松嫩平原旱生芦苇群落土壤呼吸动态及影响因子

为研究松嫩平原旱生芦苇群落土壤呼吸作用的动态变化及其影响因子,于2011年5—10月采用LI-6400土壤呼吸监测系统对旱生芦苇群落土壤呼吸进行连续野外观测,并分析水热因子对土壤呼吸的影响。结果表明:芦苇群落土壤呼吸具有明显的日变化和季节变化特征;其日变化为明显的单峰曲线,土壤呼吸速率峰值出现在中午11:00—13:00;7和8月芦苇群落土壤呼吸作用最强,10月土壤呼吸作用最弱。影响旱生芦苇群落土壤呼吸的主导因子是温度,土壤呼吸与近地表空气温度以及土壤0～10、10～20、20～30cm温度均有显著相关性(P<0.01),而近地表空气温度和土壤表层温度对土壤呼吸的影响最大。在5—10月芦苇群落土壤呼吸温度敏感性Q10值为1.2～1.65,变异系数为15.4%。土壤含水量和近地表空气相对湿度不是影响该地区芦苇群落土壤呼吸的主要因素。     

Biophysics of malarial parasite exit from infected erythrocytes

Upon infection and development within human erythrocytes, P. falciparum induces alterations to the infected RBC morphology and bio-mechanical properties to eventually rupture the host cells through parasitic and host derived proteases of cysteine and serine families. We used previously reported broad-spectrum inhibitors (E64d, EGTA-AM and chymostatin) to inhibit these proteases and impede rupture to analyze mechanical signatures associated with parasite escape. Treatment of late-stage iRBCs with E64d and EGTA-AM prevented rupture, resulted in no major RBC cytoskeletal reconfiguration but altered schizont morphology followed by dramatic re-distribution of three-dimensional refractive index (3D-RI) within the iRBC. These phenotypes demonstrated several-fold increased iRBC membrane flickering. In contrast, chymostatin treatment showed no 3D-RI changes and caused elevated fluctuations solely within the parasitophorous vacuole. We show that E64d and EGTA-AM supported PV breakdown and the resulting elevated fluctuations followed non-Gaussian pattern that resulted from direct merozoite impingement against the iRBC membrane. Optical trapping experiments highlighted reduced deformability of the iRBC membranes upon rupture-arrest, more specifically in the treatments that facilitated PV breakdown. Taken together, our experiments provide novel mechanistic interpretations on the role of parasitophorous vacuole in maintaining the spherical schizont morphology, the impact of PV breakdown on iRBC membrane fluctuations leading to eventual parasite escape and the evolution of membrane stiffness properties of host cells in which merozoites were irreversibly trapped, recourse to protease inhibitors. These findings provide a comprehensive, previously unavailable, body of information on the combined effects of biochemical and biophysical factors on parasite egress from iRBCs.     

Effect of Vitamin D Supplementation on Cardiometabolic Risks and Health-Related Quality of Life among Urban Premenopausal Women in a Tropical Country – A Randomized Controlled Trial

Background

Many observational studies linked vitamin D to cardiometabolic risks besides its pivotal role in musculoskeletal diseases, but evidence from trials is lacking and inconsistent.

Aim

To determine whether Vitamin D supplementation in urban premenopausal women with vitamin D deficiency can improve cardiometabolic risks and health-related quality of life (HRQOL).

Design

A double-blind randomized controlled trial was conducted in Kuala Lumpur, Malaysia. A total of 192 vitamin D deficient (<50 nmol/l) premenopausal women were randomized to receive either vitamin D 50,000 IU or placebo once a week for 2 months and then monthly for 10 months. Primary outcomes were serum 25(OH)D, serum lipid profiles, blood pressure and HOMA-IR measured at baseline, 6 months and 12 months. HRQOL was assessed with SF-36 at baseline and 12 months.

Results

Ninety three and ninety-nine women were randomised into intervention and placebo groups respectively. After 12 months, there were significant differences in the serum 25(OH)D concentration (mean difference: 49.54; 95% CI: 43.94 to 55.14) nmol/l) and PTH levels (mean difference: −1.02; 95% CI: −1.67 to −0.38 pmol/l) in the intervention group compared to placebo group. There was significant difference between treatment group in both serum 25(OH)D and PTH. There was no effect of supplementation on HOMA-IR, serum lipid profiles and blood pressure (all p>0.05) between two groups. There was a small but significant improvement in HRQOL in the components of vitality (mean difference: 5.041; 95% CI: 0.709 to 9.374) and mental component score (mean difference: 2.951; 95% CI: 0.573 to 5.329) in the intervention group compared to placebo group.

Conclusion

Large and less frequent dosage vitamin D supplementation was safe and effective in the achievement of vitamin D sufficiency. However, there was no improvement in measured cardiometabolic risk factors in premenopausal women. Conversely vitamin D supplementation improves some components of HRQOL.

Trial Registration

Australian New Zealand Clinical Trial Registry ACTRN12612000452897     

Correlation analysis of Normalized Different Vegetation Index (NDVI) difference series and climate variables in the Xilingole steppe, China from 1983 to 1999

There is a crucial need in the study of global change to understand how terrestrial ecosystems respond to the climate system. It has been demonstrated by many researches that Normalized Different Vegetation Index (NDVI) time series from remotely sensed data, which provide effective information of vegetation conditions on a large scale with highly temporal resolution, have a good relation with meteorological factors. However, few of these studies have taken the cumulative property of NDVI time series into account. In this study, NDVI difference series were proposed to replace the original NDVI time series with NDVI difference series to reappraise the relationship between NDVI and meteorological factors. As a proxy of the vegetation growing process, NDVI difference represents net primary productivity of vegetation at a certain time interval under an environment controlled by certain climatic conditions and other factors. This data replacement is helpful to eliminate the cumulative effect that exist in original NDVI time series, and thus is more appropriate to understand how climate system affects vegetation growth in a short time scale. By using the correlation analysis method, we studied the relationship between NOAA/AVHRR ten-day NDVI difference series and corresponding meteorological data from 1983 to 1999 from 11 meteorological stations located in the Xilingole steppe in Inner Mongolia. The results show that: (1) meteorological factors are found to be more significantly correlation with NDVI difference at the biomass-rising phase than that at the falling phase; (2) the relationship between NDVI difference and climate variables varies with vegetation types and vegetation communities. In a typical steppe dominated by Leymus chinensis, temperature has higher correlation with NDVI difference than precipitation does, and in a typical steppe dominated by Stipa krylovii, the correlation between temperature and NDVI difference is lower than that between precipitation and NDVI difference. In a typical steppe dominated by Stipa grandis, there is no significant difference between the two correlations. Precipitation is the key factor influencing vegetation growth in a desert steppe, and temperature has poor correlation with NDVI difference; (3) the response of NDVI difference to precipitation is fast and almost simultaneous both in a typical steppe and desert steppe, however, mean temperature exhibits a time-lag effect especially in the desert steppe and some typical steppe dominated by Stipa krylovii; (4) the relationship between NDVI difference and temperature is becoming stronger with global warming. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(5): 753–765 [译自: 植物生态学报]     

Reductive transformation of parathion and methyl parathion by Bacillus sp.

Based on the results of phenotypic features, phylogenetic similarity of 16S rRNA gene sequences and BIOLOG test, a soil bacterium was identified as Bacillus sp. DM-1. Using either growing cells or a cell-free extract, it transformed parathion and methyl parathion to amino derivatives by reducing the nitro group. Pesticide transformation by a cell-free extract was specifically inhibited by three nitroreductase inhibitors, indicating the presence of nitroreductase activity. The nitroreductase activity was NAD(P)H-dependent, O₂-insensitive, and exhibited the substrate specificity for parathion and methyl parathion. Reductive transformation significantly decreased the toxicity of pesticides.     

ChREBP在肝细胞糖脂代谢中的作用

碳水化合物反应元件结合蛋白(carbohydrate response element binding protein,ChREBP)是一个在糖脂代谢过程中发挥重要作用的转录因子.ChREBP的分子量约为90kD,含有四个与其活性紧密相关的磷酸化位点.葡萄糖代谢旁路产物5-磷酸木酮糖可以激活蛋白磷酸酶2A,其促使ChREBP去磷酸化,去磷酸化的ChREBP进入细胞核,并与MLX形成异源二聚体ChREBP/MLX,ChREBP/MLX结合到靶基因启动子区域的ChRE上,激活靶基因的转录.ChREBP的靶基因主要是参与糖酵解和脂质合成的一些酶类,因而ChREBP的激活可促进葡萄糖向脂质转化.敲除ChREBP的小鼠虽可正常生长发育但其体内脂肪组织明显减少,同时肝中有大量糖原堆积而导致肝肿大.敲除ChREBP的ob/ob小鼠,体重及糖脂代谢紊乱也有明显改善.总之,现有的研究揭示ChREBP有可能成为治疗代谢综合征的一个新靶点.     

贺兰山岩羊种群生态及保护

作者于1994年11月、1995年7～8月和9～10月在宁夏贺兰山对岩羊种群生态进行了初步研究,发现贺兰山岩羊的最适生态分布见于海拔1801～2000 m,岩羊每天有两个活动高峰,分别为早晨和下午。在观察到的448只岩羊中,发现平均群大小为5.5只,2～8只为一群的占总数的70.8%。岩羊种群的雌雄性比为1∶1.2,雌幼比为1∶0.44,贺兰山的岩羊处于增长趋势。目前在贺兰山,影响岩羊生存的主要因素是偷猎、人为干扰和家畜竞争。     

Pseudomonas oryzae sp. nov. isolated from a paddy soil in South China

A Gram-staining-negative, rod-shaped and motile with several polar flagellums bacterium, designated WM-3^T, was isolated from a rice paddy soil in South China. Growth occurred with 0–3.0 % (w/v) NaCl (optimum 2.0 %), at pH 5.5–9.0 (optimum pH 7.0) and at 25–42 °C (optimum 30–37 °C) in liquid Reasoner’s 2A medium. Analysis of the 16S rRNA gene and gyrB gene sequences revealed that strain WM-3^T was most closely related to the type strains of the species Pseudomonas linyingensis and Pseudomonas sagittaria. Its sequence similarities with P. linyingensis CGMCC 1.10701^T and P. sagittaria JCM 18195^T were 97.4 and 97.3 %, respectively, for 16S rRNA gene, and were 94.1 and 94.2 %, respectively, for gyrB gene. DNA–DNA hybridization between strain WM-3^T and these two type strains showed relatedness of 35.6 and 30.9 %, respectively. G+C content of genomic DNA was 69.4 mol%. The whole-cell fatty acids mainly consisted of C_16:0 (30.0 %), C_16:1 ω6c and/or C_16:1 ω7c (19.3 %) and C_18:1 ω6c and/or C_18:1 ω7c (16.3 %). The results of phenotypic, chemotaxonomic and genotypic analyses clearly indicated that strain WM-3^T belongs to genus Pseudomonas but represents a novel species, for which the name Pseudomonas oryzae sp. nov. is proposed. The type strain is WM-3^T (=KCTC 32247^T =CGMCC 1.12417^T).