BACKGROUND & AIMS: :Ammonium and the analogue methylammonium are taken into the cell by active transport systems which constitute a family of transmembrane proteins that have been identified in fungi, bacteria, plants, and animals. Two genes from Aspergillus nidulans, mepA and meaA, which encode ammonium transporters with different affinities have been characterized. The MepA transporter exhibits the highest affinity for methylammonium (Km, 44.3 microM); in comparison, the Km for MeaA is 3.04 mM. By use of targeted gene replacement strategies, meaA and mepA deletion mutants were created. Deletion of both meaA and mepA resulted in the inability of the strain to grow on ammonium concentrations of less than 10 mM. The single meaA deletion mutant exhibited reduced growth at the same concentrations, whereas the mepA deletion mutant displayed wild-type growth. Interestingly, multiple copies of mepA were found to complement the methylammonium resistance phenotype conferred by the deletion of meaA. The expression profiles for mepA and meaA differed; the mepA transcript was detected only in nitrogen-starved cultures, whereas meaA was expressed under both ammonium-sufficient and nitrogen starvation conditions. Together, these results indicate that MeaA constitutes the major ammonium transport activity and is required for the optimal growth of A. nidulans on ammonium as the sole nitrogen source and that MepA probably functions in scavenging low concentrations of ammonium under nitrogen starvation conditions.

背景与目标： : 铵和类似物甲基铵被主动转运系统带入细胞，这些转运系统构成了在真菌，细菌，植物和动物中已鉴定的跨膜蛋白家族。已经鉴定了来自构巢曲霉的两个基因mepA和meaA，它们编码具有不同亲和力的铵转运蛋白。MepA转运蛋白对甲基铵表现出最高的亲和力 (Km，44.3微米); 相比之下，MeaA的Km为3.04 mM。通过使用靶向基因替代策略，创建了meaA和mepA缺失突变体。meaA和mepA的缺失均导致菌株无法在小于10 mM的铵浓度下生长。单个meaA缺失突变体在相同浓度下表现出降低的生长，而mepA缺失突变体表现出野生型生长。有趣的是，发现多个mepA副本补充了meaA缺失所赋予的甲基铵抗性表型。mepA和meaA的表达谱有所不同; mepA转录物仅在缺乏氮的培养物中检测到，而meaA在铵充足和氮饥饿条件下均表达。总之，这些结果表明，MeaA构成了主要的铵转运活性，并且是在铵上最佳生长所必需的。作为唯一的氮源，MepA可能在氮饥饿条件下清除低浓度的铵。

BACKGROUND & AIMS:

背景与目标：

BACKGROUND & AIMS:

背景与目标：

BACKGROUND & AIMS: :The ratio of the major monensin analogs produced by Streptomyces cinnamonensis is dependent upon the relative levels of the biosynthetic precursors methylmalonyl-coenzyme A (CoA) (monensin A and monensin B) and ethylmalonyl-CoA (monensin A). The meaA gene of this organism was cloned and sequenced and was shown to encode a putative 74-kDa protein with significant amino acid sequence identity to methylmalonyl-CoA mutase (MCM) (40%) and isobutyryl-CoA mutase (ICM) large subunit (36%) and small subunit (52%) from the same organism. The predicted C terminus of MeaA contains structural features highly conserved in all coenzyme B12-dependent mutases. Plasmid-based expression of meaA from the ermE* promoter in the S. cinnamonensis C730.1 strain resulted in a decreased ratio of monensin A to monensin B, from 1:1 to 1:3. Conversely, this ratio increased to 4:1 in a meaA mutant, S. cinnamonensis WM2 (generated from the C730.1 strain by insertional inactivation of meaA by using the erythromycin resistance gene). In both of these experiments, the overall monensin titers were not significantly affected. Monensin titers, however, did decrease over 90% in an S. cinnamonensis WD2 strain (an icm meaA mutant). Monensin titers in the WD2 strain were restored to at least wild-type levels by plasmid-based expression of the meaA gene or the Amycolatopsis mediterranei mutAB genes (encoding MCM). In contrast, growth of the WD2 strain in the presence of 0.8 M valine led only to a partial restoration (<25%) of monensin titers. These results demonstrate that the meaA gene product is significantly involved in methylmalonyl-CoA production in S. cinnamonensis and that under the tested conditions the presence of both MeaA and ICM is crucial for monensin production in the WD2 strain. These results also indicate that valine degradation, implicated in providing methylmalonyl-CoA precursors for many polyketide biosynthetic processes, does not do so to a significant degree for monensin biosynthesis in the WD2 mutant.

背景与目标： : 肉桂链霉菌产生的主要莫能菌素类似物的比例取决于生物合成前体甲基丙二酰辅酶a (CoA) (莫能菌素A和莫能菌素B) 和乙基丙二酰辅酶a (莫能菌素A) 的相对水平。克隆并测序了该生物的meaA基因，并显示出编码与甲基丙二酰辅酶a变位酶 (MCM) (40%) 和异丁酰辅酶a变位酶 (ICM) 大亚基 (36%) 和小亚基 (52%) 具有显着氨基酸序列同一性的推定74 kDa蛋白有机体。MeaA的预测C末端包含在所有辅酶B12-dependent突变酶中高度保守的结构特征。在肉桂S. cinnamonensis C730.1菌株中，来自ermme * 启动子的meaA基于质粒的表达导致莫能菌素a与莫能菌素B的比例从1:1降低到1:3。相反，在meaA突变体，S. cinnamonensis WM2 (通过使用红霉素抗性基因对meaA进行插入失活而由C730.1菌株产生) 中，该比率增加至4:1。在这两个实验中，总体莫能菌素滴度没有受到显着影响。然而，随着90% 的推移，在肉桂S. cinnamonensis WD2菌株 (一种icmmeaa突变体) 中，莫能菌素滴度确实降低。通过meaA基因或Amycolatopsis mediterranei mutAB基因 (编码MCM) 的基于质粒的表达，将WD2菌株中的莫能菌滴度至少恢复到野生型水平。相反，在0.8 M缬氨酸存在下WD2菌株的生长仅导致莫能菌素滴度的部分恢复 (<25%)。这些结果表明，meaA基因产物显着参与了肉桂草中甲基丙二酰辅酶a的产生，并且在测试条件下，MeaA和ICM的存在对于WD2菌株中的莫能菌素的产生至关重要。这些结果还表明，缬氨酸降解与为许多聚酮化合物生物合成过程提供甲基丙二酰辅酶a前体有关，对WD2突变体中的莫能菌素生物合成没有很大程度的影响。

BACKGROUND & AIMS: OBJECTIVE:The principal aim of the study was to estimate the level of exposure to organic solvents of graffiti removers, and to identify the chemicals used in different cleaning agents. A secondary objective was to inform about the toxicity of various products and to optimise working procedures. METHODS:Exposure to organic solvents was determined by active air sampling and biological monitoring among 38 graffiti removers during an 8-h work shift in the Stockholm underground system. The air samples and biological samples were analysed by gas chromatography. Exposure to organic solvents was also assessed by a questionnaire and interviews. RESULTS:Solvents identified were N-methylpyrrolidone (NMP), dipropylene glycol monomethyl ether (DPGME), propylene glycol monomethyl ether (PGME), diethylene glycol monoethyl ether (DEGEE), toluene, xylene, pseudocumene, hemimellitine, mesitylene, ethylbenzene, limonene, nonane, decane, undecane, hexandecane and gamma-butyrolactone. The 8-h average exposures [time-weighted average (TWA)] were below 20% of the Swedish permissible exposure limit value (PEL) for all solvents identified. In poorly ventilated spaces, e.g. in elevators etc., the short-term exposures exceeded occasionally the Swedish short-term exposure limit values (STEL). The blood and urine concentrations of NMP and its metabolites were low. Glycol ethers and their metabolites (2-methoxypropionic acid (MPA), ethoxy acetic acid (EAA), butoxy acetic acid (BAA), and 2-(2-methoxyethoxy) acetic acid (MEAA)) were found in low concentrations in urine. There were significant correlation between the concentrations of NMP in air and levels of NMP and its metabolites in blood and urine. The use of personal protective equipment, i.e. gloves and respirators, was generally high. CONCLUSIONS:Many different cleaning agents were used. The average exposure to solvents was low, but some working tasks included relatively high short-term exposure. To prevent adverse health effects, it is important to inform workers about the health risks and to restrict the use of the most toxic chemicals. Furthermore, it is important to develop good working procedures and to encourage the use of personal protection equipment.

背景与目标：

BACKGROUND & AIMS: :A study of workers exposed to jet fuel propellant 8 (JP-8) was conducted at U.S. Air Force bases and included the evaluation of three biomarkers of exposure: S-benzylmercapturic acid (BMA), S-phenylmercapturic acid (PMA), and (2-methoxyethoxy)acetic acid (MEAA). Postshift urine specimens were collected from various personnel categorized as high (n = 98), moderate (n = 38) and low (n = 61) JP-8 exposure based on work activities. BMA and PMA urinary levels were determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and MEAA urinary levels were determined by gas chromatography-mass spectrometry (GC-MS). The numbers of samples determined as positive for the presence of the BMA biomarker (above the test method's limit of detection [LOD = 0.5 ng/ml]) were 96 (98.0%), 37 (97.4%), and 58 (95.1%) for the high, moderate, and low (control) exposure workgroup categories, respectively. The numbers of samples determined as positive for the presence of the PMA biomarker (LOD = 0.5 ng/ml) were 33 (33.7%), 9 (23.7%), and 12 (19.7%) for the high, moderate, and low exposure categories. The numbers of samples determined as positive for the presence of the MEAA biomarker (LOD = 0.1 μ g/ml) were 92 (93.4%), 13 (34.2%), and 2 (3.3%) for the high, moderate, and low exposure categories. Statistical analysis of the mean levels of the analytes demonstrated MEAA to be the most accurate or appropriate biomarker for JP-8 exposure using urinary concentrations either adjusted or not adjusted for creatinine; mean levels of BMA and PMA were not statistically significant between workgroup categories after adjusting for creatinine.

背景与目标： : 在美国空军基地对暴露于喷气燃料推进剂8 (JP-8) 的工人进行了一项研究，其中包括对三种暴露生物标志物的评估: S-苄基巯基乙酸 (BMA)，S-苯基巯基乙酸 (PMA)，和 (2-甲氧基乙氧基) 乙酸 (MEAA)。移位后尿液标本来自分类为高 (n = 98) 的各种人员，基于工作活动的中等 (n = 38) 和低 (n = 61) JP-8暴露。通过高效液相色谱-串联质谱法 (hplc-ms/MS) 测定BMA和PMA尿水平，用气相色谱-质谱法 (gc-ms) 测定MEAA尿水平，经测定为BMA生物标志物阳性 (高于检测方法的检出限 [LOD = 0.5 ng/ml]) 的样品数为96 (98.0%)，高、中、低 (对照) 暴露工作组类别分别为37 (97.4%) 和58 (95.1%)。对于PMA生物标志物 (LOD = 0.5 ng/ml) 的存在，被确定为阳性的样品数量为33 (33.7%)，9 (23.7%)，高、中、低暴露类别的12 (19.7%)。对于MEAA生物标志物 (LOD = 0.1 μ g/ml) 的存在，被确定为阳性的样品数量分别为92 (93.4%) 、13 (34.2%) 和2 (3.3%) 的高，中度和低暴露类别。对分析物平均水平的统计分析表明，MEAA是使用尿浓度调整或未调整肌酐的最准确或最合适的JP-8暴露生物标志物; 调整肌酐后，研究组类别之间的BMA和PMA的平均水平无统计学意义。

BACKGROUND & AIMS: :2-Methyl-6-ethylaniline (MEA) is the main microbial degradation intermediate of the chloroacetanilide herbicides acetochlor and metolachlor. Sphingobium sp. strain MEA3-1 can utilize MEA and various alkyl-substituted aniline and phenol compounds as sole carbon and energy sources for growth. We isolated the mutant strain MEA3-1Mut, which converts MEA only to 2-methyl-6-ethyl-hydroquinone (MEHQ) and 2-methyl-6-ethyl-benzoquinone (MEBQ). MEA may be oxidized by the P450 monooxygenase system to 4-hydroxy-2-methyl-6-ethylaniline (4-OH-MEA), which can be hydrolytically spontaneously deaminated to MEBQ or MEHQ. The MEA microbial metabolic pathway was reconstituted based on the substrate spectra and identification of the intermediate metabolites in both the wild-type and mutant strains. Plasmidome sequencing indicated that both strains harbored 7 plasmids with sizes ranging from 6,108 bp to 287,745 bp. Among the 7 plasmids, 6 were identical, and pMEA02' in strain MEA3-1Mut lost a 37,000-bp fragment compared to pMEA02 in strain MEA3-1. Two-dimensional electrophoresis (2-DE) and protein mass fingerprinting (PMF) showed that MEA3-1Mut lost the two-component flavin-dependent monooxygenase (TC-FDM) MeaBA, which was encoded by a gene in the lost fragment of pMEA02. MeaA shared 22% to 25% amino acid sequence identity with oxygenase components of some TC-FDMs, whereas MeaB showed no sequence identity with the reductase components of those TC-FDMs. Complementation with meaBA in MEA3-1Mut and heterologous expression in Pseudomonas putida strain KT2440 resulted in the production of an active MEHQ monooxygenase.

背景与目标： : 2-甲基-6-乙基苯胺 (MEA) 是氯乙酰苯胺除草剂乙草胺和异丙甲草胺的主要微生物降解中间体。鞘氨醇菌株MEA3-1可以利用MEA和各种烷基取代的苯胺和酚化合物作为唯一的碳和能源来生长。我们分离了突变菌株MEA3-1Mut，该菌株仅将MEA转化为2-甲基-6-乙基对苯二酚 (MEHQ) 和2-甲基-6-乙基-苯醌 (MEBQ)。MEA可能被P450单加氧酶系统氧化为4-羟基-2-甲基-6-乙基苯胺 (4-OH-MEA)，可将其自发水解脱氨为MEBQ或MEHQ。根据底物光谱和鉴定野生型和突变菌株中的中间代谢物，重构了MEA微生物代谢途径。质体测序表明，两种菌株都含有7个质粒，其大小范围为6,108 bp至287,745 bp。在7个质粒中，6个是相同的，与菌株MEA3-1中的pMEA02相比，菌株MEA3-1Mut中的pMEA02失去了37,000 bp的片段。二维电泳 (2-DE) 和蛋白质质量指纹图谱 (PMF) 显示，MEA3-1Mut丢失了双组分黄素依赖性单加氧酶 (TC-FDM) MeaBA，该酶由pmea02丢失片段中的一个基因编码。MeaA与某些TC-FDMs的加氧酶组分共享25% 氨基酸序列同一性的22%，而MeaB与那些TC-FDMs的还原酶组分没有序列同一性。与meaBA在MEA3-1Mut中的互补和恶臭假单胞菌菌株KT2440中的异源表达导致产生活性MEHQ单加氧酶。

BACKGROUND & AIMS: :The movement of ammonium across biological membranes is mediated in both prokaryotes and eukaryotes by ammonium transport proteins (AMT/MEP) that constitute a family of related sequences. We have previously identified two ammonium permeases in Aspergillus nidulans, encoded by the meaA and mepA genes. Here we show that meaA is expressed in the presence of ammonium, consistent with the function of MeaA as the main ammonium transporter required for optimal growth on ammonium as a nitrogen source. In contrast, mepA, which encodes a high-affinity ammonium permease, is expressed only under nitrogen-limiting or starvation conditions. We have identified two additional AMT/MEP-like genes in A. nidulans, namely, mepB, which encodes a second high-affinity ammonium transporter expressed only in response to complete nitrogen starvation, and mepC, which is expressed at low levels under all nitrogen conditions. The MepC gene product is more divergent than the other A. nidulans AMT/MEP proteins and is not thought to significantly contribute to ammonium uptake under normal conditions. Remarkably, the expression of each AMT/MEP gene under all nitrogen conditions is regulated by the global nitrogen regulatory GATA factor AreA. Therefore, AreA is also active under nitrogen-sufficient conditions, along with its established role as a transcriptional activator in response to nitrogen limitation.

背景与目标： : 在原核生物和真核生物中，铵跨生物膜的运动均由构成相关序列家族的铵转运蛋白 (AMT/MEP) 介导。我们先前已经在构巢曲霉中鉴定出两种由meaA和mepA基因编码的铵盐。在这里，我们表明meaA在铵的存在下表达，这与MeaA作为铵作为氮源的最佳生长所需的主要铵转运蛋白的功能一致。相反，编码高亲和力铵渗透酶的mepA仅在氮限制或饥饿条件下表达。我们已经在niddulans中鉴定了另外两个AMT/MEP样基因，即mepB和mepC，mepB编码仅在完全氮饥饿时表达的第二种高亲和力铵转运蛋白，mepC在所有氮条件下均以低水平表达。MepC基因产物比其他A.Niddulans AMT/MEP蛋白更分散，并且被认为在正常条件下不会显着促进铵的吸收。值得注意的是，在所有氮条件下，每个AMT/MEP基因的表达均受全球氮调节GATA因子区域的调节。因此，AreA在氮充足的条件下也具有活性，以及其作为响应氮限制的转录激活因子的既定作用。

BACKGROUND & AIMS: :In Syrian hamsters, reproductive behavior relies on the perception of chemical signals released from conspecifics. The medial amygdala (MEA) processes sexual odors through functionally distinct, but interconnected, sub-regions; the anterior MEA (MEAa) appears to function as a chemosensory filter to distinguish between opposite-sex and same-sex odors, whereas the posterodorsal MEA (MEApd) is critical for generating attraction specifically to opposite-sex odors. To identify how these sub-regions interact during odor processing, we measured odor-induced Fos expression, an indirect marker of neuronal activation, in the absence of either MEAa or MEApd processing. In Experiment 1, electrolytic lesions of the MEAa decreased Fos expression throughout the posterior MEA in male hamsters exposed to either female or male odors, whereas MEApd lesions had no effect on Fos expression within the MEAa. These results indicate that the MEAa normally enhances processing of sexual odors within the MEApd and that this interaction is primarily unidirectional. Furthermore, lesions of the MEAa, but not the MEApd, decreased Fos expression within several connected forebrain nuclei, suggesting that the MEAa provides the primary excitatory output of the MEA during sexual odor processing. In Experiment 2, we observed a similar pattern of decreased Fos expression, using fiber-sparing, NMDA lesions of the MEAa, suggesting that the decreases in Fos expression were not attributable exclusively to damage to passing fibers. Taken together, these results provide the first direct test of how the different sub-regions within the MEA interact during odor processing, and highlight the role of the MEAa in transmitting sexual odor information to the posterior MEA, as well as to related forebrain nuclei.

背景与目标： : 在叙利亚仓鼠中，生殖行为依赖于对同种异体释放的化学信号的感知。内侧杏仁核 (MEA) 通过功能上不同但相互关联的子区域处理性气味; 前MEA (MEAa) 似乎起着化学感觉过滤器的作用，以区分异性和同性气味，后嗅MEA (MEApd) 对于产生特别针对异性气味的吸引力至关重要。为了确定这些子区域在气味处理过程中如何相互作用，我们在没有MEAa或MEApd处理的情况下测量了气味诱导的Fos表达，这是神经元激活的间接标记。在实验1中，在暴露于雌性或雄性气味的雄性仓鼠中，MEAa的电解病变降低了整个后路MEA的Fos表达，而MEApd病变对MEAa内的Fos表达没有影响。这些结果表明，MEAa通常会增强MEApd内性气味的处理，并且这种相互作用主要是单向的。此外，MEAa的病变 (而不是MEApd) 降低了几个相连的前脑核中的Fos表达，这表明MEAa在性气味处理过程中提供了MEA的主要兴奋性输出。在实验2中，我们使用MEAa的纤维保留，NMDA病变观察到类似的Fos表达降低模式，这表明Fos表达的降低并非仅归因于对通过纤维的损害。总之，这些结果提供了有关MEA内不同子区域在气味处理过程中如何相互作用的第一个直接测试，并强调了MEAa在将性气味信息传递到后MEA以及相关的前脑中的作用核。

BACKGROUND & AIMS: PURPOSE:To demonstrate the utility of the urinary metabolite (2-methoxyethoxy)acetic acid (MEAA) as a biomarker of exposure. 2-(2-methoxyethoxy)ethanol [diethylene glycol monomethyl ether] is an anti-icing agent used in the formulation of JP-8, and it is added at a known uniform 0.1% (v/v) concentration to each batch lot. JP-8 is a kerosene-based fuel containing different compounds that vary in the content of every batch/lot of fuel; thus, MEAA has the potential to be a more specific and a consistent quantitative biomarker for JP-8 exposure. METHODS:MEAA was used to measure exposure of jet propulsion fuel 8 (JP-8) in United States Air Force (USAF) personnel working at six airbases within the United States. Post-shift urine specimens from various personnel including high (n = 98), moderate (n = 38), and low (n = 61) exposure workgroup categories were collected and analyzed by a gas chromatographic-mass spectrometric test method. The three exposure groups were evaluated for the number per group positive for MEAA, and a statistical analysis consisted of pair-wise t-tests for unequal variances was used to test for the differences in mean MEAA concentrations between the exposure groups. RESULTS:The number of samples detected as positive for MEAA exposure, that is, those above the test method's limit of detection (LOD = 0.1 μg/ml), were 92 (93.9%), 13 (34.2%), and 2 (3.3%) for the high, moderate, and low exposure workgroup categories, respectively. The mean urinary MEAA level was significantly greater in the high exposure category (6.8 μg/ml), compared to the moderate (0.42 μg/ml) and the low (0.07 μg/ml) exposure categories. The maximum concentration of urinary MEAA was 110 μg/ml for the high exposure category, while 4.8 μg/ml and 0.2 μg/ml maximum levels were found in the moderate and low exposure categories, respectively. CONCLUSION:This study demonstrated that urinary MEAA can be used as an accurate biomarker of exposure for JP-8 workers and clearly distinguished the differences in JP-8 exposure by workgroup category.

背景与目标：

BACKGROUND & AIMS: :2-Methoxyacetic and 2-ethoxyacetic acids are well known toxic metabolites of 2-alkoxyethanols. The use of 2-alkoxyethanols is now restricted, and the regulations have forced manufacturers to find substitutive solvents, 2-(2-alkoxyethoxy)ethanols. 2-(2-Alkoxyethoxy)ethanols resemble 2-alkoxyethanols, and their most hazardous similarity is their ability to metabolize to the 2-(2-alkoxyethoxy)acetic acids. In the present study, floor lacquerers' (n = 22) inhalation and total exposure to 2-(2-alkoxy)ethoxyethanols was measured. The measurements of inhalation exposure were done with charcoal tubes, and total exposure was biomonitored by urinalysis of 2-(2-alkoxyethoxy)acetic acids. The 8h inhalation exposures of floor lacquerers to 2-(2-methoxyethoxy)ethanol (DEGME), 2-(2-ethoxyethoxy)ethanol (DEGEE) and 2-(2-butoxyethoxy)ethanol (DEGBE) were in average 0.23 +/- 0.07 ppm (average+/-S.D., n = 3), 0.08 +/- 0.07 ppm (n = 16), and 0.05 +/- 0.03 ppm (n = 16), respectively. The excretions of 2-(2-methoxyethoxy)acetic acid (MEAA), 2-(2-ethoxyethoxy)acetic acid (EEAA) and 2-(2-butoxyethoxy)acetic acid (BEAA) were in average 4.9 +/- 4.3 mmol/mol creatinine, 9.3 +/- 8.0 mmol/mol creatinine and 9.2 +/- 7.4 mmol/mol creatinine, respectively. A linear relationship was found between the urinary 2-(2-alkoxyethoxy)acetic acid concentrations and the preceding 8-h occupational exposure to 2-(2-alkoxyethoxy)ethanol.

背景与目标： : 2-甲氧基乙酸和2-乙氧基乙酸是众所周知的2-烷氧基乙醇的有毒代谢产物。2-烷氧基乙醇的使用现在受到限制，法规迫使制造商寻找替代溶剂，2-(2-烷氧基乙氧基) 乙醇。2-(2-烷氧基乙氧基) 乙醇类似于2-烷氧基乙醇，它们最危险的相似之处是它们代谢成2-(2-烷氧基乙氧基) 乙酸的能力。在本研究中，测量了地板漆器 (n = 22) 的吸入和2-(2-烷氧基) 乙氧基乙醇的总暴露量。吸入暴露量的测量是用木炭管进行的，并且通过2-(2-烷氧基乙氧基) 乙酸的尿液分析对总暴露量进行生物监测。地板漆器对2-(2-甲氧基乙氧基) 乙醇 (DEGME) 的8小时吸入暴露，2-(2-乙氧基乙氧基) 乙醇 (DEGEE) 和2-(2-丁氧基乙氧基) 乙醇 (DEGBE) 平均0.23 +/- 0.07 ppm (平均 +/-s.d.，n = 3)，0.08 +/- 0.07 ppm (n = 16)，和0.05 +/- 0.03 ppm (n = 16)。2-(2-甲氧基乙氧基) 乙酸 (MEAA) 的排泄物，2-(2-乙氧基乙氧基) 乙酸 (EEAA) 和2-(2-丁氧基乙氧基) 乙酸 (BEAA) 平均4.9 +/- 4.3 mmol/mol肌酐，9.3 +/- 8.0 mmol/mol肌酐和9.2 +/- 7.4 mmol/mol肌酐，分别发现尿中的2-(2-烷氧基乙氧基) 乙酸浓度与前8小时职业暴露2-(2-烷氧基乙氧基) 乙醇之间存在线性关系。

BACKGROUND & AIMS: :The metabolism of the reproductive and developmental toxicant bis(2-methoxyethyl)ether (diglyme) was studied in isolated rat hepatocytes and in the intact rat. Male Sprague-Dawley rats (190-220 g) were used in both studies. Hepatocytes, isolated by a two-step in situ collagenase perfusion of the liver, were cultured as monolayers and incubated with [14C]diglyme at 1, 10, 30, and 50 microM for up to 48 h. For the in vivo study, rats were given single oral doses of [14C]diglyme at 5.1 mmol/kg body wt, and urine was collected for up to 96 h. Radioactive compounds in the culture medium or in the urine were separated by high performance liquid chromatography and quantified with an in-line radioactivity monitor. Metabolites were identified by comparison of their chromatographic retention times and their mass spectra with those of authentic compounds. The principal metabolite from hepatocytes and in the urine was (2-methoxyethoxy)acetic acid (MEAA). This metabolite accounted for approximately 36% of the radioactivity in the 48-h culture medium and about 67% of the administered dose in the 48-h urine. Other prominent metabolites common to both systems included 2-(2-methoxyethoxy)ethanol, methoxyacetic acid (MAA), 2-methoxyethanol, and diglycolic acid. The diglyme metabolite profiles from urine and from hepatocytes were qualitatively similar, demonstrating that, in the rat, hepatocytes serve as a good model system for predicting the urinary metabolites of diglyme. Moreover, MEAA was shown to be the metabolite best suited for use as a short-term biological marker of exposure to diglyme.(ABSTRACT TRUNCATED AT 250 WORDS)

背景与目标： : 在分离的大鼠肝细胞和完整的大鼠中研究了生殖和发育毒性双 (2-甲氧基乙基) 醚 (dlyme) 的代谢。两项研究中都使用了雄性Sprague-Dawley大鼠 (190-220g)。肝细胞，通过肝脏的两步原位胶原酶灌注分离，以单层培养，并与 [14C] 二甘醇在1、10、30和50微米下孵育长达48小时。对于体内研究，给大鼠单次口服剂量为5.1 mmol/kg体重的 [14C] 二甘醇，收集尿液长达96小时。培养基或尿液中的放射性化合物通过高效液相色谱分离，并用在线放射性监测仪定量。通过将其色谱保留时间和质谱与真实化合物进行比较来鉴定代谢物。主要代谢物来自肝细胞和尿液中的是 (2-甲氧基乙氧基) 乙酸 (MEAA)。这种代谢物约占48小时培养基中放射性的36%，约占48小时尿液中给药剂量的67%。这两个系统常见的其他突出代谢物包括2-(2-甲氧基乙氧基) 乙醇,甲氧基乙酸 (MAA)，2-甲氧基乙醇和二乙醇酸。尿液和肝细胞的二甘醇胺代谢物谱在定性上相似，表明在大鼠中，肝细胞是预测二甘醇胺尿代谢物的良好模型系统。此外，MEAA被证明是最适合用作暴露于dlyme的短期生物标志物的代谢物。(摘要截短于250字)

BACKGROUND & AIMS: :The objective of this study was to examine differences between fluent English-speaking ethnically diverse (ED) individuals (from Hispanic, Asian and Middle-Eastern descent) and monolingual English-speaking Anglo-Americans (MEAA) on commonly used tests of information processing and attention. A sample of 123 (84 ED and 39 MEAA) healthy individuals participated. The results revealed that the MEAA group outperformed the ED group on Trail Making Test Part B, Stroop B and C, and Auditory Consonant Trigrams (18s delay condition). Additionally, a host of acculturation variables such as score on a formal acculturation scale, amount of time educated outside of the U.S., and the amount of English spoken when growing up correlated with these various neuropsychological tests. The findings from this study highlight the importance of taking acculturation into account for fluent English-speaking ED individuals when administering and interpreting neuropsychological tests.

背景与目标： : 这项研究的目的是在常用的信息测试中，研究流利的讲英语的族裔 (ED) 个体 (来自西班牙裔，亚洲人和中东血统) 与讲英语的盎格鲁裔美国人 (MEAA) 之间的差异处理和注意。参加了123名 (84名ED和39名MEAA) 健康个体的样本。结果表明，MEAA组在跟踪测试B部分，Stroop B和C以及听觉辅音三叉音 (18s延迟条件) 方面优于ED组。此外，许多适应变量 (例如正式适应量表上的分数，在美国以外受教育的时间以及长大后说英语的数量) 与这些各种神经心理学测试相关。这项研究的发现强调了在进行和解释神经心理学测试时，对流利的英语ED个体考虑适应的重要性。

BACKGROUND & AIMS: :The amino acid profiles, modified essential amino acid (MEAA) indexes, and in vitro pepsin digestibilities were determined for single-cell protein (SCP) from certain industrially important lactobacilli. For the three parameters examined, substantial differences were seen between different Lactobacillus species and between strains with a given species. SCP from all of the lactobacilli examined appeared relatively high in MEAA indexes and pepsin digestibility. SCP from L. acidophilus 3205 and L. fermenti 3954 had the highest MEAA indexes, whereas L. bulgaricus 2217 and L. thermophilus 3863 had the highest percentage of digestible crude protein. SCP from L. plantarum strains had the lowest MEAA indexes. The essential amino acid compositions of SCP from different lactobacilli appear comparable to that of Food and Agriculture Organization reference protein and SCP from other sources.

背景与目标： : 确定了某些工业上重要的乳杆菌的单细胞蛋白 (SCP) 的氨基酸谱，修饰的必需氨基酸 (MEAA) 指数和体外胃蛋白酶消化率。对于所检查的三个参数，在不同的乳杆菌物种之间以及具有给定物种的菌株之间发现了实质性差异。所检查的所有乳酸杆菌的SCP在MEAA指数和胃蛋白酶消化率方面均相对较高。嗜酸乳杆菌3205和3954的SCP具有最高的MEAA指数，而保加利亚乳杆菌2217和嗜热乳杆菌3863具有最高的可消化粗蛋白百分比。植物菌株的SCP MEAA指数最低。来自不同乳酸杆菌的SCP的必需氨基酸组成似乎与粮食和农业组织参考蛋白和其他来源的SCP相当。

BACKGROUND & AIMS: :Ammonium and the analogue methylammonium are taken into the cell by active transport systems which constitute a family of transmembrane proteins that have been identified in fungi, bacteria, plants, and animals. Two genes from Aspergillus nidulans, mepA and meaA, which encode ammonium transporters with different affinities have been characterized. The MepA transporter exhibits the highest affinity for methylammonium (Km, 44.3 microM); in comparison, the Km for MeaA is 3.04 mM. By use of targeted gene replacement strategies, meaA and mepA deletion mutants were created. Deletion of both meaA and mepA resulted in the inability of the strain to grow on ammonium concentrations of less than 10 mM. The single meaA deletion mutant exhibited reduced growth at the same concentrations, whereas the mepA deletion mutant displayed wild-type growth. Interestingly, multiple copies of mepA were found to complement the methylammonium resistance phenotype conferred by the deletion of meaA. The expression profiles for mepA and meaA differed; the mepA transcript was detected only in nitrogen-starved cultures, whereas meaA was expressed under both ammonium-sufficient and nitrogen starvation conditions. Together, these results indicate that MeaA constitutes the major ammonium transport activity and is required for the optimal growth of A. nidulans on ammonium as the sole nitrogen source and that MepA probably functions in scavenging low concentrations of ammonium under nitrogen starvation conditions.

背景与目标： : 铵和类似物甲基铵被主动转运系统带入细胞，这些转运系统构成了在真菌，细菌，植物和动物中已鉴定的跨膜蛋白家族。已经鉴定了来自构巢曲霉的两个基因mepA和meaA，它们编码具有不同亲和力的铵转运蛋白。MepA转运蛋白对甲基铵表现出最高的亲和力 (Km，44.3微米); 相比之下，MeaA的Km为3.04 mM。通过使用靶向基因替代策略，创建了meaA和mepA缺失突变体。meaA和mepA的缺失均导致菌株无法在小于10 mM的铵浓度下生长。单个meaA缺失突变体在相同浓度下表现出降低的生长，而mepA缺失突变体表现出野生型生长。有趣的是，发现多个mepA副本补充了meaA缺失所赋予的甲基铵抗性表型。mepA和meaA的表达谱有所不同; mepA转录物仅在缺乏氮的培养物中检测到，而meaA在铵充足和氮饥饿条件下均表达。总之，这些结果表明，MeaA构成了主要的铵转运活性，并且是在铵上最佳生长所必需的。作为唯一的氮源，MepA可能在氮饥饿条件下清除低浓度的铵。