一例12号染色体臂间倒位的细胞遗传学研究

小麦主要经济性状大多属数量性状,是受 微效多基因控制的。为了探索小麦常用亲本配 制组合时各主要经济性状的遗传变异规律,于 1980年选用了江苏、浙江两省普遍采用的UP 301、泰山1号、908、早白、白壳早、短秆早6 个品种作为杂交亲本,研究并分析了主要经济 性状的遗传参数,为有效地选配亲本,提高育种 成效,提供一些理论依据。     

Evidence for a compensatory mechanism regulating Ag-NOR activity in families with de novo 21;21 translocation Down syndrome

Nucleolus organizing region (NOR) activity in seven probands with Down syndrome due to a de novo (21;21) translocation and their parents was analyzed on the basis of total Ag-NOR size per cell, mean Ag-NOR size per cell (Xc), mean Ag-NOR size per acrocentic (Xa), and the characteristic Ag-NOR number of each subject. The results showed intercellular variations in total Ag-NOR size per cell in all subjects, as well as interindividual variations in mean Ag-NOR size per cell. When the subjects were grouped according to their characteristic Ag-NOR number and the mean Ag-NOR size per cell for each group (GXc) and the mean Ag-NOR size per acrocentric for each group (GXa) were calculated, a number of interesting and significant correlations were found: (1) GXc correlated perfectly with the group's characteristic Ag-NOR number, (2) GXa varied inversely with the group's characteristic Ag-NOR number, and (3) GXc and GXa varied inversely with each other. These results suggest that if the Ag-NOR number of a cell decreases, the total NOR activity of the cell also decreases, but the NOR activity of its chromosomes increases. This finding supports the existence of a compensatory mechanism that regulates NOR activity on the cellular level.     

Visualization of nucleolar organizer regions in mammalian chromosomes using silver staining

A simple ammoniacal silver staining procedure, designated Ag-AS, differentially stains the chromosomal locations of ribosomal DNA in certain mammalian species. This was critically demonstrated by Ag-AS staining of the nucleolus organizer regions in karyotypes of the same species and cell lines used for locating the ribosomal cistrons by DNA/RNA in situ hybridization. With Ag-AS, silver stained NORs (Ag-NORs) are visualized as black spherical bodies on yellow-brown chromosome arms. Ag-NORs were visualized throughout mitosis at the secondary constrictions in the rat kangaroo, Seba's fruit bat, Indian muntjac, and Rhesus monkey. The Chinese hamster and cattle have telomeric Ag-NORs, the mouse subcentromeric Ag-NORs, and the field vole Ag-NORs as minute short arms or choromosomal satellites. Ag-NORs occur at both secondary constrictions and at telomeres in the cotton rat. Variability in Ag-NOR pattern included differences in the number of Ag-NORs per cell within a cell population, size of Ag-NORs among chromosomes of a complement, and presence of Ag-NOR on particular chromosomes in two cell lines of the Chinese hamster. The available cytochemical data suggest that the Ag-AS reaction stains chromosomal proteins at the NOR rather than the rDNA itself.     

Nucleolar organizing regions of human chromosomes

Summary Silver-Stained cells from 49 parents with a history of several abortions were compared with cells from 35 parents with normal liveborn children. The modal and mean number of silver-stained NORs (Ag-NORs) observed on D- or G-group chromosomes was similar in both groups and between males and females. Ag-NORs were randomly distributed on all five acrocentric pairs. The distribution and size of Ag-NORs within an individual was not random and was fairly consistent from cell to cell.The mean number of associations per cell was similar in both males and females of the abortion group and was less than the number of associations in controls. The probability of D- or G-group chromosomes being associated was near the expected probability of 0.6 for D-association and 0.4 for G-association. The frequency of association of any chromosome combination did not differ statistically from the expected values, though the number of associations, 15/22, was higher than expected.     

Nucleolar Organizer Regions In Pituitary Gland Adenomas

Nucleolar organizer regions are DNA segments concerned with the synthesis of ribosomal RNA (rRNA). Some specific proteins related to NORs can be demonstrated by a silver technique and are then referred to as Ag-NORs. The mean number of Ag-NORs per cell has been used as a marker of cell proliferation in recent years and there is some evidence to suggest that Ag-NOR counts can be used to differentiate between normal and neoplastic cells. Paraffin block sections of 42 pituitary gland adenomas and 24 normal adult pituitary glands have been examined using the Ag-NOR staining technique. Touch imprints of nine adenomas and 12 normal adult pituitary glands were also examined using the same Ag-NOR staining technique. Using light microscopy at x2000 magnification, the Ag-NORs were located as black dots in the cell nuclei and the mean number of Ag-NORs per cell was determined. No significant difference was observed between blocked sections and imprints of adenomas or between imprints and paraffin sections of normal glands. However, a significant difference was observed between the mean number of Ag-NORs in pituitary gland adenomas and normal glands in paraffin block sections and touch preparations (P less than 0.001). The modified Ag-NOR technique can be a useful aid in the differential diagnosis between normal pituitary gland tissue and pituitary adenomas, especially during surgical operations.     

Numerical variation of nucleolar organizer regions after silver staining in domestic and wild Suidae (Mammalia)

Selective silver staining was used to investigate the cellular distribution of numbers of nucleolar organizer regions (NORs) in domestic pigs (Sus scrofa) of eight different breeds, the European wild boar (S. scrofa scrofa), Indonesian wild boar (S. scrofa vittatus), Javan warty pig (S. verrucosus), Sulawesi warty pig (S. celebensis), and pigmy hog (S. salvanius). In the domestic pig as well as in the wild (sub)species of Sus, actively transcribing ribosomal RNA genes were found to be present in the secondary constrictions of chromosome pairs 10 and 8. Chromosomes 10 were consistently Ag-positive. Chromosomes 8 less frequently showed Ag-NORs, resulting in different mean numbers of Ag-NORs per individual animal. Mean Ag-NOR numbers per breed or (sub)species were generally higher in the wild representatives of Sus than in the domestic breeds. The highest mean numbers of Ag-NORs were observed in the Meishan breed and in S. celebensis and S. salvanius. The Meishan breed appears to be conservative in Ag-NOR staining pattern, being more comparable to the Asian wild Suidae than to the European breeds.     

Number and distribution of silver-stained nucleolar organizer regions and evolutionary relationships in domestic pigs

Variation in the numbers of silver-stained nucleolar organizer regions (Ag-NORS) were examined in 36 breeds of domestic pig of different geographic origins and five subspecies of wild boar. The relationship between Ag-NORs and evolution of domestic pigs was investigated. In all pigs observed, Ag-NORs were localized on the secondary constriction of chromosomes 10 and 8. The mean Ag-NOR numbers varied from 2.0–4.0, and decreased gradually with the different geographical distribution from south to north in China and from east to west in Europe. This regular change was caused mainly by the differences of frequency in chromosome 8 Ag-NOR type and was closely related to the evolution of domestic pig breeds.     

太平洋鳕染色体核型及银染分析

以野生太平洋鳕为材料,采用植物血球凝集素（PHA）及秋水仙素体内注射法,取头肾细胞经低渗、固定后,常规空气干燥法制备染色体标本,并对其染色体核型进行了分析。结果表明,太平洋鳕的二倍体染色体数目为2n=46,核型公式为:2n=8m+6sm+20st+12t,NF=60,即有4对中部着丝点染色体、3对亚中部着丝点染色体、10对亚端部着丝点染色体和6对端位着丝点染色体,染色体臂数为NF=60;染色体经银染后,Ag-NORs在不同间期细胞中表现出多态性,数目为13,其中2个Ag-NORs的频率最高（82%）;在分裂相中,具有1个Ag-NORs的频率最高（87.1%）,且在第12对亚端部着丝点染色体的一条带有明显的次缢痕,为Ag-NORs所在区域,并未发现Ag-NORs联合现象及性别相关的异型染色体。       

Chromosome banding in salmonid fish: nucleolar organizer regions in Salmo and Salvelinus

Chromosome banding patterns obtained by silver staining (Ag-NORs) were analyzed in three species of Salmo (rainbow, brown trout, and Atlantic salmon) and three species of Salvelinus (brook trout, lake trout, and arctic char). In rainbow trout and Atlantic salmon the Ag-NORs were found at the secondary constrictions of a single chromosome pair, while in brown trout the Ag-NORs were found on the short arms of one or two of the two longest subtelocentric or acrocentric chromosome pairs. The location of the Ag-NORs was multichromosomal in the three Salvelinus species, occurring on one or both members of four to six different chromosome pairs in different individuals. The Ag-NOR sites were on the short arms of some acrocentric pairs and at the telomeres of other acrocentric pairs and one or two metacentric pairs. Chromomycin A3 positive bands were found at the same sites as the Ag-NORs in all species. In the species with multichromosomal location of Ag-NORs, polymorphisms in the size and location of the NORs were extremely common, so that almost every individual fish had a different pattern of Ag-NOR sites.     

Activity of nucleolus organizer regions (NORs) in embryonic livers from twin minks]

Ag-NOR patterns were studied in hepatocytes from nine mink embryo siblings, including a pair of monochorionic (presumably monozygotic, MZ) twins. Both the number and the size of Ag-NORs per cell were found to be identical in MZ twins. All the other sibs had the patterns different from each other and from the MZ ones. The conclusion is that the NORs activity is a strongly inherited character and the Ag-NOR pattern can be used as a reliable genetic marker to distinguish the twin zygosity.     

Importance of interphase nucleolar organizer regions in tumor pathology

The importance of the distribution of silverstained nucleolar organizer regions (Ag-NORs) in interphase nuclei for diagnostic and prognostic purposes in tumor pathology has been reviewed. The available data demonstrated that interphase Ag-NOR evaluation may be of help in distinguishing malignant from hyperplastic or normal cells. On the other hand, there is increasing evidence that a relationship exists between the quantity of interphase Ag-NORs and the prognosis of malignant tumors: the greater the number of interphase Ag-NORs, the worse is the prognosis. This can be explained by the observation that the interphase Ag-NOR quantity is strictly related to the cell proliferation rate. The procedures used for the measurement of the interphase Ag-NOR quantity are also critically discussed.     

Importance of interphase nucleolar organizer regions in tumor pathology.

The importance of the distribution of silver-stained nucleolar organizer regions (Ag-NORs) in interphase nuclei for diagnostic and prognostic purposes in tumor pathology has been reviewed. The available data demonstrated that interphase Ag-NOR evaluation may be of help in distinguishing malignant from hyperplastic or normal cells. On the other hand, there is increasing evidence that a relationship exists between the quantity of interphase Ag-NORs and the prognosis of malignant tumors: the greater the number of interphase Ag-NORs, the worse is the prognosis. This can be explained by the observation that the interphase Ag-NOR quantity is strictly related to the cell proliferation rate. The procedures used for the measurement of the interphase Ag-NOR quantity are also critically discussed.     

银杏雌株染色体Ag-NOR的研究

本文以银杏雌株的幼小胚珠为材料,对其体细胞染色体进行了Ag-NOR染色研究。发现其Ag-NOR(随体)的数目均为4个,大小则有同形和异形两种类型。认为NOR(随体)的数目和形态不能作为性染色体的识别特征,并对NOR的杂合性和多态性进行了讨论。 Abstract:In this paper,the Ag-NOR of somatic chromosomes of young ovulum in Ginkgo biloba was studied.It was found that the number of Ag-NORs(satellite)were four constantly,though there were two kinds in size,homoeotype and heterotype.So we considered that the number and morphology of NOR(satellite)can not be used as identification markers of sex chromosome in Ginkgo biloba.In addition,the heterozygosity and polymorphism of NOR are discussed.     

Nucleolar organizing regions of normal Chinese hamster and CHW cell line chromosomes

The chromosome preparations from fibroblasts of normal male and female Chinese hamsters and the cell line CHW were stained with AgNO3. The silver stain was usually localized at the telomeres of autosomes. The marker chromosome M1 in the CHW cell line has Ag-NOR near the centre of the long arm, which indicates that either the long arms of two number 5 chromosomes fused at the telomeres or the intact telomeric region of one chromosome fused with one with a deleted telomere. The variation of Ag-NORs' number per cell and Ag-heteromorphism in chromosome number 4 were observed. The Ag-NORs of chromosome number 4 and 5 are in approximately the same position as the positive C-bands and these may play a role in the preservation of heterochromatin.     

鼷鹿云南亚种（Tragulus javanicus williamsoni）的核型分析

本文以染色体分带技术,发现鼷鹿云南亚种的染色体数目为2n=32。全部为双胃染色体,NF=64。所有染色体着丝点区分布有C带,多数染色体的端部或两端也有C带。某些染色体还有插入C带。Y染色体C带阳性,有一Ag-NORs。文章对鼷鹿云南亚种染色体独特的C带分布以及和核型进化的关系进行了讨论。     

Recent chromosome diversification in the evolutionary radiation of the freshwater fish family Curimatidae (Characiformes)

Neotropical Curimatidae fishes include 97 species in eight genera. Basic cytogenetic studies show a karyotype of 2 n = 54 chromosomes in most species. Karyotype divergence of the nucleolus organizing regions between species has been reported, and these regions appear to be good cytotaxonomic markers. In the present work, karyotype, heterochromatin and Ag-NOR variability in 13 species were investigated to analyse the chromosome diversification in view of the biogeographic history of this group. Only Cyphocharax platanus showed a karyotype with 2 n = 58 chromosomes. Ag-NOR and C-banding patterns were quite divergent among the species studied. All species whose C-bands were analysed had heterochromatic blocks associated with the nucleolus organizing regions. Species with multiple Ag-NORs also showed an increase in NOR-associated heterochromatic blocks. C-banding showed considerable differentiation among species, revealing a pronounced chromosome diversification in this group. Karyotypic variability corroborates the hypothesis that these fishes in Amazon region show various discrete patterns of species endemism. Chromosome diversification in curimatids has a recent origin and appears to be accompanying the post-Andean speciation responsible for the diversity of species in the family.     

Differential rRNA Genes Expression in Hexaploid Wheat Related to NOR Methylation

Ribosomal RNA genes expression was analysed in 18 Portuguese bread wheat accessions (Triticum aestivum L. em Thell.), and the number of argyrophilic-nucleolar organiser regions (Ag-NORs) per cultivar was scored. Ten accessions presented six Ag-NORs per metaphase and six nucleoli per interphase, and eight accessions presented four Ag-NORs per metaphase and four nucleoli per interphase. Fluorescent in situ hybridisation with the 45S rDNA sequence pTa71 and genomic DNA from Aegilops tauschii (2n = 2x= 14, DD) confirmed the Ag-NOR location and identified the six satellited chromosomes as being the chromosome pairs 1B, 6B and 5D. The methylation pattern of the NOR region was studied by Southern blot using pTa71 as probe, which represented a complete rDNA unit of bread wheat. DNA digestions performed by MspI and HpaII resulted in different patterns revealing the high level of cytosine methylation at their recognition sequences. The total percentage values of NOR methylation indicated that wheat accessions with a maximum of four Ag-NORs were more heavily methylated at the NOR region than accessions with a maximum of six Ag-NORs.     

Characterization of yellow grouper Epinephelus awoara (Serranidae) karyotype by chromosome bandings and fluorescence in situ hybridization

The cytogenetics of yellow grouper Epinephelus awoara was studied using multiple cytogenetic markers [Giemsa staining, C-banding, Ag-NORs and fluorescence in situ hybridization (FISH)]. Giemsa staining results showed that the karyotypic formula of E. awoara was 2n = 48a, FN (fundamental number) = 48. Faint C-bandings were only detected at the centromeric regions of chromosome pair number 24, being almost indiscernible on the other chromosome pairs. After Ag-NOR staining, one pair of nucleolar organizer regions (NOR) was observed in the subcentromeric region of pair number 24. FISH results showed that 5S rDNA was located at a pair of medium-sized chromosomes, while 18S rDNA appeared at the same location in the subcentromeric region of pair number 24 where Ag-NORs were detected. The telomeric sequence (TTAGGG)(n) detected by FISH was located at both ends of each chromosome. The results suggested that E. awoara has retained general karyotypic structure stability during the evolutionary diversification process.     

三个家猪品种和rob易位群染色体分带多态性的比较

对家猪不同品种及家系间的染色体组型、C－带、Ag－NORs多态性进行的研究表明：杜洛克猪、约克夏猪、长白猪体细胞染色体数2n＝38,核型2n＝10sm＋12m＋4st＋12t,而13／17易位纳合子猪（36,rob．13／17）的体细胞染色体数2n＝36,核型2n＝10sm＋12m＋6st＋8t;13／17易位杂合子猪（37,rob．13／17）的体细胞染色体数目为2n＝37,核型为2n＝10sm＋12m＋5st＋10t。5种家猪的C－带在13～18号染色体上存在大、中、小三种类型,且呈多态性分布。杜洛克猪、约克夏猪、长白猪、13／17易位纳合子猪、13／17易位杂合子猪的Ag－NORs均数分别为2．05、2．062．00、1．99、1．98,说明Ag－NORs在品种、个体及细胞间具有多态性.