The Toxoplasma gondii type-II NADH dehydrogenase TgNDH2-I is inhibited by 1-hydroxy-2-alkyl-4(1H)quinolones

The apicomplexan parasite Toxoplasma gondii does not possess complex I of the mitochondrial respiratory chain, but has two genes encoding rotenone-insensitive, non-proton pumping type-II NADH dehydrogenases (NDH2s). The absence of such "alternative" NADH dehydrogenases in the human host defines these enzymes as potential drug targets. TgNDH2-I and TgNDH2-II are constitutively expressed in tachyzoites and bradyzoites and are localized to the mitochondrion as shown by epitope tagging. Functional expression of TgNDH2-I in the yeast Yarrowia lipolytica as an internal enzyme, with the active site facing the mitochondrial matrix, permitted growth in the presence of the complex I inhibitor DQA. Bisubstrate kinetics of TgNDH2-I measured within Y. lipolytica mitochondrial membrane preparations were in accordance with a ping-pong mechanism. Using inhibition kinetics we demonstrate here that 1-hydroxy-2-alkyl-4(1)quinolones with long alkyl chains of C(12) (HDQ) and C(14) are high affinity inhibitors for TgNDH2-I, while compounds with shorter side chains (C(5) and C(6)) displayed significantly higher IC(50) values. The efficiency of the various quinolone derivatives to inhibit TgNDH2-I enzyme activity mirrors their inhibitory potency in vivo, suggesting that a long acyl site chain is critical for the inhibitory potential of these compounds.     

Nitrous oxide and methane fluxes from soils of the Orinoco savanna under different land uses

The study investigates the effect of land‐use change on nitrous oxide (N₂O) and methane (CH₄) fluxes from soil, in savanna ecosystems of the Orinoco region (Venezuela). Gas fluxes were measured by closed static chambers, in the wet and dry season, in representative systems of land management of the region: a cultivated pasture, an herbaceous savanna, a tree savanna and a woodland (control site). Higher N₂O emissions were observed in the cultivated pasture and in the herbaceous savanna compared with the tree savanna and the woodland, and differences were mainly related to fine soil particle content and soil volumetric water content measured in the studied sites. Overall N₂O emissions were quite low in all sites (0–1.58 mg N₂O‐N m^?2 day^?1). The cultivated pasture and the woodland savanna were on average weak CH₄ sinks (?0.05±0.07 and ?0.08±0.05 mg CH₄ m^?2 day^?1, respectively), whereas the herbaceous savanna and the tree savanna showed net CH₄ production (0.23±0.05 and 0.19±0.05 mg CH₄ m^?2 day^?1, respectively). Variations of CH₄ fluxes were mainly driven by variation of soil water‐filled pore space (WFPS), and a shift from net CH₄ consumption to net CH₄ production was observed at around 30% WFPS. Overall, the data suggest that conversion of woodland savanna to managed landscape could alter both CH₄ and N₂O fluxes; however, the magnitude of such variation depends on the soil characteristics and on the type of land management before conversion.     

美国不同棱型大麦种质资源品质分析

对新引进的300份美国大麦种质资源不同棱型间蛋白质、赖氨酸和淀粉含量的鉴定结果分析表明:①二棱大麦蛋白质总体方差与六棱大麦具有极显著的差异,其频率分布分别是以含量12.5%和17.0%为中心的双峰分布,这可能反映了二棱大麦利用上的新特点;淀粉含量二棱大麦显著高于六棱;六棱大麦当蛋白质作为固定变量时,赖氨酸与淀粉的相关性不显著.②提出了促进SPSS统计分析软件在农业科研上的开发应用研究的建议.     

Costimulation of resting B lymphocytes alters the IL-4-activated IRS2 signaling pathway in a STAT6 independent manner: implications for cell survival and proliferation

INTRODUCTIONThe inappropriate enhancement of lymphocytesurviVal due to a block in programmed cell deathand/or an enhancement of entry into the cell cyclecan contribute to the abnormal expansion of clonesresulting in tumorigenesis or the breakdown of pe-ripheral self-toleranced, 2]. Proper lymphocytehomeostasis is critical for normal immune functionand is maintained by a complex series of cellularinteractions and the action of secreted cytokines.Illterleukin-4 (IL-4), a cytokine produced …     

中华眼镜蛇伤致局部组织损伤治疗的实验研究

目的 探讨中华眼镜蛇伤致局部组织损伤的最佳治疗方法。方法 用中华眼镜蛇毒作家兔局部组织损伤模型,分别采用抗蛇素血清局部注射、糜蛋白酶局部注射、蛇伤药酒外敷、坏死组织早期切除、局部烧灼法、局部组织切开冲洗,共6种处理方法进行局部治疗,观察其疗效。结果 6种治疗方法从优到劣依次是：抗蛇毒血清局部注射、糜蛋白酶局部注射、蛇伤药酒外敷、坏死组织早期切除、局部烧灼法、局部组织切开冲洗。结论 中华眼镜蛇伤致局部组织损伤的治疗方法应首选抗蛇毒血清局部注射和糜蛋白酶局部注射,其次选用蛇伤药酒外敷。     

Rheology and gelation of water-insoluble dextran from Leuconostoc mesenteroides NRRL B-523

Dynamic oscillatory testing has been used to study the rheology of water-insoluble dextran. The rheological properties (storage and loss moduli) of dextran gel were measured and dextran was found to be neither a strong gel nor a weak gel, but an entanglement network at a concentration of 250 mg/ml. The extent of gelation, illustrated by the gel elastic modulus G′, is found to decrease with increasing concentration of calcium ions. This was confirmed by shift of crossover frequencies towards higher values on the dynamic spectra and lower yield stress τ values obtained from stress ramp experiments. Finally, a comparison between gelation of dextran and alginate (a similar biopolymer) was made for clear understanding of effect of calcium ions on the dextran gelation.