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。     

洋葱细胞核仁内ＤＮＡ的结构变化及排布过程

以洋葱（Allium cepa L.)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,邓核仁外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。     

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。     

小麦细胞核仁中rRNA基因转录的超微定位

真核细胞核仁中rRNA基因转录位点是长期以来未能解决的问题。以小麦细胞为研究材料,应用常规电子显微镜技术,观察了小麦细胞核仁纤维中心(Fibrillar centers,FC)内染色质的超微结构;并通过DNA抗体阐明了核仁中DNA位于纤维中心、致密纤维组分(Dense fibrillar component,DFC)以及两者的过渡区域;应用RNA聚合酶I相关转录因子UBF(Upstream binding factor)抗体所做的分析显示,小麦细胞核仁中UBF位于FC与DFC的过渡区域以及DFC中,在FC中没有UBF的存在;进一步借助于RNA/DNA杂合体抗体选择性地直接标记核仁中rRNA基因的转录位点,结果表明了小麦细胞核仁rRNA基因的转录位点是在FC与DFC的过渡区域及DFC中。     

小麦细胞核仁中rRNA基因转录的超微定位（简报）

真核细胞核仁中rRNA基因转录位点是长期以来未能解决的问题。以小麦细胞为研究材料,应用常规电子显微镜技术,观察了小麦细胞核仁纤维中心（Fibrillar centers,FC)内染色质的超微结构;并通过DNA抗体阐明了核仁中DNA位于纤维中心、致密纤维组分（Dense fibrillar component,DFC）以及两者的过度区域;应用RNA聚合酶I相关转录因子UBF（Upstream binding factor) 抗体所做的分析显示,小麦细胞核仁中UBF位于FC与DFC的过渡区域以及DFC中,在FC中没有UBF的存在;进一步借助于RNA／DNA杂合体抗体选择性地直接标记核仁中rRNA基因的转录位点,结果表明了小麦细胞核仁rRNA基因的转录位点是在FC与DDFC的过渡区域及DFC中。     

鼠肝细胞核仁结构与rRNA基因转录位点研究

通过常规电子显微镜观察了鼠肝细胞核仁的超微结构,并采用NAMA-Ur细胞化学DNA特异染色方法分析了核仁中DNA的分布及其原位位置,直观的显示了鼠肝细胞核仁DNA来源于核仁伴随染色质,并在核仁DFC区域连续伸展,排布于FC的边缘部位及DFC区域中,进一步借助于RNA/DNA杂合体抗体选择性直接标记核仁中rRNA基因转录位点,结果表明了鼠肝细胞核仁rRNA基因的转录位点是在FC的边缘及DFC区域.     

蚕豆细胞核仁和核质中剪接因子SC35的定位研究

本文以蚕豆(Vicia faba L.)根端分生组织细胞为材料,以抗SC35抗体为探针,在电镜下对SC35在高等植物细胞中的存在与否和分布特点进行了研究,发现经抗SC35抗体标记后,标明SC35位置的胶体金颗粒主要分布于核仁的致密纤维组分(DFC)、核质的染色质间颗粒(IGs)和染色质周边纤维处(PFs),而核仁的纤维中心(FC)、核仁液泡和集缩染色质团块中央部位的金颗粒很少。DFC, IGs和PFs处的金颗粒平均密度分别为65.89个/μm~2和36.28个/μm~2,远远高于集缩染色质团块中央部位以及FC和核仁液泡处的金颗粒平均密度(分别为5.90个/μm~2和6.26个/μm~2)。说明蚕豆细胞核仁的DFC,核质的IGs和PFs处富含剪接因子SC35。本文研究结果表明,SC35或SC35类蛋白在蚕豆细胞核质中的分布与其在哺乳动物细胞核质中的分布规律相似。同时本文首次报道了SC35或SC35类蛋白存在于核仁中。     

核仁和核仁蛋白

核仁是位于细胞核内的非膜结构。电子显微镜下的核仁从形态上可以分为三层结构包括纤维中心区(FC)、高密度纤维区(DFC)和颗粒区(GC)。核仁内的蛋白有核糖体蛋白和非核糖体蛋白两种。利用蛋白质组学方法已经鉴定了350多种核仁蛋白,其中包括80多种核糖体蛋白。核仁是核糖体合成的场所,核仁中的非核糖体蛋白对核糖体的生物合成起关键调控作用。核仁不仅是细胞内通讯和核糖体：RNA加工的中心,而且在细胞周期、细胞增殖和衰老中起重要调控作用;核仁也是tRNA、mRNA和其它类型小分子RNA加工的场所。因此核仁是一个多功能的细胞生命活动中心。     

不同固定方法对植物细胞扫描电镜观察用冷冻断裂样品的影响

用冷冻断裂法在扫描电镜下研究了洋葱(Allium cepa)根端分生组织细胞内部的三维结构。采用了两种固定方法。冷冻断裂前只用1％锇酸固定的材料容易在细胞质和核之间断开,而用卡诺固定液(无水乙醇:冰醋酸3:1)前固定,然后再用1％锇酸固定的材料容易使细胞核断裂。前一固定方法适于研究细胞质的内部结构(细胞骨架的纤维、线粒体、内质网等及其三维分布关系):后一固定方法适于研究核内结构(染色质、核仁、核基质纤维)的三维形象,特别是核仁纤维中心染色质的三维结构。     

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.     

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.     

Correlation of the nucleolar organizer and the fibrillar center of the nucleolus

The review is dedicated to the question, to what extent it is possible to speak about the correspondence of the fibrillar center (FC) of the nucleolus to the nucleolar organizer region (NOR) of the metaphase chromosome. The analysis of the literature on the problem provides grounds for the affirmation that the chromatin-containing elements of the FC and of the fibrillar component of the nucleolus correspond to the NOR. At the same time, the number of facts evidence in favour of the hypothesis that the FC serves as a kind of "depot" for nucleolar proteins. The latter makes it possible to consider the FC to be polyfunctional.     

A comparative study of the main components of the nucleolus in different populations of rat trophoblast cells during differentiation. II. The nucleoli of the trophospongium cells, the glycogen cells and the secondary giant cells

A comparative study was performed of the arrangement of different nucleolar components during differentiation of trophoblast cell populations in the junctional zone of placenta (glycogen cells and trophospongium) and in the secondary giant cells. Each cell type is characterized by specific interrelation of nucleolar components. Some glycogen cells show signs of segregation of nucleolar components: strands of nucleolar components with fibrillar centers (FCs) are displaced to the periphery of the nucleolus and contact with the perinucleolar chromatin. Large reticular nucleoli in trophospongium cells contain many FCs which are gathered into several "chains" by strands of dense fibrillar component. Such a "chain" has also been found in nucleoli of secondary giant cells, with greater number of FCs in each "chain". Relationship between the arrangement of nucleolar components and the level of cell differentiation is discussed.