氮源种类及浓度对眼点拟微绿球藻生长密度、油脂产率和二十碳五烯酸含量的影响

氮源是影响微藻生长和油脂积累的重要因素,文中通过单因素试验比较了NaNO3、CO(NH2)2、NH4Cl、CH3COONH4及其浓度对眼点拟微绿球藻生长密度、生长速率、油脂产率、二十碳五烯酸(EPA)含量的影响。结果表明：NH4+更易被眼点拟微绿球藻利用,能更好地促进微藻生长和油脂积累;氮浓度的增加有利于微藻的生长和藻油脂肪酸的去饱和,但不利于微藻油脂的积累。在实验考察的氮源种类和浓度范围内,CH3COONH4是促进眼点拟微绿球藻生长和油脂积累、EPA生成的适宜氮源,其适宜的浓度为5.29 mmol/L。     

Whole-Organ CT Perfusion of the Pancreas: Impact of Iterative Reconstruction on Image Quality,Perfusion Parameters and Radiation Dose in 256-Slice CT-Preliminary Findings

Background

This study was performed to assess whether iterative reconstruction can reduce radiation dose while maintaining acceptable image quality, and to investigate whether perfusion parameters vary from conventional filtered back projection (FBP) at the low-tube-voltage (80-kVp) during whole-pancreas perfusion examination using a 256-slice CT.

Methods

76 patients with known or suspected pancreatic mass underwent whole-pancreas perfusion by a 256-slice CT. High- and low-tube-voltage CT images were acquired. 120-kVp image data (protocol A) and 80-kVp image data (protocol B) were reconstructed with conventional FBP, and 80-kVp image data were reconstructed with iDose⁴ (protocol C) iterative reconstruction. The image noise; contrast-to-noise ratio (CNR) relative to muscle for the pancreas, liver, and aorta; and radiation dose of each protocol were assessed quantitatively. Overall image quality was assessed qualitatively. Among 76 patients, 23 were eventually proven to have a normal pancreas. Perfusion parameters of normal pancreas in each protocol including blood volume, blood flow, and permeability-surface area product were measured.

Results

In the quantitative study, protocol C reduced image noise by 36.8% compared to protocol B (P<0.001). Protocol C yielded significantly higher CNR relative to muscle for the aorta, pancreas and liver compared to protocol B (P<0.001), and offered no significant difference compared to protocol A. In the qualitative study, protocols C and A gained similar scores and protocol B gained the lowest score for overall image quality (P<0.001). Mean effective doses were 23.37 mSv for protocol A and 10.81 mSv for protocols B and C. There were no significant differences in the normal pancreas perfusion values among three different protocols.

Conclusion

Low-tube-voltage and iDose⁴ iterative reconstruction can dramatically decrease the radiation dose with acceptable image quality during whole-pancreas CT perfusion and have no significant impact on the perfusion parameters of normal pancreas compared to the conventional FBP reconstruction using a 256-slice CT scanner.     

Semantic Annotation of Mutable Data

Electronic annotation of scientific data is very similar to annotation of documents. Both types of annotation amplify the original object, add related knowledge to it, and dispute or support assertions in it. In each case, annotation is a framework for discourse about the original object, and, in each case, an annotation needs to clearly identify its scope and its own terminology. However, electronic annotation of data differs from annotation of documents: the content of the annotations, including expectations and supporting evidence, is more often shared among members of networks. Any consequent actions taken by the holders of the annotated data could be shared as well. But even those current annotation systems that admit data as their subject often make it difficult or impossible to annotate at fine-enough granularity to use the results in this way for data quality control. We address these kinds of issues by offering simple extensions to an existing annotation ontology and describe how the results support an interest-based distribution of annotations. We are using the result to design and deploy a platform that supports annotation services overlaid on networks of distributed data, with particular application to data quality control. Our initial instance supports a set of natural science collection metadata services. An important application is the support for data quality control and provision of missing data. A previous proof of concept demonstrated such use based on data annotations modeled with XML-Schema.     

Myristoylation is required for human immunodeficiency virus type 1 Gag-Gag multimerization in mammalian cells

The Gag protein of human immunodeficiency virus type 1 directs the virion assembly process. Gag proteins must extensively multimerize during the formation of the spherical immature virion shell. In vitro, virus-like particles can be generated from Gag proteins that lack the N-terminal myristic acid modification or the nucleocapsid (NC) protein. The precise requirements for Gag-Gag multimerization under conditions present in mammalian cells, however, have not been fully elucidated. In this study, a Gag-Gag multimerization assay measuring fluorescence resonance energy transfer was employed to define the Gag domains that are essential for homomultimerization. Three essential components were identified: protein-protein interactions contributed by residues within both the N- and C-terminal domains of capsid (CA), basic residues in NC, and the presence of myristic acid. The requirement of myristic acid for multimerization was reproduced using the heterologous myristoylation sequence from v-src. Only when a leucine zipper dimerization motif was placed in the position of NC was a nonmyristoylated Gag protein able to multimerize. These results support a three-component model for Gag-Gag multimerization that includes membrane interactions mediated by the myristoylated N terminus of Gag, protein-protein interactions between CA domains, and NC-RNA interactions.     

Identification of RNA binding sequences of Drosophila SR protein DX16

Dxl6 is a member of the Drosophila melanogaster SR protein family, a group of nuclear proteins that are both essential splicing factors and specific splicing regulators. To get more insight of Dx16 function, we generated the monoclonal antibody against Dx16 and determined its expression pattern and subcellular location. It is mainly expressed in the nucleus of CNS in Drosophila embryos. In order to investigate the RNA-binding specificity of Dxl6, Dxl6-binding RNAs were identified by SELEX screen by using recombinant Dxl6 N-terminus protein as the target. These RNAs contained a consensus motif. Some pre-mRNAs from the corresponding genes showed splicing defects in the Dxl6-P-element insertional mutant fly. These results indicate that Dxl6 has unique functions in the removal of some introns during development.     

Negative effect of chromosome 1A on dough strength shown by modification of 1D addition in durum wheat (<Emphasis Type="Italic">Triticum durum</Emphasis>)

A monosomic addition line of Aegilops tauschii chromosome 1D in Triticum durum cv. PBW114 was produced in 1990. This line was self-pollinated and maintained for several generations while following the presence of chromosome 1D carrying the gene for red glume color. Cytological analysis indicated that two of the three derivative lines had substitution of chromosome 1D for 1A and another had substitution of chromosome 1D for 1B. One of these lines carried a pair of small chromosomes in addition to the 1D chromosome. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the derived lines showed the presence of high-molecular-weight (HMW) glutenin encoded by the Glu-D1 locus. The small chromosome found in one of the lines had nearly regular pairing and transmission to daughter nuclei. Fluorescent in situ hybridization (FISH) and analysis of molecular markers indicated that the small chromosome was derived from the short arm of chromosome 1A and carried the Glu-A3 locus. Microsatellite mapping based on the deletion bin map revealed that the small chromosome had terminal deletions on both the terminal and centromeric sides. The line with the small chromosome showed improvement of the sodium dodecyl sulfate (SDS)-sedimentation value as compared to parent durum. However, the increase in SDS-sedimentation value was more significant in the substitution line of chromosome 1D for 1A without the small chromosome. These facts suggest a negative effect of the Glu-A3 locus on dough strength. The sequence of the Glu-D1 locus from these lines showed that the HMW glutenin subunits were Ae. tauschii specific 2^t + T2, which were previously found to be associated with poor rheological properties and bread loaf volume in synthetic hexaploid wheat by other workers. Thus, the significant improvement in the SDS-sedimentation value of the substitution line of 1D for 1A suggests that the absence of the negative effect of chromosome 1A on quality is more important than the presence of Glu-D1 of Ae. tauschii.     

Optimization of medium composition for the production of alkaline β-mannanase by alkaliphilic Bacillus sp. N16-5 using response surface methodology

In this work, a 2² factorial design was employed combining with response surface methodology (RSM) to optimize the medium compositions for the production of alkaline β-mannanase by alkaliphilic Bacillus sp. N16-5 isolated previously from sediment of Wudunur Soda Lake in Inner Mongolia, China. The central composite design (CCD) used for the analysis of treatment combinations showed that a second-order polynomial regression model was in good agreement with experimental results, with R ² = 0.9829 (P < 0.05). The maximum activity was obtained at NaCl concentration (84.4 g l⁻¹) and sodium glutamate (3.11 g l⁻¹) and a high medium pH around 10.0. Under such conditions, the activity of alkaline β-mannanase achieved 310.1 U/ml in the scale of 5-l fermenter, which was increased nearly twice compared with the original. Through optimization, the substrates shifted from the expensive substrates, such as locust bean gum and peptone, to the inexpensive ones such as konjac powder, soymeal, and sodium glutamate. The experiment results also suggested that the environmental conditions of high salinity and high alkalinity, as well as the inducer substrates, play very important roles in the production of the alkaline β-mannanase by alkaliphilic Bacillus sp. N16-5.