Role of complement components on cells and in cell interactions.

The complement system, though complex, is relatively easy to study both in terms of its reaction pathways, its distribution and its genetics. There is reason to believe that the complement system is involved in cell surface events and interactions at a variety of levels and we may hope that the knowledge of the system in the blood plasma will provide relatively easy insights into the more difficult areas with cells.     

毕赤酵母蛋白表达系统研究进展

选择合适的蛋白表达系统是外源基因能否成功表达的关键.毕赤酵母(Pichia pastoris)蛋白表达系统是近些年来发展起来的一种真核表达系统,与其他表达系统相比,该系统所具有的诸多优势使其研究价值和应用价值越来越广泛,已经成功表达了多种蛋白质.简要综述其特点、表达宿主菌、表达载体以及其元件、外源蛋白的表达及其影响因素等方面的基础研究和最新进展.     

Properties of a pigment system consisting of carotenoids and reaction centre pigments in chromatophores of Rhodospirillum rubrum

A pigment system containing carotenoids and oxidised reaction centre pigments is present in chromatophores of Rhodospirillum rubrum and this pigment system may cause fluorescence quenching when a still unidentified chromatophore component is in its oxidised state. Besides by its action spectrum, this pigment system is characterised by the time course and level of light saturation of the effect. The quenching of bacteriochlorophyll fluorescence is abolished when the permeability of the chromatophore membranes is affected. The quenching effect is correlated with a reversible absorption decrease of B 880. A possible function for this pigment system is discussed.     

A recurrent system incorporating characteristics of the visual system: a model for the function of backward neural connections in the visual system

A recurrent system is constructed in order to investigate the role of the backward neural connections found in the primate visual system. The system incorporates a layer to perform localized spatial frequency analysis of input images, a function which has been assumed to take place in the primary visual cortex. The function of the system is examined by simulation. The results show that the system can separate an object pattern from its background, irrespective of its precise position. The acceptable displacement range for input images is determined from the width of the window function used to calculate the local Fourier transform. A multilayer version of the above recurrent system is also constructed.     

双组分系统——细胞识别渗透胁迫信号的感应器

双组分系统是广泛存在于原核和真核细胞中的信号转导系统.主要由组氨酸蛋白激酶(HPK)和响应调节蛋白(RR)两个组分组成. 双组分系统信号通路一般包括信号的输入、HPK自身磷酸化、RR磷酸化、信号输出等环节.对双组分系统信号转导机制及其在渗透胁迫信号识别和传导中的作用进行了综述.     

Dynamic analysis of the KlGAL regulatory system in Kluyveromyces lactis: a comparative study with Saccharomyces cerevisiae

The GAL regulatory system is highly conserved in yeast species of Saccharomyces cerevisiae and Kluyveromyces lactis. While the GAL system is a well studied system in S. cerevisiae, the dynamic behavior of the KlGAL system in K. lactis has not been characterized. Here, we have characterized the GAL system in yeast K. lactis by developing a dynamic model and comparing its performance to its not-so-distant cousin S. cerevisiae. The present analysis demonstrates the significance of the autoregulatory feedbacks due to KlGal4p, KlGal80p, KlGal1p and Lac12p on the dynamic performance of the KlGAL switch. The model predicts the experimentally observed absence of bistability in the wild type strain of K. lactis, unlike the short term memory of preculturing conditions observed in S. cerevisiae. The performance of the GAL switch is distinct for the two yeast species although they share similarities in the molecular components. The analysis suggests that the whole genome duplication of S. cerevisiae, which resulted in a dedicated inducer protein, Gal3p, may be responsible for the high sensitivity of the system to galactose concentrations. On the other hand, K. lactis uses a bifunctional protein as an inducer in addition to its galactokinase activity, which restricts its regulatory role and hence higher galactose levels in the medium are needed to trigger the GAL system. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11693-011-9082-7) contains supplementary material, which is available to authorized users.     

快速渗滤生态工程冬季运行热平衡研究及其在系统设计中的应用

本文以快速渗滤中试生态工程冬季运行实验为基础,讨论了系统在布水、融冻、渗滤及暴露过程中能量补充与损失的途径,建立了池底裸露与有冰层覆盖条件下的热平衡数学模型,扩展了快速渗滤土地处理的系统设计程序,分析了场地、工艺及运行条件对系统热量损失及净化功能的影响,为快渗系统设计与冬季安全运行提供了理论根据。     

Extending the viability theory framework of resilience to uncertain dynamics,and application to lake eutrophication

Resilience, the capacity for a system to recover from a perturbation so as to keep its properties and functions, is of growing concern to a wide range of environmental systems. The challenge is often to render this concept operational without betraying it, nor diluting its content. The focus here is on building on the viability theory framework of resilience to extend it to discrete-time stochastic dynamical systems. The viability framework describes properties of the system as a subset of its state space. This property is resilient to a perturbation if it can be recovered and kept by the system after a perturbation: its trajectory can come back and stay in the subset. This is shown to reflect a general definition of resilience. With stochastic dynamics, the stochastic viability kernel describes the robust states, in which the system has a high probability of staying in the subset for a long time. Then, probability of resilience is defined as the maximal probability that the system reaches a robust state within a time horizon. Management strategies that maximize the probability of resilience can be found through dynamic programming. It is then possible to compute a range of statistics on the time for restoring the property. The approach is illustrated on the example of lake eutrophication and shown to foster the use of different indicators that are adapted to distinct situations. Its relevance for the management of ecological systems is also discussed.     

Self-reproducing systems: structure, niche relations and evolution.

A formal definition of a self-reproducing system is proposed using Petri nets. A potential self-reproducing system is a set of places in the Petri net such that the number of tokens in each place increases due to some sequence of internal transitions (a transition is called internal to the marked subset of places if at least one of its starting places and one of its terminating places belongs to that subset). An actual self-reproducing system is a system that compensates the outflow of its components by reproduction. In a suitable environment every potential self-reproducing system becomes an actual one. Each Petri net can be considered as an ecosystem with the web of ecological niches bound together with trophic and other relations. The stationary dynamics of the ecosystem is characterized by the set of filled niches. The process of evolution is described in terms of niche composition change. Perspectives of the theory of self-reproducing systems in biology are discussed.     

The Evolution of the Linnaean Hierarchy

The Linnaean system of classification is a threefold system of theoretical assumptions, sorting rules, and rules of nomenclature. Over time, that system has lost its theoretical assumptions as well as its sorting rules. Cladistic revisions have left it less and less Linnaean. And what remains of the system is flawed on pragmatic grounds. Taking all of this into account, it is time to consider alternative systems of classification.     

Molecular mechanisms of the shrimp clotting system

Shrimp, like other invertebrates, relies solely on its innate immune system, to combat invading pathogens. The invertebrate immune system has ancient origins that involve cellular and humoral responses. The clotting system of the humoral immune response is the first line of defense against pathogens and also serves to prevent blood loss during injury and wound healing. Tranglutaminase and clotting protein are molecules involved in the blood clotting system of crayfish and shrimp. Studies have shown that the shrimp clotting system is linked with the activation of antimicrobial peptides, similar to that of the horseshoe crab. Unlike the horseshoe crab and crayfish blood coagulation which are well studied systems, blood clotting in shrimp remains poorly understood. Here we review the shrimp clotting system and its involvement in innate immunity.     

香港特区公营医院运行机制评估及对内地的启示

回顾香港医疗融资的发展历程并简述香港公营医院的运营状况与开支构成比,重点分析香港公营医院的管理机构——香港医院管理局,研究其宗旨任务与目标策略相结合的管理医院管理战略,跟踪其主要经费来源的变化趋势,对其财务状况进行深入探究并进行预测。在对香港公营医院运行机制进行评估的基础上,探讨香港公营医院存在的问题以及对内地的启示,为内地医院管理机构借鉴香港逐步建立以政府投入为主体的医疗融资体系提供参考。     

The ubiquitin-proteasome system--micro target for macro intervention?

The ubiquitin-proteasome system is the two sequential labeling and degradation system that accounts for the degradation of 80-90% of all intracellular proteins. Based on the diversity of its substrates, it is integrated in many different biological processes, especially inflammation and cell proliferation. Given the significance of these two processes for primary atherosclerosis and restenosis, the ubiquitin-proteasome system may be an amendable target in cardiovascular therapy. This review provides background information on the ubiquitin-proteasome system, currently available data on its involvement in cardiovascular diseases, and a future perspective on the targeted use proteasome inhibitors, including drug-eluting stents.     

Specificity of transinhibition of amino acid transport in neurospora

Amino acid transport systems I and III in Neurospora are inhibited by amino acids in the intracellular pool (transinhibition). The transinhibition is system specific. The ability of an amino acid to transinhibit a transport system is highly correlated with its affinity for the system. The significance of the system specificity of transinhibition is discussed.     

Information Content,Complexity, and Uncertainty in Material Flow Analysis

Material Flow Analysis (MFA) is a useful method for modeling, understanding, and optimizing sociometabolic systems. Among others, MFAs can be distinguished by two general system properties: First, they differ in their complexity, which depends on system structure and size. Second, they differ in their inherent uncertainty, which arises from limited data quality. In this article, uncertainty and complexity in MFA are approached from a systems perspective and expressed as formally linked phenomena. MFAs are, in a graph‐theoretical sense, understood as networks. The uncertainty and complexity of these networks are computed by use of information measures from the field of theoretical ecology. The size of a system is formalized as a function of its number of flows. It defines the potential information content of an MFA system and holds as a reference against which complexity and uncertainty are gauged. Integrating data quality measures, the uncertainty of an MFA before and after balancing is determined. The actual information content of an MFA is measured by relating its uncertainty to its potential information content. The complexity of a system is expressed based on the configuration of each individual flow in relation to its neighboring flows. The proposed metrics enable different material flow systems to be compared to one another and the role of individual flows within a system to be assessed. They provide information useful for the design of MFAs and for the communication of MFA results. For exemplification, the regional MFAs of aluminum and plastics in Austria are analyzed in this article.     

The periplasmic modifier protein for methanol dehydrogenase in the methylotrophs Methylophilus methylotrophus and Paracoccus denitrificans.

A modifier protein (M-protein), which increases the affinity of methanol dehydrogenase (MDH) for alcohols but decreases its affinity for formaldehyde, has been partially purified from Methylophilus methylotrophus and Paracoccus denitrificans. Analysis was complicated by non-protein factors in bacterial extracts that are able to mimic M-protein in one of its functions-that of increasing the activity of MDH with butane-1,3-diol in the dye-linked assay system. The 67 kDa polypeptide, previously identified as a subunit of the M-protein, is an unrelated cytoplasmic protein. The M-protein is exclusively periplasmic and is a multimeric protein with subunits of 45 kDa. The M-protein is active in the 'physiological' assay system with the specific cytochrome c electron acceptor for MDH, lowering its affinity for formaldehyde. It has its maximum effect when the ratio of M-protein:MDH is 1:5 but its concentration in the periplasm is much lower than 20% of that of MDH.     

Modulation of urokinase plasminogen activator system by poly(ADP-ribose)polymerase-1 inhibition

The urokinase plasminogen activator (uPA) system is a complex regulator of extracellular proteolysis which is involved in various physiological and pathological processes. The major components of this system are the serine protease uPA, two inhibitors PAI-1 and PAI-2, and the receptor uPAR. It has been previously shown by several groups that the uPA system has an important role in cancer progression and therefore its possible prognostic and therapeutic value has been evaluated. The aim of this study is to tackle the role of poly(ADP-ribosyl)ation in the induction of uPA activity in a glioblastoma cell line, A1235. This cell line is sensitive to alkylation damage and is a model for drug treatment. The components of the uPA system and the level of DNA damage were analyzed after alkylation agent treatment in combination with poly(ADP-ribose)polymerase-1 (PARP-1) inhibition. Here we show that the increase in uPA activity results from the net balance change between uPA and its inhibitor at mRNA level. Further, PARP-1 inhibition exerts its influence on uPA activity through DNA damage increase. Involvement of several signaling pathways, as well as cell specific regulation influencing the uPA system are discussed.     

Possibility of analytical application of the partition in aqueous biphasic polymeric systems technique

The partition behaviour of a number of ionic and nonionic surface-active substances in the dextran-polyethylene glycol system was examined. The strictly linear dependence of the logarithm of the partition coefficient on the alkyl chain length for a homologous series of nonionic surfactants provides a measure of the difference in the relative hydrophobicity between the two phases of the system, in terms of the free energy of transfer of a CH₂ group from the bottom phase to the top phase of the system. This difference is found to be altered in the presence of NaCl or KCl depending on the salt concentration. It is concluded that the influence of the salt composition of the system on the distributed solutes' behaviour may be due to the effect of the ions on the hydrophobicity difference between the phases.The partition of ionic amphiphiles is found to be dependent on the relative hydrophobicity of the compounds as well as on their charge. It is shown that at salt concentrations up to about 0.1 M NaCl the charged solute partition is determined by its charge as well as its relative hydrophobicity, in the presence of 0.1–0.2 M NaCl the substance distribution is highly dependent on its charge and slightly on its lipophility. At the salt concentrations above 0.2 M the solute partition is determined just by its hydrophobic character and seems to be totally independent of its charge. It is concluded that the partition technique can be used for analytical purposes. The method seems to be unique in providing quantitative information on the amphiphilic surface properties of the solutes being partitioned.     

Pressure measurements during automatic breast compression in mammography

Breast compression during X-ray mammography results in improved image quality at a lower radiation dose to the patient, and, as a consequence, the Department of Health recommends that automatic breast compression devices are fitted to mammographic X-ray units. However, the degree of breast compression is not standardized and can vary depending on the size of the patient, the particular mammography X-ray unit and the conditions of its use. A pressure measuring system was used to determine accurately the pressure on the breast. This system takes the form of a fluid-filled neonatal cuff connected to a pressure transducer by a fluid line. The pressure measuring system was calibrated and tested, first without and then with the patients, to assess its pratical feasibility. The elements of the pressure measuring system, the techniques involved in its calibration and its use on patients in the clinical environment are described here. The system has proved to be a quick and simple method of relating the pressure on the breast to the pressure reading of the mammography X-ray unit.