洋葱细胞核仁内DNA的结构变化及排布过程(英文)

以洋葱 (AlliumcepaL .)细胞为研究材料 ,应用DNA细胞化学特异染色方法 (NAMA_Ur)及常规电子显微镜技术 ,观察了洋葱细胞核仁FC(纤维中心 )内DNA的超微结构 ,发现FC内DNA存在着一个介于集缩到解集缩之间的变化过程 ,并揭示了DNA在核仁内的连续排布过程 ,即核仁外DNA经过核仁通道进入到FC后 ,继续沿FC的边缘或DFC(致密纤维成分 )与FC的交界处环绕FC而排布 ,再经FC之间的核仁通道 ,延伸到另外的FC区域     

The Structural Transformation of Nucleolar DNA and Its Arrangement in Nucleolus of Allium cepa Cells

By using the DNA specific cytochemical staining method (NAMA-Ur) and conventional electron microscopic technique, the authors examined the configuration of intranucleolar DNA in Allium cepa L. cells and found that nucleolar DNA within the fibrillar center (FC) underwent a structural transformation process from condensed to extended state. The authors' observations also displayed a continuous arrangement process of nucleolar DNA, i.e., the extranucleolar DNA entered FC through the nucleolar organizer region (NOR) channel, then extended to the periphery of FC or to the border between FC and dense fibrillar component (DFC), and distributed along the periphery of FC. Thence, by passing through the NOR channel between FCs, the nucleolar DNA continued to transfer to other FCs and arranged in the same above-mentioned forms.     

小麦细胞核仁中DNA原位位置与rRNA基因转录位点的研究

以小麦细胞为研究材料, 应用常规电子显微镜技术和DNA细胞化学特异染色NAMA-Ur技术, 在原位水平对核仁中DNA的分布和特征进行了直观的观察。结果表明, 小麦细胞核仁中DNA位于纤维中心(Fibrillar Centers, FC)、致密纤维组分(Dense Fibrillar Component, DFC)以及两者的过渡区域, 并呈现出环绕FC排布的构型; 应用RNP优先染色(Benhard staining)技术分析了核仁中RNP的分布及其原位位置, 直观的显示了小麦细胞核仁中RNP颗粒主要集中在 FC与DFC的过渡区域及DFC和颗粒组分(Granular Component, GC)中; 并且在FC与DFC的过渡区域, 它们不太均匀也不太连续地半围绕着FC而排布; 进一步借助于RNA/DNA杂合体抗体在原位水平标记和分析了细胞核仁中活跃基因转录的精细位点, 结果表明小麦细胞核仁rRNA基因的转录位点位于FC与DFC的过渡区域及DFC中。     

豌豆细胞核仁中rDNA的超微定位和排布构型

利用细胞化学DNA特异染色法——NAMA-Ur特异染色法对豌豆细胞核仁中rDNA的位置及其排布构型进行了原位观察。结果表明,核仁中的rDNA位于纤维中心(FC)以及FC与致密纤维组分的交界处,以环绕FC的形式排布。不同位置的rDNA成分都具有集缩和解集缩两种形态结构,核仁外的核仁伴随染色质经过核仁通道进入核仁,沿FC周边排列,与其中的DNA相连。     

豌豆细胞核仁中rDNA的超微定位和排布构型

利用细胞化学DNA特异染色法——NAMA-Ur特异染色法对豌豆细胞核仁中rDNA的位置及其排布构型进行了原位观察。结果表明,核仁中的rDNA位于纤维中心(FC)以及FC与致密纤维组分的交界处,以环绕FC的形式排布。不同位置的rDNA成分都具有集缩和解集缩两种形态结构,核仁外的核仁伴随染色质经过核仁通道进入核仁,沿FC周边排列,与其中的DNA相连。     

Subnucleolar distribution and organization of Vicia faba L. rDNA in situ

The distribution and organization of nucleolar DNA in Vicia faba L. was analyzed by specific cytochemical staining using NAMA-Ur. The results showed that nucleolar DNA was distributed in the FCs and at the FC/DFC junctions. Statistical analysis showed that the rRNA genes occupied about one-third of the total dense fibrillar component region. The rDNA was condensed in some regions and uncondensed in others. Nucleolus-associated chromatin extended from outside the nucleolus to the periphery of the FCs via nucleolar channels, suggesting a possible origin for nucleolar DNA.     

Studies on changes in nucleolar organizer region of human promyelocytic leukemia cells (HL-60) treated with retinoic acid

Changes of nucleolar organizer region in HL-60 cells after treated with retinoic acid (RA) were studied with techniques of silver-staining nucleolar organizer region (Ag-NOR) in metaphase karyotypes, Brachet's reaction and with our improved TEM techniques for studying silver-stained active nucleolar organizer region (Ag-aNOR) in interphase nucleoli. Number of Ag-NOR in HL-60 cells is 4.5/cell on average. The Ag-NOR number of cells treated with RA showed no remarkable difference from that of control group. Ag-aNOR number treated with RA was reduced obviously as compared with that of control group. Meanwhile, the changes of nucleolus number showed by Brachet's reaction were in accordance with those of Ag-aNOR. Therefore, it may be concluded: (1). Though the number of active rRNA genes did not changed after the differentiation of HL-60 cells induced by RA, their expression was clearly inhibited: (2). The relationship between the changes of Brachet-No and Ag-aNOR is in positive correlation (r = 0.98, p less than 0.01). EM examination of Ag-aNOR of HL-60 cells reveals that Ag-protein (RNA polymerase I) only presented in fibrillar centers (FC) and the dense fibrillar components (DFC) of nucleolus. In addition, in control group, large amount of Ag-protein, FC, DFC and granular components (GC) were observed, and there were many large nucleoli in a nucleus, meanwhile, the cells of the treated group tended to be mature, with a decrease in the amount of Ag-protein, FC, DFC and GC accordingly, and the nucleoli reduced both in size and number significantly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dynamic change and derivation process of FC and DFC through G1, S and G2 phases in HeLa cells

In order to get a deeper understanding of the relationship between nucleolus structure and its function, the dynamic change and derivation of FC (fibrillar center) and DFC (dense fibrillar component) through interphase were investigated in HeLa cells synchronized at the ultrastructural level. The results showed that there was a process of FC and DFC derivation in the nucleolus of HeLa cells during interphase. In G1 phase there were a few big FCs in the nucleolus of the HeLa cell. In S phase DFC around the FC got thickened and the configuration of the DFC changed. A lot of tiny FCs were derived from parts of the thickened DFC. We called the FC and DFC formed in G1 phase as primary FC (pri-FC) and primary DFC (pri-DFC) and the FC and DFC derived from the thickened pri-DFC as secondary FC (sec-FC) and secondary DFC (sec-DFC). In G2 phase sec-FC and sec-DFC were gradually separated from pri-DFC and scattered evenly in the nucleolus. Few large pri-FCs coexisted with numerous tiny sec-FCs in the nucleolus of HeLa cells in G2 phase. Based on the results of our observation, we suggest here a model of the dynamic change and the process of derivation of FC and DFC through interphase.