Expression and production of the CXC chemokine growth-related oncogene-alpha by human eosinophils

Eosinophils are seen together with neutrophils at sites of inflammation. However, their roles are not clear. In addition, eosinophils infiltrate tumor tissue in some neoplastic diseases. In this study, we show that large amounts of the neutrophil-activating CXC chemokine growth-related oncogene (GRO)-alpha can be produced by human eosinophils. Eosinophils showed presence of preformed GRO-alpha in the crystalloid-containing specific granules (190 pg/2 x 10(6) cells). During incubation, a strong increase in GRO-alpha gene expression was seen. At a low cell density, addition of TNF-alpha or IL-1 beta increased the production of GRO-alpha in eosinophils, which was not the case at a higher cell density. Eosinophils can produce TNF-alpha themselves, and neutralizing Abs against TNF-alpha significantly inhibited GRO-alpha production. This suggests that autocrine and paracrine effects from TNF-alpha can be important when up-regulating GRO-alpha gene expression. In contrast, IFN-gamma, a prototypic Th1-cytokine, down-regulated expression of GRO-alpha. This may be important during resolution of inflammation but also suggests different roles for eosinophils depending on the inflammatory context. Tumor-infiltrating eosinophils in Hodgkin's disease of the nodular sclerosing type are associated with a poor prognosis. Eosinophils from such tumor tissue showed an abundant expression of GRO-alpha. The GRO-alpha receptor CXCR2 was also detected in tumor tissue, proposing interactions between eosinophils and the tumor. Our findings suggest that eosinophils can promote inflammation through recruitment of CXCR2-bearing cells. In addition, this feature of the eosinophils indicates a role for these cells in the biology of certain tumors.     

Structure of Rhodococcus erythropolis limonene-1,2-epoxide hydrolase reveals a novel active site

Epoxide hydrolases are essential for the processing of epoxide-containing compounds in detoxification or metabolism. The classic epoxide hydrolases have an alpha/beta hydrolase fold and act via a two-step reaction mechanism including an enzyme-substrate intermediate. We report here the structure of the limonene-1,2-epoxide hydrolase from Rhodococcus erythropolis, solved using single-wavelength anomalous dispersion from a selenomethionine-substituted protein and refined at 1.2 A resolution. This enzyme represents a completely different structure and a novel one-step mechanism. The fold features a highly curved six-stranded mixed beta-sheet, with four alpha-helices packed onto it to create a deep pocket. Although most residues lining this pocket are hydrophobic, a cluster of polar groups, including an Asp-Arg-Asp triad, interact at its deepest point. Site-directed mutagenesis supports the conclusion that this is the active site. Further, a 1.7 A resolution structure shows the inhibitor valpromide bound at this position, with its polar atoms interacting directly with the residues of the triad. We suggest that several bacterial proteins of currently unknown function will share this structure and, in some cases, catalytic properties.     

Cost-effective engineering of a small-scale bioreactor

Several methods exist for increasing the scale of cell culture in the laboratory. While these methods provide significant increases in biomass, they are often prohibitively expensive for many laboratories. We have engineered a small-scale bioreactor with a novel means of introducing oxygen through the catalytic breakdown of hydrogen peroxide using a manganese oxide catalyst. We have also adapted and modified an existing assay for dissolved oxygen to be compatible with culture conditions. In this system we have been able to culture CHO cells at densities of up to 10(7) cells/mL without the use of automated feedback systems.     

Bovine P2 Myelin Basic Protein Crystallizes in Three Different Forms

P2 protein is a minor component of the myelin membrane. We have crystallized this protein for high-resolution crystallographic study. Three crystal morphologies are available. Two of them are from ammonium sulfate, and one is from polyethyleneglycol (PEG). The unit cell of the most suitable crystals from PEG 4000 has the dimensions a = 91.3 A, b = 99.8 A, c = 56.0 A; is of space group P2(1)2(1)2(1); and contains up to four molecules per asymmetric unit. The limit of resolution is 2.7 A.     

Comparing tropical forest tree size distributions with the predictions of metabolic ecology and equilibrium models

Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the −2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality.     

Differences in Phyllotreta cruciferae and Phyllotreta striolata (Coleoptera: Chrysomelidae) responses to neonicotinoid seed treatments

Insecticidal seed treatments are used commonly throughout the Northern Great Plains of North America to systemically protect seedlings of canola (Brassica napus L. and Brassica rapa L.) from attack by the flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae). Here, we investigated differential responses by the two flea beetle species to the neonicotinoid seed treatments thiamethoxam (Helix and Helix XTra) and clothianidin (Prosper 400) in greenhouse experiments. P. cruciferae experienced higher mortality and fed less when exposed to these compounds than did P. striolata. Beetles of the overwintered and the summer generations responded differently when feeding on seedlings that developed with insecticidal seed treatments, with mortality higher for P. cruciferae in May than in August. When the two flea beetle species were held together at equal densities and allowed to feed on seedlings affected by the seed treatments, mortality of P. cruciferae significantly exceeded that of P. striolata. Differences in efficacies of these compounds for these beetles have ramifications for management strategies in regions where these insects occur sympatrically. Competitive release of P. striolata was previously reported to occur when P. cruciferae was excluded from brassicaceous crops; consequently, the consistent use of these seed treatments over millions of hectares of canola cropland may be a factor that contributes to a shift in prevalence of flea beetle pest species from P. cruciferae toward P. striolata.     

Oncogenic translation directs spliceosome dynamics revealing an integral role for SF3A3 in breast cancer

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