基于质谱成像和组学分析的环境毒理研究

生物体多器官的空间异质性导致环境污染物在生物体内的毒性分子机制错综复杂.基于传统化学和生物分析的环境毒理学研究,通常将研究对象看作“均一”整体,无法从空间上准确定位污染物及其代谢.以质谱成像和组学分析为基础的技术,同时对污染物、污染物代谢活化途径及其诱导的生物分子进行定性、定量和空间分析,从而确定污染物迁移、生物学效应...     

多溴二苯醚的生物代谢机制研究进展

作为一种广泛使用的阻燃剂,多溴二苯醚(PBDEs)及其衍生物羟基化多溴二苯醚(OH-PBDEs)和甲氧基化多溴二苯醚(MeO-PBDEs)等已从环境介质、各种生物体甚至人体内检测出来.但是对于生物体内低溴代PBDEs及其羟基化和甲氧基化衍生物的来源及其是否由PBDEs在生物体内代谢形成等问题,目前仍存在较多争论.由于PBDEs进入生物体后的生物转化、代谢途径与其对生物体的毒性有密切关系,因此是研究者们关注的焦点.本文在对生物体内PBDEs及其代谢物的来源和分布进行分析的基础上,综述了PBDEs在生物体内发生脱溴还原代谢和氧化代谢的研究进展,从体内原位代谢和体外模拟代谢研究两方面探讨了PBDEs的生物代谢机制、代谢途径及还原和氧化代谢中可能涉及的代谢酶,指出进一步深入开展PBDEs的生物积累和代谢研究的方向.     

持久性有机污染物的分析检测研究进展

持久性有机污染物(POPs)可以通过各种环境介质(大气、水、生物体等)长距离迁移并长期存在于环境中,具有生物富集性、毒性、致畸、致癌性,对人类健康和环境具有严重的危害.用于此类物质的分析方法很多,主要可分为仪器联用分析方法和快速分析方法,如:色谱-质谱分析、光谱分析、生物分析、光/电分析、传感分析等.这些方法各有优缺点,互为补充.本文将按照分析方法,重点介绍2000年至今在POPs分析技术上的最新进展.     

蛋壳中的化学

在了解蛋壳的形成机理和理化性质之前,很有必要谈谈什么是生物矿化.所谓的生物矿化,是指在生物体内生成矿物的过程,即在生物体的特定部位,在一定的物理、化学条件下和有机基质的诱导下,生物体将无机物与有机基质通过自组装形成具有生物功能的特殊材料的过程,是一个高度受控的生命过程,也是动物体内一种特有的生理过程,如骨骼的发育、牙齿的生长等.     

蛋中全氟/多氟化合物的分析方法及其作为污染指示物的应用

全氟和多氟化合物(perfluoroalkyl and poly-fluoroalkylated substances, PFASs)在环境中有极强的持久性和生物富集能力,在全球生态系统及人体中已被普遍检出,其潜在的毒性引起了人们高度关注。蛋是卵生动物生命的起源,同时其营养丰富,是人类主要的蛋白质来源之一,因此,蛋中的污染物水平一方面有可能影响卵生动物种族繁衍,另一方面也关系到人类的健康风险。近年来禽蛋类样品作为非损伤性生物基质已广泛应用于生物体和生态系统污染情况的评估,同时利用蛋类样品中污染物水平评估相应的遗传发育毒性风险和摄入健康风险的研究也逐渐增多。该文对现有文献中蛋中PFASs的样品前处理和仪器检测方法进行了归纳总结,并且对蛋作为PFASs污染指示物的适用性和先进性进行了讨论。     

浅谈生物体内自发反应的推动力

生物体以自由能的形式从外界获取能量用于驱动生命过程,整体上遵循热力学规律。化学反应自由能变化的可加和性及生物体内化学反应的偶联性,使得生物体内在热力学上不利的反应可以由有利的反应所推动。高能生物分子,如三磷酸腺苷(ATP),是生命活动的直接能源。正是这些高能生物分子推动着生物体内化学反应的进行,把外界的能量转化为生物体自身的能量,以维持生物体内各种组织的有序性。     

环境内分泌干扰物毒理学研究

传统上,环境内分泌干扰物的研究对象主要是对动物生殖器官的作用.但是脊椎动物体内存在复杂的内分泌系统,来调节其生长发育及繁殖.本文从环境内分泌干扰物对生物完整内分泌系统的影响总结了最近的研究进展.内分泌干扰物可通过作用于下丘脑.脑垂体.性腺轴的内分泌系统途径,影响重要激素或者受体,并最终影响动物的繁殖;也可作用于下丘脑一脑垂体.甲状腺轴途径,影响甲状腺激素的合成、转运、结合等过程,破坏甲状腺激素内环境的稳定而对生长发育造成危害.环境污染物也可通过影响类固醇激素的合成途径,即通过非受体途径而发挥内分泌干扰物作用.水体缺氧也可干扰鱼类的内分泌系统,因此也是内分泌干扰物.分子生物学技术,如组学、转基因技术等不仅可为环境污染物的内分泌干扰作用的危险评价提供可靠的手段而且也可揭示污染物作用的模式.     

PBDEs研究的最新进展

多澳联苯醚(PBDEs)是一类环境中广泛存在的全球性有机污染物.由于其具有环境持久性、远距离传输、生物可累积性及对生物和人体具有毒害效应等特性,对其环境问题的研究已成为当前环境科学的一大热点.本文对最近几年来环境中PBDEs研究的进展进行综述,对多溴联苯醚在环境及生物体中的分布、时间趋势、人体暴露及途径、环境中的降解和生物代谢以及生物累积与生物放大方面的研究进行了总结,对目前存在问题及进一步的研究方向进行了讨论和展望.     

基于超分子化学的核酸表观遗传修饰研究

核酸是生物体的遗传物质,在生命体系中发挥着重要作用.除了构成核酸的经典碱基之外,核酸中还存在天然修饰的碱基,这被称为核酸的表观遗传修饰.核酸的表观遗传修饰在基因表达过程中具有重要的调控作用,对生物体遗传和生命生长过程影响很大,并且核酸表观遗传与疾病密切相关.超分子化学是研究分子间键的化学,而许多生物分子都需要通过超分子化学作用来发挥其生物功能,可以说生物体内天然存在着大量的超分子化学过程.本文综合评述了基于超分子化学的核酸表观遗传修饰研究的一些代表性工作.     

碳纳米材料与共存污染物的联合毒性

碳纳米材料(carbon nanomaterials,CNMs)具有广泛的应用,其产量飞速增长,并在纳米产品的消费过程中不可避免地被释放到环境中.环境中的CNMs能够与共存污染物(如有机污染物、重金属和其他纳米颗粒)相互作用,影响彼此的归趋及毒性效应.因此在评价CNMs的环境风险时,CNMs与环境中共存污染物的联合毒性不容忽视.本文首先归纳了CNMs对生物体的直接及间接致毒机制,随后着重探讨了CNMs与有机污染物、重金属等环境污染物的联合毒性,从CNMs与其他污染物的作用方式入手,探究了联合毒性与单一毒性发生差异(增强或抑制)的机制,最后对目前CNMs与共存污染物联合毒性的评价方法、研究水平以及面临的挑战进行了分析和展望,为准确评估并深入理解CNMs的环境风险提供一定的理论基础.     

The Accuracy in Microweighing in Vacuum and Controlled Environments

Accurate weighing depends on both physical factors and the weighing technique. There are two categories of physical factors: the location and support of the balance, and physical phenomena. Important such phenomena include processes of heat transfer by convection and radiation in rarefriction gases, Archimedes buoyancy, electrostatic, magnetostatic and gravitational effects, etc. Surveys of disturbances which affect the accuracy of weighing in vacuum or in controlled environments have been published elsewhere. This paper describes a high-vacuum apparatus connected to a Cahn RG ultramicrobalance. The system was adapted for investigations of long-time kinetic runs of oxygen loss in oxide superconductors in dynamic vacuum, and of other gas - solid interactions. Typical calibration curves for 'not fully compensated system' are presented in controlled environments at cryogenic temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

The evolution of steep fronts in non-fickian polymer-penetrant systems

We adapt a recently proposed model for non-Fickian diffusion of penetrants into polymers and use it to study a drug-delivery problem. The model modified Fick's diffusion equation by the addition of stress-induced flux. A stress evolution equation incorporating aspects of the Maxwell and Kelvin-Voigt viscoelastic stress models completes the model. The relaxation time in the polymer is taken as a function of the penetrant concentration. The system is studied under the assumption that the diffusivity is large. Singular perturbation techniques are used to show that the concentration and stress evolve diffusively for small time, but exhibit steep fronts in a narrow region within the domain for larger time. These predictions are verified numerically for specified parameter values. Finally, the equations are studied in the steady state and are found to predict the evolution of shocks.     

Theoretical aspects of communication in chemistry

Successful searching for publications on the basis of subject obeys rules whose relations to thermodynamics are unmistakable. As a collection of literature grows, the degree of order required increases, since the patience, time, and memory used by man to compensate for lack of order cannot keep pace. The high degrees of order that are necessary nowadays in scientific literature cannot be attained by traditional documentation methods. If modern techniques are used to improve communication, the conceptual basis of such a documentation method must be revised and adapted to suit the new possibilities. The conditions in chemistry are relatively favorable for the effective use of modern technical and conceptual methods, since the terminology has been developed further than in most other sciences.     

Present-day communication in chemistry--problems and possibilities

This article deals with the problems and possibilities in the present-day communication of chemical results and opinions. Personal communications as well as primary and secondary literature have to be supplemented in the future by documentation and information services which use modern electronic data processing equipment.     

Applicability of reversed-phase liquid chromatography for the speciation of vanadyl and nickel metalloporphyrins in oil extracts

Summary Gradient reversed-phase liquid chromatography was examined with a view to using it as a separation technique for the speciation of vanadyl and nickel porphyrins in oil extracts. Poor separations were obtained when precipitation of the sample constituents occurred in the starting mobile phase. The reasons for the precipitation phenomena were found to be highly complex. Mixed crystal formation, slow dissolution kinetics and saturation may influence the elution behaviour of species present in the oil extracts. When precipitation was avoided the separation of the vanadyl porphyrins was significantly improved. Thus far, no satisfactory separations have been obtained for the nickel porphyrinic species.Although the occurrence of precipitation of the extracts hinders the distinct speciation of metalloporphyrins with reversed phase chromatography, the precipitation/dissolution phenomena showed some interesting features as a clean-up step for diluted crude oil samples and oil fractions.     

Transport of acetylcholine in a membrane

A laminate model of the cleft-plus-postsynaptic membrane structure of the neuromuscular junction was studied. In order to prepare a model of the postsynaptic membrane, the properties of acetylcholine (Ach) receptor-rich vesicles purified from Torpedo fish were measured. Immobilization of vesicles was demonstrated by various methods, in particular, by investigating collagen and carrageenan matrices as models of the fluidfilled fibrous matrix of the cleft. It was found that a laminated system employing a liquid membrane-containing vesicle suspension, together with a swollen collagen membrane, is an appropriate model for examining important transport/reception aspects of the cleft-plus-postsynaptic membrane structure. Combined transport with immobilization of Ach in the liquid membrane system was elucidated and effective diffusivities in the vesicle suspension layer were calculated. Effective diffusivities of the composite system simulating the cleft and the postsynaptic membrane were evaluated as well. These data illustrate the importance of penetrant immobilization in retarding the diffusion process during neurotransmission.     

Methanol-induced opacity in poly (methyl methacrylate)

Methanol-induced opacity in poly (methyl methacrylate) (PMMA) is investigated subject to two cooling processes; furnace cooling and air cooling. The glass transition temperature of PMMA decreases with increasing time of exposure to methanol at 40–60°C and then increases during cooling, due to progressive desorption. Voids form during cooling as long as specimen temperature remains above its glass transition temperature. Since furnace cooling affords enough time for holes to expand larger than the light wavelengths, the transmittance of furnace-cooled PMMA is independent of wavelength. The transmittance of PMMA subjected to rapid cooling in the air is wavelength dependent due to scattering by holes smaller than light wavelengths. The transmittance of PMMA bearing a given weight gain of methanol (measured at absorption temperature) prior to cooling for furance cooling is lower than that for the same material subjected to air cooling. A sharp front between outer and inner regions is found in specimens removed quickly from the thermostated water bath to air at ambient temperature.     

Temperature effects in capillary electrophoresis 2: Some theoretical calculations and predictions

Summary The dependence of the temperature excess, , in the capillary bore on the applied power, EI, is considered for both natural and forced convective cooling, using classical heat equations. The dependence of on EI is found to be linear for forced convection but not for natural convection. Use of forced convective cooling and capillaries of large outer diameter reduces . Direct comparison of the performance of different systems can be achieved by consideration of . Column performance is ultimately limited by thermal gradients across the capillary bore.     

Intestinal metabolism of Polygonum cuspidatum in vitro and in vivo

Rhizoma et Radix Polygoni Cuspidati (RRPC) is commonly prescribed for the treatment of amenorrhea, arthralgia, jaundice and abscess in traditional Chinese medicine. Previous pharmacological studies have indicated that polyphenols are the main pharmacological active ingredients in RRPC. Meanwhile, the poor bioavailability of polyphenols in RRPC implies that those components are probably metabolized by intestinal bacteria before absorption. However, there is rather limited information about RRPC''s metabolites produced by intestinal bacteria and the intestinal absorbed constituents. In the present study, the metabolites were characterized after the aqueous extract of RRPC was incubated with the crude enzyme of human intestinal bacteria in vitro. The metabolic characteristics of glycosides in RRPC were figured out by comparing the metabolic profiles of emodin‐8‐O‐β‐d ‐glucopyranoside and polydatin between aqueous extract of RRPC and equivalent amounts of these two glycosides. The transitional constituents absorbed into blood were investigated in rats via intraduodental administration and portal vein intubation. A total of 38 prototype components and 43 metabolites were detected and characterized in vivo. The overall results demonstrated that the intestinal bacteria played an important role in the metabolism of RRPC, and the main metabolic pathways were hydrolysis in vitro, glucuronidation and sulfation in vivo.