杀菌剂对感染越冬桃小食心虫的白僵菌的抑制作用

【目的】桃小食心虫是我国果树上发生最普遍的食心类害虫,其室内人工饲养是综合防治研究的基础,但面临着田间越冬种群大量感染白僵菌死亡,给实验室种群的建立带来很大困难。因此筛选出对球孢白僵菌高效的杀菌剂用于解决桃小食心虫种群建立时感染白僵菌的问题。【方法】利用液体摇床振荡法和平皿十字交叉法测定16种常见杀菌剂对球孢白僵菌孢子萌发和菌丝生长的影响。【结果】筛选出9种杀菌剂,其中,腐霉利和中生菌素对孢子萌发的抑制效果好,常规用量抑制效果分别为97.88%±1.53%和93.22%±2.36%;抑霉唑和戊唑醇对菌丝生长的抑制效果明显,常规用量抑制效果分别达100.00%±0.00%和98.43%±0.99%;咪酰胺、丙环唑、噻菌灵、腈菌唑和吡唑醚菌酯对孢子萌发和菌丝生长的抑制效果都好。同时测定了这9种杀菌剂常规浓度及其5倍和10倍稀释液对桃小食心虫的毒力,结果表明有5种杀菌剂对桃小食心虫稍有不利影响。【结论】4种杀菌剂,中生菌素、戊唑醇、吡唑醚菌酯和噻菌灵可用于解决桃小食心虫种群建立时越冬幼虫的感染白僵菌问题。     

Leukotriene D4 induces amyloid-β generation via CysLT1R-mediated NF-κB pathways in primary neurons

Although the pathogenesis of sporadic Alzheimer’s disease (AD) is not clearly understood, neuroinflammation has been known to play a role in the pathogenesis of AD. To investigate a functional link between the neuroinflammation and AD, the effect of leukotriene D4 (LTD4), an inflammatory lipid mediator, was studied on amyloid-β generation in vitro. Application of LTD4 to cell monolayers at concentrations up to 40 nM LTD4 caused increases in the Aβ releases. Concentrations ?40 nM LTD4 decreased neuronal viability. Application of 20 nM LTD4 caused a significant increase in Aβ generation, as assessed by ELISA or Western blotting, without significant cytotoxicity. At this concentration, exposure of neurons to LTD4 for 24 h produced maximal effect in the Aβ generation, and significant increases in the expressions of cysteinyl leukotriene 1 receptor (CysLT₁R) and activity of β- or γ-secretase with complete abrogation by the selective CysLT₁R antagonist pranlukast. Exposure of neurons to LTD4 for 1 h showed activation of NF-κB pathway, by assessing the levels of p65 or phospho-p65 in the nucleus, and either CysLT₁R antagonist pranlukast or NF-κB inhibitor PDTC prevented the nuclear translocation of p65 and the consequent phosphorylation. PDTC also inhibited LTD4-induced elevations of β- or γ-secretase activity and Aβ generation in vitro. Overall, our data show for the first time that LTD4 causes Aβ production by enhancement of β- or γ-secretase resulting from activation of CysLT₁R-mediated NF-κB signaling pathway. These findings provide a novel pathologic link between neuroinflammation and AD.     

Membrane Permeation Induced by Aggregates of Human Islet Amyloid Polypeptides

Several neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases as well as nonneuropathic diseases such as type II diabetes and atrial amyloidosis are associated with aggregation of amyloid polypeptides into fibrillar structures, or plaques. In this study, we use molecular dynamics simulations to test the stability and orientation of membrane-embedded aggregates of the human islet amyloid polypeptide (hIAPP) implicated in type II diabetes. We find that in both monolayers and bilayers of dipalmitoylphosphatidylglycerol (DPPG) hIAPP trimers and tetramers remain inside the membranes and preserve their β-sheet secondary structure. Lipid bilayer-inserted hIAPP trimers and tetramers orient inside DPPG at 60° relative to the membrane/water interface and lead to water permeation and Na⁺ intrusion, consistent with ion-toxicity in islet β-cells. In particular, hIAPP trimers form a water-filled β-sandwich that induce water permeability comparable with channel-forming proteins, such as aquaporins and gramicidin-A. The predicted disruptive orientation is consistent with the amphiphilic properties of the hIAPP aggregates and could be probed by chiral sum frequency generation (SFG) spectroscopy, as predicted by the simulated SFG spectra.     

Nanoscale mapping and organization analysis of target proteins on cancer cells from B-cell lymphoma patients

CD20, a membrane protein highly expressed on most B-cell lymphomas, is an effective target demonstrated in clinical practice for treating B-cell non-Hodgkin's lymphoma (NHL). Rituximab is a monoclonal antibody against CD20. In this work, we applied atomic force microscopy (AFM) to map the nanoscale distribution of CD20 molecules on the surface of cancer cells from clinical B-cell NHL patients under the assistance of ROR1 fluorescence recognition (ROR1 is a specific cell surface marker exclusively expressed on cancer cells). First, the ROR1 fluorescence labeling experiments showed that ROR1 was expressed on cancer cells from B-cell lymphoma patients, but not on normal cells from healthy volunteers. Next, under the guidance of ROR1 fluorescence, the rituximab-conjugated AFM tips were moved to cancer cells to image the cellular morphologies and detect the CD20-rituximab interactions on the cell surfaces. The distribution maps of CD20 on cancer cells were constructed by obtaining arrays of (16×16) force curves in local areas (500×500 nm²) on the cell surfaces. The experimental results provide a new approach to directly investigate the nanoscale distribution of target protein on single clinical cancer cells.     

A single amino acid determines the catalytic efficiency of two alkenal double bond reductases produced by the liverwort Plagiochasma appendiculatum

Alkenal double bond reductases (DBRs) catalyze the NADPH-dependent reduction of the α,β-unsaturated double bond of many secondary metabolites. Two alkenal double bond reductase genes PaDBR1 and PaDBR2 were isolated from the liverwort species Plagiochasma appendiculatum. Recombinant PaDBR2 protein had a higher catalytic activity than PaDBR1 with respect to the reduction of the double bond present in hydroxycinnamyl aldehydes. The residue at position 56 appeared to be responsible for this difference in enzyme activity. The functionality of a C56 to Y56 mutation in PaDBR1 was similar to that of PaDBR2. Further site-directed mutagenesis and structural modeling suggested that the phenol ring stacking between this residue and the substrate was an important determinant of catalytic efficiency.     

Membrane Permeation Induced by Aggregates of Human Islet Amyloid Polypeptides

Several neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases as well as nonneuropathic diseases such as type II diabetes and atrial amyloidosis are associated with aggregation of amyloid polypeptides into fibrillar structures, or plaques. In this study, we use molecular dynamics simulations to test the stability and orientation of membrane-embedded aggregates of the human islet amyloid polypeptide (hIAPP) implicated in type II diabetes. We find that in both monolayers and bilayers of dipalmitoylphosphatidylglycerol (DPPG) hIAPP trimers and tetramers remain inside the membranes and preserve their β-sheet secondary structure. Lipid bilayer-inserted hIAPP trimers and tetramers orient inside DPPG at 60° relative to the membrane/water interface and lead to water permeation and Na⁺ intrusion, consistent with ion-toxicity in islet β-cells. In particular, hIAPP trimers form a water-filled β-sandwich that induce water permeability comparable with channel-forming proteins, such as aquaporins and gramicidin-A. The predicted disruptive orientation is consistent with the amphiphilic properties of the hIAPP aggregates and could be probed by chiral sum frequency generation (SFG) spectroscopy, as predicted by the simulated SFG spectra.     

Overwintering strategy of endoparasitoids in Chilo suppressalis: a perspective from the cold hardiness of a host

Although parasitoids ultimately kill their host, koinobiont parasitoids must protect not only themselves but also their hosts against extreme environments. In this study, the parasitism rate of Chilo suppressalis Walker (Lepidoptera: Pyralidae) was investigated, and the average body weights, supercooling points, and concentrations of glycerol (acting as a cryoprotectant) in the hemolymph were compared between parasitized and non‐parasitized larvae. Five species of koinobiont endoparasitoids parasitized the overwintering C. suppressalis larvae and the total parasitism rate was 47.6% (n = 1 537). Average body weight of parasitized larvae was significantly lower than that of non‐parasitized larvae, and the parasitism rate of the lighter group (20–30 mg) was highest. The supercooling point of parasitized C. suppressalis larvae (?15.7 ± 0.3 °C) was significantly lower than that of the non‐parasitized larvae (?14.3 ± 0.2 °C). In addition, supercooling points were not correlated with body weights between parasitized and non‐parasitized larvae, indicating that cold hardiness of parasitized larvae was enhanced by endoparasitoids. Furthermore, the concentration of glycerol in the hemolymph was significantly higher in parasitized larvae (205.0 ± 7.1 μmol ml^?1) than in non‐parasitized larvae (169.8 ± 14.4 μmol ml^?1), which suggests that the mechanism that decreases the supercooling point of parasitized larvae was associated with glycerol. All these results indicated that the cold hardiness of parasitized C. suppressalis larvae was enhanced by their endoparasitoids, which benefitted overwintering endoparasitoids.