Rhizosphere soil bacterial communities and nitrogen cycling affected by deciduous and evergreen tree species

Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N₂‐fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N‐cycling‐related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta‐diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short‐term drought. Root biomass was the most important factor in driving soil bacterial community and N‐cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N‐cycle‐related functional genes, copy numbers of ammonia‐oxidizing bacteria (AOB) and autotrophic ammonia‐oxidizing archaea (AOA), N₂ fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N‐cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N‐cycling function in artificial forest ecosystems.     

Design,synthesis, and biological evaluation of novel carbazole derivatives as potent DNMT1 inhibitors with reasonable PK properties

The DNA methyltransferases (DNMTs) were found in mammals to maintain DNA methylation. Among them, DNMT1 was the first identified, and it is an attractive target for tumour chemotherapy. DC_05 and DC_517 have been reported in our previous work, which is non-nucleoside DNMT1 inhibitor with low micromolar IC₅₀ values and significant selectivity towards other S-adenosyl-_L-methionine (SAM)-dependent protein methyltransferases. In this study, through a process of similarity-based analog searching, a series of DNMT1 inhibitors were designed, synthesized, and evaluated as anticancer agents. SAR studies were conducted based on enzymatic assays. And most of the compounds showed strong inhibitory activity on human DNMT1, especially WK-23 displayed a good inhibitory effect on human DNMT1 with an IC₅₀ value of 5.0 µM. Importantly, the pharmacokinetic (PK) profile of WK-23 was obtained with quite satisfying oral bioavailability and elimination half-life. Taken together, WK-23 is worth developing as DNMT1-selective therapy for the treatment of malignant tumour.     

Determination of cefazedone in human plasma by high performance liquid chromatography–tandem mass spectrometry: Application to a pharmacokinetic study on Chinese volunteers

A rapid, sensitive and simple high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method was developed for determination of cefazedone in human plasma using metronidazole as internal standard (IS). The chromatographic separation was achieved on an Ultimate XB-CN column (2.1 mm × 150 mm, 5 μm) with an isocratic mobile phase of acetonitrile and 20 mM ammonium acetate in 0.1% formic acid in water (15:85, v/v). Detection was performed using electrospray ionization in positive ion multiple reaction-monitoring mode (SRM), monitoring the transitions m/z 548.2 → 344.1 for cefazedone and m/z 172.2 → 128.1 for IS. Calibration curves were linear over a wide range of 0.20–401.12 μg/mL for cefazedone in plasma. The lower limit of quantification (LLOQ) was 0.20 μg/mL. The intra- and inter-day precisions were less than 7.2%. The average recovery of cefazedone was 90.8–91.0%. The validated method was successfully applied to the pharmacokinetic study of cefazedone in Chinese healthy volunteers following intravenous (IV) administration of 500, 1000 and 2000 mg cefazedone injection.     

嘌呤拟似物对豚鼠胃窦环行肌自发性收缩及电活动的影响

为探讨非肾上腺素能非胆碱能神经递质对胃窦环行肌功能的调节作用,在离体胃平滑肌上观察了嘌呤拟似物对胃窦环行肌自发性收缩活动和电活动的影响。电活动用传统的细胞内微电极记录,并和收缩活动同步描记于多道生理记录仪。结果表明,嘌呤能P2Y受体激动剂,三磷酸腺苷(ATP)和2-methylthio ATP(2-MeSATP)均增强胃窦平滑肌的收缩活动,但不影响电活动,而且ATP和2-MeSATP对胃平滑肌收缩活动的增强作用可被嘌呤能P2Y受体阻断剂,reactive blue-2和苏拉明(suramin)所阻断。用100μmol／L α,β-MeATP引起的脱敏感使P2X受体被阻断,ATP增强胃窦平滑肌收缩活动的效应不受影响。嘌呤能P2X受体激动剂,α,β-MeATP明显抑制胃窦环行肌自发性收缩活动,同时使膜电位明显超极化。ATP对胃窦平滑肌的收缩作用不被L型钙通道阻断剂尼卡地平(nicardipine)阻断,但细胞外用无钙液灌流时这种效应则完全被阻断。用前列腺素合成抑制剂消炎痛预先处理20min后,ATP和2-MeSATP仍能增强胃窦平滑肌的自发性收缩活动。以上结果提示：(1)ATP和2-MeSATP通过嘌呤能P2Y受体增强胃窦平滑肌的自发性收缩活动,而α,β-MeATP或β,γ-MeATP通过嘌呤能P2X受体使膜电位超极化,引起胃窦平滑肌的舒张;(2)ATP和2-MeSATP增强胃窦平滑肌自发性收缩活动的效应依赖于细胞外钙,但钙离子进入细胞的途径并不是电压依赖性钙通道;(3)ATP和2-MeSATP增强胃窦平滑肌自发性收缩活动的效应不通过前列腺素介导。     

Soil Diversity and Land Use in the United States

Soils are dynamic components of terrestrial ecosystems that historically have been viewed as economic resources by government and private interests. The large-scale conversion of many sections of the United States to agriculture and urban land uses, combined with the growing awareness of the role of soils in global biogeochemistry and ecology, ultimately requires an assessment of the remaining distribution of undisturbed soils in the country. Here we conduct the first quantitative analysis of disturbed and undisturbed soil distribution in the USA using a GIS-based approach. We find that a sizable fraction (4.5%) of the nation's soils are in danger of substantial loss, or complete extinction, due to agriculture and urbanization. In the agricultural belt of the country, up to 80% of the soils that were naturally of low abundance are now severely impacted (greater than 50% conversion to agricultural/urban uses). Undisturbed soils provide ecosystem services that warrant their preservation, including a somewhat complex relationship with rare or endangered plants. The known and unknown attributes of undisturbed soils suggests the need for an integrated biogeodiversity perspective in landscape preservation efforts.     

Successive chromosome walking by compatible ends ligation inverse PCR

Here we describe an advanced polymerase chain reaction (PCR) technique, the compatible ends ligation inverse PCR (CELI-PCR) for chromosome walking. In CELI-PCR, several restriction enzymes, which produce compatible cohesive ends, were used to digest target DNA simultaneously or sequentially to produce DNA fragments of suitable size. DNA fragments were then easily circularized and PCR amplification could be carried out efficiently. The previous limitations of inverse PCR were overcome, such as unavailable restriction sites, poor template DNA circularization, and low amplification efficiency. Therefore, successive chromosome walking was performed successfully. Our work, isolating a 11,395-bp fragment from Gossypium hirsutum, was presented as an example to describe how CELI-PCR was carried out.     

利用假型反转录病毒对大部分胰腺切除后再生细胞的世系追踪

胰腺是一个重要的内外分泌混合腺, 胰腺发生损伤后能够再生。为了探讨胰腺活体细胞世系追踪的方法和胰腺损伤后再生细胞的来源,分别通过胰腺伤口涂抹并胰内注射、尾静脉注射及腹腔注射三种方法, 利用假型反转录病毒对成体小鼠大部分切除后胰腺的细胞进行世系追踪。结果发现在活体条件下, 与尾静脉注射及腹腔注射法相比, 胰腺伤口涂抹并胰腺内注射反转录病毒的方法能够更有效的标记胰腺细胞; 而且, 通过对标记细胞的世系追踪研究证明, 在胰腺损伤后, 胰腺腺泡细胞能够接受损伤信号刺激发生再生。为今后进一步利用反转录假病毒对活体胰腺进行细胞命运追踪研究奠定基础, 为利用反转录病毒载体进行胰腺疾病的基因治疗提供线索。     

施肥措施对鳄嘴花(Clinacanthus nutans)生物量的影响

通过施肥措施对鳄嘴花[Clinacanthus nutans(Burm. f.) Lindau]生物量分配的影响研究得到,鳄嘴花各构件生物量与各构件生物量的分配比例并不总是一致。N肥处理组根茎叶以及总生物量均较K低。P肥则为处理4根茎叶以及总生物量较大。而K肥根茎生物量较大的均为处理5,叶和总生物量较大的则为处理4。有机肥的施肥效果对鳄嘴花各构件生物量的促进效果均较差。施肥配比中,各个施肥配比对根、茎生物量的增加效果均较差。叶和总生物量中,则为N1∶P1∶K1效果较好。总体来看,合理施肥对鳄嘴花生物量的增加有促进作用,对生物量的分配产生一定的影响。