Tallgrass prairie restoration: implications of increased atmospheric nitrogen deposition when site preparation minimizes adventive grasses

Site preparation designed to exhaust the soil seedbank of adventive species can improve the success of tallgrass prairie restoration. Despite these efforts, increased rates of atmospheric nitrogen (N) deposition over the next century could potentially promote the growth of nitrophilic, adventive species in tallgrass restoration projects. We used a field experiment to examine how N addition affected species composition and plant productivity over the first 3 years of a tallgrass prairie restoration that was preceded by the planting of glyphosate‐resistant crops and multiple applications of glyphosate to exhaust the pre‐existing seedbank. We predicted that N addition would increase the percent cover of adventive plant species not included in the original seeding. Contrary to our prediction, only the cover of native species increased with N addition; native non‐leguminous forbs increased substantially, with Conyza canadensis (a weedy native species not part of the restoration seed mix) exploiting the combination of high N and bare ground in the first year, and non‐leguminous forbs (in particular Monarda fistulosa) and native C₃ grasses, all of which were seeded, increasing with N addition by the third year. Native legumes was the only functional group that exhibited lower cover in N addition plots than in control plots. There was no significant response by native C₄ grasses to N addition, and adventive grasses remained mostly absent from the plots. Overall, our results suggest that site pre‐treatment with herbicide may continue to be effective in minimizing adventive grasses in restored tallgrass prairie, despite future increases in atmospheric N deposition.     

Production of xylooligosaccharides by xylanase from Pichia stipitis based on xylan preparation from triploid Populas tomentosa

Xylooligosaccharides (XOS) with DP 2-4 are important synbiotics used as food ingredients based on its prebiotic characteristics. In this work, the production of XOS from lignocellulosic material was performed by combined chemical-enzymatic methods. Xylan was prepared from triploid Populas tomentosa, and bioconverted into XOS by crude xylanase solution obtained from Pichia stipitis. The effects of reaction time, temperature, enzyme dosage, and pH value on the production of XOS were fully evaluated. Under the optimal condition (25 U g⁻¹ substrate, pH 5.4 and 50 °C), 36.8% of the xylan preparation was converted to XOS, equivalent to 3.95 mg/mL of the hydrolyzate. Xylobiose, xylotriose and xylotetrose were analyzed to be the main products of the enzymatic hydrolyzate, which together accounted for over 95% of the released oligosaccharides. Meanwhile, the effect of sonication pretreatment on the conversion efficiency of the xylan preparation was also investigated.     

小麦种子过氧化物酶WP1 基因的原核表达、纯化及多克隆抗体制备

WP1是小麦种子中最主要的阳离子过氧化物酶,该酶不仅参与种子的发育过程,而且影响面粉的加工品质。首先构建了WP1基因原核表达载体pET28a-WP1,并将其转化到T7 Expression大肠杆菌菌株中诱导表达。His-tag融合的WP1主要以包涵体形式存在,使用Ni-NTA亲和层析柱在变性条件下进行纯化,获得纯度大于98％的重组蛋白。重组WP1经尿素梯度透析复性溶解后免疫新西兰大白兔,最终获得WP1多克隆抗体。ELISA分析结果显示制备的WP1兔抗血清的效价大于1∶625 000;Western blotting结果证明制备的多克隆抗体对WP1具有很好的专一性。     

中华蚊母树染色体制片及核型分析

以中华蚊母树根尖为材料,采用常规压片法制片,比较材料的不同采集时间、预处理方法、固定剂、解离方法、解离时间及染色方法对中华蚊母树根尖染色体制片的影响.结果表明最佳的制片技术为:取材时间为上午9:00~11:00或下午13:00~15:00,以饱和对二氯苯预处理3 h,用1 mol?L-1盐酸60℃下解离8 min,卡诺固定剂固定,以改良石碳酸品红染色10 min.以该最佳制片方案对中华蚊母树进行体细胞染色体核型分析,首次揭示了中国特有植物———中华蚊母树体细胞染色体数目为2n=2x=24,染色体基数x=12,染色体核型公式为2n=2x=24=12m(2SAT)+10sm+2st,主要由中部和近中部着丝点染色体组成;染色体相对长度组成为2n=24=2L+8M2+12M1+2S,核型不对称指数为64.29%,属于2A型.结果显示中华蚊母树核型对称程度较高,在进化中属于比较原始的类型.     

两种榕属植物的染色体核型分析

采用根尖压片法对菩提树(Ficus religiosa Linn.)和小叶榕(Ficus microcarpa L.f.)进行染色体核型分析.结果显示两种植物的染色体数目均为2n=30,核型类型均为1B,核型公式分别为菩提树2n=2x=30=24m(2SAT)+6sm,小叶榕2n=2x=30=28m(2SAT)+2sm.比较发现,两种植物的核型相似,亲缘关系相近,二者中小叶榕的不对称系数较小(58.16%),为较原始的类型.两者的核型均为首次报道.     

低温电子显微技术在膜蛋白结构研究中的应用和展望

介绍了蛋白质电子晶体学和单颗粒分析技术这两种低温电子显微技术在膜蛋白和膜蛋白复合体结构研究中的具体方法和近10~20年来的实际应用,并分别分析了这两种方法的优势和瓶颈。此外,还介绍了Amphipol替代、Streptavidin二维晶体锚定脂质体和纳米球包被脂质体等近两年来出现的新的用于低温电镜成像的膜蛋白样品制备方法。最后对膜蛋白的低温电子显微研究的未来发展做了展望。     

家蚕核型多角体病毒BmNPV囊膜蛋白P74膜外区克隆和原核表达

通过PCR扩增家蚕核型多角体病毒(Bombyx mori nucleopolyhedrovirus,BmNPV)囊膜蛋白p74基因膜外区片段,对切胶纯化得到的DNA目的片段与原核表达载体pET28a进行连接,通过不同浓度的IPTG对含有pET28a-p74重组质粒的大肠杆菌BL21(DE3)进行诱导,对诱导产物进行SDS-PAGE电泳.结果表明p74基因膜外区获得了表达;通过His单抗对原核表达产物进行Western blotting分析,其结果证实诱导蛋白带为融合有组氧酸的目的蛋白.对割胶获得的P74蛋白和免疫佐剂进行克分研磨,以研磨后的匀浆液对昆明小鼠进行皮下多点注射,通过收获的抗血清对BmNPV ODV病毒粒子进行Westem blotting分析,检测到一条分子量大小为74 kD的特异杂交带,表明获得的多抗可用于P74蛋白功能的进一步研究.     

后磨牙模拟根管模型制备与研究

目的：制备后磨牙模拟根管模型。方法：依照预实验中测试的牙本质和树脂根管模型材料的布氏硬度值（牙本质HB72,树脂块HB54）选取纯铜质铜管为材料（纯铜HB58）同时利用预实验中确认的后磨牙模拟根管模型弯曲角度的范围（70°-60°）并参照树脂根管模型相关数据,设计不同弯曲角度（70°,64°,60°）的纯铜质根管模型,将20套镍钛根管锉随机分为4组,其中3组根管锉分别预备相应角度的10个纯铜质后磨牙根管模型,另一组在临床预备10个后磨牙根管作为对照组。所有镍钛根管锉均在疲劳寿命测试装置中测试疲劳寿命。结果：选用根管长度为16mm±1mm,弯曲半径为5mm,内径为0.70mm的纯铜质铜管制作后磨牙根管模型。其中在弯曲角度为70°的后磨牙根管模型中有33%（2/6）近似临床;在弯曲角度为64°的后磨牙根管模型中有67%（4/6）近似临床;在弯曲角度为60°的后磨牙根管模型中有33%（2/6）近似临床。结论：弯曲角度为64°的纯铜制后磨牙模拟根管模型更接近于临床实际,可为体外研究镍钛根管锉各项指标提供一个较为理想的模型。     

Procedures for rat in situ skeletal muscle contractile properties

There are many circumstances where it is desirable to obtain the contractile response of skeletal muscle under physiological circumstances: normal circulation, intact whole muscle, at body temperature. This includes the study of contractile responses like posttetanic potentiation, staircase and fatigue. Furthermore, the consequences of disease, disuse, injury, training and drug treatment can be of interest. This video demonstrates appropriate procedures to set up and use this valuable muscle preparation. To set up this preparation, the animal must be anesthetized, and the medial gastrocnemius muscle is surgically isolated, with the origin intact. Care must be taken to maintain the blood and nerve supplies. A long section of the sciatic nerve is cleared of connective tissue, and severed proximally. All branches of the distal stump that do not innervate the medial gastrocnemius muscle are severed. The distal nerve stump is inserted into a cuff lined with stainless steel stimulating wires. The calcaneus is severed, leaving a small piece of bone still attached to the Achilles tendon. Sonometric crystals and/or electrodes for electromyography can be inserted. Immobilization by metal probes in the femur and tibia prevents movement of the muscle origin. The Achilles tendon is attached to the force transducer and the loosened skin is pulled up at the sides to form a container that is filled with warmed paraffin oil. The oil distributes heat evenly and minimizes evaporative heat loss. A heat lamp is directed on the muscle, and the muscle and rat are allowed to warm up to 37°C. While it is warming, maximal voltage and optimal length can be determined. These are important initial conditions for any experiment on intact whole muscle. The experiment may include determination of standard contractile properties, like the force-frequency relationship, force-length relationship, and force-velocity relationship. With care in surgical isolation, immobilization of the origin of the muscle and alignment of the muscle-tendon unit with the force transducer, and proper data analysis, high quality measurements can be obtained with this muscle preparation.     

开展临床指导教师对普通专科医师培训情况的调查结果分析

目的:调查我院专科医师培训开展的整体情况,为继续做好专科医师培训工作提供依据。方法:随机调查我院参与普通专科医师培训轮转科室的指导教师,发放自制调查表。结果:90%以上导师认为科室带教质量高;48.78%导师认为临床科室应为学员每月发放1000元以上生活补助;60.98%导师认为硕士研究生普通专科医师培训时间应为二年;60%以上导师认为应着重硕士研究生临床操作技能、医患沟通能力、病历书写能力及阅片能力等方面能力的培训;50%以上导师认为目前培训中存在的主要问题是生活无保障;图书馆国内外最新文献不足;监管力度不强;临床技能培训针对性不强等。结论:我院开展普通专科医师培训整体情况较好。但仍存在很多问题,在今后的培训过程中应继续为学员的生活提供更多保障,继续加强管理监督,保证培训按计划、按质量完成。