ABCA1的胞内运输及功能研究新进展

三磷酸腺苷结合盒转运体A1(ABCA1)具有介导细胞内脂质流出,维持细胞脂质稳态的功能．新生的ABCA1必须经过胞内运输和各种化学修饰等过程,最终成为具有功能的成熟转运体,才能行使其转运脂质的功能,因此,ABCA1在胞内的运输过程和正确质膜定位对其介导胆固醇流出的功能至关重要．目前ABCA1相关研究主要集中于脂质转运方面,并提出各种胆固醇流出机制的模型,如通道转运模型、蘑菇状突起模型和胞吞-胞吐转运模型等．最近研究显示,ABCA1还具有调节质膜脂筏结构、参与免疫和炎症调节等新功能．本文主要针对ABCA1的胞内运输过程以及各种功能做一综述,以期为动脉粥样硬化相关疾病提供新的治疗靶点和途径．     

Interactions between cyazofamid and human drug transporters

We aimed to investigate the intestinal permeability and interaction of cyazofamid with clinically important transporters. The intestinal permeability of cyazofamid was low (0.21 ± 0.02 cm/s), and it is a substrate for P‐glycoprotein (P‐gp) with a K_m value of 83.1 μM, indicated that P‐gp in the intestinal lumen could serve as a protective barrier to this fungicide. Cyazofamid was not a substrate for clinically important transporters. However, cyazofamid inhibited organic cation transporter 3 (OCT3) and OAT1, with IC₅₀ values of 1.54 and 17.3 μM, respectively, but could not result in OAT3‐ and OAT1‐mediated cyazofamid‐drug interactions because of its low plasma concentration. Cyazofamid poorly interacted with OCT1, OCT2, organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, P‐gp, breast cancer resistance‐related protein, and multidrug resistance‐related protein 2. In conclusion, the interactions of cyazofamid with human drug transporters have been evaluated as part of the safety assessment. Given its low intestinal permeability and poor interaction with human drug transporters, cyazofamid might not cause serious toxicity or adverse events.     

Integrated management for sustainable cropping systems: Looking beyond the greenhouse balance at the field scale

Cover crops (CC) promote the accumulation of soil organic carbon (SOC), which provides multiple benefits to agro‐ecosystems. However, additional nitrogen (N) inputs into the soil could offset the CO₂ mitigation potential due to increasing N₂O emissions. Integrated management approaches use organic and synthetic fertilizers to maximize yields while minimizing impacts by crop sequencing adapted to local conditions. The goal of this work was to test whether integrated management, centered on CC adoption, has the potential to maximize SOC stocks without increasing the soil greenhouse gas (GHG) net flux and other agro‐environmental impacts such as nitrate leaching. To this purpose, we ran the DayCent bio‐geochemistry model on 8,554 soil sampling locations across the European Union. We found that soil N₂O emissions could be limited with simple crop sequencing rules, such as switching from leguminous to grass CC when the GHG flux was positive (source). Additional reductions of synthetic fertilizers applications are possible through better accounting for N available in green manures and from mineralization of soil reservoirs while maintaining cash crop yields. Therefore, our results suggest that a CC integrated management approach can maximize the agro‐environmental performance of cropping systems while reducing environmental trade‐offs.     

Nitrification in Dutch heathland soils

A survey was conducted over a range of 17 Dutch heathland locations, subdivided into 41 sites dominated by either dwarf-shrubs (Calluna vulgaris or Erica tetralix) or grass species (Deschampsia flexuosa or Molinia caerulea). Among the habitats of the dominant plant species relatively little differences in general soil properties were observed. The P status of Deschampsia sites was relatively high as well as the NO₃ ^–-N concentrations in the 0–10 cm layer (FH included) at the grass-dominated sites. At sites with a dead or degenerating dwarf-shrub vegetation, NH₄ ⁺-N concentrations reached very high levels.Net production of nitrate was observed during incubation of intact 0–10 cm soil cores (FH-layer included) in the laboratory for all sites, even though in some instances, particularly at Calluna and Erica sites, no nitrate was initially measured. Generally, a higher nitrification rate was found for the grass-dominated sites, and for Deschampsia in particular. The net production of nitrate was highly significantly correlated with net N mineralization, being a reasonable predictor of nitrification in a simple regression model (R²=0.47; P<0.001). Net nitrification was also significantly correlated with the NO₃ ^–-N initially present at the start of the growing season (R=0.65; P<0.001) and with the labile organic P content of the soil (R=0.65; P<0.001). By including initial NO₃ ^–-N and labile organic P, together with net N mineralization and pH, in a multiple regression model, net nitrate production could be predicted with a much higher precision (R²=0.75; P<0.001). Although apparent nitrification was not significantly correlated with pH, the latter contributed significantly to the multiple regression equation for the prediction of the former.The influence of the labile organic P pool may act via its positive correlation with microbial biomass, thus more or less reflecting the potential mineralization/nitrifying capacity of a particular site.     

雪被去除对川西亚高山云杉林土壤活性氮的影响

气候变化引发的季节性雪被改变可能对高寒森林土壤氮循环产生深刻影响.以遮雪棚去除雪被,研究了雪被去除样方和对照样方在不同关键时期(雪被初期、深雪被期和雪被融化期)土壤氮库和矿化速率的变化.结果表明: 季节性雪被对土壤具有良好的保温作用,雪被去除使得5 cm深度土壤平均温度和最低温度分别降低0.33和1.17 ℃,并明显增加了土壤冻结深度和冻融循环.土壤活性氮在不同雪被时期存在显著差异.雪被去除使得冬季土壤铵态氮、硝态氮和可溶性有机氮增加38.6%、23.5%和57.3%.此外,雪被去除也促进了融化期土壤硝化和矿化速率的增加.因此,未来气候变暖引起的雪被减少可能加快川西亚高山森林冬季土壤氮循环.     

Nitrogen uptake and the importance of internal nitrogen loading in Lake Balaton

1. The importance of various forms of nitrogen to the nitrogen supply of phytoplankton has been investigated in the mesotrophic eastern and eutrophic western basin of Lake Balaton.
2. Uptake rates of ammonium, urea, nitrate and carbon were measured simultaneously. The uptake rates were determined using N and C methodologies, and N2‐fixation was measured using the acetylene‐reduction method. The light dependence of uptake was described with an exponential saturation equation and used to calculate surface‐related (areal) daily uptake.
3. The contribution of ammonium, urea and nitrate to the daily nitrogen supply of phytoplankton varied between 11 and 80%, 17 and 73% and 1 and 15%, respectively. N2‐fixation was negligible in the eastern basin and varied between 5 and 30% in the western region of the lake. The annual external nitrogen load was only 10% of that utilized by algae.
4. The predominant process supplying nitrogen to the phytoplankton in the lake is the rapid recycling of ammonium and urea in the water column. The importance of the internal nutrient loading is emphasized.     

Effect of ammonium and nitrate on ferric chelate reductase and nitrate reductase in Vaccinium species

BACKGROUND AND AIMS: Most Vaccinium species have strict soil requirements for optimal growth, requiring low pH, high iron availability and nitrogen primarily in the ammonium form. These soils are limited and are often located near wetlands. Vaccinium arboreum is a wild species adapted to a wide range of soils, including high pH, low iron, and nitrate-containing soils. This broader soil adaptation in V. arboreum may be related to increased efficiency of iron or nitrate uptake compared with the cultivated Vaccinium species. METHODS: Nitrate, ammonium and iron uptake, and nitrate reductase (NR) and ferric chelate reductase (FCR) activities were compared in two Vaccinium species grown hydroponically in either nitrate or ammonia, with or without iron. The species studied were the wild V. arboreum and the cultivated V. corymbosum interspecific hybrid, which exhibits the strict soil requirements of most Vaccinium species. RESULTS: Ammonium uptake was significantly greater than nitrate uptake in both species, while nitrate uptake was greater in the wild species, V. arboreum, compared with the cultivated species, V. corymbosum. The increased nitrate uptake in V. arboreum was correlated with increased root NR activity compared with V. corymbosum. The lower nitrate uptake in V. corymbosum was reflected in decreased plant dry weight in this species compared with V. arboreum. Root FCR activity increased significantly in V. corymbosum grown under iron-deficient conditions, compared with the same species grown under iron-sufficient conditions or with V. arboreum grown under either iron condition. CONCLUSIONS: V. arboreum appears to be more efficient in acquiring nitrate compared with V. corymbosum, possibly due to increased NR activity and this may partially explain the wider soil adaptation of V. arboreum.     

硝酸镧对霍霍巴多芽苗生长的促进作用及植株再生

在增殖培养基(改良MS 2mg／L6-BA 0．5mg／LG3)中添加1～3．5mg／L硝酸镧,对霍霍巴试管苗生长有显著促进作用,2．5mg／L硝酸镧对多芽分化有极显著的促进;在生根培养基(改良1/2MS 3mg／LIBA 1．5mg／LNAA)中,1～2mg／L的La(NO3)3对根的分化有显著的促进作用,生根率提高,最佳浓度为2．0mg／L。过高的浓度对试管苗生长有一定抑制。试验表明,不同器官对硝酸镧的敏感程度不同。取2cm高以上的霍霍巴试管苗,用25mg／L IBA或NAA处理30min,扦插于沙基质中。保持室温20～30℃。50d后揭去覆膜,保持光强3000 lx,相对湿度85％以上。正常管理条件下成活率达75％。     

铬(Ⅲ)-天冬氨酸螯合物合成与分析

研究了铬(Ⅲ)-天冬氨酸螯合物的合成方法,探讨了影响合成工艺的主要因素,确定了原料配比、pH值、最佳反应时间及温度,采用X射线衍射光谱对螯合物进行了表征,结果表明铬(Ⅲ)能与天冬氨酸形成螯合物。