Analysis and management of resistance to chemotherapeutants in salmon lice,Lepeophtheirus salmonis (Copepoda: Caligidae)

In Northern Europe and Canada, the salmon louse, Lepeophtheirus salmonis (Kr?yer), seriously affects the marine phase of salmon production. Although the problem is long-standing, the development of sustainable methods of pest management has been unable to keep pace with the intensification of production, leading to large-scale reliance on very few chemotherapeutants. This runs the risk of selecting for genetically determined resistance in target organisms. There are many examples of similar evolutionary adaptations in arthropod pests of arable crops, livestock and human health. Several hundred pest species are now documented as being resistant to one or more chemical classes of insecticides and acaricides. Many of these compounds are identical or closely related to ones currently employed against salmon lice. It is, therefore, opportune to consider what lessons have been learnt from contending with resistance in terrestrial organisms, the implications for sustainable use of chemotherapeutants in aquaculture, and the potential for developing effective resistance management strategies. An EU-funded project named SEARCH (QLK2-CT-2000-00809) has been initiated to explore in more detail the diagnosis, incidence, dynamics and management of resistance to chemotherapeutants in L salmonis.     

Lethal and Sublethal Effects of Imidacloprid on Nicotine-Tolerant Myzus nicotianae and Myzus persicae

Bioassays of nicotine and imidacloprid against clones of Myzus persicae (Sulzer) and Myzus nicotianae (Blackman) from around the world demonstrated that some had low levels of resistance to both compounds. This was expressed not only as a reduced mortality, but more markedly as differential inhibition of feeding by imidacloprid concentrations in the parts per billion range. Such concentrations also reduced aphid fecundity by inhibiting the production and viability of nymphs, and this effect was more marked for susceptible aphids than for those showing reduced direct lethal and antifeedant effects.     

Evaluation of biological control of sheep parasites using Duddingtonia flagrans under commercial farming conditions on the island of Gotland, Sweden

Field trials, conducted over 3 consecutive years, were aimed at assessing farmer opinions of the practicality and effectiveness of using Duddingtonia flagrans to control nematode parasites in their flocks on the Swedish island of Gotland. These trials were also monitored by intensive parasitological investigation. On Gotland, lambing occurs in spring, and around mid-summer (late June), ewes and lambs are moved to saved pastures due to pasture deterioration caused by dry conditions. Weaned lambs are then returned to original lambing pastures in early autumn for finishing. One farm (B) was used for 2001-2003 and a second farm (N) was also used in 2002 and 2003. On each farm, two flocks (each of 20 ewes + twin lambs) were managed separately, namely: fungus group which received a daily supplement + fungal spores from lambing until the summer move (6 weeks) and: control group which received supplement only. For Farm B, the numbers of lambs that were marketed prior to the end of the grazing season, were 13, 18, 19 for the fungus treatment whereas corresponding numbers for the control treatment were 8, 16 and 11 for years 2001, 2002 and 2003, respectively. Final weights of the remaining lambs at the end of each year were also consistently heavier, and the numbers of lambs retained for finishing during winter were less, on the fungus treatment compared with the control treatment. On Farm N, similar results were recorded, with more lambs marketed earlier in the fungus group (25 and 19) compared with the control (19 and 15) in 2002 and 2003, respectively. The weights of the remaining lambs at the end of the trial in 2003 showed a 4.5 kg weight gain advantage of the fungus group compared to the controls. Tracer tests during autumn 2001 on Farm B, showed that Teladorsagia circumcincta plus Trichostrongylus spp. levels were significantly less on the fungus treatment (P=0.018). The summer/autumn of 2002 was one of the driest on record for Gotland. This resulted in very low levels of infective larval availability. But on both farms, T. circumcincta numbers were less on the fungus than on the control paddocks (P=0.048 on Farm B). In 2003 very low numbers of infective larvae were recorded in the autumn tracers for both treatments on both farms. Both farmer co-operators were encouraged with these results and consider that biological control of nematode parasites in their flocks, using D. flagrans, is of practical value.     

Characterization of step-edge barriers in organic thin-film growth

Detailed understanding of growth mechanisms in organic thin-film deposition is crucial for tailoring growth morphologies, which in turn determine the physical properties of the resulting films. For growth of the rodlike molecule para-sexiphenyl, the evolution of terraced mounds is observed by atomic force microscopy. Using methods established in inorganic epitaxy, we demonstrate the existence of an additional barrier (0.67 electron volt) for step-edge crossing-the Ehrlich-Schwoebel barrier. This result was confirmed by transition state theory, which revealed a bending of the molecule at the step edge. A gradual reduction of this barrier in the first layers led to an almost layer-by-layer growth during early deposition stage. The reported phenomena are a direct consequence of the complexity of the molecular building blocks versus atomic systems.     

Observations at mercury encounter by the plasma science experiment on mariner 10

A fully developed bow shock and magnetosheath were observed near Mercury, providing unambiguous evidence for a strong interaction between Mercury and the solar wind. Inside the sheath there is a distinct region analogous to the magnetosphere or magnetotail of Earth, populated by electrons with lower density and higher temperature than the electrons observed in the solar wind or magnetosheath. At the time of encounter, conditions were such that a perpendicular shock was observed on the inbound leg and a parallel shock was observed on the outbound leg of the trajectory, and energetic plasma electron events were detected upstream from the outbound shock crossing. The interaction is most likely not atmospheric, but the data clearly indicate that the obstacle to solar wind flow is magnetic, either intrinsic or induced. The particle fluxes and energy spectra showed large variations while the spacecraft was inside the magnetosphere, and these variations could be either spatial or temporal.     

Use of logic relationships to decipher protein network organization

A major focus of genome research is to decipher the networks of molecular interactions that underlie cellular function. We describe a computational approach for identifying detailed relationships between proteins on the basis of genomic data. Logic analysis of phylogenetic profiles identifies triplets of proteins whose presence or absence obey certain logic relationships. For example, protein C may be present in a genome only if proteins A and B are both present. The method reveals many previously unidentified higher order relationships. These relationships illustrate the complexities that arise in cellular networks because of branching and alternate pathways, and they also facilitate assignment of cellular functions to uncharacterized proteins.