Reliable estimation of biochemical parameters from C3 leaf photosynthesis–intercellular carbon dioxide response curves

The Farquhar–von Caemmerer–Berry (FvCB) model of photosynthesis is a change‐point model and structurally overparameterized for interpreting the response of leaf net assimilation (A) to intercellular CO₂ concentration (Ci). The use of conventional fitting methods may lead not only to incorrect parameters but also several previously unrecognized consequences. For example, the relationships between key parameters may be fixed computationally and certain fits may be produced in which the estimated parameters result in contradictory identification of the limitation states of the data. Here we describe a new approach that is better suited to the FvCB model characteristics. It consists of four main steps: (1) enumeration of all possible distributions of limitation states; (2) fitting the FvCB model to each limitation state distribution by minimizing a distribution‐wise cost function that has desirable properties for parameter estimation; (3) identification and correction of inadmissible fits; and (4) selection of the best fit from all possible limitation state distributions. The new approach implemented theoretical parameter resolvability with numerical procedures that maximally use the information content of the data. It was tested with model simulations, sampled A/Ci curves, and chlorophyll fluorescence measurements of different tree species. The new approach is accessible through the automated website leafweb.ornl.gov.     

Control of the Life Cycle of Methanosarcina mazei S-6 by Manipulation of Growth Conditions

The morphology of Methanosarcina mazei was controlled by magnesium, calcium, and substrate concentrations and by inoculum size; these factors allowed manipulation of the morphology and interconversions between pseudosarcinal aggregates and individual, coccoid cells. M. mazei grew as aggregates in medium with a low concentration of catabolic substrate (either 50 mM acetate, 50 mM methanol, or 10 mM trimethylamine) unless Ca²⁺ and Mg²⁺ concentrations were high. Growth in medium high in Ca²⁺, Mg²⁺, and substrate (i.e., 150 mM acetate, 150 mM methanol, or 40 mM trimethylamine) converted pseudosarcinal aggregates to individual cocci. In such media, aggregates separated into individual cells which continued to grow exclusively as single cells during subsequent transfers. Conversion of single cells back to aggregates was complicated, because conditions which supported the aggregated morphology (e.g., low calcium or magnesium concentration) caused lysis of coccoid inocula. We recovered aggregates from coccoid cells by inoculating serial dilutions into medium high in calcium and magnesium. Cells from very dilute inocula grew into aggregates which disaggregated on continued incubation. However, timely transfer of the aggregates to medium low in calcium, magnesium, and catabolic substrates allowed continued growth as aggregates. We demonstrated the activity of the enzyme (disaggregatase) which caused the dispersion of aggregates into individual cells; disaggregatase was produced not only during disaggregation but also in growing cultures of single cells. Uronic acids, the monomeric constituents of the Methanosarcina matrix, were also produced during disaggregation and during growth as coccoids.     

芸苔属植物种子蛋白质及脂肪酸成分研究

本文对芸苔属(Brassica)19个植物种和变种的种子作了蛋白质、油脂及脂肪酸成分的系统分析。该属植物种子含蛋白质21.2—28.8%,油脂29.3—43.2%,均含有相同的至少13种脂肪酸成分,芥酸是其主要的也是特征脂肪酸,占总脂肪酸的24.2—52.0%。芥酸含量大于50%的种有紫菜苔、塌棵菜、白菜和花椰菜;笋子芥芥酸含量最低,为24.2—30.5%。     

赤眼蜂、白僵菌防治苹果害虫的研究

研究表明,利用松毛虫赤跟蜂防治苹果小卷叶蛾、梨小食心虫;白僵菌处理地面．防治桃小食心虫的寄生效果,均可达90％左右,防治效果优于化学农药．赤眼蜂应掌握在害虫始卵期开始放蜂．5天1次,连放4次,每亩总放蜂量12万头．白僵菌应在桃小食心虫越冬代幼虫出土始盛期和盛期各防治1次,每次每亩用菌剂(100亿孢子／g)2kg．加25％对硫磷微胶囊剂0．15kg．兑水150kg,在树冠下地面喷洒．喷后覆草是提高防治效果的关键．     

Metformin alleviates human cellular aging by upregulating the endoplasmic reticulum glutathione peroxidase 7

Metformin, an FDA‐approved antidiabetic drug, has been shown to elongate lifespan in animal models. Nevertheless, the effects of metformin on human cells remain unclear. Here, we show that low‐dose metformin treatment extends the lifespan of human diploid fibroblasts and mesenchymal stem cells. We report that a low dose of metformin upregulates the endoplasmic reticulum‐localized glutathione peroxidase 7 (GPx7). GP×7 expression levels are decreased in senescent human cells, and GPx7 depletion results in premature cellular senescence. We also indicate that metformin increases the nuclear accumulation of nuclear factor erythroid 2‐related factor 2 (Nrf2), which binds to the antioxidant response elements in the GPX7 gene promoter to induce its expression. Moreover, the metformin‐Nrf2‐GPx7 pathway delays aging in worms. Our study provides mechanistic insights into the beneficial effects of metformin on human cellular aging and highlights the importance of the Nrf2‐GPx7 pathway in pro‐longevity signaling.     

Diagnosis of <Emphasis Type="Italic">Clostridium difficile</Emphasis> infection using an UPLC–MS based metabolomics method

Introduction

The fecal metabolome of Clostridium difficile (CD) infection is far from being understood, particularly its non-volatile organic compounds. The drawbacks of current tests used to diagnose CD infection hinder their application.

Objective

The aims of this study were to find new characteristic fecal metabolites of CD infection and develop a metabolomics model for the diagnosis of CD infection.

Methods

Ultra-performance liquid chromatography-mass spectrometry (UPLC–MS) was used to characterize the fecal metabolome of CD positive and negative diarrhea and healthy control stool samples.

Results

Diarrhea and healthy control samples showed distinct clusters in the principal components analysis score plot, and CD positive group and CD negative group demonstrated clearer separation in a partial least squares discriminate analysis model. The relative abundance of sphingosine, chenodeoxycholic acid, phenylalanine, lysophosphatidylcholine (C16:0), and propylene glycol stearate was higher, and the relative abundance of fatty amide, glycochenodeoxycholic acid, tyrosine, linoleyl carnitine, and sphingomyelin was lower in CD positive diarrhea groups, than in the CD negative group. A linear discriminant analysis model based on capsiamide, dihydrosphingosine, and glycochenodeoxycholic acid was further constructed to identify CD infection in diarrhea. The leave-one-out cross-validation accuracy and area under receiver operating characteristic curve for the training set/external validation set were 90.00/78.57%, and 0.900/0.7917 respectively.

Conclusions

Compared with other hospital-onset diarrhea, CD diarrhea has distinct fecal metabolome characteristics. Our UPLC–MS metabolomics model might be useful tool for diagnosing CD diarrhea.

     

The Catalytically Inactive Mutation of the Ubiquitin-Conjugating Enzyme CDC34 Affects its Stability and Cell Proliferation

The ubiquitin proteasome system (UPS) plays important roles in the regulation of protein stability, localization, and activity. A myriad of studies have focused on the functions of ubiquitin ligases E3s and deubiquitinating enzymes DUBs due to their specificity in the recognition of downstream substrates. However, the roles of the most ubiquitin-conjugating enzymes E2s are not completely understood except that they transport the activated ubiquitin and form E2–E3 protein complexes. Ubiquitin-conjugating enzyme CDC34 can promote the degradation of downstream targets through the UPS whereas its non-catalytic functions are still elusive. Here, we find that mutation of the catalytically active cysteine to serine (C93S) results in the reduced ubiquitination, increased stability, and attenuated degradation rate of CDC34. Through semi-quantitative proteomics, we identify the CDC34-interacting proteins and discover that the wild-type and mutant proteins have many differentially interacted proteins. Detailed examination finds that some of them are involved in the regulation of gene expression, cell growth, and cell proliferation. Cell proliferation assay reveals that both the wild-type and C93S proteins affect the proliferation of a cancer cell line. Database analyses show that CDC34 mRNA is highly expressed in multiple cancers, which is correlated with the reduced patient survival rate. This work may help to elucidate the enzymatic and non-enzymatic functions of this protein and might provide additional insights for drug discovery targeting E2s.     

Polarization Conversion Based on Mie-Type Electromagnetically Induced Transparency (EIT) Effect in All-Dielectric Metasurface

In this paper, we propose an all-dielectric metasurface to realize the linear-to-circular polarization conversion of resonantly transmitted waves. This metasurface is composed of two intersection bars and four circle bricks. It has numerically demonstrated that the electromagnetic (EM) couplings between dielectric bar and bricks lead to the famous electromagnetically induced transparent (EIT) effect. Subsequently, based on Mie-type EIT resonances for two incident polarizations, the linear-to-circular polarization conversion occur at about 0.47 THz. More importantly, the thickness of our device is subwavelength and it is very transparency for EM waves. We also investigate the dependences of device performance on incident angles of EM waves and structure thicknesses. Device good performance is almost kept at about 0.47 THz for slightly incident angle tilts (θ ≤?30°) and tiny changes of substrate thickness. But device performance is strongly dependent on dielectric thickness. These results are very important for its integration to the existing terahertz devices, or its application to future polarization controls.     

Epstein-Barr病毒相关T/NK细胞淋巴瘤与B细胞淋巴瘤的临床分析

Epstein-Barr病毒(Epstein-Barr virus,EBV)是可导致人类感染的淋巴滤泡病毒,感染非常普遍。本研究通过对2013年1月-2016年12月于复旦大学附属华东医院就诊并确诊为淋巴瘤且伴有EBV感染的49例患者的临床资料进行回顾性分析,探讨EBV相关淋巴瘤患者的临床特点及生存情况。结果显示,49例EBV相关淋巴瘤患者中,18例为B细胞淋巴瘤,31例为T/NK细胞淋巴瘤。EBV相关B细胞淋巴瘤与T/NK细胞淋巴瘤患者之间白细胞、血小板、丙氨酸氨基转移酶、天冬氨酸氨基转移酶、乳酸脱氢酶、铁蛋白、纤维蛋白原、红细胞沉降率、C反应蛋白的差异有统计学意义(P<0.05)。中位随访5.0个月,49例患者的1个月、6个月、1年、3年生存率分别为 84.4%、59.8%、53.2%、40.3%。结果表明,与EBV相关B细胞淋巴瘤患者相比,EBV相关T/NK细胞淋巴瘤患者的肝功能损伤严重,更易合并噬血细胞综合征,生存期更短,但生存期差异无统计学意义。