Neurochemical and electrophysiological diagnosis of reversible neurotoxicity in earthworms exposed to sublethal concentrations of CL-20

Background, aim, and scope

Hexanitrohexaazaisowurtzitane (CL-20) is a relatively new energetic compound sharing some degree of structural similarity with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a known neurotoxic compound. Previously, we demonstrated using a noninvasive electrophysiological technique that CL-20 was a more potent neurotoxicant than RDX to the earthworm Eisenia fetida. In the present study, we investigated the effect of CL-20 exposure and subsequent recovery on muscarinic acetylcholine receptors (mAChRs) to further define the mechanism of reversible neurotoxicity of CL-20 in E. fetida.

Materials and methods

We used a noninvasive electrophysiological technique to evaluate neurotoxicity in CL-20-treated worms, and then measured how such exposures altered levels of whole-body mAChR in the same animals.

Results and discussion

A good correlation exists between these two types of endpoints. Effect on mAChR levels was most prominent at day 6 of exposure. After 7 days of recovery, both conduction velocity and mAChR were significantly restored. Our results show that sublethal concentrations of CL-20 significantly reduced mAChR levels in a concentration- and duration-dependent manner, which was accompanied with significant decreases in the conduction velocity of the medial and lateral giant nerve fibers. After 7-day post exposure recovery, worms restored both neurochemical (mAChR) and neurophysiological (conduction velocity) endpoints that were reduced during 6-day exposures to CL-20 concentrations from 0.02 to 0.22 µg/cm².

Conclusions and perspectives

Our findings support the idea that CL-20 induced neurotoxic effects are reversible, and suggest that CL-20 neurotoxicity may be mediated through the cholinergic system. Future studies will investigate other neurotransmission systems such as GABA, glutamate, and monoamine. Ion channels in the nerve membrane should be examined to further define the precise mechanisms underlying CL-20 neurotoxicity.     

鸡、猪粪便源大肠杆菌对4种抗生素耐药性的比较

以琼脂稀释法对67株鸡源大肠杆菌及61株猪源大肠杆菌进行最低抑菌浓度(MIC)测定,并以SPSS分别进行卡方检验和Probit模型估算,分析不同来源大肠杆菌耐药差异显著性及不同抗生素的半数抑菌浓度(MIC50),以期对不同畜禽粪便来源的大肠杆菌耐药差异进行详细准确的探讨。结果显示,鸡源大肠杆菌对头孢噻肟、诺氟沙星、环丙沙星和四环素耐药率分别为98.51%、68.66%、56.72%和100%,猪源大肠杆菌对头孢噻肟耐药率为88.52%,对诺氟沙星、环丙沙星和四环素则100%耐药。除四环素,鸡源、猪源大肠杆菌对诺氟沙星、环丙沙星、头孢噻肟的耐受差异显著(P0.05),51%的鸡源大肠杆菌和89%的猪源大肠杆菌均呈4重耐药。SPSS分析结果表明,Probit模型估算结果优于当前MIC50常规计算方法,头孢噻肟、诺氟沙星、环丙沙星和四环素对鸡源大肠杆菌MIC50分别为40.031μg·m L~(-1)、40.020μg·m L~(-1)、2.683μg·m L~(-1)和101.418μg·m L~(-1),对猪源大肠杆菌MIC50分别为8.724μg·m L~(-1)、56.044μg·m L~(-1)、31.214μg·m L~(-1)和130.915μg·m L~(-1)。回归方程显示环丙沙星对鸡源大肠杆菌抑制作用最强;高于40.031μg·m L~(-1)时,诺氟沙星抗菌作用弱于头孢噻肟,低于120.23μg·m L~(-1)时,诺氟沙星抗菌作用强于四环素;头孢噻肟、环丙沙星、诺氟沙星和四环素对猪源大肠杆菌的抑菌作用则呈递减趋势。同时验证了诺氟沙星和环丙沙星属同种作用机制,基于Probit模型计算更简单、快速、直观。研究结果可为畜禽养殖中大肠杆菌的耐药差异监控提供一定的数据基础。     

青藏高原纳木错流域持久性有机污染物的多介质迁移与归趋模拟

南亚排放的持久性有机污染物(POPs)可随大气传输到青藏高原,然而POPs在高原多介质间的迁移与分配尚不清晰。本研究利用三级逸度模型对4种POPs(六六六α-HCH,滴滴涕p,p'-DDT,菲Phe和苯并芘Ba P)在纳木错流域的迁移与归趋进行了模拟。结果表明,大气沉降是该区域污染物的主要输入过程,而降解损失则是主要的输出途径。就最终归趋而言,土壤是POPs在纳木错流域的重要储库,其存储了大于50%的POPs。此外,湖水和沉积物分别对α-HCH和PAHs具有较强的存储能力。灵敏度分析的结果表明,环境温度、大气中POPs的浓度及其理化性质是影响POPs在环境中分布的关键参数。本研究明确了纳木错流域不同POPs的迁移方向和归趋特征,这将为青藏高原生态安全评估提供科学依据。     

柴油机微粒捕集器复合再生性能及其场协同分析

基于柴油机微粒捕集器瞬态复合再生机理,建立了CFD三维仿真模型,并利用漩涡破碎燃烧模型和场协同数学模型对柴油机微粒捕集器瞬态复合再生过程的速度矢量和温度梯度进行了数值模拟和场协同分析,结果表明,再生时间为175 s时的微粒捕集器过滤体后端壁面峰值温度达到1 184 K,且其过滤体内速度矢量和温度梯度的协同度最好,最优燃烧再生区域所占最大比值为0.58,表明此时微粒捕集器过滤体内再生燃烧速率最大,其再生效率最高。     

无机离子对石墨烯/TiO2纳米管阵列光电极光催化性能影响

采用原位阳极氧化法制备二氧化钛纳米管阵列(TNAs)光电极,并采用电沉积工艺对其进行石墨烯修饰。以罗丹明B(Rh.B)为目标污染物,考察了染料溶液中主要无机离子对光电极光催化降解Rh.B的影响。实验结果表明,150W氙灯照射1 h,石墨烯/TNAs对Rh.B光催化降解率达到75%,是TNAs光电极的1.45倍。溶液中NO-3,Ca2+和Mg2+促进光电极对Rh.B的光催化降解,而SO2-4,Cl-和F-则会抑制对Rh.B的降解。     

生活垃圾和玉米秆混合热解动力学及产物分布

为探讨生活垃圾和玉米秆共热解过程中的协同关系和产物分布,采用热重分析仪对生活垃圾、玉米秆及其混合物进行了热解实验研究,并进行动力学计算。结果表明,混合热解可分为脱水、热解、炭化、焦催化气化4个阶段,前3个阶段与单独热解过程类似,第4个阶段与单独热解相比失重明显增加,表明混合热解过程中存在协同效应;混合物热解的实际活化能为28.492 k J/mol,低于单独热解及其混合物热解理论活化能,可见混合热解利于热解反应进行。为明晰混合热解对热解反应的促进作用,利用固定床热解实验,研究了混合比例对产物产率和热解气各组分产率的影响。结果表明,在不同混合比例下,固液实际产率低于理论值,而气体实际产率则比理论值高;混合物料热解气中H2、CH4、CO2产量均高于其理论值,而CO产量却相反,低于其理论值。     

森林凋落物研究现状及我国西南喀斯特地区研究展望

近几十年来,我国西南喀斯特地区生态环境退化严重,石漠化面积迅速扩大,林地覆盖率急剧下降,成为制约我国西部大开发生态建设中不可回避的重要科学问题,严重影响了西南地区社会、经济的可持续发展。喀斯特地区土层薄且侵蚀严重,土壤中的有机碳和营养盐主要来自地表枯枝落叶层的分解及累积。在气候变暖、陆地生态系统土壤温度升高、土壤有机碳急速流失和土壤质量退化的背景下,分析不同林下凋落物量和降解动态以及土壤有机碳库积累差异,揭示西南喀斯特地区不同林地凋落物归还量及其对土壤碳库积累的贡献具有极其重要的意义,将为喀斯特地区林地恢复重建和石漠化遏制工作提供科研依据。     

Day-to-Day Particulate Exposures and Health Changes in Los Angeles Area Residents with Severe Lung Disease

ABSTRACT

We measured particulate matter (PM_2.5 and PM₁₀) exposures, home temperature, arterial blood oxygen saturation, blood pressure, and lung function in 30 volunteer Los Angeles area residents during four-day intervals. Continuous Holter electrocardiograms were recorded in a subgroup on the first two days. Subjects recorded symptoms and time-activity patterns in diaries during monitoring, and during a reference period one week earlier/later. All subjects had severe chronic obstructive pulmonary disease. PM₁₀ (24-hr mean) at monitoring stations near subjects’ homes averaged 33 μg/m³, and ranged from 9 to 84 μpg/m³. In longitudinal analyses, day-to-day changes in PM_2.5 and PM₁₀ outside subjects’ homes significantly tracked concurrent station PM10 (r² = 0.22 and 0.44, respectively). Indoor and personal concentrations were less related to station readings (r² ≤ 0.1), but tracked each other (r² ≥ 0.4). In-home temperatures tracked outdoor temperatures more for lows (r² = 0.27) than for highs (r² = 0.10). These longitudinal relationships of subject-oriented and station PM measurements were generally similar to cross-sectional relationships observed previously in similar subjects. Among health measurements, only blood pressure showed reasonably consistent unfavorable longitudinal associations with particulates, more with station or outdoor PM than with indoor or personal PM.     

Replacing monocultures with mixed-species stands: Ecosystem service implications of two production forest alternatives in Sweden

Whereas there is evidence that mixed-species approaches to production forestry in general can provide positive outcomes relative to monocultures, it is less clear to what extent multiple benefits can be derived from specific mixed-species alternatives. To provide such insights requires evaluations of an encompassing suite of ecosystem services, biodiversity, and forest management considerations provided by specific mixtures and monocultures within a region. Here, we conduct such an assessment in Sweden by contrasting even-aged Norway spruce (Picea abies)-dominated stands, with mixed-species stands of spruce and birch (Betula pendula or B. pubescens), or spruce and Scots pine (Pinus sylvestris). By synthesizing the available evidence, we identify positive outcomes from mixtures including increased biodiversity, water quality, esthetic and recreational values, as well as reduced stand vulnerability to pest and pathogen damage. However, some uncertainties and risks were projected to increase, highlighting the importance of conducting comprehensive interdisciplinary evaluations when assessing the pros and cons of mixtures.