Effects of water temperature and salinity on elimination of Salmonella charity and Escherichia coli from Sydney rock oysters (Crassostrea commercialis).

The elimination of Salmonella charity and Escherichia coli from the Sydney rock oyster, Crassostrea commercialis, was examined during commercial purification of oysters under different water temperatures and salinities. Both organisms were rapidly eliminated at 18 to 22 degrees C. Purification was effective but slower at 24 to 27 degrees C and incomplete and inconsistent at temperatures below 17 degrees C. The oysters suffered stress and were not effectively purified at water salinities of 15 to 20% but were rapidly purified at 32 to 47% salinity. Winter-harvested and summer-harvested oysters were purified similarly in water at 18 to 22 degrees C and 32 to 36% salinity.     

Development of combined imbibition and hydrothermal threshold models to simulate maize (Zea mays) and chickpea (Cicer arietinum) seed germination in variable environments

* The ability of hydrothermal time (HTT) and virtual osmotic potential (VOP) models to describe the kinetics of maize (Zea mays) and chickpea (Cicer arietinum) seed germination under variable conditions of water potential was investigated with a view to gaining an improved understanding of the impact of on-farm seed priming on seedling establishment through simulation. * Germination and/or imbibition time courses were recorded over a wide range of constant temperatures and water potentials and simple stepwise changes in water potential. * Both models adequately described germination under constant environmental conditions, but not conditions of water potential that varied. To test the hypothesis that this inaccuracy resulted from the use of ambient water potential, a parsimonious model of seed imbibition was developed to calibrate the HTT and VOP models (IHTT and IVOP) and drive them with estimates of seed water potential. * The IHTT and IVOP models described germination during stepwise changes in water potential more accurately than the conventional models, and should contribute to improved predictions of germination time in the field.     

DNA/HSA interaction and nuclease activity of an iron(III) amphiphilic sulfonated corrole

The DNA binding of amphiphilic iron(III) 2,17‐bis(sulfonato)‐5,10,15‐tris(pentafluorophenyl)corrole complex (Fe–SC) was studied using spectroscopic methods and viscosity measurements. Its nuclease‐like activity was examined by using pBR322 DNA as a target. The interaction of Fe–SC with human serum albumin (HSA) in vitro was also examined using multispectroscopic techniques. Experimental results revealed that Fe–SC binds to ct‐DNA via an outside binding mode with a binding constant of 1.25 × 10⁴ M^–1. This iron corrole also displays good activity during oxidative DNA cleavage by hydrogen peroxide or tert‐butyl hydroperoxide oxidants, and high‐valent (oxo)iron(V,VI) corrole intermediates may play an important role in DNA cleavage. Fe–SC exhibits much stronger binding affinity to site II than site I of HSA, indicating a selective binding tendency to HSA site II. The HSA conformational change induced by Fe–SC was confirmed by UV/Vis and CD spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

Pseudomonas aeruginosa toxin ExoU induces a PAF-dependent impairment of alveolar fibrin turnover secondary to enhanced activation of coagulation and increased expression of plasminogen activator inhibitor-1 in the course of mice pneumosepsis

Background

ExoU, a Pseudomonas aeruginosa cytotoxin with phospholipase A₂ activity, was shown to induce vascular hyperpermeability and thrombus formation in a murine model of pneumosepsis. In this study, we investigated the toxin ability to induce alterations in pulmonary fibrinolysis and the contribution of the platelet activating factor (PAF) in the ExoU-induced overexpression of plasminogen activator inhibitor-1 (PAI-1).

Methods

Mice were intratracheally instilled with the ExoU producing PA103 P. aeruginosa or its mutant with deletion of the exoU gene. After 24 h, animal bronchoalveolar lavage fluids (BALF) were analyzed and lung sections were submitted to fibrin and PAI-1 immunohistochemical localization. Supernatants from A549 airway epithelial cells and THP-1 macrophage cultures infected with both bacterial strains were also analyzed at 24 h post-infection.

Results

In PA103-infected mice, but not in control animals or in mice infected with the bacterial mutant, extensive fibrin deposition was detected in lung parenchyma and microvasculature whereas mice BALF exhibited elevated tissue factor-dependent procoagulant activity and PAI-1 concentration. ExoU-triggered PAI-1 overexpression was confirmed by immunohistochemistry. In in vitro assays, PA103-infected A549 cells exhibited overexpression of PAI-1 mRNA. Increased concentration of PAI-1 protein was detected in both A549 and THP-1 culture supernatants. Mice treatment with a PAF antagonist prior to PA103 infection reduced significantly PAI-1 concentrations in mice BALF. Similarly, A549 cell treatment with an antibody against PAF receptor significantly reduced PAI-1 mRNA expression and PAI-1 concentrations in cell supernatants, respectively.

Conclusion

ExoU was shown to induce disturbed fibrin turnover, secondary to enhanced procoagulant and antifibrinolytic activity during P. aeruginosa pneumosepsis, by a PAF-dependent mechanism. Besides its possible pathophysiological relevance, in vitro detection of exoU gene in bacterial clinical isolates warrants investigation as a predictor of outcome of patients with P. aeruginosa pneumonia/sepsis and as a marker to guide treatment strategies.     

Cascading effects of herbivore protective symbionts on hyperparasitoids

1. Microbial symbionts can play an important role in defending their insect hosts against natural enemies. However, researchers have little idea how the presence of such protective symbionts impacts food web interactions and species diversity. 2. This study investigated the effects of a protective symbiont (Hamiltonella defensa) in pea aphids (Acyrthosiphon pisum) on hyperparasitoids, which are a trophic level above the natural enemy target of the symbiont (primary parasitoids). 3. Pea aphids, with and without their natural infections of H. defensa, were exposed first to a primary parasitoid against which the symbiont provides partial protection (either Aphidius ervi or Aphelinus abdominalis), and second to a hyperparasitoid known to attack the primary parasitoid species. 4. It was found that hyperparasitoid hatch rate was substantially affected by the presence of the symbiont. This effect appears to be entirely due to the removal of potential hosts by the action of the symbiont: there was no additional benefit or cost experienced by the hyperparasitoids in response to symbiont presence. The results were similar across the two different aphid–parasitoid–hyperparasitoid interactions we studied. 5. It is concluded that protective symbionts can have an important cascading effect on multiple trophic levels by altering the success of natural enemies, but that there is no evidence for more complex interactions. These findings demonstrate that the potential influence of protective symbionts on the wider community should be considered in future food web studies.     

Differential effects of age,cytomegalovirus-seropositivity and end-stage renal disease (ESRD) on circulating T lymphocyte subsets

The age- and cytomegalovirus (CMV)-seropositivity-related changes in subsets and differentiation of circulating T cells were investigated in end-stage renal disease (ESRD) patients (n = 139) and age-matched healthy individuals. The results show that CMV-seropositivity is associated with expansion of both CD4⁺ and CD8⁺ memory T cells which is already observed in young healthy individuals. In addition, CMV-seropositive healthy individuals have a more differentiated memory T cell profile. Only CMV-seropositive healthy individuals showed an age-dependent decrease in CD4⁺ naïve T cells. The age-related decrease in the number of CD8⁺ naïve T cells was CMV-independent. In contrast, all ESRD patients showed a profound naïve T-cell lymphopenia at every decade. CMV-seropositivity aggravated the contraction of CD4⁺ naïve T cells and increased the number of differentiated CD4⁺ and CD8⁺ memory T cells. In conclusion, CMV-seropositivity markedly alters the homeostasis of circulating T cells in healthy individuals and aggravates the T cell dysregulation observed in ESRD patients.     

Specific localization of scallop gill epithelial calmodulin in cilia

Calmodulin has been isolated and characterized from the gill of the bay scallop aequipecten irradians. Quantitative electrophoretic analysis of epithelial cell fractions show most of the calmodulin to be localized in the cilia, specifically in the detergent- solubilized membrane-matrix fraction. Calmodulin represents 2.2 +/- 0.3 percent of the membrane-matrix protein or 0.41 +/- 0.5 percent of the total ciliary protein. Its concentration is at least 10(-4) M if distributed uniformly within the matrix. Extraction in the presence of calcium suggests that the calmodulin is not bound to the axoneme proper. The ciliary protein is identified as a calmodulin on the basis of its calcium- dependent binding to a fluphenazine-sepharose affinity column and its comigration with bovine brain calmodulin on alkaline-urea and SDS polyacrylamide gels in both the presence and absence of calcium. Scallop ciliary calmodulin activates bovine brain phosphodiesterase to the same extent as bovine brain and chicken gizzard calmodulins. Containing trimethyllysine and lacking cysteine and tryptophan, the amino acid composition of gill calmodulin is typical of known calmodulins, except that it is relatively high in serine and low in methionine. Its composition is less acidic than other calmodulins, in agreement with an observed isoelectric point approximately 0.2 units higher than that of bovine brain. Comparative tryptic peptide mapping of scallop gill ciliary and bovine brain calmodulins indicates coincidence of over 75 percent of the major peptides, but at least two major peptides in each show no near-equivalency. Preliminary results using ATP-reactivated gill cell models show no effect of calcium at micromolar levels on ciliary beat or directionality of the lateral cilia, the cilia which constitute the vast majority of those isolated. However, ciliary arrest will occur at calcium levels more than 150 muM. Because calmodulin usually functions in the micromolar range, its role in this system is unclear. Scallop gill ciliary calmodulin may be involved in the direct regulation of dyneintubule sliding, or it may serve some coupled calcium transport function. At the concentration in which it is found, it must also at least act as a calcium buffer.     

Research in general practice: a survey of incentives and disincentives for research participation

Background Recruitment rates of general practitioners (GPs) to do research vary widely. This may be related to the ability of a study to incorporate incentives for GPs and minimise barriers to participation.Method A convenience sample of 30 GPs, ten each from the Sydney intervention and control groups Ageing in General Practice ‘Detection and Management of Dementia’ project (GP project) and 10 GPs who had refused participation, were recruited to determine incentives and barriers to participating in research. GPs completed the 11-item ‘Meeting the challenges of research in general practice: general practitioner questionnaire’ (GP survey) between months 15 and 24 of the GP project, and received brief qualitative interviews from a research GP to clarify responses where possible.Results The most important incentives the 30 GPs gave for participating in the project were a desire to update knowledge (endorsed by 70%), to help patients (70%), and altruism (60%). Lack of time (43%) was the main barrier. GPs also commented on excessive paperwork and an inadequate explanation of research.Conclusions While a desire to update knowledge and help patients as well as altruism were incentives, time burden was the primary barrier and was likely related to extensive paperwork. Future recruitment may be improved by minimising time burden, making studies simpler with online data entry, offering remuneration and using a GP recruiter.