酪氨酸酶的应用研究进展

酪氨酸酶具有重要的生理生化特性,在医药、环境、食品、精细化工等领域具有广泛的用 途。酪氨酸酶可以氧化L-酪氨酸合成L-多巴和黑色素,L-多巴用于帕金森症的治疗,黑色素能够 杀死HIV病毒。酪氨酸酶可用于环境工程领域处理含苯酚及胺类废水,用于精细化工领域催化 有机合成反应。综述了酪氨酸酶在各个领域的应用概况,阐明了其在工业生产领域的应用前景。     

植物外来种入侵及其对生态系统的影响

对植物外来种的入侵及生态系统的影响进行综述与分析，植物入侵多种因子的影响，可分为外因和内因两类，植物外来种对生态系统的影响主要体现在生产力，土壤营养，水分，干扰体制，群落的结构和动态等方面，在管理外来种时，需对外来种的特性和影响因子进行系统的观察研究，采用机械法，化学方法和生物控制法等综合办法控制植物的入侵，引进植物引来种时，要对引进种的行为特性进行了调查研究，注意其安全性。     

Modern problems of biodosimetry

Humans have different radiosensitivity. Besides, many factors which are not under control can change significantly biological effects of radiation. Some of substances are present in our food--residual amounts of fertilizers or herbicides can be mutagenic or influence mutagenic action of radiation. In the last case synergetic or antagonistic effects can be observed. At the same time many food products contain radioprotectors or antimutagens. Some drugs, stress, virus diseases and so on can change biological effects of radiation too. Radioadaptive response is one of the most significant factors which can be responsible for incorrect radiation dose evaluation. All these uncontrolled factors may be responsible for significant mistakes of evaluating radiation dose by biological methods. That is why biological methods can be used for bioindication but not for biodosimetry.     

Interactions of liposomes with serum proteins

The interactions of serum proteins are diverse, complex and can lead to dramatic effects on liposome stability and in vivo behavior; conversely lipids can modify the biological activities of serum proteins. Serum lipoproteins can potentially destabilize bilayer membranes leading to vesicle disruption and loss of contents; irregularities in the lipid bilayer, such as those which exist at phase boundaries, promote the destabilizing effects of lipoproteins. Other serum components such as fibronectin, immunoglobulins and C reactive protein can modify the biological properties of liposomes by promoting interactions with reticuloendothelial cells and/or activation of the complement system. Liposomes can avidly bind certain serum clotting factors, a process which can lead to dramatic effects on the clotting cascade. Thus the interactions of liposomes with serum proteins can reciprocally effect both components involved.     

Derivation of the angle of torsion of the eye.

The angle of torsion of the eye, that is the amount by which the eye rotates about its anterio-posterior axis, changes with the direction of the line of fixation. If the eye can be considered as a rigid body under an elaborate system for constraints its motion can be described by the laws of kinematics. The techniques of linear algebra can then be used to derive an explicit relationship between the angles defining the direction of fixation and the angle of torsion of the eye. The angle of torsion can then be expressed as a function of the angle of rotation of the eye and the direction cosines of the axis of rotation. However, under conditions in which Listing's Law holds these angles, are well defined functions of the angles defining the direction of fixation, and so the angle of torsion, in this case, can be expressed as an explicit function of this direction.     

The use of controlled-release glass for the controlled delivery of bioactive materials

CRG can provide a useful supplement to other methods of controlled delivery. Some advantages of this approach are: The constituents of the CRG can be limited to biologically safe ionic species such as Na+, Ca2+ and PO4(3-). The release system is completely soluble in water and no residue remains. There is no evidence of any mechanism for biodegradation of the CRG and so one possible cause of premature or accelerated release is eliminated. The absolute release rate can be selected anywhere in a spectrum covering several orders of magnitude and the rate-controlling process has zero-order kinetics. The release rate can be selected to be pH-sensitive or pH-independent. Complex temporal release-rate patterns can be obtained readily by the choice of geometrical shape or composition profile of the device. The controlled release of organics or other heat-sensitive materials which cannot be incorporated in the glass can be realized by the use of composite structures in which the CRG is the rate-controlling constituent. A number of different functions can be performed by a single CRG-based device. For example, CRG can be used as a biomedical resorbable material in surgery and the CRG structural component can release an AM as it dissolves. Similarly the CRG of the sinter-composite used for organic AM release can itself release any selected inorganic adjuvant. CRG boluses containing either copper or cobalt and weighing approx. either 70 g or 15 g, have been administered to both cattle and sheep. More than 90% of the boluses remained either in the reticulum of trace element remained after dosing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of the specific radloactivity of proteins separated by two-dimensional gel electrophoresis

Tritlum-labeled proteins, separated by two-dimensional gel electrophoresis, can be quantitatively extracted using sodium dodecyl sulfate (SDS)-urea buffer and subsequently acid-precipitated in the presence of serum albumin as carrier at low temperature (0–4°C). Their radioactivity can be counted efficiently under these conditions. Besides a better efficiency of counting, this method has some other advantages over the classical procedures using H₂O₂. The amounts of the eluted proteins can be easily measured in the SDS solution, using the Lowry method, and therefore specific radioactivity can be calculated. Also SDS can be removed easily, and the proteins can be used for further experiments.     

HarpinPss elicited early defense responses of tobacco cells and involvement of calcium]

HarpinPss can induce hypersensitive reaction (HR) in tobacco leaves. As superoxide dismutase can inhibit but catalase can not inhibit the development of HR induced by harpinPss, superoxide anion is required for this response. HarpinPss can also induce the release of active oxygen and extracellular alkalinization, two early defence responses in tobacco suspension culture. Diphenylene iodoium, can completely inhibit the induction of HR in tobacco leaves, and the release of active oxygen in the suspension culture system, superoxide anion in these system may be produced by the activation of NADPH oxidase. Ethyleneglycol-bis (beta-aminoethyl) N, N, N'N'-tetraacetic acid (EGTA) can inhibit the development of harpinPss-induced HR and these two early defence responses in suspension culture system. Adding Ca2+ into the medium again, these responses can return to normal level in a short time. Lanthanum chloride, verapamil, neomycin, U-73122, and LiCl can also inhibit these harpinPss-induced responses. Therefore, the influx of Ca2+ mediated by calcium channel and the release of Ca2+ from internal Ca2+ pool may be involved in the two early defense responses induced by harpinPss. Cycloheximide and actinomycin D have no effect on the release of active oxygen but can inhibit harpinPss-induced HR even added them in the intermediate process for inducing HR. It indicates superoxide is just a trigger for HR, and HR is a more complex process that needs the sustained expression of some genes.     

The logical repertoire of ligand-binding proteins

Proteins whose conformation can be altered by the equilibrium binding of a regulatory ligand are one of the main building blocks of signal-processing networks in cells. Typically, such proteins switch between an 'inactive' and an 'active' state, as the concentration of the regulator varies. We investigate the properties of proteins that can bind two different ligands and show that these proteins can individually act as logical elements: their 'output', quantified by their average level of activity, depends on the two 'inputs', the concentrations of both regulators. In the case where the two ligands can bind simultaneously, we show that all of the elementary logical functions can be implemented by appropriate tuning of the ligand-binding energies. If the ligands bind exclusively, the logical repertoire is more limited. When such proteins cluster together, cooperative interactions can greatly enhance the sharpness of the response. Protein clusters can therefore act as digital logical elements whose activity can be abruptly switched from fully inactive to fully active, as the concentrations of the regulators pass threshold values. We discuss a particular instance in which this type of protein logic appears to be used in signal transduction-the chemotaxis receptors of E. coli.     

环境雌激素生态影响的研究进展

环境雌激素(ｅｃｏｅｓｔｒｏｇｅｎ) ,是指能够扰乱动物内分泌活动 ,生理活性与雌激素较为相似的动物体外化学物质 ,包括人工合成化合物以及植物天然雌激素 ,由于目前所发现的干扰动物及人体内分泌系统的有机化合物绝大多数都具有激素特征 ,因此通常又将环境激素称做“干扰内分泌化合物”(ｅｎｄｏｃｒｉｎｅｄｉｓｒｕｐｔｉｎｇｃｈｅｍｉ ｃａｌｓ或ｅｎｄｏｃｒｉｎｅｄｉｓｒｕｐｔｅｒｓ)。环境激素问题只是在最近几年才引起世界关注 ,但由于环境激素污染范围广、影响大 ,对人类生存的威胁更直接 ,目前 ,西方国家将环境激素问题与臭…     

Pharmacokinetics of monoclonal antibodies and Fc-fusion proteins

There are many factors that can influence the pharmacokinetics (PK) of a mAb or Fc-fusion molecule with the primary determinant being FcRn-mediated recycling. Through Fab or Fc engineering, IgG-FcRn interaction can be used to generate a variety of therapeutic antibodies with significantly enhanced half-life or ability to remove unwanted antigen from circulation. Glycosylation of a mAb or Fc-fusion protein can have a significant impact on the PK of these molecules. mAb charge can be important and variants with pI values of 1–2 unit difference are likely to impact PK with lower pI values being favorable for a longer half-life. Most mAbs display target mediated drug disposition (TMDD), which can have significant consequences on the study designs of preclinical and clinical studies. The PK of mAb can also be influenced by anti-drug antibody (ADA) response and off-target binding, which require careful consideration during the discovery stage. mAbs are primarily absorbed through the lymphatics via convection and can be conveniently administered by the subcutaneous (sc) route in large doses/volumes with co-formulation of hyaluronidase. The human PK of a mAb can be reasonably estimated using cynomolgus monkey data and allometric scaling methods.     

Study of models of single populations: development of equations used in microorganism cultures

This article derives a number of equations which can be used in both continuous and the semicontinuous cultures of microorganism populations in chemostat systems. Using these equations, some phenomena which have been known for many years can be explained reasonably in terms of chemical kinetics, and a number of analytical solutions can be obtained instead of numerical solutions previously published.     

种群内部因素对动物免疫功能的影响

动物的免疫状况与种群动态的关系是近年来动物生态学研究的热点之一。总结了种群内部因素对动物免疫功能的影响,并介绍了几种免疫调节假说,对于不同的研究对象,种群密度的高低对其可产生不同的影响。在一个种群中,优势个体往往具有较高的免疫水平;雌性个体的免疫水平高于雄性个体,这可部分归因于性激素的作用,动物处于繁殖期时免疫水平有所下降。婚配制度的作用效果是复杂的,为了能够成功进行繁殖而面临更大选择压力的性别可能具有更强的免疫水平有所下降,婚配制度的作用效果是复杂的,为了能够成功进行繁殖而面临更大选择压力的性别可能具有更强的免疫功能,许多研究者根据野外研究结果探讨了种群调节的免疫机制问题,认为个体的免疫能力受到遗传和环境因素的影响,其变化状况将关系到整个种群的数量波动,还介绍了生态学研究中采用的免疫学指标。评价了这些指标对实验结果的影响,并对今后的研究方向提出了几点建议。     

Marine yeasts as biocontrol agents and producers of bio-products

As some species of marine yeasts can colonize intestine of marine animals, they can be used as probiotics. It has been reported that β-glucans from marine yeast cells can be utilized as immuno-stimulants in marine animals. Some siderophores or killer toxins produced by marine yeasts have ability to inhibit growth of pathogenic bacteria or kill pathogenic yeasts in marine animals. The virulent factors from marine pathogens can be genetically displayed on marine yeast cells, and the yeast cells displaying the virulent factors can stimulate marine animals to produce specific antibody against the pathogens. Some marine yeast cells are rich in proteins and essential amino acids and can be used in nutrition for marine animals. The marine yeast cells rich in lipid can be used for biodiesel production. Recently, it has been reported that some strains of Yarrowia lipolytica isolated from marine environments can produce nanoparticles. Because many marine yeasts can remove organic pollutants and heavy metals, they can be applied to remediation of marine environments. It has been shown that the enzymes produced by some marine yeasts have many unique properties and many potential applications.     

Diagnosis of Dermatophytosis

Dermatophytoses are infections of the skin, hair or nails caused by dermatophytes. Dermatophytes can induce typical diagnostic clinical lesions (tinea), but can also mimic other dermatoses. Therefore, physicians need to be familiar with the whole spectrum of tinea and must constantly be mindful of possible dermatophytosis. An examination with Wood’s light can be helpful. In superficial lesions, the demonstration of dermatophytes may be achieved by dermatoscopy or laser scanning. An essential step of the following diagnostic procedure is the skilful collection of samples for the proof of fungi. Microscopy of KOH mounts or equivalent preparations produced from infected material and histology are approved methods. The necessary identification of dermatophytes on species level can finally be accomplished by conventional methods based on cultures or by new techniques based on molecular differentiation or MALDI-TOF analysis. These modern methods are clearly on the increase and can considerably improve and accelerate dermatophyte identification.     

植物寄生对生态系统结构和功能的影响

寄生植物是生态系统中的特殊类群之一。植物寄生可以驱动生态系统中生物与非生物因子的变化,在生态系统结构与功能中起关键作用。寄生植物可以通过对寄主营养的集聚、改变凋落物的质量与数量、改变根的周转与分泌物格局、改变土壤水势,从而影响土壤理化特性。寄生植物会改变寄主的行为,改变寄主与非寄主植物之间的相互作用,从而影响植物群落的结构、多样性和动态,进而影响植被演替和植被生产力等。寄生植物与寄主均可被消费者取食,可直接或间接地影响生态系统的食草动物,包括草食昆虫等。寄生植物与寄主的其它寄生物存在竞争关系,可以直接或间接地影响寄主的其它寄生植物或病原真菌。寄生植物可以明显地改变土壤地球化学循环,将固有的不可动的成分转变为可利用的营养成分,改变土壤生物群落的结构与功能,从而显著影响地下生物群落。这些表明,植物寄生对生态系统的结构和功能有重要影响。针对特殊的被入侵的植物群落,该地寄生植物可以通过影响入侵植物寄主的生长、繁殖、生物量分配格局,改变土壤的理化特性,促进非寄主的非优势本地植物的生长,从而改变被入侵植物群落结构与多样性,达到生物防治及生态恢复的目的。     

The ecological and evolutionary significance of frost in the context of climate change

The effects that below-freezing temperature (frost) can have at times of year when it is unusual are an interesting ecological phenomenon that has received little attention. The physiological consequence of formation of ice crystals in plant tissue is often death of the plants, or at least of sensitive parts that can include flower buds, ovaries, and leaves. The loss of potential for sexual reproduction can have long-lasting effects on the demography of annuals and long-lived perennials, because the short-term negative effects of frosts can result in longer-term benefits through lowered populations of seed predators. The loss of host plants can have dramatic consequences for herbivores, even causing local extinctions, and the loss of just flowers can also affect populations of seed predators and their parasitoids. Frosts can cause local extinctions and influence the geographical distribution of some species. The potential for global climate change to influence the frequency and distribution of frost events is uncertain, but it seems likely that they may become more frequent in some areas and less frequent in others.     

Characterization of a Drosophila melanogaster orthologue of muskelin

Visual systems of vertebrates exhibit a striking level of diversity, reflecting their adaptive responses to various color environments. The photosensitive molecules, visual pigments, can be synthesized in vitro and their absorption spectra can be determined. Comparing the amino acid sequences and absorption spectra of various visual pigments, we can identify amino acid changes that have modified the absorption spectra of visual pigments. These hypotheses can then be tested using the in vitro assay. This approach has been a powerful tool in elucidating not only the molecular bases of color vision, but the processes of adaptive evolution at the molecular level.     

Synchronization of delayed coupled neurons in presence of inhomogeneity

In principle, two directly coupled limit cycle oscillators can overcome mismatch in intrinsic rates and match their frequencies, but zero phase lag synchronization is just achievable in the limit of zero mismatch, i.e., with identical oscillators. Delay in communication, on the other hand, can exert phase shift in the activity of the coupled oscillators. In this study, we address the question of how phase locked, and in particular zero phase lag synchronization, can be achieved for a heterogeneous system of two delayed coupled neurons. We have analytically studied the possibility of inphase synchronization and near inphase synchronization when the neurons are not identical or the connections are not exactly symmetric. We have shown that while any single source of inhomogeneity can violate isochronous synchrony, multiple sources of inhomogeneity can compensate for each other and maintain synchrony. Numeric studies on biologically plausible models also support the analytic results.