Alterations of three-dimensional structure of nucleolar organizers during cell division and differentiation

细胞分裂和分化过程中核仁组织者三维结构的变化

基本信息

批准号：
09640793
负责人：
SATO Seiichi
金额：
$ 1.6万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

The nucleoloneina of Raphanus sativus root-tip cells was studied with light and electron microscopy especially focusing on its three-dimensional structural organization. Its countour was very intricate and thc thickness showed a large variation in air-dried specimens. It usually appeared to coil or meander. Serial ultrathin sectioning of thc nucleolonema iii its longitudinal orientation first revealed the stack of short nucleolonema fragments, then a pair of knobbly frames with space in-between, and again the stack of the short nucleolonema segments. On the other hand, transversal sections revealed 'c'-shaped segments with the change of their openings' orientation. Morphometry of the nucleolonema indicated two categories of the nucleolonema ; each had an average thickness of 510 nm and 1.19mum, respectively. Taken together, the thin nucleolonema may coil or fold to form the thick one. The fibrillar centers including DNA-containing structures were closely associated with the thin nucleo … More lonem a and intermittently arranged along the nucleolonema.Localization of intranucleolar DNA under hypoxic conditions was examined in excised loot tips of Allium cepa. Application of a silver impregnation technique to serial ultrathin sections indicated that the nucleolus segregated into two regions, the central core of the dense fibrillar component (DFC) and the periphery of the granular component (GC), and developed achromatic channels meandering within the DEC core. Electron microscopy showed that the Qccurrence of the achromatic channel was caused by development and/or fusion of the fibrillar centers (FCs), which are believed to contain the temporarily resting ribosomal-RNA genes (rDNA). The label of the DFC with anti-DNA antibodies was significantly strong compared with that of the cytosol and the labeling specificity was uniform throughout the DEC.Interestingly, the labeling specificity of the ECs and their surrounding region in the specimens exposed to hypoxic condition was almost the same as those grown under a normal condition. Concurrently with the development of the FCs under hypoxic conditions, the granules about 35 um in diameter (35 nm granules) were formed in the FCs. They were not labeled at all with anti-DNA antibodies and RNase-gold complexes, indicating that they contain neither DNA nor RNA.Altogether, the DFC containing the intranucleolar DNA probably engaged in the RNA transcription may gradually collapses to turn into the FCs and simultaneously releases the inactivated rDNA as clusters of chromatin-likemasses and Sonic nucleolar proteins as the 35 inn granules, when the cells are exposed to hypoxic conditions. Less

用光学和电子显微镜对萝卜根尖细胞的核仁进行了研究，特别关注其三维结构组织，其数量非常复杂，并且在风干的标本中厚度变化很大，通常呈卷曲或卷曲。核仁瘤的连续超薄切片其纵向方向首先显示了短核仁瘤碎片的堆叠，然后显示了一对带有空间的节状框架。另一方面，横截面显示“C”形片段，其开口方向的变化表明核仁瘤有两类。平均厚度分别为 510 nm 和 1.19μm，合计起来，薄的核仁体可以卷曲或折叠形成厚的纤维状中心。包括含有 DNA 的结构与薄核密切相关，并沿着核仁瘤间歇性排列。在洋葱的切下的尖端中检查了缺氧条件下核仁内 DNA 的定位，将银浸渍技术应用于连续超薄切片。表明核仁分为两个区域，致密纤维成分（DFC）的中央核心和细胞核的外围。电子显微镜显示，消色差通道的 Q 出现是由纤维中心 (FC) 的发育和/或融合引起的，据信纤维中心包含暂时静止的纤维中心。与胞质溶胶相比，带有抗 DNA 抗体的 DFC 的标记明显强，并且标记特异性在整个过程中是一致的。有趣的是，暴露于低氧条件下的标本中ECs及其周围区域的标记特异性与在正常条件下生长的ECs及其周围区域的标记特异性几乎相同，与FCs在低氧条件下的发育同时，颗粒约35μm。 FC 中形成直径为 35 nm 的颗粒，它们根本没有用抗 DNA 抗体和 RNase-金复合物标记，表明它们既不含 DNA，也不含 DNA。 RNA。总而言之，当细胞处于较少暴露于缺氧环境。