小分子干扰RNA对斑马鱼VEGF基因的沉默作用

运用RNA干扰技术,针对斑马鱼血管内皮生长因子(VEGF)基因设计并合成了特异性小分子干扰RNA(siRNA),并从血管形成水平研究了siRNA对VEGF基因表达的影响。为了得到能在体内稳定表达的siRNA,进一步以pSilencer4.1-CMVVector为载体,合成了短发夹RNA(shRNA)表达模板并定向克隆到CMV启动子下游,构建了shRNA表达载体。定量碱性磷酸酶染色显示注射合成的siRNA后胚胎新血管生成(angiogenesis)为71.8%,NBT/BCIP血管染色显示表达载体可以引起斑马鱼胚胎肠下静脉、节间血管发育缺陷,原位杂交结果显示胚胎头部及前原肾管部位VEGF表达异常。     

VEGF功能化二氧化钛纳米管对内皮细胞生长的协同效应研究

将血管内皮细胞生长因子(VEGF)以共价键方式固定在直径为30nm、60nm和100nm的TiO2纳米管表面,探究钛材表面纳米结构和生长因子对细胞生长的协同影响。采用扫描电子显微镜(SEM)、接触角及X射线光电子能谱仪(XPS)对材料进行了表征,结果表明,VEGF有效地固定在TiO2纳米管阵列薄膜上。接种在VEGF功能化的TiO2纳米管上的人脐静脉内皮细胞(HUVEC)较对照组有更高的活力(p<0.01);其中,30nm的TiO2纳米管上面VE-钙黏蛋白的表达量和前列环素(PGI2)的分泌量较100nm的TiO2纳米管和对照组有显著统计差异性(p<0.01)。该结果表明VEGF和TiO2纳米管的管径(纳米拓扑结构)协同增效地促进了HUVEC生长及功能表达。     

Inhibitory activity of gold and silica nanospheres to vascular endothelial growth factor （VEGF）-mediated angiogenesis is determined by their sizes

Nanoparticles can be involved in biological activities such as apoptosis, angiogenesis, and oxidative stress by themselves. In particular, inorganic nanoparticles such as gold and silica nanoparticles are known to inhibit vascular endothelial growth factor （VEGF）-mediated pathological angiogenesis. In this study, we show that anti-angiogenic effect of inorganic nanospheres is determined by their sizes. We demonstrate that 20 nm size gold and silica nanospheres suppress VEGF-induced activation of VEGF receptor-2, in vitro angiogenesis, and in vivo pathological angiogenesis more efficiently than their 100 nm size counterparts. Our results suggest that modulation of the size of gold and silica nanospheres determines their inhibitory activity to VEGF-mediated angiogenesis.     

Mathematical models of the transitions between endocrine therapy responsive and resistant states in breast cancer

Endocrine therapy, targeting the oestrogen receptor pathway, is the most common treatment for oestrogen receptor-positive breast cancers. Unfortunately, these tumours frequently develop resistance to endocrine therapies. Among the strategies to treat resistant tumours are sequential treatment (in which second-line drugs are used to gain additional responses) and intermittent treatment (in which a ‘drug holiday’ is imposed between treatments). To gain a more rigorous understanding of the mechanisms underlying these strategies, we present a mathematical model that captures the transitions among three different, experimentally observed, oestrogen-sensitivity phenotypes in breast cancer (sensitive, hypersensitive and independent). To provide a global view of the transitions between these phenotypes, we compute the potential landscape associated with the model. We show how this oestrogen response landscape can be reshaped by population selection, which is a crucial force in promoting acquired resistance. Techniques from statistical physics are used to create a population-level state-transition model from the cellular-level model. We then illustrate how this population-level model can be used to analyse and optimize sequential and intermittent oestrogen-deprivation protocols for breast cancer. The approach used in this study is general and can also be applied to investigate treatment strategies for other types of cancer.     

Mechanical Cues Regulating Proangiogenic Potential of Human Mesenchymal Stem Cells through YAP‐Mediated Mechanosensing

Stem cells secrete trophic factors that induce angiogenesis. These soluble factors are promising candidates for stem cell–based therapies, especially for cardiovascular diseases. Mechanical stimuli and biophysical factors presented in the stem cell microenvironment play important roles in guiding their behaviors. However, the complex interplay and precise role of these cues in directing pro‐angiogenic signaling remain unclear. Here, a platform is designed using gelatin methacryloyl hydrogels with tunable rigidity and a dynamic mechanical compression bioreactor to evaluate the influence of matrix rigidity and mechanical stimuli on the secretion of pro‐angiogenic factors from human mesenchymal stem cells (hMSCs). Cells cultured in matrices mimicking mechanical elasticity of bone tissues in vivo show elevated secretion of vascular endothelial growth factor (VEGF), one of representative signaling proteins promoting angiogenesis, as well as increased vascularization of human umbilical vein endothelial cells (HUVECs) with a supplement of conditioned media from hMSCs cultured across different conditions. When hMSCs are cultured in matrices stimulated with a range of cyclic compressions, increased VEGF secretion is observed with increasing mechanical strains, which is also in line with the enhanced tubulogenesis of HUVECs. Moreover, it is demonstrated that matrix stiffness and cyclic compression modulate secretion of pro‐angiogenic molecules from hMSCs through yes‐associated protein activity.     

Rapid and accurate ranking of binding affinities of epidermal growth factor receptor sequences with selected lung cancer drugs

The epidermal growth factor receptor (EGFR) is a major target for drugs in treating lung carcinoma. Mutations in the tyrosine kinase domain of EGFR commonly arise in human cancers, which can cause drug sensitivity or resistance by influencing the relative strengths of drug and ATP-binding. In this study, we investigate the binding affinities of two tyrosine kinase inhibitors—AEE788 and Gefitinib—to EGFR using molecular dynamics simulation. The interactions between these inhibitors and the EGFR kinase domain are analysed using multiple short (ensemble) simulations and the molecular mechanics/Poisson–Boltzmann solvent area (MM/PBSA) method. Here, we show that ensemble simulations correctly rank the binding affinities for these systems: we report the successful ranking of each drug binding to a variety of EGFR sequences and of the two drugs binding to a given sequence, using petascale computing resources, within a few days.     

The role of ECL2 in CGRP receptor activation: a combined modelling and experimental approach

The calcitonin gene-related peptide (CGRP) receptor is a complex of a calcitonin receptor-like receptor (CLR), which is a family B G-protein-coupled receptor (GPCR) and receptor activity modifying protein 1. The role of the second extracellular loop (ECL2) of CLR in binding CGRP and coupling to Gs was investigated using a combination of mutagenesis and modelling. An alanine scan of residues 271–294 of CLR showed that the ability of CGRP to produce cAMP was impaired by point mutations at 13 residues; most of these also impaired the response to adrenomedullin (AM). These data were used to select probable ECL2-modelled conformations that are involved in agonist binding, allowing the identification of the likely contacts between the peptide and receptor. The implications of the most likely structures for receptor activation are discussed.     

The role of evolutionary game theory in spatial and non-spatial models of the survival of cooperation in cancer: a review

Evolutionary game theory (EGT) is a branch of mathematics which considers populations of individuals interacting with each other to receive pay-offs. An individual’s pay-off is dependent on the strategy of its opponent(s) as well as on its own, and the higher its pay-off, the higher its reproductive fitness. Its offspring generally inherit its interaction strategy, subject to random mutation. Over time, the composition of the population shifts as different strategies spread or are driven extinct. In the last 25 years there has been a flood of interest in applying EGT to cancer modelling, with the aim of explaining how cancerous mutations spread through healthy tissue and how intercellular cooperation persists in tumour-cell populations. This review traces this body of work from theoretical analyses of well-mixed infinite populations through to more realistic spatial models of the development of cooperation between epithelial cells. We also consider work in which EGT has been used to make experimental predictions about the evolution of cancer, and discuss work that remains to be done before EGT can make large-scale contributions to clinical treatment and patient outcomes.     

非均质表皮层径向双层承压井流数学模型的半解析解

考虑表皮层和未扰动承压层的非均质性、各向异性以及竖向越流补给作用,建立了径向双层承压三维井流的数学模型,采用Laplace变换和矩阵理论求得表皮层和未扰动承压层的水头降以及井壁流量的半解析解.应用所求解编制计算程序,分析了表皮层沿竖向随机变化的渗透性对承压层井流的影响,结果表明:表皮层非均质变化形态决定了表皮层内和其附近处的水头降以及井壁流量的竖向分布规律,表皮层对承压层渗流产生的影响范围与承压层的竖向渗透系数大小有关;改善井周岩土介质渗透性或增大"负表皮层"厚度可提高抽水井产量;表皮层径向渗透系数较小时,承压层的水头降幅度主要取决于承压层径向渗透系数的大小,而当表皮层径向渗透系数较大时,承压层径向渗透系数和竖向渗透系数均对承压层水头降有较大影响.     

The perovskite structure – a review of its role in ceramic science and technology

Starting with the history of the fundamental science of the relation of structure to composition delineated completely by Goldschmidt, we use the perovskite structure to illustrate the enormous power of crystal chemistry-based intelligent synthesis in creating new materials. The perovskite structure is shown to be the single most versatile ceramic host. By appropriate changes in composition one can modify the most significant electroceramic dielectric (BaTiO₃ and its relatives) phase in industry, into metallic conductors, superconductors or the highest pressure phases in the earth. After an historical introduction of the science, detailed treatment of the applications is confined to the most recent research on novel uses in piezoelectric, ferroelectric and related applications. Received: 29 November 1999 / Accepted: 3 July 2000     

Facile deposition of polyvinylpyrrolidone-grafted multi-walled carbon nanotube on glassy carbon electrode and its application in the sensing of biomolecules

Polyvinylpyrrolidone-grafted multi-walled carbon nanotube (PVP/MWCNT) was deposited on carboxylated glassy carbon electrode (GCE) from acidic water via the electrostatic force between the positively charged PVP/MWCNTs and negatively charged GCE. It was found out that PVP/MWCNT-modified GCE (PVP/MWCNT/GCE) exhibited great catalytic capability for the oxidation of dopamine (DA), uric acid (UA), tyrosine (Tyr) and nitrite) by enhancing their oxidation currents and lowering their overpotentials. For PVP/MWCNT/GCE, the linear calibration plots for DA, UA, Tyr and nitrite were obtained over the range of 0.1–50 μM, 1–500 μM, 1–200 μM and 1–500 μM with detection limits of 0.04 μM, 0.17 μM, 0.26 μM and 0.30 μM, respectively. In addition, satisfactory results were obtained by applying PVP/MWCNT/GCE in the determination of DA, UA, Tyr and nitrite in human serum samples with standard addition method.     

TEM and HRTEM evidence for the role of ligands in the formation of shape-controlled platinum nanoparticles

The morphology of platinum nanoparticles synthesized using an organometallic approach from PtMe(2) (C(8) H(12) ) is influenced by the nature of the ligands used as stabilizing agents. The use of long alkyl chain amines leads to the formation of multipodal nanoparticles that transform into compact nano-objects, adopting cubic, truncated cubic, or cuboctahedral shapes. In contrast, the use of diamine ligands allows the growth of compact (111) arrowlike faces, forming polycrystalline nanoparticles of an overall desert-rose aspect. Different reaction parameters are studied ([ligand]/[metal] ratio, temperature, solvent identity) in order to optimize the various shapes.     

A quantitative investigation of the role of information and communication technologies in the implementation of a product-service system

This paper reports evidence from a survey, aimed at testing whether and how Information and Communication Technologies (ICTs), which enable the adoption of product-service systems, can contribute to value creation. This analysis builds on previous contributions, according to which companies that are enriching their product offering through value-added services (the so-called servitisation strategy) often report lower levels of profitability, owing to the poor performance of their operating process. A wide stream of research claims that companies that invest in ICTs can enjoy valuable outcomes, since the adoption of such technologies results in processes that are more efficient and more responsive. Our hypothesis concerns the possibility of leveraging ICTs at operating process level so as to pursue a servitisation strategy. The in-field analysis presented in this paper concerns a sample of 109 companies located in Italy; data collected through the survey have been analysed using the structural equation modelling approach. The evidence presented demonstrates that ICTs can have a relevant impact on value creation because they lead to superior responsiveness of operating processes and to sound improvements in the product offering. In particular, companies that are able to embed such superior responsiveness into their product offering can further boost value creation.     

Modelling the functional roles of synaptic and extra-synaptic γ-aminobutyric acid receptor dynamics in circadian timekeeping

In the suprachiasmatic nucleus (SCN), γ-aminobutyric acid (GABA) is a primary neurotransmitter. GABA can signal through two types of GABA_A receptor subunits, often referred to as synaptic GABA_A (gamma subunit) and extra-synaptic GABA_A (delta subunit). To test the functional roles of these distinct GABA_A in regulating circadian rhythms, we developed a multicellular SCN model where we could separately compare the effects of manipulating GABA neurotransmitter or receptor dynamics. Our model predicted that blocking GABA signalling modestly increased synchrony among circadian cells, consistent with published SCN pharmacology. Conversely, the model predicted that lowering GABA_A receptor density reduced firing rate, circadian cell fraction, amplitude and synchrony among individual neurons. When we tested these predictions, we found that the knockdown of delta GABA_A reduced the amplitude and synchrony of clock gene expression among cells in SCN explants. The model further predicted that increasing gamma GABA_A densities could enhance synchrony, as opposed to increasing delta GABA_A densities. Overall, our model reveals how blocking GABA_A receptors can modestly increase synchrony, while increasing the relative density of gamma over delta subunits can dramatically increase synchrony. We hypothesize that increased gamma GABA_A density in the winter could underlie the tighter phase relationships among SCN cells.     

Spatio-temporal development of the endothelial glycocalyx layer and its mechanical property in vitro

The endothelial glycocalyx is a thin layer of polysaccharide matrix on the luminal surface of endothelial cells (ECs), which contains sulphated proteoglycans and glycoproteins. It is a mechanotransducer and functions as an amplifier of the shear stress on ECs. It controls the vessel permeability and mediates the blood–endothelium interaction. This study investigates the spatial distribution and temporal development of the glycocalyx on cultured ECs, and evaluates mechanical properties of the glycocalyx using atomic force microscopy (AFM) nano-indentation. The glycocalyx on human umbilical vein endothelial cells (HUVECs) is observed under a confocal microscope. Manipulation of the glycocalyx is achieved using heparanase or neuraminidase. The Young''s modulus of the cell membrane is calculated from the force–distance curve during AFM indentation. Results show that the glycocalyx appears predominantly on the edge of cells in the early days in culture, e.g. up to day 5 after seeding. On day 7, the glycocalyx is also seen in the apical area of the cell membrane. The thickness of the glycocalyx is approximately 300 nm–1 μm. AFM indentation reveals the Young''s modulus of the cell membrane decreases from day 3 (2.93 ± 1.16 kPa) to day 14 (0.35 ± 0.15 kPa) and remains unchanged to day 21 (0.33 ± 0.19 kPa). Significant difference in the Young''s modulus is also seen between the apical (1.54 ± 0.58 kPa) and the edge (0.69 ± 0.55 kPa) of cells at day 7. By contrast, neuraminidase-treated cells (i.e. without the glycocalyx) have similar values between day 3 (3.18 ± 0.88 kPa), day 14 (2.12 ± 0.78 kPa) and day 21 (2.15 ± 0.48 kPa). The endothelial glycocalyx in vitro shows temporal development in the early days in culture. It covers predominantly the edge of cells initially and appears on the apical membrane of cells as time progresses. The Young''s modulus of the glycocalyx is deduced from Young''s moduli of cell membranes with and without the glycocalyx layer. Our results show the glycocalyx on cultured HUVECs has a Young''s modulus of approximately 0.39 kPa.     

Invasion,persistence and control in epidemic models for plant pathogens: the effect of host demography

Many epidemiological models for plant disease include host demography to describe changes in the availability of susceptible tissue for infection. We compare the effects of using two commonly used formulations for host growth, one linear and the other nonlinear, upon the outcomes for invasion, persistence and control of pathogens in a widely used, generic model for botanical epidemics. The criterion for invasion, reflected in the basic reproductive number, R₀, is unaffected by host demography: R₀ is simply a function of epidemiological parameters alone. When, however, host growth is intrinsically nonlinear, unexpected results arise for persistence and the control of disease. The endemic level of infection (I_∞) also depends upon R₀. We show, however, that the sensitivity of I_∞ to changes in R₀ > 1 depends upon which underlying epidemiological parameter is changed. Increasing R₀ by shortening the infectious period results in a monotonic increase in I_∞. If, however, an increase in R₀ is driven by increases in transmission rates or by decreases in the decay of free-living inoculum, I_∞ first increases (R₀ < 2), but then decreases (R₀ > 2). This counterintuitive result means that increasing the intensity of control can result in more endemic infection.