Scaling carbon dioxide and water vapour exchange from leaf to canopy in a deciduous forest. I. Leaf model parametrization

In order to parametrize a leaf submodel of a canopy level gas-exchange model, a series of photosynthesis and stomatal conductance measurements were made on leaves of white oak (Quercus alba L.) and red maple (Acer rubrum L.) in a mature deciduous forest near Oak Ridge, TN. Gas-exchange characteristics of sun leaves growing at the top of a 30 m canopy and of shade leaves growing at a depth of 3–4 m from the top of the canopy were determined. Measured rates of net photosynthesis at a leaf temperature of 30°C and saturating photosynthetic photon flux density, expressed on a leaf area basis, were significantly lower (P = 0.01; n = 8) in shade leaves (7.9μmol m^?2 s^?1) than in sun leaves (11–5μmol m^?2 s^?1). Specific leaf area increased significantly with depth in the canopy, and when photosynthesis rates were expressed on a dry mass basis, they were not significantly different for shade and sun leaves. The percentage leaf nitrogen did not vary significantly with height in the canopy; thus, rates expressed on a per unit nitrogen basis were also not significantly different in shade and sun leaves. A widely used model integrating photosynthesis and stomatal conductance was parametrized independently for sun and shade leaves, enabling us to model successfully diurnal variations in photosynthesis and evapotranspiration of both classes of leaves. Key photosynthesis model parameters were found to scale with leaf nitrogen levels. The leaf model parametrizations were then incorporated into a canopy-scale gas-exchange model that is discussed and tested in a companion paper (Baldocchi & Harley 1995, Plant, Cell and Environment 18, 1157–1173).     

影响白腐真菌AH28-2菌株漆酶合成的因子和发酵条件

White-rot fungus AH28-2, a newly isolated strain, produced effectively laccase by induction when grown on a synthetic medium. Aromatic compounds of low molecular weight had an inducing influence on laccase production and its isoenzyme compositions. The using of o-toluidine or syringic acid had the best inducing effect. Cu2+ concentration in medium had distinguished effect on laccase production. Enzyme activity was notably increased by Cu2+ and reached the maximum when Cu2+ final concentration was 5 mumol/L. Mn2+ inhibited the synthesis of laccase. Carbon and nitrogen limitation were not beneficial to laccase synthesis, while high nutrient organic medium was beneficial to the growth of cell and the synthesis of laccase. Using cellobiose as the sole carbon source, the highest level enzyme activity reached 82,923. 7 u/L under the condition of optimum fermentation with ABTS as substrate. This enzyme activity was 2.9-fold higher compared to the reported data on international references in recent years.     

自制载体冷冻小鼠原核期胚胎效果分析

目的探讨自制冷冻载体冷冻保存昆明小鼠体内原核期胚胎的可行性。方法首先,比较了两种流行的商业化载体:开放式拉长麦管(open pulled straw,OPS)和冷冻帽(cryotop)开展小鼠原核胚玻璃化冷冻保存效果。其次,以cryotop为对照,利用自制简易载体(cryotip)开展小鼠原核期胚胎的玻璃化冷冻保存。之后,利用ANOVA对各组胚胎在复苏后的体外培养卵裂率、囊胚率进行统计分析。结果 OPS和cryotop两组之间,胚胎在玻璃化冷冻/复苏后发育的2-细胞率、4-细胞率和囊胚率差异均无显著性(P0.05),但cryotop冷冻效果更接近对照组;cryotip玻璃化冷冻载体与cryotop相比,胚胎复苏后各组差异均无显著性(P0.05),数值上除了2-细胞发育率外,cryotip其他几项结果都稍微高于cryotop组。结论 OPS,cryotop,cryotip冷冻保存昆明小鼠体内原核期胚胎均是可行的;cryotop在冷冻效果上要优于OPS,笔者自制的cryotip因其成本低,制作简单,操作安全可靠,在实验中替代昂贵的商业化载体OPS和cryotop是可行的。     

Cell wall structure of secreted laccase-silenced strain in Lentinula edodes

Laccase1 (Lcc1) is abundantly secreted from vegetative mycelia into culture medium by Lentinula edodes. Down-regulation of lcc1 in L. edodes results in abnormal hyphal structure and thinner cell wall in mycelia. In this study, we observed the effects of Lcc1 on the hyphal morphology and cell wall structure of L. edodes. A thick cell wall and fibrous layer were clearly observed in the lcc1-silenced strain ivrL1#32, when purified Lcc1 (0.1 mU/mL) was added to the culture medium. The ratio of cell wall polysaccharide contents was compared between the ivrL1#32 strain and the wild-type (WT) strain SR-1, revealing that levels of the alkali soluble β-1,3-1,6-glucan were significantly lower in the lcc1-silenced strain than in the WT strain. Chronological analysis revealed that chitin content in the cell wall did not increase over time, but that the alkali soluble β-1,3-1,6-glucan content increased after Lcc1 secretion in the WT. Taken together, these data suggest that the increased level of β-1,3-1,6-glucan induced by Lcc1 in the mycelial cell wall contributes to increased cell wall thickness and strength.     

Cadmium induced MTs synthesis via oxidative stress in yeast Saccharomyces cerevisiae

Lignan complex has been isolated from flaxseed. It has been shown to reduce serum lipids and the extent of hypercholesterolemic atherosclerosis. However, it is not known whether the chronic use of lignan complex has any adverse effects on the hemopoietic system. The effects of lignan complex (40 mg/kg body wt orally daily for 2 months) on the red blood cells (RBC) count, mean corpuscular volume (MCV), red cell distribution width (RDW), hematocrit (Hct), hemoglobin (Hb), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and counts of white blood cell (WBC), granulocytes, lymphocytes, monocytes and platelet, and platelet volume were investigated in normo- and hypercholesterolemic rabbits. The results show that lignan complex had no adverse effects of counts of RBC, WBC, granulocytes, lymphocytes, monocytes and platelet in both the normo- and hyper-cholesterolemic rabbits. The values for MCV, RDW, Hct, Hb, MCH, MCHC, and platelet volume were similar in lignan complex-treated or untreated normo- and hypercholesterolemic rabbits. It is concluded that chronic use of lignan complex had no adverse effects on the hemopoietic system. (Mol Cell Biochem 270: 139–145, 2005)     

河北异小杆线虫一品系的分类鉴定及其对蛴螬致病力的测定

昆虫病原线虫是一种有应用潜力的地下害虫生物防治因子。本研究利用形态学特征和ITS-rDNA分析方法对从河北省沧州分离的异小杆线虫一品系进行了鉴定, 并在室内测定比较了其对蛴螬的致病力。通过对该线虫侵染期幼虫和雄性成虫主要形态学特征的参数测量, 发现其与嗜菌异小杆线虫Heterorhabditis bacteriophora的形态特征最为相近;同时ITS1-rDNA序列比对和系统发育学分析结果显示其与嗜菌异小杆线虫亲缘关系最近。结合形态学和分子生物学特征, 确定该线虫为嗜菌异小杆线虫沧州品系。该线虫对蛴螬（华北大黑鳃金龟Holotrichia oblita、暗黑鳃金龟H. parallela和铜绿丽金龟Anomala corpulenta 3种金龟子的2龄幼虫）的致病力研究结果表明：处理72 h后, 暗黑鳃金龟幼虫死亡率显著高于另外两种金龟子幼虫 (P<0.05);处理120 h后, 暗黑鳃金龟和铜绿丽金龟幼虫的死亡率分别达到93.3%和80.0%, 二者无显著差异 (P>0.05), 可见该线虫对它们有较强的致病力。不同线虫对暗黑鳃金龟幼虫的致病力结果显示, 嗜菌异小杆线虫沧州品系侵染96 h后, 幼虫的死亡率显著高于Steinernema feltiae和S. longicaudum两种线虫的处理 (P<0.05) , 说明嗜菌异小杆线虫沧州品系的致病力显著高于另外两种线虫。     

荧光粉激发型LED光对拟南芥生长发育的影响

在室内人工光源照射条件下, 探究150 μmol∙m^-2·s^-1光强下不同比例的红蓝光对拟南芥(Arabidopsis thaliana)生长发育的影响。以哥伦比亚(Columbia-0)野生型拟南芥为研究对象, 采用荧光粉激发型LED作为植物生长光源, 以SrSiAlN₃为红色基底, 调节荧光粉添加量获得不同红蓝光谱, 考察不同光照条件下拟南芥萌发率、根长、株高、叶绿素含量和相对电导率等参数的变化规律。结果表明, 在荧光粉激发型LED光照调节下的拟南芥具有更高的萌发率、根长、株高、叶绿素含量和相对电导率, 且在红蓝光质比为2:1时萌发率(95.63%)和叶绿素含量(26.7)最高; 在红蓝光质比为4:5时根长(4.19 cm)较长; 在红蓝光质比为4:1时株高(15.5 cm)较高; 在红蓝光质比为4:5时相对电导率(40.5 S·m^-1)较大。研究结果表明相对平衡的光质(红蓝光质比为4:1)有利于拟南芥生长发育, 且减少蓝光比例对根系生长及叶绿素积累有一定的促进作用。研究表明不同光谱对模式植物拟南芥的生长发育有较明显的影响, 改变光谱组成可以对植物的生长发育起不同程度的调控作用。     

Lipid metabolism in mammalian tissues and its control by retinoic acid

Evidence has accumulated that specific retinoids impact on developmental and biochemical processes influencing mammalian adiposity including adipogenesis, lipogenesis, adaptive thermogenesis, lipolysis and fatty acid oxidation in tissues. Treatment with retinoic acid, in particular, has been shown to reduce body fat and improve insulin sensitivity in lean and obese rodents by enhancing fat mobilization and energy utilization systemically, in tissues including brown and white adipose tissues, skeletal muscle and the liver. Nevertheless, controversial data have been reported, particularly regarding retinoids' effects on hepatic lipid and lipoprotein metabolism and blood lipid profile. Moreover, the molecular mechanisms underlying retinoid effects on lipid metabolism are complex and remain incompletely understood. Here, we present a brief overview of mammalian lipid metabolism and its control, introduce mechanisms through which retinoids can impact on lipid metabolism, and review reported activities of retinoids on different aspects of lipid metabolism in key tissues, focusing on retinoic acid. Possible implications of this knowledge in the context of the management of obesity and the metabolic syndrome are also addressed. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.     

Biophysical insights into the interaction of hen egg white lysozyme with therapeutic dye clofazimine: modulation of activity and SDS induced aggregation of model protein

The present study details the binding process of clofazimine to hen egg white lysozyme (HEWL) using spectroscopy, dynamic light scattering, transmission electron microscopy (TEM), and molecular docking techniques. Clofazimine binds to the protein with binding constant (K_b) in the order of 1.57?×?10⁴ at 298 K. Binding process is spontaneous and exothermic. Molecular docking results suggested the involvement of hydrogen bonding and hydrophobic interactions in the binding process. Bacterial cell lytic activity in the presence of clofazimine increased to more than 40% of the value obtained with HEWL only. Interaction of the drug with HEWL induced ordered secondary structure in the protein and molecular compaction. Clofazimine also effectively inhibited the sodium dodecyl sulfate (SDS) induced amyloid formation in HEWL and caused disaggregation of preformed fibrils, reinforcing the notion that there is involvement of hydrophobic interactions and hydrogen bonding in the binding process of clofazimine with HEWL and clofazimine destabilizes the mature fibrils. Further, TEM images confirmed that fibrillar species were absent in the samples where amyloid induction was performed in the presence of clofazimine. As clofazimine is a drug less explored for the inhibition of fibril formation of the proteins, this study reports the inhibition of SDS-induced amyloid formation of HEWL by clofazimine, which will help in the development of clofazimine-related molecules for the treatment of amyloidosis.     

Signatures of local adaptation in candidate genes of oaks (Quercus spp.) with respect to present and future climatic conditions

Testing how populations are locally adapted and predicting their response to their future environment is of key importance in view of climate change. Landscape genomics is a powerful approach to investigate genes and environmental factors involved in local adaptation. In a pooled amplicon sequencing approach of 94 genes in 71 populations, we tested whether >3500 single nucleotide polymorphisms (SNPs) in the three most common oak species in Switzerland (Quercus petraea, Q. pubescens, Q. robur) show an association with abiotic factors related to local topography, historical climate and soil characteristics. In the analysis including all species, the most frequently associated environmental factors were those best describing the habitats of the species. In the species‐specific analyses, the most important environmental factors and associated SNPs greatly differed among species. However, we identified one SNP and seven genes that were associated with the same environmental factor across all species. We finally used regressions of allele frequencies of the most strongly associated SNPs along environmental gradients to predict the risk of nonadaptedness (RONA), which represents the average change in allele frequency at climate‐associated loci theoretically required to match future climatic conditions. RONA is considerable for some populations and species (up to 48% in single populations) and strongly differs among species. Given the long generation time of oaks, some of the required allele frequency changes might not be realistic to achieve based on standing genetic variation. Hence, future adaptedness requires gene flow or planting of individuals carrying beneficial alleles from habitats currently matching future climatic conditions.