Summer irrigation,grazing and seed addition differentially influence community composition in an invaded serpentine grassland

Community assembly theory predicts that resource availability, biotic interactions, and dispersal dynamics will determine community composition. Recent work has demonstrated that manipulating these processes or “filters” to exclude exotic species may assist in restoring invaded plant communities. In this study, we began by manipulating an abiotic filter, summer water availability, on the theory that irrigation prior to the growing season could trigger the germination of exotic species during unfavorable environmental conditions. First, we performed a greenhouse experiment to assess the germination traits of 23 native and exotic species at low (16°C, spring) and high (30°C, summer) temperatures. At summer temperatures, we found high emergence of many exotic and native grasses and low emergence of native forbs suggesting that summer irrigation may help deplete the exotic seed bank. In a second experiment, we established field plots to test the efficacy of summer irrigation and simultaneously manipulated a biotic and a dispersal filter, subjecting some plots to grazing and/or native seed addition. Summer irrigation and seed addition had no effect on percent cover or species richness while grazing reduced native cover but increased native species richness and soil nitrogen content. Our data suggest that manipulating grazing (a biotic filter) may be more effective than altering abiotic or dispersal filters when restoring invaded serpentine grassland. However, summer irrigation may also be effective, if applied at lower temperatures or for longer periods.     

A novel binding assay identifies high affinity ligands to the rosiglitazone binding site of mitoNEET

A novel outer mitochondrial membrane protein containing [2Fe-2S] clusters, mitoNEET was first identified through its binding to the anti-diabetic drug pioglitazone. Pioglitazone belongs to a family of drugs that are peroxisome proliferator-activated receptor (PPAR) gamma agonists, collectively known as glitazones. With the lack of pharmacological tools available to fully elucidate mitoNEET's function, we developed a binding assay to probe the glitazone binding site with the aim of developing selective and high affinity compounds. We used multiple thiazolidine-2,4-dione (TZD), 2-thioxothiazolidin-4-one (TTD), and 2-iminothiazolidin-4-one (ITD) compounds to establish several trends to enhance ligand development for the purpose of elucidating mitoNEET function.     

Testing the molecular and evolutionary causes of a 'leapfrog' pattern of geographical variation in coloration

Understanding the mechanisms accounting for the evolution of phenotypic diversity is central to evolutionary biology. We use molecular and phenotypic data to test hypotheses for 'leapfrog' patterns of geographical variation, in which phenotypically similar, disjunct populations are separated by distinct populations of the same species. Phylogenetic reconstructions revealed independent evolution of melanic plumage characters in different populations in the Neotropical avian genus Arremon. Thus, phenotypic similarities between distant populations cannot be explained by close phylogenetic affinity. Nor can they be attributed to recurring mutations in the MC1R gene, a locus involved in melanic pigmentation. A coalescent analysis indicates that plumage traits have become fixed at a faster rate than expected under genetic drift, suggesting that selection underlies their repeated evolution. In contrast to views that genetic drift drives phenotypic differentiation in Neotropical montane birds, our results imply that geographical variation preceding speciation may reflect the action of deterministic selective processes.     

Proteomic analysis of human cataract aqueous humour: Comparison of one-dimensional gel LCMS with two-dimensional LCMS of unlabelled and iTRAQ®-labelled specimens

In this study, we report a comparative and quantitative analysis by mass spectrometry of the protein content of aqueous humour from cataract (control) patients. In addition to protein profiling, the approach is layered with quantitative proteomics using the iTRAQ? methodology. Aqueous humour from ten clinically-matched patients was collected and depleted of albumin and immunoglobulin G. Pairs of patient material were pooled and divided into three aliquots for subsequent analysis by alternative proteomic approaches. Excluding keratin, trypsin, residual albumin and immunoglobulins, a total of 198 protein groups were identified across the entire study. Relative protein quantitation with iTRAQ? revealed that 88% of the proteins had a maximal ±2-fold differential regulation between 3 of the 4 labelled samples, indicating minimal variation. The identified proteins were categorised by gene ontology and one third of the proteins were annotated as extracellular. The major molecular functions of the proteins in aqueous humour are binding (protein, metal ion, heparin, and DNA) and inhibition of proteolytic activity. Complementary to molecular function, the predominant biological processes for the proteins in aqueous humour are assigned to inflammatory and immune responses, and transport.     

Natural killer (NK) and lymphokine-activated killer (LAK) cell functions from healthy dogs and 29 dogs with a variety of spontaneous neoplasms

To investigate natural killer (NK) and lymphokine-activated killer (LAK) cell functions from 10 healthy dogs and 29 dogs with a variety of spontaneous neoplasms, large granular lymphocytes (LGLs) from blood samples were separated by a 58.5% Percoll density gradient. LGLs were stimulated with a low dose of recombinant human interleukin 2 (rhIL-2) for 7 days. Cytotoxicity of effector cells against the susceptible CTAC cell line was measured before and after stimulation. Compared with those before stimulation, the percentage of LGLs after stimulation with rhIL-2 was found to be significantly increased (P<0.01) in both dogs with tumors and controls. However, the increase was significantly higher in control animals, indicating a defect in proliferation ability of NK cells in canine tumor patients. After stimulation with rhIL-2, lymphokine-activated killer (LAK) cell activity in dogs with tumors was significantly lower (P<0.01) when compared with controls. Reduced cytotoxicity of rhIL-2–activated NK cells in dogs with tumors seems to be attributable to the presence of a diminished proliferative capacity of NK cells and a decreased ability of LAK cells to lyse target cells. Further knowledge of the precise function of IL-2–activated NK cells in dogs with tumors may help to optimize new and therapeutically beneficial treatment strategies in canine and human cancer patients. Our findings suggest that the dog could also serve as a relevant large animal model for cancer immunotherapy with IL-2.     

Spatial models of virus-immune dynamics

To date, the majority of theoretical models describing the dynamics of infectious diseases in vivo are based on the assumption of well-mixed virus and cell populations. Because many infections take place in solid tissues, spatially structured models represent an important step forward in understanding what happens when the assumption of well-mixed populations is relaxed. Here, we explore models of virus and virus-immune dynamics where dispersal of virus and immune effector cells was constrained to occur locally. The stability properties of our spatial virus-immune dynamics models remained robust under almost all biologically plausible dispersal schemes, regardless of their complexity. The various spatial dynamics were compared to the basic non-spatial dynamics and important differences were identified: When space was assumed to be homogeneous, the dynamics generated by non-spatial and spatially structured models differed substantially at the peak of the infection. Thus, non-spatial models may lead to systematic errors in the estimates of parameters underlying acute infection dynamics. When space was assumed to be heterogeneous, spatial coupling not only changed the equilibrium properties of the uncoupled populations but also equalized the dynamics and thereby reduced the likelihood of dynamic elimination of the infection. In line with experimental and clinical observations, long-lasting oscillation periods were virtually absent. When source-sink dynamics were considered, the long-term outcome of the infection depended critically on the degree of spatial coupling. The infection collapsed when emigration from source sites became too large. Finally, we discuss the implications of spatially structured models on medical treatment of infectious diseases, and note that a huge gap exists in data accurately describing infection dynamics in solid tissues.     

A series of 5-(5,6)-dihydrouracil substituted 8-hydroxy-[1,6]naphthyridine-7-carboxylic acid 4-fluorobenzylamide inhibitors of HIV-1 integrase and viral replication in cells

Introduction of a 5,6-dihydrouracil functionality in the 5-position of N-(4-fluorobenzyl)-8-hydroxy-[1,6]naphthyridine-7-carboxamide 1 led to a series of highly active HIV-1 integrase inhibitors. These compounds displayed low nanomolar activity in inhibiting both the strand transfer process of HIV-1 integrase and viral replication in cells. Compound 11 is a 150-fold more potent antiviral agent than 1, with a CIC(95) of 40 nM in the presence of human serum. It displays good pharmacokinetics when dosed in rats and dogs.     

Perspective: Reproductive isolation caused by natural selection against immigrants from divergent habitats

The classification of reproductive isolating barriers laid out by Dobzhansky and Mayr has motivated and structured decades of research on speciation. We argue, however, that this classification is incomplete and that the unique contributions of a major source of reproductive isolation have often been overlooked. Here, we describe reproductive barriers that derive from the reduced survival of immigrants upon reaching foreign habitats that are ecologically divergent from their native habitat. This selection against immigrants reduces encounters and thus mating opportunities between individuals from divergently adapted populations. It also reduces the likelihood that successfully mated immigrant females will survive long enough to produce their hybrid offspring. Thus, natural selection against immigrants results in distinctive elements of premating and postmating reproductive isolation that we hereby dub "immigrant inviability." We quantify the contributions of immigrant inviability to total reproductive isolation by examining study systems where multiple components of reproductive isolation have been measured and demonstrate that these contributions are frequently greater than those of traditionally recognized reproductive barriers. The relevance of immigrant inviability is further illustrated by a consideration of population-genetic theory, a review of selection against immigrant alleles in hybrid zone studies, and an examination of its participation in feedback loops that influence the evolution of additional reproductive barriers. Because some degree of immigrant inviability will commonly exist between populations that exhibit adaptive ecological divergence, we emphasize that these barriers play critical roles in ecological modes of speciation. We hope that the formal recognition of immigrant inviability and our demonstration of its evolutionary importance will stimulate more explicit empirical studies of its contributions to speciation.     

The 5-lipoxygenase pathway in arterial wall biology and atherosclerosis

Leukotrienes (LTs) are powerful inflammatory lipid mediators derived from the 5-lipoxygenase (5-LO) cascade of arachidonic acid. Recent clinical, population genetic, cell biological, and mouse studies indicate participation of the 5-LO pathway in atherogenesis and arterial wall remodeling. 5-LO is expressed by leukocytes including blood monocytes, tissue macrophages, dendritic cells, neutrophils, and mast cells. LTB4 and the cysteinyl LTs LTC4, LTD4, and LTE4, act through two BLT and two cysLT receptors that are differentially expressed on hematopoietic and arterial wall cells. The precise roles of LTs or the LT receptors in cardiovascular physiology remain largely to be explored. In this review, we will discuss what is currently known about the 5-LO atherosclerosis connection. We will attempt to propose strategies to further explore potential links between the 5-LO pathway and blood vessel physiology and disease progression.     

Macrophage-specific expression of group IIA sPLA2 results in accelerated atherogenesis by increasing oxidative stress

Group IIA secretory phospholipase A2 (sPLA2) is an acute-phase protein mediating decreased plasma HDL cholesterol and increased atherosclerosis. This study investigated the impact of macrophage-specific sPLA2 overexpression on lipoprotein metabolism and atherogenesis. Macrophages from sPLA2 transgenic mice have 2.5 times increased rates of LDL oxidation (thiobarbituric acid-reactive substances formation) in vitro (59 +/- 5 vs. 24 +/- 4 nmol malondialdehyde/mg protein; P < 0.001) dependent on functional 12/15-lipoxygenase (12/15-LO). Low density lipoprotein receptor-deficient (LDLR-/-) mice were transplanted with bone marrow from either sPLA2 transgenic mice (sPLA2--> LDLR-/-; n = 19) or wild-type C57BL/6 littermates (C57 BL/6-->LDLR-/-; n = 19) and maintained for 8 weeks on chow and then for 9 weeks on a Western-type diet. Plasma sPLA2 activity and plasma lipoprotein profiles were not significantly different between sPLA2-->LDLR-/- and C57BL/6-->LDLR-/- mice. Aortic root atherosclerosis was increased by 57% in sPLA2-->LDLR-/- mice compared with C57BL/6-->LDLR-/- controls (P < 0.05). Foam cell formation in vitro and in vivo was increased significantly. Urinary, plasma, and aortic levels of the isoprostane 8,12-iso-iPF2alpha-VI and aortic levels of 12/15-LO reaction products were each significantly higher (P < 0.001) in sPLA2-->LDLR-/- compared with C57BL/6-->LDLR-/- mice, indicating significantly increased in vivo oxidative stress in sPLA2--> LDLR-/-. These data demonstrate that macrophage-specific overexpression of human sPLA2 increases atherogenesis by directly modulating foam cell formation and in vivo oxidative stress without any effect on systemic sPLA2 activity and lipoprotein metabolism.