Towards a global database of weed risk assessments: a test of transferability for the tropics

Worldwide spread and establishment of alien plant species continues to accelerate and damage ecological and agricultural systems. Early warning and prevention of high-risk introductions is the most cost-effective approach to minimise losses while maximising benefits, and the Australian Weed Risk Assessment (A-WRA) system has been the most well-developed and successful predictive scheme. However, any system would be limited if the results or scores were confined to the locality of assessment. We compiled A-WRA scores conducted in four tropical to sub-tropical regions and tested the accuracy of these scores for predicting naturalisations for a separate well-documented, equatorial, exotic flora where weed risk assessments have never been conducted. Receiver Operating Characteristic (ROC) curves reflect high accuracies of predictions, comparable to those in other studies. No significant differences in accuracy were found between each regional subset and the compiled set of scores. Our results show that A-WRA scores assessed at one locality can be used for others of similar climate, increasing the utility of every species’ assessment. A global database of A-WRA scores would enable rapid local decision-making in border controls on imported plant species. A growing record of species assessments would also facilitate monitoring evolutionary and ecological aspects of invasive species.     

Leucine nutrition in animals and humans: mTOR signaling and beyond

Macronutrients, such as protein or amino acid, not only supply calories but some components may also play as signaling molecules to affect feeding behavior, energy balance, and fuel efficiency. Leucine, a branched-chain amino acid is a good example. After structural roles are satisfied, the ability of leucine to function as signal and oxidative substrate is based on a sufficient intracellular concentration. Therefore, leucine level must be sufficiently high to play the signaling and metabolic roles. Leucine is not only a substrate for protein synthesis of skeletal muscle, but also plays more roles beyond that. Leucine activates signaling factor of mammalian target of rapamycin (mTOR) to promote protein synthesis in skeletal muscle and in adipose tissue. It is also a major regulator of the mTOR sensitive response of food intake to high protein diet. Meanwhile, leucine regulates blood glucose level by promoting gluconeogenesis and aids in the retention of lean mass in a hypocaloric state. It is beneficial to animal nutrition and clinical application and extrapolation to humans.     

Cell selectivity correlates with membrane-specific interactions: A case study on the antimicrobial peptide G15 derived from granulysin

A 15-residue peptide dimer G15 derived from the cell lytic protein granulysin has been shown to exert potent activity against microbes, including E. coli, but not against human Jurkat cells [Z. Wang, E. Choice, A. Kaspar, D. Hanson, S. Okada, S.C. Lyu, A.M. Krensky, C. Clayberger, Bactericidal and tumoricidal activities of synthetic peptides derived from granulysin. J. Immunol. 165 (2000) 1486-1490]. We investigated the target membrane selectivity of G15 using fluorescence, circular dichroism and ³¹P NMR methods. The ANS uptake assay shows that the extent of E. coli outer membrane disruption depends on G15 concentration. ³¹P NMR spectra obtained from E. coli total lipid bilayers incorporated with G15 show disruption of lipid bilayers. Fluorescence binding studies on the interaction of G15 with synthetic liposomes formed of E. coli lipids suggest a tight binding of the peptide at the membrane interface. The peptide also binds to negatively charged POPC/POPG (3:1) lipid vesicles but fails to insert deep into the membrane interior. These results are supported by the peptide-induced changes in the measured isotropic chemical shift and T1 values of POPG in 3:1 POPC:POPG multilamellar vesicles while neither a non-lamellar phase nor a fragmentation of bilayers was observed from NMR studies. The circular dichroism studies reveal that the peptide exists as a random coil in solution but folds into a less ordered conformation upon binding to POPC/POPG (3:1) vesicles. However, G15 does not bind to lipid vesicles made of POPC/POPG/Chl (9:1:1) mixture, mimicking tumor cell membrane. These results explain the susceptibility of E. coli and the resistance of human Jurkat cells to G15, and may have implications in designing membrane-selective therapeutic agents.     

Decidual NK cells alter in vitro first trimester extravillous cytotrophoblast migration: a role for IFN-gamma

Abnormal placentation results in either inadequate (consequences: recurrent miscarriage, intrauterine growth restriction, and preeclampsia) or overzealous (consequences: placenta accreta, increta, and percreta) placentation. NK cells dominate in first trimester decidua and probably control extravillous cytotrophoblast (EVT) invasion. We examined this interaction in a novel way, using NK cells and villous explants from concordant first trimester pregnancies cocultured using a new collagen (two-dimensional) model of placentation. Decidual NK (dNK) cells exerted contact-independent inhibition of normal cytotrophoblast migration, associated with changes in the cytotrophoblast expression of metalloproteases-2 and -9, and plasminogen activator inhibitor-1. dNK cells did not affect EVT proliferation and apoptosis, and cell column formation. dNK cell effects were partially reversed by neutralizing Abs against IFN-gamma. We provide ex vivo human evidence of a direct role for dNK in modulating EVT differentiation as they form columns and then migrate from anchoring villi.     

Exploring Nitrilase Sequence Space for Enantioselective Catalysis

Nitrilases are important in the biosphere as participants in synthesis and degradation pathways for naturally occurring, as well as xenobiotically derived, nitriles. Because of their inherent enantioselectivity, nitrilases are also attractive as mild, selective catalysts for setting chiral centers in fine chemical synthesis. Unfortunately, <20 nitrilases have been reported in the scientific and patent literature, and because of stability or specificity shortcomings, their utility has been largely unrealized. In this study, 137 unique nitrilases, discovered from screening of >600 biotope-specific environmental DNA (eDNA) libraries, were characterized. Using culture-independent means, phylogenetically diverse genomes were captured from entire biotopes, and their genes were expressed heterologously in a common cloning host. Nitrilase genes were targeted in a selection-based expression assay of clonal populations numbering 10⁶ to 10¹⁰ members per eDNA library. A phylogenetic analysis of the novel sequences discovered revealed the presence of at least five major sequence clades within the nitrilase subfamily. Using three nitrile substrates targeted for their potential in chiral pharmaceutical synthesis, the enzymes were characterized for substrate specificity and stereospecificity. A number of important correlations were found between sequence clades and the selective properties of these nitrilases. These enzymes, discovered using a high-throughput, culture-independent method, provide a catalytic toolbox for enantiospecific synthesis of a variety of carboxylic acid derivatives, as well as an intriguing library for evolutionary and structural analyses.     

Involvement of nitric oxide in cerebroside-induced defense responses and taxol production in <Emphasis Type="Italic">Taxus yunnanensis</Emphasis> suspension cells

This work was to characterize the generation of nitric oxide (NO) in Taxus yunnanensis cells induced by a fungal-derived cerebroside and the signal role of NO in the elicitation of plant defense responses and taxol production. (2S,2′R,3R,3′E,4E,8E)-1-O-β-d-glucopyranosyl-2-N-(2′-hydroxy-3′-octadecenoyl)-3-hydroxy-9-methyl-4,8-sphingadienine at 10 μg/ml induced a rapid and dose-dependent NO production in the Taxus cell culture, reaching a maximum within 5 h of the treatment. The NO donor sodium nitroprusside (SNP) potentiated cerebroside-induced H₂O₂ production and cell death. Inhibition of nitric oxide synthase activity by phenylene-1,3-bis(ethane-2-isothiourea) dihydrobromide or scavenging NO by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide partially blocked the cerebroside-induced H₂O₂ production and cell death. Moreover, NO enhanced cerebroside-induced activation of phenylalanine ammonium-lyase and accumulation of taxol in cell cultures. These results are suggestive of a role for NO as a new signal component for activating the cerebroside-induced defense responses and secondary metabolism activities of plant cells. Taxol is a trademark of Bristol-Myers Squibb, Madison, NJ.     

大鼠原代肝细胞培养方法的建立

目的：探索混合胶原凝胶培养肝细胞的方法,观察培养鼠肝细胞的功能与形态特征,用于评价中药十八反的作用机理。方法：两步法分离鼠肝细胞,与鼠尾胶原溶液混合接种于培养板,观察培养鼠肝细胞的形态学特征和生化指标。采用RT-PCR技术。检测药物对P450亚酶CYP3A1表达的影响,进一步确证该体系的可靠性。结果：双层胶原培养体系可观察到典型的肝细胞形态特征,肝细胞功能检测显示肝细胞合成分泌的尿素、白蛋白,而乳酸脱氢酶漏出量较少。药物对P450亚酶CYP3A1表达的影响呈良好的剂量依赖性,同时双层胶原具有保持肝细胞活性的优点。可作为原代肝细胞培养的条件。结论：混合胶原凝胶培养能保留体内的细胞功能和活性,特别是保留药物代谢酶的活性。     

Reciprocal regulation of brain and muscle Arnt-like protein 1 and peroxisome proliferator-activated receptor alpha defines a novel positive feedback loop in the rodent liver circadian clock

Recent evidence has emerged that peroxisome proliferator-activated receptor alpha (PPARalpha), which is largely involved in lipid metabolism, can play an important role in connecting circadian biology and metabolism. In the present study, we investigated the mechanisms by which PPARalpha influences the pacemakers acting in the central clock located in the suprachiasmatic nucleus and in the peripheral oscillator of the liver. We demonstrate that PPARalpha plays a specific role in the peripheral circadian control because it is required to maintain the circadian rhythm of the master clock gene brain and muscle Arnt-like protein 1 (bmal1) in vivo. This regulation occurs via a direct binding of PPARalpha on a potential PPARalpha response element located in the bmal1 promoter. Reversely, BMAL1 is an upstream regulator of PPARalpha gene expression. We further demonstrate that fenofibrate induces circadian rhythm of clock gene expression in cell culture and up-regulates hepatic bmal1 in vivo. Together, these results provide evidence for an additional regulatory feedback loop involving BMAL1 and PPARalpha in peripheral clocks.     

SAR and molecular mechanism study of novel acylhydrazone compounds targeting HIV-1 CA

We synthesized a series of acylhydrazone compounds bearing naturally occurring amino acids’ side chains as HIV assembly inhibitors. Biological evaluation indicated that the compounds had anti-SIV and capsid assembly inhibitory activities. The structure–activity relationship (SAR) study showed that compounds bearing proper aromatic side chains had potential antiviral activities. The molecular modeling experiments revealed the molecular mechanism that they could bind to CA in the same manner as CAP-1 and occupy two more grooves.