Recalculating Australian water scarcity characterisation factors using the AWARE method

The International Journal of Life Cycle Assessment - Quantifying the impacts of water consumption on available water resources forms one of the core indicators of many life cycle assessments...     

Functional mapping of NPY/PYY receptors in rat and human gastro-intestinal tract

Peptide YY (PYY) is involved in the regulation of several gastro-intestinal functions, including motility. The aims of the present study were (i) to characterize the effects of PYY on smooth muscle strips obtained from the different gastro-intestinal segments in rats and in humans and (ii) to realize a map of the Y receptors expression. Contractions of strips were recorded under isometric conditions, using PYY and acetylcholine as control. We observed that PYY induced a contraction of muscle strips from rat proximal colon, but displayed no effect on other gut segments. Using RT-PCR, mRNA encoding the Y1 and Y4 receptors were detected in muscle strips depending on the segment. In humans, the muscle preparations responded to ACh but not to PYY. Moreover, only Y2 receptor mRNA was found in the ileum and the left colon, but not in other segments. Our study shows the heterogeneity in the expression of Y receptors along the gastro-intestinal tract, and reveals great discrepancies between rats and humans both concerning the expression of Y receptor, and the response of smooth muscle strips to PYY.     

Socio-economic and Climate Factors Associated with Dengue Fever Spatial Heterogeneity: A Worked Example in New Caledonia

Background/Objectives

Understanding the factors underlying the spatio-temporal distribution of infectious diseases provides useful information regarding their prevention and control. Dengue fever spatio-temporal patterns result from complex interactions between the virus, the host, and the vector. These interactions can be influenced by environmental conditions. Our objectives were to analyse dengue fever spatial distribution over New Caledonia during epidemic years, to identify some of the main underlying factors, and to predict the spatial evolution of dengue fever under changing climatic conditions, at the 2100 horizon.

Methods

We used principal component analysis and support vector machines to analyse and model the influence of climate and socio-economic variables on the mean spatial distribution of 24,272 dengue cases reported from 1995 to 2012 in thirty-three communes of New Caledonia. We then modelled and estimated the future evolution of dengue incidence rates using a regional downscaling of future climate projections.

Results

The spatial distribution of dengue fever cases is highly heterogeneous. The variables most associated with this observed heterogeneity are the mean temperature, the mean number of people per premise, and the mean percentage of unemployed people, a variable highly correlated with people''s way of life. Rainfall does not seem to play an important role in the spatial distribution of dengue cases during epidemics. By the end of the 21st century, if temperature increases by approximately 3°C, mean incidence rates during epidemics could double.

Conclusion

In New Caledonia, a subtropical insular environment, both temperature and socio-economic conditions are influencing the spatial spread of dengue fever. Extension of this study to other countries worldwide should improve the knowledge about climate influence on dengue burden and about the complex interplay between different factors. This study presents a methodology that can be used as a step by step guide to model dengue spatial heterogeneity in other countries.     

Sequence-based Network Completion Reveals the Integrality of Missing Reactions in Metabolic Networks

Genome-scale metabolic models are central in connecting genotypes to metabolic phenotypes. However, even for well studied organisms, such as Escherichia coli, draft networks do not contain a complete biochemical network. Missing reactions are referred to as gaps. These gaps need to be filled to enable functional analysis, and gap-filling choices influence model predictions. To investigate whether functional networks existed where all gap-filling reactions were supported by sequence similarity to annotated enzymes, four draft networks were supplemented with all reactions from the Model SEED database for which minimal sequence similarity was found in their genomes. Quadratic programming revealed that the number of reactions that could partake in a gap-filling solution was vast: 3,270 in the case of E. coli, where 72% of the metabolites in the draft network could connect a gap-filling solution. Nonetheless, no network could be completed without the inclusion of orphaned enzymes, suggesting that parts of the biochemistry integral to biomass precursor formation are uncharacterized. However, many gap-filling reactions were well determined, and the resulting networks showed improved prediction of gene essentiality compared with networks generated through canonical gap filling. In addition, gene essentiality predictions that were sensitive to poorly determined gap-filling reactions were of poor quality, suggesting that damage to the network structure resulting from the inclusion of erroneous gap-filling reactions may be predictable.     

Nitrite reduces cytoplasmic acidosis under anoxia

The ameliorating effect of nitrate on the acidification of the cytoplasm during short-term anoxia was investigated in maize (Zea mays) root segments. Seedlings were grown in the presence or absence of nitrate, and changes in the cytoplasmic and vacuolar pH in response to the imposition of anoxia were measured by in vivo (31)P nuclear magnetic resonance spectroscopy. Soluble ions and metabolites released to the suspending medium by the anoxic root segments were measured by high-performance liquid chromatography and (1)H nuclear magnetic resonance spectroscopy, and volatile metabolites were measured by gas chromatography and gas chromatography-mass spectrometry. The beneficial effect of nitrate on cytoplasmic pH regulation under anoxia occurred despite limited metabolism of nitrate under anoxia, and modest effects on the ions and metabolites, including fermentation end products, released from the anoxic root segments. Interestingly, exposing roots grown and treated in the absence of nitrate to micromolar levels of nitrite during anoxia had a beneficial effect on the cytoplasmic pH that was comparable to the effect observed for roots grown and treated in the presence of nitrate. It is argued that nitrate itself is not directly responsible for improved pH regulation under anoxia, contrary to the usual assumption, and that nitrite rather than nitrate should be the focus for further work on the beneficial effect of nitrate on flooding tolerance.     

Entomological and functional role of floral strips in an organic apple orchard: Hymenopteran parasitoids as a case study

Habitat manipulation techniques improve the availability of resources required by natural enemies to increase their effectiveness. This study focused on the effects of floral strips on Hymenopteran parasitoid presence. The experiments were conducted during spring 2007 in one organic low-input apple orchard located in south-eastern France. The density and the diversity of parasitic wasps collected from sown floral strips were higher than those from mown plants. The family of parasitic wasps of Braconidae was strongly dominant, followed by Mymaridae and Pteromalidae. By studying 26 flowering species, the greatest diversity and density of parasitic wasps were collected from Potentilla reptans, Achillea millefolium, Trifolium repens and Torilis arvensis. In terms of the early flowering plants, the most important results were observed in Euphorbia helioscopia, Senecio vulgaris and Veronica persica. To give an idea of the functional role of these plants, we studied the parasitic wasps of the diapausing larvae (cocoon) of codling moth Cydia pomonella. We recorded three emerged species: Ascogaster quadridentata, Pristomerus vulnerator and the hyperparasite Perilampus fulvicornis. However, none of these species have been observed on the 26 studied plants. Hence, this result may be suggesting that the studied plants do not have a functional role concerning these parasitoids. These studies may be advantageous for biological control programs in order to select flowering plant species attracting parasitic wasps specific to fruit pests.     

Separating the effects of prey size and speed on the kinematics of prey capture in the omnivorous lizard Gerrhosaurus major

Feeding behavior is known to be modulated as prey properties change. During prey capture, external prey properties, including size and mobility, are likely some of the most important components in predator–prey interactions. Whereas prey size has been demonstrated to elicit modulation of jaw movements during capture, how prey speed affects the approach and capture of prey remains unknown. We quantified the kinematics associated with movements of both the feeding and locomotor systems during prey capture in a lizard, Gerrhosaurus major, while facing prey differing in size and mobility (newborn mice, grasshoppers, and mealworms). Our data show that the feeding and locomotor systems were recruited differently in response to changes in the size or speed of the prey. The timing of jaw movements and of the positioning of the head are affected by changes in prey size—and speed, to a lesser extent. Changes in prey speed resulted in concomitant changes in the speed of strike and an early and greater elevation of the neck. External prey properties, and prey mobility in particular, are relevant in predator–prey interactions and elicit specific responses in different functional systems.     

Calcium Dynamics During Physiological Acidification in Xenopus Oocyte

Interplays between intracellular pH (pHi) and calcium ([Ca²⁺]_i) variations remain unclear, though both proton and calcium homeostasis changes accompany physiological events such as Xenopus laevis oocyte maturation. In this report, we used NH₄Cl and changes of extracellular pH (pHe) to acidify the cytosol in a physiological range. In oocytes voltage-clamped at −80 mV, NH₄Cl triggered an inward current, the main component of which is a Ca²⁺-dependent chloride current. Calcium imaging confirmed that NH₄Cl provoked a [Ca²⁺]_i increase. The mobilized sources of calcium were discriminated using the triple-step protocol as a means to follow both the calcium-activated chloride currents (ICl-Ca) and the hyperpolarization- and acid-activated nonselective cation current (I_In). These currents were stimulated during external addition of NH₄Cl. This upregulation was abolished by BAPTA-AM, caffeine and heparin. By both buffering pHi changes with MOPS and by inhibiting calcium influx with lanthanum, intracellular acidification, initiated by NH₄Cl and extracellular acidic medium, was shown to trigger a [Ca²⁺]_i increase through both calcium release and calcium influx. The calcium pathways triggered by pHe changes are similar to those activated by NH₄Cl, thus suggesting that there is a robust signaling mechanism allowing the cell to adjust to variable environmental conditions.