水环境和水产品中β-N-甲氨基-L-丙氨酸(BMAA)检测方法和检出情况的研究进展

本文对蓝藻毒素β-N-甲氨基-L-丙氨酸(β-N-methylamino-L-alanine,BMAA)的结构形态、检测方法、环境和食物中的检出情况等方面进行系统综述.研究结果表明,BMAA主要存在3种赋存形态(游离态、溶解结合态、沉淀结合态);环境和食物中的BMAA类目前主要采用经过AQC衍生的LCMS/MS法检测,样品需经形态分离后、采用MCX固相萃取小柱处理.水环境、水产品和藻类保健品中BMAA类的污染已被大量报道.亚洲、北美洲、欧洲的相关环境和食物中均有一定的检出(检出浓度:水样<0.01—25.3μg·L^(-1);藻类<0.01—300μg·g^(-1);非鲨鱼水产品中0.08—115.3μg·g^(-1);藻类保健品中0.04—0.73μg·g^(-1)).BMAA存在生物积累和生物放大的现象,水产品中营养级别越高的生物检出浓度就越高,如鲨鱼类产品中检出浓度高达34—2011μg·g^(-1),需要引起重视.我国目前对BMAA的相关研究还很有限,未来应加强检测方法、现场调查、风险评估等相关方面的研究,以全面了解我国人群对BMAA类物质的暴露风险.

神经毒素BMAA的生物合成、食物链传递及其致病机理的研究进展与展望

本文参考有关BMAA的来源、作用机制及可能的生物合成过程等方面的研究论文,系统介绍了最早在苏铁组织中发现的BMAA毒素在淡水或海洋环境中蓝细菌、硅藻和甲藻样品中的检出情况及其沿食物链的生物放大作用,梳理了BMAA的毒性机制及可能的生物合成途径,并客观分析了BMAA诱发人神经退行性疾病的假说。最后,对BMAA未来的研究方向进行了展望。

神经毒素BMAA在淡水池塘水体中的健康风险及调控技术

为掌握中国常见淡水养殖生态系统中神经毒素β-N-甲氨基-L-丙氨酸BMAA的污染水平,文章选取典型淡水养殖池塘的水体、底泥及6种水产品(河蚬、铜锈环棱螺、日本沼虾、中华绒螯蟹、青鱼和鲫)进行BMAA的含量检测,在此基础上开展BMAA对人体的健康风险评估。同时采用L-半胱氨酸修饰后的氧化石墨烯为载体,结合化感物质“没食子酸”,制备新型化感缓释抑藻剂,研究其抑藻作用和调控BMAA毒素污染的效果。结果表明,上述6种水产品中BMAA的EDI值(估计每日摄入量)均远小于TDI值(每日容许摄入量),其浓度水平也远低于GV值(建议安全标准限值),对人体的健康风险较低;没食子酸浓度为12.5 mg/L制备的新型化感缓释抑藻剂既能保证较好的抑藻效果,又能有效调控BMAA毒素污染,添加7d后BMAA总量下降69.72%;经生物急性毒性测试发现,新型化感缓释抑藻剂具有良好的生态安全性,可应用至实际养殖池塘水体水华处理中。

神经毒素BMAA对球等鞭金藻(Isochrysis galbana)的生长抑制作用研究

神经毒素β-N-甲氨基-L-丙氨酸(β-N-methylamino-L-alanine,BMAA)主要来自淡水或海洋环境中的蓝藻和硅藻,在海洋生态系统中具有明显的生物放大作用,被认为是诱发阿尔茨海默症(Alzheimer’s Disease, AD)等多种神经退行性疾病的重要环境因子。近年, BMAA及其同分异构体2,4-二氨基丁酸(2,4-diaminobutyric acid, DAB)在我国及其他多个沿海国家和地区的贝类水产品中被普遍检出,潜在威胁消费者健康和海洋生态安全。但目前有关BMAA对海洋微藻的化学生态学作用尚不清楚。为此,通过向球等鞭金藻(Isochrysis galbana)培养基中分别添加不同浓度的BMAA及20种蛋白氨基酸,探究了BMAA单独及其与氨基酸联合作用96 h对球等鞭金藻比生长率和氨基酸含量的影响,并分析了微藻吸收外源BMAA的含量。结果表明,球等鞭金藻能吸收培养体系中的外源BMAA,吸收量与BMAA的添加浓度呈正相关,且进入细胞内的BMAA多半以溶解结合态形式存在;BMAA抑制批次培养的球等鞭金藻比生长率的96 h半效应浓度(96h-EC_(50))约为2μmol/L;与对照组相比,暴露于BMAA 96 h后球等鞭金藻细胞内酪氨酸、丙氨酸、丝氨酸等15种氨基酸的合成量明显降低;除脯氨酸、苏氨酸、甘氨酸外,其他17种氨基酸与BMAA联合暴露实验均增强了BMAA对球等鞭金藻比生长率的抑制效应,这可能与培养体系中的氨基酸促进了微藻吸收外源BMAA的能力有关。因此,海洋生态系统中BMAA毒素的化学生态学作用应引起人们的关注。有关BMAA抑制球等鞭金藻有丝分裂的分子机制有待进一步研究。

藻毒素β-N-甲氨基-L-丙氨酸(BMAA)的氯化降解

本文建立了高效液相色谱-串联质谱法(HPLC-MS/MS)来检测水中BMAA,并以次氯酸钠为消毒剂进行模拟氯化,研究BMAA的氯化降解及环境因子对BMAA降解的影响.结果表明,采用亲水交换作用色谱柱建立的HPLC-MS/MS分析方法,样品前处理过程简单易操作,在2—500μg·L^(-1)范围内线性关系良好(R2=0.9995),且检出限低(0.2μg·L^(-1)).在常规条件下(Cl∶N=2∶1,T=20℃,p H=7),BMAA能通过氯化得到有效降解,2 h降解率达到80%,6 h降解率达到97%;低的Cl∶N,低温及碱性条件下,BMAA的降解率显著降低.研究结果为饮用水预氯化及氯化消毒去除BMAA提供了理论依据.

提高大学生就业质量的BMAA培养模式分析

目前,全国各地如火如荼地进行着人才抢夺大战;毕业即失业,亦是大学生再熟悉不过的一个话题。人才抢夺与毕业即失业从侧面反映出教育与就业市场的供求失衡,学校与企业之间的信息不畅。通过调查北京和山东部分在校大学生,分析目前大学生就业存在的问题,为下一步通过实验经济学方法研究本科生培养模式改革的必要性和有效性打下基础。以提高大学生就业质量为目的,借鉴国内外现有培养模式,以本科生培养过程为核心,以学术发展与就业创业为导向,提出BMAA培养模式。

武汉官桥湖蓝藻毒素BMAA的生物累积与健康风险评估

鉴于蓝藻"水华"能产生新型神经毒素-β-N-甲氨基-L-丙氨酸(β-N-methylamino-L-alanine,BMAA),并通过生物富集作用在水生态系统的各营养级进行传递;选取武汉东湖子湖-官桥湖,采用HPLC-MS/MS分析方法,在蓝藻水华暴发期间,测定湖水、蓝藻及鱼体内游离态和蛋白结合态BMAA毒素的含量。结果表明,在水体中未检测到溶解态BMAA(在检测限0.05μg/L以下),但在微囊藻细胞及鱼体内(干重)均能检测到,含量均值分别为(0.040±0.002)μg/g和(0.32±0.317)μg/g,说明官桥湖在暴发水华后,蓝藻产生了BMAA毒素且被鱼类吸收和放大;不同鱼体(干重)累积BMAA的程度不同,总BMAA含量(干重)分别为鳑鲏(0.243±0.205)μg/g,鲫(0.126±0.040)μg/g,鲤(0.613±0.120)μg/g,鲢(0.028±0.018)μg/g,鳙(0.039±0.021)μg/g,鳊(0.879±0.243)μg/g;鲤和鳊的富集浓度较高,且与其它几种鱼有显著性差异(P<0.05)。按照WHO生活饮用水安全标准的建议进行推算,官桥湖鱼肉EDI值(估算的每天摄入量)为1.015μg/(kg·d),显著低于估算出的TDI值(日容许摄入量)0.5mg/(kg·d),基本不会对人造成急性中毒,但由于BMAA毒素为慢性毒素,不能忽视经常食用鱼肉后的累积风险。建议有关部门将东湖水产品的BMAA毒素纳入长期监测。

Investigation on cyanobacterial production of the proposed neurotoxinβ-N-methylamino-L-alanine(BMAA)

β-N-methylamino-L-alanine(BMAA)is an environmental neurotoxin thought to be produced by cyanobacteria.However,the cyanobacterial origin of BMAA remains controversial.The detection method and culture conditions of cyanobacteria are often cited as factors behind the discrepancy of published results.We showed previously that BMAA was highly toxic to the cyanobacterium Nostoc PCC 7120,and it is taken up via an amino acid transport system.Using a mutantΔnatAΔbgtA deficient in amino acid transport as a genetic control,we show here that BMAA taken up from the medium can be detected quantitatively at a threshold similar to,or below those reported,but was undetectable in the mutant.The BMAA isomer,2,4-diaminobutanoic acids(DAB),but not BMAA,could be detected in cell free extracts of Nostoc PCC 7120.Long-term(20 days)diazotrophic growth or nonlimiting supply of phosphate,conditions reported to enhance BMAA synthesis,did not lead to the detection of BMAA.An UPLC-MS/MS signal with a similar retention time to BMAA was found after prolonged diazotrophic incubation,but did not have fragment ions of BMAA after further analysis.When extended to 29 different cyanobacterial strains and 6 natural cyanobacterial bloom samples,none of them was found to produce BMAA.The cytotoxicity of BMAA to cyanobacteria,and the lack of a cellular protective mechanism against such toxicity,contradict the presence of a BMAA synthesis pathway in these organisms.More specific methods for BMAA detection in vivo need to be developed to clarify the cyanobacterial origin of BMAA.

不同液相色谱-质谱联用法分析贝类样品中神经毒素β-N-甲氨基-L-丙氨酸的比较

基于液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry,LC-MS/MS),比较了两种亲水交互作用(hydrophilic liquid interaction chromatography column,HILIC)色谱柱和C18色谱柱分析扁玉螺(Neverita didyma)、脉红螺(Rapana venosa)、栉江珧(Atrina pectinata)和菲律宾蛤仔(Ruditapes philippinarum)等贝类样品中神经毒素β-N-甲氨基-L-丙氨酸(β-N-methylamino-L-alanine,BMAA)及其同分异构体化合物的性能。本研究采用Agilent 6430串联质谱对3批扁玉螺样品中的游离态、总溶解态和沉淀结合态BMAA毒素进行了分析,通过AB Sciex Qtrap 4500质谱分析了其他3种贝类样品的总溶解态BMAA。结果表明,4种贝类样品均含有BMAA和低浓度的2,4-二氨基丁酸(2,4-diaminobutyric acid,DAB),且扁玉螺中的β-氨基-N-甲基丙氨酸(β-amino-N-methylalanine,BAMA)含量较低,其他3种贝类含有较高浓度的BAMA,但均未检出N-2-氨乙基甘氨酸[N-(2-aminoethyl)glycine,AEG]。HILIC-MS/MS直接分析法获得的定量结果均高于AQC-柱前衍生法的定量结果,建议使用HILIC-MS/MS直接分析法对生物样品中的BMAA进行定性和定量分析,采用变迁离子119->88和119->44的信号强度辅助定性,并使用前者的色谱峰面积进行定量计算,条件允许时可采用AQC-柱前衍生法进行辅助定性分析。本研究可为生物样品中BMAA毒素的检测分析提供重要的方法学参考。

一种新型压气机叶片造型方法的平面叶栅试验验证

为验证一种新型超/跨声压气机叶片造型方法——B样条控制中线角叶型、贝塞尔曲线控制叶型厚度方法 (BMAA方法)的有效性,分别与原有的可控扩散叶型定制造型和任意中线造型进行平面叶栅对比试验。结果表明,BMAA方法得到的跨声叶型,具有比定制叶型更优的气动性能;BMAA方法得到的超声叶型,具有与任意中线叶型相似的气动性能;与传统叶片造型方法相比,BMAA方法具有更高的效率,可提高叶片的气动负荷。

Trophic Interactions between Anadromous Juvenile Alewife (<i>Alosa pseudoharengus</i>) and Cyanobacterial Populations in a Shallow Mesotrophic Pond

Alosa pseudoharengus is an anadromous fish that migrates from marine to freshwaters to spawn. The early larval and juvenile forms are known to be planktivorous, where heavy feeding upon their preferred food source of large crustacean zooplankton often results in changes to composition and size structure within this trophic guild which in turn can result in shifts within the trophic spectrum and a classic trophic cascade. In this study of Lower Mill Pond, Brewster MA, we evaluated the feeding strategy of juvenile Alosa to determine whether juvenile alewife switches to feeding largely on cyanobacteria and whether cyanotoxins microcystin (MC) and β-methlyamino-L-alanine (BMAA) bioaccumulate in their muscle tissue. Within 15 - 30 days of their estimated spawning date, overexploitation of crustacean zooplankton resulted in a shift from planktivory to benthic detritivory for the majority of their life history, although this did not reduce their condition based on weight-length relationships (Log Wwt. = -5.503 + (3.101 × Log Length). Mean MC (0.003 μg·g-1 dwt) and BMAA (4.49 μg·g-1 dwt) concentrations in the muscle tissue of out-migrating juveniles were presumably derived from benthic subsidies, exporting freshwater cyanotoxins and creating a potential transfer to consumer of 0.0012 μg MC and 1.85 μg BMAA. Biodilution of MC and biomagnification of BMAA were observed. Depletion of the crustacean biomass by >95% resulted in an increase in the rotifer biomass, where Log crustacean (μg·L-1 dwt) = - 5.642 - (7.976 × Log rotifer (μg·L-1 dwt), and an increase in the amount of potentially edible <50 μm cyanobacterial biomass (r(8) = - 0.676, p = 0.046). A secondary cascade appears to have been maintained via invertebrate planktivory by Chaoborus spp.; however for a period of time edible cyanobacteria growth exceeded grazing pressure, resulting in a bloom of edible cyanobacteria. Continued grazing resulted in a shift to larger, inedible cyanobacterial communities where late season (October) surface accumulations were observed. The mass occurrence of juvenile Alosa pseudoharengus appears to be coupled to the sequential increases of cyanobacterial biomass via its influence on the trophic spectrum. Overall, the rotifer biomass (μg·L-1) was positively correlated with MC (pg·mL-1) (r(8) = 0.577, p = 0.104), and negatively correlated with BMAA (μg·L-1) (r(8) = - 0.388, p = 0.373) in the edible cyanobacterial fraction of the water column, although neither of these were significant.