Benzoic acid, a stimulant of odorant receptors of Bombyx mori, is rapidly metabolized to N-benzoylserine on the antennae

Summary. Benzoic acid is a known stimulant of olfactory receptor cells in trichoid sensilla on the antennae of adult females of Bombyx mori. Exposure of freshly excised antennae, from B. mori females and males, to vapours of [¹⁴C]-benzoic acid revealed that the adsorbed acid is rapidly metabolized (15% conversion in 10 s), suggesting the presence of a highly active enzymatic system. The major product could be identified as N-benzoylserine by use of [²H₅]-benzoic acid, and mass spectrometry linked to a gas chromatograph (GC-MS) or a liquid chromatograph (LC-MS), for analysis of the metabolites. The conjugation of benzoic acid with an amino acid apparently represents a novel mode for the rapid deactivation of odorant molecules. Received 26 March 2001.     

甲基一六O五降解菌J5的分离及其降解性状研究

从农药厂污水处理系统中分离到 1株降解甲基一六O五 (O ,O-二甲基 -O- 对硝基苯基 -硫代磷酸酯 ,简称MP)的芽胞杆菌 ,初步鉴定为蜡状芽胞杆菌 (Bacilluscereus)J5。J5能够高效降解MP ,但它不能利用MP作为唯一碳源生长 ,其代谢方式可能为共代谢。在有葡萄糖作为碳源的条件下 ,J5可以高效转化MP ,其转化效率可达 95 %以上。用薄层层析、紫外扫描和液相色谱法初步研究了J5对MP的降解性能及相关降解产物     

Fate in soil of 14C-sulfadiazine residues contained in the manure of young pigs treated with a veterinary antibiotic

The fate of ¹⁴C-labeled sulfadiazine (¹⁴C-SDZ) residues was studied in time-course experiments for 218 days of incubation using two soils (A_p horizon of loamy sand, orthic luvisol; A_p horizon of silt loam, cambisol) amended with fresh and aged (6 months) ¹⁴C-manure [40 g kg^?1 of soil; 6.36 mg of sulfadiazine (SDZ) equivalents per kg of soil], which was derived from two shoats treated with ¹⁴C-SDZ. Mineralization of ¹⁴C-SDZ residues was below 2% after 218 days depending little on soil type. Portions of extractable ¹⁴C (ethanol-water, 9:1, v/v) decreased with time to 4–13% after 218 days of incubation with fresh and aged ¹⁴C-manure and both soils. Non-extractable residues were the main route of the fate of the ¹⁴C-SDZ residues (above 90% of total recovered ¹⁴C after 218 days). These residues were high immediately after amendment depending on soil type and aging of the ¹⁴C-manure, and were stable and not remobilized throughout 218 days of incubation. Bioavailable portions (extraction using CaCl₂ solution) also decreased with increasing incubation period (5–7% after 218 days). Due to thin-layer chromatography (TLC), 500 μg of ¹⁴C-SDZ per kg soil were found in the ethanol-water extracts immediately after amendment with fresh ¹⁴C-manure, and about 50 μg kg^?1 after 218 days. Bioavailable ¹⁴C-SDZ portions present in the CaCl₂ extracts were about 350 μg kg^?1 with amendment. Higher concentrations were initially detected with aged ¹⁴C-manure (ethanol-water extracts: 1,920 μg kg^?1; CaCl₂ extracts: 1,020 μg kg^?1), probably due to release of ¹⁴C-SDZ from bound forms during storage. Consistent results were obtained by extraction of the ¹⁴C-manure-soil samples with ethyl acetate; portions of N-acetylated SDZ were additionally determined. All soluble ¹⁴C-SDZ residues contained in ¹⁴C-manure contributed to the formation of non-extractable residues; a tendency for persistence or accumulation was not observed. SDZ's non-extractable soil residues were associated with the soluble HCl, fulvic acids and humic acids fractions, and the insoluble humin fraction. The majority of the non-extractable residues appeared to be due to stable covalent binding to soil organic matter.     

Uptake of cadmium into cells in culture∗

Cadmium has been recognized as pollutant of the environment for many years and numerous studies on its toxic effects have been carried out. Little, however, is known about its metabolic behaviour e.g. why the metal is accumulated so extremely rapidly into the organs of men and animals. Since the study of the individual metabolic steps is very difficult in vivo cell cultures may be used to obtain first indications of what happens in the whole animal.

We used CHO cells in monolayer culture to study the conditions under which the uptake of cadmium occurs. From serumfree medium the metal is accumulated rapidly in the cells. The uptake is inhibited very strongly by the presence of serum or albumin. Accumulation occurs against a concentration gradient and is dependent on the incubation temperature. Below 10°C no cadmium uptake is seen. Several substances which are known to affect cell metabolism have been used to influence cadmium accumulation. Neither inhibitors of energy production nor microtubule or microfilament disruptors showed any substantial effect. In contrast SH‐group blocking agents markedly reduced cadmium uptake.

The results show that cadmium uptake does not occur by passive diffusion but by some active mechanism.     

物质代谢分析框架及其研究述评

追溯了物质代谢概念的起源和发展,剖析了不同学科视角下物质代谢内涵的共性和差异性,并将物质代谢划分为生命代谢、生态代谢和经济或社会代谢等三大类.在此基础上,根据研究重点和目标不同,将物质代谢分析划分为代谢主体分析和代谢物质分析两大类,并进一步细分为组织代谢、区域代谢、物质分析、材料分析;对主要的物质代谢分析方法的适用范围、研究对象进行了比较和界定.基于物质代谢分析框架,对国内外相关研究系统地进行了归纳和总结,客观分析和评价了当前研究存在的问题和不足,并展望了物质代谢研究的重点领域和发展方向.      

环境雌激素双酚A暴露现状及其雄性生殖毒性研究概况

双酚A(bisphenol A,BPA)作为典型的环境雌激素,在环境中广泛存在,具有接触机会频繁、剂量累积、潜伏期长等特点,是对生殖系统危害极大的一类污染物。研究表明BPA可在地表水、野生动物体内检测出,甚至在健康人群的体液中存在,尤其在婴儿体内含量较高。BPA进入机体后可通过I相和II相代谢酶分解,其分解产物的毒性目前仍不清楚。BPA在体内发挥雌激素样作用,与雌二醇竞争性地结合到雌激素受体上,阻碍雄激素受体的活性,促进促黄体生成素与催乳素的合成,最终抑制雄性激素的合成。BPA可破坏血睾屏障,直接刺激睾丸细胞的凋亡并导致精子质量下降,其中主要通过影响下丘脑-垂体-性腺轴(HPG)上促性腺激素释放激素受体(Gn RHR)、促黄体生成素受体(LHRβ)和促卵泡雌激素(Fshb)的表达和直接刺激睾丸和附睾细胞,降低睾酮合成酶的表达及活性,抑制与精子生成相关蛋白的表达,从而影响生殖能力。同时,BPA代谢过程中消耗大量的抗氧化酶,产生氧自由基,其氧化产物可能会对睾丸和附睾的损伤形成二次打击。总之,双酚A造成雄性生殖损伤障碍主要是损伤HPG轴正负反馈调节的平衡以及影响调节激素相关基因的表达和直接损伤睾丸细胞和精子质量。     

基于JACK的机务人员工作负荷评估

为了客观评估机务人员的工作负荷,选取作业能耗和姿态负荷作为评估机务人员工作负荷的指标。分解A320飞机主轮拆卸的维修任务,确定维修动作参数和姿态参数,使用JACK软件中的新陈代谢模块计算作业能耗,使用JACK软件中的RULA模块计算机务人员的姿态负荷,结果验证了该方法的可行性。相对于传统的评估工作负荷的方法,基于JACK仿真的方法具有省时高效的特点。     

多种政策对经济-环境系统的综合作用分析

提出了一套分析多种政策手段对社会经济系统物质流和价值流变化的综合作用的理论概念,弥补了现有不足.在理论概念的基础上,构建了由7个子模块组成的具体模型框架,以反映多种政策手段共同实施对物质流和价值流变化的综合作用.以我国为案例,利用提出的模型框架评估了我国7类典型环境经济政策对我国经济增长和物质流变化的综合和单独作用,证明了综合分析的必要性.     

外源NO介导Cu~(2+)胁迫下番茄幼苗活性氧与内源NO代谢的研究

采用营养液培养方法,研究Cu~(2+)胁迫下外源一氧化氮(nitric oxide,NO)介导的番茄幼苗活性氧及NO代谢途径。结果表明:在Cu~(2+)胁迫下,番茄叶片和根系氧自由基含量增加,NO释放量以及硝酸还原酶(nitrate reductase,NR)和一氧化氮合酶(nitric oxide synthase,NOS)活性降低。外源NO能提高Cu~(2+)胁迫下番茄叶片NR和NOS活性,促进NO的产生,根系NOS活性及NO产量也同时上升。外源NO使精氨酸含量显著增加,而Hb(牛血红蛋白,NO清除剂)可部分抵消NO的促进作用,使Cu~(2+)+SNP+Hb处理下番茄精氨酸含量显著下降。可见,外源NO的加入可通过酶促和非酶促途径促进Cu~(2+)胁迫下NO的合成,介导NO信号调控网络,调节内源NO、精氮酸和活性氧代谢途径,从而缓解过多Cu~(2+)引起的氧化伤害。     

g 辐照预处理促进剩余污泥发酵产氢的研究

为降低能耗,提高辐照技术的经济性,探讨了在0~9.5kGy范围内,γ辐照剂量对生活污水处理厂二沉池剩余污泥中耗氢菌的抑制效果和对发酵产氢的影响,建立了描述发酵产氢过程及辐照影响的动力学模型.结果表明,γ辐照剂量从0增加至9.5kGy时,污泥溶解率从0增加至4%,上清液中可检测出一定的蛋白质和多糖等物质,其中蛋白质中的氮素占溶出总氮素的90%,表明较低剂量辐照即对污泥菌体造成较明显的破解,这可在一定程度上抑制无法形成芽孢的耗氢菌活性;与之相对应的是污泥发酵产氢能力的明显提升,以葡萄糖为底物(1.0g/L),在35℃和初始pH值为7.0时,当辐射剂量仅为0.5kGy时,累积产氢量即比未辐照时有70%的提升,进一步增加辐照剂量至5kGy,累计产氢量和产氢得率均继续增长且达到最大值,分别为240mL/g葡萄糖和1.93mLH2/mol葡萄糖(发酵液的污泥量达2.0g VSS/L);此后,污泥发酵产氢能力随辐射剂量的增加而降低.修正的Logistic模型能很好地描述本研究中累积产氢量随时间的变化规律,而修正的Han-Levenspiel模型能很好地描述辐照剂量对平均产氢速率的影响.