into serous acinar cells, mucous acinar cells, intercalated duct cells, striated duct cells, and interlobular duct cells. The mean AgNOR number of each cell type was compared among six age groups.

SETTING

The study was conducted at the Department of Oral Pathology, Tohoku University School of Dentistry, Japan.

SUBJECTS

Necropsy specimens from 66 males and 57 females 1 to 97 years old.

RESULTS

In all cell types except for intercalated duct cells, the mean AgNOR number was lowest in the 0-14 year-old group and highest in the 15-29 year-old group. The value then gradually decreased with advancing age and ultimately reached a similar level to that in the 0-14 year-old group. In intercalated duct cells, the mean AgNOR number did not differ significantly between any age group. There were no significant sex-related differences.

CONCLUSIONS

The cellular activity of almost all components of human submandibular glands rises in adolescence and young adulthood and then decreases with aging. These results suggest that intercalated duct cells are capable of not only proliferation but also division into other components; these cells may thus compensate for the reduced activity of other components in elderly subjects.

A comparative study of nucleolar organizer region, proliferating cell nuclear antigen and epidermal growth factor receptor staining in colon tumours

Several studies have reported that proliferating cell nuclear antigen (PCNA), nucleolar organizer regions (NOR) and epidermal growth factor receptor (EGF-R) are cellular proliferation parameters in malignant tumours. However, the correlation of EGF-R with PCNA and NOR has not been reported in colon tumours. To clarify this, we investigated the correlation of the expression of EGF-R with PCNA and NOR in colonic epithelial tumours. Using immunohistochemical staining and one-step silver staining techniques, the expressions of EGF-R-, PCNA- and NOR-associated protein were studied in paraffin sections from five normal mucosae, 10 adenomas with mild atypia, 16 adenomas with moderate atypia, 32 adenomas with severe atypia including carcinoma in situ and 47 with invasive colon carcinomas. Significant differences were found among the respective degrees of atypia in Ag-NOR counts, PCNA labelling index (LI), and the expression of EGF-R. However, there were no significant differences among the Ag-NOR counts of the severe atypia and invasive carcinoma. There was a significant positive correlation between Ag-NOR counts and PCNA LI (P < 0.001). The Ag-NOR counts and PCNA LI in EGF-R-positive cases were higher than in EGF-R-negative cases (P < 0.001). These results indicate that each of the parameters increased significantly with the increase in atypia and the progression of cancer. Epidermal growth factor receptor provokes an exacerbation of protein synthesis and the cell cycle in colonic epithelial tumours.

Localization of the genes for major ribosomal RNA on chromosomes of the house musk shrew, Suncus murinus, at meiotic and mitotic cells by fluorescence in situ hybridization and silver staining

The genes for major ribosomal RNA were localized on chromosomes 5pter-p15, 9q64-qter, and 13q38-qter of the house musk shrew, Suncus murinus (Insectivora, Soricidae) by silver staining of mitotic metaphase and meiotic pachytene spreads and fluorescence in situ hybridization using the human 28S-RNA genes as a probe to mitotic metaphase spreads. The data presented indicate a correlation between sites of in situ hybridization and silver staining. The finding of nuclear materials in mitosis was in a good agreement with observation in meiosis: same chromosomes carried active NORs in both meiotic and mitotic cells.

Prognostic value of nucleolar organizer regions in supraglottic carcinoma

The relationship of nucleolar organizer regions (NORs) to proliferative activity and tumor progression was studied in 16 supraglottic carcinomas. The number of NORs stained by a silver colloid staining method (AgNOR staining method) was determined. The mean AgNOR number tended to be higher (but not significantly so) in poorly differentiated tumors. Moreover as T and N categories and stage of the tumor rose, the AgNOR number also rose, but not significantly. More interestingly, the mean AgNOR number was significantly higher in the presence than in the absence of lymph node metastasis. These studies indicate that the AgNOR number might be of clinical value as a predictor of lymph node metastasis of supraglottic carcinomas.

Nucleolar organizer regions in glottic carcinomas: comparison of DNA cytofluorometry and clinicopathological analysis

The significance of nucleolar organizer regions (NORs) and nuclear DNA content in 73 glottic carcinomas was assessed for proliferative activity and tumor progression. NORs stained with silver colloid were counted, and nuclear DNA content was assayed by cytofluorometry. The cytofluorometric study demonstrated that the percentage of tumors with aneuploidy tended to increase as histological differentiation decreased. Survival rates of patients with diploid and aneuploid tumors were not significantly different. AgNOR staining revealed that mean AgNOR numbers rose as histological differentiation of tumors decreased. Moreover, as T and N categories and stages showed advancing malignancy, mean AgNOR numbers tended to rise. However, there was no significant difference in survival rates between tumors with low and with high AgNOR counts. These studies indicate that while AgNOR staining is better than DNA cytofluorometry for determining histological differentiation of glottic carcinoma, neither is of prognostic value at the present time.

Nucleolar organizer regions in tongue carcinomas induced in rats: comparison with DNA cytofluorometric analysis

Eleven papillomas and 25 carcinomas were induced in rat tongues by oral administration of 0.001% 4-nitroquinoline 1-oxide (4NQO) in drinking water, and the biological characteristics and proliferative activity of the tumors were investigated by both DNA cytofluorometry and the argyrophilic nucleolar organizer region (AgNOR) staining method. The histopathological characteristics, the mean number of AgNORs per cell and DNA ploidy patterns were compared. The mean AgNOR number was lowest in normal epithelium (1.65 +/- 0.10), and highest in squamous cell carcinomas (2.97 +/- 0.70) and intermediate in papillomas (1.87 +/- 0.28). The differences were statistically significant. All normal epithelium and all papillomas showed a diploid pattern. Eighteen (72%) of 25 squamous cell carcinomas showed a diploid pattern, while 7 (28%) showed a diploid plus tetraploid pattern. There was a significant difference in the mean AgNOR number between the two ploidy groups of squamous cell carcinomas. These results suggest that the mean AgNOR number may reflect the histological grade in the process of carcinogenesis and polyploidization of carcinomas.

The effect of vitamin A on the proliferation of oral epithelium in the rat

This study assessed the effect of topical and systemic 13-cis-retinoic acid on rat palatal epithelial proliferation with bromodeoxyuridine labelling and silver stained nucleolar organizer regions. Sixty male Wistar rats were assigned randomly to a control group or treatment groups of topical orabase, RA in orabase, 5 times/week or twice weekly systemic doses of 12 mg RA in coconut oil. The rats were treated for 1, 2, 4 or 8 weeks and killed 1 h post-injection of 40 mg/kg BrdUrd. The palatal mucosae were processed, using immunoperoxidase staining or silver stain to visualize BrdUrd utilization or AgNORs, respectively. The number of BrdUrd positive nuclei/mm overlying epithelium and number and area of AgNORs in the basal cells were assessed using image analysis. ANOVA indicated there was no significant effect of treatment on LN/mm or the numbers or areas of AgNORs. The LN/mm for the 8 w group (29.5) was significantly lower than the other groups. RA did not influence rat palatal epithelial proliferation, but across all groups increased age was associated with decreased proliferation. It would appear that the proliferation of normal oral mucosa may not be subject to altered proliferation when treated with therapeutic doses of topical or systemic RA.

Video image analysis of AgNOR distribution in the normal and adenomatous colorectum

The nucleolar organizer regions (AgNORs) have been studied by video image analysis in the normal colorectum and in adenomas arising there. Total AgNOR area was measured in conjunction with the total area of nuclei and expressed as a ratio. AgNORs are found to predominate in the proliferative regions of the normal mucosal crypt, and the ratio of AgNOR to nuclear area proved significantly greater in the normal colon than in the rectum and far greater in colorectal adenomas. Further, there is a significant difference between the ratio in tubular as opposed to villous patterns of adenomatous growth in the colon but not in the rectum. When classified according to their degree of dysplasia, adenomas in the rectum exhibit a significantly higher ratio of AgNOR to nuclear area as the degree of dysplasia increases in severity. This correlation is not shown in the colon.

Nucleolar organizer regions in prostate cancer

A silver colloid technique for the staining of nucleolar organizer regions (NORs) was applied to paraffin sections of 52 clinical prostate cancers, 5 incidental carcinomas of the prostate, 12 benign prostatic hypertrophy (BPH) specimens and 7 normal prostates. The mean numbers of silver-stained NORs (AgNORs) in these lesions were 3.12 +/- 0.52 in clinical cancer, 2.65 +/- 0.64 in incidental cancer, 1.66 +/- 0.16 in BPH, and 1.76 +/- 0.22 in normal prostate. There was a statistically significant difference in agNORs numbers between cancer and benign prostatic tissues (p < 0.001). However, no significant difference was observed in AgNORs numbers between incidental and clinical carcinoma of the prostate. In clinical cancer, only poorly differentiated adenocarcinoma showed a statistically larger number of AgNORs than the well or moderately differentiated group (p < 0.02). Correlation between AgNORs numbers and clinical stage was not obvious. There was no relationship between the number of AgNORs and serum values of tumor markers such as PAP, PSA and gamma-Sm. Moreover, the AgNORs numbers did not show a relation to decreasing rates of serum marker levels during successful anti-androgen therapy. If the patients with prostate cancer were divided into two groups by 2.9 of AgNORs number, the group with the smaller number of AgNORs (n = 14) was found to have a tendency towards a longer disease-stabilizing period than the larger group (n = 17).

Silver-stained nucleolar organizer proteins in chondrosarcoma

Silver-stained nucleolar proteins (AgNORs) were counted in primary chondrosarcomas of three histologic grades and in metastatic chondrosarcomatous lesions in the lung. The AgNOR numbers of neoplastic cells in primary tumors increased stepwise from grade 1 (4.42 +/- 1.11) through grade 2 (4.94 +/- 1.31) to grade 3 (6.97 +/- 1.10). There was a significant difference in AgNOR numbers between grade 3 and both grades 1 and 2 (p less than 0.001). Furthermore, the mean number of AgNORs in metastatic lesions (9.75 +/- 0.83) was significantly higher than that in primary sites (p less than 0.001). The number of AgNORs therefore reflects the grade of the chondrosarcoma. The results in the present study indicate that silver colloid staining is a useful technique for determining the histologic grade and evaluating the proliferative activity of chondrosarcomas.

Nucleolar organizer regions in the normal, hyperplastic and carcinomatous epithelium of endometrium

A silver colloid technique to identify nucleolar organizer region associated protein (AGNORs) has been applied to paraffin sections in a total of 43 endometrial hyperplasias (24 adenomatous and 19 adenocystic) 26 endometrial carcinomas and 22 normal endometria (11 of proliferative and 11 of secretory phase). A morphometric analysis of highly magnified photographic images of AGNORs in light microscopic preparations was performed. Malignant tumor cells showed significantly higher AGNOR numbers, maximum diameter and mean area compared with normal and hyperplastic endometrium, with the exception of adenocystic hyperplasia whose Dmax and mean area were significantly larger. Regarding the distribution pattern of AGNOR dots in the cases studied, it was found that normal and hyperplastic endometrium had a mainly clustered distribution while endometrial adenocarcinomas revealed a scattered one. The significant differences observed in the number of AGNORs, their size and mean area between benign and malignant endometrial epithelia suggest that the AGNOR staining technique is of diagnostic importance in distinguishing between these two groups.

Nucleolar organizer regions in various human brain tumors

Nucleolar organizer regions (NOR's) are loops of deoxyribonucleic acid (DNA) which transcribe to ribosomal ribonucleic acid (RNA) by RNA polymerase I. They possess vital significance in the ultimate synthesis of cellular proteins. A silver colloid staining technique for demonstration of NOR-associated proteins (Ag-NOR's) was applied to paraffin-embedded sections from 128 varied brain tumors and to chromosomal preparations from cultured brain-tumor cells. There was a statistically significant difference in the mean number of Ag-NOR's per nucleus between low-grade tumors (1.98/nucleus) and high-grade tumors (2.95/nucleus). It is suggested that the mean number of Ag-NOR's may represent the proliferative potential of brain tumors. Furthermore, high-grade tumors usually showed relatively large Ag-NOR's in a scattered distribution. In chromosomal preparations, the cultured cells displayed five to 12 Ag-NOR's on acrocentric chromosomes. Five of eight cell lines examined demonstrated ectopic Ag-NOR's. This simple staining technique can be easily applied to routinely processed paraffin-embedded sections and will become a useful tool for quick estimation of the proliferative potential of human brain tumors.

Nucleolar organizer region score and Ki-67 labelling index in high-grade gliomas and metastatic brain tumours

Sixteen cases of malignant brain tumours comprising 6 anaplastic astrocytomas, 3 glioblastoma multiforme, 1 medulloblastoma and 6 metastatic brain tumours were investigated independently by a silver colloid method for nucleolar organizer regions (NORs) and an immunohistochemistry using a monoclonal antibody against a nuclear antigen. Ki-67, in proliferating cells. The correlation between the mean number of NORs and the percentage of Ki-67 labelled cells (Ki-67 labelling index) was examined. In addition, four normal brain tissue samples without neoplastic cells were stained for NOR. The mean number of NORs in these malignant brain tumours was significantly greater than that in normal astrocytes (p less than 0.001). Moreover, both the mean number of NORs and the Ki-67 labelling index in metastatic brain tumours were significantly greater than those in high-grade gliomas (p less than 0.001). The Ki-67 labelling index and the mean number of NORs in malignant brain tumours including metastatic brain tumours were found to be linearly related (r = 0.86). These results suggest that the proliferative potential of malignant brain tumours could be evaluated by NOR score as well as Ki-67 labelling index and that such indices provide clear discrimination between high-grade gliomas and metastatic brain tumours.

Acrocentric interconnections and NOR variants in human lymphocytes

Acrocentric interconnections and NOR (nucleolus organizer region) variants are frequently observed in silver-stained metaphase preparations from lymphocytes of phenotypically normal individuals. The types of interconnections and of NOR variants are outlined. It is speculated that the satellite acrocentrics (both normal and variant) are the consequence of breakage and recoiling of these interconnections. Awareness of these two features of the human genome may facilitate understanding of the NOR/nucleolus interaction(s) in such important processes as nucleolus formation and in development and/or diagnosis of disease states (i.e., malignancy).

Proliferative potential of human brain tumours as assessed by nucleolar organizer regions (AgNORs) and Ki67-immunoreactivity

Two proliferation markers, silver stained nucleolar organizer regions (AgNOR) and immunoreactivity with Ki-67, were used to assess the proliferative activity in 80 smear preparations from neurosurgically removed intracranial tumours. These included 45 gliomas, 18 meningiomas, 8 metastases and 9 others. We found a remarkably close correlation between the results obtained with both methods. Increasing malignancy, as determined by conventional grading, was paralleled by an increase in the growth fraction and the number of nucleolar organizer regions. Linear regression analysis yielded the following equation: AgNORs/cell = 0.35 x L1 (Ki-67) + 3.24, with a correlation coefficient of rs = 0.53 (Spearman rank correlation test, p less than 0.0001). Thus, both the Ki-67 L1 and the AgNOR technique appear suitable for estimating the proliferative potential in smear preparations of human intracranial neoplasms. The AgNOR technique may be particularly useful for application to stereotaxic biopsies since it can easily be performed on minute tumour samples.

Intratubular germ cell neoplasia of the testis: identification by placental alkaline phosphatase immunostaining and argyrophilic nucleolar organizer region quantification

We assessed the value of placental alkaline phosphatase (PLAP) immunostaining and argyrophilic nucleolar organizer region (AgNOR) quantification as techniques for the identification of intratubular germ cell neoplasia (ITGCN), and compared them with hematoxylin-eosin and periodic acid-Schiff staining. We examined 46 malignant testicular germ cell tumors for the presence of ITGCN; 43 had sufficient tubules available for assessment. We also examined 16 cryptorchid testes, 16 testicular biopsies from 10 subfertile men, and 12 normal adult intrascrotal testes. In tubules adjacent to invasive tumors, hematoxylin-eosin staining identified 30 cases (70%) of ITGCN, while PLAP and AgNOR staining identified 36 cases (84%). All the seminomas (18) and 22 of 28 nonseminomatous germ cell tumors were PLAP-positive and had high AgNOR counts. Intratubular germ cell neoplasia was not identified in the other groups examined; germ cells in these groups were PLAP-negative and had low AgNOR counts. Cells of ITGCN showed cytoplasmic block positivity with periodic acid-Schiff staining but this was not a consistent finding. We conclude that ITGCN is present adjacent to most invasive germ cell tumors, and is reliably identified by hematoxylin-eosin staining when fully developed. Periodic acid-Schiff staining was not helpful as normal spermatogonia were also positive. Staining with PLAP and AgNOR were useful diagnostic adjuncts, but results with PLAP were easier to interpret.

Silver colloid staining technique for analysis of glioma malignancy

A silver colloid staining technique for identifying nucleolar organizer region-associated proteins (Ag-NOR's) was applied to 51 human gliomas. These comprised 20 glioblastomas multiforme, 15 anaplastic astrocytomas, and 16 astrocytomas, in which the mean numbers of Ag-NOR's per cell (+/- standard error of the mean) were 2.51 +/- 0.12, 2.01 +/- 0.10, and 1.76 +/- 0.06, respectively. Significant differences among these were recognized, and the mean number of Ag-NOR's paralleled the degree of histopathological malignancy. In 16 cases, studies were performed of the number of Ag-NOR's and the S-phase fraction by in vitro labeling using antibromodeoxyuridine monoclonal antibody. A linear relationship was demonstrated between these two factors (r = 0.857, p less than 0.001), although some scatter was seen. In 32 adult patients, the correlation between the number of Ag-NOR's and the prognosis was estimated. The results demonstrated that the group containing patients with less than 1.80 Ag-NOR's per cell had a better prognosis than the group with 1.80 Ag-NOR's or more. Thus, the number of Ag-NOR's reflected the degree of histopathological malignancy, S-phase fraction, and prognosis. Silver colloid staining for Ag-NOR's is a simple, rapid, and reproducible method for estimating the proliferative potential of human gliomas without requiring a complicated technique.

Molecular biology and respiratory disease. 3. Evaluation of nucleolar organiser regions in pulmonary pathology

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Silver staining of nucleolar organizer regions in malignant melanoma and melanotic nevi

The recently described method of staining nucleolar organizer regions (NOR) with colloidal silver nitrate was applied to the paraffin sections of five junctional nevi, 13 compound nevi, seven Spitz nevi, nine cellular blue nevi, 11 dysplastic nevi, seven malignant lentigines, 12 superficial spreading melanomas, and 14 secondary melanomas. There was a significant difference between the pooled silver-NOR (AgNOR) numbers of the 45 benign lesions (mean, 1.22; SD, 0.51) and the 33 melanomas (mean, 9.18; SD, 4.05) by t test analysis (P less than .01). The difference was striking enough to be recognized on casual microscopic examination, suggesting that AgNOR staining may be a useful technique to help separate melanocytic nevi from malignant melanomas.

Nucleolar organiser regions in pituitary adenomas

Nucleolar organiser regions have been identified by a silver-staining technique (AgNORs) and quantified in paraffin sections of normal foetal and adult pituitary gland and in a series of 35 pituitary adenomas, which included all the main types. In the adult pituitary there were 1.45 +/- 0.07 (mean +/- SEM) AgNORs per cell and in the foetal gland 2.94 +/- 0.37. The overall values for the adenomas were 1.98 +/- 0.08. Macroadenomas had significantly higher numbers (2.18 +/- 0.09) than microadenomas (1.69 +/- 0.11). Of the hormonally active tumours, corticotroph adenomas had the highest value (2.18 +/- 0.15), although four out of six were microadenomas.

Effects of age, sex and multiple endocrine neoplasia type-II on silver stained nucleolar organizer regions

Silver stained nucleolar organizer regions (AgNORs) were studied in phytohemagglutinin (PHA)-stimulated lymphocytes from 55 Caucasian control individuals (34 females with average age of 24 years and age range 19 weeks gestation to 87 years; 21 males with average age of 31 years and age range 29 weeks gestation to 72 years) and 13 individuals (7 females, 6 males; average age 38.8 years with age range 25-58 years) with multiple endocrine neoplasia-type II (MEN-II), an autosomal dominant malignancy with increased chromosome breakage. For the first time, AgNORs were examined in lymphocytes from normal fetuses and patients with MEN-II in order to determine the effects of age, sex or malignancy on the number of AgNORs. No significant difference in the average number of AgNORs were found in fetal cells (8.2 +/- S.D. 0.7/cell) when compared with cells from older individuals including those over 65 years of age (8.0 +/- S.D. 0.8/cell). There was a statistically significant negative correlation (P less than 0.05) between the modal number of AgNORs on G but not D chromosomes in both males and females. A negative correlation was also found between the mean number of AgNORs and age but was not statistically significant. The average number of AgNORs in the MEN-II individuals was 8.5 +/- S.D. 0.7/cell, which was not significantly different than 8.2 +/- S.D. 0.7/cell observed in age-matched control subjects.

A comparison of nucleolar organizer region staining and Ki-67 immunostaining in non-Hodgkin's lymphoma

Eighty cases of non-Hodgkin's lymphomas were examined independently using the monoclonal antibody Ki-67 and an argyrophilic method for the demonstration of nucleolar organizer regions. The evidence that Ki-67 immunoreactivity may be used as a marker of cell proliferation is described and the nature of nucleolar organizer regions reviewed. The proportion of tumour cells with nuclear Ki-67 immunoreactivity and the mean number of nuclear organizer regions are shown to be linearly related (r = 0.86, P less than 0.001) although some scatter was observed. These data suggest that the mean number of nucleolar organizer regions may reflect the cellular kinetics of a tumour. This study also provides further evidence supporting the thesis that the mean nucleolar organizer region score is related to the histological grade of non-Hodgkin's lymphoma. Ki-67 immunostaining and nucleolar organizer region staining would seem to provide comparable data, at least in non-Hodgkin's lymphoma, but the latter method has the advantage of being applicable to conventionally fixed and processed paraffin sections.

Correlation between DNA flow cytometric and nucleolar organizer region data in non-Hodgkin's lymphomas

The argyrophilic staining (AgNOR) technique, novel in histopathology, was applied to a series of 20 non-Hodgkin's lymphomas (NHL) of established Kiel subtype. The method demonstrates nucleolar organizer regions (NORs) by virtue of sulphydryl groups on their associated proteins and the enumeration of AgNOR foci has been previously shown to discriminate between NHL of low- and high-grade histological types. This finding was confirmed and the results were compared with those obtained by means of DNA flow cytometry performed on paraffin wax-embedded tissue from the same lymphomas. There was a very good linear correlation between the mean numbers of AgNOR sites per nucleus and the percentage of S-phase cells for each case, both values being high in high-grade NHL and low in low-grade lesions. Conversely there was no significant correlation between the DNA index, representing DNA aneuploidy, and AgNOR counts. It is suggested that the numbers of AgNORs in a lymphoma may be related to the dividing fraction of cells rather than, as might be expected, to ploidy alone. It is also proposed that the AgNOR technique, which is rapid, simple, and inexpensive, may provide, at least, an adjunct to DNA flow cytometry in the assessment of neoplasm in histopathology.

Genetic instability as the primary cause of human aging

The origins of aging of higher forms of life, particularly humans, is presented as the consequence of an evolved balance between 4 specific kinds of dysfunction-producing events and 4 kinds of evolved counteracting effects in long-lived forms. Among the deleterious events, particular importance is assigned to damage to DNA, but damage of a different kind than classical mutations. The evolution in man's ancestors of means to counteract the kinds of events that limit the life-spans of short lived mammals is postulated to be the indirect consequence of the prior evolution of superior mental capacities. Further, it is shown that the human species rapidly evolved its life-extending mutations because of the special circumstances afforded by the subdivision of the species into small semi-isolated (genetically) tribes of 10-100 individuals in which polygamy was the key factor in rapid incorporation of life- and well-being-extending new features. These conditions permit at least one or two orders of magnitude more of such beneficial genes to have been incorporated into our genomes during the 100,000 years or so of extremely rapid human evolution that evidently occurred about 100,000 to 200,000 years age than has been posited by other workers. The sources of damage to DNA are then considered, with special emphasis on free-radical derivatives of molecular oxygen and evidence is presented that longer lived forms of mammals have peroxide lysing enzymes that produce a lower steady state of damaging radicals derived from this compound. Evidence that so-called "classical" mutations cannot be the source of aging is then reviewed. A different kind of mutation, one that is not increased in proportion to point mutations by mutagens, namely deletion of tandemly duplicated copies of genes, is discussed and the evidence that such damage (gene loss) occurs in an amount sufficient to account for the major losses in function during aging is presented. The most likely mechanisms of such loss plus the prospects for evolving and bio-engineering means to counteract these losses together with some implications regarding the documented loss of NORs with age (as regards rDNA loss) together with key areas for intensive present and future research on aging are presented.