Mutants impaired in vacuolar metal mobilization identify chloroplasts as a target for cadmium hypersensitivity in Arabidopsis thaliana

Cadmium (Cd) is highly toxic to plants causing growth reduction and chlorosis. It binds thiols and competes with essential transition metals. It affects major biochemical processes such as photosynthesis and the redox balance, but the connection between cadmium effects at the biochemical level and its deleterious effect on growth has seldom been established. In this study, two Cd hypersensitive mutants, cad1‐3 impaired in phytochelatin synthase (PCS1), and nramp3nramp4 impaired in release of vacuolar metal stores, have been compared. The analysis combines genetics with measurements of photosynthetic and antioxidant functions. Loss of AtNRAMP3 and AtNRAMP4 function or of PCS1 function leads to comparable Cd sensitivity. Root Cd hypersensitivities conferred by cad1‐3 and nramp3nramp4 are cumulative. The two mutants contrast in their tolerance to oxidative stress. In nramp3nramp4, the photosynthetic apparatus is severely affected by Cd, whereas it is much less affected in cad1‐3. In agreement with chloroplast being a prime target for Cd toxicity in nramp3nramp4, the Cd hypersensitivity of this mutant is alleviated in the dark. The Cd hypersensitivity of nramp3nramp4 mutant highlights the critical role of vacuolar metal stores to supply essential metals to plastids and maintain photosynthetic function under Cd and oxidative stresses.     

Agroecosystems and conservation of migratory waterbirds: importance of coastal pastures and factors influencing their use by wintering shorebirds

Coastal pastures are common agroecosystems adjacent to estuarine areas that can provide valuable habitat for wildlife, particularly for migratory shorebirds. Disentangling the factors that influence coastal pasture use by wintering shorebirds will provide new insights into its role for buffering human disturbances and habitat loss in intertidal areas. We examined whether numbers of two shorebirds (Eurasian curlew and Black-tailed godwit) foraging actively on coastal pastures was affected by weather conditions, tidal stage (low/high tide) and number of harvesters at intertidal areas throughout winter. Both species frequently used coastal pastures and most individuals foraged actively there. The average percentage of the total wintering population of curlews and godwits foraging on coastal pastures was 27.4 and 7.8 %, respectively, and was significantly higher during high tide compared to low tide. The number of harvesters on mudflats also had a positive significant effect in explaining the presence of curlews, and to a lesser extent for godwits, on coastal pastures, and accumulated rainfall had a positive effect for both species too. These supratidal areas were consistently used as alternative foraging grounds during low tide by curlews, as well as supplementary foraging areas during high tide by wintering populations of both large shorebirds. By supplementary foraging, wintering curlews, and probably godwits, seemed to compensate for a negative effect of the presence of harvesters on their foraging activity. We recommend managing of those coastal agricultural fields adjacent to intertidal foraging grounds in order to increase the availability of supratidal foraging habitats for declining shorebird populations. These habitats may thus have a beneficial role in sustaining populations of wintering shorebirds, but further studies are needed to estimate if birds can compensate for any shortfall in daily energy budget by supplementary foraging on coastal pastures, thus providing insights into whether they are involved in large-scale population regulation of migratory birds.     

Effects of curcumin on methyl methanesulfonate damage to mouse kidney

Methylmethane sulfonate (MMS) is an alkylating agent that may react with DNA and damage it. We investigated histological changes and apoptosis caused by MMS and the effects of curcumin on MMS treated mouse kidneys. Twenty-four mice were divided into four equal groups: controls injected with saline, a group injected with 40 mg/kg MMS, a group injected with 40 mg/kg MMS and given 100 mg/kg curcumin by gavage, and a group given 100 mg/kg curcumin by gavage. MMS caused congestion and vacuole formation, and elevated the apoptotic index significantly, but had no other effect on kidney tissue. Curcumin improved the congestion and vacuole formation caused by MMS and decreased the apoptotic index. Curcumin administered with MMS appears to decrease the deleterious effects of MMS on the kidney.     

Characterization of SPACR, a sialoprotein associated with cones and rods present in the interphotoreceptor matrix of the human retina: immunological and lectin binding analysis

Rod and cone photoreceptors project from the outer retinal surface into a carbohydrate-rich interphotoreceptor matrix (IPM). Unique IPM glycoconjugates are distributed around rods and cones. Wheat germ agglutinin (WGA) strongly decorates the rod matrix domains and weakly decorates the cone matrix domains. This study characterizes the major WGA-binding glycoprotein in the human IPM, which we refer to as SPACR (sialoprotein associated with cones and rods). SPACR, which has a molecular weight of 147 kDa, was isolated and purified from the IPM by lectin affinity chromatography. A polyclonal antibody to SPACR was prepared that colocalizes in tissue preparations with WGA-binding domains in the IPM. Sequential digestion of SPACR with N- and O- glycosidases results in a systematic increase in electrophorectic mobility, indicating the presence of both N- and O-linked glycoconjugates. Complete deglycosylation results in a reduction in the relative molecular mass of SPACR by about 30%. Analysis of lectin binding allowed us to identify some of the structural characteristics of SPACR glycoconjugates. Treatment with neuraminidase exposes Galbeta1- 3GalNAc disaccharide as indicated by positive peanut agglutinin (PNA) staining, accompanied by the loss of WGA staining. Maackia amurensis agglutinins (MAA-1 and MAA-2), specific for sialic acid in alpha2-3 linkage to Gal, bind SPACR, while Sambucus nigra agglutinin (SNA), specific for alpha2-6 linked sialic acid, does not, indicating that the dominant glycoconjugate determinant on SPACR is the O-linked carbohydrate, NeuAcalpha2-3Galbeta1-3GalNAc. The abundance of sialic acid in SPACR suggests that this glycoprotein may contribute substantially to the polyanionic nature of the IPM. The carbohydrate chains present on SPACR could also provide sites for extensive crosslinking and participate in the formation of the ordered IPM lattice that surrounds the elongate photoreceptors projecting from the outer retinal surface.      

Elucidating mechanistic principles underpinning eukaryotic translation initiation using quantitative fluorescence methods

Eukaryotic translation initiation is an intricate process involving at least 11 formally classified eIFs (eukaryotic initiation factors), which, together with the ribosome, comprise one of the largest molecular machines in the cell. Studying such huge macromolecular complexes presents many challenges which cannot readily be overcome by traditional molecular and structural methods. Increasingly, novel quantitative techniques are being used to further dissect such complex assembly pathways. One area of methodology involves the labelling of ribosomal subunits and/or eIFs with fluorophores and the use of techniques such as FRET (F?rster resonance energy transfer) and FA (fluorescence anisotropy). The applicability of such techniques in such a complex system has been greatly enhanced by recent methodological developments. In the present mini-review, we introduce these quantitative fluorescence methods and discuss the impact they are beginning to have on the field.     

每搏量变异度在围手术期容量治疗监测中的应用

每搏量变异度是动态的容量监测指标.机械通气患者心肺的相互作用是每搏量变异度的产生基础,通过动脉压力波形分析技术可以进行连续监测.每搏量变异度能够准确预测容量治疗反应,与静态的血流动力学参数相比,对于优化心输出量和组织氧供更有优势,但也存在一定的局限性.每搏量变异度受多种因素影响且不能用于自主呼吸和心律失常的患者.临床应用时应该综合考虑其影响因素,结合其他的指标和方法指导容量治疗.     

A quantitative inventory of global soniferous fish diversity

Reviews in Fish Biology and Fisheries - Sound production in fishes is vital to an array of behaviors including territorial defense, reproduction, and competitive feeding. Unfortunately, recent...     

Validation of daily increments and a marine‐entry check in the otoliths of sockeye salmon Oncorhynchus nerka post‐smolts

Juvenile sockeye salmon Oncorhynchus nerka that were reared and smolted in laboratory conditions were found to produce otolith daily increments, as well as a consistently visible marine‐entry check formed during their transition to salt water. Field‐collected O. nerka post‐smolts of an equivalent age also displayed visible checks; however, microchemistry estimates of marine‐entry date using Sr:Ca ratios differed from visual estimates by c. 9 days suggesting that microstructural and microchemical processes occur on different time scales.     

白马雪山国家级自然保护区典型森林生态系统服务

生态系统服务是近年来生态学研究的热点领域,对关键区域生态系统服务的研究具有重要意义.云南省白马雪山国家级自然保护区地处青藏高原南延部分,拥有独特的地理位置,是生物多样性保护的热点区域.本文对该保护区森林生态系统的生物量与生产力、水源涵养、营养物质循环等3项服务的功能量进行了评估.结果表明:保护区森林总生物量2215.86×104t,生产力171.84×104t·a-1;水源涵养量11964.56×104m3;N、P、K年吸收量分别为26025.94t、2638.57t、12016.85 t.研究表明,保护区森林生态效益显著,对于维持当地以及周边地区的生态安全具有重要意义.