Modern approaches for the biological control of vertebrate pests: An Australian perspective

Vertebrate pests cost Australia at least $1 billion annually in lost agricultural production and environmental damage. The spectacular success of myxomatosis in the 1950s and more recently, rabbit hemorrhagic disease, in the biological control of European rabbits has led to ongoing research into similar solutions for other vertebrate pests. There are significant barriers to the successful employment of biological control options including the obvious technological ones, such as host-specificity, as well as the investment required, public concerns and regulatory requirements. The role of biological control in vertebrate pest management and the attempts to develop such strategies in Australia is reviewed with emphasis on species specific case studies for rabbits, cane toads and carp, and the generic approaches of immunocontraception and daughterless genes.     

Targeting Bcl-2-IP3 receptor interaction to reverse Bcl-2's inhibition of apoptotic calcium signals

The antiapoptotic protein Bcl-2 inhibits Ca2+ release from the endoplasmic reticulum (ER). One proposed mechanism involves an interaction of Bcl-2 with the inositol 1,4,5-trisphosphate receptor (IP3R) Ca2+ channel localized with Bcl-2 on the ER. Here we document Bcl-2-IP3R interaction within cells by FRET and identify a Bcl-2 interacting region in the regulatory and coupling domain of the IP3R. A peptide based on this IP3R sequence displaced Bcl-2 from the IP3R and reversed Bcl-2-mediated inhibition of IP3R channel activity in vitro, IP3-induced ER Ca2+ release in permeabilized cells, and cell-permeable IP3 ester-induced Ca2+ elevation in intact cells. This peptide also reversed Bcl-2's inhibition of T cell receptor-induced Ca2+ elevation and apoptosis. Thus, the interaction of Bcl-2 with IP3Rs contributes to the regulation of proapoptotic Ca2+ signals by Bcl-2, suggesting the Bcl-2-IP3R interaction as a potential therapeutic target in diseases associated with Bcl-2's inhibition of cell death.     

Nitrogen fixation in the rhizosphere and rhizoplane of barley

Summary Aerobic and anaerobic N₂-fixing bacteria developed in the rhizosphere of barley seedlings and exhibited N₂ase activity when seedlings were grown in sterilized sand-nutrient cultures containing low levels of combined nitrogen. The source of the N₂-fixing bacteria appeared to be the seed. Average daily rates up to 0.9 μmoles C₂H₄ h⁻¹ g⁻¹ dry root tissue were measured, but the intensity of the activity was affected by moisture levels and concentration of combined N in the rhizosphere. Removal and washing of the roots did not remove the activity, and roots remained active even after surface-sterilization. An unidentified aerobic N₂-fixing bacterium was isolated from the rhizoplane of active barley roots. Inoculation of barley seedlings with the aerobic N₂-fixing bacterium enhanced N₂ase activity of excised roots 10-fold, with average rates of 0.9, 1.1 and 1.3 μmoles h⁻¹ g⁻¹ dry root assayed under pO₂ of 0.01, 0.02 and 0.04 atm respectively. The aerobic N₂-fixing bacterium also exhibited N₂ase activity when inoculated into the rhizosphere of oat, rice and wheat seedlings. Microscopic observations of sterilized live and stained barley roots suggest that the aerobic N₂-fixing bacterium is an endophyte which infects root tissue and metamorphoses into vesicle-like structures.     

A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 control a diverse array of migratory events in adaptive immune function. Most prominently, CCR7 promotes homing of T cells and DCs to T cell areas of lymphoid tissues where T cell priming occurs. However, CCR7 and its ligands also contribute to a multitude of adaptive immune functions including thymocyte development, secondary lymphoid organogenesis, high affinity antibody responses, regulatory and memory T cell function, and lymphocyte egress from tissues. In this survey, we summarise the role of CCR7 in adaptive immunity and describe recent progress in understanding how this axis is regulated. In particular we highlight CCX-CKR, which scavenges both CCR7 ligands, and discuss its emerging significance in the immune system.     

The T cell receptor triggering apparatus is composed of monovalent or monomeric proteins

Understanding the component stoichiometry of the T cell antigen receptor (TCR) triggering apparatus is essential for building realistic models of signal initiation. Recent studies suggesting that the TCR and other signaling-associated proteins are preclustered on resting T cells relied on measurements of the behavior of membrane proteins at interfaces with functionalized glass surfaces. Using fluorescence recovery after photobleaching, we show that, compared with the apical surface, the mobility of TCRs is significantly reduced at Jurkat T cell/glass interfaces, in a signaling-sensitive manner. Using two biophysical approaches that mitigate these effects, bioluminescence resonance energy transfer and two-color coincidence detection microscopy, we show that, within the uncertainty of the methods, the membrane components of the TCR triggering apparatus, i.e. the TCR complex, MHC molecules, CD4/Lck and CD45, are exclusively monovalent or monomeric in human T cell lines, implying that TCR triggering depends only on the kinetics of TCR/pMHC interactions. These analyses also showed that constraining proteins to two dimensions at the cell surface greatly enhances random interactions versus those between the membrane and the cytoplasm. Simulations of TCR-pMHC complex formation based on these findings suggest how unclustered TCR triggering-associated proteins might nevertheless be capable of generating complex signaling outputs via the differential recruitment of cytosolic effectors to the cell membrane.     

Soft Polydimethylsiloxane-Supported Lipid Bilayers for Studying T Cell Interactions

Much of what we know about the early stages of T cell activation has been obtained from studies of T cells interacting with glass-supported lipid bilayers that favor imaging but are orders of magnitude stiffer than typical cells. We developed a method for attaching lipid bilayers to polydimethylsiloxane polymer supports, producing “soft bilayers” with physiological levels of mechanical resistance (Young’s modulus of 4 kPa). Comparisons of T cell behavior on soft and glass-supported bilayers revealed that whereas late stages of T cell activation are thought to be substrate-stiffness dependent, early calcium signaling was unaffected by substrate rigidity, implying that early steps in T cell receptor triggering are not mechanosensitive. The exclusion of large receptor-type phosphatases was observed on the soft bilayers, however, even though it is yet to be demonstrated at authentic cell-cell contacts. This work sets the stage for an imaging-based exploration of receptor signaling under conditions closely mimicking physiological cell-cell contact.     

General practitioner's perceptions of the route to evidence based medicine: a questionnaire survey.

OBJECTIVES: To determine the attitude of general practitioners towards evidence based medicine and their related educational needs. DESIGN: A questionnaire study of general practitioners. SETTING: General practice in the former Wessex region, England. SUBJECTS: Randomly selected sample of 25% of all general practitioners (452), of whom 302 replied. MAIN OUTCOME MEASURES: Respondents'' attitude towards evidence based medicine, ability to access and interpret evidence, perceived barriers to practising evidence based medicine, and best method of moving from opinion based to evidence based medicine. RESULTS: Respondents mainly welcomed evidence based medicine and agreed that its practice improves patient care. They had a low level of awareness of extracting journals, review publications, and databases (only 40% knew of the Cochrane Database of Systematic Reviews), and, even if aware, many did not use them. In their surgeries 20% had access to bibliographic databases and 17% to the world wide web. Most had some understanding of the technical terms used. The major perceived barrier to practising evidence based medicine was lack of personal time. Respondents thought the most appropriate way to move towards evidence based general practice was by using evidence based guidelines or proposals developed by colleagues. CONCLUSION: Promoting and improving access to summaries of evidence, rather than teaching all general practitioners literature searching and critical appraisal, would be the more appropriate method of encouraging evidence based general practice. General practitioners who are skilled in accessing and interpreting evidence should be encouraged to develop local evidence based guidelines and advice.