电磁感应电导仪（EM38）测定土壤含盐量的研究

利用EM38型电磁感应电导仪(EM38)在野外原位测定土壤电磁感应电导率(EM),是一种快速简便测定土壤含盐量的新方法。将EM38水平放置在地表以上不同高度,仪器EM读数随高度的变化与不同深度土层的盐分含量分布有关。室内用电导法测定不同深度土层土壤水浸液(水:土=5:1)的电导率(EC)。两种电导率(EM和EC)之间的相关分析表明,地面不同高度EM与不同深度土层EC具有显著相关性。根据EM建立了EC的回归方程,代入相应的EM值即可求出不同深度土层的EC和含盐量。     

Activities of the EM10 protein from Echinococcus multilocularis in cultured mammalian cells demonstrate functional relationships to ERM family members

The ezrin-radixin-moesin (ERM) homolog EM10 is expressed by the larval stage of the parasite E. multilocularis and shows 46.9% overall identity in the primary structure with human ezrin. To determine whether EM10 has similar activities to ERM proteins, we investigated properties of the protein expressed in mammalian cells. In particular, we transiently expressed haemagglutinin-tagged (HA-tagged) versions of the full-length EM10 as well as the amino- and the carboxy-terminal halves of EM10 in HtTA-1 cells. In addition we stably transfected NIH-3T3 cells with untagged full-length EM10. The data demonstrate that EM10 polypeptides behave like their corresponding portions of radixin when transiently expressed in mammalian cells. The full-length and amino-terminal EM10 polypeptides were localized to cortical structures. Cells expressing the carboxy-terminal polypeptide of EM10 showed long actin-filled protrusions. Cells expressing full-length EM10 showed a reduction in endogenous moesin-staining at cortical structures. In stably transfected NIH-3T3 cells EM10 was not crisply localized but rather was diffuse throughout the cytoplasm. These cells showed a conspicuous loss of stress-fibers, a phenotype that was not seen in analogous experiments with ERM proteins. The results demonstrate both similarities and differences between the functional properties of EM10 and ERM proteins expressed in vertebrate cells.     

Application of dynamic metabolic flux analysis for process modeling: Robust flux estimation with regularization,confidence bounds,and selection of elementary modes

In macroscopic dynamic models of fermentation processes, elementary modes (EM) derived from metabolic networks are often used to describe the reaction stoichiometry in a simplified manner and to build predictive models by parameterizing kinetic rate equations for the EM. In this procedure, the selection of a set of EM is a key step which is followed by an estimation of their reaction rates and of the associated confidence bounds. In this paper, we present a method for the computation of reaction rates of cellular reactions and EM as well as an algorithm for the selection of EM for process modeling. The method is based on the dynamic metabolic flux analysis (DMFA) proposed by Leighty and Antoniewicz (2011, Metab Eng, 13(6), 745–755) with additional constraints, regularization and analysis of uncertainty. Instead of using estimated uptake or secretion rates, concentration measurements are used directly to avoid an amplification of measurement errors by numerical differentiation. It is shown that the regularized DMFA for EM method is significantly more robust against measurement noise than methods using estimated rates. The confidence intervals for the estimated reaction rates are obtained by bootstrapping. For the selection of a set of EM for a given st oichiometric model, the DMFA for EM method is combined with a multiobjective genetic algorithm. The method is applied to real data from a CHO fed-batch process. From measurements of six fed-batch experiments, 10 EM were identified as the smallest subset of EM based upon which the data can be described sufficiently accurately by a dynamic model. The estimated EM reaction rates and their confidence intervals at different process conditions provide useful information for the kinetic modeling and subsequent process optimization.     

Selective use of electron microscopy in fine needle aspiration cytology

The utility of electron microscopy (EM) applied to fine needle aspiration (FNA) biopsy specimens was analyzed in order to determine the role and the diagnostic contribution of the EM examination. A rapid stain (Diff-Quik) was used to obtain a preliminary diagnostic impression and to assure the adequacy of the EM specimen for problematic cases. Our experience suggests that EM is being relied upon with greater frequency in the study of FNA specimens because it is an accurate and cost-effective diagnostic procedure. The use of a rapid interpretation (Diff-Quik stain) enhances the quality of the EM specimen and, as in surgical pathology, the EM examination increases the accuracy and specificity of the FNA biopsy diagnosis.     

Strong differences in Quercus robur-associated ectomycorrhizal fungal communities along a forest-city soil sealing gradient

Ectomycorrhizal fungi (EM) that associate with tree roots in a symbiotic relationship may be crucial in mediating tree health in urban environments, but research on the effects of urbanization on EM communities is very limited so far. Here, we compared EM communities of adult pedunculate oaks (Quercus robur) between urban and forest environments, and assessed the effect of soil sealing around the trees on their EM community composition and EM diversity. We sampled 32 oak individuals across 4 sampling classes (Street, Lane, Park and Forest), and we characterized their EM communities using 454 amplicon pyrosequencing. The EM communities were not nested but they were significantly different between all sampling classes, with a very strong community differentiation between forest and urban trees. There were indications that EM richness declined with increasing sealed soil surface, with a significant effect of sampling class on estimated EM richness and diversity. We also identified indicator EM of the different sampling classes. The most important soil factor affecting EM community composition was pH, followed by plant available phosphorus, total nitrogen content and organic matter. Our results may have important implications when developing EM inocula for managing tree health in urban environments.     

Increased ectomycorrhizal fungal abundance after long-term fertilization and warming of two arctic tundra ecosystems

Shrub abundance is expected to increase with enhanced temperature and nutrient availability in the Arctic, and associated changes in abundance of ectomycorrhizal (EM) fungi could be a key link between plant responses and longer-term changes in soil organic matter storage. This study quantifies the response in EM fungal abundance to long-term warming and fertilization in two arctic ecosystems with contrasting responses of the EM shrub Betula nana. Ergosterol was used as a biomarker for living fungal biomass in roots and organic soil and ingrowth bags were used to estimate EM mycelial production. We measured 15N and 13C natural abundance to identify the EM-saprotrophic divide in fungal sporocarps and to validate the EM origin of mycelia in the ingrowth bags. Fungal biomass in soil and EM mycelial production increased with fertilization at both tundra sites, and with warming at one site. This was caused partly by increased dominance of EM plants and partly by stimulation of EM mycelial growth. We conclude that cycling of carbon and nitrogen through EM fungi will increase when strongly nutrient-limited arctic ecosystems are exposed to a warmer and more nutrient-rich environment. This has potential consequences for below-ground litter quality and quantity, and for accumulation of organic matter in arctic soils.     

外生菌根菌与森林树木的相互关系

生态系统的每个过程都伴随着各种微生物的活动,其中最重要的功能群之一是菌根真菌(菌根菌)。一般认为,菌根菌是自然界多数植物生存最基本的组成部分,陆地上约90％以上的高等植物都具有菌根菌。这些菌类的菌丝体与植物根系结合形成菌根,使植物生长成为可能,使不同种类植物的根系联在一起。根据菌根菌入侵植物根系的方式及菌根的形态特征,菌根可分为外生菌根、内生菌根和内外生菌根3组共7种类型。外生菌根主要出现在松科、桦木科、壳斗科等树种的森林生态系统中,在根系表面形成菌丝鞘,部分菌丝进入根系皮层细胞间隙形成哈氏网表面。菌根菌剂在森林经营中得到广泛地应用。外生菌根菌对森林树木的作用可归纳为：1)促进造林或育苗成活与生长;2)提高森林生态系统中植物的多样性、稳定性和生产力;3)对森林生态系统的综合效应,主要表现在增加植物一土壤联结,改善土壤结构,促进土壤微生物,增强植物器官的功能;4)抗拮植物根部病害病原菌等。树木与菌根菌相互关系研究主要包括：1)菌根共生的机理;2)菌根菌在退化森林生态系统恢复与改造中的作用;3)菌根菌的分布格局与森林生态系统服务功能的关系;4)菌根菌对森林生态系统的综合效应,如菌根菌与森林植物群落结构、物种多样性以及森林系统稳定性和生产力的研究。     

Electron microscopy: essentials for viral structure, morphogenesis and rapid diagnosis

Electron microscopy(EM) should be used in the front line for detection of agents in emergencies and bioterrorism,on accounts of its speed and accuracy.However,the number of EM diagnostic laboratories has decreased considerably and an increasing number of people encounter difficulties with EM results.Therefore,the research on viral structure and morphology has become important in EM diagnostic practice.EM has several technological advantages,and should be a fundamental tool in clinical diagnosis of viruses,particularly when agents are unknown or unsuspected.In this article,we review the historical contribution of EM to virology,and its use in virus differentiation,localization of specific virus antigens,virus-cell interaction,and viral morphogenesis.It is essential that EM investigations are based on clinical and comprehensive pathogenesis data from light or confocal microscopy.Furthermore,avoidance of artifacts or false results is necessary to exploit fully the advantages while minimizing its limitations.     

The effects of endomorphins and diprotin A on striatal dopamine release induced by electrical stimulation-an in vitro superfusion study in rats

The endomorphins (EM1: Tyr-Pro-Trp-Phe-NH2, and EM2: Tyr-Pro-Phe-Phe-NH2) are recently discovered endogenous ligands for mu-opioid receptors (MORs) with role of neurotransmitters or neuromodulators in mammals. Cessation of their physiological action may be effected through rapid enzymatic degradation by the dipeptidyl-peptidase IV (DPPIV) found in the brain synaptic membranes. An in vitro superfusion system was utilized to investigate the actions of EM1, EM2 and specific DPPIV inhibitor diprotin A on the striatal release of dopamine (DA) induced by electrical stimulation in rats. The involvement of the different MORs (MOR1 and MOR2) in this process was studied by pretreatment with MOR antagonists beta-funaltrexamine (a MOR1 and MOR2 antagonist) and naloxonazine (a MOR1 antagonist). EM1 significantly increased the tritium-labelled dopamine DA release induced by electrical stimulation. EM2 was effective only when the slices were pretreated with diprotin A. beta-Funaltrexamine antagonized the stimulatory effects of both EM1 and EM2. The administration of naloxonazine did not appreciably influence the action of EM1, but blocked the action of EM2, at least when the slices were pretreated with diprotin A. These data suggest that both EM1 and EM2 increase DA release from the striatum and, though diprotin A does not affect the action of EM1, it inhibits the enzymatic degradation of EM2. The DA-stimulating action induced by EM1 seems to be mediated by MOR2, while that evoked by EM2 appears to be transmitted by MOR1.     

Recovery from sublethal and potentially lethal damage in an X-ray-sensitive CHO cell

It has been suggested that DNA strand breaks are the molecular lesions responsible for radiation-induced lethality and that their repair is the basis for the recovery of irradiated cells from sublethal and potentially lethal damage. EM9 is a Chinese hamster ovary cell line that is hypersensitive to killing by X rays and has been reported to have a defect in the rate of rejoining of DNA single-strand breaks. To establish the importance of DNA strand-break repair in cellular recovery from sublethal and potentially lethal X-ray damage, those two parameters, recovery from sublethal and potentially lethal damage, were studied in EM9 cells as well as in EM9's parental repair-proficient strain, AA8. As previously reported, EM9 is the more radiosensitive cell line, having a D0 of 0.98 Gy compared to a D0 of 1.56 Gy for AA8 cells. DNA alkaline elution studies suggest that EM9 cells repair DNA single-strand breaks at a slower rate than AA8 cells. Neutral elution analysis suggests that EM9 cells also repair DNA double-strand breaks more slowly than AA8 cells. All of these data are consistent with the hypothesis that DNA strand-break ligation is defective in EM9 cells and that this defect accounts for increased radiosensitivity. The kinetics and magnitude of recovery from sublethal and potentially lethal damage, however, were similar for both EM9 and AA8 cells. Six-hour recovery ratios for sublethal damage repair were found to be 2.47 for AA8 cells and 1.31 for EM9 cells. Twenty-four-hour recovery ratios for potentially lethal damage repair were 3.2 for AA8 and 3.3 for EM9 cells. Both measurements were made at approximately equitoxic doses. Thus, the defect in EM9 cells that confers radiosensitivity and affects DNA strand-break rejoining does not affect sublethal damage repair or potentially lethal damage repair.     

Developments,applications, and prospects of cryo‐electron microscopy

Cryo‐electron microscopy (cryo‐EM) is a structural biological method that is used to determine the 3D structures of biomacromolecules. After years of development, cryo‐EM has made great achievements, which has led to a revolution in structural biology. In this article, the principle, characteristics, history, current situation, workflow, and common problems of cryo‐EM are systematically reviewed. In addition, the new development direction of cryo‐EM—cryo‐electron tomography (cryo‐ET), is discussed in detail. Also, cryo‐EM is prospected from the following aspects: the structural analysis of small proteins, the improvement of resolution and efficiency, and the relationship between cryo‐EM and drug development. This review is dedicated to giving readers a comprehensive understanding of the development and application of cryo‐EM, and to bringing them new insights.     

An Engineered Endomorphin-2 Gene for Morphine Withdrawal Syndrome

An optimal therapeutics to manage opioid withdrawal syndrome is desired for opioid addiction treatment. Down-regulation of endogenous endomorphin-2 (EM2) level in the central nervous system after continuous morphine exposure was observed, which suggested that increase of EM2 could be an alternative novel method for opioid dependence. As a short peptide, the short half-life of EM2 limits its clinical usage through conventional administration. In the present study, we engineered an EM2 gene using a signal peptide of mouse growth factor for an out-secretory expression of EM2 and an adenovirus as a vector, which ultimately sustained the release of EM-2. After administration of the adenovirus in central nervous system, a sustained increase of EM2 level in the cerebral spinal fluid (CSF) was observed along with a reduction of morphine withdrawal syndrome. These findings suggest that the engineered EM2 gene delivered to the central nervous system could be a novel therapeutics for withdrawal syndrome in opioid dependent subjects.     

Asymmetrical over-infection as a process of plant virus emergence

Disentangling the role of epidemiological factors in plant pathogen emergences is a prerequisite to identify the most likely future invaders. An example of emergence was recently observed in France: in 10 years, “classic” (CL) strains of Watermelon mosaic virus (WMV) were displaced at a regional scale by newly introduced “emerging” (EM) strains. Here we analyse a 3 years dataset describing the co-dynamics of CL and EM strains at field scale using state-space models estimating jointly: (i) probabilities of primary and secondary infection and (ii) probabilities of over-infecting with a CL [EM] strain a plant already infected with an EM [CL] strain. Results especially indicate that it is more than 3 times less probable for a CL strain to over-infect an EM infected plant than for an EM strain to over-infect a CL infected plant. To investigate if these asymmetric interactions can explain the CL/EM shift observed at regional scale, an exploratory model describing WMV epidemiology over several years in a landscape composed of a reservoir and a cultivated compartment is introduced. In most simulations a shift is observed and both strains do coexist in the landscape, reaching an equilibrium that depends on the probabilities of over-infection.     

DOES ELASTIN CONTRIBUTE TO THE PERSISTENCE OF CORPORA ALBICANTIA IN THE OVARY OF THE COMMON DOLPHIN (DELPHINUS DELPHIS)

The corpora albicantia (CAs) from the ovaries of 39 common dolphins ( Delphinus delphis ) caught in driving fisheries were used, and histologically and immunohistochemically examined. The area of each corpus albicans (CA) and the proportion of that area occupied by elastin were measured using NIH-image software. In all CAs, elastoid material (EM) was apparent although EM area varied in each CA. CAs increased in number with dolphin age. Smaller CAs contained a higher proportion of EM. EM was completely digested by elastase, but not by collagenase. Furthermore, EM was immunostained with anti-α-elastin antibody. These results demonstrated that EM was elastin. The present study is the first to describe the presence of elastin in cetacean CAs. The higher proportion of elastin in small-sized CAs of common dolphins is suggested as the likely cause of the persistence of CA.     

Disruption of Escherichia coli outer membranes by EM 49. A new membrane active peptide.

A new peptide antibiotic, EM 49, is shown to disrupt the structure of Escherichia coli outer membranes and release outer membrane fragments into the surrounding media. Evidence supporting this conclusion indludes EM 49 stimulated release of outer membrane phospholipids, lipopolysaccharide, and membrane fragments having a phospholipid and polypeptide composition similar to outer membranes. The density of the membrane fragments released by EM 49 was 1.22 g/cm3, which was identical to isolated outer membranes. Approximately 10 to 15% of the E. coli lipopolysaccharide was released upon treatment with EM 49. Both scanning and transmission electron microscopy revealed that the antibiotic caused the formation of numerous protrusions or blebs on the surface of E. coli with apparent release of membrane vesicles from the cells. Direct interaction between EM 49 and outer membranes was demonstrated using outer membranes labeled with the fluorescent dye diphenylhexatriene. Treatment of the fluorescent-labeled outer membranes with EM 49 increased fluorescence intensity and decreased polarization, indicating that the peptide perturbed outer-membrane structure. In addition, strong interactions between EM 49 and purified E. coli phospholipids were detected using the Hummel and Dreyer technique. Association constants between the peptide and phospholipids were approximately 10(5) M-1. A model for the disruptive effect of EM 49 on outer-membrane structure is proposed in which the fatty acid chain of the antibiotic is inserted into the hydrophobic core of the membrane. This orientation would allow the polycationic, peptide portion of the antibiotic to disrupt the antibiotic to disrupt the normal electrostatic interactions between divalent cations and components of the outer membrane. Evidence supporting this conclusion includes specific protection of E. coli from EM 49 by Mg2+ and Ca2+ and inhibition of EM 49 stimulated phospholipid release by these cations. Disruption of the antibiotic to penetrate to the inner membrane, which is probably the primary killing site of EM 49.     

Biochemical characterization and immunocytochemical localization of EM66, a novel peptide derived from secretogranin II, in the rat pituitary and adrenal glands.

Characterization of secretogranin II (SgII) mRNA in various vertebrates has revealed selective conservation of the amino acid sequences of two regions of the protein, i.e., the bioactive peptide secretoneurin and a flanking novel peptide that we named EM66. To help elucidate the possible role of EM66, we examined the occurrence as well as the cellular and subcellular distribution of EM66 in rat pituitary and adrenal glands by using a polyclonal antibody raised against the recombinant human EM66 peptide. High-performance liquid chromatography (HPLC) analysis of rat pituitary and adrenal extracts combined with a radioimmunoassay resolved EM66-immunoreactive material exhibiting the same retention time as recombinant EM66. In the rat pituitary, double-labeling immunohistochemical (IHC) studies showed that EM66 immunoreactivity (IR) was present in gonadotrophs, lactotrophs, thyrotrophs, and melanotrophs, whereas corticotrophs were devoid of labeling. EM66-IR was also observed in nerve endings in the neural lobe. Immunocytochemical staining at the electron microscopic level revealed that EM66-IR is sequestered in the secretory granules within gonadotrophs and lactotrophs. In the adrenal medulla, double IHC labeling showed that EM66-IR occurs exclusively in epinephrine-synthesizing cells. At the ultrastructural level, EM66-IR was seen in chromaffin vesicles of adrenomedullary cells. These results demonstrate that post-translational processing of SgII generates a novel peptide that exhibits a cell-specific distribution in the rat pituitary and adrenal glands where it is stored in secretory granules, supporting the notion that EM66 may play a role in the endocrine system.