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1.
Accurate estimation of forest biomass C stock is essential to understand carbon cycles. However, current estimates of Chinese forest biomass are mostly based on inventory-based timber volumes and empirical conversion factors at the provincial scale, which could introduce large uncertainties in forest biomass estimation. Here we provide a data-driven estimate of Chinese forest aboveground biomass from 2001 to 2013 at a spatial resolution of 1 km by integrating a recently reviewed plot-level ground-measured forest aboveground biomass database with geospatial information from 1-km Moderate-Resolution Imaging Spectroradiometer (MODIS) dataset in a machine learning algorithm (the model tree ensemble, MTE). We show that Chinese forest aboveground biomass is 8.56 Pg C, which is mainly contributed by evergreen needle-leaf forests and deciduous broadleaf forests. The mean forest aboveground biomass density is 56.1 Mg C ha−1, with high values observed in temperate humid regions. The responses of forest aboveground biomass density to mean annual temperature are closely tied to water conditions; that is, negative responses dominate regions with mean annual precipitation less than 1300 mm y−1 and positive responses prevail in regions with mean annual precipitation higher than 2800 mm y−1. During the 2000s, the forests in China sequestered C by 61.9 Tg C y−1, and this C sink is mainly distributed in north China and may be attributed to warming climate, rising CO2 concentration, N deposition, and growth of young forests.  相似文献   
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【目的】采用高通量测序方法研究强化玉米饮食对小鼠肠道菌群结构的影响以及可提高宿主糖代谢相关菌群功能基因的分析。【方法】分别给予两组小鼠(各10只)常规饮食和强化玉米饮食(1/4的玉米粉加3/4的常规饮食成分),喂养10周,之后采集小鼠粪便样本,提取DNA,使用高通量测序仪进行宏基因组测序分析,比较两组小鼠肠道菌群和功能基因的差异。【结果】两组小鼠的终末体重没有明显差异。各样本DNA的测序有效率足够,肠道菌群的多样性存在一定差异。属放线菌门(Actinobacteria)的双歧杆菌(Bifidobacteriales)-B.pseudolongum分支和Coriobacteriia-Collinsella/Enterorhabdus分支的丰度在强化玉米饮食组的小鼠中显著升高,相应的宏基因组中涉及糖酵解和胆汁酸合成的一些酶和功能单元的含量也在强化玉米饮食组显著升高。【结论】强化玉米饮食可以提高肠道菌群中双歧杆菌等益生菌的丰度,增加宏基因组糖脂代谢相关基因和通路的含量,从而可能促进宿主的糖代谢功能。  相似文献   
4.
Two series of 1,3-diphenyl-1H-pyrazole derivatives containing rhodanine-3-alkanoic acid groups were identified as competitive protein tyrosine phosphatase 1B (PTP1B) inhibitors. Among the compounds studied, IIIv was found to have the best in vitro inhibition activity against PTP1B (IC50?=?0.67?±?0.09?µM) and the best selectivity (9-fold) between PTP1B and T-cell protein tyrosine phosphatase (TCPTP). Molecular docking studies demonstrated that compounds IIIm, IIIv and IVg could occupy simultaneously at both the catalytic site and the adjacent pTyr binding site. These results provide novel lead compounds for the design of inhibitors of PTP1B as well as other PTPs.  相似文献   
5.
Three novel series of dihydrotriazine derivatives bearing 1,3-diaryl pyrazole moieties were designed, synthesized and evaluated in terms of their antibacterial and antifungal activities. Most of the synthesized compounds showed potent inhibition of several Gram-positive bacterial strains (including multidrug-resistant clinical isolates) and Gram-negative bacterial strains with minimum inhibitory concentration values in the range of 1–64?µg/mL. Compounds 4b and 4c presented the most potent inhibitory activity against Gram-positive bacteria (S. aureus 4220, MRSA 3167, QRSA 3519) and Gram-negative bacteria (E. coli 1924), with minimum inhibitory concentration values of 1 or 2?µg/mL. Compared with previous studies, these compounds exhibited a broad spectrum of inhibitory activity. The cytotoxic activity of the compounds 4a, 4b, 4c and 11n were assessed in L02 cells. In vitro enzyme study implied that compound 4c exerted its antibacterial activity through DHFR inhibition.  相似文献   
6.
Recent studies have revealed large unexplained variation in heat requirement‐based phenology models, resulting in large uncertainty when predicting ecosystem carbon and water balance responses to climate variability. Improving our understanding of the heat requirement for spring phenology is thus urgently needed. In this study, we estimated the species‐specific heat requirement for leaf flushing of 13 temperate woody species using long‐term phenological observations from Europe and North America. The species were defined as early and late flushing species according to the mean date of leaf flushing across all sites. Partial correlation analyses were applied to determine the temporal correlations between heat requirement and chilling accumulation, precipitation and insolation sum during dormancy. We found that the heat requirement for leaf flushing increased by almost 50% over the study period 1980–2012, with an average of 30 heat units per decade. This temporal increase in heat requirement was observed in all species, but was much larger for late than for early flushing species. Consistent with previous studies, we found that the heat requirement negatively correlates with chilling accumulation. Interestingly, after removing the variation induced by chilling accumulation, a predominantly positive partial correlation exists between heat requirement and precipitation sum, and a predominantly negative correlation between heat requirement and insolation sum. This suggests that besides the well‐known effect of chilling, the heat requirement for leaf flushing is also influenced by precipitation and insolation sum during dormancy. However, we hypothesize that the observed precipitation and insolation effects might be artefacts attributable to the inappropriate use of air temperature in the heat requirement quantification. Rather than air temperature, meristem temperature is probably the prominent driver of the leaf flushing process, but these data are not available. Further experimental research is thus needed to verify whether insolation and precipitation sums directly affect the heat requirement for leaf flushing.  相似文献   
7.
Luo R  Jin Z  Deng Y  Strokes N  Piao X 《PloS one》2012,7(1):e29818
GPR56 is a member of the adhesion G protein-coupled receptor (GPCR) family. Mutations in GPR56 cause a devastating human brain malformation called bilateral frontoparietal polymicrogyria (BFPP). Using the N-terminal fragment of GPR56 (GPR56(N)) as a probe, we have recently demonstrated that collagen III is the ligand of GPR56 in the developing brain. In this report, we discover a new functional domain in GPR56(N), the ligand binding domain. This domain contains four disease-associated mutations and two N-glycosylation sites. Our study reveals that although glycosylation is not required for ligand binding, each of the four disease-associated mutations completely abolish the ligand binding ability of GPR56. Our data indicates that these four single missense mutations cause BFPP mostly by abolishing the ability of GPR56 to bind to its ligand, collagen III, in addition to affecting GPR56 protein surface expression as previously shown.  相似文献   
8.
We use eddy covariance measurements of net ecosystem productivity (NEP) from 21 FLUXNET sites (153 site-years of data) to investigate relationships between phenology and productivity (in terms of both NEP and gross ecosystem photosynthesis, GEP) in temperate and boreal forests. Results are used to evaluate the plausibility of four different conceptual models. Phenological indicators were derived from the eddy covariance time series, and from remote sensing and models. We examine spatial patterns (across sites) and temporal patterns (across years); an important conclusion is that it is likely that neither of these accurately represents how productivity will respond to future phenological shifts resulting from ongoing climate change. In spring and autumn, increased GEP resulting from an ‘extra’ day tends to be offset by concurrent, but smaller, increases in ecosystem respiration, and thus the effect on NEP is still positive. Spring productivity anomalies appear to have carry-over effects that translate to productivity anomalies in the following autumn, but it is not clear that these result directly from phenological anomalies. Finally, the productivity of evergreen needleleaf forests is less sensitive to phenology than is productivity of deciduous broadleaf forests. This has implications for how climate change may drive shifts in competition within mixed-species stands.  相似文献   
9.
The objective was to investigate the effects of oxygen tension and follicle cells (FCs) during in vitro maturation of porcine oocytes in only porcine (Sus scrofa domesticus) follicular fluid (pFF), using static and non-static (rotating) culture systems, on the nuclear maturation and subsequent in vitro fertilization of the oocytes. In the first experiment, cumulus-oocyte complexes (COCs) were matured for 48 h in pFF supplemented with (+) or without (−) FCs (5.2 × 106 cells/mL), using the static (S) and rotating (R) culture systems (+FC/S, −FC/S, +FC/R, and −FC/R) under 5% or 20% O2. Co-culture with FCs in the static culture system (+FC/S) had a detrimental effect on the meiotic competence of oocytes, whereas co-culture with FCs in the rotating culture system (+FC/R) increased maturation rates. In both culture systems, oxygen tension had no apparent effects on meiotic competence of oocytes, irrespective of culture system and FC addition. In the second experiment, COCs were matured under 5% or 20% O2 using the −FC/S or +FC/R culture systems and then fertilized. Oxygen tension had no significant effects on fertilization parameters, irrespective of the culture system. The rotating culture system increased rates of sperm penetration and male pronuclear formation and decreased polyspermic fertilization compared with the static culture system (P < 0.05). In conclusion, both −FC/S and +FC/R culture systems supported meiotic competence, irrespective of oxygen tension. However, the +FC/R culture system may be superior to the −FC/S culture system for promoting fertilization.  相似文献   
10.
 <正> 1980年,Hunter首次发现Rous肉瘤病毒转化的细胞,其蛋白质分子上的酪氨酸残基磷酸化水平明显升高。现已知道,其它的肿瘤病毒诱导的转化细胞以及某些恶性肿瘤细胞的酪氨酸残基磷酸化作用亦有不同程度的增强。但迄今物理的致癌因素如放射性同位素引起的细胞转化是否伴随着酪氨酸特异的磷酸化的增强,尚未见报道。因此,本实验对C_3H10  相似文献   
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