Dr Michael Johnson is responsible for light and optical imaging in the Faculty of Science at UTS. He also co-ordinates and teaches in the Advanced Microscopy and Imaging (91566) subject, that is a core requirement for the MSc (Medical Biotechnology) students.
Dr Michael Johnson has over 15 years experience in Apicomplexan parasitology, and has applied his knowledge of light and optical microscopy to many other cell types. He is highly expert in IFM, 3D imaging by confocal and widefield microscopy (with deconvolution) as well as flow cytometry. He also has expertise in image analysis.
Can supervise: YES
Subject Co-ordinator for Advanced Microscopy and Imaging (91566 & 91567) in the MSc (Medical Biotechnology) stream
Lecturer in Parasitology (91532): Apicomplexan parasites: parasite transmission and imaging
Cheng, J, Tan, Y, Zhou, J, Xiao, L, Johnson, M & Qu, X 2020, 'Green tea polyphenols ameliorate metabolic abnormalities and insulin resistance by enhancing insulin signalling in skeletal muscle of Zucker fatty rats', Clinical Science, vol. 134, no. 10, pp. 1167-1180.View/Download from: Publisher's site
©2020 The Author(s). In the present study, we evaluated the metabolic effects of green tea polyphenols (GTPs) in high-fat diet (HFD) fed Zucker fatty (ZF) rats, in particular the effects of GTP on skeletal muscle insulin sensitivity. Body weight, visceral fat, glucose tolerance, lipid profiles and whole-body insulin sensitivity were measured in HFD-fed ZF rats after 8-week-treatment with GTP (200 mg/kg of body weight) or saline (5 ml/kg of body weight). Zucker lean rats were studied as controls. Ex vivo insulin-mediated muscle glucose uptake was assessed. Immunoblotting was used to evaluate the expression of key insulin signalling proteins in skeletal muscle. GTP treatment attenuated weight gain (P<0.05) and visceral fat accumulation (27.6%, P<0.05), and significantly reduced fasting serum glucose (P<0.05) and insulin (P<0.01) levels. Homoeostasis model assessment of insulin resistance (HOMA-IR), a measure of insulin resistance, was lower (P<0.01) in GTP-treated animals compared with ZF controls. Moreover, insulin-stimulated glucose uptake by isolated soleus muscle was increased (P<0.05) in GTP-ZF rats compared with ZF-controls. GTP treatment attenuated the accumulation of ectopic lipids (triacyl- and diacyl-glycerols), enhanced the expression and translocation of glucose transporter-4, and decreased pSer612IRS-1 and increased pSer473Akt2 expression in skeletal muscle. These molecular changes were also associated with significantly decreased activation of the inhibitory (muscle-specific) protein kinase (PKC) isoform, PKC-θ. Taken together, the present study has shown that regular ingestion of GTP exerts a number of favourable metabolic and molecular effects in an established animal model of obesity and insulin resistance. The benefits of GTP are mediated in part by inhibiting PKC-θ and improving muscle insulin sensitivity.
Kuhl, M, Trampe, E, Mosshammer, M, Johnson, M, Larkum, AWD, Frigaard, N-U & Koren, K 2020, 'Substantial near-infrared radiation-driven photosynthesis of chlorophyll f-containing cyanobacteria in a natural habitat', ELIFE, vol. 9.View/Download from: Publisher's site
Espinoza-Vergara, G, Noorian, P, Silva-Valenzuela, CA, Raymond, BBA, Allen, C, Hoque, MM, Sun, S, Johnson, MS, Pernice, M, Kjelleberg, S, Djordjevic, SP, Labbate, M, Camilli, A & McDougald, D 2019, 'Vibrio cholerae residing in food vacuoles expelled by protozoa are more infectious in vivo', Nature Microbiology, vol. 4, no. 12, pp. 2466-2474.View/Download from: Publisher's site
Fisher, A, Wangpraseurt, D, Larkum, AWD, Johnson, M, Kühl, M, Chen, M, Wong, HL & Burns, BP 2019, 'Correlation of bio-optical properties with photosynthetic pigment and microorganism distribution in microbial mats from Hamelin Pool, Australia.', FEMS microbiology ecology, vol. 95, no. 1.View/Download from: Publisher's site
Microbial mats and stromatolites are widespread in Hamelin Pool, Shark Bay, however the phototrophic capacity of these systems is unknown. This study has determined the optical properties and light-harvesting potential of these mats with light microsensors. These characteristics were linked via a combination of 16S rDNA sequencing, pigment analyses and hyperspectral imaging. Local scalar irradiance was elevated over the incident downwelling irradiance by 1.5-fold, suggesting light trapping and strong scattering by the mats. Visible light (400-700 nm) penetrated to a depth of 2 mm, whereas near-infrared light (700-800 nm) penetrated to at least 6 mm. Chlorophyll a and bacteriochlorophyll a (Bchl a) were found to be the dominant photosynthetic pigments present, with BChl a peaking at the subsurface (2-4 mm). Detailed 16S rDNA analyses revealed the presence of putative Chl f-containing Halomicronema sp. and photosynthetic members primarily decreased from the mat surface down to a depth of 6 mm. Data indicated high abundances of some pigments and phototrophic organisms in deeper layers of the mats (6-16 mm). It is proposed that the photosynthetic bacteria present in this system undergo unique adaptations to lower light conditions below the mat surface, and that phototrophic metabolisms are major contributors to ecosystem function.
Ong, M, Cheng, J, Jin, X, Lao, W, Johnson, M, Tan, Y & Qu, X 2019, 'Paeoniflorin extract reverses dexamethasone-induced testosterone over-secretion through downregulation of cytochrome P450 17A1 expression in primary murine theca cells.', Journal of ethnopharmacology, vol. 229, pp. 97-103.View/Download from: Publisher's site
ETHNOPHARMACOLOGICAL RELEVANCE:Polycystic Ovarian Syndrome (PCOS) is a complex endocrine and reproductive disorder. A main hallmark includes increased androgen production. The root of Paeonia lactiflora Pall. (Bai Shao) is used in Chinese herbal medicine for reproductive disorders, however its effects and mechanisms on ovarian theca cells has not yet been fully elucidated. AIM OF THE STUDY:The aim of this study was to evaluate effect of paeoniflorin extract (PFE), the main constituents of Bai Shao, on androgen production in ovarian theca cells. MATERIALS AND METHODS:Primary murine theca cells were treated with concentrations of PFE (1-100 µg/mL) in the presence of dexamethasone (10 µM) with media-only treated cells used as the control. After 24 h, culture media was collected for biochemistry assays of testosterone and progesterone. Expression of key steroidogenic enzymes, cholesterol side-chain cleavage (CYP11A1) and 17α-hydroxylase (CYP17A1) was characterized using immunofluorescence staining, immunoblotting and qRT-PCR. RESULTS:Dexamethasone significantly enhanced testosterone secretion (P < 0.05 vs. the control cells). PFE reversed over-production of testosterone induced by dexamethasone in a dose-dependent manner. The treatment with PFE also normalized production of progesterone in dexamethasone-treated cells. Expression of CYP11A1 and CYP17A1 in the theca cells were visualised by immunofluorescence staining. All doses of PFE significantly inhibited CYP17A1 expression detected by immunoblotting, but only 100 µg/mL of PFE downregulated CYP11A1 expression and reduced CYP11A1 significantly in dexamethasone-treated theca cells. CONCLUSIONS:PFE may reduce over-secretion of testosterone in theca cells through downregulation of CYP17A1 and CYP11A1. These findings provide scientific evidence to treat ovarian hyperandrogenism with the root of Paeonia lactiflora Pall.
Donnelly, S, Huston, WM, Johnson, M, Tiberti, N, Saunders, B, O'Brien, B, Burke, C, Labbate, M & Combes, V 2017, 'Targeting the master regulator mTOR: a new approach to prevent the neurological of consequences of parasitic infections?', Parasites & Vectors, vol. 10, no. 1, pp. 1-6.View/Download from: Publisher's site
A systematic analysis of 240 causes of death in 2013 revealed that parasitic diseases were responsible for more than one million deaths. The vast majority of these fatalities resulted from protozoan infections presenting with neurological sequelae. In the absence of a vaccine, development of effective therapies is essential to improving global public health. In 2015, an intriguing strategy to prevent cerebral malaria was proposed by Gordon et al. 2015 mBio, 6:e00625. Their study suggested that inhibition of the mammalian target of rapamycin prevented experimental cerebral malaria by blocking the damage to the blood brain barrier and stopping the accumulation of parasitized red blood cells and T cells in the brain. Here, we hypothesize that the same therapeutic strategy could be adopted for other protozoan infections with a brain tropism, to prevent cerebral parasitosis by limiting pathogen replication and preventing immune mediated destruction of brain tissue.
Jaiswal, R, Johnson, MS, Pokharel, D, Krishnan, SR & Bebawy, M 2017, 'Microparticles shed from multidrug resistant breast cancer cells provide a parallel survival pathway through immune evasion.', BMC Cancer, vol. 17, no. 1, pp. 1-12.View/Download from: Publisher's site
BACKGROUND: Breast cancer is the most frequently diagnosed cancer in women. Resident macrophages at distant sites provide a highly responsive and immunologically dynamic innate immune response against foreign infiltrates. Despite extensive characterization of the role of macrophages and other immune cells in malignant tissues, there is very little known about the mechanisms which facilitate metastatic breast cancer spread to distant sites of immunological integrity. The mechanisms by which a key healthy defense mechanism fails to protect distant sites from infiltration by metastatic cells in cancer patients remain undefined. Breast tumors, typical of many tumor types, shed membrane vesicles called microparticles (MPs), ranging in size from 0.1-1 μm in diameter. MPs serve as vectors in the intercellular transfer of functional proteins and nucleic acids and in drug sequestration. In addition, MPs are also emerging to be important players in the evasion of cancer cell immune surveillance. METHODS: A comparative analysis of effects of MPs isolated from human breast cancer cells and non-malignant human brain endothelial cells were examined on THP-1 derived macrophages in vitro. MP-mediated effects on cell phenotype and functionality was assessed by cytokine analysis, cell chemotaxis and phagocytosis, immunolabelling, flow cytometry and confocal imaging. Student's t-test or a one-way analysis of variance (ANOVA) was used for comparison and statistical analysis. RESULTS: In this paper we report on the discovery of a new cellular basis for immune evasion, which is mediated by breast cancer derived MPs. MPs shed from multidrug resistant (MDR) cells were shown to selectively polarize macrophage cells to a functionally incapacitated state and facilitate their engulfment by foreign cells. CONCLUSIONS: We propose this mechanism may serve to physically disrupt the inherent immune response prior to cancer cell colonization whilst releasing mediators required for the recruitment...
Zhao, Z, Johnson, MS, Chen, B, Grace, M, Ukath, J, Lee, VS, McRobb, LS, Sedger, LM & Stoodley, MA 2016, 'Live-cell imaging to detect phosphatidylserine externalization in brain endothelial cells exposed to ionizing radiation: implications for the treatment of brain arteriovenous malformations', Journal of Neurosurgery, pp. 1-8.View/Download from: Publisher's site
Chaiyadet, S, Smout, M, Johnson, M, Whitchurch, C, Turnbull, L, Kaewkes, S, Sotillo, J, Loukas, A & Sripa, B 2015, 'Excretory/secretory products of the carcinogenic liver fluke are endocytosed by human cholangiocytes and drive cell proliferation and IL6 production', INTERNATIONAL JOURNAL FOR PARASITOLOGY, vol. 45, no. 12, pp. 773-781.View/Download from: Publisher's site
Chaiyadet, S, Sotillo, J, Smout, M, Cantacessi, C, Jones, MK, Johnson, MS, Turnbull, L, Whitchurch, CB, Potriquet, J, Laohaviroj, M, Mulvenna, J, Brindley, PJ, Bethony, JM, Laha, T, Sripa, B & Loukas, A 2015, 'Carcinogenic Liver Fluke Secretes Extracellular Vesicles That Promote Cholangiocytes to Adopt a Tumorigenic Phenotype', JOURNAL OF INFECTIOUS DISEASES, vol. 212, no. 10, pp. 1636-1645.View/Download from: Publisher's site
Smout, MJ, Sotillo, J, Laha, T, Papatpremsiri, A, Rinaldi, G, Pimenta, RN, Chan, LY, Johnson, MS, Turnbull, L, Whitchurch, CB, Giacomin, PR, Moran, CS, Golledge, J, Sripa, B, Mulvenna, JP, Brindley, PJ & Loukas, A 2015, 'Carcinogenic Parasite Secretes Growth Factor That Accelerates Wound Healing and Potentially Promotes Neoplasia', PLoS Pathogens, vol. 11, no. 10.View/Download from: Publisher's site
Infection with the human liver fluke Opisthorchis viverrini induces cancer of the bile ducts, cholangiocarcinoma (CCA). Injury from feeding activities of this parasite within the human biliary tree causes extensive lesions, wounds that undergo protracted cycles of healing, and re-injury over years of chronic infection. We show that O. viverrini secreted proteins accelerated wound resolution in human cholangiocytes, an outcome that was compromised following silencing of expression of the fluke-derived gene encoding the granulin-like growth factor, Ov-GRN-1. Recombinant Ov-GRN-1 induced angiogenesis and accelerated mouse wound healing. Ov-GRN-1 was internalized by human cholangiocytes and induced gene and protein expression changes associated with wound healing and cancer pathways. Given the notable but seemingly paradoxical properties of liver fluke granulin in promoting not only wound healing but also a carcinogenic microenvironment, Ov-GRN-1 likely holds marked potential as a therapeutic wound-healing agent and as a vaccine against an infection-induced cancer of major public health significance in the developing world.
Frolich, S, Johnson, MS, Robinson, ML, Entzeroth, R & Wallach, M 2013, 'The Spatial Organization And Extraction Of The Wall-forming Bodies Of Eimeria Maxima', Parasitology, vol. 140, no. 7, pp. 876-887.View/Download from: Publisher's site
Eimeria maxima has been used as a model apicomplexan parasite to study sexual stage development and oocyst wall formation. A complete understanding of the wall's biochemical and biophysical properties is of great interest in research on all apicomplexan parasites. Purified gametocytes, zygotes and oocysts were analysed by three-dimensional confocal microscopy, and wide-field fluorescent microscopy was used to investigate the appearance and spatial organization of the 2 types of wall-forming bodies (WFBs). In addition, a variety of staining procedures and immunoassays were used to assess the biosynthesis, metabolic activity, intactness and molecular composition of the WFBs in situ. WFBs were extracted from gametocytes/zygotes and their composition was assessed by microscopy and SDS-PAGE analysis. It was concluded that isolated gametocytes are intact and metabolically active. Additionally, it was observed that the Type 1 WFBs are aligned at the periphery of the parasite and fuse together producing neutral lipid rich patches that appear to be inserted into the space between 2 parasite-specific membranes. Finally, it was shown that the WFBs extracted from purified gametocytes had the same shape, size and staining properties as those observed in situ, and contained the major glycoprotein antigens known to be present in these organelles.
Ivanov, IE, Boyd, CD, Newell, PD, Schwartz, ME, Turnbull, L, Johnson, MS, Whitchurch, CB, O'Toole, GA & Camesano, TA 2012, 'Atomic force and super-resolution microscopy support a role for LapA as a cell-surface biofilm adhesin of Pseudomonas fluorescens', Research in Microbiology, vol. 163, no. 9-10, pp. 685-691.View/Download from: Publisher's site
Pseudomonas fluorescence Pf0-1 requires the large repeat protein LapA for stable surface attachment. This study presents direct evidence that LapA is a cell-surface-localized adhesin. Atomic force microscopy (AFM) revealed a significant 2-fold reduction in adhesion force for mutants lacking the LapA protein on the cell surface compared to the wild-type strain. Deletion of lapG, a gene encoding a periplasmic cysteine protease that functions to release LapA from the cell surface, resulted in a 2-fold increase in the force of adhesion. Three-dimensional structured illumination microscopy (3D-SIM) revealed the presence of the LapA protein on the cell surface, consistent with its role as an adhesin. The protein is only visualized in the cytoplasm for a mutant of the ABC transporter responsible for translocating LapA to the cell surface. Together, these data highlight the power of combining the use of AFM and 3D-SIM with genetic studies to demonstrate that LapA, a member of a large group of RTX-like repeat proteins, is a cell-surface adhesin
Parameswaran, N, Thompson, RS, Sundar, N, Pan, S, Johnson, MS, Smith, NC & Grigg, M 2010, 'Non-Archetypal Type Ii-Like And Atypical Strains Of Toxoplasma Gondii Infecting Marsupials Of Australia', International Journal For Parasitology, vol. 40, no. 6, pp. 635-640.View/Download from: Publisher's site
Australia is geographically isolated and possesses a remarkable diversity of wildlife species. Marsupials are highly susceptible to infection with the cosmopolitan parasite Toxoplasma gondii. Of 46 marsupials screened for T. gondii by multilocus PCR-DNA
Johnson, MS, Broady, KW, Angelici, M & Johnson, AM 2003, 'The relationship between nucleoside triphosphate hydrolase (NTPase) isoform and Toxoplasma strain virulence in rat and human toxoplasmosis', Microbes and Infection, vol. 5, pp. 797-806.View/Download from: Publisher's site
Johnson, MS, Broady, KW & Johnson, AM 1999, 'Differential recognition of Toxoplasma gondii recombinant nucleoside triphosphate hydrolase isoforms by naturally infected human sera', International Journal for Parasitology, vol. 29, no. 12, pp. 1893-1905.View/Download from: Publisher's site
Toxoplasma gondii possesses a highly active nucleoside triphosphate hydrolase, which has been shown to be an immunodominant antigen in mice and humans. Two isoforms (I and II) which exhibit different activities with respect to hydrolysis of ATP exist. Past studies suggest that all strains of T. gondii contain the less active nucleoside triphosphate hydrolase II, whilst only virulent strains contain the nucleoside triphosphate hydrolase I isoform. In order to further investigate the correlation between nucleoside triphosphate hydrolase isoform and biological significance, we cloned and expressed as glutathione S-transferase fusion proteins the full-length nucleoside triphosphate hydrolase I and II isoforms and two truncations of the nucleoside triphosphate hydrolase I isoform in Escherichia coli. We then used ELISAs with the full-length recombinant nucleoside triphosphate hydrolases as antigens to examine 188 naturally infected T. gondii-positive sera and 83 T. gondii-negative sera for antibody reactivity. All positive sera reacted to T. gondii whole tachyzoite lysate antigen, 31 sera reacted to both nucleoside triphosphate hydrolase isoforms, three sera reacted specifically to nucleoside triphosphate hydrolase I and two sera reacted to only nucleoside triphosphate hydrolase II. Immunoblot analysis of the five sera reacting to either nucleoside triphosphate hydrolase I or II revealed both quantitative and qualitative differences in reactivity to the two isoforms. Comparative immunoblot analysis using the truncations of the nucleoside triphosphate hydrolase I isoform, and one of these positive sera identified a presumptive differential epitope between the nucleoside triphosphate hydrolase I and II isoforms within an 81-aa region (aa 445-526) at the C-terminus of the nucleoside triphosphate hydrolase I isoform. This differential reactivity was further localised to the 12-residue region of greatest variability between the two isoforms (residues 488-499) using synthet...
The nucleoside triphosphate hydrolase (NTPase) of Toxoplasma gondii demonstrates an unusually high level of ATP hydrolysis, which, among the apicomplexan parasites, has only been observed in T. gondii and the closely related Neospora caninum. In T. gondii, NTPase has been shown to be highly expressed (constituting up to 8% of the tachyzoite protein) and is an immunodominant antigen in mice and humans. Two isoforms exist - NTPasel and NTPasell. NTPasel demonstrates a 4.5 fold greater activity than NTPasell with respect to ATP hydrolysis. Past studies suggest that only virulent strains possess the highly active NTPasel isoform. We have recently identified a B cell epitope (aa 484-502) on the NTPase isoforms which, despite some cross reactivity, is differentially recognised by a naturally infected human serum sample. In this study we used competitive antigen ELISAs and have identified that this serum sample reacts specifically to the NTPasel epitope, whilst the corresponding region on NTPasell isoform is the less specific cross reactive epitope. These results are consistent with the hypothesis that this patient has been infected with a virulent strain of T. gondii. Copyright© 1999, The Research Center for Protozoan Molecular Immunology.