北京西山不同海拔油松林PM2.5浓度及叶片吸附量变化规律

以北京西山不同海拔梯度油松人工林为研究对象,对油松林PM_(2.5)浓度变化和叶片PM_(2.5)吸附量进行分析,并应用电子显微镜对不同海拔油松叶表面微形态特征进行观察,阐释叶片吸附PM_(2.5)差异。结果表明:随着海拔升高PM_(2.5)质量浓度逐渐降低,不同海拔油松林PM_(2.5)质量浓度日变化均呈典型的双峰曲线,7:00和19:00是一天的两个峰值,最小值出现在13:00—15:00左右;从不同月份看,不同海拔油松林PM_(2.5)质量浓度最高值出现在冬季的2月,最低值在8月;不同海拔油松林PM_(2.5)质量浓度全年均值为84 m((102.28±18.44)μg/m~3)110 m((94.18±18.34)μg/m~3)160 m((81.53±19.23)μg/m~3)230 m((75.39±15.71)μg/m~3);随着海拔升高单位叶面积PM_(2.5)吸附量逐渐减小,每升高50 m,单位叶面积PM_(2.5)吸附量降低23.25%,每公顷PM_(2.5)吸附量下降26.43%,不同海拔油松林每公顷PM_(2.5)吸附量全年均值为84 m((8.61±1.08)kg/hm~2)110 m((7.30±0.94)kg/hm~2)160 m((6.35±0.99)kg/hm~2)230 m((4.34±1.14)kg/hm~2);处于低海拔的油松叶表面较粗糙,气孔内部和周围聚集大量颗粒物,在叶面形态上更有利于吸附PM_(2.5),高海拔则相反。高海拔空气质量优于低海拔,低海拔的植物吸附颗粒物多于高海拔。研究结果可为城市造林和森林净化大气提供数据支持。     

城市规模对大气污染物NO2和PM2.5浓度的影响

随着我国城市的快速发展,城市的区域性大气污染问题日益突出,尤其是大城市和超大城市的污染问题更加严重。那么城市规模的扩大是否必然导致空气污染的加剧?控制城市人口规模是否是防治空气污染的有效手段?这些问题成为空气污染防治中政府、公众和学者广泛关注的焦点。采用2013年冬季全国114个重点城市两种典型大气污染物-NO_2(传统)和PM_(2.5)(新型)-浓度的实时监测数据,首先分析了这两种大气污染物的空间分布特征,进而定量分析城市人口规模和大气污染物浓度的关系。结果显示:(1)仅有21%的城市NO_2浓度达到WHO的城市年均浓度标准(40μg/m~3),全部城市的PM_(2.5)浓度高于WHO年均浓度标准(10μg/m~3);(2)大气污染物的空间分布具有显著的集聚特征和区域性特征,表现为:NO_2呈较为分散的空间分布,而PM_(2.5)的空间分布呈现"北高南低、内陆高沿海低"的特征。NO_2浓度高的区域主要分布在天津、河北东南部和山东中部地区,PM_(2.5)浓度高的区域主要分布于河北西南部和山东西部;(3)常住人口规模同冬季NO_2和PM_(2.5)浓度呈倒"U"型关系;在1000到1200万的城市冬季平均NO_2和PM_(2.5)浓度最高(NO_2:69.28μg/m~3,PM_(2.5):119.58μg/m~3)。(4)总人口低于1200万的城市,冬季NO_2浓度和PM_(2.5)浓度随着城市规模增加而显著升高(NO_2:r=0.44,P0.01;PM_(2.5):r=0.43,P0.01);总人口高于1200万的城市,NO_2浓度同城市规模呈显著负相关关系(r=0.91,P0.05),PM_(2.5)浓度随城市规模增加逐渐降低。(5)常住人口密度在1000人/km~2以下的重点城市,NO_2和PM_(2.5)浓度同城市人口密度呈显著正相关关系(NO_2:r=0.23,P0.05;PM_(2.5):r=0.36,P0.01)。常住人口密度在1000人/km~2以上的城市人口密度同NO_2和PM_(2.5)浓度呈显著负相关关系(NO_2:r=-0.61,P0.05;PM_(2.5):r=0.63,P0.01)。以上研究结果可以为划定不同大气污染物的重点防治区域和制定联合防治行动计划提供理论依据,并为重点城市大气污染治理和城市人口规模控制理论完善提供参考。     

张家口市大气颗粒物PM2.5、PM10浓度与慢性阻塞性肺疾病住院人次的关系研究

目的:研究张家口市大气颗粒物对慢性阻塞性肺疾病(COPD)的影响,并分析大气颗粒物对不同特征人群的影响。方法:从张家口市医保办公室获取张家口市2013年1月1日-2015年12月31日两家三甲医院COPD患者的住院病历资料,从中国环境监测总站网站获取大气污染物的监测数据,从张家口市气象局获取气象资料。建立广义相加模型(GAM),在控制长期趋势、星期几效应和温湿度影响后,应用条件Logitic回归方法评估PM_(2.5)、PM_(10)对COPD住院人次的影响。根据患者不同特征(性别、年龄、季节)进行分层分析,评估颗粒物污染的高危人群。结果:研究纳入两家三甲医院,共1984例住院COPD患者,其中男性患者1258例(63.4%)、女性患者726例(36.6%),≥75岁患者678例(34.2%),60~75岁患者936例(47.2%)、芨60岁患者370例(18.6%)。2013-2015年PM_(2.5)、PM_(10)年均浓度分别为[(36.54±20.34)μg/m~3、(84.37±52.54)μg/m~3],[(34.50±27.08)μg/m~3、(78.43±69.78)μg/m~3],[(32.04±21.35)μg/m~3、(75.46±50.02)μg/m~3],两者在移动平均滞后3d时,对COPD的影响最大,即PM_(2.5)每增加10μg/m~3,COPD住院人次增加1.90%(95%CI:1.002-1.033,P0.05),PM_(10)每增加10μg/m~3,COPD住院人次增加2.10%(95%CI:1.005-1.045,P0.05)。分层分析结果显示:PM_(2.5)、PM_(10)每升高10μg/m~3,女性COPD患者住院人次增加1.09%、1.14%,差异具有统计学意义(P0.05);≥75岁患者,COPD住院人次增加1.03%、0.99%,差异具有统计学意义(P0.05);而年龄芨60岁、60~75岁、男性以及季节分层分析中,PM_(2.5)、PM_(10)浓度与COPD住院人次无统计学意义(P0.05)。结论:颗粒物污染会增加COPD住院率,≥75岁的老年患者及女性患者更敏感。     

北京西山绿化树种PM2.5吸附量及叶表面AFM特征分析

以北京西山针阔叶树种(白皮松Pinus bungeana、油松Pinus tabulaeformis、柳树Salix babylonica、五角枫Acermono、银杏Ginkgo biloba、杨树Populus spp.)为研究对象,应用气溶胶再发生器测定植物叶片夏秋季PM_(2.5)吸附量,同时用原子力显微镜(AFM)观察叶表面微形态特征,并分析叶表面粗糙度等参数,探讨树种叶表面特征与其PM_(2.5)吸附能力间的相关性。结果表明:针叶树种年均单位叶面积PM_(2.5)吸附量(1.70μg/cm~2)阔叶树种(0.48μg/cm~2);各树种年均单位叶面积PM_(2.5)吸附量大小排序为白皮松(1.71μg/cm~2)油松(1.67μg/cm~2)柳树(0.54μg/cm~2)五角枫(0.51μg/cm~2)银杏(0.47μg/cm~2)杨树(0.39μg/cm~2)。针叶树种单位叶面积PM_(2.5)吸附量季节变化趋势为冬(2.86μg/cm~2)春(1.39μg/cm~2)秋(1.13μg/cm~2)夏(0.96μg/cm~2);而阔叶树种则是秋(0.56μg/cm~2)夏(0.55μg/cm~2)春(0.015μg/cm~2)。叶片粗糙度与单位叶面积PM_(2.5)吸附量呈显著线性正相关(P0.01),其中,针叶树种吸附PM_(2.5)能力受粗糙度影响较明显。北京作为国际化大都市,大气环境PM_(2.5)污染趋于严重。因此,分析了北京西山典型针阔叶树种PM_(2.5)吸附量的季节差异及其影响因素,探讨各树种叶片吸附PM_(2.5)机理,根据各树种吸附PM_(2.5)特征及其与叶表面形态的关系,对针阔叶树种进行合理配置,充分发挥城市绿地系统的生态服务功能,为城市绿化树种的科学选择提供参考。     

北京西山典型城市森林内PM_(2.5)动态变化规律

城市森林内PM2.5浓度的状况可以直接反映城市森林对PM2.5的净化效果,也是居民休闲游憩关心的森林环境问题。选择北京西山3种典型的游憩型城市森林,通过对林内PM2.5浓度一年四季昼夜24h内变化的同步观测,分析了不同类型城市森林内PM2.5浓度的季节变化、日变化以及影响因素,结果表明:(1)北京西山3种游憩林内PM2.5浓度多数时候远低于城区对照值,在春、夏、秋三季都达到了国家城市化地区的标准,甚至在春季、秋季还达到了国家一类地区的标准。(2)城市森林在不同季节对PM2.5的净化效果存在差异,林内PM2.5浓度总体上呈现冬季夏季秋季春季的规律。(3)林内PM2.5浓度在一天24h内有很大变化波动,夜间浓度总体上高于白天,日变化曲线近似呈"双峰双谷"型,两个高峰出现在夜晚和早上,两个低谷出现在凌晨和中午前后。一年四季白天低谷出现时间有所不同,春季15:00左右、夏季13:00—17:00、秋季13:00—15:00、冬季9:00—11:00。(4)PM2.5在不同类型游憩林内的变化趋势和浓度值存在一定差异。郁闭度较大的侧柏林夜间PM2.5浓度总体上高于其它两种林型,其高峰和低谷出现时间延迟,高峰值大,高峰期持续时间长,且这种规律在秋季表现得更明显。(5)基于上述研究认为,北京西山城市森林为居民在PM2.5污染比较突出的都市背景下提供了一个相对清洁、健康的森林游憩环境,春季、夏季、秋季全天以及冬季9:00—11:00均是森林中PM2.5状况健康而适宜外出游憩的时段。     

北京山区典型暖温带落叶阔叶林大气CO_2浓度、草本层光合作用及土壤释放CO_2变化特点(英文)

为探讨森林生态系统植被、土壤等不同组分与大气CO_2交换特点,利用中型同化箱(40cm×40cm×2Ocm)及红外CO_2分析仪装置对北京山区典型暖温带森林生态系统辽东栎(Quercus liaotungensisKoidz.)林草本层净光合作用、土壤释放CO_2及林外(高出林冠2m)与林内(低于林冠2m)大气CO_2变化进行测定。结果表明:夏季及秋季大气CO_2浓度分别为(323±10)μmol·mol~(-1)和(330±1)μmol·mol~(-1);在一天内连续24h的测定中,大气与林内CO_2浓度的差值最大时可分别达-46和-61μmol·mol~(-1)。夏季草本层净光合强度为(2.59±1.05)μmol CO_2·m~(-2)·s~(-1),是秋季((1.31±0.39)μmol CO_2·m~(-2)·s~(-1))的2倍;夏季土壤呼吸释放CO_2的强度明显高于秋季,分别为(5.18±0.75)μmol CO_2·m~(-2)·s~(-1)和(1.96±0.57)μmol CO_2·m~(-2)·s~(-1)。土壤释放CO_2强度与地面温度之间存在显著相关,其关系式为Y=-0.8642 0.3101X(r=0.7164,P<0.001,n=117)。大气CO_2浓度的低值及草本层光合强度高值约出现在14:00左右;而在夜间土壤释放CO_2强度增加,表现为大气CO_2浓度升高。     

降雨对北方城市5种典型城市绿化树种叶面滞尘的影响

城市树木和森林植被净化大气颗粒污染物的功能受到了广泛的重视,但由于受多种植被特征与环境因素的影响,定量评价城市植被净化大气颗粒污染物功能非常困难。研究了不同降雨条件下大叶黄杨、银杏、栾树、五角枫、杜仲5种我国北方城市绿化典型树种叶面滞尘量的变化特征。在选定的样树冠层分上、中、下3层和东、南、西、北4个方向,采集成熟叶片,采用刷洗样本叶表,抽取水样及分级抽滤并烘干称重的方法,测定这5种树种降雨后12d(夏季累积滞尘量)、14mm降雨后(小雨)、29mm降雨后(中雨)以及室内模拟降雨30mm/h(15mm雨量)后叶片表面不同粒径大气颗粒污染物的滞留量。研究结果表明:降雨对不同粒径颗粒物去除能力有较大差异,除银杏以外,PM10以上颗粒物更容易去除;小雨对颗粒物的冲刷能力有限;中雨可以冲刷掉50%以上总颗粒物;室内模拟强降雨可以冲刷掉90%以上颗粒物,随着降雨增大,各粒径颗粒物随之冲刷量增加;同时叶表结构对抗冲刷能力有显著影响,革质叶片更容易滞尘及冲刷,绒毛结构滞尘能力较低,抗冲刷能力较强;北方大叶黄杨具有综合去除空气中颗粒物优势(小雨TSP冲刷量为(775.06±33.99)mg/m~2),银杏具有去除细颗粒物优势(中雨PM_(2.5)冲刷量为(426.55±40.83.99)mg/m~2)。     

基于ENVI-met的城市道路绿地植物配置对PM2.5的影响研究

随着城市化的快速发展,大气污染尤其细颗粒物(PM_(2.5))已成为制约城市环境的重要因素,相关研究表明,在众多的PM_(2.5)来源中道路交通是在其中的重要来源之一,而道路绿地植物群落能够消减来自道路的PM_(2.5)。运用场地观测和ENVI-met模拟相结合的方法探讨城市道路绿地植物群落对PM_(2.5)的影响,分析仅有乔木(i)、乔木+树篱(ii)、乔木+树篱+灌木(iii)3种模式下的植物群落配置对PM_(2.5)的影响,揭示绿地植物群落的长度、宽度、高度和LAI对PM_(2.5)的影响。结果表明:(1)场地观测中的道路绿地植物群落的3种配置模式对PM_(2.5)的消减率分别是iii(14.2%)ii(12.9%)i(9.2%)。(2)绿地中植物的种类、绿地宽度、绿地植物的叶面指数等要素对消减作用起正面作用,高度和长度起负面作用。(3)绿地的长度的一定量的减少可以在绿地后方形成一个宽度约为绿地长度80%的、随着与绿地的距离的增加而宽度递减的较绿地长度更长环境PM_(2.5)浓度更低的低谷区,但其他没有绿地的空间的PM_(2.5)浓度会加重。(4)绿地高度的增加会迫使PM_(2.5)向更高的空间运动。     

冬季PM2.5的气象影响因素解析

气象因素能够显著影响PM_(2.5)浓度,可减轻或加剧城市空气污染,尤其是在雾霾严重的冬季。同时由于城市间污染物排放强度和扩散条件的差异,雾霾的发生往往具有较强的区域性。选择了石家庄、西安、北京、太原、广州5个不同污染区域的典型城市,首先分析多个气象因子与PM_(2.5)浓度的关系,进而研究气象因素对PM_(2.5)浓度变异解释度的差异,以及气象因子对PM_(2.5)浓度影响的相对重要性,进一步对比分析气象因素对PM_(2.5)浓度影响在不同污染程度的城市之间的差异,解析了不同城市的主要气象影响因素和气象因素的综合影响程度。研究结果表明:(1)气象条件与PM_(2.5)日浓度显著相关,且在不同污染程度的城市与PM_(2.5)浓度相关的气象因子不同。与石家庄冬季PM_(2.5)浓度相关的气象因素为相对湿度、平均风速;与西安PM_(2.5)浓度相关的主要气象因素为相对湿度、平均风速和最大持续风速;与北京PM_(2.5)浓度相关的主要气象因素相对湿度、日均温度、平均风速、最大持续风速和最低温;与太原PM_(2.5)浓度相关的主要气象因素为日均温、相对湿度、平均风速、最高温、最低温和最大持续风速;与广州PM_(2.5)浓度相关的主要气象因素为相对湿度、平均风速、最高温和降雨量。(2)PM_(2.5)浓度越高的地区,气象因素能够解释的PM_(2.5)浓度变异越小。严重污染区的石家庄气象因素多元回归分析的R~2为0.27,重污染区的西安气象因素多元回归分析R~2为0.29,中污染区的北京气象因素多元回归分析R~2为0.46,污染地区的太原气象因素多元回归分析R~2为0.67。研究结果揭示了不同城市的主要气象影响因素及其综合影响程度,可为城市PM_(2.5)控制和预测精度提高提供理论参考,并为区域生态环境规划和城市协调发展提供科学依据。     

贵州某燃煤电厂周边春季大气颗粒物的汞污染特征

为分析燃煤电厂周边不同粒径大气颗粒物及其中汞的污染特征,于2017年春季对贵州某燃煤电厂周边TSP、PM_(10)、PM_(2.5)进行样品采集,应用冷原子荧光汞分析仪对颗粒物中汞的浓度进行测定。结果表明:TSP、PM_(10)、PM_(2.5)的体积浓度范围分别为83.7~162、65.2~130、43.6~87.1μg·m-3,超标率分别为0、5.63%、25.7%。汞的体积浓度(Cv(Hg))分别为68.5~102、58.9~84.9、51.4~80.9 pg·m~(-3);汞的质量浓度(Cm(Hg))分别为571~810、627~913、693~1083 ng·g~(-1);从空间分布看,上风向颗粒物样品中汞浓度低于下风向,主导风向高于非主导风向,主要受当地风向和采样点位置影响。汞在颗粒物中的PM_(2.5)/PM_(10)和PM_(10)/TSP值分别为67.5%~95.2%、83.1%~98.8%,明显高于其相应的颗粒物质量浓度比值,表明汞主要在细颗粒物中富集。     

Altitudinal Changes in Photosynthetic Pathways of Floristic Elements in Southern Sinai, Egypt

High altitude profoundly influenced plant diversity and distribution on mountains of southern Sinai (Egypt). Plants exhibiting the C₃-mode of photosynthesis were widely distributed along the altitudinal transect. Plants exhibiting the C₄-mode were restricted below an altitude of about 1400 m above sea level. The transition from C₃-dominated areas to C₄-dominated areas occurred between 1200 and 1400 m a.s.l. This revised version was published online in August 2006 with corrections to the Cover Date.     

Magnesium uptake kinetics in loblolly pine seedlings

Recent studies have suggested that the growth of loblolly pine (Pinus taeda L.) has declined in the southern United States and it has been hypothesized that foliar Mg deficiency may play an important role in the perceived decline. Quantitative nutrient uptake models such as the Barber-Cushman model have been used successfully to investigate nutrient uptake by crop species under a variety of field and experimental conditions and may provide one approach to evaluating this question. However, in order to use this approach it is necessary to develop, for the plant species and nutrient of interest, values for maximal nutrient influx rate at high solution concentrations (I_max), the solution concentration where net influx is 0.5 I_max (K_m), and the nutrient concentration below which influx ceases (C_min). As a first step in evaluating the potential of such an approach, two sets of experiments using established solution nutrient depletion techniques were used to define these values for loblolly pine seedlings 180, 240, 365, and 425 days in age. Observed I_max values for Mg range from 7.90E-8 to 1.29E-7 mol cm^–2 s^–1 with younger seedlings having higher values. Values of K_m for all seedling ages were quite similar ranging from 8.69 to 8.58E-3 mol cm^–3. Most importantly, the results of both experiments indicate that during a growth flush, seedlings will withdraw Mg from solution until the concentration is essentially zero (C_min=0). During non-flush periods uptake rates appear to be greatly reduced. Therefore, efforts to model Mg uptake will need to take these differences as well as seedling age influences into consideration.     

Unambiguous through-bond sugar-to-base correlations for purines in 13C, 15N-labeled nucleic acids: The HsCsNb,HsCs(N)bCb,and HbNbCb experiments

Summary A set of three 3D (¹H, ¹³C, ¹⁵N) triple-resonance correlation experiments has been designed to provide H1-H8 intraresidue sugar-to-base correlations in purines in an unambiguous and efficient manner. Together, the H_sC_sN_b, H_sC_s(N)_bC_b, and H_bN_bC_b experiments correlate the H1 sugar proton to the H8 proton of the attached base by means of the {H1, C1, N9, C8, H8} heteronuclear scalar coupling network. The assignment strategy presented here allows for unambiguous H1-H8 intraresidue correlations, provided that no two purines have both the same H1 and C1 chemical shifts and the same C8 and N9 chemical shifts. These experiments have yielded H1-H8 intraresidue sugar-to-base correlations for all five guanosines in the [¹³C, ¹⁵N] isotopically labeled RNA duplex r(GGCGCUUGCGUC)₂.     

Assessing the Impact of Advected African Dust on Air Quality and Health in the Eastern United States

Large quantities of African dust are carried into the southeastern United States each summer with concentrations typically in the range of 10 to 100?µg m^?3. Because approximately one-third to one-half of the dust mass is in the size range under 2.5?µm diameter, the advection of African dust has implications for the EPA's newly implemented standard for PM_2.5 particulate matter and for the assessment of human health effects. It will be difficult to assess the impact of African dust events on air quality because they occur during the summer (maximum in July) when photochemical pollution events are frequent and intense in the eastern United States. Indeed, the presence of dust could affect the evolution of photochemical dust events. In order to assess the role of African dust in air quality in the United States, it will be necessary to develop a set of diagnostic indicators; it appears that dust mineralogy and elemental composition might be useful for this purpose. Various satellite products can be used to characterize the spatial coverage of dust events and, when coupled with meteorological tools, to predict impact regions.     

八肽胆囊收缩素对大鼠大脑皮质细胞钙调素活性的影响

为了探讨胆囊收缩素(CCK)受体在中枢神经系统中的信号传递机制,观察了CCK₈和CCK_A受体拮抗剂L-364,718、CCK_B受体拮抗剂L-365,260对大鼠大脑皮质钙调素（CaM）活性的影响.结果表明：a.CCK₈对CaM活性的影响具有时间依赖性,15 min达到最高点后逐渐下降;b.CCK₈在10^－12～10^－7 mol/L范围内可刺激CaM活性的增加,超过10^－7 mol/L后,逐渐趋于饱和.c.CCK_A受体拮抗剂L-364,718、CCK_B受体拮抗剂L-365,260均可抑制10^－7 mol/L CCK₈引起的CaM活性的增加,但两者IC₅₀相差40倍,L-365,260在较低浓度时即能明显拮抗CCK₈引起的CaM活性变化.研究结果提示CCK₈可能通过CCK_B受体引起CaM活性变化,而CaM可能是CCK_B受体的重要信号传递机制之一.     

Differences in folate-protein interactions result in differing inhibition of native rat liver and recombinant glycine N-methyltransferase by 5-methyltetrahydrofolate

Glycine N-methyltransferase (GNMT) is a key regulatory enzyme in methyl group metabolism. In mammalian liver it reduces S-adenosylmethionine levels by using it to methylate glycine, producing N-methylglycine (sarcosine) and S-adenosylhomocysteine. GNMT is inhibited by binding two molecules of 5-methyltetrahydrofolate (mono- or polyglutamate forms) per tetramer of the active enzyme. Inhibition is sensitive to the status of the N-terminal valine of GNMT and to polyglutamation of the folate inhibitor. It is inhibited by pentaglutamate form more efficiently compared to monoglutamate form. The native rat liver GNMT contains an acetylated N-terminal valine and is inhibited much more efficiently compared to the recombinant protein expressed in E. coli where the N-terminus is not acetylated. In this work we used a protein crystallography approach to evaluate the structural basis for these differences. We show that in the folate-GNMT complexes with the native enzyme, two folate molecules establish three and four hydrogen bonds with the protein. In the folate-recombinant GNMT complex only one hydrogen bond is established. This difference results in more effective inhibition by folate of the native liver GNMT activity compared to the recombinant enzyme.     

Prostaglandin E2 produced by inducible COX-2 and mPGES-1 promoting cancer cell proliferation in vitro and in vivo

Aim

Many cancers originate and flourish in a prolonged inflammatory environment. Our aim is to understand the mechanisms of how the pathway of prostaglandin E₂ (PGE₂) biosynthesis and signaling can promote cancer growth in inflammatory environment at cellular and animal model levels.

Main methods

In this study, a chronic inflammation pathway was mimicked with a stable cell line that over-expressed a novel human enzyme consisting of cyclooxygenase isoform-2 (COX-2) linked to microsomal (PGE₂ synthase-1 (mPGES-1)) for the overproduction of pathogenic PGE₂. This PGE₂-producing cell line was co-cultured and co-implanted with three human cancer cell lines including prostate, lung, and colon cancers in vitro and in vivo, respectively.

Key findings

Increases in cell doubling rates for the three cancer cell types in the presence of the PGE₂-producing cell line were clearly observed. In addition, one of the four human PGE₂ subtype receptors, EP₁, was used as a model to identify PGE₂-signaling involved in promoting the cancer cell growth. This finding was further proven in vivo by co-implanting the PGE₂-producing cells line and the EP₁-positive cancer cells into the immune deficient mice, after that, it was observed that the PGE₂-producing cells promoted all three types of cancer formation in the mice.

Significance

This study clearly demonstrated that the human COX-2 linked to mPGES-1 is a pathway that, when mediated by the EP, is linked to promoting cancer growth in a chronic inflammatory environment. The identified pathway could be used as a novel target for developing and advancing anti-inflammation and anti-cancer interventions.     

Effect of Some Environmental Pollutants on the Superoxide Dismutase Activity in Lemna

Exposure of Lemma sp. to SO₂ resulted in an increased activity of superoxide dismutase. About 3 to 4 fold increase in the activity was observed within 30 minutes after the plants were fumigated with 10 ml/l of SO₂. Paraquat, a well known superoxide generator, doubled the enzyme activity after 1 hour of treatment with 0.1 mM paraquat. Superoxide dismutase activity was also enhanced by cadmium treatment but the response was not immediate. Optimum increase in the activity of enzyme was observed after 4 days of treatment with 40 mg/l of cadmium in the medium. Treatment with H₂O₂ very clearly inhibited the activity of superoxide dismutase in Lemna.     

Stereospecific synthesis of new steroidal isoxazoles in dry media

An easy and fast procedure was developed for one-pot synthesis of steroidal isoxazoles starting from 23-acetylsapogenins derivatives in presence of P₂O₅/SiO₂ in dry media under microwaves irradiation is described. Substrates of the 25S and 25R series were used as raw materials, establishing that this new methodology is applicable to both series.