Effects of Acetylcholine, Cytochalasin B and Amiprophosmethyl on Phloem Transport in Radish （Raphanus sativas）

We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement （acetylcholine, （ACh） a neurotransmitter in animals and insects; cytochalasin B, （CB） a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, （APM） a specific inhibitor of many cellular responses that are mediated by microtubule systems）. Their effects on phloem transport were estimated by two experimental devices： （i） a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and （ii） distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations （5.0×10^-4 mol/L） but inhibited it in higher concentrations （2.0×10^-3 mol/L） from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport.     

芨芨草愈伤组织器官发生及植株再生

芨芨草(Achnatherum splendens (Trin.) Nevski)种子消毒并在MS培养基上萌发获得无菌苗, 以幼苗的叶鞘和胚轴为外植体诱导愈伤组织, 经继代后进一步诱导不定芽及生根。研究结果表明, 诱导愈伤组织最适合的培养基为B5+1.5 mg.L-12,4-D+0.5 mg.L-1 NAA; 诱导芽分化较适合的培养基为B5+0.5 mg.L-1 6-BA +0.2 mg.L-1 NAA; 1/4 B5+1.0 mg.L-1 NAA+0.2 mg.L-1 IBA +1.0 g.L-1活性炭培养基则有利于芨芨草试管苗的生根。本实验建立了完整的芨芨草植株再生体系, 移栽成活率高。     

New selenoproteins identified in silico from the genome of Anopheles gambiae

Selenoprotein is biosynthesized by the incorporation of selenocysteine into proteins,where the TGA codon in the open reading frame does not act as a stop signal but is translated into selenocysteine.The dual functions of TGA result in mis-annotation or lack of selenoproteins in the sequenced genomes of many species.Available computational tools fail to correctly predict selenoproteins.Thus,we devel-oped a new method to identify selenoproteins from the genome of Anopheles gambiae computationally.Based on released genomic information,several programs were edited with PERL language to identify selenocysteine insertion sequence(SECIS)element,the coding potential of TGA codons,and cys-teine-containing homologs of selenoprotein genes.Our results showed that 11365 genes were termi-nated with TGA codons,918 of which contained SECIS elements.Similarity search revealed that 58 genes contained Sec/Cys pairs and similar flanking regions around in-frame TGA codons.Finally,7 genes were found to fully meet requirements for selenoproteins,although they have not been anno-tated as selenoproteins in NCBI databases.Deduced from their basic properties,the newly found se-lenoproteins in the genome of Anopheles gambiae are possibly related to in vivo oxidation tolerance and protein regulation in order to interfere with anopheles' vectorial capacity of Plasmodium.This study may also provide theoretical bases for the prevention of malaria from anopheles transmission.     

北京西部山区胡枝子种群研究: 个体和构件生物量

通过对北京西部山区胡枝子(Lespedeza bicolor Turcz.)种群个体和构件地上生物量进行系统研究。结果表明, 种群(总和)个体和各构件地上生物量积累与年龄的关系均可用方程式Y=axb表示。不同种群的植株个体和构件生物量有显著性不同(P<0.05), 在海拔910-1 100 m的山脊林缘的种群个体和构件地上生物量较其它种群大, 植株地上营养构件的生物量比率较小, 而繁殖构件生物量比率较大; 不适生境中的种群则反之。种群个体生长和各构件生物量动态与环境条件关系密切。构件生物量比率也随着年龄的增长而有所变化。叶生物量比率随年龄增加而减小; 枝构件生物量比率随年龄增加而增大; 繁殖构件的生物量比率随年龄增加先增后减。依据相关指数R2, 筛选各构件生物量估计的最优模型: 枝、枝叶生物量和地上生物量均为m(DW)= a(D2H1)b, 叶生物量和花果生物量均为m(DW)=a(D)b。     

Fermentation of plant cell walls by ruminal bacteria, protozoa and fungi and their interaction with fibre particle size

The objective of the experiment was to evaluate the contribution of various ruminal microbial groups to the fermentation of cell walls of corn stover with different particle sizes based on ruminal gas production in vitro. Physical, chemical, and antibiotical methods were used to differentiate groups of bacteria, protozoa and fungi in rumen fluid, offering following rumen microbial groups: whole rumen fluid (WRF), bacterial (B), protozoal (P), fungal (F), bacterial plus protozoal (B + P), bacterial plus fungal (B + F), protozoal plus fungal (P + F), and negative control (CON). Cell walls from corn stover were ground and ball milled to produce two different particle sizes. The results showed that digestion of the cell walls was undertaken by the interaction among ruminal bacteria, protozoa and fungi, and such co-actions seemed to fail alternation by one of three microbial groups or any combinations. However, B + P group showed a significant contribution to the degradation of milled cell walls, and B + F group revealed a great synergy effect on the ground cell walls degradation. Particle size of cell walls also had a considerable influence on their fermentation extent instead of the fermentative patterns by various rumen microbial groups.     

Simultaneous quantification of malonyl-CoA and several other short-chain acyl-CoAs in animal tissues by ion-pairing reversed-phase HPLC/MS

Malonyl-CoA is a key intermediate involved in lipid synthesis and lipid oxidation. Here, we report on a novel method for the quantification of malonyl-CoA and seven other short-chain acyl-CoAs in various rat and mouse tissues using ion-pairing reversed-phase HPLC/MS. This method is capable of measuring malonyl-CoA, free coenzyme A (CoASH), acetyl-CoA, beta-hydroxyl-butyryl-CoA (HB-CoA), 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA), propionyl-CoA, succinyl-CoA, and isobutyryl-CoA simultaneously with a dynamic linear range over two orders of magnitude in a 7.0 min HPLC gradient run. The lower limit of quantification (LLOQ) was 0.225 pmol for all acyl-CoAs studied, except for HMG-CoA which had a higher LLOQ of 0.90 pmol. The interference of HB-CoA on the quantification of malonyl-CoA in animal tissues was also explored for the first time.     

Determination of triazines in infant nutrient cereal-based foods by pressurized microwave-assisted extraction coupled with high-performance liquid chromatography-mass spectrometry

A method for determining triazine herbicides in infant nutrient cereal-based foods by pressurized microwave-assisted extraction (PMAE), coupled with high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS), is described. The key parameters of PMAE, including extraction solvent, extraction time and temperature, were optimized. The isolation of the target compounds from the matrix was found to be efficient when 2 g of nutrient cereal samples was extracted with 20 mL of methanol for 10 min at 105 degrees C. Final determination was accomplished by HPLC-ESI/MS. The recoveries from 66.2 to 88.6% were obtained for three compounds at fortification levels (5-500 microg kg(-1)) with relative standard deviations (R.S.D.) 相似文献   

Mechanistic analysis on the effects of salt concentration and pH on protein adsorption onto a mixed-mode adsorbent with cation ligand

Streamline Direct HST is a new kind of mixed-mode adsorbent with cation exchange ligand, especially developed for the expanded bed adsorption process, which can capture target protein directly from the moderate ionic strength feedstock without the need of dilution or other additives. In this study, the isotherm adsorption behaviors and the isocratic retention factors of bovine serum albumin (BSA) on Streamline Direct HST were measured, and the corresponding adsorption mechanisms were also described. The results indicated that Streamline Direct HST shows the typical property of salt-independent adsorption and the maximum binding capacity of BSA occurs near the isoelectric point of BSA. When there are some amounts of electrostatic repulsion protein-adsorbent interactions, the multilayer adsorption could be found, and high salt concentration does not favor the adsorption of protein. A patch-controlled adsorption process and an oriented adsorption model are proposed for describing the adsorption behaviors under electrostatic repulsion condition.     

Quantitative determination of trans-polydatin, a natural strong anti-oxidative compound, in rat plasma and cellular environment of a human colon adenocarcinoma cell line for pharmacokinetic studies

A simple, accurate, precise, specific and reproducible high-performance liquid chromatography (HPLC) method was developed for determination of trans-polydatin, a natural strong anti-oxidative compound, in rat plasma and cell suspension. The assay procedure involved simple liquid-liquid extraction, the supernatant liquid was added an equal volume of water to avoid solvent effect. The detection of the analyte peak was achieved by monitoring the eluate using a UV detector set at 303 nm. The analysis used a Hypersil ODS2 C18 column (5 microm, 4.6 mm x 250 mm) and methanol/distilled water as the mobile phase (flow rate=1 mL/min). A total analytical run was achieved within 6.0 min and calibration curve was linear over a wide concentration range of 0.25-40 microg/mL for plasma sample and 1.0-500 microM for cell suspension, the coefficients of correlation were 0.9997 and 0.9999 or better, respectively. There was 80.7+/-7.86%, 96.8+/-3.20% and 102.7+/-9.72% recovery from 0.5, 10, and 40 microg/mL plasma samples, respectively. Intra- and inter-batch accuracy and precision were acceptable for the both matrices. The RSD of intra- and inter-day assay variations were all less than 10%. Both analyte and IS were stable in the battery of stability studies, freeze-thaw cycles. The described assay method was applied to pharmacokinetic studies in rats and a human colon adenocarcinoma cell line (Caco-2) successfully. The application of the assay to determine the pharmacokinetic is described.     

CD39 and control of cellular immune responses

CD39 is the cell surface-located prototypic member of the ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase) family. Biological actions of CD39 are a consequence (at least in part) of the regulated phosphohydrolytic activity on extracellular nucleotides. This ecto-enzymatic cascade in tandem with CD73 (ecto-5–nucleotidase) also generates adenosine and has major effects on both P2 and adenosine receptor signalling. Despite the early recognition of CD39 as a B lymphocyte activation marker, little is known of the role of CD39 in humoral or cellular immune responses. There is preliminary evidence to suggest that CD39 may impact upon antibody affinity maturation. Pericellular nucleotide/nucleoside fluxes caused by dendritic cell expressed CD39 are also involved in the recruitment, activation and polarization of naïve T cells. We have recently explored the patterns of CD39 expression and the functional role of this ecto-nucleotidase within quiescent and activated T cell subsets. Our data indicate that CD39, together with CD73, efficiently distinguishes T regulatory cells (Treg) from other resting or activated T cells in mice (and humans). Furthermore, CD39 serves as an integral component of the suppressive machinery of Treg, acting, at least in part, through the modulation of pericellular levels of adenosine. We have also shown that the coordinated regulation of CD39/CD73 expression and of the adenosine receptor A2A activates an immunoinhibitory loop that differentially regulates Th1 and Th2 responses. The in vivo relevance of this network is manifest in the phenotype of Cd39-null mice that spontaneously develop features of autoimmune diseases associated with Th1 immune deviation. These data indicate the potential of CD39 and modulated purinergic signalling in the co-ordination of immunoregulatory functions of dendritic and Treg cells. Our findings also suggest novel therapeutic strategies for immune-mediated diseases.