ORCID Profile
0000-0002-4967-209X
Current Organisations
Charles Sturt University
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With Distinction Research, Academic & Career Consultants
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Publisher: Elsevier BV
Date: 07-2001
Publisher: Elsevier BV
Date: 04-2000
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.YEXCR.2006.05.010
Abstract: Caveolae and their coat proteins, caveolins, co-ordinate multiple signaling pathways. Caveolin-3 is a muscle-specific caveolin isoform that is deficient in limb girdle muscular dystrophy type 1 C (LGMD1C). Paradoxically, overexpression of this protein also causes muscle degeneration in vivo. We hypothesize that altered membrane expression of caveolin-3 in muscle cells causes a degenerative phenotype by disrupting the co-ordination of signaling pathways that are critical to the maintenance of cell survival. Here, we show for the first time that, in normal muscle cells subjected to oxidative stress, the phosphatidylinositol (3) kinase (PI(3) kinase)-associated proteins PDK1 and Akt associate with caveolae where they bind to caveolin-3, and that normal activation of this pathway promotes cell survival. Either increased or decreased expression of caveolin-3 at the membrane caused an increased susceptibility to oxidative stress, and myotube survival was markedly improved by PI(3) kinase inhibition. This occurred concomitantly with altered phosphorylation of the pro-apoptotic proteins GSK3beta and Bad, despite normal levels of Akt activation. Taken together, our results demonstrate that altered caveolin-3 expression can change the outcome of PI(3) kinase activation from cell survival to cell death. These findings indicate that normal expression and localization of caveolin-3 are required to appropriately co-ordinate PI(3) kinase/Akt-mediated cell survival signaling, and suggest that this pathway may be an effective therapeutic target for the treatment of muscular dystrophies associated with caveolin-3 mutations.
Publisher: Springer Science and Business Media LLC
Date: 11-05-2001
Abstract: The expression of desmin, a muscle-specific intermediate filament protein, is upregulated during skeletal myogenesis, but its role in the myogenic process is unclear. Postnatal skeletal muscle regeneration occurs to completion in desmin null (-/-) mice, however, only late time points (i.e., days 7 and 21) in the myogenic process have been examined. This study observes the early events in skeletal muscle regeneration (i.e., from 3 days) in desmin (-/-) mice. Whole muscle autografts were performed in desmin (-/-) and control normal (Balb/c) mice. Muscle s les were taken on days 3, 5, 6, 7, 8, 9 and 11 after transplantation, and regeneration was assessed by graft morphology, patterns of cell proliferation and quantitation of myotube numbers. At day 5 myotube formation was delayed in the desmin (-/-) grafts compared to the normal controls. Immunohistochemical analysis of proliferating cell nuclear antigen demonstrated a very high proportion of proliferating cells in the periphery of desmin (-/-) whole muscle grafts at day 5 compared to the controls, where mitosis in this area was negligible. This strongly indicates t hat myoblast proliferation is prolonged during postnatal myogenesis in the absence of desmin. By day 6 there was no marked morphological difference between desmin (-/-) and normal control whole muscle grafts, although the zonal pattern of myoblast replication was slightly delayed in the desmin (-/-) mice until day 8. These results indicate a slightly extended phase of myoblast proliferation with delayed fusion in vivo in mature regenerating desmin (-/-) skeletal muscle.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-11-2003
Abstract: A hallmark of aging is diminished regenerative potential of tissues, but the mechanism of this decline is unknown. Analysis of injured muscle revealed that, with age, resident precursor cells (satellite cells) had a markedly impaired propensity to proliferate and to produce myoblasts necessary for muscle regeneration. This was due to insufficient up-regulation of the Notch ligand Delta and, thus, diminished activation of Notch in aged, regenerating muscle. Inhibition of Notch impaired regeneration of young muscle, whereas forced activation of Notch restored regenerative potential to old muscle. Thus, Notch signaling is a key determinant of muscle regenerative potential that declines with age.
Publisher: Oxford University Press (OUP)
Date: 07-11-2020
DOI: 10.1093/HMG/DDZ266
Abstract: Duchenne muscular dystrophy (DMD) is a lethal muscle wasting disorder caused by mutations in the DMD gene that lead to the absence or severe reduction of dystrophin protein in muscle. The mdx mouse, also dystrophin deficient, is the model most widely used to study the pathology and test potential therapies, but the phenotype is milder than human DMD. This limits the magnitude and range of histological damage parameters and molecular changes that can be measured in pre-clinical drug testing. We used three weeks of voluntary wheel running to exacerbate the mdx phenotype. In mdx mice voluntary exercise increased the amount of damaged necrotic tissue and macrophage infiltration. Global gene expression profiling revealed that exercise induced additional and larger gene expression changes in mdx mice and the pathways most impacted by exercise were all related to immune function or cell-extracellular matrix (ECM) interactions. When we compared the matrisome and inflammation genes that were dysregulated in mdx with those commonly differentially expressed in DMD, we found the exercised mdx molecular signature more closely resembled that of DMD. These gene expression changes in the exercised mdx model thus provide more scope to assess the effects of pre-clinical treatments. Our gene profiling comparisons also highlighted upregulation of extracellular matrix proteins involved in innate immunity pathways, proteases that can release them, and downstream receptors and signalling molecules in exercised mdx and DMD, suggesting that the ECM could be a major source of pro-inflammatory molecules that trigger and maintain the immune response in dystrophic muscle.
Publisher: Wiley
Date: 20-08-2012
DOI: 10.1002/MUS.23312
Abstract: Duchenne muscular dystrophy (DMD) results from a deficiency in the protein, dystrophin. Dystrophic myotubes are susceptible to stressful stimuli. This may be partly due to altered regulation of pro-survival signaling pathways, but a role for mitogen-activated protein (MAP) kinases has not been investigated. We examined patterns of phosphorylation of key MAP kinase proteins in cultured myotubes responding to oxidative stress, and in muscle tissue in vivo. Dystrophic (mdx) myotubes have an increased susceptibility to oxidant-induced death compared with wild-type (C57Bl/10ScSn) myotubes. This correlates with late phosphorylation of c-Jun N-terminal kinase (JNK), and persistently high p38 MAP kinase phosphorylation in mdx myotubes. JNK and extracellular signal-regulated kinase 1/2 (ERK1/2) also showed altered phosphorylation levels in mdx muscle tissue. We show altered patterns of MAP kinase protein phosphorylation in dystrophic muscle in vitro and in vivo. These pathways may be novel pharmacological targets for treating DMD.
Publisher: Springer International Publishing
Date: 2016
DOI: 10.1007/978-3-319-27511-6_7
Abstract: Post-natal skeletal muscle is a highly plastic tissue that has the capacity to regenerate rapidly following injury, and to undergo significant modification in tissue mass (i.e. atrophy/hypertrophy) in response to global metabolic changes. These processes are reliant largely on soluble factors that directly modulate muscle regeneration and mass. However, skeletal muscle function also depends on an adequate blood supply. Thus muscle regeneration and changes in muscle mass, particularly hypertrophy, also demand rapid changes in the microvasculature. Recent evidence clearly demonstrates a critical role for soluble growth factors in the tight regulation of angiogenic expansion of the muscle microvasculature. Furthermore, exogenous modulation of these factors has the capacity to impact directly on angiogenesis and thus, indirectly, on muscle regeneration, growth and performance. This chapter reviews recent developments in understanding the role of growth factors in modulating the skeletal muscle microvasculature, and the potential therapeutic applications of exogenous angiogenic and anti-angiogenic mediators in promoting effective growth and regeneration, and ameliorating certain diseases, of skeletal muscle.
Publisher: The Company of Biologists
Date: 12-2003
DOI: 10.1242/JCS.00806
Abstract: Caveolins are membrane proteins that are the major coat proteins of caveolae, specialized lipid rafts in the plasma membrane that serve as scaffolding sites for many signaling complexes. Among the many signaling molecules associated with caveolins are the Src tyrosine kinases, whose activation regulates numerous cellular functions including the balance between cell survival and cell death. Several mutations in the muscle-specific caveolin, caveolin-3, lead to a form of autosomal dominant muscular dystrophy referred to as limb girdle muscular dystrophy type 1C (LGMD-1C). One of these mutations (here termed the `TFT mutation') results in a deletion of a tripeptide (ΔTFT(63-65)) that affects the scaffolding and oligomerization domains of caveolin-3. This mutation causes a 90-95% loss of caveolin-3 protein levels and reduced formation of caveolae in skeletal muscle fibers. However, the effects of this mutation on the specific biochemical processes and cellular functions associated with caveolae have not been elucidated. We demonstrate that the TFT caveolin-3 mutation in post-mitotic skeletal myotubes causes severely reduced localization of caveolin-3 to the plasma membrane and to lipid rafts, and significantly inhibits caveolar function. The TFT mutation reduced the binding of Src to caveolin-3, diminished targeting of Src to lipid rafts, and caused abnormal perinuclear accumulation of Src. Along with these alterations of Src localization and targeting, there was elevated Src activation in myotubes expressing the TFT mutation and an increased incidence of apoptosis in those cells compared with control myotubes. The results of this study demonstrate that caveolin-3 mutations associated with LGMD-1C disrupt normal cellular signal transduction pathways associated with caveolae and cause apoptosis in muscle cells, all of which may reflect pathogenetic pathways that lead to muscle degeneration in these disorders.
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.EXGER.2008.02.005
Abstract: Injured skeletal muscle generally regenerates less efficiently with age, but little is understood about the effects of ageing on the very early inflammatory and neovascular events in the muscle repair process. This study used a total of 174 whole muscle grafts transplanted within and between young and old mice to analyse the effects of ageing on the early inflammatory response in two strains of mice (BALB/c and SJL/J). There was a very slight delay in the early inflammatory response, and in the appearance of myotubes at day 4 in BALB/c muscle grafted into an old host environment (implicating systemic events). In SJL/J mice, the initial speed of the inflammatory response was slightly delayed with old muscle grafts regardless of host age (implicating muscle-derived factors), while an old host environment transiently affected myogenesis (myotube formation). The slight delays in inflammatory and neovascular responses in old mice did not dramatically impact on the overall formation of new muscle. The neovascular response to injured young and old muscle tissue was further analysed using the corneal micropocket assay. This showed a very clear 1-2 day delay in angiogenesis induced by old versus young BALB/c muscle tissue implanted into the young rat cornea, indicating that new blood vessel formation is at least partly determined by muscle-derived factors. Taken together these results indicate that, while there are slight age-associated delays in inflammation and neovascularisation in response to injured muscle, there is no detrimental effect on myogenesis in the mouse model used in this study.
Publisher: Springer International Publishing
Date: 2016
Publisher: Wiley
Date: 07-2008
DOI: 10.1002/ASE.33
Abstract: Speech pathology students enrolled in a lecture-based gross human anatomy program completed two out of nine topics in self-directed mode. Student performance in quizzes was compared for the two modes, and the students completed questionnaires on their perceptions of the self-directed mode of delivery. Students performed as well in the first self-directed topic as they did in lecture-based material, but performance declined significantly on the second self-directed topic. Correlations showed that students who performed well in lecture-based topics also performed well on self-directed topics. The major issues that arose in the student questionnaires were primarily related to the amount of content in the topics and the length of time required for completion. We conclude that there is a strong need for appropriate design of distance education materials to reflect student perceptions of length, content, and time investment, and more importantly that there is a need to ensure extensive communication and support of students studying in distance education/self-directed modes for the first time.
Publisher: Wiley
Date: 2001
Publisher: Mary Ann Liebert Inc
Date: 10-2002
DOI: 10.1089/10763270260424240
Abstract: Successful clinical transplantation of whole skeletal muscles can be limited by impaired muscle revascularization and regeneration. The aim of this study was to enhance the revascularization (and hence speed of regeneration) of transplanted whole muscles by transducing muscles with the vascular endothelial growth factor (VEGF) gene before transplantation, using a recombinant adeno-associated virus (rAAV). The rAAV encoding VEGF and green fluorescent protein (GFP) (rAAV.VEGF.GFP) was injected into the tibialis anterior muscles of adult BALB/c mice. One month after injection whole muscle autotransplantation was performed. Muscles were s led 7 days after autografting. GFP expression was examined as an indicator of persistent transgene expression after grafting, and immunohistochemistry was used to identify VEGF, blood vessels, and newly formed myotubes. After grafting, GFP expression persisted only in a few surviving myofibers in the periphery of rAAV.VEGF.GFP-pretreated muscles, although abundant VEGF expression was seen in myogenic cells in all grafted muscles. Quantitative analysis demonstrated that, although only small numbers of rAAV.VEGF.GFP-transduced myofibers were present, whole muscle grafts preinjected with rAAV.VEGF.GFP were significantly more vascular than saline-injected and uninjected control muscle grafts. Furthermore, rAAV.VEGF.GFP-injected whole muscle transplants were further advanced in terms of regeneration (myotube formation) compared with the uninjected control muscle transplants. This study clearly shows that rAAV-mediated VEGF expression persists only in myofibers that survive the necrosis induced by muscle transplantation however, this amount of VEGF results in significantly increased revascularization and regeneration of whole muscle transplants.
Publisher: Bentham Science Publishers Ltd.
Date: 10-2013
Publisher: Wiley
Date: 04-2000
DOI: 10.1002/(SICI)1097-4598(200004)23:4<560::AID-MUS16>3.0.CO;2-G
Abstract: Sliced male C57Bl/10Sn (H2-b) donor muscles were grafted into the female histocompatible muscles of untreated, FK506-treated, and T-cell depleted (with or without thymic tolerization) dystrophic (mdx H2-b) and normal (C57Bl/10Sn H2-b) hosts, and also into histoincompatible normal (Balb/c H2-d) hosts. The fate of male donor nuclei was monitored on tissue sections by in situ hybridization with a Y-chromosome specific probe. The results demonstrate that the dystrophic environment is more conducive than normal muscle to donor myoblast migration, with the distance moved being threefold greater at 12 weeks in dystrophic hosts. T-cell depletion was significantly more effective than FK506 treatment at enhancing donor myoblast emigration in both histocompatible and histoincompatible hosts at 3 weeks. Furthermore, the effects of T-cell depletion were sustained in histoincompatible hosts at 12 weeks. These data endorse the use of host T-cell depletion as a promising long-term strategy to improve myoblast transfer therapy (MTT) in the clinical situation.
Publisher: SAGE Publications
Date: 05-2000
DOI: 10.1177/096368970000900309
Abstract: The effects of tissue culture conditions on the viability of myoblasts in whole muscles transplanted in vivo were investigated. Whole male (SJL/J) donor muscles were exposed to various tissue culture reagents and proteolytic enzymes, and allografted into female (SJL/J) host mice. Desmin immunohistochemistry was used to assess the numbers of myogenic cells (as an index of myoblast viability and the extent of regeneration) in tissue sections of whole-muscle grafts s led on days 7 and 14. DNA quantitation with a Y-chromosome-specific probe was used to determine the total Y-1 sequence DNA (as an index of myoblast survival and proliferation) in whole-muscle grafts s led on days 1, 3, and 7. In grafts exposed to serum-free medium, there was a delay in myoblast fusion at 7 days that was recovered by 14 days, but exposure to serum (10% or 20%) had a prolonged adverse effect on myotube formation at 14 days. DNA quantitation demonstrated that either serum-free culture medium or 10% serum enhanced the number of male cells within whole-muscle grafts at 7 days. Proteolytic digestion (even for 5 min) of whole muscles prior to grafting was extremely detrimental to myoblast survival and viability at 7 and 14 days. The unexpected finding of adverse effects of tissue culture conditions on the regeneration of whole-muscle grafts in vivo appears to parallel the major problem of the rapid death of isolated cultured donor myoblasts after injection in myoblast transfer therapy. The use of whole-muscle grafts provides an alternative and sensitive model to analyze the crucial effects of various tissue culture components on the subsequent survival and proliferation of myogenic cells in vivo.
Publisher: Public Library of Science (PLoS)
Date: 19-03-2012
Location: Australia
No related grants have been discovered for Gayle Smythe.