Interactions between the ant Tapinoma nigerrimum (Hymenoptera: Formicidae) and the main natural enemies of the vine and citrus mealybugs (Hemiptera: Pseudococcidae)

Honeydew-excreting hemipterans, such as mealybug pests, can be protected from their natural enemies by tending ants in return for honeydew, thereby compromising the aims of biological control. In this respect, antagonistic interactions between the ant Tapinoma nigerrimum, native to the Mediterranean basin, and the main natural enemies of both the vine mealybug (VMB), Planococcus ficus, and the citrus mealybug (CM), Planococcus citri, were assessed in laboratory conditions. Parasitism of vine and CMs by their respective parasitoids, Anagyrus sp. nr. pseudococci and Leptomastix dactylopii, was negatively affected by the ant T. nigerrimum. Similarly, T. nigerrimum was shown to significantly disrupt the predatory potential of ladybird larvae, Cryptolaemus montrouzieri, when foraging on host CMs. By contrast, the presence of the ant did not negatively influence the predatory activity of C. montrouzieri adults when feeding on CMs. Consequently, the encyrtid parasitoids A. sp. nr. pseudococci and L. dactylopii and the larval stage of the predator C. montrouzieri may be considered as T. nigerrimum-sensitive, whereas the adults of C. montrouzieri may be regarded as T. nigerrimum-resistant predators. Accordingly, the ant T. nigerrimum constitutes a threat to the biological control of mealybugs by either the encyrtids A. sp. nr. pseudococci and L. dactylopii or the larval stage of the ladybird C. montrouzieri. Hence, adequate control of T. nigerrimum is highly recommended before any release of these mealybugs' natural enemies.     

Simultaneous determination of rufloxacin, fenbufen and felbinac in human plasma using high-performance liquid chromatography

A simple, specific and sensitive high-performance liquid chromatographic method has been developed for the simultaneous determination of rufloxacin, fenbufen and felbinac in human plasma. Plasma, spiked with internal standard, was vortex-mixed for 1 min with a mixture of dichloromethane-diethyl ether (80:20, v/v). The evaporated extract was dissolved in 0.02 M NaOH. Drugs were resolved at room temperature on a 5 μm Zorbax SAX column (250×4.6 min I.D.) equipped with a 20×4.6 mm anion-exchange Vydac AXGU ( 10 μm particle size) precolumn. The mobile phase consisted of acetonitrile and phosphate buffer (pH 7.0), delivered at a flow-rate of 1.2 ml/min. Detection was made at 280 nm, 2-[4-(2′-Furoyl)phenyl]propionic acid was used as internal standard. The calibration curve was linear from 0.2 to 10μg/ml for rufloxacin, from 0.5 to 30 μg/ml for fenbufen and from 0.2 to 10 μg/ml for felbinac, respectively. The detection limit was 0.1 μg/ml for rufloxacin. 0.3 μg/ml for fenbufen and 0.1 μg/ml for felbinac, respectively.     

Conformational behaviour of A cyclolinopeptide a analogue: Two-dimensional NMR study of cyclo(Pro1-Pro-Phe-Phe-Ac6c-IIe-ala-Val8)

The cyclic octapeptide cyclo[-Pro¹-Pro-Phe-Phe-Ac₆c-Ile-ala-Val⁸-] [C₈-Ac₆c], containing the Pro¹-Pro-Phe-Phe sequence, followed by a bulky helicogenic C^α,α-dialkylated glycine residue Ac₆c (1-aminocyclohexane-1-carboxylic acid), and a _D-Ala residue at position 7 has been synthesized. This cyclic peptide is a deletion analogue of the naturally occurring cyclic nonapeptide cyclolinopeptide A (CLA). It has been designed with the aim of studying the role that the Ac₆c and _D-Ala residues play on the conformational behaviour of the whole molecule and their influence on the conformation of the Pro¹-Pro-Phe-Phe sequence when compared with cyclolinopeptide A. C₈Ac₆c has been investigated in chloroform and acetonitrile solutions by 2D NMR techniques. Only one set of sharp signals is observed in both solvents. This evidence strongly supports the hypothesis that only one conformational state exists in the chosen solvents. The interpretation of the experimental data points to the existence for C₈-Ac₆c of a very rigid structure stabilized by intramolecular hydrogen bonds. The measured NOE effects allow the calculation of internuclear distances, which have been used as restraints in molecular dynamic calculations. The proposed conformation of the molecule shows that the Pro-Pro-Phe segment retains the conformation observed in natural CLA both in solution and in the solid state and that the Ac₆c residue indeed reinforces the ring rigidity not permitting the formation of any appropriate cavity in which inorganic cations could be complexed.     

Quantitation of pH-induced Aggregation in Binary Protein Mixtures by Dielectric Spectroscopy

This paper presents a quantitative approach for measuring pH-controlled protein aggregation using dielectric spectroscopy. The technique is demonstrated through two aggregation experiments, the first between ??-lactoglobulin (??-Lg) and hen lysozyme (HENL) and the second between bovine serum albumin (BSA) and HENL. In both experiments, the formation of aggregates is strongly dependent on the solution pH and is clearly indicated by a decrease in the measured permittivity when the second protein is added. A quantifiable lower-bound on the ratio of proteins involved in the aggregation process is obtained from the permittivity spectra. Lower-bound aggregation ratios of 83?% for ??-Lg/HENL at pH?6.0 and 48?% for BSA/HENL at pH?9.2 were consistent with turbidity measurements made on the same solutions.     

Disposal of blood [1-13C]lactate in humans during rest and exercise

Lactate irreversible disposal (RiLa) and oxidation (RoxLa) rates were studied in six male subjects during rest (Re), easy exercise [EE, 140 min of cycling at 50% of maximum O2 consumption (VO2max)] and hard exercise (HE, 65 min at 75% VO2max). Twenty minutes into each condition, subjects received a Na+-L(+)-[1-13C]lactate intravenous bolus injection. Blood was sampled intermittently from the contralateral arm for metabolite levels, acid-base status, and enrichment of 13C in lactate. Expired air was monitored continuously for determination of respiratory parameters, and aliquots were collected for determination of 13C enrichment in CO2. Steady-rate values for O2 consumption (VO2) were 0.33 +/- 0.01, 2.11 +/- 0.03, and 3.10 +/- 0.03 l/min for Re, EE, and HE, respectively. Corresponding values of blood lactate levels were 0.84 +/- 0.01, 1.33 +/- 0.05, and 4.75 +/- 0.28 mM in the three conditions. Blood lactate disposal rates were significantly correlated to VO2 (r = 0.78), averaging 123.4 +/- 20.7, 245.5 +/- 40.3, and 316.2 +/- 53.7 mg X kg-1 X h-1 during Re, EE, and HE, respectively. Lactate oxidation rate was also linearly related to VO2 (r = 0.81), and the percentage of RiLa oxidized increased from 49.3% at rest to 87.0% during exercise. A curvilinear relationship was found between RiLa and blood lactate concentration. It was concluded that, in humans, 1) lactate disposal (turnover) rate is directly related to the metabolic rate, 2) oxidation is the major fate of lactate removal during exercise, and 3) blood lactate concentration is not an accurate indicator of lactate disposal and oxidation.     

Lethal and sub-lethal effects of insecticides on natural enemies of citrus scale pests

Laboratory trials were conducted to test the side-effects of the insecticides chlorpyrifos-methyl, buprofezin, pyriproxifen, spinosad and a narrow range mineral oil on Aphytis melinus DeBach, Coccophagus lycimnia Walker (Hymenoptera: Aphelinidae) and Leptomastix dactylopii Howard (Hymenoptera: Encyrtidae). The effects of chlorpyrifos-methyl, spinosad and pyriproxifen were also investigated in semi-field conditions on L. dactylopii. Contact toxicity on adult female parasitoids after 24, 48 and 72 h, the effects on their fertility as well as the sex ratio of the progeny were measured. In the laboratory trials chlorpyrifos-methyl and spinosad caused 100% mortality on all tested parasitoids just 24 h after the treatment. According to the IOBC classification, the mineral oil was slightly harmful on L. dactylopii; buprofezin was harmful on C. lycimnia, and slightly harmful on L. dactylopii and A. melinus; pyriproxifen resulted moderately harmful on C. lycimnia and slightly harmful on L. dactylopii and A. melinus. The progeny production of each L. dactylopii surviving female treated with buprofezin was not affected by the treatment while in the case of A. melinus it was significantly reduced. C. lycimnia females treated with pyriproxifen did not produce any progeny. In semi-field conditions the tested insecticides were less harmful to L. dactylopii adults but, although none of them influenced the progeny production of the survived females, the longevity was negatively affected.     

Characterization of tetrakis(thiadiazole)porphyrazine metal complexes by magnetic circular dichroism and magnetic circularly polarized luminescence

The magnetic circular dichroism (MCD) spectra of metal complexes of tetrakis(thiadiazole)porphyrazines ([TTDPzM] with M = 2H^I, Zn^II, Mg^II(H₂O), and Cd^II) have been recorded in dimethyl formamide solution. Together with the UV–Vis spectra, the MCD spectra provide useful information about the structure and electronic properties of the complexes. The experimental UV–Vis and MCD spectra compare pretty well with DFT calculations of two sorts, based either on the sum-over-states (SOS) approach or on the complex polarization propagator approach. They further corroborate the findings and interpretation of MCD spectra of porphyrazines based on the model of Michl for peripheral molecular orbitals. Magnetic circularly polarized luminescence (MCPL) spectra, quite uncommon in the literature, have been recorded for [TTDPzM] (M = 2H^I, Zn^II, Mg^II(H₂O)).     

Testing the vibrational exciton and the local mode models on the instructive cases of dicarvone,dipinocarvone, and dimenthol vibrational circular dichroism spectra

The vibrational circular dichroism (VCD) spectra of dicarvone ( 1 ), dipinocarvone ( 2 ), and dimenthol ( 3 ) have been recorded in the range 900–3200 cm⁻¹, encompassing the mid-infrared (mid-IR), the CO stretching, and the CH-stretching regions. For compound 3 also, the fundamental and the first overtone OH stretching regions have been investigated by IR/NIR absorption and VCD. Density functional theory (DFT) calculations allow one to interpret the IR and VCD spectra and to confirm the configuration/conformational studies previously conducted by X-ray diffraction. The most intense VCD signals are associated with the vibrational normal modes involving symmetry-related groups close to the CC bond connecting covalently the two molecular units. The vibrational exciton (VCDEC) model is fruitfully tested on the VCD data of compounds 1 and 2 for the spectroscopic regions at ~1700 cm⁻¹, and the local mode model is tested on compound 3 at ~3500 and ~6500 cm⁻¹. For compounds 1 and 2 also, ECD spectra are reported, and the exciton mechanism is tested also there, and connections to the VCDEC model are examined.