小麦根端分生组织细胞核仁的超微结构与rDNA复制位置

应用常规电镜和电镜放射自显影技术，观察到小麦根端分生细胞核仁的超微结构是由纤维中心（FC），密集纤维成分（DFC）和颗粒成分（G）等构成的，小麦根尖用3H－胸腺嘧啶脱氧核苷标记，电镜放射自显影研究的结果显示，银粒大多分布在核仁边缘的颗粒区，密集纤维成分次之，纤维中心和密集纤维成分的交界区出现的银粒最少，我们推测，rDNA的复制主要发生在颗粒区，但有时在纤维中心与密集纤维成分交界处就开始复制，然后向颗粒区转移。     

Cerebellar degeneration in lurcher mice under confocal laser scanning microscope

Lurcher mutant mice represent a natural model of genetically‐determined olivocerebellar degeneration caused by a mutation in the δ2 glutamate receptor gene. They suffer from progressive postnatal loss of cerebellar Purkinje cells and a decrease of granule cells and inferior olive neurons. Their wild type littermates serve as healthy controls. A confocal laser scanning microscope was used aiming investigation the dynamics of changes in the cerebellar cortex of Lurcher and wild type mice derived from two strains during the period of 8–21 postnatal days. Fluorescent double‐staining was used to visualize mainly the Purkinje cells in cerebellar slices. In wild types, only normal Purkinje cells of round or regular drop‐shaped were present, when staining intensity of other individual cell structures differed in dependence on the age of the animal. In Lurcher mutants, there were still some normal‐shaped cells. Nevertheless, depending on the animal's age, a wide variety of stages of the cell degeneration were depicted. The main characteristics of Purkinje cell degeneration in the early stage are: disruption of the continuity of the Purkinje cell layer, dark spots in cell nuclei and an irregular coloring of the cytoplasm. Later, the cells and their nuclei were deformed, often with two main dendrites sprouting from the cell body. Finally, the cell and nucleus margins were unclear, dendrites were significantly thickened, showing signs of shrinkage and fragmentation. Cell nucleoli underwent changes in number and appearance. No differences between the Lurcher mice of both strains (C3H and B6CBA) under examination were found. Microsc. Res. Tech. 76:545–551, 2013. © 2013 Wiley Periodicals, Inc.     

Repeated elements coordinate the spatial organization of the yeast genome

The spatial organization of the chromosomes is crucial for gene expression and development. Inter‐ and intrachromosomal interactions form a crucial part of this epigenomic regulatory system. Here we use circular chromosome conformation capture‐on‐chip (4C) to identify interactions between repetitive and non‐repetitive loci within the yeast genome. The interacting regions occur in non‐randomly distributed clusters. Furthermore, the SIR2 histone deacetylase has opposing roles in the organization of the inter‐ or intrachromosomal interactions. These data establish a dynamic domain model for yeast genome organization. Moreover, they point to the repeated elements playing a central role in the dynamic organization of genome architecture. Copyright © 2009 John Wiley & Sons, Ltd.     

Digital three-dimensional visualization of cellular organelles studied by medium- and high-voltage electron microscopy

Tilted thick sections (one-half to several micrometres) of biological specimens observed with medium- to high-voltage electron microscopes are extremely useful for the study of the three-dimensional (3-D) structure of organelles. If high resolution in 3-D visualization and 3-D reconstruction is needed, many images corresponding to various angles of rotation and tilt must be recorded. This necessitates very time-consuming work—including eventual photographic processing—before good positioning of the object is defined. We have developed software which permits very rapid and precise determination of the tilt-axis, the registration of tilted views, 3-D measurements and 3-D visualization. Images are digitized either from negative films or directly with a camera fitted to the microscope. The application of the software is performed in minutes and allows for a rapid check of the quality of the tilt-series and of the features of interest of the object. Application of the software to the study of the 3-D structure of active components of the nucleolus stained with silver is shown.     

考虑输电阻塞的电网固定成本分摊核仁法

探讨了电力市场环境下多区域互联电网固定成本的分摊问题,给出了固定成本分摊的合作博弈模型。针对输电固定成本分配的核仁模型未考虑输电阻塞的情况,提出了一种区域核仁算法。首先根据系统潮流分布情况确定出现阻塞的线路,再根据节点边际价格的差异将输电网划分成多个输电区域,每个输电区域所有节点边际价格基本一致,区域内部线路没有阻塞;然后采用等值双边交易法将输电固定成本分配给各输电区域;最后在区域内部采用核仁模型将成本分配到用户。该方法考虑了阻塞并减小了将多区域互联电网作为一个整体求核仁解时的计算量。以IEEE14节点系统为例的仿真结果表明了该方法的可行性。     

基于合作博弈论的电能替代效益分摊方法

电能替代对于落实节能环保政策、实现能源战略转型具有实际意义。为了将电能替代效益公平合理地分摊给电力用户,激励用户参与电能替代,提出一种基于合作博弈理论的电能替代效益分摊方法。分析电能替代对降低生产运行成本和减少污染排放的价值,并对其进行量化;基于合作博弈理论,采用核仁和Shapley值法对电能替代效益进行分摊。算例验证了所提电能替代效益分摊方法的有效性和合理性。     

The Patterning and Proportion of Charged Residues in the Arginine-Rich Mixed-Charge Domain Determine the Membrane-Less Organelle Targeted by the Protein

Membrane-less organelles (MLOs) are formed by biomolecular liquid–liquid phase separation (LLPS). Proteins with charged low-complexity domains (LCDs) are prone to phase separation and localize to MLOs, but the mechanism underlying the distributions of such proteins to specific MLOs remains poorly understood. Recently, proteins with Arg-enriched mixed-charge domains (R-MCDs), primarily composed of R and Asp (D), were found to accumulate in nuclear speckles via LLPS. However, the process by which R-MCDs selectively incorporate into nuclear speckles is unknown. Here, we demonstrate that the patterning of charged amino acids and net charge determines the targeting of specific MLOs, including nuclear speckles and the nucleolus, by proteins. The redistribution of R and D residues from an alternately sequenced pattern to uneven blocky sequences caused a shift in R-MCD distribution from nuclear speckles to the nucleolus. In addition, the incorporation of basic residues in the R-MCDs promoted their localization to the MLOs and their apparent accumulation in the nucleolus. The R-MCD peptide with alternating amino acids did not undergo LLPS, whereas the blocky R-MCD peptide underwent LLPS with affinity to RNA, acidic poly-Glu, and the acidic nucleolar protein nucleophosmin, suggesting that the clustering of R residues helps avoid their neutralization by D residues and eventually induces R-MCD migration to the nucleolus. Therefore, the distribution of proteins to nuclear speckles requires the proximal positioning of D and R for the mutual neutralization of their charges.