西瓜连作对土壤主要微生物类群和土壤酶活性的影响

从昌乐不同种植年限西瓜大棚采集土壤,测定了连续种植6、8、10、14和20年西瓜大棚土壤中细菌、放线菌和真菌数量、土壤酶活性及土壤理化特性状的变化特点.结果表明:随着种植年限的增加,土壤中细菌、放线菌呈现先升后降趋势;真菌数量变化趋势则与之相反;蛋白酶、多酚氧化酶也同样呈现先升后降趋势,脲酶呈下降趋势,蔗糖酶呈上升趋势;同时在连作栽培过程中,土壤中速效氮含量较为稳定,速效钾和速效磷的含量随着连作年限的增加出现少量积累,土壤酸化日趋严重.讨论了连作条件下土壤微生物数量与土壤酶活性及土壤理化性状之间的关系.     

Governmental policies on HIV infection in China

EVOLUTION OF THE GOVERNMENT POLI- CIES Looking back 20 and more years, one could have hardly imagined that such great changes would have happened to the governmental policies on HIV/AIDS in China. In the earlier phase of the epidemic, laws and regulations were drafted based on the practices and experiences of preven- tion and control of other infectious diseases, such as isolation, quarantine and compulsory testing and examina- tions etc. When the HIV/AIDS epidemic was firstl…     

Improved Cardiac Contractility of Human Recombinant Growth Hormone on the Congestive Heart Failure of Pig

1Introduction Congestiveheartfailureisamultipleaetiology,high prevalence,cardiovasculardisorderwithpoorprognosis. Medicaltreatmentofdilatedcardiomyopathyisaimedat alleviatingthesymptomsofheartfailure.Diuretics,ACE inhibitorsandbeta blockershavefavourableeffectson symptoms,exercisecapacityandmortality[1-3].Growth hormone(GH)andinsulin likegrowthfactor(IGF) 1 areinvolvedinseveralphysiologicalprocessessuchas thecontrolofmusclemassandfunction,bodycomposi tionandtheregulationofnutrientmetaboli…     

A Computational Model of Soil Adhesion and Resistance for a Non-smooth Bulldozing Plate

1IntroductionAdhesive forces exist between soil and the surfacesof soil-engaging components[1,2].Soil adhesion increasesthe running resistance and energy consumption,andaffects the operating quality.Soil adhesion also reducesthe working productivity of terrain machines,even worseit makes terrain machines fail to run.Reducing theadhesive force of the soil-engaging machines will have aprofound influence for cultivation.Through theinvestigation of soil animals,we have found that soilanimals poss…     

中国植物区系新资料

在对中国科学院西双版纳热带植物园标本馆植物标本的鉴定清理工作中,发现中国新记录植物2种,兹报道如下,供有关部门和研究者参考。     

严重急性呼吸综合征动物模型中血清因子的检测

严重急性呼吸综合征是一种新近出现的严重传染性疾病,病原体为一种新的冠状病毒。但其免疫病理的发病机制尚未阐明,我们用SARS病毒感染了恒河猴和leiws大鼠,经PCR和抗体检测,证明病毒在动物体内有复制。用酶连免疫吸附试验测量动物血清中白介素(IL)-6,白介素(IL)-10,γ-干扰素(INF),肿瘤坏死因子(TNF)-α的含量。结果显示,血清中IL-10和INF-γ的含量在感染前后无显著性差异。感染后动物体内IL-6显著升高,其含量与肺部病变程度呈正相关。TNF-α的含量降低。动物模型中血清免疫因子的测定避免了临床病人由于使用抗病毒药物和激素造成的干扰,对于我们了解免疫因子在SARS免疫病理发病机制的作用有一定帮助。     

三七总RNA提取方法的对比研究

比较利用改进的异硫氰酸胍一步法、异硫氰酸胍高盐法、CTAB法和Thomas’RNA提取法等4种方法提取三七根茎2个部位总RNA的可行性。结果表明,改进的异硫氰酸胍一步法和异硫氰酸胍高盐法能有效地抑制酚类物质、多糖及皂苷等次级代谢产物对总RNA的影响,可从三七根茎中获得质量高、完整性好的总RNA。RT—PCR分析显示提取的总RNA具有反转录活性。这2种方法具有快速、简单、有效的特点。     

A Stable Upstream Stem-loop Structure Enhances Selection of the First 5'-ORF-AUG as a Main Start Codon for Translation Initiation of Human ACAT1 mRNA

Acyl-coenzyme A:cholesterol acyltransferase (ACAT)is an integral membrane protein, which is mainly locatedin rough endoplasmic reticulum (ER), and is responsiblefor catalyzing the intracellular formation of cholesterylester from cholesterol and long-chain fatty acyl-coenzymeA [1,2]. Human ACAT1 cDNA K1 was firstly cloned andfunctionally expressed in 1993 [3]. Further studies withspecific anti-ACAT1 antibody (DM10) illustrated that onemajor 50 kD ACAT1 protein was expressed in various…     

Ⅰ型马立克氏病病毒不同致病型参考株与中国分离株pp24基因的克隆与序列分析

为了比较Ⅰ型马立克氏病病毒(MDV)的致病型与pp24基因的关系,将Ⅰ型MDV弱毒(mMDV)、强毒(vMDV)、超强毒(vvMDV)、特超强毒(vv MDV)等不同致病型的CVI988、GA、648A、RB1B、Md5和Md11等6个国际参考株,从中国河北、北京、广东和广西等地分离的7个中国分离株和1个中国疫苗毒814株的pp24基因分别做PCR扩增,并将其克隆到pMD-18载体中测序,与国外已发表的BC-1株进行序列比较.结果表明:Ⅰ型MDV的pp24基因非常保守,15个毒株中只出现5个碱基的随机变化,并引起相应的4个氨基酸改变,但与致病型无明显相关;pp24基因ORF的第81碱基出现差异,所有中国株为G,所有不同致病型国外参考株为C,但并未引起氨基酸改变,显示这一碱基差异只是作为MDV地域性分布的遗传标志,而与病毒分离的年代及致病型等因素无关.     

Phylogenetic clusters of rhizobia revealed by genome structures

Rhizobiaareagriculturallyandenvironmentallyimportantbacteria.Theirsymbiosiswithleguminousplantsisresponsibleformostoftheatmosphericni-trogenfixedonland.Classificationofthesebacteriabasedontheirnaturalrelationshipswillpromotetheirapplication.Thisresearchemploysanewphylogeneticmethod,i.e.,revelationandcomparisonofgenomestructure,tocategorizerhizobia.Phylogenyisthestudyoftheevolutionaryrelationshipsamongorgan-isms[1].Currentlyphylogeneticrelationshipsamongrhizobiaaremostlyinferredfromcomparisons…