Evaluating the Risk of Liver Cancer in Humans Exposed to Trichloroethylene Using Physiological Models

Trichloroethylene (TCE) is a widespread environmental pollutant. TCE is classified as a rodent carcinogen by the U.S. Environmental Protection Agency (EPA). Using the rodent cancer bioassay findings and estimates of metabolized dose, the EPA has estimated lifetime exposure cancer risks for humans that ingest TCE in drinking water or inhale TCE. In this study, a physiologically based pharmacokinetic (PB-PK) model for mice was used to simulate selected gavage and inhalation bioassays with TCE. Plausible dose-metrics thought to be linked with the mechanism of action for TCE carcinogenesis were selected. These dose-metrics, adjusted to reflect an average amount per day for a lifetime, were metabolism of TCE (AMET, mg/kg/day) and systemic concentration of TCA (AUCTCA, mg/L/day). These dose-metrics were then used in a linearized multistage model to estimate AMET and AUCTCA values that correspond to liver cancer risks of 1 in 1 million in mice. A human PB-PK model for TCE was then used to predict TCE concentrations in drinking water and air that would provide AMET and AUCTCA values equal to the predicted mice AMET and AUCTCA values that correspond to liver cancer risks of 1 in 1 million. For the dose-metrics, AMET and AUCTCA, the TCE concentrations in air were 10.0 and 0.1 ppb TCE (continuous exposure), respectively, and in water, 7 and 4 μg TCE/L, respectively.     

Assessment of the Dose–Response Relationship Between Folate Exposure and Cognitive Impairment: Synthesizing Data from Documented Studies

The dose–response relationship between folate levels and cognitive impairment among individuals with vitamin B12 deficiency is an essential component of a risk-benefit analysis approach to regulatory and policy recommendations regarding folic acid fortification. Epidemiological studies provide data that are potentially useful for addressing this research question, but the lack of analysis and reporting of data in a manner suitable for dose–response purposes hinders the application of the traditional evidence synthesis process. This study aimed to estimate a quantitative dose–response relationship between folate exposure and the risk of cognitive impairment among older adults with vitamin B12 deficiency using “probabilistic meta-analysis,” a novel approach for synthesizing data from observational studies. Second-order multistage regression was identified as the best-fit model for the association between the probability of cognitive impairment and serum folate levels based on data generated by randomly sampling probabilistic distributions with parameters estimated based on summarized information reported in relevant publications. The findings indicate a “J-shape” effect of serum folate levels on the occurrence of cognitive impairment. In particular, an excessive level of folate exposure is predicted to be associated with a higher risk of cognitive impairment, albeit with greater uncertainty than the association between low folate exposure and cognitive impairment. This study directly contributes to the development of a practical solution to synthesize observational evidence for dose–response assessment purposes, which will help strengthen future nutritional risk assessments for the purpose of informing decisions on nutrient fortification in food.     

氨基酸亲-疏水性及分子大小使用偏好的统计分析

据GeneBank91资料库,对氨基酸的亲-疏水性及分子大小的使用偏好进行 了统计分析,发现它们与蛋白质的结构及折叠密切相关,同时分析了癌基因的三个 家族,并与普通序列进行了对比.     

以磷酸铁盐为催化剂:乳酸氧化脱氢制丙酮酸

用磷酸铁盐作催化剂气相催化氧化乳酸 ,乳酸选择性地转化为丙酮酸 ,收率可达到50 % ,同时对反应过程中影响丙酮酸形成的一些因素也进行了探讨     

赤霉素和脱落酸在植物生长发育中相互关系的研究进展

脱落酸和赤霉素是两种重要的植物激素,脱落酸和赤霉素之间的相互关系是调节多种生理活动的关键因素。在最近的研究中,研究者们发现ABA会引起两种质子泵基因HVP1和HvVHA-A表达的增加,而GA会抑制质子泵的活性。基因FUSCA3是调节植物叶器官形成的重要基因,高水平的脱落酸和低水平的赤霉素都会使FUSCA3蛋白的稳定性增加,反过来,FUSCA3的表达又会通过调节脱落酸和赤霉素的合成来影响叶的形成。在细胞凋亡、自然休眠和水淹植物的偏上生长现象中,ABA、GA的动态平衡发挥重要作用,相互拮抗着对方的作用。此外,已发现了一种赤霉素受体GID1和两种不同的脱落酸受体FCA和CHLH,它们对不同的基本生理过程是必不可少的。     

混酸溶液中有关离子浓度计算的简便公式

给出了混酸溶液中有关离子浓度计算的简便公式 ,并用该公式计算了氢氟酸和醋酸混合液的氢离子浓度和pH值 ,结果与实验值对照基本吻合     

核黄素、烟酸对烟草抗赤星病诱导的交互作用

用核黄素、烟酸单独或二者组合分别诱导烟草植株,１６ｈ提取总ＲＮＡ,用５种防卫基因的ｃＤＮＡ探针作印迹杂交．结果表明,病程相关蛋白ＰＲ－ｌａ在４种处理中均表现出转录活性增强,其中以核黄素诱导效应最好．几丁质酶（ＣＨＴ）、查尔酮合成酶（ＣＨＳ）及脂氧合酶（ＬＯＸ）基因的表现为：受核黄素、烟酸／核黄素诱导后活性略有增强,而受烟酸、核黄素／烟酸诱导后活性下降．苯丙氨酸氨裂解酶（ＰＡＬ）基因在４种处理中都不能被激活．ＰＡＧＥ电泳显示,ＰＲ－ｌａ和ＣＨＴ积累与基因转录活性相一致;ＰＲ蛋白积累动态又与诱导抗性发生动态呈先后关系,抗病性最大期比蛋白质积累的最高期晚３天;烟草基因组ＤＮＡ的随机引物扩增（ＲＡＰＤ）检测结果指出,除烟酸单独诱导在引物２中扩增出两种产物外,其他处理都不能诱导烟草ＤＮＡ分子结构发生变化．     

稀土固体超强酸SO4^2-／TiO2／La^3＋催化合成丙酸环己酯

研究了以稀土固体超强酸为催化剂,丙酸和环己醇为原料合成丙酸环己酯,并考察了影响反应的因素。结果表明：环己醇与丙酸物质的量之比为3：1,催化剂用量为1．4g（丙酸用量0．1mol）,带水剂为甲苯,用量为2mL,反应时间3．0h时,反应效果最佳,其酯化率可达90．9％。     

葡萄糖酸制备方法研究评述

葡萄糖酸及其衍生物是一类重要的有机化工产品．本文讨论了葡萄糖氧化制葡萄糖酸的各种氧化方法,同时强调多相催化氧化法在工业化生产中具有较大的应用潜力     

苯甲酸水溶液最大吸收峰波长刍议

通过实验测试出苯甲酸水溶液最大吸收峰 (λmax)波长小于 2 3 0nm ,并对结果从实验和理论两方面加以分析