Quantification of piscine reovirus (PRV) at different stages of Atlantic salmon Salmo salar production

The newly described piscine reovirus (PRV) appears to be associated with the development of heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon Salmo salar L. PRV seems to be ubiquitous among fish in Norwegian salmon farms, but high viral loads and tissue distribution support a causal relationship between virus and disease. In order to improve understanding of the distribution of PRV in the salmon production line, we quantified PRV by using real-time PCR on heart samples collected at different points in the life cycle from pre-smolts to fish ready for slaughter. PRV positive pre-smolts were found in about 36% of the freshwater cohorts and a general increase in viral load was observed after their transfer to seawater. A reduction in viral loads was recorded when fish approached slaughter (18 mo in sea cages). Sequencing of positive samples did not support the hypothesis that outbreaks are caused by the spreading of a particular (virulent) strain of PRV.     

Regulation of genes involved in nitrogen utilization on different C/N ratios and nitrogen sources in the model ectomycorrhizal fungus Hebeloma cylindrosporum

Nitrogen (N) utilization by ectomycorrhizal fungi is an essential aspect of their ecosystem function. N deposition changes both the N pools and the carbon/nitrogen (C/N) ratio of the substrates where ectomycorrhizal fungi are found, and it is important to understand how these changes affect the N forms used by ectomycorrhizal fungi. To overcome the difficulties of studying ectomycorrhizal fungi in situ, we investigated all known N genes in the model fungus, Hebeloma cylindrosporum in a culture study. In addition to studying the regulation of all known N utilization genes, we aimed to understand whether there are gene clusters that undergo similar regulation. Lastly we studied how C/N ratio, N transporter type, and N source affected relative gene expression levels. We grew the D2 strain of H. cylindrosporum on a range of inorganic and organic N sources under low, medium, and high C/N ratios. We found three gene clusters that were regulated in a similar pattern. Lastly, we found C/N ratio, N source and N transporter type all affected gene expression levels. Relative expression levels were highest on the high C/N ratio, BSA and diLeucine N sources, and inorganic N transporters were always expressed at higher levels than organic N transporters. These results suggest that inorganic N sources may always the default preference for H. cylindrosporum, regardless of both the N sources and the C/N ratio of the substrate.     

Grassland resistance and resilience after drought depends on management intensity and species richness

The degree to which biodiversity may promote the stability of grasslands in the light of climatic variability, such as prolonged summer drought, has attracted considerable interest. Studies so far yielded inconsistent results and in addition, the effect of different grassland management practices on their response to drought remains an open question. We experimentally combined the manipulation of prolonged summer drought (sheltered vs. unsheltered sites), plant species loss (6 levels of 60 down to 1 species) and management intensity (4 levels varying in mowing frequency and amount of fertilizer application). Stability was measured as resistance and resilience of aboveground biomass production in grasslands against decreased summer precipitation, where resistance is the difference between drought treatments directly after drought induction and resilience is the difference between drought treatments in spring of the following year. We hypothesized that (i) management intensification amplifies biomass decrease under drought, (ii) resistance decreases with increasing species richness and with management intensification and (iii) resilience increases with increasing species richness and with management intensification.We found that resistance and resilience of grasslands to summer drought are highly dependent on management intensity and partly on species richness. Frequent mowing reduced the resistance of grasslands against drought and increasing species richness decreased resistance in one of our two study years. Resilience was positively related to species richness only under the highest management treatment. We conclude that low mowing frequency is more important for high resistance against drought than species richness. Nevertheless, species richness increased aboveground productivity in all management treatments both under drought and ambient conditions and should therefore be maintained under future climates.     

Composition and function of haemolymphatic tissues in the European common shrew

Background

Studies of wild animals responding to their native parasites are essential if we are to understand how the immune system functions in the natural environment. While immune defence may bring increased survival, this may come at a resource cost to other physiological traits, including reproduction. Here, we tested the hypothesis that wild common shrews (Sorex araneus), which produce large numbers of offspring during the one breeding season of their short life span, forgo investment in immunity and immune system maintenance, as increased longevity is unlikely to bring further opportunities for mating. In particular, we predicted that adult shrews, with shorter expected lifespans, would not respond as effectively as young animals to infection.

Methodology/Principal Findings

We examined haemolymphatic tissues from wild-caught common shrews using light and transmission electron microscopy, applied in conjunction with immunohistology. We compared composition and function of these tissues in shrews of different ages, and the extent and type of inflammatory reactions observed in response to natural parasitic infections. All ages seemed able to mount systemic, specific immune responses, but adult shrews showed some signs of lymphatic tissue exhaustion: lymphatic follicles in adults (n = 21) were both smaller than those in sub-adults (n = 18; Wald = 11.1, p<0.05) and exhibited greater levels of depletion (Wald = 13.3, p<0.05).

Conclusions/Significance

Contrary to our expectations, shrews respond effectively to their natural parasites, and show little indication of immunosenescence as adults. The pancreas of Aselli, a unique lymphoid organ, may aid in providing efficient immune responses through the storage of large numbers of plasma cells. This may allow older animals to react effectively to previously encountered parasites, but infection by novel agents, and eventual depletion of plasma cell reserves, could both still be factors in the near-synchronous mortality of adult shrews observed shortly after breeding.     

The angiotensin converting enzyme inhibitory tripeptides Ile-Pro-Pro and Val-Pro-Pro show increasing permeabilities with increasing physiological relevance of absorption models

Transepithelial transport of the ACE inhibitory peptides Ile-Pro-Pro and Val-Pro-Pro was studied in different models of absorption. Apparent permeability (P(app)) values for absorptive transport across Caco-2 monolayers were 1.0+/-0.9 x 10(-8) (Ile-Pro-Pro) and 0.5+/-0.1 x 10(-8)cms(-1) (Val-Pro-Pro). Ex vivo transport across jejunal segments in the Ussing chamber was 5-times (Ile-Pro-Pro) to 10-times (Val-Pro-Pro) higher with no significant differences (p>0.05) observed between both peptides. The peptidase inhibitor bestatin increased permeability for the absorptive direction for Ile-Pro-Pro by twofold. Neither a transepithelial pH gradient nor increased apical tripeptide concentration nor longitudinal localization of the intestinal segment influenced P(app) in the ex vivo experiments. Val-Pro-Pro transport across Peyer's patches, however, was 4-times higher (P(app)=21.0+/-9.3 x10(-8)cms(-1)) as compared to duodenum (P(app)=4.8+/-1.4 x 10(-8)cms(-1)). In the in situ perfusion experiments P(app) values varied greatly among different animals ranging from 0.5 to 24.0 x10(-8)cms(-1) (Ile-Pro-Pro) and from 1.0 to 15.6 x 10(-8)cms(-1) (Val-Pro-Pro). In summary, Caco-2 and ex vivo absorption models differ considerably regarding their peptide permeability. The in situ model seems to be less appropriate because of the observed large variability in peptide permeability. The results of this study demonstrate that the ACE inhibitory peptides Ile-Pro-Pro and Val-Pro-Pro are absorbed partially undegraded.     

Leukemia inhibitory factor deficiency modulates the immune response and limits autoimmune demyelination: a new role for neurotrophic cytokines in neuroinflammation

The neurotrophic cytokines ciliary neurotrophic factor and leukemia inhibitory factor (LIF) play a key role in neuronal and oligodendrocyte survival and as protective factors in neuroinflammation. To further elucidate the potential of endogenous LIF in modulating neuroinflammation, we studied myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis in LIF knockout mice (LIF(-/-) mice). In the late phase of active myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis, LIF(-/-) mice exhibited a markedly milder disease course. The inflammatory infiltrate in LIF(-/-) mice was characterized by an increase in neutrophilic granulocytes early and fewer infiltrating macrophages associated with less demyelination later in the disease. In good correlation with an effect of endogenous LIF on the immune response, we found an Ag-specific T cell-priming defect with impaired IFN-gamma production in LIF(-/-) mice. On the molecular level, the altered recruitment of inflammatory cells is associated with distinct patterns of chemokine production in LIF(-/-) mice with an increase of CXCL1 early and a decrease of CCL2, CCL3, and CXCL10 later in the disease. These data reveal that endogenous LIF is an immunologically active molecule in neuroinflammation. This establishes a link between LIF and the immune system which was not observed in the ciliary neurotrophic factor knockout mouse.     

Redox control of iron regulatory protein 2 stability

Iron regulatory protein 2 (IRP2) is a critical switch for cellular and systemic iron homeostasis. In iron-deficient or hypoxic cells, IRP2 binds to mRNAs containing iron responsive elements (IREs) and regulates their expression. Iron promotes proteasomal degradation of IRP2 via the F-box protein FBXL5. Here, we explored the effects of oxygen and cellular redox status on IRP2 stability. We show that iron-dependent decay of tetracycline-inducible IRP2 proceeds efficiently under mild hypoxic conditions (3% oxygen) but is compromised in severe hypoxia (0.1% oxygen). A treatment of cells with exogenous H(2)O(2) protects IRP2 against iron and increases its IRE-binding activity. IRP2 is also stabilized during menadione-induced oxidative stress. These data demonstrate that the degradation of IRP2 in iron-replete cells is not only oxygen-dependent but also sensitive to redox perturbations.     

Exosomes: vesicular carriers for intercellular communication in neurodegenerative disorders

The intercellular transfer of misfolded proteins has received increasing attention in various neurodegenerative diseases characterized by the aggregation of specific proteins, as observed in Alzheimer’s, Parkinson’s and Huntington’s disease. One hypothesis holds that intercellular dissemination of these aggregates within the central nervous system results in the seeded assembly of the cognate soluble protein in target cells, similar to that proposed for transmissible prion diseases. The molecular mechanisms underlying the intercellular transfer of these proteinaceous aggregates are poorly understood. Various transfer modes of misfolded proteins including continuous cell-cell contacts such as nanotubes, unconventional secretion or microvesicle/exosome-associated dissemination have been suggested. Cells can release proteins, lipids and nucleic acids by vesicular exocytosis pathways destined for horizontal transfer. Encapsulation into microvesicular/exosomal vehicles not only protects these molecules from degradation and dilution in the extracellular space but also facilitates delivery over large distances, e.g. within the blood flow or interstitial fluid. Specific surface ligands might allow the highly efficient and targeted uptake of these vesicles by recipient cells. In this review, we focus on the cell biology and function of neuronal microvesicles/exosomes and discuss the evidence for pathogenic intercellular protein transfer mediated by vesicular carriers.