Antibodies to envelope glycoprotein of dengue virus during the natural course of infection are predominantly cross-reactive and recognize epitopes containing highly conserved residues at the fusion loop of domain II

The antibody response to the envelope (E) glycoprotein of dengue virus (DENV) is known to play a critical role in both protection from and enhancement of disease, especially after primary infection. However, the relative amounts of homologous and heterologous anti-E antibodies and their epitopes remain unclear. In this study, we examined the antibody responses to E protein as well as to precursor membrane (PrM), capsid, and nonstructural protein 1 (NS1) of four serotypes of DENV by Western blot analysis of DENV serotype 2-infected patients with different disease severity and immune status during an outbreak in southern Taiwan in 2002. Based on the early-convalescent-phase sera tested, the rates of antibody responses to PrM and NS1 proteins were significantly higher in patients with secondary infection than in those with primary infection. A blocking experiment and neutralization assay showed that more than 90% of anti-E antibodies after primary infection were cross-reactive and nonneutralizing against heterologous serotypes and that only a minor proportion were type specific, which may account for the type-specific neutralization activity. Moreover, the E-binding activity in sera of 10 patients with primary infection was greatly reduced by amino acid replacements of three fusion loop residues, tryptophan at position 101, leucine at position 107, and phenylalanine at position 108, but not by replacements of those outside the fusion loop of domain II, suggesting that the predominantly cross-reactive anti-E antibodies recognized epitopes involving the highly conserved residues at the fusion loop of domain II. These findings have implications for our understanding of the pathogenesis of dengue and for the future design of subunit vaccine against DENV as well.     

Ultrathin Co3O4 Layers with Large Contact Area on Carbon Fibers as High‐Performance Electrode for Flexible Zinc–Air Battery Integrated with Flexible Display

A facile and binder‐free method is developed for the in situ and horizontal growth of ultrathin mesoporous Co₃O₄ layers on the surface of carbon fibers in the carbon cloth (ultrathin Co₃O₄/CC) as high‐performance air electrode for the flexible Zn–air battery. In particular, the ultrathin Co₃O₄ layers have a maximum contact area on the conductive support, facilitating the rapid electron transport and preventing the aggregation of ultrathin layers. The ultrathin feature of Co₃O₄ layers is characterized by the transmission electron microscopy, Raman spectra, and X‐ray absorption fine structure spectroscopy. Benefiting from the high utilization degree of active materials and rapid charge transport, the mass activity for oxygen reduction and evolution reactions of the ultrathin Co₃O₄/CC electrode is more than 10 times higher than that of the carbon cloth loaded with commercial Co₃O₄ nanoparticles. Compared to the commercial Co₃O₄/CC electrode, the flexible Zn–air battery using ultrathin Co₃O₄/CC electrode exhibits excellent rechargeable performance and high mechanical stability. Furthermore, the flexible Zn–air battery is integrated with a flexible display unit. The whole integrated device can operate without obvious performance degradation under serious deformation and even during the cutting process, which makes it highly promising for wearable and roll‐up optoelectronics.     

Pou4f2‐GFP knock‐in mouse line: A model for studying retinal ganglion cell development

Pou4f2 acts as a key node in the comprehensive and step‐wise gene regulatory network (GRN) and regulates the development of retinal ganglion cells (RGCs). Accordingly, deletion of Pou4f2 results in RGC axon defects and apoptosis. To investigate the GRN involved in RGC regeneration, we generated a mouse line with a POU4F2‐green fluorescent protein (GFP) fusion protein expressed in RGCs. Co‐localization of POU4F2 and GFP in the retina and brain of Pou4f2‐GFP/+ heterozygote mice was confirmed using immunofluorescence analysis. Compared with those in wild‐type mice, the expression patterns of POU4F2 and POU4F1 and the co‐expression patterns of ISL1 and POU4F2 were unaffected in Pou4f2‐GFP/GFP homozygote mice. Moreover, the quantification of RGCs showed no significant difference between Pou4f2‐GFP/GFP homozygote and wild‐type mice. These results demonstrated that the development of RGCs in Pou4f2‐GFP/GFP homozygote mice was the same as in wild‐type mice. Thus, the present Pou4f2‐GFP knock‐in mouse line is a useful tool for further studies on the differentiation and regeneration of RGCs.     

防御素(Defensin)研究进展

防御素(Defensin)是近年来发现的广泛存在于动物和植物体内的一类阳离子抗菌活性肽。它们通常都是由28～54个氨基酸残基组成,分子内富含精氨酸和由半胱氨酸形成的分子内二硫键。它们具有广谱高效的杀菌活性,能有效地杀灭革兰氏阳性菌、革兰氏阴性菌、某些真菌、螺旋体、被膜病毒等微生物,因而对它们的研究已成为当前国际学术界中一个引人关注的研究热点。本文将简述有关防御素的分布、分子结构特征、生物学活性、作用机制、分子生物学特征等方面的研究概况及展望。     

Genetic analyses and mapping of a new thermo-sensitive genic male sterile gene in maize

The present study describes a novel thermo-sensitive genic male sterile (TGMS) line, Qiong68ms. To analyse the mode of fertility inheritance and tag the TGMS gene, a set of F₂, BC₁ and F_2:3 populations derived from a cross between Qiong68ms and K12 were evaluated for a period of 2 years. Classical genetic analyses and QTL mapping using the mean restoration percentage of the F_2:3 populations revealed that the fertility of Qiong68ms was likely to be governed by a single recessive gene, which was named tms3; the tms3 gene was mapped to a location between SSR markers umc2129 and umc1041, at a distance of 3.7 cM form umc2129 and 1.5 cM form umc1041. The molecular markers tightly linked with tms3 gene will aid in the transfer of the TGMS gene to various background inbred lines using the MAS method.     

Determination of the baculovirus transducing titer in mammalian cells

Baculovirus has emerged as a promising vector for in vivo or ex vivo gene therapy. To date, the infectious titer and multiplicity of infection (MOI) based on the ability of baculovirus to infect insect cells are commonly adopted to indicate the virus dosage. However, the infectious titer and MOI do not reliably represent the baculovirus transducing ability, making the comparison of baculovirus-mediated gene transfer difficult. To determine the baculovirus transducing ability more rapidly and reliably, we developed a protocol to evaluate the transducing titers of baculovirus stocks. The virus was diluted twofold serially and used to transduce HeLa cells. The resultant transduction efficiencies were measured by flow cytometry for the calculation of transducing titers. Compared to the infectious titer, the determination of transducing titer is more reproducible as the standard deviations among measurements are smaller. Also, the transducing titers can be obtained in 24 h, which is significantly faster as opposed to 4-7 days to obtain the infectious titer. More importantly, we demonstrated that baculoviruses with higher transducing titers could transduce cells at higher efficiency and yield stronger and longer transgene expression, confirming that the transducing titer was representative of the baculovirus transducing ability. This finding is particularly significant for ex vivo gene delivery whereby unconcentrated viruses are used for transduction and long-term transgene expression is desired. In this regard, our titration protocol provides a simple, fast, and reliable measure to evaluate the quality of virus stocks during virus production and purification, and is helpful to predict the performance of vector supernatants and ensure reproducible gene delivery experiments.     

Endothelial FAK is essential for vascular network stability, cell survival, and lamellipodial formation

Morphogenesis of a vascular network requires dynamic vessel growth and regression. To investigate the cellular mechanism underlying this process, we deleted focal adhesion kinase (FAK), a key signaling mediator, in endothelial cells (ECs) using Tie2-Cre mice. Targeted FAK depletion occurred efficiently early in development, where mutants exhibited a distinctive and irregular vasculature, resulting in hemorrhage and lethality between embryonic day (e) 10.5 and 11.5. Capillaries and intercapillary spaces in yolk sacs were dilated before any other detectable abnormalities at e9.5, and explants demonstrate that the defects resulted from the loss of FAK and not from organ failure. Time-lapse microscopy monitoring EC behavior during vascular formation in explants revealed no apparent decrease in proliferation or migration but revealed increases in cell retraction and death leading to reduced vessel growth and increased vessel regression. Consistent with this phenotype, ECs derived from mutant embryos exhibited aberrant lamellipodial extensions, altered actin cytoskeleton, and nonpolarized cell movement. This study reveals that FAK is crucial for vascular morphogenesis and the regulation of EC survival and morphology.     

5'-(2-Nitrophenylalkanoyl)-2'-deoxy-5-fluorouridines as potential prodrugs of FUDR for reductive activation

Four 5'-(2-nitrophenylalkanoyl)-2'-deoxy-5-fluorouridines (1a-d) were designed and synthesized as potential prodrugs of FUDR for reductive activation. Two methyl groups were introduced alpha to the ester carbonyl to increase both the rate of cyclization activation and the stability of the conjugates towards serum esterases. Chemical reduction of the nitro group into an amino leads to cyclization and release of the active FUDR. Kinetic analysis of the cyclization activation process indicates that the two methyl groups alpha to the ester carbonyl restrict the rotational freedom of ground state molecule and promote the cyclization reaction. However, the two methyl groups also were found to render the conjugates as poor substrates of E. coli B nitroreductase. Conjugate 1c, without the two methyl groups, was reduced by E. coli B nitroreductase (t(1/2)=8 h) to give two products, a N-hydroxyl lactam and the drug FUDR, suggesting that the enzymatic reduction and subsequent cyclization activation proceeded through the hydroxylamine intermediate. These results indicate that cyclization activation will occur once the nitro group is reduced either to an amino or to a hydroxylamino group. The fact that the amino intermediates cyclized easily to release the incorporated drug FUDR suggests the feasibility of using peptide-linked acyl 2-aminophenylalkanoic acid esters as potential prodrugs for proteolytic activation.     

The effects of post-stroke upper-limb training with an electromyography (EMG)-driven hand robot

Loss of hand function and finger dexterity are main disabilities in the upper limb after stroke. An electromyography (EMG)-driven hand robot had been developed for post-stroke rehabilitation training. The effectiveness of the hand robot assisted whole upper limb training was investigated on persons with chronic stroke (n = 10) in this work. All subjects attended a 20-session training (3–5 times/week) by using the hand robot to practice object grasp/release and arm transportation tasks. Significant motor improvements were observed in the Fugl-Meyer hand/wrist and shoulder/elbow scores (p < 0.05), and also in the Action Research Arm Test and Wolf Motor Function Test (p < 0.05). Significant reduction in spasticity of the fingers as was measured by the Modified Ashworth Score (p < 0.05). The training improved the muscle co-ordination between the antagonist muscle pair (flexor digitorum (FD) and extensor digitorum (ED)), associated with a significant reduction in the ED EMG level (p < 0.05) and a significant decrease of ED and FD co-contraction during the training (p < 0.05); the excessive muscle activities in the biceps brachii were also reduced significantly after the training (p < 0.05).