Showing papers by "Cooperative Research Centre published in 2005"

Engineered antibody fragments and the rise of single domains

Abstract: With 18 monoclonal antibody (mAb) products currently on the market and more than 100 in clinical trials, it is clear that engineered antibodies have come of age as biopharmaceuticals. In fact, by 2008, engineered antibodies are predicted to account for >30% of all revenues in the biotechnology market. Smaller recombinant antibody fragments (for example, classic monovalent antibody fragments (Fab, scFv)) and engineered variants (diabodies, triabodies, minibodies and single-domain antibodies) are now emerging as credible alternatives. These fragments retain the targeting specificity of whole mAbs but can be produced more economically and possess other unique and superior properties for a range of diagnostic and therapeutic applications. Antibody fragments have been forged into multivalent and multispecific reagents, linked to therapeutic payloads (such as radionuclides, toxins, enzymes, liposomes and viruses) and engineered for enhanced therapeutic efficacy. Recently, single antibody domains have been engineered and selected as targeting reagents against hitherto immunosilent cavities in enzymes, receptors and infectious agents. Single-domain antibodies are anticipated to significantly expand the repertoire of antibody-based reagents against the vast range of novel biomarkers being discovered through proteomics. As this review aims to show, there is tremendous potential for all antibody fragments either as robust diagnostic reagents (for example in biosensors), or as nonimmunogenic in vivo biopharmaceuticals with superior biodistribution and blood clearance properties.

Repressor- and activator-type ethylene response factors functioning in jasmonate signaling and disease resistance identified via a genome-wide screen of Arabidopsis transcription factor gene expression.

Abstract: To identify transcription factors (TFs) involved in jasmonate (JA) signaling and plant defense, we screened 1,534 Arabidopsis (Arabidopsis thaliana) TFs by real-time quantitative reverse transcription-PCR for their altered transcript at 6 h following either methyl JA treatment or inoculation with the incompatible pathogen Alternaria brassicicola. We identified 134 TFs that showed a significant change in expression, including many APETALA2/ethylene response factor (AP2/ERF), MYB, WRKY, and NAC TF genes with unknown functions. Twenty TF genes were induced by both the pathogen and methyl JA and these included 10 members of the AP2/ERF TF family, primarily from the B1a and B3 subclusters. Functional analysis of the B1a TF AtERF4 revealed that AtERF4 acts as a novel negative regulator of JA-responsive defense gene expression and resistance to the necrotrophic fungal pathogen Fusarium oxysporum and antagonizes JA inhibition of root elongation. In contrast, functional analysis of the B3 TF AtERF2 showed that AtERF2 is a positive regulator of JA-responsive defense genes and resistance to F. oxysporum and enhances JA inhibition of root elongation. Our results suggest that plants coordinately express multiple repressor- and activator-type AP2/ERFs during pathogen challenge to modulate defense gene expression and disease resistance.

Establishing representative no-take areas in the Great Barrier Reef: large-scale implementation of theory on marine protected areas

Abstract: The Great Barrier Reef Marine Park, an area almost the size of Japan, has a new network of no-take areas that significantly improves the protection of biodiversity. The new marine park zoning implements, in a quantitative manner, many of the theoretical design principles discussed in the literature. For example, the new network of no-take areas has at least 20% protection per “bioregion,” minimum levels of protection for all known habitats and special or unique features, and minimum sizes for no-take areas of at least 10 or 20 km across at the smallest diameter. Overall, more than 33% of the Great Barrier Reef Marine Park is now in no-take areas (previously 4.5%). The steps taken leading to this outcome were to clarify to the interested public why the existing level of protection was inadequate; detail the conservation objectives of establishing new no-take areas; work with relevant and independent experts to define, and contribute to, the best scientific process to deliver on the objectives; describe the biodiversity (e.g., map bioregions); define operational principles needed to achieve the objectives; invite community input on all of the above; gather and layer the data gathered in round-table discussions; report the degree of achievement of principles for various options of no-take areas; and determine how to address negative impacts. Some of the key success factors in this case have global relevance and include focusing initial communication on the problem to be addressed; applying the precautionary principle; using independent experts; facilitating input to decision making; conducting extensive and participatory consultation; having an existing marine park that encompassed much of the ecosystem; having legislative power under federal law; developing high-level support; ensuring agency priority and ownership; and being able to address the issue of displaced fishers.

Polar ocean ecosystems in a changing world

Abstract: Polar organisms have adapted their seasonal cycles to the dynamic interface between ice and water. This interface ranges from the micrometre-sized brine channels within sea ice to the planetary-scale advance and retreat of sea ice. Polar marine ecosystems are particularly sensitive to climate change because small temperature differences can have large effects on the extent and thickness of sea ice. Little is known about the interactions between large, long-lived organisms and their planktonic food supply. Disentangling the effects of human exploitation of upper trophic levels from basin-wide, decade-scale climate cycles to identify long-term, global trends is a daunting challenge facing polar bio-oceanography.

Understanding variability in winegrape production systems 2. Within vineyard variation in quality over several vintages

Abstract: Spatial variability in various indices of wine grape quality was studied over several vintages in blocks planted to Cabernet Sauvignon and Ruby Cabernet in the Coonawarra (1999-2002) and Sunraysia (2000-2002) regions of Australia. At both sites, intra-annual variation was marked whilst intra-annual variation was much greater for some indices (e.g. concentration of total phenolics) than others (e.g. Baume). The magnitude of intra-annual variation was readily identified in terms of the 'spread', defined as the difference between the maximum and minimum values, expressed as a % of the median value. Typical values of the spread were 20% for Baume, but could be as high as 117% for phenolics, and better indicated the extent of variation facing the winemaker than the coefficient of variation (CV; typically 3% for Baume and l4% for phenolics). For all attributes, variation in any given year showed marked spatial structure, with the patterns of variation being broadly consistent for each attribute in each year of the study, and with many attributes following similar patterns. The results therefore strongly support the idea of zonal vineyard management. However, fruit quality zone identification is dependent on a large sampling effort. Therefore, given the current availability of yield monitors, the finding that between-zone differences in quality indices were generally significant (P < 0.05) for zones identified on the basis ob yield alone, and, in the absence ob an on-the-go sensing capability, it is suggested that zonal management should proceed on the basis of zones ob characteristic yield productivity. Based on the present work, it is suggested that development ob an on-the-go fruit quality sensing technology would enable the wine industry co maximise its opportunity to gain benefit from differential vineyard management such as selective harvesting. Indeed, the results ob this work suggest that in the absence ob zonal management, preferably supported by on-the-go quality sensing, winemaker demands for delivery of uniform parcels of fruit are unlikely to be satisfied.

Current wrought magnesium alloys: Strengths and weaknesses

Abstract: The opportunities for extruded and sheet magnesium products in the automotive industry, in particular, are increasing as the quest for lightweighting gains momentum. However, the current alloys all have limitations and these are accentuated when higher productivity targets are also imposed. This article attempts to summarize the strengths and weaknesses of the current wrought alloys, with particular emphasis on the extrusion process, and also considers alternative processing routes which may be useful in overcoming some of these shortcomings.

Cold-induced repression of the rice anther-specific cell wall invertase gene OSINV4 is correlated with sucrose accumulation and pollen sterility

Abstract: Low temperatures during rice (Oryza sativa L.) pollen development cause pollen sterility and decreased grain yield. We show that the time of highest sensitivity to cold coincides with the time of peak tapetal activity: the transition of the tetrad to early uni-nucleate stage (young microspore, YM stage). Low temperatures at this stage of pollen development result in an accumulation of sucrose in the anthers, accompanied by decreased activity of cell wall bound acid invertase and depletion of starch in mature pollen grains. Expression analysis of two cell wall (OSINV1, 4) and one vacuolar (OSINV2) acid invertase genes showed that OSINV4 is anther-specific and down-regulated by cold treatment. OSINV4 is transiently expressed in the tapetum cell layer at the YM stage, and later from the early binucleate stage in the maturing microspores. The down-regulation of OSINV4 expression in the tapetum at YM may cause a disruption in hexose production and starch formation in the pollen grains. In a cold-tolerant cultivar, OSINV4 expression was not reduced by cold; sucrose did not accumulate in the anthers and starch formation in the pollen grains was not affected.

Effects of rainfall seasonality and soil moisture capacity on mean annual water balance for Australian catchments

Abstract: [1] An important factor controlling catchment-scale water balance is the seasonal variation of climate. The aim of this study is to investigate the effect of the seasonal distributions of water and energy, and their interactions with the soil moisture store, on mean annual water balance in Australia at catchment scales using a stochastic model of soil moisture balance with seasonally varying forcing. The rainfall regime at 262 catchments around Australia was modeled as a Poisson process with the mean storm arrival rate and the mean storm depth varying throughout the year as cosine curves with annual periods. The soil moisture dynamics were represented by use of a single, finite water store having infinite infiltration capacity, and the potential evapotranspiration rate was modeled as an annual cosine curve. The mean annual water budget was calculated numerically using a Monte Carlo simulation. The model predicted that for a given level of climatic aridity the ratio of mean annual evapotranspiration to rainfall was larger where the potential evapotranspiration and rainfall were in phase, that is, in summer-dominant rainfall catchments, than where they were out of phase. The observed mean annual evapotranspiration ratios have opposite results. As a result, estimates of mean annual evapotranspiration from the model compared poorly with observational data. Because the inclusion of seasonally varying forcing alone was not sufficient to explain variability in the mean annual water balance, other catchment properties may play a role. Further analysis showed that the water balance was highly sensitive to the catchment-scale soil moisture capacity. Calibrations of this parameter indicated that infiltration-excess runoff might be an important process, especially for the summer-dominant rainfall catchments; most similar studies have shown that modeling of infiltration-excess runoff is not required at the mean annual timescale.

Animal visual systems and the evolution of color patterns: sensory processing illuminates signal evolution

Abstract: Animal color pattern phenotypes evolve rapidly. What influences their evolution? Because color patterns are used in communication, selection for signal efficacy, relative to the intended receiver's visual system, may explain and predict the direction of evolution. We investigated this in bowerbirds, whose color patterns consist of plumage, bower structure, and ornaments and whose visual displays are presented under predictable visual conditions. We used data on avian vision, environmental conditions, color pattern properties, and an estimate of the bowerbird phylogeny to test hypotheses about evolutionary effects of visual processing. Different components of the color pattern evolve differently. Plumage sexual dimorphism increased and then decreased, while overall (plumage plus bower) visual contrast increased. The use of bowers allows relative crypsis of the bird but increased efficacy of the signal as a whole. Ornaments do not elaborate existing plumage features but instead are innovations (new color schemes) that increase signal efficacy. Isolation between species could be facilitated by plumage but not ornaments, because we observed character displacement only in plumage. Bowerbird color pattern evolution is at least partially predictable from the function of the visual system and from knowledge of different functions of different components of the color patterns. This provides clues to how more constrained visual signaling systems may evolve.

Significant decadal-scale impact of volcanic eruptions on sea level and ocean heat content

Abstract: Ocean thermal expansion contributes significantly to sea-level variability and rise. However, observed decadal variability in ocean heat content and sea level has not been reproduced well in climate models. Aerosols injected into the stratosphere during volcanic eruptions scatter incoming solar radiation, and cause a rapid cooling of the atmosphere and a reduction in rainfall, as well as other changes in the climate system. Here we use observations of ocean heat content and a set of climate simulations to show that large volcanic eruptions result in rapid reductions in ocean heat content and global mean sea level. For the Mt Pinatubo eruption, we estimate a reduction in ocean heat content of about 3 x 10(22) J and a global sea-level fall of about 5 mm. Over the three years following such an eruption, we estimate a decrease in evaporation of up to 0.1 mm d(-1), comparable to observed changes in mean land precipitation. The recovery of sea level following the Mt Pinatubo eruption in 1991 explains about half of the difference between the long-term rate of sea-level rise of 1.8 mm yr(-1) (for 1950-2000), and the higher rate estimated for the more recent period where satellite altimeter data are available (1993-2000).

The generic enhancement of photochromic dye switching speeds in a rigid polymer matrix

Abstract: The switching or isomerization speed of photochromic dyes in a rigid polymeric matrix (such as an ophthalmic lens) is generally significantly slower than that observed in the mobile environment of a solution. Here we describe that the attachment of flexible oligomers having a low glass-transition temperature-such as poly(dimethylsiloxane)-to photochromic dyes greatly increases their switching speeds in a rigid polymer matrix. The greatest impact was observed in the thermal fade parameters T(1/2) and T(3/4)-the times it takes for the optical density to reduce by half and three quarters of the initial optical density of the coloured state-which were reduced by 40-95% and 60-99% respectively for spirooxazines, chromenes and an azo dye in a host polymer with a glass-transition temperature of 120 degrees C. The method does not alter the electronic nature of the dyes but simply protects them from the host matrix and provides greater molecular mobility for the switching process. In addition to ophthalmic lenses, the generic nature of the method may find further utility in data recording or optical switching.

Stable isotope dilution analysis of wine fermentation products by HS-SPME-GC-MS.

Abstract: The aim of this study was to quantify, in a single analysis, 31 volatile fermentation-derived products that contribute to the aroma of red and white wine. We developed a multi-component method based on headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS). The 31 volatile compounds analysed include ethyl esters, acetates, acids and alcohols. Although these compounds have a range of functional groups, chemical properties, volatilities, affinities for the SPME fibre, and are found in wine at various concentrations, the accuracy of the analysis was achieved with the use of polydeuterated internal standards for stable isotope dilution analyses (SIDA). Nine of the labelled standards were commercially available, while 22 were synthesised. The method was validated by a series of duplicate spiked standard additions to model, white and red wine matrices over the concentration range relevant for each compound in wine. This demonstrated that the appropriate use of SIDA helped to account for matrix effects, for instance potential sources of variation such as the relative response to the MS detector, ionic strength, ethanol content and pH of different wine matrices. The resultant calibration functions had correlation coefficients (R2) ranging from 0.995 to 1.000. Each compound could be quantified at levels below its aroma threshold in wine. Relative standard deviations were all <5%. The method was optimised for the best compromise (over the 31 compounds) of wine dilution factor, level of sodium chloride addition, SPME fibre, SPME temperature, SPME time, GC column and MS conditions. Confirmation of identity was achieved by retention time and peak shape, and measurement of at least three ions for each analyte and internal standard with the MS operating in selected ion monitoring mode to facilitate more precise quantitation with a high sampling rate. The method is a valuable research tool with many relevant applications. A novel method for the combined chiral separation and SIDA quantification of 2- and 3-methylbutanoic acid is also demonstrated.

CD8α+ Dendritic Cells Selectively Present MHC Class I-Restricted Noncytolytic Viral and Intracellular Bacterial Antigens In Vivo

Abstract: CD8α+ dendritic cells (DCs) have been shown to be the principal DC subset involved in priming MHC class I-restricted CTL immunity to a variety of cytolytic viruses, including HSV type 1, influenza, and vaccinia virus. Whether priming of CTLs by CD8α+ DCs is limited to cytolytic viruses, which may provide dead cellular material for this DC subset, or whether these DCs selectively present intracellular Ags, is unknown. To address this question, we examined Ag presentation to a noncytolytic virus, lymphocytic choriomeningitis virus, and to an intracellular bacterium, Listeria monocytogenes. We show that regardless of the type of intracellular infection, CD8α+ DCs are the principal DC subset that initiate CD8+ T cell immunity.

Effect of population size on the estimation of QTL: a test using resistance to barley stripe rust.

Abstract: The limited population sizes used in many quantitative trait locus (QTL) detection experiments can lead to underestimation of QTL number, overestimation of QTL effects, and failure to quantify QTL interactions. We used the barley/barley stripe rust pathosystem to evaluate the effect of population size on the estimation of QTL parameters. We generated a large (n=409) population of doubled haploid lines derived from the cross of two inbred lines, BCD47 and Baronesse. This population was evaluated for barley stripe rust severity in the Toluca Valley, Mexico, and in Washington State, USA, under field conditions. BCD47 was the principal donor of resistance QTL alleles, but the susceptible parent also contributed some resistance alleles. The major QTL, located on the long arm of chromosome 4H, close to the Mlo gene, accounted for up to 34% of the phenotypic variance. Subpopulations of different sizes were generated using three methods—resampling, selective genotyping, and selective phenotyping—to evaluate the effect of population size on the estimation of QTL parameters. In all cases, the number of QTL detected increased with population size. QTL with large effects were detected even in small populations, but QTL with small effects were detected only by increasing population size. Selective genotyping and/or selective phenotyping approaches could be effective strategies for reducing the costs associated with conducting QTL analysis in large populations. The method of choice will depend on the relative costs of genotyping versus phenotyping.

Cereal phosphate transporters associated with the mycorrhizal pathway of phosphate uptake into roots.

Abstract: A very large number of plant species are capable of forming symbiotic associations with arbuscular mycorrhizal (AM) fungi. The roots of these plants are potentially capable of absorbing P from the soil solution both directly through root epidermis and root hairs, and via the AM fungal pathway that delivers P to the root cortex. A large number of phosphate (P) transporters have been identified in plants; tissue expression patterns and kinetic information supports the roles of some of these in the direct root uptake pathways. Recent work has identified additional P transporters in several unrelated species that are strongly induced, sometimes specifically, in AM roots. The primary aim of the work described in this paper was to determine how mycorrhizal colonisation by different species of AM fungi influenced the expression of members of the Pht1 gene families in the cereals Hordeum vulgare (barley), Triticum aestivum (wheat) and Zea mays (maize). RT-PCR and in-situ hybridisation, showed that the transporters HORvu;Pht1;8 (AY187023), TRIae;Pht1;myc (AJ830009) and ZEAma;Pht1;6 (AJ830010), had increased expression in roots colonised by the AM fungi Glomus intraradices,Glomus sp. WFVAM23 and Scutellospora calospora. These findings add to the increasing body of evidence indicating that plants that form AM associations with members of the Glomeromycota have evolved phosphate transporters that are either specifically or preferentially involved in scavenging phosphate from the apoplast between intracellular AM structures and root cortical cells. Operation of mycorrhiza-inducible P transporters in the AM P uptake pathway appears, at least partially, to replace uptake via different P transporters located in root epidermis and root hairs.

Cylindrospermopsin genotoxicity and cytotoxicity: role of cytochrome P-450 and oxidative stress.

Abstract: Cylindrospermopsin (CYN) is a cyanobacterial toxin found in drinking-water sources world wide. It was the likely cause of human poisonings in Australia and possibly Brazil. Although CYN itself is a potent protein synthesis inhibitor, its acute toxicity appears to be mediated by cytochrome p-450 (CYP450)-generated metabolites. CYN also induces genotoxic effects both in vitro and in vivo, and preliminary evidence suggests that tumors are generated by oral exposure to CYN. To understand the role of CYP450-activated CYN metabolites on in vitro genotoxicity, this study quantified the process in primary mouse hepatocytes using the COMET assay in both the presence and absence of CYP450 inhibitors known to block acute CYN cytotoxicity. CYN was cytotoxic at concentrations above 0.1 μM(EC50 = 0.5 μM) but produced significant increases in Comet tail length, area, and tail moment at 0.05 μM and above; hence genotoxicity is unlikely to be secondary to metabolic disruption due to toxicity. The CYP450 inhibitors omepraz...

Arabinogalactan proteins are required for apical cell extension in the moss Physcomitrella patens.

Abstract: Cell biological, structural, and genetic approaches have demonstrated the presence of arabinogalactan proteins (AGPs) in the moss Physcomitrella patens and provided evidence for their function in cell expansion and specifically in the extension of apical tip-growing cells. Inhibitor studies indicated that apical cell expansion in P. patens is blocked by synthetic AGP binding β-glucosyl Yariv reagent (βGlcYR). The anti-(1→5)-α-l-arabinan monoclonal antibody LM6 binds to some AGPs in P. patens , to all plasma membranes, and to the cell wall surface at the most apical region of growing protonemal filaments. Moreover, LM6 labeling of cell walls at the tips of apical cells of P. patens was abolished in the presence of βGlcYR, suggesting that the localized movement of AGPs from the plasma membrane to the cell wall is a component of the mechanism of tip growth. Biochemical and bioinformatic analyses were used to identify seven P. patens ESTs encoding putative AGP core proteins from homology with Arabidopsis thaliana , Brassica napus , and Oryza sativa sequences and from peptide fragments isolated from βGlcYR-precipitated AGPs. Gene knockout by homologous recombination of one of these genes, P. patens AGP1 , encoding a classical AGP core protein, resulted in reduced cell lengths in protonemal filaments, indicating a role for AGP1 in apical cell expansion in P. patens .

Continuous-wave ultraviolet light induced fiber Bragg gratings in few- and single-mode microstructured polymer optical fibers

Abstract: We report observations and measurements of the inscription of fiber Bragg gratings (FBGs) in two different types of microstructured polymer optical fiber: few-mode and an endlessly single mode. Contrary to the FBG inscription in silica microstructured fiber, where high-energy laser pulses are a prerequisite, we have successfully used a low-power cw laser source operating at 325 nm to produce 1 cm long gratings with a reflection peak at 1570 nm. Peak reflectivities of more than 10% have been observed.

Genomewide Linkage Study in 1,176 Affected Sister Pair Families Identifies a Significant Susceptibility Locus for Endometriosis on Chromosome 10q26

Abstract: Endometriosis is a common gynecological disease that affects up to 10% of women in their reproductive years. It causes pelvic pain, severe dysmenorrhea, and subfertility. The disease is defined as the presence of tissue resembling endometrium in sites outside the uterus. Its cause remains uncertain despite >50 years of hypothesis-driven research, and thus the therapeutic options are limited. Disease predisposition is inherited as a complex genetic trait, which provides an alternative route to understanding the disease. We seek to identify susceptibility loci, using a positional-cloning approach that starts with linkage analysis to identify genomic regions likely to harbor these genes. We conducted a linkage study of 1,176 families (931 from an Australian group and 245 from a U.K. group), each with at least two members—mainly affected sister pairs—with surgically diagnosed disease. We have identified a region of significant linkage on chromosome 10q26 (maximum LOD score [MLS] of 3.09; genomewide P = .047) and another region of suggestive linkage on chromosome 20p13 (MLS = 2.09). Minor peaks (with MLS > 1.0) were found on chromosomes 2, 6, 7, 8, 12, 14, 15, and 17. This is the first report of linkage to a major locus for endometriosis. The findings will facilitate discovery of novel positional genetic variants that influence the risk of developing this debilitating disease. Greater understanding of the aberrant cellular and molecular mechanisms involved in the etiology and pathophysiology of endometriosis should lead to better diagnostic methods and targeted treatments.

Propagation of electromagnetic ion cyclotron wave energy in the magnetosphere

Abstract: [1] Recent satellite and conjugate observations of Pc 1 electromagnetic ion cyclotron (EMIC) waves have cast doubt on the validity of the long-standing bouncing wave packet (BWP) model that describes their propagation in the magnetosphere. A study was undertaken using the Combined Release and Radiation Effects Satellite (CRRES) E and B field data to further the understanding of the propagation characteristics of Pc 1 EMIC waves in the middle magnetosphere. CRRES covered the region L = 3.5-8.0, magnetic latitude up to ±30°, and magnetic local time 1400-0800. From 6464 hours of observation a total of 248 EMIC wave events were identified. For the first time the Poynting vector for Pc 1 EMIC waves is presented in the dynamic spectral domain permitting the study of energy propagation of simultaneous waves located in different frequency bands. The maximum wave energy flux for the events was 25 μW/m 2 , averaging range 1.3 μW/m 2 , with the direction of wave energy propagation independent of wave frequency but dependent on magnetic latitude. EMIC wave energy propagation was bidirectional both away and toward the equator, for events observed below 11° |MLat|. Unidirectional wave energy propagation away from the equator was observed for all events located above 11° |MLat|. This supports the concept of unidirectional EMIC wave energy propagation away from a broad source region centered on the geomagnetic equator. No measurable energy was observed propagating equatorward beyond the source region, in contradiction to the BWP paradigm.

Are alien fish a reliable indicator of river health

Abstract: 1. The ability of many introduced fish species to thrive in degraded aquatic habitats and their potential to impact on aquatic ecosystem structure and function suggest that introduced fish may represent both a symptom and a cause of decline in river health and the integrity of native aquatic communities. 2. The varying sensitivities of many commonly introduced fish species to degraded stream conditions, the mechanism and reason for their introduction and the differential susceptibility of local stream habitats to invasion because of the environmental and biological characteristics of the receiving water body, are all confounding factors that may obscure the interpretation of patterns of introduced fish species distribution and abundance and therefore their reliability as indicators of river health. 3. In the present study, we address the question of whether alien fish (i.e. those species introduced from other countries) are a reliable indicator of the health of streams and rivers in south-eastern Queensland, Australia. We examine the relationships of alien fish species distributions and indices of abundance and biomass with the natural environmental features, the biotic characteristics of the local native fish assemblages and indicators of anthropogenic disturbance at a large number of sites subject to varying sources and intensities of human impact. 4. Alien fish species were found to be widespread and often abundant in south-eastern Queensland rivers and streams, and the five species collected were considered to be relatively tolerant to river degradation, making them good candidate indicators of river health. Variation in alien species indices was unrelated to the size of the study sites, the sampling effort expended or natural environmental gradients. The biological resistance of the native fish fauna was not concluded to be an important factor mediating invasion success by alien species. Variation in alien fish indices was, however, strongly related to indicators of disturbance intensity describing local in-stream habitat and riparian degradation, water quality and surrounding land use, particularly the amount of urban development in the catchment. 5. Potential confounding factors that may influence the likelihood of introduction and successful establishment of an alien species and the implications of these factors for river bioassessment are discussed. We conclude that the potentially strong impact that many alien fish species can have on the biological integrity of natural aquatic ecosystems, together with their potential to be used as an initial basis to find out other forms of human disturbance impacts, suggest that some alien species (particularly species from the family Poeciliidae) can represent a reliable 'first cut' indicator of river health.