Ecotoxicity of lead to the zebra musselDreissena Polymorpha,Pallas

The effect of lead on the filtration rate of the zebra musselDreissena polymorpha was investigated, together with the accumulation of Pb in the soft tissues of the mussels. The NOEC-filtration was 116 g.l^–1 (0,56 mol.l^–1) and the EC₅₀-filtration was 370 g.l^–1 (1.79 mol.l^–1). The NOEC-accumulation was the concentration found in the control water (1.4g.l^–1). These experiments show that the EC₅₀-filtration for Pb is similar to that for Cd, higher than that for Cu and lower than that for Zn. The water quality criteria for lead allow 25 g Pb.l^–1 in surface water. This will not cause short-term effects. Long-term effects may, however, occur, since an accumulation of Pb as low as 16 g.l^–1 was recorded in this study.     

The Role of Specific Tomato Volatiles in Tomato-Whitefly Interaction

Bemisia tabaci (whitefly) infestations and the subsequent transfer of viruses are the cause of severe losses in crop production and horticultural practice. To improve biological control of B. tabaci, we investigated repellent properties of plant-produced semiochemicals. The mix of headspace volatiles, collected from naturally repellent wild tomato accessions, influenced B. tabaci initial choice behavior, indicating a role for plant semiochemicals in locating host plants. A collection of wild tomato accessions and introgression lines (Solanum pennellii LA716 × Solanum lycopersicum ‘Moneyberg’) were extensively screened for attractiveness to B. tabaci, and their headspace profiles were determined by means of gas chromatography-mass spectrometry. Correlation analysis revealed that several terpenoids were putatively involved in tomato-whitefly interactions. Several of these candidate compounds conferred repellence to otherwise attractive tomato plants when applied to the plant''s branches on paper cards. The sesquiterpenes zingiberene and curcumene and the monoterpenes p-cymene, α-terpinene, and α-phellandrene had the strongest effects in free-choice bioassays. These terpenes also elicited a response of receptors on the insect''s antennae as determined by electroantennography. Conversely, the monoterpene β-myrcene showed no activity in both assays. B. tabaci apparently uses, besides visual cues, specific plant volatile cues for the initial selection of a host. Altering whitefly choice behavior by manipulation of the terpenoid composition of the host headspace may therefore be feasible.During the last decades, a worldwide spread of the pest insects Bemisia tabaci (Gennadius) and greenhouse whitefly (Trialeurodes vaporariorum) has led to local devastation of vegetable and ornamental crops, resulting in large economic losses. The damage whiteflies cause by their feeding behavior, such as affected biochemistry and development (for review, see Inbar and Gerling, 2008), is far exceeded by the secondary, indirect crop losses due to virus transmission. Specifically B. tabaci outbreaks are associated with the emergence of viruses for which they serve as vectors (Polston and Anderson, 1997). B. tabaci is capable of transmitting >100 different virus species of which the majority belong to the genus Begomovirus, such as Tomato yellow leaf curl virus, Tomato mottle virus (Jones, 2003), and African cassava mosaic virus (Maruthi et al., 2001). Damage caused by virus infection ranges from mild symptoms, such as leaf discolorations, to overall yield reduction, severe fruit necrosis, flower and fruit abortions, and plant death. Viral diseases are particularly severe since no chemical control is available and good sources of virus resistance for interspecific crossing are not always available (Maruthi et al., 2003). To date, only a limited number of virus resistance genes have been identified, and due to high mutation rates, viruses rapidly evolve (Drake and Holland, 1999; García-Andrés et al., 2006) and break monogenic resistances. Herbivores, such as whiteflies and thrips, can apparently benefit from transmitting viruses (Medeiros et al., 2004; Jiu et al., 2007; Belliure et al., 2008).B. tabaci was originally restricted to subtropical regions and greenhouses. However, the new and extremely invasive B and Q biotypes have the ability to rapidly adapt to more temperate zones and new host species (Jones, 2003; Wan et al., 2008). To date, the main control strategy for many crops is the application of insecticides, though effective spraying is complicated because of the insect''s preference for the abaxial side of the leaf (Simmons, 1994). Moreover, B. tabaci is difficult to control chemically due to emerging resistance to active ingredients (Horowitz et al., 2005). A new biological control agent, the phytoseiid predator Typhlodromips swirskii, has only been successful on plants without trichomes in closed greenhouses (Nomikou et al., 2002). The root-knot nematode resistance gene Mi1.2, which confers partial resistance to B. tabaci (Nombela et al., 2003), is widely used in modern tomato (Solanum spp.) varieties but is not sufficient to provide adequate protection against whitefly infestations.During insect host selection, orientation, and landing, both visual and olfactory cues play a predominant role (Visser, 1988). Color is an important factor in host-plant selection, and it was shown that B. tabaci reacts to blue-UV and yellow wavelengths (Van Lenteren and Noldus, 1990). The olfactory stimuli associated with the host plant initiate host targeting, whereas visual cues improve the accuracy of landing. In the initial phase of host targeting, olfaction may cause a positive chemotactic response, i.e. a flight up an odor gradient. Plant odor specificity might be achieved by a particular ratio of constituent volatiles (Bruce et al., 2005a). In the case of whiteflies, the role of olfaction in attraction or repellence has not received much prior attention. After host contact, B. tabaci evaluates host plant quality by labial dabbing and probing using piercing mouthparts. By probing, persistent viruses are transmitted via the insects'' salivary glands and mouthparts (Ghanim et al., 1998; Rosell et al., 1999). Therefore, to avoid virus transmission by B. tabaci, probing should be prevented.Volatile organic compounds released by plants can act as semiochemicals. They play an important role in enabling insects to recognize host plants from a distance (Schütz et al., 1997; Bruce et al., 2005a) or in attracting predators and parasitoids upon herbivory (De Moraes et al., 1998; Van Poecke and Dicke, 2002; Kappers et al., 2005). Moreover, they can play a role in the direct defense against herbivores and pathogens (Kessler and Baldwin, 2001; Shiojiri et al., 2006). A large number of different plant volatiles, with numerous ecological roles, have been identified so far (Sacchettini and Poulter, 1997; Pichersky et al., 2006). The largest class of plant volatiles is derived from the isoprenoid or terpenoid pathway. Solanaceous plants, like tomato, often make use of these terpenes for the defense against herbivores (Snyder et al., 1993; Kennedy, 2003). Some terpenes have been shown to exhibit repellent properties to insects (Peterson et al., 2002; Birkett et al., 2004; Terry et al., 2007). These plant-produced semiochemicals can potentially be used as insect repellents of natural origin, thus providing an alternative to the use of pesticides (Peterson and Coats, 2001). Engineering terpene emission to make crop plants more attractive to herbivore enemies has already been shown to be feasible (Degenhardt et al., 2003; Kappers et al., 2005; Schnee et al., 2006).The aim of this study is to identify the role of plant volatiles in the B. tabaci-tomato host interaction and to identify the terpenes that cause repellence of a selection of wild tomato accessions. The potential of several terpenes as repellent olfactory cues in B. tabaci host-preference behavior has been assessed in behavioral studies and through electroantennography (EAG).     

Tomato-produced 7-epizingiberene and R-curcumene act as repellents to whiteflies

How whiteflies (Bemisia tabaci) make the choice for a host plant prior to landing, is not precisely known. Here we investigated whether they respond to specific volatiles of tomato. Zingiberene and curcumene were purified from Solanum habrochaites (PI127826), characterised by NMR and X-ray analysis and identified as 7-epizingiberene and R-curcumene. In contrast, oil from Zingiber officinalis contained the stereoisomers zingiberene and S-curcumene, respectively. Using a combination of free-choice bio-assays and electroantennography, 7-epizingiberene and its dehydrogenated derivative R-curcumene were shown to be active as semiochemicals to B. tabaci adults, whereas the stereoisomers from ginger were not. In addition, R-curcumene elicited the strongest electroantennographic response. Bio-assays showed that a cultivated tomato could be made less attractive to B. tabaci than its neighbouring siblings by the addition of the tomato stereoisomer 7-epizingiberene or its derivative R-curcumene. These sesquiterpenes apparently repel adult whiteflies prior to landing, presumably because it informs them that after landing they, or their offspring, may be exposed to higher and lethal concentrations of the same compounds.     

Glucose Kinetics in the Collagen-Induced Arthritis Model: An All-in-One Model to Assess Both Efficacy and Metabolic Side Effects of Glucocorticoids

Prednisolone and other glucocorticoids (GCs) are potent anti-inflammatory drugs, but chronic use is hampered by metabolic side effects. Therefore, there is an urgent medical need for improved GCs that are as effective as classical GCs but have a better safety profile. A well-established model to assess anti-inflammatory efficacy is the chronic collagen-induced arthritis (CIA) model in mice, a model with features resembling rheumatoid arthritis. Models to quantify undesired effects of glucocorticoids on glucose kinetics are less well-established. Recently, we have described a model to quantify basal blood glucose kinetics using stably-labeled glucose. In the present study, we have integrated this blood glucose kinetic model in the CIA model to enable quantification of both efficacy and adverse effects in one animal model. Arthritis scores were decreased after treatment with prednisolone, confirming the anti-inflammatory properties of GCs. Both inflammation and prednisolone induced insulin resistance as insulin secretion was strongly increased whereas blood glucose concentrations and hepatic glucose production were only slightly decreased. This insulin resistance did not directly resulted in hyperglycemia, indicating a highly adaptive compensatory mechanism in these mice. In conclusion, this ‘all-in-one’ model allows for studying effects of (novel) GC compounds on the development of arthritis and glucose kinetics in a single animal. This integrative model provides a valuable tool for investigating (drug-induced) metabolic dysregulation in an inflammatory setting.