The impact of eriophyoids on crops: recent issues on Aculus schlechtendali, Calepitrimerus vitis and Aculops lycopersici.

The nature of the damage caused by eriophyoid mites and the assessment of yield losses still require detailed studies if appropriate control and risk mitigation strategies are to be planned. The economic importance of eriophyoid mites is increasing worldwide and a lot of species have reached a permanent pest status in certain crops, while others represent a quarantine threat for several countries. Due to their relevant role in Europe and elsewhere, three eriophyoid mites that have been frequently reported in recent research, are here considered as case studies: two of them (the apple rust mite, Aculus schlechtendali, and the grape rust mite, Calepitrimerus vitis) colonise temperate fruits, while one (the tomato russet mite, Aculops lycopersici) affects vegetables. The damage assessment related to the apple rust mite has been evaluated on different apple varieties with implications for pest control. Some factors affecting the spread and economic importance of the grape rust mite have been identified. The complexity and difficulty in controlling the tomato russet mite by chemicals enhances the interest in biological control agents. Considerations on interactions between eriophyoids and host plants (e.g. resistance, varietal susceptibility), on pest management regimes (e.g. impact of fungicides, resistance to acaricides, perspectives on biological control) are presented.

Prostaglandin and thromboxane synthesis by M5076 ovarian reticulosarcoma during growth: effects of a thromboxane synthetase inhibitor.

The five stable metabolites [prostaglandin F2 alpha (PGF2 alpha), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha)] of arachidonic acid (AA) via the cyclooxygenase pathway were measured by high-resolution gas chromatography-mass spectrometry in M5076 ovarian reticulosarcoma (M5) homogenates at various times after tumor implantation (Days 15, 18, 21, and 24). Vegetating tumor showed an active AA overall metabolism, which significantly increased during tumor growth. Synthesis of selected products (TXB2, PGD2, and PGE2) increased markedly over time (up to 10.6, 3.5, and 0.9 micrograms/g, respectively). The overall metabolic profile was TXB2 much greater than PGD2 greater than PGF2 alpha greater than 6-keto-PGF1 alpha greater than PGE2 on Day 15 and TXB2 much greater than PGD2 much greater than PGF2 alpha greater than 6-keto-PGF1 alpha on Day 24. TXB2 was also by far the most abundant product of in vitro-cultured M5 cells. Chronic treatment of M5-bearing mice with dazmegrel (UK-38,485), a selective thromboxane synthetase inhibitor (100 mg/kg p.o. daily, from Day 7 to killing), resulted in incomplete TXB2 synthesis inhibition, AA metabolism diversion toward the other prostaglandins, and no effects of tumor growth and metastasis. More frequent dazmegrel treatment (100 mg/kg p.o. every 8 h from Day 1 to killing) resulted in complete TXB2 synthetase inhibition, AA metabolism diversion, and increased tumor growth and metastasis. These data do not support the hypothesis of thromboxane synthetase inhibitors reducing tumor growth. However, since TXB2 suppression was accompanied by the production of other products possibly interfering in tumor growth, no conclusions on the effective role of TXA2 in malignancy can be drawn.

Prostaglandin and thromboxane synthesis by Lewis lung carcinoma during growth.

The five stable metabolites [prostaglandin F2 alpha, prostaglandin D2, prostaglandin E2 (PGE2), thromboxane B2, and 6-keto-prostaglandin F1 alpha] of arachidonic acid (AA) via the cyclooxygenase pathway were measured by high-resolution gas chromatography-mass spectrometry in Lewis lung carcinoma homogenates at various times after tumor implantation (11 to 25 days). Vegetating and necrotic sections of the primary tumor and lung metastases were examined. Vegetating tumor showed a very active AA metabolism. Synthesis of PGE2, the most abundant product, markedly increased during tumor growth (up to 30 micrograms/g). A high and increasing synthetic capacity was also noted for prostaglandin D2 (up to 9 micrograms/g). Minor time differences and lower levels (up to 1.4 micrograms/g) were found for the other AA metabolites. PGE2 and prostaglandin D2 were the major products in necrotic tumor, too, but synthesis was markedly less than in vegetating tumor, and no increase was noted over time. Metastatic tissue showed a different AA metabolic profile, as compared to primary tumor and surrounding lung tissue, with PGE2 and 6-keto-prostaglandin F1 alpha being the main metabolites.

Characterization of arachidonic acid metabolic profiles in animal tissues by high-resolution gas chromatography-mass spectrometry.

A standardized, highly specific routine method was developed for the quantitative profiling of cyclooxygenase metabolites of arachidonic acid in animal tissues. Whole homogenates were used to assess the potential capacity of tissues to metabolize endogenous arachidonic acid. Samples were analyzed by high-resolution gas chromatography-mass spectrometry in the selected ion monitoring mode. The screening of several rat tissues by this method revealed marked tissue-specificity in both the synthesis capacity and prostaglandin profile. The major products detected were: 6-ketoprostaglandin F1alpha for lung, stomach, muscle and heart; prostaglandin D2 for spleen, brain and liver; prostaglandin F2alpha for kidney and prostaglandin E2 for seminal vesicles. Marked species differences were found when guinea pig tissues were analyzed.

Prostaglandins and human platelet aggregation. Implications for the anti-aggregating activity of thromboxane-synthase inhibitors.

Selective pharmacological blockade of thromboxane-synthase in human platelets by dazoxiben resulted in the reorientation of cyclic-endoperoxides towards PGE2, PGD2 and PGF2 alpha. At concentrations which can be reached when thromboxane-synthase is inhibited, PGE2 (100-500 nM) exerted a marked, concentration-dependent pro-aggregatory effect. This required the formation of endogenous or the addition of exogenous endoperoxides and was prevented by PGD2 or 13-aza-prostanoic acid, a selective antagonist of PGH2/TxA2 receptors. The anti-aggregating effect of PGD2 was evident at concentrations lower than those obtained in dazoxiben-treated platelets. It is proposed that in the absence of TxA2 generation, a combination of endoperoxides and PGE2 may result in normal aggregation. The latter may be inhibited by PGD2. No interference of PGF2 alpha on platelet function could be shown.

Inhibition of thromboxane biosynthesis by 3-pyridinol carboxypentyl ethers substituted with a hydroxylated octyl chain.

Racemic 6-[4-(3'-hydroxy-1'-octenyl)-3-pyridyloxy]hexanoic and 6-[4-(3'-hydroxyoctyl)-3-pyridyloxy] exanoic acids have been synthesized and their activity as inhibitors of the biosynthesis of thromboxane A2 in human serum has been studied, in comparison with isomers having the eight-carbon chain in the 2 position. Very high, selective activity was found for the new 4-substituted 3-pyridinol ethers, whereas the 2-substituted compounds showed no action.

Short-term changes in consumption and oviposition rates of Neoseiulus californicus strains (Acari: Phytoseiidae) after a diet shift.

Short-term effects on consumption and oviposition rates of four strains of Neoseiulus californicus (McGregor) after a diet shift were evaluated. The new feeding conditions experienced by the predators were six fixed densities of eggs or protonymphs of Tetranychus urticae Koch placed on excised strawberry leaflet discs and maintained under laboratory conditions (25 +/- 1 degrees C, 75-85% RH, 16L: 8D). The observations were made on the first and the fifth day of the experiment. The phytoseiids came from three long-term mass-reared strains fed on T. urticae, Dermatophagoidesfarinae Hughes, or Quercus spp. pollen, respectively. The fourth strain was collected directly in a strawberry field. Time since diet transfer can be added to the factors (i.e. feeding history and prey density) already known to affect the functional and numerical responses of N. californicus, both when it feeds on prey eggs and protonymphs. If consumption rates were averaged over all strains and densities, 9.04 and 11.41 eggs, and 6.97 and 6.48 protonymphs were consumed on the first and the fifth day, respectively. If the same was done for oviposition rates, predators feeding on eggs produced 1.46 and 2.36 eggs/female/day, whereas predators feeding on protonymphs produced 1.35 and 2.29 eggs/female/day. Time had the greatest impact on the functional response of the strain that had previously fed on tetranychids, while an effect of time on the numerical response was detectable in all strains.

Susceptibility of cypress seedlings to the eriophyoid mite Trisetacus juniperinus.

In Italian nurseries and young groves of evergreen cypress (Cupressus sempervirens L.), the eriophyoid mite Trisetacus juniperinus (Nal.) is considered a very serious pest. A rating system of damage symptoms was developed to investigate the susceptibility of different cypress seedling families to the mite. Based on this system, the seedlings were evaluated for three years in the nursery and in two field locations after transplanting. Data obtained in the nursery allowed the cypress families to be allocated to at least two different levels of susceptibility. These levels of susceptibility were generally also maintained in the field. However, the environmental conditions of the two transplanting localities significantly affected the susceptibility of each family. In all families, scores for each of the damage categories were strongly correlated positively to each other and negatively with the average increment in the height of plant over the duration of the field experiment. Assessment of the intensity of the symptoms peculiar to damage category A (buds enlarged, deformed, russet and/or branch apex folded) was sufficient to give the same susceptibility evaluation as if data for all damage categories were used. The evaluation of susceptibility on the basis of injury pattern may return very useful information for selection and certification of families of known susceptibility to eriophyoid mites.

Quantitative profiling of prostaglandins and thromboxane by high-resolution gas chromatography-selected--ion monitoring.

The development and biological application of a rapid method for quantitative profiling of prostaglandins and thromboxane using high-resolution gas chromatography (HRGC) coupled with mass spectrometry in the selected-ion monitoring technique (SIM) are described. The method is based on the single-step extraction of prostaglandins from biological samples on C18 reversed-phase cartridges after addition of deuterated analogues as internal standards, followed by derivatization of functional groups and final analysis by HRGC-SIM with wall-coated open tubular persilanized capillary columns. Biological applications include the determination of endogenous arachidonic acid cascade profiles in rat tissue homogenates and thromboxane synthetase inhibition studies in human serum.

Comparison of radioimmunoassay and high-resolution gas chromatography mass spectrometry for the quantitative determination of serum thromboxane B2 and 6-keto-PGF1 alpha after pharmacological blockade of thromboxane synthetase.

Radioimmunoassay (RIA) and high-resolution gas chromatography-mass spectrometry (HRGC-MS) were compared for the determination of serum 6-keto-PGF-1 alpha and TXB2 in a situation of drug-altered arachidonate metabolism. Results were comparable for TXB2 in both conditions. 6-keto-PGF1 alpha RIA determinations (with two different antisera) revealed increased levels in dazoxiben-treated samples, which were not confirmed by HRGC-MS. The assay were repeatedly checked in controlled conditions to investigate these discrepancies. Interference was found with both antisera, due to the drug-induced change in metabolism.

Coronary and systemic 6-ketoprostaglandin F1 alpha and thromboxane B2 during myocardial ischemia in dog.

The left anterior descending coronary artery (LAD) of five dogs was ligated, and blood was withdrawn from the great cardiac vein, left marginal cardiac vein, femoral vein, and aorta. After ligation, immunoreactive 6-ketoprostaglandin (PG) F1 alpha rose from less than 0.1 to a mean value of 1.2 pmol/ml plasma in the great cardiac vein (GCV) and 0.88 pmol/ml in the left marginal vein, with no change in peripheral circulation. Immunoreactive thromboxane (TX) B2 remained below 0.075 pmol/ml throughout the experiments. LAD of 11 dogs was stenosed 60-80% with consequent cyclical reductions in blood flow. 6-Keto-PGF1 alpha in GCV rose in seven dogs (range 0.5-2.2 pmol/ml) and remained unchanged in four. No change was observed in peripheral plasma levels of 6-keto-PGF1 alpha. In these experimental conditions TXB2 remained below 0.075 pmol/ml. Lactate concentrations rose in both experimental conditions in GCV but not in peripheral circulation or in the left marginal vein. This study confirms a link between cardiac ischemia and increased coronary prostacyclin release, but we were unable to detect a similar correlation with TXB2 in plasma.