Gene flow and population structure of a common agricultural wild species (Microtus agrestis) under different land management regimes

The impact of landscape structure and land management on dispersal of populations of wild species inhabiting the agricultural landscape was investigated focusing on the field vole (Microtus agrestis) in three different areas in Denmark using molecular genetic markers. The main hypotheses were the following: (i) organic farms act as genetic sources and diversity reservoirs for species living in agricultural areas and (ii) gene flow and genetic structure in the agricultural landscape are influenced by the degree of landscape complexity and connectivity. A total of 443 individual voles were sampled within 2 consecutive years from two agricultural areas and one relatively undisturbed grassland area. As genetic markers, 15 polymorphic microsatellite loci (nuclear markers) and the central part of the cytochrome-b (mitochondrial sequence) were analysed for all samples. The results indicate that management (that is, organic or conventional management) was important for genetic population structure across the landscape, but that landscape structure was the main factor shaping gene flow and genetic diversity. More importantly, the presence of organically managed areas did not act as a genetic reservoir for conventional areas, instead the most important predictor of effective population size was the amount of unmanaged available habitat (core area). The relatively undisturbed natural area showed a lower level of genetic structuring and genetic diversity compared with the two agricultural areas. These findings altogether suggest that political decisions for supporting wildlife friendly land management should take into account both management and landscape structure factors.     

Glucose Metabolism and Regulation in Lactating Mink (Mustela Vison) - Effects of Low Dietary Protein Supply

Eighteen lactating mink raising litters of 6 to 7 kits were fed ad libitum from parturition on diets with 32% of ME derived from protein and decreasing fat:carbohydrate ratios [high fat:low carbohydrate (HFLC): 67:1, medium fat:medium carbohydrate (MFMC): 52:16, low fat:high carbohydrate (LFHC): 37:31]. Four weeks post partum the dams were fitted with a jugular vein catheter, and the experiment started with a 3 hours fasting period, after which the dams were fed 210kJ ME of the experimental diets. Blood samples were collected 10 and 5min before feeding and 30, 60, 90, 120, 150 and 180min postprandially. Two hours postprandially a single dose of 50µCi U-¹⁴C-labelled glucose was administered to each dam and blood samples were collected 5, 10, 20, 30, 45 and 60min after the tracer administration. Plasma concentrations of glucose and insulin 30 to 120min postprandially were higher in dams fed the LFHC diet, than in dams fed the HFLC diet, values for dams fed the MFMC diet being intermediate. Plasma glucagon concentrations were not significantly affected by dietary treatment. The glucagon:insulin ratios decreased postprandially in all dams, the response being significant in dams fed the LFHC diet. Plasma concentrations of urea were not significantly affected by dietary treatment. Plasma FFA concentrations tended to increase postprandially in dams fed the HFLC diet. Glucose turnover rates were approximately 4.0% permin in all dams, irrespective of dietary treatment. However, the daily glucose flux was lower in dams fed the HFLC diet than in dams fed the LFHC diet, and tended to be lower than in dams fed the MFMC diet. In conclusion, a dietary protein supply of 32% of ME simultaneously with a carbohydrate supply of 16% or 31% of ME had no adverse effects on glucose homeostasis or glucose metabolism in lactating mink.     

A process-oriented life-cycle assessment (LCA) model for environmental and resource-related technologies (EASETECH)

The International Journal of Life Cycle Assessment - In life-cycle assessment (LCA), environmental technologies are often modelled as “black-box processes”, where inputs and outputs are...     

The effect of Bt crops on soil invertebrates: a systematic review and quantitative meta-analysis

The ongoing debate about the ecological effects of Bt-crops calls for thorough reviews about the impact on soil biodiversity and their ecosystem services. Transgenic Bt-crops have been genetically modified by inserting a Bacillus thuriengensis gene so the plant expresses a Cry toxin aimed for insect crop pests. Non-target soil invertebrates are particularly recognized for their contribution to plant nutrient availability and turnover of organic matter and it is therefore relevant to protect these invertebrate taxa. A number of studies have compared the population abundance and biomass of soil invertebrates in agricultural fields planted with genetically modified Bt crops and their conventional counterparts. Here, were review and analyze a selection of studies on Protista, nematodes, Collembola, mites, enchytraeids, and earthworms systematically to empower the evidence for asking the question whether population abundances and biomasses of soil invertebrates are changed by Bt crops compared to conventional crops. 6110 titles were captured, of which 38 studies passed our inclusion criteria, and a final number of 22 publications were subject to data extraction. A database with 2046 records was compiled covering 36 locations and the Bt types Cry1Ab, Cry1Ac, Cry3Bb1 and Cry3Aa. Comparative effect sizes in terms of Hedges’ g were calculated irrespectively of statistical significance of effects of the source studies. Cry effects on populations were compared across the studies in a meta-analysis employing a hierarchical Bayesian approach of weighted data according to the level of replication. The temporal development of effect sizes was modelled, thereby taking into account the variable duration of the field experiments. There was considerable variation among soil invertebrate orders, but the sample size was insufficient and the sample heterogeneity too large to draw any credible conclusions on the effect of Cry at the order level. However, across orders there was no significant effect of Cry on soil invertebrates.

     

Phylogeny of the true water bugs (Nepomorpha: Hemiptera–Heteroptera) based on 16S and 28S rDNA and morphology

Abstract. Morphological characters and molecular sequence data were for the first time analysed separately and combined for the true water bugs (Hemiptera–Heteroptera, infraorder Nepomorpha). Data from forty species representing all families were included, together with two outgroup species representing the infraorders Gerromorpha and Leptopodomorpha. The morphological data matrix consisted of sixty‐five characters obtained from literature sources. Molecular data included approximately 960 bp from the mitochondrial gene 16S and the nuclear gene 28S for all forty‐two terminal taxa. The morphological dataset was analysed using maximum parsimony and the combined morphological and molecular (16S + 28S rDNA) dataset was analysed using direct optimization. A sensitivity analysis of sixteen different sets of parameters (various combinations of insertion–deletion cost and transversion costs) was undertaken. Character congruence was used as an optimality criterion to choose among competing phylogenetic hypotheses. The final hypothesis was obtained from the analysis of the combined molecular and mor phological dataset with the most congruent parameter set. This hypothesis supports the monophyly of all currently recognized families of Nepomorpha, and of the superfamilies Nepoidea (Nepidae + Belostomatidae), Corixoidea (Corixidae), Ochteroidea Ochteridae + Gelastocoridae), Notonectoidea (Notonectidae), and Pleoidea (Pleidae + Helotrephidae), but not the monophyly of the Naucoroidea (Naucoridae + Aphelocheiridae + Potamocoridae). The close relationship between the Notonectidae and Pleoidea is also supported. Our hypothesis concurs with Mahner in the placement of the Corixidae as a sister group to the remaining nepomorphan superfamilies except the Nepoidea, but differs in the placement of the Ochteroidea as a sister group to the Notonectoidea + Pleoidea. The superfamily Naucoroidea should be limited to only including the family Naucoridae and not the families Aphelocheiridae and Potamocoridae. The present analysis strongly supports a sister group relationship between the families Aphelocheiridae and Potamocoridae, a monophylum for which we propose a new superfamily, Aphelocheiroidea.     

Phylogeny and reclassification of species groups in Aquarius Schellenberg, Limnoporus Stål and Gerris Fabricius (Insecta: Hemiptera-Heteroptera, Gerridae)

Abstract. We investigated phylogenetic relationships of water striders (Hemiptera‐Heteroptera: Gerridae) from the three principal Holarctic genera, Aquarius Schellenberg, Limnoporus Stål and Gerris Fabricius with parsimony analyses of sixty‐six morphological characters and DNA sequences from mitochondrial (cytochrome c oxidase subunit I + II; large mitochondrial ribosomal subunit) and nuclear (elongation factor 1‐alpha) genes. The taxon sampling included all species of Aquarius and Limnoporus, and a dense, near complete, sample of Gerris species with representatives from all subgenera and species groups, and Gigantometra gigas (China) was selected as an outgroup species. A simultaneous analysis of all data sets gave eight equally parsimonious trees, and a strict consensus tree left only a few relationships within Gerris unresolved. While Limnoporus and Gerris each were resolved as monophyletic entities, Aquarius was found to be polyphyletic, because the Nearctic Aquarius remigis‐group, comprising A. remigis (Say), A. amplus (Drake and Harris), A. nyctalis (Drake and Hottes) and A. remigoides Gallant and Fairbairn, was placed as sister group to Gerris, while the Andean Aquarius chilensis (Berg) was sister group to all three genera. Remaining species of Aquarius comprised a sister group to the Gerris + the A. remigis‐group clade. Based on our phylogenetic reconstruction we discuss relationships within and among the three genera, reassess and diagnose species groups, and discuss zoogeographical relationships among all taxa.     

Ants suppressing plant pathogens: a review

Ant–plant mutualisms are usually regarded as driven by ants defending plants against herbivores in return for plant‐produced food rewards and housing. However, ants may provide additional services. In a review of published studies on ant–pathogen–plant interactions, we investigated whether ants’ extensive hygiene measures, including the use of ant‐produced antibiotics, extend to their host plants and reduce plant pathogen loads. From 30 reported species combinations, we found that the presence of ants lead to reduced pathogen levels in 18 combinations and to increased levels in 6. On average, ants significantly reduced pathogen incidence with 59%. This effect size did not differ significantly from effect sizes reported from meta‐analyses on herbivore protection. Thus, pathogen and herbivore protection could be of equal importance in ant–plant mutualisms. Considering the abundance of these interactions, ecological impacts are potentially high. Furthermore, awareness of this service may stimulate the development of new measures to control plant diseases in agriculture. It should be noted, though, that studies were biased toward tropical ant–plant symbioses and that the literature in the field is limited at present. Future research on plant pathogens is needed to enhance our understanding of ant–plant mutualisms and their evolution.     

DDX6 regulates sequestered nuclear CUG-expanded DMPK-mRNA in dystrophia myotonica type 1

Myotonic dystrophy type 1 (DM1) is caused by CUG triplet expansions in the 3′ UTR of dystrophia myotonica protein kinase (DMPK) messenger ribonucleic acid (mRNA). The etiology of this multi-systemic disease involves pre-mRNA splicing defects elicited by the ability of the CUG-expanded mRNA to ‘sponge’ splicing factors of the muscleblind family. Although nuclear aggregation of CUG-containing mRNPs in distinct foci is a hallmark of DM1, the mechanisms of their homeostasis have not been completely elucidated. Here we show that a DEAD-box helicase, DDX6, interacts with CUG triplet-repeat mRNA in primary fibroblasts from DM1 patients and with CUG–RNA in vitro. DDX6 overexpression relieves DM1 mis-splicing, and causes a significant reduction in nuclear DMPK-mRNA foci. Conversely, knockdown of endogenous DDX6 leads to a significant increase in DMPK-mRNA foci count and to increased sequestration of MBNL1 in the nucleus. While the level of CUG-expanded mRNA is unaffected by increased DDX6 expression, the mRNA re-localizes to the cytoplasm and its interaction partner MBNL1 becomes dispersed and also partially re-localized to the cytoplasm. Finally, we show that DDX6 unwinds CUG-repeat duplexes in vitro in an adenosinetriphosphate-dependent manner, suggesting that DDX6 can remodel and release nuclear DMPK messenger ribonucleoprotein foci, leading to normalization of pathogenic alternative splicing events.     

Pharmacological Identification of a Guanidine-Containing β-Alanine Analogue with Low Micromolar Potency and Selectivity for the Betaine/GABA Transporter 1 (BGT1)

The γ-aminobutyric acid (GABA) transporters (GATs) are key membrane transporter proteins involved in the termination of GABAergic signaling at synapses in the mammalian brain and proposed drug targets in neurological disorders such as epilepsy. To date, four different GAT subtypes have been identified: GAT1, GAT2, GAT3 and the betaine/GABA transporter 1 (BGT1). Owing to the lack of potent and subtype selective inhibitors of the non-GAT1 GABA transporters, the physiological role and therapeutic potential of these transporters remain to be fully understood. Based on bioisosteric replacement of the amino group in β-alanine or GABA, a series of compounds was generated, and their pharmacological activity assessed at human GAT subtypes. Using a cell-based [³H]GABA uptake assay, several selective inhibitors at human BGT1 were identified. The guanidine-containing compound 9 (2-amino-1,4,5,6-tetrahydropyrimidine-5-carboxylic acid hydrochloride) displayed more than 250 times greater potency than the parent compound β-alanine at BGT1 and is thus the most potent inhibitor reported to date for this subtype (IC₅₀ value of 2.5 µM). In addition, compound 9 displayed about 400, 16 and 40 times lower inhibitory potency at GAT1, GAT2 and GAT3, respectively. Compound 9 was shown to be a substrate for BGT1 and to have an overall similar pharmacological profile at the mouse orthologue. Compound 9 constitutes an interesting pharmacological tool for specifically investigating the cellular pharmacology of BGT1 and is the first small-molecule substrate identified with such a high selectivity for BGT1 over the three other GAT subtypes.     

Validation of ⁹⁹mTechnetium-labeled mebrofenin hepatic extraction method to quantify meal-induced splanchnic blood flow responses using a porcine model

The aim of this study was to evaluate the measurement of the total splanchnic blood flow (SBF) using a clinical diagnostic method based on Fick's principle and hepatic extraction of 99mTc-mebrofenin (99mTc-MBF) compared with a paraaminohippuric acid (pAH) dilution method in a porcine model. Another aim was to investigate whether enterohepatic cycling of 99mTc-MBF affected the SBF measurement. Five indwelling catheters were placed in each pig (n = 15) in the portal, mesenteric, and hepatic veins, as well as in the aorta and the vena cava. The SBF was measured using both methods. The portal blood flow; the intestinal and hepatic oxygen uptake; the net fluxes of oxygen, lactate, and glucose; and the extraction fraction (EF) of 99mTc-MBF were measured before and for 70 min after feeding. The mean baseline SBF was 2,961 ml/min vs. 2,762 ml/min measured by pAH and 99mTc-MBF, respectively, and increased significantly to 3,977 ml/min and 3,981 ml/min postprandially. The hepatic EF of 99mTc-MBF decreased from 40% at the start of the investigation to 16% 70 min after feeding. The arterial-portal difference in 99mTc-MBF concentration was 0.21% (P = 0.48), indicating no intestinal extraction or metabolism. The clinical method for measuring the SBF based on hepatic 99mTc-MBF extraction is robust compared with the indicator dilution method, despite the decrease seen in hepatic extraction of 99mTc-MBF. Because there was no difference in the content of 99mTc-MBF between the arterial and portal vein plasma, the SBF can be calculated from an arterial and a hepatic vein sample.