Methyl Jasmonate Increases the Tropane Alkaloid Scopolamine and Reduces Natural Herbivory in Brugmansia suaveolens: Is Scopolamine Responsible for Plant Resistance?

The tropane alkaloid (TA) scopolamine is suggested to protect Brugmansia suaveolens (Solanaceae) against herbivorous insects. To test this prediction in a natural environment, scopolamine was induced by methyl jasmonate (MJ) in potted plants which were left 10?days in the field. MJ-treated plants increased their scopolamine concentration in leaves and herbivory decreased. These findings suggest a cause?Ceffect relationship. However, experiments in laboratory showed that scopolamine affect differently the performance of the specialist larvae of the ithomiine butterfly Placidina euryanassa (C. Felder & R. Felder) and the generalist fall armyworm Spodoptera frugiperda (J. E. Smith): the specialist that sequester this TA from B. suaveolens leaves was not negatively affected, but the generalist was. Therefore, scopolamine probably acts only against insects that are not adapted to TAs. Other compounds that are MJ elicited may also play a role in plant resistance against herbivory by generalist and specialist insects, and deserve future investigations.     

Host preferences in a phonotactic parasitoid of field crickets: the relative importance of host song characters

Abstract.  1. Predators, including insect parasitoids, often eavesdrop on prey signals, and as a result, predation can have important effects on the evolution of prey signalling behaviour.
2. The phonotactic parasitoid fly, Ormia ochracea , uses the calling songs of male field crickets to locate their field crickets hosts. In the western USA, this fly parasitises the variable field cricket, Gryllus lineaticeps . Previous work with one fly population suggested that female flies, like female field crickets, preferentially orient to male songs with higher chirp rates and longer chirp durations, although a limited range of male song types was used in this previous study. The current study, with a different fly population, used field-based, two-speaker choice tests to examine: (1) the effect of male chirp rate and chirp duration on fly attraction, using a natural range of song types; and (2) the relative importance of these song types in host selection by the flies.
3. Three lines of evidence suggested that chirp rate is more important than chirp duration in host selection. (a) The flies consistently preferred higher chirp rates but only sometimes preferred longer chirp durations. (b) The flies consistently preferred higher chirp rate/shorter chirp duration songs to lower chirp rate/longer chirp duration songs. (c) Preferences for longer chirp durations could be eliminated by increasing the amplitude of the less attractive song type, while preferences for higher chirp rates could only sometimes be eliminated by increasing the amplitude of the less attractive song type.
4. Fly predation may favour lower chirp rates and shorter chirp durations in G. lineaticeps , and may have resulted in stronger selection on chirp rate than on chirp duration.     

Statistical challenges in the analysis of two-dimensional difference gel electrophoresis experiments using DeCyder

MOTIVATION: The DeCyder software (GE Healthcare) is the current state-of-the-art commercial product for the analysis of two-dimensional difference gel electrophoresis (2D DIGE) experiments. Analyses complementing DeCyder are suggested by incorporating recent advances from the microarray data analysis literature. A case study on the effect of smallpox vaccination is used to compare the results obtained from DeCyder with the results obtained by applying moderated t-tests adjusted for multiple comparisons to DeCyder output data that was additionally normalized. RESULTS: Application of the more stringent statistical tests applied to the normalized 2D DIGE data decreased the number of potentially differentially expressed proteins from the number obtained from DeCyder and increased the confidence in detecting differential expression in human clinical studies.     

Prevalence is the preferred measure of frequency of birth defects

Researchers and other public health professionals continue to debate the use of prevalence versus incidence as the preferred term to represent the frequency of birth defects. This paper addresses this question by noting that incidence--the number of new cases of a disorder in a given at-risk population during a specified time period--cannot be reliably estimated with existing data. Consequently, it is not appropriate to use the term "incidence" in reporting the frequency of birth defects, and the term prevalence is recommended. The basis for this recommendation, and issues involved in calculating both measures, are discussed.     

Internalization and trafficking of the human and rat growth hormone-releasing hormone receptor

Internalization and intracellular trafficking of the growth hormone-releasing hormone receptor (GHRH-R) were studied in rat anterior pituitary and human (h) and rat (r) GHRH-R-transfected BHK cells, with the GHRH agonist, [N(alpha)-5-carboxyfluoresceinyl-D-Ala(2), Ala(8), Ala(15), Lys(22)]hGHRH(1-29)NH(2) (Fluo-GHRH). Time- and temperature-dependent internalization of stimulated GHRH-R was blocked by phenyl arsine oxide (PAO) in both cell types. In anterior pituitary and rGHRH-R-transfected BHK cells, only filipin III and cerulenin blocked receptor-mediated internalization of Fluo-GHRH while in hGHRH-R-transfected BHK cells, only hyperosmolar sucrose inhibited this process. These results suggest that hGHRH-R internalization is clathrin-dependent, while fatty acid acylation of rGHRH-R appears to be a prerequisite to caveolin-dependent internalization. Experiments in anterior pituitary using Bodipy-FL-C(5) ganglioside GM1, a specific marker of lipid rafts such as caveolae, confirmed this latter pathway. Co-localization of Fluo-GHRH with LysoTracker indicated that Fluo-GHRH was directed to acidic organelles in both cell types. Finally, studies using cycloheximide and monensin showed that upon stimulation with GHRH, an optimal concentration of functional GHRH-R was maintained at the plasma membrane due to de novo synthesis and recycling in pituitary cells and to de novo synthesis solely in hGHRH-R-transfected BHK cells. This first study on the dynamics of the GHRH/GHRH-R complexes using fluorescence imaging in a native environment compared to cell system models, revealed that both receptor primary structure and concentration at the plasma membrane play important roles in internalization and trafficking of specific G-protein-coupled receptors (GPCR).     

Marine reserves demonstrate trophic interactions across habitats

Several infaunal bivalve taxa show patterns of decreased biomass in areas with higher densities of adjacent reef-associated predators (the snapper, Pagrus auratus and rock lobster, Jasus edwardsii). A caging experiment was used to test the hypothesis that patterns observed were caused by predation, using plots seeded with a known initial density of the bivalve Dosinia subrosea to estimate survivorship. The caging experiment was replicated at several sites inside and outside two highly protected marine reserves: predators are significantly more abundant inside these reserves. Survivorship in fully caged, partially caged and open plots were then compared at sites having either low (non reserve) or high (reserve) predator density. The highest rates of survivorship of the bivalve were found in caged plots inside reserves and in all treatments outside reserves. However, inside reserves, open and partially caged treatments exhibited low survivorship. It was possible to specifically attribute much of this mortality to predation by large rock lobsters, due to distinctive marks on the valves of dead D. subrosea. This suggests that predation by large rock lobster could indeed account for the distributional patterns previously documented for certain bivalve populations. Our results illustrate that protection afforded by marine reserves is necessary to investigate how depletion through fishing pressure can change the role of upper-level predators and trophic processes between habitats. Electronic Supplementary Material Supplementary material is available for this article at An erratum to this article can be found at     

Compression or tension? The stress distribution in the proximal femur

Background  

Questions regarding the distribution of stress in the proximal human femur have never been adequately resolved. Traditionally, by considering the femur in isolation, it has been believed that the effect of body weight on the projecting neck and head places the superior aspect of the neck in tension. A minority view has proposed that this region is in compression because of muscular forces pulling the femur into the pelvis. Little has been done to study stress distributions in the proximal femur. We hypothesise that under physiological loading the majority of the proximal femur is in compression and that the internal trabecular structure functions as an arch, transferring compressive stresses to the femoral shaft.     

Different domains of the RNA polymerase of infectious bursal disease virus contribute to virulence

BACKGROUND: Infectious bursal disease virus (IBDV) is a pathogen of worldwide significance to the poultry industry. IBDV has a bi-segmented double-stranded RNA genome. Segments A and B encode the capsid, ribonucleoprotein and non-structural proteins, or the virus polymerase (RdRp), respectively. Since the late eighties, very virulent (vv) IBDV strains have emerged in Europe inducing up to 60% mortality. Although some progress has been made in understanding the molecular biology of IBDV, the molecular basis for the pathogenicity of vvIBDV is still not fully understood. METHODOLOGY, PRINCIPAL FINDINGS: Strain 88180 belongs to a lineage of pathogenic IBDV phylogenetically related to vvIBDV. By reverse genetics, we rescued a molecular clone (mc88180), as pathogenic as its parent strain. To study the molecular basis for 88180 pathogenicity, we constructed and characterized in vivo reassortant or mosaic recombinant viruses derived from the 88180 and the attenuated Cu-1 IBDV strains. The reassortant virus rescued from segments A of 88180 (A88) and B of Cu-1 (BCU1) was milder than mc88180 showing that segment B is involved in 88180 pathogenicity. Next, the exchange of different regions of BCU1 with their counterparts in B88 in association with A88 did not fully restore a virulence equivalent to mc88180. This demonstrated that several regions if not the whole B88 are essential for the in vivo pathogenicity of 88180. CONCLUSION, SIGNIFICANCE: The present results show that different domains of the RdRp, are essential for the in vivo pathogenicity of IBDV, independently of the replication efficiency of the mosaic viruses.     

Consistent abundance distributions of marine fishes in an old,climatically buffered,infertile seascape

Aim Macroecological theory predicts that along direct physiological gradients there will be unimodal abundance distributions of species and consistent rates of assemblage turnover. However, the majority of marine studies that have investigated the realized distribution of species along latitudinal or temperature gradients have generally found unimodal distributions to be rare. We assess fish distributions along a temperature gradient in a stable oligotrophic seascape and suggest that unimodal distributions will be more common. Location Nearshore demersal fish habitat extending 1500 km along the coast of south‐western Australia. Methods The relative abundances of demersal fish species were sampled off the coast of south‐western Australia along a temperature gradient. The confounding influence of other environmental variables was tested, and the assemblage was found to be highly correlated with temperature. For the 20 most abundant species, quantile regression spline models were used to construct a model within which 95% of their abundance was expected to fall. We compared the results from this study with the proportion of unimodal species abundance distributions observed in other studies. Results Of the 20 most abundant species, 19 displayed patterns that indicated temperature was an important factor influencing their range and relative abundance; with 15 species exhibiting unimodal abundance distributions, four having ramped distribution to one end of the sampled range and one showing no consistent pattern. Main conclusions The high diversity and percentage of endemic species in terrestrial and marine habitats of south‐western Australia is likely to be due to the stable geological and oceanographic history of the region. In comparison, studies of abundance distribution in other marine systems have been conducted in relatively heterogeneous and productive environments. The old, climatically buffered, oligotrophic seascape of south‐western Australia has provided a simple system in which the consistent influence of physiological gradients on the abundance distribution of fish species can be observed.