Michael S. Roberts

University of Queensland

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Jay L. Garland

Environmental Protection Agency

Xin Liu

University of Queensland

Xiaowen Liang

Nanjing Medical University

Haolu Wang

University of Queensland

Mary Hummerick

Kennedy Space Center

Zhi Ping Xu

University of Queensland

Aaron L. Mills

University of Virginia

Tony Rector

United Technologies Corporation (Poland)

Richard F. Strayer

Michigan State University

Nicholas A. Buckley

University of Sydney

Cooperative Institutions

University of Queensland

University of Cambridge

Princess Alexandra Hospital

Translational Research Institute

University College London

Newcastle University

Kennedy Space Center

National Health Service

University of Peradeniya

South Asian Clinical Toxicology Research Collaboration

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Permeability of solutes through biological membranes measured by a desorption technique

Nature (1975)

Michael S. Roberts E. J. Triggs R. A. Anderson

10.1038/257225a0

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Citations (31)

Microbial structural diversity estimated by dilutionâextinction of phenotypic traits and T-RFLP analysis along a land-use intensification gradient

FEMS Microbiology Ecology (2004)

Elena Gómez Jay L. Garland Michael S. Roberts

The present work tested whether the relationship between functional traits and inoculum density reflected structural diversity in bacterial communities from a land-use intensification gradient applying a mathematical model. Terminal restriction fragment length polymorphism (T-RFLP) analysis was also performed to provide an independent assessment of species richness. Successive 10-fold dilutions of a soil suspension were inoculated onto Biolog GN(R) microplates. Soil bacterial density was determined by total cell and plate counts. The relationship between phenotypic traits and inoculum density fit the model, allowing the estimation of maximal phenotypic potential (Rmax) and inoculum density (KI) at which Rmax will be half-reduced. Though Rmax decreased with time elapsed since clearing of native vegetation, KI remained high in two of the disturbed sites. The genetic pool of bacterial community did not experience a significant reduction, but the active fraction responding in the Biolog assay was adversely affected, suggesting a reduction in the functional potential.

Serial dilution

Extinction (optical mineralogy)

Dilution

10.1016/j.femsec.2004.03.012

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Citations (32)

Spatio-temporal trends in livestock exposure to per- and polyfluoroalkyl substances (PFAS) inform risk assessment and management measures

Environmental Research (2023)

Antti Mikkonen N. Martin Richard N. Upton Andrew O. Barker Carolyn M. Brumley

The migration of per- and polyfluoroalkyl substances (PFAS) onto agricultural properties has resulted in the accumulation of PFAS in livestock. The environmental determinants of PFAS accumulation in livestock from the grazing environment are poorly understood, resulting in limited capacity to manage livestock exposure and subsequent transfer of PFAS through the food chain. Analytical- (n = 978 samples of soil, water, pasture, and serum matrices), farm management/practice- and livestock physiology data were collated and interrogated from environmental PFAS investigations across ten farms, from four agro-ecological regions of Victoria (Australia). Statistical analysis identified perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) as key analytes of concern for livestock bioaccumulation. PFOS and PFHxS concentrations in livestock drinking water were positively correlated with serum concentrations while other intake pathways (pasture and soil) had weaker correlations. Seasonal trends in PFAS body burden (serum concentrations) were identified and suggested to be linked to seasonal grazing behaviours and physiological water requirements. The data showed for the first time that livestock exposure to PFAS is dynamic and with relatively short elimination half-lives, there is opportunity for exposure management. Meat from cattle, grazed on PFAS impacted sites, may exceed health-based guideline values for PFAS, especially for markets with low limits (like the European Commission Maximum Limits or EC MLs). This study found that sites with mean livestock drinking water concentrations as low as 0.003 μg PFOS/L may exceed the EC ML for PFOS in cattle meat. Risk assessment can be used to prioritise site cleanup and development of management plans to reduce PFAS body burden by considering timing of stock rotation and/or supplementation of primary exposure sources.

Perfluorooctane

10.1016/j.envres.2023.115518

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Citations (8)

Distribution of Microbial Communities Associated with the Dominant High Marsh Plants and Sediments of the United States East Coast

Microbial Ecology (2004)

Linda K. Blum Michael S. Roberts Jay L. Garland Aaron L. Mills

Salt marsh

East coast

10.1007/s00248-003-1051-6

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Citations (56)

Periodic electric field enhanced transport through membranes

Journal of Membrane Science (2005)

Thomas Mollee Yuri G. Anissimov Michael S. Roberts

10.1016/j.memsci.2004.10.049

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Citations (13)

Characterization of microbial and chemical composition of shuttle wet waste with permanent gas and volatile organic compound analyses

Advances in Space Research (2004)

Barbara V. Peterson Mary Hummerick Michael S. Roberts Valdis Krumins Adrienne Kish

Biodegradable waste

Volatile organic compound

10.1016/j.asr.2003.11.005

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Citations (21)

Two-photon dual imaging platform for in vivo monitoring cellular oxidative stress in liver injury

Scientific Reports (2017)

Haolu Wang Run Zhang Kim R. Bridle Aparna Jayachandran James A. Thomas

Abstract Oxidative stress reflects an imbalance between reactive oxygen species (ROS) and antioxidants, which has been reported as an early unifying event in the development and progression of various diseases and as a direct and mechanistic indicator of treatment response. However, highly reactive and short-lived nature of ROS and antioxidant limited conventional detection agents, which are influenced by many interfering factors. Here, we present a two-photon sensing platform for in vivo dual imaging of oxidative stress at the single cell-level resolution. This sensing platform consists of three probes, which combine the turn-on fluorescent transition-metal complex with different specific responsive groups for glutathione (GSH), hydrogen peroxide (H 2 O 2 ) and hypochlorous acid (HOCl). By combining fluorescence intensity imaging and fluorescence lifetime imaging, these probes totally remove any possibility of crosstalk from in vivo environmental or instrumental factors, and enable accurate localization and measurement of the changes in ROS and GSH within the liver. This precedes changes in conventional biochemical and histological assessments in two distinct experimental murine models of liver injury. The ability to monitor real-time cellular oxidative stress with dual-modality imaging has significant implications for high-accurate, spatially configured and quantitative assessment of metabolic status and drug response.

Fluorescence-lifetime imaging microscopy

Hypochlorous acid

10.1038/srep45374

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Citations (50)

Microneedle Enhanced Delivery of Cosmeceutically Relevant Peptides in Human Skin

PLoS ONE (2014)

Yousuf Mohammed Miko Yamada Lynlee L. Lin Jeffrey E. Grice Michael S. Roberts

Peptides and proteins play an important role in skin health and well-being. They are also found to contribute to skin aging and melanogenesis. Microneedles have been shown to substantially enhance skin penetration and may offer an effective means of peptide delivery enhancement. The aim of this investigation was to assess the influence of microneedles on the skin penetration of peptides using fluorescence imaging to determine skin distribution. In particular the effect of peptide chain length (3, 4, 5 amino acid chain length) on passive and MN facilitated skin penetration was investigated. Confocal laser scanning microscopy was used to image fluorescence intensity and the area of penetration of fluorescently tagged peptides. Penetration studies were conducted on excised full thickness human skin in Franz type diffusion cells for 1 and 24 hours. A 2 to 22 fold signal improvement in microneedle enhanced delivery of melanostatin, rigin and pal-KTTKS was observed. To our knowledge this is the first description of microneedle enhanced skin permeation studies on these peptides.

Penetration (warfare)

Human skin

10.1371/journal.pone.0101956

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Citations (77)

Modelling of the SDF-1/CXCR4 regulated in vivo homing of therapeutic mesenchymal stem/stromal cells in mice

PeerJ (2018)

Jin Wang Xiaowen Liang Anastasia Brooks Kathryn Futrega Xin Liu

Mesenchymal stem/stromal cells (MSCs) are a promising tool for cell-based therapies in the treatment of tissue injury. The stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) axis plays a significant role in directing MSC homing to sites of injury. However in vivo MSC distribution following intravenous transplantation remains poorly understood, potentially hampering the precise prediction and evaluation of therapeutic efficacy.A murine model of partial ischemia/reperfusion (I/R) is used to induce liver injury, increase the hepatic levels of SDF-1, and study in vivo MSC distribution. Hypoxia-preconditioning increases the expression of CXCR4 in human bone marrow-derived MSCs. Quantitative assays for human DNA using droplet digital PCR (ddPCR) allow us to examine the in vivo kinetics of intravenously infused human MSCs in mouse blood and liver. A mathematical model-based system is developed to characterize in vivo homing of human MSCs in mouse models with SDF-1 levels in liver and CXCR4 expression on the transfused MSCs. The model is calibrated to experimental data to provide novel estimates of relevant parameter values.Images of immunohistochemistry for SDF-1 in the mouse liver with I/R injury show a significantly higher SDF-1 level in the I/R injured liver than that in the control. Correspondingly, the ddPCR results illustrate a higher MSC concentration in the I/R injured liver than the normal liver. CXCR4 is overexpressed in hypoxia-preconditioned MSCs. An increased number of hypoxia-preconditioned MSCs in the I/R injured liver is observed from the ddPCR results. The model simulations align with the experimental data of control and hypoxia-preconditioned human MSC distribution in normal and injured mouse livers, and accurately predict the experimental outcomes with different MSC doses.The modelling results suggest that SDF-1 in organs is an effective in vivo attractant for MSCs through the SDF-1/CXCR4 axis and reveal the significance of the SDF-1/CXCR4 chemotaxis on in vivo homing of MSCs. This in vivo modelling approach allows qualitative characterization and prediction of the MSC homing to normal and injured organs on the basis of clinically accessible variables, such as the MSC dose and SDF-1 concentration in blood. This model could also be adapted to abnormal conditions and/or other types of circulating cells to predict in vivo homing patterns.

Homing (biology)

10.7717/peerj.6072

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Citations (68)

Prediction of organophosphorus insecticide-induced intermediate syndrome with stimulated concentric needle single fibre electromyography

PLoS ONE (2018)

Chanika Alahakoon Tharaka L. Dassanayake Indika Gawarammana E.M. Sedgwick Vajira S. Weerasinghe

Background Deliberate self-poisoning (DSP) using organophosphorus (OP) insecticides are a common clinical problem in Asia. OPs inhibit acetylcholine esterase (AChE), leading to over-activity of muscarinic and nicotinic cholinergic circuits. Intermediate syndrome (IMS) is mediated via prolonged nicotinic receptor stimulation at the neuromuscular junction and its onset is between 24–96 hours post ingestion. The aims of the present study were 1) to investigate whether neuromuscular junction dysfunction within the first 24 hours following exposure, quantified by jitter in single fibre electromyography (SfEMG), can predict IMS, and 2) to compare the changes in SfEMG jitter over the course of the illness among patients who developed IMS (IMS+) and those who did not (IMS-). Methods and findings We conducted a prospective cohort study in a tertiary care hospital in Sri Lanka on 120 patients admitted between September 2014 and August 2016 following DSP by OP insecticides viz., profenofos 53, phenthoate 17, diazinon 13, chlorpyrifos 5, others 12, unknown 20. SfEMG was performed every second day during hospitalization. Exposure was confirmed based on the history and red blood cell AChE assays. IMS was diagnosed in patients who demonstrated at least three out of four of the standard IMS criteria: proximal muscle weakness, bulbar muscle weakness, neck muscle weakness, respiratory paralysis between 24–96 hours post ingestion. Respiratory failure requiring intubation occurred in 73 out of 120 patients; 64 of these were clinically diagnosed with IMS. Of the 120 patients, 96 had repeated SfEMG testing, 67 of them being tested within the first 24 hours. Prolonged jitter (>33.4μs) within the first 24 hours was associated with greatly increased risk of IMS (odds ratio = 8.9, 95% confidence intervals = 2.4–29.6, p = 0.0003; sensitivity 86%, specificity 58%). The differences in jitter between IMS+ and IMS- patients remained significant for 72 hours and increased jitter was observed in some patients for up to 216 hours. For intubated patients, the median time for jitter to normalize and median time to extubate were similar, and the two variables had a moderate positive correlation (r = 0.49, P = 0.001). Conclusions Prolonged jitter recorded with SfEMG <24 hours of ingestion of an OP strongly correlates with subsequent occurrence of IMS. The time course of electrophysiological recovery of the NMJ was similar to the time course of respiratory recovery in IMS patients.

10.1371/journal.pone.0203596

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Citations (13)