Was improvement of spinach growth by nano-TiO2 treatment related to the changes of Rubisco activase?

Characterized by a photo—catalysis property, nano-anatase TiO₂ is closely related to photosynthesis of spinach. It could not only improve light absorbance, transformation from light energy to electron energy and active chemical energy, but also promote the activity of Rubiso activase of spinach. However, the relation between the activity of Rubiso activase and the growth of spinach promoted by nano-anatase TiO₂ treatment remains largely unclear. In this study, we find that the amount and the activity of Rubiso activase are obviously increased by nano-anatase TiO₂ treatment, which led to the great promotion of Rubsico carboxylation and the high rate of photosynthesis, thus improving of spinach growth. The significant enhancement of Rubiso activase activity of nano-anatase TiO₂ treated spinach is also accompanied by conformational changes as determined by spectroscopic analysis. But bulk TiO₂ effect is not as significant as nano-anatase TiO₂, as the grain size of nano-anatase TiO₂ (5 nm) is much smaller than that of bulk TiO₂, which entered spinach cell more easily.     

不同植被类型森林火灾及雷击火自组织临界性

利用黑龙江省大兴安岭林区呼中区 196 5～ 2 0 0 2年的雷击火数据、黑龙江省 1981～ 2 0 0 0年森林火灾数据及森林资源数据 ,对雷击造成的森林火灾的自组织临界性及不同植被类型条件下的自组织临界性作了研究 ,比较了在不同尺度和植被类型条件下火干扰的自组织临界性、自相似性 ,并与传统的森林火灾元胞自动机模型模拟的结果进行比较。结果表明 :中国黑龙江省不同森林类型的火干扰具有自组织临界行为 ,森林可燃物已经达到临界状态 ,其临界值在 1.8～ 2 .86之间 ,具有自相似性 ;当森林的面积过小时 ,森林火灾的“面积 -频率”分布曲线上会出现频率峰 ,表现出“有限面积效应”现象。     

Water-mediated responses of ecosystem carbon fluxes to climatic change in a temperate steppe

Global warming and a changing precipitation regime could have a profound impact on ecosystem carbon fluxes, especially in arid and semiarid grasslands where water is limited. A field experiment manipulating temperature and precipitation has been conducted in a temperate steppe in northern China since 2005. A paired, nested experimental design was used, with increased precipitation as the primary factor and warming simulated by infrared radiators as the secondary factor. The results for the first 2 yr showed that gross ecosystem productivity (GEP) was higher than ecosystem respiration, leading to net C sink (measured by net ecosystem CO(2) exchange, NEE) over the growing season in the study site. The interannual variation of NEE resulted from the difference in mean annual precipitation. Experimental warming reduced GEP and NEE, whereas increased precipitation stimulated ecosystem C and water fluxes in both years. Increased precipitation also alleviated the negative effect of experimental warming on NEE. The results demonstrate that water availability plays a dominant role in regulating ecosystem C and water fluxes and their responses to climatic change in the temperate steppe of northern China.     

Nano-Anatase Relieves the Inhibition of Electron Transport Caused by Linolenic Acid in Chloroplasts of Spinach

Linolenic acid is an inhibitor of electron transport in chloroplasts of higher plants. It has obvious effects on the structure and function of chloroplasts. In the present paper, we investigated the nano-anatase relieving the inhibition of photoreduction activity and oxygen evolution caused by linolenic acid in spinach chloroplasts. The results showed that linolenic acid in various concentrations could obviously reduce the whole chain electron transport and the photoreduction activity of two photosystems, especially on the oxidative reside and reduce reside of photosystem II (PS II). After adding nano-anatase to chloroplasts treated by linolenic acid, the whole chain electron transport rate, the photoreduction activity of two photosystems, and the oxygen evolution rate were increased significantly, indicating that nano-anatase could obviously decrease the inhibition of linolenic acid on the electron transport, photoreduction activity, and oxygen evolution of spinach chloroplasts.     

Influences of Lead (II) Chloride on the Nitrogen Metabolism of Spinach

Lead (Pb²⁺) is a well-known highly toxic element. The mechanisms of the Pb²⁺ toxicity are not well understood for nitrogen metabolism of higher plants. In this paper, we studied the effects of various concentrations of PbCl₂ on the nitrogen metabolism of growing spinach. The experimental results showed that Pb²⁺ treatments significantly decreased the nitrate nitrogen absorption and inhibited the activities of nitrate reductase, glutamate dehydrogenase, glutamine synthase, and glutamic–pyruvic transaminase of spinach, and inhibited the synthesis of organic nitrogen compounds such as protein and chlorophyll. However, Pb²⁺ treatments increased the accumulation of ammonium nitrogen in spinach cell. It implied that Pb²⁺ could inhibit inorganic nitrogen to be translated into organic nitrogen in spinach, thus led to the reduction in spinach growth.     

Oxidative Stress Induced by Lead in Chloroplast of Spinach

Seedlings of spinach were grown in Hoagland's medium containing 0, 20, 40, 60, 80, 100 microM PbCl2, respectively, for 4 weeks. Chloroplasts were assayed for overproduction of reactive oxygen species (ROS) such as superoxide radicals (O2(*-)) and hydrogen peoxide (H2O2) and of lipid peroxide (malonyldialdehyde) and for activities of the antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase and glutathione content, oxygen-evolving rate, and chlorophyll content. Increase in both ROS and lipid peroxide content and reduction in photosynthesis and activities of the antioxidant defense system indicated that spinach chloroplast underwent a stress condition due to an oxidative attack. Seedling growth cultivated in containing Pb2+ media was significantly inhibited. The results imply that spinach chloroplast was not able to tolerate the oxidative stress induced by Pb2+ due to having no effective antioxidant defense mechanism.     

Urinary Metabolomic Signatures in Obstructive Sleep Apnea through Targeted Metabolomic Analysis: A Pilot Study

Introduction

Obstructive sleep apnea (OSA) is very common sleep problem, and it is associated with serious morbidities such as cardiovascular diseases and metabolic diseases. Overnight polysomnography (PSG) is the gold standard test for OSA, but it is expensive and requires specific facilities and equipment. Thus, novel screening methods are needed for effective diagnosis and follow-up in OSA.

Objectives

The aims of the study were to investigate the urinary metabolic signatures and identify potential urine markers for OSA using a mass spectrometry (MS)-based assay for targeted metabolomics.

Methods

Urine samples were collected from 48 male subjects who visited a sleep clinic for suspicious OSA. All underwent overnight in-laboratory polysomnography. The Biocrates AbsoluteIDQ p180 kit was used for targeted metabolomics.

Results

Among the 86 metabolites quantified, three acylcarnitines, one biogenic amine, two glycerophospholipids, and two sphingomyelins were differently expressed in OSA patients [apnea-hypopnea index (AHI) ≥5] compared with control groups (AHI <5 and/or simple snoring with no other sleep disorders). Additional partial correlation and multivariate logistic regression analysis revealed that long-chain acylcarnitine C14:1, symmetric dimethylarginine, and sphingomyelin C18:1 might be potential biomarkers for OSA. Receiver operating characteristic analysis showed favorable predictive properties of these metabolites. Furthermore, a combination of the metabolites exceeding cutoff values yielded further improved sensitivity or specificity.

Conclusions

MS-based targeted metabolomics identified specific classes of urinary metabolites that were up-regulated in OSA patients. Further assessments in large populations are required to clarify the screening values of these metabolite markers.