小流域内植被类型对土壤NO3-/NH4+空间变化的影响

流域内植被类型、地形地貌特征对土壤氮循环过程有重要的作用,是影响下游水体无机氮素来源以及富营养化的关键因子。通过比较小流域内4种植被类型(落叶松人工林、油松人工林、天然阔叶次生林和农田(玉米))对土壤NO3--N和NH4+-N含量空间变化的影响,揭示流域内不同立地条件下水源涵养林与土壤无机氮变化特征之间的关系。结果表明:4种植被类型土壤NO3--N和NH4+-N含量差异显著(P<0.05);由坡上到坡下土壤NO3--N和NH4+-N含量显著降低;在土壤表层NO3--N和NH4+-N含量最高,随着土层深度增加无机氮含量减少;与水源涵养林天然植被和人工林植被相比,农田土壤NO3--N含量最高(11.86mg·kg-1),有较高的氮流失风险。     

不同氮素形态及水分胁迫对水稻苗期水分吸收、光合作用及生长的影响

采用室内营养液培养, 聚乙二醇(PEG6000)模拟水分胁迫处理、HgCl2抑制水通道蛋白活性的方法, 在3种供氮形态下(NH4+-N/ NO 3--N为100/0、50/50和0/100), 研究了水稻苗期水分吸收、光合及生长的状况。结果表明, 在非水分胁迫下, 水稻单位干重吸水量以单一供NO3--N处理最高, 加HgCl2抑制水通道蛋白活性后, 单一供NO3--N、NH4+-N和NH4+-N/ NO3--N为50/50处理的水稻水分吸收分别下降了9.6%、20.7%和16.0%; 但在水分胁迫下, 单一供NO3--N的处理水分吸收量显著降低, 低于其它2个处理, 加HgCl2抑制水通道蛋白活性后, 水分吸收量分别降低了1.0%、18.8%和23.5%。在2种水分条件(水分胁迫与非水分胁迫)下, 净光合速率、气孔导度、蒸腾速率和细胞间隙CO2浓度等指标均以单一供NH4+-N处理最大,NH4+-N/ NO3--N为50/50处理次之, 单一供NO3--N处理最小。HgCl2处理结果表明, 不同形态氮素营养能够影响水稻幼苗根系水通道蛋白活性。在2种水分条件下, NH4+-N/ NO3--N为50/50处理的生物量(干重)均最大。本研究为水稻苗期合理施肥以壮苗提供了理论依据。     

不同基因型水生植物对铵态氮和硝态氮吸收动力学特性研究

针对不同营养状况的富营养化水体修复而选择吸收养分效率较强的水生植物,采用改进常规耗竭法比较研究了6种不同基因型水生植物凤眼莲(Eichhornia crassipes Solms)、黄花水龙(Jussiaea stipulacea Ohwi)、再力花(Thalia dealbata Fraser)、美人蕉(Canna glauca L.)、水芹[Oenanthe javanica(Bl).DC]和豆瓣菜(Nasturtium officinaleR.Br.)对铵态氮和硝态氮吸收动力学特性。结果表明,不同基因型水生植物吸收铵态氮和硝态氮的动力学特性可用Michaelis-Menten方程来描述。在低浓度培养下,不同基因型水生植物对NH4+-N和NO3--N吸收的动力学参数Imax和Km差异较大,其吸收NH4+-N和NO3--N的Imax最大是水芹,其次是豆瓣菜;Km值最小的是水芹,其次是豆瓣菜;且水芹对NH4+-N和NO3--N不仅具有较强的亲和力,还具有较高的离子吸收速率。结果还表明,当介质中氮浓度较低时,水芹有优先吸收硝态氮的趋势,而豆瓣菜和再力花有优先吸收铵态氮的趋势。     

大型溞引导的沉水植被生态修复对滴水湖水质的净化效果

2007年4月-2008年1月,在滴水湖D港中段长950m(水量为10000m3)的修复区内投放大型溞(Daphnia magna),以滤除水华藻类等颗粒有机物,然后移栽伊乐藻、苦草、轮叶黒藻、光叶眼子菜和菹草等沉水植物,逐月监测水体中总氮(TN)、铵态氮(NH4+-N)、硝态氮(NO3--N)、亚硝态氮(NO2--N)、总磷(TP)、活性磷酸盐(PO43--P)和COD等水质指标,分析沉水植被栽培对滴水湖水体水质的净化效果.结果表明:试验期间,修复区水体TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P和COD显著低于对照区(P0.01),溶解氧(DO)增加了50.4%,水体透明度(SD)平均在3.4~3.7m,水质达到国家Ⅱ~Ⅲ类地表水水质标准;2008年3月应用已构建的沉水植被群落对富营养化流水水体水质进行净化试验,7d后修复区流水水体除BOD外,TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P和COD均显著降低(P0.01),DO增加了17.98%,SD提高了30cm.利用大型溞控藻后移栽沉水植物对滴水湖水体水质的净化效果十分显著.     

生物炭对黄壤中氮淋溶影响:室内土柱模拟

土壤氮素的淋失作用不仅造成土壤营养元素的损失,而且对河流和湖泊等环境水体的富营养化具有重要贡献.采用土柱室内模拟方法,通过模拟降雨淋滤,研究了生物炭对土壤淋溶液体积、pH和电导率以及NH4+-N和NO3--N淋溶的影响.试验中所用的生物炭是以桉树木屑为原料制成,分别按照炭土质量比1％、2％、4％、10％施用于土壤中.结果显示,与对照相比,向土壤添加10％、4％、2％、1％生物炭分别减少土壤水分损失14％、0.03％、0.02％和0.01％;随生物炭添加量增加,淋溶液的pH和电导率也逐渐增加;土壤生物炭添加量为10％、4％、2％时,NH4+-N淋溶量分别增加235％、28.1％、31.6％,NO3--N淋溶量分别增加4.2％、14.5％、25.6％;但生物炭添加量为1％的土柱NH4+-N淋溶量减少15.8％,NO3--N淋溶量减少19.2％.本研究表明,桉树生物炭对土壤氮淋溶与其施用量有关,1％施用量能减少氮淋溶,过量施用将增加氮淋溶,这种作用是否与生物炭种类有关有待进一步研究.     

不同氮素形态比例对五味子幼苗生长特性的影响

以2年生五味子苗木为试验材料,在田间条件下,施以铵态氮(NH4+-N)和硝态氮(NO3--N)不同比例,分析了叶片可溶性蛋白、叶绿素含量、根系及茎叶中全氮含量、生物量等季节的动态变化规律,探讨了不同氮素形态比例对五味子苗木生长的影响。结果表明,五味子苗木在不同生长时期对不同氮素形态的吸收和利用存在明显差异,NH4+-N和NO3--N对五味子幼苗生长有显著的联合效应。在五味子生长前期,五味子主要以吸收和同化NH4+-N为主,并以铵态氮和硝态氮比例为75∶25时地上部生物量积累较多;而在五味子生长的中后期,五味子主要以NO3--N吸收和同化为主,并以铵态氮和硝态氮比例为25∶75时地上部生物量积累较多。     

NH_4~+-N、TN、TP和DO对泥鳅的氧化损伤作用研究

目的:水体富营养化给渔业的发展造成严重的负面影响,成为全球瞩目的环境问题之一。方法:本研究利用泥鳅(Misgurnus anguillicaudatus)作为实验生物,选择氨氮(NH4+-N)、总氮(TN)、总磷(TP)和溶解氧(DO)含量作为富营养化水体的影响因素。研究富营养化水体中NH4+-N、TN、TP和DO含量对泥鳅抗氧化酶活性和脂质过氧化水平的影响,旨在阐明富营养化水体对鱼类的氧化损伤作用。结果:随着水体中NH4+-N、TN、TP和DO含量的增加,泥鳅的SOD活性显著降低(P0.05),MDA含量显著增加(P0.05)。与正常的DO水平相比,水中高浓度和低浓度的氧含量都会造成SOD活性的显著下降(P0.05)和MDA含量的显著上升(P0.05)。其中NH4+-N和DO的影响最大。结论:富营养化水体对鱼类的危害与其造成的鱼类氧化损伤有直接关系,实验的开展为富营养化水体的生物监测与评价具有一定指导作用。     

四种冬季水生植物组合对富营养化水体的净化效果

选择10种耐低温的水生植物构建4种植物组合,研究了冬季低温环境下不同水生植物组合对富营养化水体的净化效果.结果表明:组合1[常绿水生鸢尾(Iris hexagonus Hybrid)*羊蹄(Rumex japonicus)+金叶“金钱蒲”(Acorus gramineus“Ogan”)+反曲灯心草“蓝箭”(Juncus inflexus“Blue Arrows”)]4种植物均能在试验富营养化水体中茂盛生长,且对TN、NOx-N、NH4-N和TP的去除率分别为47.8％、52.2％、32.4％和70.1％;组合2[常绿水生鸢尾+羊蹄+金叶“金钱蒲”+大苞萱草(Hemerocallis middendorfii)]4种植物也都能在试验富营养化水体中存活,并且有一定量的生长,对TN、NOx-N、NH4-N和TP的去除率分别为44.2％、58.5％、34.6％和67.8％;而未种植物的对照对TN、NOx-N、NH4-N和TP的去除率分别为40.0％、25.9％、27.3％和64.5％;组合1和2对富营养化水体有较好的净化效果.组合3和组合4中由于吊兰(Chlorophytum comosum)和三穗薹草(Carex tristachya)等植物长势较差,仅对NOx-N具有较明显去除能力,对其他指标去除效果不明显.通过这些水生植物在富营养化水体中生长特性和对营养元素的去除能力,发现冬季组合1和2的净化效果较好,是低温条件下适宜的浮床植物组合形式.     

金鱼藻、环棱螺及其组合处理对水生附着生物含量和氮、磷浓度的影响

通过模拟试验,研究了金鱼藻(Ceratophyllum demersum)、梨形环棱螺(Bellamya pu-rificata)及其组合3种处理对水生附着生物干质量(附着生物干质量与底栖藻类Chl-a)、总氮(TN)、氨氮(NH4+-N)、硝酸盐氮(NO3--N和总磷(TP)的影响.结果表明:(1)金鱼藻对水生附着生物干重和Chl-a含量的增长率分别为295.62%(P<0.01)和32.31%(P<0.05),环棱螺对二者的去除率为65.69%(P<0.05)和46.19%(P<0.01),组合对二者的去除率为70.07%(P<0.05)和70.16%(P<0.01);(2)金鱼藻、环棱螺及其组合对TN的平均去除率分别为35.18%、15.27%和20.48%,对NO3--N为22.34%、18.33%和10.66%,对NH4+-N为37.88%、13.98%和25.72%,对TP为53.12%、8.38%和41.97%;(3)金鱼藻与环棱螺在脱氮除磷时表现出正、负相互作用,负交互作用一定程度地促进了N、P浓度的升高.鉴于水体景观质量的提高和富营养化控制,同时使用沉水植物和螺类有利于水体的生态修复.     

潜流-上行垂直流复合人工湿地对氮磷去除效果

研究了潜流-上行垂直流复合人工湿地工艺对NH4+-N、NO3--N、TN和TP的去除效果。在处理负荷为30 L.d-1,水力停留时间为4.8 d时,该工艺对NH4+-N、NO3--N、TN和TP具有良好的去除效果,平均去除率分别为95%、52%、79%和81%。对3种含氮化合物的去除效果可以根据运行时间分为两阶段,在两阶段中,对NH4+-N、NO3--N和TN的平均去除率分别为93%和99%,35%和98%,71%和98%。对TP的去除效果在整个试验过程中则保持稳定。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.