Location by fluorescence microscopy of glycosidases and a xylanase in the anaerobic gut fungi Caecomyces communis,Neocallimastix frontalis,and Piromyces rhizinflata

-d-Glucosidase, -d-fucosidase -d-xylosidase, and -cellobiopyranosidase activities in Caecomyces communis, Neocallimastix frontalis, and Piromyces rhizinflata, located with fluorescent conjugates, occur throughout the whole thallus as from zoospore germination and disappear before sporulation. -d-Galactosidase and -l-arabinopyranosidase activities are low or nonexistent. A xylanase, detected by indirect immunofluorescence, was observed at the surface of the vegetative cells, vesicles, or rhizoids. Cross-reactions prove the existence of analogies in structure among the enzymes of these anaerobic gut fungi.     

Arbuscular mycorrhizal fungi protect a subtropical tree species exposed to simulated acid rain by accelerating photosynthetic ability,antioxidant enzymes and osmolyte accumulation

丛枝菌根真菌对其宿主光合能力、抗氧化酶和渗透物质积累的促进作用 及其抗酸雨机制的探讨 酸雨在中国南方发生频繁,对亚热带树种生长具有明显抑制作用。以往研究表明,丛枝菌根真菌(AM真菌)可以缓解酸雨对宿主植物的胁迫效应。榉树(Zelkova serrata)为中国南方主要经济树种之一,其如何与共生AM真菌协同、增强其抗酸雨胁迫的能力是本项研究所要探讨的关键科学问题。通过温室控制实验,将榉树幼苗随机接受4个水平的AM真菌接种处理(接种灭菌菌种;单独接种Rhizophagus intraradices;单独接种Diversispora versiformis;接种这两种菌种的混合菌种)和3个pH水平(pH2.5、pH4.0和pH5.6)的硫酸型酸雨和硝酸型酸雨处理组成的12个处理组合,同时测定其生长、光合性能、抗氧化酶、渗透调节和土壤酶的响应格局。研究发现酸雨处理显著降低了非菌根榉树幼苗的总干重、总叶绿素含量、叶片净光合速率和可溶性蛋白的含量;接种AM真菌,特别是接种混合菌种,显著提高了强酸胁迫下榉树幼苗的总干重、光合性能、丙二醛、过氧化物酶、超氧化物歧化酶、可溶性蛋白和根系酸性磷酸酶活性。此外,菌根效应依赖于AM真菌的种类和酸胁迫的梯度。本研究 结果表明,AM真菌对榉树幼苗抗酸胁迫的调控作用主要源于调节宿主植株光合能力、抗氧化酶和渗透物质的积累。榉树与其共生AM真菌在应对酸胁迫上协同机制的解析为该树种在中国南方酸雨区的栽培提供理论基础、具有重要的实践指导意义。     

Hmgcr in the corpus allatum controls sexual dimorphism of locomotor activity and body size via the insulin pathway in Drosophila

The insulin signaling pathway has been implicated in several physiological and developmental processes. In mammals, it controls expression of 3-Hydroxy-3-Methylglutaryl CoA Reductase (HMGCR), a key enzyme in cholesterol biosynthesis. In insects, which can not synthesize cholesterol de novo, the HMGCR is implicated in the biosynthesis of juvenile hormone (JH). However, the link between the insulin pathway and JH has not been established. In Drosophila, mutations in the insulin receptor (InR) decrease the rate of JH synthesis. It is also known that both the insulin pathway and JH play a role in the control of sexual dimorphism in locomotor activity. In studies here, to demonstrate that the insulin pathway and HMGCR are functionally linked in Drosophila, we first show that hmgcr mutation also disrupts the sexual dimorphism. Similarly to the InR, HMGCR is expressed in the corpus allatum (ca), which is the gland where JH biosynthesis occurs. Two p[hmgcr-GAL4] lines were therefore generated where RNAi was targeted specifically against the HMGCR or the InR in the ca. We found that RNAi-HMGCR blocked HMGCR expression, while the RNAi-InR blocked both InR and HMGCR expression. Each RNAi caused disruption of sexual dimorphism and produced dwarf flies at specific rearing temperatures. These results provide evidence: (i) that HMGCR expression is controlled by the InR and (ii) that InR and HMGCR specifically in the ca, are involved in the control of body size and sexual dimorphism of locomotor activity.     

Oxypropylation of cork and the use of the ensuing polyols in polyurethane formulations

Cork particles, recovered as byproducts of the processing of this natural material, were oxypropylated under pressure and relatively high temperature in the presence of KOH as catalyst. Various parameters were explored in order to assess the most suitable conditions, which led to the almost complete conversion of the solid cork into a viscous polyol. This product was a mixture of oxypropylated cork macromolecules and propylene oxide oligomers, which were thoroughly characterized. The use of these polyols as macromonomers in the synthesis of polyurethane foams gave promising results, thus showing that it should be possible to exploit the residues of this important renewable resource to manufacture original materials.     

Bioactive sucrose esters from Bidens parviflora

An investigation on Bidens parviflora led to the isolation of three sucrose esters and a substituted truxillate. Their structures were elucidated as (6-O-(E)-p-coumaroyl)-beta-D-fructofuranosyl-(2-->1)-alpha-D-glucopyranoside, (6-O-(E)-p-coumaroyl)-beta-D-fructofuranosyl-(2-->1)-(6-O-(E)-p-coumaroyl)-alpha-D-glucopyranoside II, 6,6'-sucrose ester of (1alpha,2alpha,3beta,4beta)-3,4-bis(4-hydroxyphenyl)-1,2-cyclobutanedicarboxylic acid, dimethyl ester of (1alpha,2alpha,3alpha,4alpha)-2,4-bis(3,4-dihydroxyphenyl)-1,3-cyclobutanedicarboxylic acid on the basis of spectral and chemical evidence. These compounds were subjected to the following bioassays: the histamine release inhibition of rat mast cells induced by antigen-antibody reaction and the inhibitory activity of PGE(2) production by macrophages.     

Chemodiversity of Volatile Oils in Thapsia garganica L. (Apiaceae)

The chemical composition of the volatile oils obtained from the roots, leaves, flowers, and stems of Thapsia garganica of Tunisian origin was investigated by GC‐FID and GC/MS analyses. Sesquiterpene hydrocarbons and oxygenated monoterpenes were predominant in the oils of all plant parts. Bicyclogermacrene (21.59–35.09%) was the main component in the former compound class, whereas geranial (3.31–14.84%) and linalool (0.81–10.9%) were the most prominent ones in the latter compound class. Principal‐component (PCA) and hierarchical‐cluster (HCA) analyses revealed some common constituents, but also significant variability amongst the oils of the different plant parts. This organ‐specific oil composition was discussed in relation to their biological and ecological functions. For the evaluation of the intraspecific chemical variability in T. garganica, the composition of the flower volatile oils from four wild populations was investigated. Bicyclogermacrene, linalool, and geranial were predominant in the oils of three populations, whereas epicubenol, β‐sesquiphellandrene, and cadina‐1,4‐diene were the most prominent components of the oil of one population. PCA and HCA allowed the separation of the flower oils into three distinct groups, however, no relationship was found between the volatile‐oil composition and the geographical distribution and pedoclimatic conditions of the studied populations.     

Influence of temperature and salinity on the germination of Lotus creticus (L.) from the arid land of Tunisia

Effects of salinity, temperature and their interactions on the rate and final percentage of germination were evaluated for two populations (Msarref, Oued dkouk) of the invasive glycophyte Lotus creticus Linné, grown under arid environmental conditions of the Tunisia. Seeds that were not treated with NaCl germinated well in a wide range of temperatures. For both populations, maximum germination occurred in distilled water at 25°C and lowest germination for all salinities was at 35°C. Germination was substantially delayed and significantly reduced with an increase in NaCl to levels above 300 mm . Compared to the Oued dkouk population, final germination and germination rate of the Msarref population was completely inhibited at 300 mm NaCl. The interactive effect of temperature and NaCl concentration on final germination and germination rate was significant (P < 0.01), indicating that the germination response to salinity depended on temperature. The inhibition of Oued dkouk population seed germination at high salt concentration was mostly due to osmotic effects while ionic effects were noted at Msarref population. The germination behaviour of the Oued dkouk population would therefore imply adaptive mechanisms to saline environments, while in the Msarref population such mechanisms seem to be absent. Since seed germination is more sensitive to salinity stress than the growth of established plants, the greater tolerance to salinity of Oued dkouk population would be an adaptive feature of this population to saline environment.     

Determination of the heterogeneous anisotropic elastic properties of human femoral bone: From nanoscopic to organ scale

Cortical bone is a multiscale composite material. Its elastic properties are anisotropic and heterogeneous across its cross-section, due to endosteal bone resorption which might affect bone strength. The aim of this paper was to describe a homogenization method leading to the estimation of the variation of the elastic coefficients across the bone cross-section and along the bone longitudinal axis. The method uses the spatial variations of bone porosity and of the degree of mineralization of the bone matrix (DMB) obtained from the analysis of 3-D synchrotron micro-computed tomography images. For all three scales considered (the foam (100 nm), the ultrastructure (5 μm) and the mesoscale (500 μm)), the elastic coefficients were determined using the Eshelby’s inclusion problem. DMB values were used at the scale of the foam. Collagen was introduced at the scale of the ultrastructure and bone porosity was introduced at the mesoscale. The pores were considered as parallel cylinders oriented along the bone axis. Each elastic coefficient was computed for different regions of interest, allowing an estimation of its variations across the bone cross-section and along the bone longitudinal axis. The method was applied to a human femoral neck bone specimen, which is a site of osteoporotic fracture. The computed elastic coefficients for cortical bone were in good agreement with experimental results, but some discrepancies were obtained in the endosteal part (trabecular bone). These results highlight the importance of accounting for the heterogeneity of cortical bone properties across bone cross-section and along bone longitudinal axis.     

Interactive effects of pH and temperature on the bacteriocin stability by response surface analysis

The combined influence of pH and temperature on bacteriocins produced by three lactic acid bacteria, Pediococcus pentosaceus MMZ26, Enterococcus faecium MMZ17 and Lactococcus lactis MMZ25, isolated from Tunisian traditional dry fermented meat was studied using a second order orthogonal factorial design and response-surface methodology (RSM). This method allows estimating the interactive effects of pH and temperature on the stability of each bacteriocin. The high heat stability of the three bacteriocins was demonstrated, with optimum values at light acidic pH around 5.0, temperature below 90 degrees C and short incubation times. This study contributes to a better understanding of relation between bacteriocins production and stability in order to enhance their, in situ, application as a food and feed biopreservative in fermented and/or heated food products.