Plant virus-induced changes in aphid population development and temporal fluctuations in plant nutrients

Cucurbita pepo plants were infected with zucchini yellow mosaic virus or maintained noninfected.Aphis gossypii, which transmits the virus, lived longer and produced more offspring on infected than on noninfected plants. On infected plants, the intrinsic rate of natural increase forA. gossypii increased with time after inoculation. In a similar experiment, concentrations of phloem sap nutrients, including free amino acids, total protein, and sugars from infected and noninfected plants were compared for 37 days after inoculation. Significant differences in levels of individual amino acids from phloem exudate between infected and noninfected plants were found, yet the concentration of total amino acids was not substantially different between infected and noninfected plants. Beginning four days after inoculation, the total protein content of phloem exudate generally was lower in infected plants than noninfected plants. Likewise, the total sugar content of phloem exudate from infected plants was lower than that of noninfected plants beginning nine days after inoculation. In contrast with the results from analyses of phloem exudate, foliage from infected plants had higher levels of almost all amino acids than noninfected foliage beginning nine days after inoculation. Concentrations of individual and total amino acids in infected foliage increased throughout the experimental period. Although no temporal effects were observed in the foliage sugar content for either individual or total sugars, starch content decreased with time in infected plants, while in noninfected plants, starch content remained level.     

Co-occurrence of aflatoxin B1, fumonisin B1, ochratoxin A and zearalenone in cereals and peanuts from C?te d'Ivoire.

This survey examined 30 samples of rice (n = 10), maize (n = 10) and peanuts (n = 10) from C?te d'Ivoire for aflatoxin B1, fumonisin B1 and zearalenone using immunoassays, and ochratoxin A using a validated HPLC method with fluorescence detection. In C?te d'Ivoire, as in other countries, several mycotoxins are present in the same commodities. These mycotoxins are from different structural families: aflatoxin B1, fumonisin B1, zearalenone and ochratoxin A, normally produced by fungal species from Aspergillus, Penicillium and Fusarium genera. Some samples contained four mycotoxins (86%). Four peanuts samples did not show ochratoxin A (14%), whereas they contained aflatoxin B1 concentrations above the EU regulatory limits. Concentrations of ochratoxin A, zearalenone and fumonisin B1 were low and may not cause problems per se; however, fears remain that the tolerable daily intake may be exceeded due to eating habits and synergistic effects could be important with the combination of several mycotoxins. Investigations in this direction are underway, together with isolation and characterization of the fungal species involved.     

Optimization of the dynamic wavefront control of a pulsed kilojoule/nanosecond-petawatt laser facility

The wavefront aberrations in a large-scale, flash-lamp-pumped, high-energy, high-power glass laser system can degrade considerably the quality of the final focal spot, and limit severely the repetition rate. The various aberrations induced on the Laboratoire pour l'Utilisation des Lasers Intenses (LULI), laser facility (LULI2000) throughout the amplification are identified and analyzed in detail. Based on these analyses, an optimized procedure for dynamic wavefront control is then designed and implemented. The lower-order Zernike aberrations can be effectively reduced by combining an adaptive-optics setup, comprising a bimorph deformable mirror and a four-wave lateral shearing interferometer, with a precise alignment system. This enables the laser chain to produce a reproducible focal spot close to the diffraction limit (Strehl ratio approximately 0.7). This allows also to increase the repetition rate, initially limited by the recovery time of the laser amplifiers, by a factor of 2 (one shot per hour). The proposed procedure provides an attractive alternative for dynamic correction of the wavefront aberrations of a laser facility as complex as the LULI2000.     

Identification of a Widespread Monomolecular Odor Differentially Attractive to Several <Emphasis Type="Italic">Delia Radicum</Emphasis> Ground-dwelling Predators in the Field

Dimethyl disulfide (DMDS) was identified as a major volatile constituent of Brassica napus roots heavily infested by Delia radicum, the cabbage root fly. Attractiveness of this widespread compound was tested in the field in a naturally complex odorous environment. By using an original setup especially designed for ground dwelling beetles, different concentrations of the pure molecule as well as attractiveness of the natural blend emitted by the rotten part of infested roots were tested simultaneously. The use of general linear model (GLM) statistics permitted us to finely discriminate the responses among the different treatments. The main predators of D. radicum (i.e., two staphylinids Aleochara bilineata and Aleochara bipustulata and carabid beetles of the genus Bembidion) were significantly attracted by DMDS, but responded in different ways to the natural blend and to the different concentrations tested. The dose–response curves were similar for the two staphylinids. However, whereas A. bilineata was more attracted by the natural volatile blend than by its preferred DMDS concentration, A. bipustulata was attracted as much by the natural blend as by its preferred DMDS concentration. Carabid beetles exhibited a different response. They were not attracted by the natural blend, but responded to a wider range of DMDS concentrations that included low concentrations that did not attract the staphylinid beetles. These results are discussed according to the potential resources searched by each taxon studied and their specificity for the resources. The possible use of DMDS for enhancing biological control of D. radicum is mentioned.     

A spatial model of urban winter woodsmoke concentrations

In many urban areas, residential wood burning is a significant wintertime source of PM2.5. In this study, we used a combination of fixed and mobile monitoring along with a novel spatial buffering procedure to estimate the spatial patterns of woodsmoke. Two-week average PM2.5 and levoglucosan (a marker for wood smoke) concentrations were concurrently measured at upto seven sites in the study region. In addition, pre-selected routes spanning the major population areas in and around Vancouver, B.C. were traversed during 19 cold, clear winter evenings from November, 2004 to March, 2005 by a vehicle equipped with GPS receiver and a nephelometer. Fifteen-second-average values of light scattering coefficient (bsp) were adjusted for variations between evenings and then combined into a single, highly resolved map of nighttime winter bsp levels. A relatively simple but robust (R(2) = 0.64) land use regression model was developed using selected spatial covariates to predict these temporally adjusted bsp values. The bsp values predicted by this model were also correlated with the measured average levoglucosan concentrations at our fixed site locations (R(2) = 0.66). This model, the first application of land use regression for woodsmoke, enabled the identification and prediction of previously unrecognized high woodsmoke regions within an urban airshed.     

Isothermal and Dynamic Microcalorimetry for Quantifying the Crystallization of an Amorphous Drug during Interactive Powder Mixing

ABSTRACT

This study reports the crystallization of amorphous nifedipine during an interactive mixing process quantified by using isothermal and dynamic microcalorimetry. Interactive mixtures of amorphous nifedipine and uniform glass beads were prepared by mixing in a Turbula® mixer. The difference in the extent of crystallization of amorphous nifedipine during mixing was characterized by the time it took for the crystallization of a known amount of amorphous nifedipine in isothermal calorimetry and the change in the height of the crystallization peak at 65°C in dynamic calorimetry. It was found that both isothermal and dynamic microcalorimetry are useful techniques for quantifying the physical transition of amorphous nifedipine during interactive mixing. The rate and extent of crystallization of amorphous nifedipine depended on both mixing time and speed, but mixing time played a more dominant role because the transformation of amorphous to crystalline nifedipine was greater after 3180 revolutions (9.7%) than after 405 revolutions (0.9%) at 27 rpm. The same trend was observed at 109 rpm, but the percentage of crystalline nifedipine after 3180 revolutions was only 5.2%. This meant that an increase in mixing time rather than speed increased the rate of amorphous to crystalline transformation. The greatest cause for crystal transformation during interactive mixing was the presence of crystal seeds of the thermodynamically stable nifedipine Modification I because the amount of amorphous to crystalline transformation increased from 2.6% for a completely amorphous mixture to 6.6% for a 92:8 mixture of amorphous and crystalline nifedipine when mixed for 30 minutes at 106 rpm.     

Enzyme-triggered radical reactions: another approach for tin-free radical chemistry

The system laccase/mediator/dioxygen is able to trigger radical reactions with radical precursors which are not natural substrates of this enzyme. The radical generation has been accomplished by single electron transfer oxidation of a 1,3-dicarbonyl precursor. The process is exemplified with a radical cascade.     

Grain accumulation of selenium species in rice (Oryza sativa L.)

Efficient Se biofortification programs require a thorough understanding of the accumulation and distribution of Se species within the rice grain. Therefore, the translocation of Se species to the filling grain and their spatial unloading were investigated. Se species were supplied via cut flag leaves of intact plants and excised panicle stems subjected to a ± stem-girdling treatment during grain fill. Total Se concentrations in the flag leaves and grain were quantified by inductively coupled plasma mass spectrometry. Spatial accumulation was investigated using synchrotron X-ray fluorescence microtomography. Selenomethionine (SeMet) and selenomethylcysteine (SeMeSeCys) were transported to the grain more efficiently than selenite and selenate. SeMet and SeMeSeCys were translocated exclusively via the phloem, while inorganic Se was transported via both the phloem and xylem. For SeMet- and SeMeSeCys-fed grain, Se dispersed throughout the external grain layers and into the endosperm and, for SeMeSeCys, into the embryo. Selenite was retained at the point of grain entry. These results demonstrate that the organic Se species SeMet and SeMeSeCys are rapidly loaded into the phloem and transported to the grain far more efficiently than inorganic species. Organic Se species are distributed more readily, and extensively, throughout the grain than selenite.     

Bacterial diversity of Darfiyeh, a Lebanese artisanal raw goat's milk cheese

In order to contribute to the preservation of the Lebanese dairy heritage, the aim of this study was to characterize the Darfiyeh cheese, a traditional variety made from raw goat's milk and ripened in goat's skin. Three independent batches of Darfiyeh production were analyzed after 20, 40 and 60 days of ripening. Mesophilic lactobacilli, thermophilic coccal-shaped lactic acid bacteria (LAB) and thermophilic lactobacilli were enumerated. In order to explore the Darfiyeh natural ecosystem, a combination of phenotypical and molecular approaches was applied. The latter included Polymerase Chain Reaction-temporal temperature gel electrophoresis (PCR-TTGE), classical PCR and quantitative PCR. These methods revealed the presence of Streptococcus thermophilus, Enterococcus faecium, Enterococcus durans, Enterococcus faecalis, Enterococcus malodoratus, group D Streptococcus sp., Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris, Lactobacillus plantarum, Lactobacillus curvatus, Staphylococcus haemolyticus, Escherichia coli, Clostridium sp./Eubacterium tenue. Real-time PCR enabled quantification of E. faecium, with a detection of 10⁷–10⁹ cfu g⁻¹ of product. The present molecular approaches combined with phenotypic method allowed describing the complex natural ecosystem of Darfiyeh, giving useful information for the preservation of Lebanese artisanal dairy products.     

A new approach for the purification and characterisation of PA49.5, the main prebiotic of Lactococcus lactis subsp. cremoris

The main autolysin PA49.5, an enzyme that hydrolyzes or destroys the components of a biological endogenous cell or a tissue, was purified 3045 times from the homogenate of a whole cell extract of Lactococcus lactis subsp. cremoris ATCC 9596 (Mc5), with a recovery yield of 52%. The purification of the protein was carried out through a micro-purification technique using SDS-BigCHAP polyacrylamide gel electrophoresis and concentrated with a Microcon-10 filtration system. SDS-polyacrylamide gel electrophoresis of the purified enzyme confirmed the presence of only one band having a molecular weight of 49.5 kDa. In view of its insolubility, PA49.5 contained in the cell extract precipitate was solubilized in the presence of 0.1% (w/v) of BigCHAP, a non-ionic detergent. Higher concentrations of this detergent completely inhibited the activity of solubilized PA49.5 or prevented its solubilization. The optimal pH and temperature for PA49.5 enzymatic activity are 7.5 and 45 degrees C respectively. In addition 0.1% or less of PA49.5 significantly increased Mc5 lysis. We observed 55% more lysis with 0.25 mug of purified PA49.5 compared to the control. Gas chromatography analysis of the components of the crude cell extract, of the precipitate and of the supernatant indicates the presence of at least 6 fatty acids. The long-chained fatty acids (e.g. C18:0 and C18:3) detected represent 81.65% of the precipitate from which PA49.5 was purified. Of these two acids, the C18:0 (stearic acid) alone represents 47.40% of the precipitate. Mc5 releases proteins at the beginning (major peak) and at the end (moderate peak) of the exponential stage of growth. Analysis by denaturing polyacrylamide gel electrophoresis with Mc5 cell walls incorporated as the autolysin's substrate identified a band corresponding to PA49.5 in the second peak of protein secretion.