A quantitative analysis of secondary RNA structure using domination based parameters on trees

Background  

It has become increasingly apparent that a comprehensive database of RNA motifs is essential in order to achieve new goals in genomic and proteomic research. Secondary RNA structures have frequently been represented by various modeling methods as graph-theoretic trees. Using graph theory as a modeling tool allows the vast resources of graphical invariants to be utilized to numerically identify secondary RNA motifs. The domination number of a graph is a graphical invariant that is sensitive to even a slight change in the structure of a tree. The invariants selected in this study are variations of the domination number of a graph. These graphical invariants are partitioned into two classes, and we define two parameters based on each of these classes. These parameters are calculated for all small order trees and a statistical analysis of the resulting data is conducted to determine if the values of these parameters can be utilized to identify which trees of orders seven and eight are RNA-like in structure.     

Determination of the anamorph of Cordyceps sinensis inferred from the analysis of the ribosomal DNA internal transcribed spacers and 5.8S rDNA

The anamorph determination of Cordyceps sinensis remains problematic due to the lack of clear links between the sexual and conidial forms of the fungus. In this study, we applied molecular approaches to analyze the genetic variation of Cordyceps sinensis and its allies to identify the anamorph-teleomorph connection. The sequences of the internal transcribed spacers (ITS1 and ITS2) and 5.8S ribosomal RNA gene of Cordyceps sinensis (teleomorph) collected from Qingzang plateau (altitude over 4000m), Tibet and several related asexual conidial forms were determined. The sequence comparison showed that Cordyceps sinensis was most closely related to Hirsutella sinensis, and was clearly divergent from Paecilomyces sinensis, Stachybotrys sp. or Tolypocladium sp.; distance values, estimated according to Kimura two-parameter models between Cordyceps sinensis and Hirsutella sinensis, were extremely low (<0.02), whereas distance values between Cordyceps sinensis and Paecilomyces sinensis, Stachybotrys sp. and Tolypocladium sp. were 0.34, 0.21 and 0.25, respectively. Taken together, Hirsutella sinensis and Cordyceps sinensis are the different stages of the life cycle stages of the same organism. Hirsutella sinensis is therefore the anamorph of Cordyceps sinensis, rather than Paecilomyces sinensis or other species. The possible reasons as to why different taxa can be obtained when culturing Cordyceps sinensis are also discussed.     

Analogues of SB-203207 as inhibitors of tRNA synthetases

SB-203207 and 10 analogues have been prepared, by elaboration of altemicidin, and evaluated as inhibitors of isoleucyl, leucyl and valyl tRNA synthetases (IRS, LRS, and VRS, respectively). Substituting the isoleucine residue of SB-203207 with leucine and valine increased the potency of inhibition of LRS and VRS, respectively. The leucine derivative showed low level antibacterial activity, while several of the compounds inhibited IRS from Staphylococcus aureus WCUH29 more strongly than rat liver IRS.     

我国草坪科学的现状与发展

本文对草坪科学的主要研究方向的进展进行了综述,指出了我国草坪研究的优势、劣势及存在的主要问题,如种质资源丰富但迫切需要保护;育种工作刚刚起步;草坪管理技术落后。还阐述了今后促进草坪科学发展的工作重点。     

Research on the feeding behavior of Neospastis simaona larvae

本文对思茅新木蛾Neospastis simaona Wang幼虫的取食行为、取食偏好性以及明暗条件对其取食量的影响进行了观察研究,为该昆虫的防治提供了理论依据.研究结果表明:思茅新木蛾幼虫随着龄期的增加,取食次数增多,取食总时间增加,但一次取食时间无明显变化;思茅新木蛾幼虫对木荷(Schima superba)有强烈嗜食性,4龄幼虫喜食木荷幼叶,5、6龄幼虫对木荷幼叶、成熟叶无明显偏好性;明暗条件对思茅新木蛾4至6龄幼虫的取食量没有显著影响(P＞0.05).     

The Regulation of Exogenous Jasmonic Acid on UV-B Stress Tolerance in Wheat

Enhanced ultraviolet-B radiation (UV-B, 280?C320?nm) is recognized as one of the environmental stress factors that cannot be neglected. Jasmonic acid (JA) is an important signaling molecule in a plant??s defense against biotic and abiotic stresses. To determine the role of exogenous JA in the resistance of wheat to stress from UV-B radiation, wheat seedlings were exposed to 0.9?kJ?m^?2?h^?1 UV-B radiation for 12?h after pretreatment with 1 and 2.5?mM JA, and the activity of antioxidant enzymes, the level of malondialdehyde (MDA), the content of UV-B absorbing compounds, photosynthetic pigments, and proline and chlorophyll fluorescence parameters were measured. The results of two-way ANOVA illustrated that the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), MDA level, anthocyanin and carotenoid (Car) content, and almost all chlorophyll fluorescence parameters were significantly affected by UV-B, JA, and UV-B?×?JA (P?<?0.05) [the maximal efficiency of photosystem II photochemistry (F _v/F _m) was not affected significantly by UV-B radiation]. Duncan??s multiple-range tests demonstrated that UV-B stress induced a significant reduction in plant photosystem II (PSII) function and SOD activity and an increased level of membrane lipid peroxidation, indicative of the deleterious effect of UV-B radiation on wheat. JA pretreatment obviously mitigated the detrimental effect of UV-B on PSII function by increasing F _v/F _m, reaction centers?? excitation energy capture efficiency (F _v??/F _m??), effective photosystem II quantum yield (??PSII), and photosynthetic electron transport rate (ETR), and by decreasing nonphotochemical quenching (NPQ) of wheat seedlings. Moreover, the activity of SOD and the content of proline and anthocyanin were provoked by exogenous JA. However, the MDA level was increased and Car content was decreased by exogenous JA with or without the presence of supplementary UV-B, whereas the contents of chlorophyll and flavonoids and related phenolics were not affected by exogenous JA. Meanwhile, exogenous JA resulted in a decrease of CAT and POD activities under UV-B radiation stress. These results partly confirm the hypothesis that exogenous JA could counteract the negative effects of UV-B stress on wheat seedlings to some extent.     

Preventing and curing citrulline-induced autoimmune arthritis in a humanized mouse model using a Th2-polarizing iNKT cell agonist

Invariant natural killer T (iNKT) cells are innate lymphocytes with unique reactivity to glycolipid antigens bound to non-polymorphic CD1d molecules. They are capable of rapidly releasing pro- and/or anti-inflammatory cytokines and constitute attractive targets for immunotherapy of a wide range of diseases including autoimmune disorders. In this study, we have explored the beneficial effects of OCH, a Th2-polarizing glycolipid agonist of iNKT cells, in a humanized mouse model of rheumatoid arthritis (RA) in which citrullinated human proteins are targeted by autoaggressive immune responses in mice expressing an RA susceptibility human leukocyte antigen (HLA) DR4 molecule. We found for the first time that treatment with OCH both prevents and cures citrulline-induced autoimmune arthritis as evidenced by resolved ankle swelling and reversed histopathological changes associated with arthritis. Also importantly, OCH treatment blocked the arthritogenic capacity of citrullinated antigen-experienced splenocytes without compromising their global responsiveness or altering the proportion of splenic naturally occurring CD4(+)CD25(+)FoxP3(+) regulatory T cells. Interestingly, administering the Th1-promoting iNKT cell glycolipid ligand α-C-galactosylceramide into HLA-DR4 transgenic mice increased the incidence of arthritis in these animals and exacerbated their clinical symptoms, strongly suggesting a role for Th1 responses in the pathogenesis of citrulline-induced arthritis. Therefore, our findings indicate a role for Th1-mediated immunopathology in citrulline-induced arthritis and provide the first evidence that iNKT cell manipulation by Th2-skewing glycolipids may be of therapeutic value in this clinically relevant model, a finding that is potentially translatable to human RA.     

Isolation of homozygous mutant mouse embryonic stem cells using a dual selection system

Obtaining random homozygous mutants in mammalian cells for forward genetic studies has always been problematic due to the diploid genome. With one mutation per cell, only one allele of an autosomal gene can be disrupted, and the resulting heterozygous mutant is unlikely to display a phenotype. In cells with a genetic background deficient for the Bloom's syndrome helicase, such heterozygous mutants segregate homozygous daughter cells at a low frequency due to an elevated rate of crossover following mitotic recombination between homologous chromosomes. We constructed DNA vectors that are selectable based on their copy number and used these to isolate these rare homozygous mutant cells independent of their phenotype. We use the piggyBac transposon to limit the initial mutagenesis to one copy per cell, and select for cells that have increased the transposon copy number to two or more. This yields homozygous mutants with two allelic mutations, but also cells that have duplicated the mutant chromosome and become aneuploid during culture. On average, 26% of the copy number gain events occur by the mitotic recombination pathway. We obtained homozygous cells from 40% of the heterozygous mutants tested. This method can provide homozygous mammalian loss-of-function mutants for forward genetic applications.