Measuring the discrepancy between fecundity and lifetime reproductive success in a pollinating fig wasp

Lifetime reproductive success in female insects is often egg- or time-limited. For instance in pro-ovigenic species, when oviposition sites are abundant, females may quickly become devoid of eggs. Conversely, in the absence of suitable oviposition sites, females may die before laying all of their eggs. In pollinating fig wasps (Hymenoptera: Agaonidae), each species has an obligate mutualism with its host fig tree species [Ficus spp. (Moraceae)]. These pro-ovigenic wasps oviposit in individual ovaries within the inflorescences of monoecious Ficus (syconia, or ‘figs’), which contain many flowers. Each female flower can thus become a seed or be converted into a wasp gall. The mystery is that the wasps never oviposit in all fig ovaries, even when a fig contains enough wasp females with enough eggs to do so. The failure of all wasps to translate all of their eggs into offspring clearly contributes to mutualism persistence, but the underlying causal mechanisms are unclear. We found in an undescribed Brazilian Pegoscapus wasp population that the lifetime reproductive success of lone foundresses was relatively unaffected by constraints on oviposition. The number of offspring produced by lone foundresses experimentally introduced into receptive figs was generally lower than the numbers of eggs carried, despite the fact that the wasps were able to lay all or most of their eggs. Because we excluded any effects of intraspecific competitors and parasitic non-pollinating wasps, our data suggest that some pollinators produce few offspring because some of their eggs or larvae are unviable or are victims of plant defences.

Obesity and diabetes, the built environment, and the ‘local’ food economy in the United States, 2007

Obesity and diabetes are increasingly attributed to environmental factors, however, little attention has been paid to the influence of the ‘local’ food economy. This paper examines the association of measures relating to the built environment and ‘local’ agriculture with U.S. county-level prevalence of obesity and diabetes. Key indicators of the ‘local’ food economy include the density of farmers’ markets and the presence of farms with direct sales. This paper employs a robust regression estimator to account for non-normality of the data and to accommodate outliers. Overall, the built environment is associated with the prevalence of obesity and diabetes and a strong local’ food economy may play an important role in prevention. Results imply considerable scope for community-level interventions.

Tritrophic effects of organic and conventional fertilisers on a cereal-aphid-parasitoid system

The impact of parasitoids on pests varies between conventional and low-intensity agricultural systems. Although the impacts on parasitoid natural enemies of many practices within these agricultural systems are well understood, the role of fertilisers has been less well studied. The effects of organic-based and conventional fertilisers on Hordeum vulgare L. (Poaceae), the aphid Metopolophium dirhodum Walker (Hemiptera: Aphididae), and its parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) was investigated using cage release experiments and measures of aphid and parasitoid fitness were taken. Barley tiller number and aphid weight were increased by fertilisers, particularly under conventional treatments. Adult parasitoid size correlated positively with that of the host, M. dirhodum, whereas percentage parasitism was not affected by fertiliser treatment or host size. The results suggest that the increased parasitoid impact observed in some low-intensity or organic systems is not a direct result of fertiliser treatment. Our results indicate that fertiliser treatments that improve cereal-aphid fitness will improve parasitoid fitness as measured by parasitoid size but may not influence percentage parasitism.

Energy consumption feedback in perspective: integrating Australian data to meta-analyses on in home displays

Providing homeowners with real-time feedback on their electricity consumption through a dedicated display device has been shown to reduce consumption by approximately 6-10%. However, recent advances in smart grid technology have enabled larger sample sizes and more representative sample selection and recruitment methods for display trials. By analyzing these factors using data from current studies, this paper argues that a realistic, large-scale conservation effect from feedback is in the range of 3-5%. Subsequent analysis shows that providing real-time feedback may not be a cost effective strategy for reducing carbon emissions in Australia, but that it may enable additional benefits such as customer retention and peak-load shift.

Effects of non-host plant odour on Meligethes aeneus during immigration to oilseed rape

The use of semiochemicals for the manipulation of the pollen beetle, Meliethes aeneus (Fabricius) (Coleoptera: Nitidulidae), is being investigated for potential incorporation into a push-pull strategy for this pest, which damages oilseed rape, Brassica napus L. (Brassicaceae), throughout Europe. Previous laboratory behavioural studies using volatiles from non-host plants showed that M. aeneus is repelled by the odour of lavender, Lavendula angustifolia Mill. (Lamiaceae), essential oil. This article reports on semi-field and field trials to investigate this behaviour under more realistic conditions. Semi-field experiments were conducted to assess the relative importance of olfaction at different points in host location behaviour by M. aeneus. The results showed that oilseed rape plants treated with lavender odour were less colonised by M. aeneus in comparison with an untreated control, but that the treatment effect was much reduced if the lavender odour was applied after colonisation. The field experiment demonstrated that lavender odour caused a significant reduction in the number of adultM. aeneus infesting the oilseed rape plants in the treatment plots compared to the control plots. Overall, these findings are very encouraging for the future development of a push-pull pest control system.

Can adherence to dietary guidelines address excess caloric intake? An empirical assessment for the UK

The facilitation of healthier dietary choices by consumers is a key element of government strategies to combat the rising incidence of obesity in developed and developing countries. Public health campaigns to promote healthier eating often target compliance with recommended dietary guidelines for consumption of individual nutrients such as fats and added sugars. This paper examines the association between improved compliance with dietary guidelines for individual nutrients and excess calorie intake, the most proximate determinant of obesity risk. We apply quantile regressions and counterfactual decompositions to cross-sectional data from the National Diet and Nutrition Survey (2000-01) to assess how excess calorie consumption patterns in the UK are likely to change with improved compliance with dietary guidelines. We find that the effects of compliance vary significantly across different quantiles of calorie consumption. Our results show that compliance with dietary guidelines for individual nutrients, even if successfully achieved, is likely to be associated with only modest shifts in excess calorie consumption patterns. Consequently, public health campaigns that target compliance with dietary guidelines for specific nutrients in isolation are unlikely to have a significant effect on the obesity risk faced by the population.

MALDI mass spectrometry in prostate cancer biomarker discovery

Matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry (MS) is a highly versatile and sensitive analytical technique, which is known for its soft ionisation of biomolecules such as peptides and proteins. Generally, MALDI MS analysis requires little sample preparation, and in some cases like MS profiling it can be automated through the use of robotic liquid-handling systems. For more than a decade now, MALDI MS has been extensively utilised in the search for biomarkers that could aid clinicians in diagnosis, prognosis, and treatment decision making. This review examines the various MALDI-based MS techniques like MS imaging, MS profiling and proteomics in-depth analysis where MALDI MS follows fractionation and separation methods such as gel electrophoresis, and how these have contributed to prostate cancer biomarker research. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.

Efficacy of a live attenuated Escherichia coli O78:K80 vaccine in chickens and turkeys

A candidate live vaccine for avian pathogenic Escherichia coli (APEC) was constructed from a virulent field APEC O78 strain by mutation of the aroA gene. The mutant was highly similar to the parent wild-type strain in respect of colony morphology, motility, growth in suspension, hemagglutination, Congo Red binding, HEp-2 cell adhesion, and the elaboration of surface antigens type 1 fimbriae and flagella, although production of curli fimbriae was reduced marginally. The mutant proved avirulent when inoculated into 1-day-old chicks by spray application and when presented again in the drinking water at 7 days of age. Chickens and turkeys vaccinated with an O78 aroA mutant were protected against a challenge at 6 wk of age by virulent APEC strains.

Density of insect-pollinated grassland plants decreases with increasing surrounding land-use intensity

Pollinator declines have raised concerns about the persistence of plant species that depend on insect pollination, in particular by bees, for their reproduction. The impact of pollinator declines remains unknown for species-rich plant communities found in temperate seminatural grasslands. We investigated effects of land-use intensity in the surrounding landscape on the distribution of plant traits related to insect pollination in 239 European seminatural grasslands. Increasing arable land use in the surrounding landscape consistently reduced the density of plants depending on bee and insect pollination. Similarly, the relative abundance of bee-pollination-dependent plants increased with higher proportions of non-arable agricultural land (e.g. permanent grassland). This was paralleled by an overall increase in bee abundance and diversity. By isolating the impact of the surrounding landscape from effects of local habitat quality, we show for the first time that grassland plants dependent on insect pollination are particularly susceptible to increasing land-use intensity in the landscape.

Behavioural responses of the aphid parasitoid Diaeretiella rapae to volatiles from Arabidopsis thaliana induced by Myzus persicae

In response to herbivory by insects, several plant species have been shown to produce volatiles that attract the natural enemies of those herbivores. Using a Y-tube olfactometer, we investigated responses of the aphid parasitoid Diaeretiella rapae MacIntosh (Hymenoptera: Aphidiidae) to volatiles from Arabidopsis thaliana Columbia (Brassicaceae) plants that were either undamaged, infested by the peach-potato aphid, Myzus persicae Sulzer (Homoptera: Aphididae), or mechanically damaged, as well as to volatiles from just the aphid or its honeydew. In dual-choice experiments, female D. rapae given oviposition experience on A. thaliana infested with M. persicae were significantly attracted to volatiles from A. thaliana infested with M. persicae over volatiles from undamaged A. thaliana and similarly were significantly attracted to plants that had been previously infested by M. persicae, but from which the aphids were removed, over undamaged plants. Diaeretiella rapae did not respond to volatiles from M. persicae alone, their honeydew, or plants mechanically damaged with either a pin or scissors. We conclude that an interaction between the plant and the aphid induces A. thaliana to produce volatiles, which D. rapae can learn and respond to. Poor responses of D. rapae to volatiles from an A. thaliana plant that had two leaves infested with M. persicae, with the two infested leaves being removed before testing, suggested the possibility that, at this stage of infestation, the majority of volatile production induced by M. persicae may be localized to the infested tissues of the plant. We conclude that this tritrophic interaction is a suitable model system for future investigations of the biochemical pathways involved in the production of aphid-induced volatiles attractive to natural enemies.

Delivery of crop pollination services is an insufficient argument for wild pollinator conservation

There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.

Key bioactive reaction products of the NO/H2S interaction are S/N-hybrid species, polysulfides, and nitroxyl

Experimental evidence suggests that nitric oxide (NO) and hydrogen sulfide (H2S) signaling pathways are intimately intertwined, with mutual attenuation or potentiation of biological responses in the cardiovascular system and elsewhere. The chemical basis of this interaction is elusive. Moreover, polysulfides recently emerged as potential mediators of H2S/sulfide signaling, but their biosynthesis and relationship to NO remain enigmatic. We sought to characterize the nature, chemical biology, and bioactivity of key reaction products formed in the NO/sulfide system. At physiological pH, we find that NO and sulfide form a network of cascading chemical reactions that generate radical intermediates as well as anionic and uncharged solutes, with accumulation of three major products: nitrosopersulfide (SSNO−), polysulfides, and dinitrososulfite N-nitrosohydroxylamine-N-sulfonate (SULFI/NO), each with a distinct chemical biology and in vitro and in vivo bioactivity. SSNO− is resistant to thiols and cyanolysis, efficiently donates both sulfane sulfur and NO, and potently lowers blood pressure. Polysulfides are both intermediates and products of SSNO− synthesis/decomposition, and they also decrease blood pressure and enhance arterial compliance. SULFI/NO is a weak combined NO/nitroxyl donor that releases mainly N2O on decomposition; although it affects blood pressure only mildly, it markedly increases cardiac contractility, and formation of its precursor sulfite likely contributes to NO scavenging. Our results unveil an unexpectedly rich network of coupled chemical reactions between NO and H2S/sulfide, suggesting that the bioactivity of either transmitter is governed by concomitant formation of polysulfides and anionic S/N-hybrid species. This conceptual framework would seem to offer ample opportunities for the modulation of fundamental biological processes governed by redox switching and sulfur trafficking.

Nitrosopersulfide (SSNO-) targets soluble guanylyl cyclase and induces vasodilation in vivo

Background Recent experimental evidence suggests that nitric oxide (NO) and hydrogen sulfide signaling pathways are intimately intertwined particularly in the vasculature, with mutual attenuation or potentiation of biological responses under control of the soluble guanylyl cyclase (sGC) / phopshodiesterase (PDE) pathway. There is now compelling evidence that part of the NO/sulfide cross talk has a chemical foundation via the formation of S/N-hybrid molecules including thionitrous acid (HSNO) and nitrosopersulfde (SSNO-). The aim of this study was to characterize the bioactive products of the interaction between sulfide and NO metabolites targeting sGC that may potentially regulate vasodilation. Results We found that the chemical interaction of sulfide with NO or nitrosothiols leads to formation of S/N-hybrid metabolites including SSNO- via intermediate formation of HSNO. Contrary to a recent report in the literature but consistent with the transient nature of HSNO, its formation was not detectable by high-resolution mass spectrometry under physiologically relevant conditions. SSNO- is also formed in non-aqueous media by the reaction of nitrite with oxidized sulfur species including colloidal sulfur and polysulfides. SSNO- is stable in the presence of high concentrations of thiols, release NO, and activates sGC in RFL-6 cells in an NO-dependent fashion. Moreover, SSNO- is a potent vasodilator in aortic rings in vitro and lowers blood pressure in rats in vivo. The presence of high concentrations of SOD or thiols does not affect SSNO- mediated sGC activation, while it potentiates and inhibits the effects of the nitroxyl (HNO) donor Angeli's salt, suggesting that HNO release from SSNO- is not involved in sGC activation. Conclusion The reaction between NO and sulfide leads to fomation of S/N-hybrid molecules including SSNO-, releasing NO, activating sGC and inducing vasodilation. SSNO- is considerably more stable than HSNO at pH 7.4 and thus a more likely biological mediator that can account for the chemical cross-talk between NO and sulfide.

Testosterone is associated with self-employment among Australian men

Testosterone has pronounced effects on men’s physiological development and smaller, more nuanced, impacts on their economic behavior. In this study of 1199 Australian adult males, we investigate the relationship between the self-employed and their serum testosterone levels. Because prior studies have identified that testosterone is a hormone that is responsive to external factors (e.g. competition, risk-taking), we explicitly control for omitted variable bias and reverse causality by using an instrumental variable approach. We use insulin as our primary instrument to account for endogeneity between testosterone and self-employment. This is because prior research has identified a relationship between insulin and testosterone but not between insulin and self-employment. Our results show that there is a positive association between total testosterone and self-employment. Robustness checks using bioavailable testosterone and another similar instrument (daily alcohol consumption) confirm this positive finding.

Endothelin signalling in the cardiac myocyte and its pathophysiological relevance

Endothelin A (ET(A)) transmembrane receptors predominate in rat cardiac myocytes. These are G protein-coupled receptors whose actions are mediated by the G(q) heterotrimeric G proteins. Through these, ET-1 binding to ET(A)-receptors stimulates the hydrolysis of membrane phosphatidylinositol 4,5-bisphosphate to diacylglycerol and inositol 1,4,5-trisphosphate. Diacylglycerol remains in the membrane whereas inositol 1,4,5-trisphosphate is soluble (though its importance in the cardiac myocyte is still debated). Isoforms of the phospholipid-dependent protein kinase, protein kinase C (PKC), are intracellular receptors for diacylglycerol. Cytoplasmic nPKCdelta and nPKCepsilon detect increases in membrane diacylglycerols and translocate to the membrane. This brings about PKC activation, though modifications additional to binding to phospholipids and diacylglycerol are involved. The next event (probably associated with PKC activation) is the activation of the membrane-bound small G protein Ras by exchange of GTP for GDP. Ras.GTP loading translocates Raf family mitogen-activated protein kinase (MAPK) kinase kinases to the membrane, initiates the activation of Raf, and thus activates the extracellular signal-regulated kinase 1/2 (ERK1/2) cascade. Over longer times, two analogous protein kinase cascades, the c-Jun N-terminal kinase and p38-mitogen-activated protein kinase cascades, become activated. As the signals originating from the ET(A) receptor are transmitted through these protein kinase pathways, other signalling molecules become phosphorylated, thus changing their biological activities. For example, ET-1 increases the expression of the c-jun transcription factor gene, and increases abundance and phosphorylation of c-Jun protein. These changes in c-Jun expression and phosphorylation are likely to be important in the regulation of gene transcription.