Florey Department of Neuroscience and Mental Health - Research Publications
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ItemVery early mobilization following acute stroke: Controversies, the unknowns, and a way forward(WOLTERS KLUWER MEDKNOW PUBLICATIONS, 2008-01)UNLABELLED: Evidence that organized stroke-unit care results in better outcome has led to positive changes in stroke service delivery around the world. It is well accepted that stroke rehabilitation should commence as early as possible for optimal recovery to be achieved. Exactly how early rehabilitation should start is controversial. Early mobilization (getting up out of bed within 24 h of stroke onset) is a wellestablished feature of acute stroke care in many Scandinavian hospitals. Elsewhere in the world, stroke protocols enforce bed rest for the first few days or foster long periods of bed rest after stroke. This paper aims to provide an overview of the topic of very early mobilization (VEM). It is divided into three sections: section 1 reviews the effects of bed rest and outlines arguments both for and against enforced bed rest after stroke; in section 2, VEM as a treatment for stroke and the limitations of existing literature in the field are described; and section 3 outlines the systematic approach that has been taken by our team of clinical researchers to the study the effect of VEM after stroke. CONCLUSION: VEM represents a simple, easy-to-deliver intervention, requiring little or no equipment. It is potentially deliverable to 85% of the acute stroke population and, if proven to be effective, may help reduce the significant personal and community burden of stroke. As current opinion about when mobilization should begin is divided, one way to move forward is through the conduct of a large high-quality clinical trial (such as A Very Early Rehabilitation Trial (AVERT)). Although some inroads have been made, further research in this field is clearly warranted.
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ItemDecline in Physical Fitness From Childhood to Adulthood Associated With Increased Obesity and Insulin Resistance in Adults(AMER DIABETES ASSOC, 2009-04)OBJECTIVE: To examine how fitness in both childhood and adulthood is associated with adult obesity and insulin resistance. RESEARCH DESIGN AND METHODS: A prospective cohort study set in Australia in 2004-2006 followed up a cohort of 647 adults who had participated in the Australian Schools Health and Fitness Survey in 1985 and who had undergone anthropometry and cardiorespiratory fitness assessment during the survey. Outcome measures were insulin resistance and obesity, defined as a homeostasis model assessment index above the 75th sex-specific percentile and BMI >or=30 kg/m(2), respectively. RESULTS: Lower levels of child cardiorespiratory fitness were associated with increased odds of adult obesity (adjusted odds ratio [OR] per unit decrease 3.0 [95% CI 1.6-5.6]) and insulin resistance (1.7 [1.1-2.6]). A decline in fitness level between childhood and adulthood was associated with increased obesity (4.5 [2.6-7.7]) and insulin resistance (2.1 [1.5-2.9]) per unit decline. CONCLUSIONS: A decline in fitness from childhood to adulthood, and by inference a decline in physical activity, is associated with obesity and insulin resistance in adulthood. Programs aimed at maintaining high childhood physical activity levels into adulthood may have potential for reducing the burden of obesity and type 2 diabetes in adults.
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ItemNo Preview AvailableAβ aggregation and possible implications in Alzheimer's disease pathogenesis(WILEY, 2009-03)Amyloid beta protein (Abeta) has been associated with Alzheimer's disease (AD) because it is a major component of the extracellular plaque found in AD brains. Increased Abeta levels correlate with the cognitive decline observed in AD. Sporadic AD cases are thought to be chiefly associated with lack of Abeta clearance from the brain, unlike familial AD which shows increased Abeta production. Abeta aggregation leading to deposition is an essential event in AD. However, the factors involved in Abeta aggregation and accumulation in sporadic AD have not been completely characterized. This review summarizes studies that have examined the factors that affect Abeta aggregation and toxicity. By necessity these are studies that are performed with recombinant-derived or chemically synthesized Abeta. The studies therefore are not done in animals but in cell culture, which includes neuronal cells, other mammalian cells and, in some cases, non-mammalian cells that also appear susceptible to Abeta toxicity. An understanding of Abeta oligomerization may lead to better strategies to prevent AD.
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ItemNo Preview AvailableCopper binding to the Alzheimer's disease amyloid precursor protein(SPRINGER, 2008-03)Alzheimer's disease is the fourth biggest killer in developed countries. Amyloid precursor protein (APP) plays a central role in the development of the disease, through the generation of a peptide called A beta by proteolysis of the precursor protein. APP can function as a metalloprotein and modulate copper transport via its extracellular copper binding domain (CuBD). Copper binding to this domain has been shown to reduce A beta levels and hence a molecular understanding of the interaction between metal and protein could lead to the development of novel therapeutics to treat the disease. We have recently determined the three-dimensional structures of apo and copper bound forms of CuBD. The structures provide a mechanism by which CuBD could readily transfer copper ions to other proteins. Importantly, the lack of significant conformational changes to CuBD on copper binding suggests a model in which copper binding affects the dimerisation state of APP leading to reduction in A beta production. We thus predict that disruption of APP dimers may be a novel therapeutic approach to treat Alzheimer's disease.
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ItemFamily clustering of viliuisk encephalomyelitis in traditional and new geographic regions(CENTER DISEASE CONTROL, 2007-09)Viliuisk encephalomyelitis is an acute, often fatal, meningoencephalitis that tends to develop into a prolonged chronically progressive panencephalitis. Clinical, neuropathologic, and epidemiologic data argue for an infectious cause, although multiple attempts at pathogen isolation have been unsuccessful. To assess mechanisms of disease transmission and spread, we studied 6 multiplex families. Secondary cases occurred among genetically related and unrelated persons in a setting of prolonged intrahousehold contact with a patient manifesting the disease. Transmission to unrelated persons was documented in a densely populated region around the city of Yakutsk in which Viliuisk encephalomyelitis had not been previously known. Initially identified in a small Yakut-Evenk population on the Viliui River of eastern Siberia, the disease subsequently spread through human contacts to new geographic areas, thus characterizing Viliuisk encephalomyelitis as an emerging infectious disease.
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ItemAn Ancient Duplication of Exon 5 in the Snap25 Gene Is Required for Complex Neuronal Development/Function(PUBLIC LIBRARY SCIENCE, 2008-11)Alternative splicing is an evolutionary innovation to create functionally diverse proteins from a limited number of genes. SNAP-25 plays a central role in neuroexocytosis by bridging synaptic vesicles to the plasma membrane during regulated exocytosis. The SNAP-25 polypeptide is encoded by a single copy gene, but in higher vertebrates a duplication of exon 5 has resulted in two mutually exclusive splice variants, SNAP-25a and SNAP-25b. To address a potential physiological difference between the two SNAP-25 proteins, we generated gene targeted SNAP-25b deficient mouse mutants by replacing the SNAP-25b specific exon with a second SNAP-25a equivalent. Elimination of SNAP-25b expression resulted in developmental defects, spontaneous seizures, and impaired short-term synaptic plasticity. In adult mutants, morphological changes in hippocampus and drastically altered neuropeptide expression were accompanied by severe impairment of spatial learning. We conclude that the ancient exon duplication in the Snap25 gene provides additional SNAP-25-function required for complex neuronal processes in higher eukaryotes.
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ItemThe neuropathology of kuru and variant Creutzfeldt-Jakob disease(ROYAL SOC, 2008-11-27)A comparison of the pathological profiles of two spongiform encephalopathies with a similar presumptive route of infection was performed. Archival kuru and recent variant Creutzfeldt-Jakob disease (vCJD) cases reveal distinct lesional differences, particularly with respect to prion protein, suggesting that the strain of agent is important in determining the phenotype. Genotype analysis of the polymorphism on codon 129 reveals (in conjunction with updated information from more kuru cases) that all three genotypes (VV, MV and MM (where M is methionine and V is valine)) are detected in kuru with some preference for MM homozygosity. The presence of valine does not therefore appear to determine peripheral selection of PrPCJD. vCJD remains restricted to date to MM homozygosity on codon 129. It remains to be determined whether this genotype is dictating a shorter incubation period.
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ItemDevelopment and management of systemic lupus erythematosus in an HIV-infected man with hepatitis C and B co-infection following interferon therapy: a case report.(Springer Science and Business Media LLC, 2009-06-10)INTRODUCTION: The association of human immunodeficiency virus and immune dysfunction leading to development of autoimmune markers is well described, but human immunodeficiency virus infection is relatively protective for the development of systemic lupus erythematosus. In contrast, development of systemic lupus erythematosus with hepatitis C and with interferon therapy is well described in a number of case reports. We here describe the first case of systemic lupus erythematosus developing in a man infected with human immunodeficiency virus, hepatitis C and hepatitis B co-infection where the onset seems to have been temporally related to interferon therapy. CASE PRESENTATION: We report the occurrence of systemic lupus erythematosus complicating interferon-alpha therapy for hepatitis C in a 47-year-old asplenic male with haemophilia co-infected with human immunodeficiency virus and hepatitis B. He presented with a truncal rash, abdominal pains and headache and later developed grade IV lupus nephritis requiring haemodialysis, mycophenolate mofetil and steroid therapy. We were able to successfully withdraw dialysis and mycophenolate while maintaining stable renal function. CONCLUSION: Interferon-alpha is critical in antiviral immunity against hepatitis C but also acts as a pathogenic mediator for systemic lupus erythematosus, a condition associated with activation of plasmacytoid dendritic cells that are depleted in human immunodeficiency virus infection. The occurrence of auto-antibodies and lupus-like features in the coinfections with hepatitis C require careful assessment. Immunosuppressant therapy for lupus risks exacerbating underlying infections in patients with concurrent human immunodeficiency virus, hepatitis B and C.
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ItemDocosahexaenoic and eicosapentaenoic acids increase prion formation in neuronal cells(BIOMED CENTRAL LTD, 2008-09-12)BACKGROUND: The transmissible spongiform encephalopathies, otherwise known as prion diseases, occur following the conversion of the cellular prion protein (PrPC) to an alternatively folded, disease-associated isoform (PrPSc). Recent studies suggest that this conversion occurs via a cholesterol-sensitive process, as cholesterol synthesis inhibitors reduced the formation of PrPSc and delayed the clinical phase of scrapie infection. Since polyunsaturated fatty acids also reduced cellular cholesterol levels we tested their effects on PrPSc formation in three prion-infected neuronal cell lines (ScGT1, ScN2a and SMB cells). RESULTS: We report that treatment with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) or the cholesterol synthesis inhibitor simvastatin reduced the amounts of free cholesterol in membrane extracts from prion-infected neuronal cells. Simvastatin reduced cholesterol production while DHA and EPA promoted the conversion of free cholesterol to cholesterol esters. Crucially, while simvastatin reduced PrPSc formation, both DHA and EPA significantly increased the amounts of PrPSc in these cells. Unlike simvastatin, the effects of DHA and EPA on PrPSc content were not reversed by stimulation of cholesterol synthesis with mevalonate. Treatment of ScGT1 cells with DHA and EPA also increased activation of cytoplasmic phospholipase A2 and prostaglandin E2 production. Finally, treatment of neuronal cells with DHA and EPA increased the amounts of PrPC expressed at the cell surface and significantly increased the half-life of biotinylated PrPC. CONCLUSION: We report that although treatment with DHA or EPA significantly reduced the free cholesterol content of prion-infected cells they significantly increased PrPSc formation in three neuronal cell lines. DHA or EPA treatment of infected cells increased activation of phospholipase A2, a key enzyme in PrPSc formation, and altered the trafficking of PrPC. PrPC expression at the cell surface, a putative site for the PrPSc formation, was significantly increased, and the rate at which PrPC was degraded was reduced. Cholesterol depletion is seen as a potential therapeutic strategy for prion diseases. However, these results indicate that a greater understanding of the precise relationship between membrane cholesterol distribution, PrPC trafficking, cell activation and PrPSc formation is required before cholesterol manipulation can be considered as a prion therapeutic.
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ItemGlimepiride Reduces the Expression of PrPC, Prevents PrPSc Formation and Protects against Prion Mediated Neurotoxicity(PUBLIC LIBRARY SCIENCE, 2009-12-09)BACKGROUND: A hallmark of the prion diseases is the conversion of the host-encoded cellular prion protein (PrP(C)) into a disease related, alternatively folded isoform (PrP(Sc)). The accumulation of PrP(Sc) within the brain is associated with synapse loss and ultimately neuronal death. Novel therapeutics are desperately required to treat neurodegenerative diseases including the prion diseases. PRINCIPAL FINDINGS: Treatment with glimepiride, a sulphonylurea approved for the treatment of diabetes mellitus, induced the release of PrP(C) from the surface of prion-infected neuronal cells. The cell surface is a site where PrP(C) molecules may be converted to PrP(Sc) and glimepiride treatment reduced PrP(Sc) formation in three prion infected neuronal cell lines (ScN2a, SMB and ScGT1 cells). Glimepiride also protected cortical and hippocampal neurones against the toxic effects of the prion-derived peptide PrP82-146. Glimepiride treatment significantly reduce both the amount of PrP82-146 that bound to neurones and PrP82-146 induced activation of cytoplasmic phospholipase A(2) (cPLA(2)) and the production of prostaglandin E(2) that is associated with neuronal injury in prion diseases. Our results are consistent with reports that glimepiride activates an endogenous glycosylphosphatidylinositol (GPI)-phospholipase C which reduced PrP(C) expression at the surface of neuronal cells. The effects of glimepiride were reproduced by treatment of cells with phosphatidylinositol-phospholipase C (PI-PLC) and were reversed by co-incubation with p-chloromercuriphenylsulphonate, an inhibitor of endogenous GPI-PLC. CONCLUSIONS: Collectively, these results indicate that glimepiride may be a novel treatment to reduce PrP(Sc) formation and neuronal damage in prion diseases.