Application of a novel phytotoxicity assay for the detection of herbicides in Hervey Bay and the Great Sandy Straits

A novel phytotoxicity assay was incorporated into an environmental assessment of Hervey Bay and the Great Sandy Straits, to investigate the role of run-off associated herbicides in the deteriorated health of intertidal seagrass meadows. Dose response curves of common herbicides were performed and their toxicity equivalents elucidated to assist in analysis. The results of the assay were reproducible and corresponded strongly with results of chemical analyses. The incorporation of the assay into the assessment of surface waters added an important aspect to the study by allowing investigation of the toxicity of cumulative herbicide concentrations and yielding biologically relevant data. The highest herbicide concentration detected during the study was equivalent to 0.23 mu g 1(-1) diuron; a concentration known to inhibit photosynthetic efficiency of the assay biomaterial by approximately 3%. (c) 2004 Elsevier Ltd. All rights reserved.

Antibiotic susceptibilities of Pseudomonas aeruginosa isolates derived from patients with cystic fibrosis under aerobic, anaerobic, and biofilm conditions

Recent studies have determined that Pseudomonas aeruginosa can live in a biofilm mode within hypoxic mucus in the airways of patients with cystic fibrosis (CF). P. aeruginosa grown under anaerobic and biofilm conditions may better approximate in vivo growth conditions in the CF airways, and combination antibiotic susceptibility testing of anaerobically and biofilm-grown isolates may be more relevant than traditional susceptibility testing under planktonic aerobic conditions. We tested 16 multidrug-resistant isolates of P. aeruginosa derived from CF patients using multiple combination bactericidal testing to compare the efficacies of double and triple antibiotic combinations against the isolates grown under traditional aerobic planktonic conditions, in planktonic anaerobic conditions, and in biofilm mode. Both anaerobically grown and biofilm-grown bacteria were significantly less susceptible (P < 0.01) to single and combination antibiotics than corresponding aerobic planktonically grown isolates. Furthermore, the antibiotic combinations that were bactericidal under anaerobic conditions were often different from those that were bactericidal against the same organisms grown as biofilms. The most effective combinations under all conditions were colistin (tested at concentrations suitable for nebulization) either alone or in combination with tobramycin (10 mu g ml(-1)), followed by meropenem combined with tobramycin or ciprofloxacin. The findings of this study illustrate that antibiotic sensitivities are dependent on culture conditions and highlight the complexities of choosing appropriate combination therapy for multidrug-resistant P. aeruginosa in the CF lung.

Molecular dynamics study of MscL interactions with a curved lipid bilayer

Mechanosensitivity is a ubiquitous sensory mechanism found in living organisms. The simplest known mechanotransducing mechanism is found in bacteria in the form of the mechanosensitive membrane channel of large conductance, MscL. This channel has been studied extensively using a variety of methods at a functional and structural level. The channel is gated by membrane tension in the lipid bilayer alone. It serves as a safety valve protecting bacterial cells against hypoosmotic shock. MscL of Escherichia coli embedded in bilayers composed of asymmetric amounts of single-tailed and double-tailed lipids has been shown to gate spontaneously, even in the absence of membrane tension. To gain insight into the effect of the lipid membrane composition and geometry on MscL structure, a fully solvated, all-atom model of MscL in a stress-free curved bilayer composed of double- and single-tailed lipids was studied using a 9.5-ns molecular dynamics simulation. The bilayer was modeled as a domed structure accommodating the asymmetric composition of the monolayers. During the course of the simulation a spontaneous restructuring of the periplasmic loops occurred, leading to interactions between one of the loops and phospholipid headgroups. Previous experimental studies of the role of the loops agree with the observation that opening starts with a restructuring of the periplasmic loop, suggesting an effect of the curved bilayer. Because of limited resources, only one simulation of the large system was performed. However, the results obtained suggest that through the geometry and composition of the bilayer the protein structure can be affected even on short timescales.

The role of oxides in the formation of primary iron intermetallics in an Al-11.6Si-0.37Mg Alloy

Recent research suggest that the iron-rich intermetallic phases, such as alpha-FeAl15(Fe,Mn)(3)Si-2 and beta-Fe Al5FeSi, nucleate on oxide films entrained in aluminum casting alloys. This is evidenced by the presence of crack-like defects within these iron-rich intermetallics. In an attempt to verify the role of oxides in nucleating iron-rich intermetallics, experiments have been conducted under conditions where in-situ entrained oxide films and deliberately added oxide particles were present. Iron-rich intermetallics are observed to be associated with the oxides in the final microstructure, and crack-like defects are often observed in the beta-Fe plates. The physical association of the Fe-rich intermetallic phases with these solid oxides, either formed in situ or added, is in accordance with the mechanism suggesting that iron-rich intermetallics nucleate upon the wetted sides of double oxide films.

Spectroscopic analysis of terrestrial analogues for the interpretation of surface composition of rocky bodies in the solar system. Effects of mineral mixing and particle size. Applications to moon, mars and implications for mercury.

Among the Solar System’s bodies, Moon, Mercury and Mars are at present, or have been in the recent years, object of space missions aimed, among other topics, also at improving our knowledge about surface composition. Between the techniques to detect planet’s mineralogical composition, both from remote and close range platforms, visible and near-infrared reflectance (VNIR) spectroscopy is a powerful tool, because crystal field absorption bands are related to particular transitional metals in well-defined crystal structures, e.g., Fe2+ in M1 and M2 sites of olivine or pyroxene (Burns, 1993). Thanks to the improvements in the spectrometers onboard the recent missions, a more detailed interpretation of the planetary surfaces can now be delineated. However, quantitative interpretation of planetary surface mineralogy could not always be a simple task. In fact, several factors such as the mineral chemistry, the presence of different minerals that absorb in a narrow spectral range, the regolith with a variable particle size range, the space weathering, the atmosphere composition etc., act in unpredictable ways on the reflectance spectra on a planetary surface (Serventi et al., 2014). One method for the interpretation of reflectance spectra of unknown materials involves the study of a number of spectra acquired in the laboratory under different conditions, such as different mineral abundances or different particle sizes, in order to derive empirical trends. This is the methodology that has been followed in this PhD thesis: the single factors previously listed have been analyzed, creating, in the laboratory, a set of terrestrial analogues with well-defined composition and size. The aim of this work is to provide new tools and criteria to improve the knowledge of the composition of planetary surfaces. In particular, mixtures composed with different content and chemistry of plagioclase and mafic minerals have been spectroscopically analyzed at different particle sizes and with different mineral relative percentages. The reflectance spectra of each mixture have been analyzed both qualitatively (using the software ORIGIN®) and quantitatively applying the Modified Gaussian Model (MGM, Sunshine et al., 1990) algorithm. In particular, the spectral parameter variations of each absorption band have been evaluated versus the volumetric FeO% content in the PL phase and versus the PL modal abundance. This delineated calibration curves of composition vs. spectral parameters and allow implementation of spectral libraries. Furthermore, the trends derived from terrestrial analogues here analyzed and from analogues in the literature have been applied for the interpretation of hyperspectral images of both plagioclase-rich (Moon) and plagioclase-poor (Mars) bodies.

Study of the effects of climate warming on seed germination and seed longevity of snowbed species

Understanding how climate change will affect the distribution and the phenology of plants is becoming an increasingly important topic in ecological studies. In response to climate warming, there are documented upward shift and alterations of phenology and physiology of several plant species. Despite this, the effects of climate change on plant regeneration from seeds have largely been neglected. However, regeneration from seeds, a key event in the plant life cycle, could be significantly affected by climate warming. In this regard, we investigated how climatic changes will affect the seasonal dynamics of seed germination and seedling survival in two different alpine context. The first part refers to five species inhabiting a snowbed located at the Gavia pass (Parco Naturale dello Stelvio). Here, plants were exposed, in the field, to natural conditions and to artificial warming using Open Top Chambers proposed by the ITEX (International Tundra Experiment). The germination curves of seeds produced were compared in order to highlight differences in seed germination ecology and in seed physiology induced by the climate warming. In the second part, we considered two tree species that form the treeline in Davos (Switzerland). As a surrogate of climate warming we used the natural thermal gradient driven by the altitude and we compared the germination behavior of the species studied in three sites at three different elevations in order to evaluate the likelihood of treeline shift under the predicted climate warming.

Attenuation of depression of muscle protein synthesis induced by lipopolysaccharide, tumor necrosis factor, and angiotensin II by beta-hydroxy-beta-methylbutyrate

beta-Hydroxy-beta-methylbutyrate (HMB; 50 microM) has been shown to attenuate the depression in protein synthesis in murine myotubes in response to lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) with or without interferon-gamma (IFN-gamma), and angiotensin II (ANG II). The mechanism for the depression of protein synthesis by all three agents was the same and was attributed to activation of double-stranded RNA-dependent protein kinase (PKR) with the subsequent phosphorylation of eukaryotic initiation factor 2 (eIF2) on the alpha-subunit as well as increased phosphorylation of the elongation factor (eEF2). Myotubes expressing a catalytically inactive PKR variant, PKRDelta6, showed no depression of protein synthesis in response to either LPS or TNF-alpha, confirming the importance of PKR in this process. There was no effect of any of the agents on phosphorylation of mammalian target of rapamycin (mTOR) or initiation factor 4E-binding protein (4E-BP1), and thus no change in the amount of eIF4E bound to 4E-BP1 or the concentration of the active eIF4E.eIF4G complex. HMB attenuated phosphorylation of eEF2, possibly by increasing phosphorylation of mTOR, and also attenuated phosphorylation of eIF2alpha by preventing activation of PKR. These results suggest that HMB may be effective in attenuating muscle atrophy in a range of catabolic conditions.

Mechanism of attenuation of muscle protein degradation induced by tumor necrosis factor-alpha and angiotensin II by beta-hydroxy-beta-methylbutyrate

Both tumor necrosis factor-alpha (TNF-alpha)/interferon-gamma (IFN-gamma) and angiotensin II (ANG II) induced an increase in total protein degradation in murine myotubes, which was completely attenuated by treatment with beta-hydroxy-beta-methylbutyrate (HMB; 50 microM). There was an increase in formation of reactive oxygen species (ROS) within 30 min, as well as an increase in the activity of both caspase-3 and -8, and both effects were attenuated by HMB. Moreover, inhibitors of caspase-3 and -8 completely attenuated both ROS formation and total protein degradation induced by TNF-alpha/IFN-gamma and ANG II. There was an increased autophosphorylation of double-stranded RNA-dependent protein kinase (PKR), which was attenuated by the specific caspase-3 and -8 inhibitors. Neither ROS formation or protein degradation occurred in myotubes expressing a catalytically inactive PKR variant, PKRDelta6, in response to TNF-alpha/IFN-gamma, compared with myotubes expressing wild-type PKR, although there was still activation of caspase-3 and -8. HMB also attenuated activation of PKR, suggesting that it was important in protein degradation. Formation of ROS was attenuated by rotenone, an inhibitor of the mitochondrial electron transport chain, nitro-l-arginine methyl ester, an inhibitor of nitric oxide synthase, and SB 203580, a specific inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), which also attenuated total protein degradation. Activation of p38 MAPK by PKR provides the link to ROS formation. These results suggest that TNF-alpha/IFN-gamma and ANG II induce muscle protein degradation by a common signaling pathway, which is attenuated by HMB, and that this involves the initial activation of caspase-3 and -8, followed by autophosphorylation and activation of PKR, which then leads to increased ROS formation via activation of p38 MAPK. Increased ROS formation is known to induce protein degradation through the ubiquitin-proteasome pathway.

Attenuation of skeletal muscle atrophy in cancer cachexia by d-myo-inositol 1,2,6-triphosphate

PURPOSE: To determine the effectiveness of the polyanionic, metal binding agent D-myo-inositol-1,2,6-triphosphate (alpha trinositol, AT), and its hexanoyl ester (HAT), in tissue wasting in cancer cachexia. METHODS: The anti-cachexic effect was evaluated in the MAC16 tumour model. RESULTS: Both AT and HAT attenuated the loss of body weight through an increase in the nonfat carcass mass due to an increase in protein synthesis and a decrease in protein degradation in skeletal muscle. The decrease in protein degradation was associated with a decrease in activity of the ubiquitin-proteasome proteolytic pathway and caspase-3 and -8. Protein synthesis was increased due to attenuation of the elevated autophosphorylation of double-stranded RNA-dependent protein kinase, and of eukaryotic initiation factor 2alpha together with hyperphosphorylation of eIF4E-binding protein 1 and decreased phosphorylation of eukaryotic elongation factor 2. In vitro, AT completely attenuated the protein degradation in murine myotubes induced by both proteolysis-inducing factor and angiotensin II. CONCLUSION: These results show that AT is a novel therapeutic agent with the potential to alleviate muscle wasting in cancer patients.

Experimental and theoretical characterisation of tunable fibre gratings

This thesis presents details on both theoretical and experimental aspects of UV written fibre gratings. The main body of the thesis deals with the design, fabrication and testing of telecommunication optical fibre grating devices, but also an accurate theoretical analysis of intra-core fibre gratings is presented. Since more than a decade, fibre gratings have been extensively used in the telecommunication field (as filters, dispersion compensators, and add/drop multiplexers for instance). Gratings for telecommunication should conform to very high fabrication standards as the presence of any imperfection raises the noise level in the transmission system compromising its ability of transmitting intelligible sequence of bits to the receiver. Strong side lobes suppression and high and sharp reflection profile are then necessary characteristics. A fundamental part of the theoretical and experimental work reported in this thesis is about apodisation. The physical principle of apodisation is introduced and a number of apodisation techniques, experimental results and numerical optimisation of the shading functions and all the practical parameters involved in the fabrication are detailed. The measurement of chromatic dispersion in fibres and FBGs is detailed and an estimation of its accuracy is given. An overview on the possible methods that can be implemented for the fabrication of tunable fibre gratings is given before detailing a new dispersion compensator device based on the action of a distributed strain onto a linearly chirped FBG. It is shown that tuning of second and third order dispersion of the grating can be obtained by the use of a specially designed multipoint bending rig. Experiments on the recompression of optical pulses travelling long distances are detailed for 10 Gb/s and 40 Gb/s. The characterisation of a new kind of double section LPG fabricated on a metal-clad coated fibre is reported. The fabrication of the device is made easier by directly writing the grating through the metal coating. This device may be used to overcome the recoating problems associated with standard LPGs written in step-index fibre. Also, it can be used as a sensor for simultaneous measurements of temperature and surrounding medium refractive index.

The Cys4 zinc finger of bacteriophage T7 primase in sequence-specific single-stranded DNA recognition

Bacteriophage T7 DNA primase recognizes 5'-GTC-3' in single-stranded DNA. The primase contains a single Cys4 zinc-binding motif that is essential for recognition. Biochemical and mutagenic analyses suggest that the Cys4 motif contacts cytosine of 5'-GTC-3' and may also contribute to thymine recognition. Residues His33 and Asp31 are critical for these interactions. Biochemical analysis also reveals that T7 primase selectively binds CTP in the absence of DNA. We propose that bound CTP selects the remaining base G, of 5'-GTC-3', by base pairing. Our deduced mechanism for recognition of ssDNA by Cys4 motifs bears little resemblance to the recognition of trinucleotides of double-stranded DNA by Cys2His2 zinc fingers.

Accuracy of cornea and lens biometry using anterior segment optical coherence tomography

We assess the accuracy of the Visante anterior segment optical coherence tomographer (AS-OCT) and present improved formulas for measurement of surface curvature and axial separation. Measurements are made in physical model eyes. Accuracy is compared for measurements of corneal thickness (d1) and anterior chamber depth (d2) using-built-in AS-OCT software versus the improved scheme. The improved scheme enables measurements of lens thickness (d 3) and surface curvature, in the form of conic sections specified by vertex radii and conic constants. These parameters are converted to surface coordinates for error analysis. The built-in AS-OCT software typically overestimates (mean±standard deviation(SD)]d1 by +62±4 μm and d2 by +4±88μm. The improved scheme reduces d1 (-0.4±4 μm) and d2 (0±49 μm) errors while also reducing d3 errors from +218±90 (uncorrected) to +14±123 μm (corrected). Surface x coordinate errors gradually increase toward the periphery. Considering the central 6-mm zone of each surface, the x coordinate errors for anterior and posterior corneal surfaces reached +3±10 and 0±23 μm, respectively, with the improved scheme. Those of the anterior and posterior lens surfaces reached +2±22 and +11±71 μm, respectively. Our improved scheme reduced AS-OCT errors and could, therefore, enhance pre- and postoperative assessments of keratorefractive or cataract surgery, including measurement of accommodating intraocular lenses. © 2007 Society of Photo-Optical Instrumentation Engineers.

Factors determining the growth curve of the foliose lichen Parmelia conspersa

Growth curves of the foliose lichen Parmelia conspersa (Ehrh. Ex Ach.)Ach. Were obtained by plotting radial growth (RGR, mm yr-1) of the fastest measured lobe, the slowest measured lobe, a randomly selected lobe, and by averaging a sample of lobes from each thallus against thallus diameter. Growth curves derived from the fastest-growing lobe and by averaging lobes were asymptotic and could be fitted by the growth model of Aplin and Hill. Mean lobe width increased with thallus size, reaching a maximum at approx. 4.5 cm thallus diameter. In four out of six thalli, radial growth of lobes over four months was positively correlated with initial lobe width or area. The RGR of isolated lobes was unaffected until the base of the lobe was removed to within 1-2 mm of the tip. The concentration (micrograms mg-1 biomass) of ribitol, arabitol and mannitol was greater in the marginal lobes of large than in small thalli. The results suggested that the growth curve of P. conspersa is determined by processes that occur within individual marginal lobes and can be explained by the Aplin and Hill model. Changes in lobe width and in the productive capacity of individual lobes with thallus size are likely to be more important factors than the degree of translocation within the lobe in determining the growth curve.

Long period grating directional bend sensor based on asymmetric index modification of cladding

A long period grating (LPG) written in a standard optical fibre was modified by using a femtosecond laser to induce an asymmetric change in the cladding's refractive index. This device produced blue and red wavelength shifts depending on the orientation of applied curvature, with maximum sensitivities of -1.6 nm m and +3.8 nm m, suggesting that this type of LPG may be useful as a shape sensor.

Is it all tough talking at the top? A post-structuralist analysis of the construction of gendered speaker identities of British business leaders within interview narratives

This paper uses a feminist post-structuralist approach to examine the gendered identities of a sample of British business leaders in Britain. While recent national surveys offer many material reasons why women are acutely under-represented as business leaders, the role of language is rarely addressed. This paper explores the ways in which ten senior women and men construct their sense of leadership identities through the medium of interview narratives. Drawing upon two poststructuralist models of analysis (Derrida’s 1987 theory of deconstruction and Bakhtin’s 1927/1981 concept of double-voiced discourse), the paper shows how both females and males are able to shift pragmatically between interwoven corporate discourses, which demand competing cultural allegiances from one moment to the next, allegiances constantly tested by the rapid change and uncertainty that characterise global business. While male leaders experience a relative freedom of movement between different cultural discourses, female leaders are circumscribed by negative and reductive representations of female speech and behaviour. In sum, senior women are required constantly to observe, review, police and repair their use of leadership language, which potentially undermines their confidence and authority as leaders.