The two binding sites for DCMU in Photosystem II

Measurements on the fluorescence induction of Triton X-100 extracted Photosystem II (PSII) particles confirmed the existence of the two sites of inhibition in PSII for the herbicide DCMU. The two sites were located on the reducing and oxidizing sides of PSII, respectively. The inhibition on the oxidizing side, unlike that on the reducing side which was of the "none or all" type, was found only to slow down the electron donation at low concentrations of DCMU. The results also suggested that the inhibitions of DCMU at these two sites were mutually exclusive, i.e., the binding on one site prevented the binding on the other site.     

The use of spun columns in the purification of double-stranded cDNA appropriate for tailing

A reliable estimation of the efficiency of adding homopolymeric tails to double-stranded cDNA molecules by terminal deoxynucleotidyl transferase is extremely important in the construction of cDNA libraries. Appreciable differences in transformation efficiency result when the homopolymer tails to be annealed are of inadequate length. We report here that the use of a Sephadex G-50 spun column to remove oligo(dT)12-18 frequently coprecipitating in ethanol with the cDNA results in a more dependable estimation of tail lengths.     

Preparation and characterization of radioactive castanospermine

A procedure for the preparation of tritiated castanospermine is described. The tritiated alkaloid was shown to be chromatographically identical to the native material and exhibited the same inhibitory properties. Radiolabeled castanospermine tightly bound to purified intestinal sucrase. Following gel chromatography, each mole of enzyme was shown to have bound 1 mol of the radioactive alkaloid. Cultured MDCK cells were also shown to take up the labeled castanospermine. This compound should be a useful tool in the investigation of enzymes that are responsible for the processing of glycoprotein oligosaccharides.     

Fungal-Fungal Associations Affect the Assembly of Endophyte Communities in Maize (Zea mays)

Many factors can affect the assembly of communities, ranging from species pools to habitat effects to interspecific interactions. In microbial communities, the predominant focus has been on the well-touted ability of microbes to disperse and the environment acting as a selective filter to determine which species are present. In this study, we investigated the role of biotic interactions (e.g., competition, facilitation) in fungal endophyte community assembly by examining endophyte species co-occurrences within communities using null models. We used recombinant inbred lines (genotypes) of maize (Zea mays) to examine community assembly at multiple habitat levels, at the individual plant and host genotype levels. Both culture-dependent and culture-independent approaches were used to assess endophyte communities. Communities were analyzed using the complete fungal operational taxonomic unit (OTU) dataset or only the dominant (most abundant) OTUs in order to ascertain whether species co-occurrences were different for dominant members compared to when all members were included. In the culture-dependent approach, we found that for both datasets, OTUs co-occurred on maize genotypes more frequently than expected under the null model of random species co-occurrences. In the culture-independent approach, we found that OTUs negatively co-occurred at the individual plant level but were not significantly different from random at the genotype level for either the dominant or complete datasets. Our results showed that interspecific interactions can affect endophyte community assembly, but the effects can be complex and depend on host habitat level. To our knowledge, this is the first study to examine endophyte community assembly in the same host species at multiple habitat levels. Understanding the processes and mechanisms that shape microbial communities will provide important insights into microbial community structure and the maintenance of microbial biodiversity.     

The stimulatory effect of ROCK inhibitor on bovine corneal endothelial cells

Reagents which can promote the proliferation, adhesion and migration of cultured corneal endothelial cells (CECs) will be helpful for the treatment of reduced visual acuity due to CECs deficiency. The objectives of this study were to investigate the potential use of an inhibitor of Rho-associated protein kinase (ROCK), Y-27632, to cultured bovine corneal endothelial cells (B-CECs) and evaluated its effects on the proliferation, adhesion and migration of B-CECs. The proliferation of cultured B-CECs was moderately enhanced by 10 μM Y-27632. Y-27632 induced fibroblast-like morphological changes in the cultured B-CECs and normal cell morphology could recover after Y-27632 removal. In addition, Y-27632 was found to significantly enhance the adhesion and migration of B-CECs. Furthermore, the hanging drop aggregation assay showed that Y-27632 promoted B-CECs to form cellular networks and sheets, which proliferated along the liquid–air interface and migrated to the surface of the lid of dish. Our study demonstrated that Y-27632 is a potentially powerful reagent which can enhance the proliferation of cultured B-CECs. Y-27632 will be useful in CEC injection therapy and topical application for CEC deficiency.     

银合欢基因文库的构建和种子贮藏蛋白基因的分离

本文以λEMBL_3为载体,构建了银合欢(Leucaena leucocephala)的基因文库,所得重组子为3.5×10~6pfu。以大豆种子贮藏蛋白α′亚基基因为探针,从基因文库中分离得到了4个阳性克隆,并初步绘制了其中3个重组子的物理图谱。结果表明在这3个重组子的基因内部有一致的酶切位点。亚克隆的部分核苷酸序列与 GenBank 中的基因序列比较,表明与大豆种子贮藏蛋白α′亚基基因高度同源。     

A new technique to expand human mesenchymal stem cells using basement membrane extracellular matrix

Mesenchymal stem cells (MSC) show a very short proliferative life span and readily lose the differentiation potential in culture. However, the growth rate and the proliferative life span of the stem cells markedly increased using tissue culture dishes coated with a basement membrane-like extracellular matrix, which was produced by PYS-2 cells or primary endothelial cells. Furthermore, the stem cells expanded on the extracellular matrix, but not those on plastic tissue culture dishes, retained the osteogenic, chondrogenic, and adipogenic potential throughout many mitotic divisions. The extracellular matrix had greater effects on the proliferation of MSC and the maintenance of the multi-lineage differentiation potential than basic fibroblast growth factor. Mesenchymal stem cells expanded on the extracellular matrix should be useful for regeneration of large tissue defects and repeated cell therapies, which require a large number of stem or progenitor cells.     

Structural and Stereochemical Studies of Hydroxyanthraquinone Derivatives from the Endophytic Fungus Coniothyrium sp

Four known hydroxyanthraquinones ( 1–4 ) together with four new derivatives having a tetralone moiety, namely coniothyrinones A–D ( 5–8 ), were isolated from the culture of Coniothyrium sp., an endophytic fungus isolated from Salsola oppostifolia from Gomera in the Canary Islands. The structures of the new compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configurations of coniothyrinones A ( 5 ), B ( 6 ), and D ( 8 ) were determined by TDDFT calculations of CD spectra, allowing the determination of the absolute configuration of coniothyrinone C ( 7 ) as well. Coniothyrinones A ( 5 ), B ( 6 ), and D ( 8 ) could be used as ECD reference compounds in the determination of absolute configuration for related tetralone derivatives. This is the first report of anthraquinones and derivatives from an isolate of the genus Coniothyrium sp. These compounds showed inhibitory effects against the fungus Microbotryum violaceum, the alga Chlorella fusca, and the bacteria Escherichia coli and Bacillus megaterium. Chirality 25:141–148, 2013. © 2012 Wiley Periodicals, Inc.     

真菌传杆状病毒组（Furovirus）内四种病毒的细胞病理学比较研究

本文研究丁真菌传杆状病毒组（Ｆｕｒｏｖｉｒｕｓ）四个病毒成员,即甜菜坏死黄脉病毒（ＢＮＹＶＶ）、甜菜土传病毒（ＢＳＢＶ）、花生丛生病毒印度株系（ＰＣＡ－Ｉ）以及非洲株系（ＰＣＡ－Ａ）和小麦土传花叶病毒（ＳＢＷＭＶ）所引起的细胞病理变化。这四种病毒在病毒粒子聚集的结构,是否引起细胞膜聚集及聚集的结构,过氧化物酶体泡状物的形成与否及结构均有差异。另外,同一种病毒的不同株系或分离物所引起的细胞病理变化也不相同。