Contribution of subsurface peat to CO2 and CH4 fluxes in a neotropical peatland

Tropical peatlands play an important role in the global carbon cycling but little is known about factors regulating carbon dioxide (CO₂) and methane (CH₄) fluxes from these ecosystems. Here, we test the hypotheses that (i) CO₂ and CH₄ are produced mainly from surface peat and (ii) that the contribution of subsurface peat to net C emissions is governed by substrate availability. To achieve this, in situ and ex situ CO₂ and CH₄ fluxes were determined throughout the peat profiles under three vegetation types along a nutrient gradient in a tropical ombrotrophic peatland in Panama. The peat was also characterized with respect to its organic composition using ¹³C solid state cross‐polarization magic‐angle spinning nuclear magnetic resonance spectroscopy. Deep peat contributed substantially to CO₂ effluxes both with respect to actual in situ and potential ex situ fluxes. CH₄ was produced throughout the peat profile with distinct subsurface peaks, but net emission was limited by oxidation in the surface layers. CO₂ and CH₄ production were strongly substrate‐limited and a large proportion of the variance in their production (30% and 63%, respectively) was related to the quantity of carbohydrates in the peat. Furthermore, CO₂ and CH₄ production differed between vegetation types, suggesting that the quality of plant‐derived carbon inputs is an important driver of trace gas production throughout the peat profile. We conclude that the production of both CO₂ and CH₄ from subsurface peat is a substantial component of the net efflux of these gases, but that gas production through the peat profile is regulated in part by the degree of decomposition of the peat.     

The interferon-inducible gene viperin restricts West Nile virus pathogenesis

Type I interferon (IFN) signaling coordinates an early antiviral program in infected and uninfected cells by inducing IFN-stimulated genes (ISGs) that modulate viral entry, replication, and assembly. However, the specific antiviral functions in vivo of most ISGs remain unknown. Here, we examined the contribution of the ISG viperin to the control of West Nile virus (WNV) in genetically deficient cells and mice. While modest increases in levels of WNV replication were observed for primary viperin(-/-) macrophages and dendritic cells, no appreciable differences were detected in deficient embryonic cortical neurons or fibroblasts. In comparison, viperin(-/-) adult mice infected with WNV via the subcutaneous or intracranial route showed increased lethality and/or enhanced viral replication in central nervous system (CNS) tissues. In the CNS, viperin expression was induced in both WNV-infected and adjacent uninfected cells, including activated leukocytes at the site of infection. Our experiments suggest that viperin restricts the infection of WNV in a tissue- and cell-type-specific manner and may be an important ISG for controlling viral infections that cause CNS disease.     

Evaluation of approaches for measuring taxonomic completeness of lake profundal macroinvertebrate assemblages

1. Benthic macroinvertebrates (MI) are commonly used to assess freshwater ecosystems with the reference condition approach. Such assessments necessitate control for natural community variation, either by categorical typologies or by predictive models that have been widely and successfully developed for running water biota but not previously for lake profundal invertebrates. 2. We evaluated four modelling techniques [multivariate regression tree (MRT), limiting environmental differences, nonparametric multiplicative regression (NPMR) and River Invertebrate Prediction And Classification System (RIVPACS) and the operative Finnish lake typology for assessing taxonomic completeness (observed‐to‐expected number of taxa, O/E) of profundal MI assemblages. We used data from 74 and 33 minimally disturbed reference lake basins for calibration and validation of the approaches, respectively, and 72 test basins subject to various anthropogenic pressures to evaluate sensitivity to detect impact. Either all predicted taxa (threshold probability of capture P_t = 0+) or only those predicted to be captured with ≥0.25 probability were used to calculate O/E. 3. With P_t = 0.25, all four modelling approaches were accurate (mean O/E = 0.966–1.053) but imprecise (SD of O/E = 0.279–0.304) in predicting the fauna actually observed in validation sites. All models were subtly more precise than a null model (mean 1.038, SD 0.343) or the typology (1.046, 0.327). The taxon‐specific NPMR model was slightly more precise than the other three models based on site groupings. 4. The O/E values correlated relatively weakly (r = 0.55–0.86) among the approaches, which thus produced contrasting lake‐specific assessments, despite their seemingly comparable performances. Indeed, typology, suggesting that MI assemblages were impaired in 56% of test sites, was more sensitive than the other approaches (26–46%) as an indicator of human‐induced deterioration. However, this greater ostensible sensitivity seemed to be biased, as lake morphometry, a main driver of natural community variation, remained uncontrolled by the typology. 5. Generally, our exercise illustrates the inconclusiveness of the common validation criteria for the assessment methods. The apparent poor predictability of the profundal fauna, irrespective of the method, may partly stem from large observation error, which could be alleviated by more intensive sampling. However, instead of an O/E‐taxa index, some other metric encompassing quantitative aspects might be preferable for assessing these species‐poor communities.     

Mouse-adapted ovine scrapie prion strains are characterized by different conformers of PrPSc

The agent responsible for prion disease may exist in different forms, commonly referred to as strains, with each carrying the specific information that determines its own distinct biological properties, such as incubation period and lesion profile. Biological strain typing of ovine scrapie isolates by serial passage in conventional mice has shown some diversity in ovine prion strains. However, this biological diversity remains poorly supported by biochemical prion strain typing. The protein-only hypothesis predicts that variation between different prion strains in the same host is manifest in different conformations adopted by PrPSc. Here we have investigated the molecular properties of PrPSc associated with two principal Prnp(a) mouse-adapted ovine scrapie strains, namely, RML and ME7, in order to establish biochemical prion strain typing strategies that may subsequently be used to discriminate field cases of mouse-passaged ovine scrapie isolates. We used a conformation-dependent immunoassay and a conformational stability assay, together with Western blot analysis, to demonstrate that RML and ME7 PrPSc proteins show distinct biochemical and physicochemical properties. Although RML and ME7 PrPSc proteins showed similar resistance to proteolytic digestion, they differed in their glycoform profiles and levels of proteinase K (PK)-sensitive and PK-resistant isoforms. In addition, the PK-resistant core (PrP27-30) of ME7 was conformationally more stable following exposure to guanidine hydrochloride or Sarkosyl than was RML PrP27-30. Our data show that mouse-adapted ovine scrapie strains can be discriminated by their distinct conformers of PrPSc, which provides a basis to investigate their diversity at the molecular level.     

Phase 1 Study of the E-Selectin Inhibitor GMI 1070 in Patients with Sickle Cell Anemia

Background

Sickle cell anemia is an inherited disorder of hemoglobin that leads to a variety of acute and chronic complications. Abnormal cellular adhesion, mediated in part by selectins, has been implicated in the pathophysiology of the vaso-occlusion seen in sickle cell anemia, and selectin inhibition was able to restore blood flow in a mouse model of sickle cell disease.

Methods

We performed a Phase 1 study of the selectin inhibitor GMI 1070 in patients with sickle cell anemia. Fifteen patients who were clinically stable received GMI 1070 in two infusions.

Results

The drug was well tolerated without significant adverse events. There was a modest increase in total peripheral white blood cell count without clinical symptoms. Plasma concentrations were well-described by a two-compartment model with an elimination T_1/2 of 7.7 hours and CLr of 19.6 mL/hour/kg. Computer-assisted intravital microscopy showed transient increases in red blood cell velocity in 3 of the 4 patients studied.

Conclusions

GMI 1070 was safe in stable patients with sickle cell anemia, and there was suggestion of increased blood flow in a subset of patients. At some time points between 4 and 48 hours after treatment with GMI 1070, there were significant decreases in biomarkers of endothelial activation (sE-selectin, sP-selectin, sICAM), leukocyte activation (MAC-1, LFA-1, PM aggregates) and the coagulation cascade (tissue factor, thrombin-antithrombin complexes). Development of GMI 1070 for the treatment of acute vaso-occlusive crisis is ongoing.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00911495","term_id":"NCT00911495"}}NCT00911495     

Nondegradative role of Atg5-Atg12/ Atg16L1 autophagy protein complex in antiviral activity of interferon gamma

Host resistance to viral infection requires type I (α/β) and II (γ) interferon (IFN) production. Another important defense mechanism is the degradative activity of macroautophagy (herein autophagy), mediated by the coordinated action of evolutionarily conserved autophagy proteins (Atg). We show that the Atg5-Atg12/Atg16L1 protein complex, whose prior known function is in autophagosome formation, is required for IFNγ-mediated host defense against murine norovirus (MNV) infection. Importantly, the direct antiviral activity of IFNγ against MNV in macrophages required Atg5-Atg12, Atg7, and Atg16L1, but not induction of autophagy, the degradative activity of lysosomal proteases, fusion of autophagosomes and lysosomes, or the Atg8-processing protein Atg4B. IFNγ, via Atg5-Atg12/Atg16L1, inhibited formation of the membranous cytoplasmic MNV replication complex, where Atg16L1 localized. Thus, the Atg5-Atg12/Atg16L1 complex performs a pivotal, nondegradative role in IFNγ-mediated antiviral defense, establishing that multicellular organisms have evolved to use portions of the autophagy pathway machinery in a cassette-like fashion for host defense.     

The stability and aggregation of ovine prion protein associated with classical and atypical scrapie correlates with the ease of unwinding of helix-2

Susceptibility to scrapie disease in sheep, the archetypal prion disease, correlates with polymorphisms within the ovine PrP (prion-related protein) gene. The VRQ (Val136Arg154Gln171) and AL141RQ (Ala136Leu141Arg154Gln171) allelic variants are associated with classical scrapie, whereas the ARR (Ala136Arg154Arg171), AF141RQ (Ala136Phe141Arg154Gln171) and AHQ (Ala136His154Gln171) allelic variants are associated with atypical scrapie. Recent studies have suggested that there are differences in the stability of PrPSc (abnormal disease-specific conformation of PrP) associated with these different forms of scrapie. To address which structural features of ovine PrP may contribute to this difference, in the present study we have investigated the conformational stability and susceptibility to aggregation of allelic variants of ovine PrP associated with classical or atypical scrapie. We find that the melting temperature of ovine recombinant VRQ and AL141RQ PrP is higher than that of AF141RQ, AHQ and ARR. In addition, monoclonal-antibody studies show that the region around helix-1 of VRQ and AL141RQ is less accessible compared with other ovine PrP allelic variants. Furthermore, the extent of both the structural change to copper-ion-treatment and denaturant-induced aggregation was reduced in PrP associated with atypical scrapie compared with PrP associated with classical scrapie. Through the use of molecular dynamics simulations we have found that these biochemical and biophysical properties of ovine PrP correlate with the ease of unwinding of helix-2 and a concurrent conformational change of the helix-2-helix-3 loop. These results reveal significant differences in the overall stability and potential for aggregation of different allelic variants of ovine PrP and consequently have implications for the differences in stability of PrPSc associated with classical and atypical scrapie.