Recent Advances in the Treatment of Duodenal Ulcer Disease: A Surgical Perspective

Chronic peptic ulceration is a disease process in transition. During the past two decades, the disease has changed in its incidence, in its presentation and in its medical consequences. The pathogenesis of acid-peptic disease has been the major focus of numerous investigations, and major advances in understanding basic gastric physiology have led to specific and increasingly effective therapeutic approaches. With the introduction of H₂-receptor antagonists, the treatment of peptic ulceration has been radically altered, and many new therapies await clinical trial. Surgeons treating gastroduodenal ulceration will require greater knowledge of gastric physiology and an increasingly refined appreciation of both the power and limitations of various medical and surgical therapies.     

陆地生态系统碳循环模型研究概述

陆地碳循环研究是全球变化研究中的一个重要组成部分,而碳循环模型已成为目前研究陆地碳循环的必要手段.本文针对有关碳循环研究方面的进展,介绍了陆地碳循环模型的基本结构、碳循环过程中涉及的两个基本模型以及目前陆地生态系统碳循环模型的两大类型,并通过对现有主要陆地生态系统碳收支模式的分析,指出了未来陆地碳循环模型的研究方向可能是发展基于动态植被的生物物理模型.这种耦合模型也可能是地球系统模式的重要组成部分.     

木聚糖酶分子结构与重要酶学性质关系的研究进展

木聚糖是一种多聚五碳糖 ,是植物细胞中主要的半纤维素成分。木聚糖酶是可将木聚糖降解成低聚木糖和木糖的水解酶 ,它在饲料、造纸、食品、能源工业和环境科学上有着广阔的应用前景。随着分子生物学、结构生物学的发展及蛋白质工程的应用 ,对木聚糖酶结构和功能的研究不断深入。这里重点阐述与酶的活性、热稳定性、作用pH、等电点、底物亲和性及催化效率等重要性质相关的分子结构研究进展 ,讨论了其进一步的研究发展方向。研究木聚糖酶结构与功能的关系 ,对进一步加深木聚糖酶作用机制的了解、指导木聚糖酶的分子改良有重要意义。     

Thermal Behavior, Microstructure, Polymorphism, and Crystallization Properties of Zero Trans Fats from Soybean Oil and Fully Hydrogenated Soybean Oil

Blends of soybean oil (SO) and fully hydrogenated soybean oil (FHSBO), with 10, 20, 30, 40, and 50% (w/w) FHSBO content were interesterified under the following conditions: 20 min reaction time, 0.4% sodium methoxide catalyst, and 500 rpm stirring speed, at 100 °C. The original and interesterified blends were examined for triacylglycerol composition, thermal behavior, microstructure, crystallization kinetics, and polymorphism. Interesterification produced substantial rearrangement of the triacylglycerol species in all the blends, reduction of trisaturated triacylglycerol content and increase in monounsaturated–disaturated and diunsaturated–monosaturated triacylglycerols. Evaluation of thermal behavior parameters showed linear relations with FHSBO content in the original blends. Blend melting and crystallization thermograms were significantly modified by the randomization. Interesterification caused significant reductions in maximum crystal diameter in all blends, in addition to modifying crystal morphology. Characterization of crystallization kinetics revealed that crystal formation induction period (τ _SFC) and maximum solid fat content (SFC_máx) were altered according to FHSBO content in the original blends and as a result of the random rearrangement. Changes in Avrami constant (k) and exponent (n) indicated, respectively, that—as compared with the original blends—interesterification decreased crystallization velocities and modified crystallization processes, altering crystalline morphology and nucleation mechanism. X-ray diffraction analyses revealed that interesterification altered crystalline polymorphism. The interesterified blends showed a predominance of the β′ polymorph, which is of more interest for food applications.     

Recent progress in the synthesis of carbohydrate-based amphiphilic materials: the examples of sucrose and isomaltulose

In the context of the use of carbohydrates obtained from agricultural crops, the search for amphiphilic derivatives is one of the most developed aspects. Indeed, due to the high polarity and the functional richness of sugars, many different structures can be targeted, with a wide range of physicochemical properties, either for large scale products of industrial interest, or for fine applications at the chemistry-biology interface. Among carbohydrates arising from agricultural resources, sucrose is especially interesting because of its very large production scale in the world (ca. 160Mt/year, ca. 20Mt/year of which in the European Community). Here, we describe the research accomplished in our group dealing with the synthesis and the study of the properties of amphiphilic derivatives prepared from sucrose as well as from another very available disaccharide, isomaltulose.     

Recent Advances in Polymer Electrolytes for Zinc Ion Batteries: Mechanisms,Properties, and Perspectives

Aqueous rechargeable zinc ion batteries (ZIBs) have been deemed to be possible candidates for large‐scale energy storage due to their ecoefficiency, substantial reserve, safety, and low cost. However, the challenges inherent in aqueous electrolytes, such as water splitting reactions, water evaporation, and liquid leakage, have greatly hindered their development in energy storage. Fortunately, polymer electrolytes would be able to overcome the abovementioned challenges. Moreover, the flexible properties of polymer electrolytes can facilitate their future application in wearable electronics. Recently, increasing attention has been attracted to the polymer electrolyte‐based zinc ion batteries. However, the development of polymer electrolytes for ZIBs is still in the early stages due to numerous challenges. Therefore, substantial research effort is required to overcome the challenges of polymer electrolyte‐based ZIBs. In this review, the current progress in developing polymer electrolytes, including solid polymer electrolytes, gel polymer electrolytes, and hybrid polymer electrolytes, as well as the interactions between electrodes and polymer electrolytes for ZIBs is comprehensively reviewed, analyzed, and discussed in terms of their synthesis, characterization, and performance validation. To facilitate further research and development of polymer electrolytes for ZIBs, the relevant challenges are summarized and analyzed, and some underlying approaches to overcome these challenges are also proposed.     

Prevalent Mutations of Human Prion Protein: A Molecular Modeling and Molecular Dynamics Study

Abstract

Point mutations in the human prion protein gene, leading to amino acid substitutions in the human prion protein contribute to conversion of PrP^C to PrP^Sc and amyloid formation, resulting in prion diseases such as familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker disease (GSS), and fatal familial insomnia. We have investigated impressions of prevalent mutations including Q217R, D202N, F198S, on the human prion protein and compared the mutant models with wild types. Structural analyses of models were performed with molecular modeling and molecular dynamics simulation methods. According to our results, frequently occurred mutations are observed in conserved and fully conserved sequences of human prion protein and the most fluctuation values occur in the Helix 1 around residues 144–152 and C-terminal end of the Helix 2. Our analysis of results obtained from MD simulation clearly shows that this long-range effect plays an important role in the conformational fluctuations in mutant structures of human prion protein. Results obtained from molecular modeling such as creation or elimination of some hydrogen bonds, increase or decrease of the accessible surface area and molecular surface, loss or accumulation of negative or positive charges on specific positions, and altering the polarity and pKa values, show that amino acid point mutations, though not urgently change the stability of PrP, might have some local impacts on the protein interactions which are required for oligomerization into fibrillar species.     

人脑和人血清胆碱酯酶三维结构的计算机模拟研究

本文以同源的电鳐胆碱酯酶（Ｔ．ＡＣｈＥ）的三维结构为模板,模拟预测了人脑和血清胆碱酯酶（Ｈ。ＡＣｈＥ和Ｈ．ＢｕＣｈＥ）的三维结构和活力中心的组成。指Ｔ．ＡＣｈＥ,Ｈ．ＡＣｈＥ和Ｈ．ＢｕＣｈＥ宁间结构差异,并讨论了ＡＣｈ和Ｈ。ＡＣｈＥ的对接（ｄｏｃｋｉｎｇ）。Ｈ。ＡＣｈＥ和Ｈ．ＢｕＣｈＥ三维结构的确定将为进一步深入研究它的中毒机理和合理药物设计提供靶子。     

Effects of Acidification, Sodium Chloride, and Moisture Levels on Wheat Dough: I. Modeling of Rheological and Microstructural Properties

The rheological attributes of polymers as wheat dough are strongly related to its microstructure. To quantify dough protein microstructure confocal laser scanning microscopy combined with image analysis was used. The effect of three experimental factors pH (addition of lactic acid and sodium hydroxide), water addition, and sodium chloride (NaCl) addition on empirical and fundamental rheological properties as well as microstructural protein properties were studied and modeled by applying a response surface methodology. The obtained models revealed high correlations between the experimental factors and the complex shear modulus (R ²?=?0.97), dough resistance (R_max ^k; R ²?=?0.91) and stickiness (R ²?=?0.93). Furthermore it was possible to determine microstructural attributes as the area fraction (R ²?=?0.88) and Feret??s diameter (R ²?=?0.86) as a function of pH, water and NaCl addition. Especially measures of R^k _max revealed highly significant correlations with the protein microstructure as the branching index (r?=?0.79).     

Polyphenoloxidases immobilized in organic gels: Properties and applications in the detoxification of aromatic compounds

Gelatine gels originate from water in oil microemulsions in which the ternary system consists of isooctane/ sulfosuccinic acid bis [2-ethyl hexyl] ester/water; the solubilization of gelatin in the water pool of these microemulsions transforms them into viscous gels in which it is possible to cosolubilize various reactive molecules. These gels were used to immobilize two phenoloxidases, a laccase from Trametes versicolor and a tyrosinase from mushroom. The best balance between gel retention and catalytic activity was reached at a gelatine concentration of 2.5% (w/v) in the case of tyrosinase, while laccase immobilization was independent of gelatine concentration. Both enzymes kept the same optimum pH as the corresponding soluble controls, while a partial loss of activity was observed when they were immobilized. Immobilized enzymes showed an increased stability when incubated for several days at 4 degrees C with a very low release from the gels in the incubation solutions. The immobilization of tyrosinase and of laccase enhanced stability to thermal inactivation. Furthermore, gel-entrapped tyrosinase was almost completely preserved from proteolysis: more than 80% of the activity was maintained, while only 25% of the soluble control activity was detected after the same proteolytic treatments. A column packed with gel-immobilized tyrosinase was used to demonstrate that enzymes immobilized with this technique may be reused several times in the same reaction without loosing their efficiency. Finally, gel-entrapped tyrosinase and laccase were capable of removing naturally occurring and xeno-biotic aromatic compounds from aqueous suspensions with different degrees of efficiency. (c) 1995 John Wiley & Sons, Inc.     

A Dispersion Modeling Study of Major VOCs from Non‐Point Emission Sources in the Urban Atmosphere

To assist with the understanding and solving of toxic air pollutant problems in urban areas, an atmospheric dispersion model, SKYDM, was developed with three preprocessors (meteorology, emission, and topography), and a physical process and chemical decay term based on NO_x‐O₃‐RH photochemistry in the actual atmosphere. SKYDM can work with multicomponents in a single model run, as well as with a single compound in a model run and produces 2D meteorological field results due to an integration approach. The present study aims to develop and evaluate a SKYDM at local spatial scales, in the short term. A comparative study is conducted to estimate the effects of model parameters in defining the applicability limits of dispersion models and to examine the integration approach methodology. All simulations are run for volatile organic compounds (VOCs) such as BTXS (Benzene, Toluene, Xylene, and Styrene) emitted from non‐point sources, located at 151 villages in seven divisions, in a northeastern portion of Seoul, Korea, with eight different meteorological data sets during 2002. Modeled toluene concentrations are compared with those observed at ten monitoring sites. The main findings of the present study are as follows: (a) Model uncertainties are obviously caused by limitations of meteorological conditions and emission and topographical information, by removal processes, and by user errors or application skills – the chemical decay term was a comparatively significant parameter in the removal of toxic air pollutants, (b) the integration approach indicated a correlation between observations and the model, and (c) the SKYDM showed potential as a useful tool for assessing the air quality in urban areas. In further work, the SKYDM will be upgraded to an improving model algorithm with fully detailed input information, and evaluated in comparison with other Gaussian dispersion models.     

二维心室建模和Brugada综合症仿真

本文以Tusscher提出的人体心室单细胞计算模型为基础,用计算机建模仿真的方法,构建一个心室壁组织的二维网格模型。通过修改细胞的离子通道参数,仿真了正常生理条件下和Brugada症状下三类心室细胞的动作电位和心电图波形。结果显示:Brugada症状下的心电图波形有明显的J波出现,ST-段抬高甚至T波倒置。这与临床医学上的报道基本符合,本研究为用计算机仿真建模研究Brugada综合症打下了基础。     

破骨细胞的形成和活化研究进展

破骨细胞是骨髓系细胞经细胞因子RANKL和M-CSF共同刺激后融合而成,在维持骨代谢平衡中发挥重要作用。破骨细胞的“形成”和“活化”是破骨细胞生理活动的两个重要方面。该文综述了最近关于破骨细胞的“形成”和“活化”方面的研究进展。从转录因子、细胞因子、酸性环境、蛋白激酶和淋巴细胞等方面详述了对破骨细胞形成的调节,从整合素、溶酶体、Src蛋白、破骨相关基因、骨保护素、Ephrin／Eph和Semaphorin信号通路等方面详述了对破骨细胞活化的调节,并总结了破骨细胞凋亡方面的最新进展。最后,该文阐述了力学刺激对破骨细胞形成和活化的影响,为以破骨细胞为靶点的药物研发提供了新的思路。     

整联蛋白结构及其功能研究进展

整联蛋白是广泛存在于真核细胞表面的完整的膜受体家族,包括由至少18种不同的α亚基及8种β亚基形成的20多种αβ异二聚体。整联蛋白配体主要有胶原蛋白、纤维结合蛋白、层粘连蛋白、玻连蛋白、血小板凝血酶敏感蛋白、胞间黏附分子、细胞反受体、补体蛋白,以及多种细菌和病毒蛋白,在介导血管内皮细胞和肿瘤细胞的黏附、淋巴细胞运输、肿瘤生长及感染等都有重要的作用。     

Theoretical and Experimental Considerations Related to Reaction-Based Modeling: A Case Study Using Iron(III) Oxide Bioreduction

The kinetics of reductive dissolution of hematite ( f -Fe 2 O 3 ) by the dissimilatory iron-reducing bacterium Shewanella putrefaciens strain CN32 under nongrowth conditions with H 2 as the electron donor was measured and then modeled using a reaction-based biogeochemical model. Minimum data needs and a reaction matrix decomposition procedure are presented from a reaction-based modeling perspective and used to design subsequent experiments. Detailed step-by-step modeling methodology is presented. Independent experiments were performed to determine if Fe 2+ sorption to S. putrefaciens CN32 or hematite could be described as either kinetic or equilibrium reactions (i.e., slow or fast, respectively, relative to the time-scale of the bioreduction experiments). Fe 2+ sorption to S. putrefaciens CN32 was an equilibrium reaction and a linear adsorption isotherm was used to determine the associated equilibrium constant. Fe 2+ sorption to hematite was a kinetic reaction and an elementary rate formulation was independently determined from abiotic experiments. The ratio of the forward rate divided by the backward rate [log(k f /k b )] for the sorption of Fe 2+ to hematite was 6.33 - 0.14 (n = 2) and the corresponding log(k f ) was 6.66 - 0.28 (n = 2, M -1 h -1 ). Three different kinetic reaction rate formulations were used to model hematite bioreduction, an elementary rate law for the overall reaction, an empirical rate law physically based on hematite "free" surface sites, and an empirical rate law physically based on hematite free surface sites and bacterial inhibition caused by Fe(II) biosorption. All rate formulations modeled the measured results reasonably well (R 2 values ranged from 0.83 to 0.99). For the elementary rate formulation, log(k f /k b ) was 24.37 - 0.15 (n = 4) and the corresponding forward rate [log(k f )] was 26.46 - 0.27 (n = 4, M -4 h -1 ). These results demonstrate that independently determined reaction-based rate formulations were applicable in another experimental system, as theoretically expected. Therefore, the simulation and prediction of complex biogeochemical systems may eventually be able to be performed using reaction-based models.     

蛋白酶体结构和功能研究进展

蛋白酶体是真核细胞内依赖ATP的蛋白质水解途径的重要成分,负责大多数细胞内蛋白质的降解. 20 S蛋白酶体有多种肽酶活性,其活性位点为Thr. 19 S复合物与20 S蛋白酶体结合成为26 S复合物,能降解泛素化蛋白.近几年来,蛋白酶体的分子组成、亚基、生化机理、胞内功能等方面的研究取得了明显进展.     

Biochemical Processing of Fats and Oils As a Means of Obtaining Lipid Products with Improved Biological and Physicochemical Properties: A Review

Recent advances in the improvement of biological and physicochemical characteristics of lipids are reviewed, with emphasis on products of biochemical processing of natural (animal or plant) fats and oils. Possible uses of these new lipid products include their use in food and forage industries, as well as in the production of new medicines and in biotechnology. Specific features of biochemical transformations of lipids (hydrolysis, esterification, and reesterification) in the presence of water-soluble and immobilized lipases of animal, plant, and microbial origin are scrutinized.     

Design of Model Apple Cells Suspensions: Rheological Properties and Impact of the Continuous Phase

The objective of this work is twofold: to develop a relevant model system to study plant cells suspensions’ rheology and to evaluate the impact of the continuous phase composition and viscosity on the rheological behaviour of apple cells suspensions. Model suspensions of individual or clustered apple cells were developed. Rheological behaviours of both type of suspensions were observed separately, suspending from 0.145 g/100mL to 3.48 g/100mL of particles in five model media and in the original apple serum. Our results show that model suspensions successfully reproduce the rheological behaviour of apple purees, following three concentration domains. In particular, cell clusters greatly reproduce the behaviour of bimodal apple purees, suggesting that clusters dominate the rheological behaviour of the whole puree. One of our main result is that continuous phase does not affect elastic properties of suspensions in the concentrated domain since they are essentially governed by particle interactions: G’ values are similar whatever the continuous phase. If the continuous phase has the main impact on diluted suspensions’ viscosity, its effect becomes smaller as particle concentration increases. A lubricating effect was observed in the concentrated domain for continuous phases containing polymers. Presence of polymers may help in structuring the network in the intermediate domain.