Medicine (Austin & Northern Health) - Research Publications
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ItemFunctionally distinct PI 3-kinase pathways regulate myelination in the peripheral nervous system.(Rockefeller University Press, 2014-03-31)The PI 3-kinase (PI 3-K) signaling pathway is essential for Schwann cell myelination. Here we have characterized PI 3-K effectors activated during myelination by probing myelinating cultures and developing nerves with an antibody that recognizes phosphorylated substrates for this pathway. We identified a discrete number of phospho-proteins including the S6 ribosomal protein (S6rp), which is down-regulated at the onset of myelination, and N-myc downstream-regulated gene-1 (NDRG1), which is up-regulated strikingly with myelination. We show that type III Neuregulin1 on the axon is the primary activator of S6rp, an effector of mTORC1. In contrast, laminin-2 in the extracellular matrix (ECM), signaling through the α6β4 integrin and Sgk1 (serum and glucocorticoid-induced kinase 1), drives phosphorylation of NDRG1 in the Cajal bands of the abaxonal compartment. Unexpectedly, mice deficient in α6β4 integrin signaling or Sgk1 exhibit hypermyelination during development. These results identify functionally and spatially distinct PI 3-K pathways: an early, pro-myelinating pathway driven by axonal Neuregulin1 and a later-acting, laminin-integrin-dependent pathway that negatively regulates myelination.
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ItemComparison of sequence variants in transcriptomic control regions across 17 mouse genomes.(Oxford University Press (OUP), 2014)The laboratory mouse is the most widely used mammalian model organism in biomedical research, so a thorough annotation of functional variation in the mouse genome would be of significant value. In this study, we compared sequence variation in a comprehensive list of functional elements (e.g. promoters, enhancers and CTCF binding sites) across 17 inbred mouse strains. Sequences were derived for ∼300,000 functional elements experimentally identified by the mouse ENCODE project as regulating gene expression in 19 different tissue sources. We aligned sequences for each predicted cis-regulatory element to genomes of 17 mouse strains. This yielded a database comprising ∼5 million aligned sequences, allowing interrogation of sequence variation of functional elements for each of the 19 tissues/cell types in commonly used mouse strains. We also developed an online tool to visualize the genome around each predicted cis-regulatory element in each tissue context and which allows efficient comparison of variation between any two sets of strains. This will be particularly useful in the context of the Collaborative Cross (CC), which was conceived as a powerful new systems genetics resource to accelerate gene discovery. Comprising a large number of inbred strains derived from eight genetically diverse founders, the CC offers rapid mapping and identification of genes that mediate complex traits. We show that, among the 17 sequenced strains, the set of CC founder strains captures the most variability in the ENCODE elements, further emphasizing the value of this resource. Database URL: www.sysgen.org/ecco.
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ItemEx vivo restimulation of human PBMC expands a CD3+CD4-CD8- γδ+ T cell population that can confound the evaluation of CD4 and CD8 T cell responses to vaccination.(Hindawi Limited, 2013)The measurement of vaccine-induced humoral and CD4(+) and CD8(+) cellular immune responses represents an important correlate of vaccine efficacy. Accurate and reliable assays evaluating such responses are therefore critical during the clinical development phase of vaccines. T cells play a pivotal role both in coordinating the adaptive and innate immune responses and as effectors. During the assessment of cell-mediated immunity (CMI) in subjects participating in a large-scale influenza vaccine trial, we identified the expansion of an IFN-γ-producing CD3(+)CD4(-)CD8(-) γδ (+) T cell population in the peripheral blood of 90/610 (15%) healthy subjects. The appearance of CD3(+)CD4(-)CD8(-) γδ (+) T cells in the blood of subjects was transient and found to be independent of the study cohort, vaccine group, subject gender and ethnicity, and ex vivo restimulation conditions. Although the function of this population and relevance to vaccination are unclear, their inclusion in the total vaccine-specific T-cell response has the potential to confound data interpretation. It is thus recommended that when evaluating the induction of IFN-γ-producing CD4(+) and CD8(+) immune responses following vaccination, the CD3(+)CD4(-)CD8(-) γδ (+) T cells are either excluded or separately enumerated from the overall frequency determination.
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ItemOsteoprotegerin Is an Independent Predictor of Vascular Events in Finnish Adults With Type 1 Diabetes(AMER DIABETES ASSOC, 2013-07)OBJECTIVE: Osteoprotegerin (OPG) is involved in the process of vascular calcification. We investigated whether OPG is associated with the development and progression of diabetes complications in adults with type 1 diabetes (T1D). RESEARCH DESIGN AND METHODS: Serum OPG was measured in 1,939 adults with T1D participating in the Finnish Diabetic Nephropathy (FinnDiane) Study. Patients with end-stage renal disease (dialysis or transplantation) at baseline were excluded from analysis. Data on cardiovascular (CV) events and mortality during follow-up were verified from hospital discharge registries (ICD codes) and the Finnish National Death Registry, respectively. The follow-up time was 10.4 ± 2.0 (mean ± SD) years. RESULTS: Only patients with macroalbuminuria and/or renal impairment had elevated OPG concentrations, when compared with participants without overt kidney disease. Patients with retinopathy or CV disease also had higher OPG concentrations, but this was attributable to their higher frequency of chronic kidney disease. OPG predicted an incident CV event (hazard ratio 1.21 [95% CI 1.01-1.45]; P = 0.035) and peripheral vascular disease/amputation events (1.46 [1.13-1.88]; P = 0.004) during follow-up. CONCLUSIONS: We showed that serum OPG is an independent predictor of CV complications. OPG may be directly involved in extraosseous calcification, resulting in stiffening of the arteries and subsequent vascular insufficiency in patients with T1D.
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ItemAdvanced glycation end products (AGEs) are cross-sectionally associated with insulin secretion in healthy subjects(SPRINGER WIEN, 2014-02)It has been postulated that chronic exposure to high levels of advanced glycation end products (AGEs), in particular from dietary sources, can impair insulin secretion. In the present study, we investigated the cross-sectional relationship between AGEs and acute insulin secretion during an intravenous glucose tolerance test (IVGTT) and following a 75 g oral glucose tolerance test (OGTT) in healthy humans. We report the cross-sectional association between circulating AGE concentrations and insulin secretory function in healthy humans (17 F: 27 M, aged 30 ± 10 years) with a wide range of BMI (24.6-31.0 kg/m(2)). Higher circulating concentrations of AGEs were related to increased first phase insulin secretion during IVGTT (r = 0.43; p < 0.05) and lower 2-h glucose concentrations during OGTT (r = -0.31; p < 0.05). In addition, fasting (r = -0.36; p < 0.05) and 2-h glucose concentrations were negatively related to circulating levels of soluble receptor for AGE (RAGE) isoforms (r = -0.39; p < 0.01). In conclusion, in healthy humans, we show a cross-sectional association between advanced glycation end products and acute insulin secretion during glucose tolerance testing.
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ItemExercise-induced inhibition of remodelling is focally offset with fatigue fracture in racehorses(SPRINGER LONDON LTD, 2013-07)UNLABELLED: Bone remodelling is inhibited by high repetitive loading. However, in subchondral bone of racehorses in training, eroded surface doubled in association with fatigue fracture and there was greater surrounding trabecular bone volume suggesting trabecular modelling unloads the bone focally, allowing damage repair by remodelling. INTRODUCTION: Remodelling replaces damaged bone with new bone but is suppressed during high magnitude repetitive loading when damage is most likely. However, in cortical bone of racehorses, at sites of fatigue fracture, focal porosity, consistent with remodelling, is observed in proportion to the extent of surrounding callus. Focal areas of porosity are also observed at sites of fatigue damage in subchondral bone. We hypothesised that fatigued subchondral bone, like damaged cortical bone, is remodelled focally in proportion to the modelling of surrounding trabecular bone. METHODS: Eroded and mineralizing surfaces and bone area were measured using backscattered scanning electron microscopy of post-mortem specimens of the distal third metacarpal bone in 11 racehorses with condylar fractures (cases) and eight racehorses in training without fractures (controls). RESULTS: Cases had a two-fold greater eroded surface per unit area at the fracture site than controls (0.81 ± 0.10 vs. 0.40 ± 0.12 mm(-1), P = 0.021) but not at an adjacent site (0.22 ± 0.09 vs. 0.30 ± 0.11 mm(-1), P = 0.59). Area fraction of surrounding trabecular bone was higher in cases than controls (81 ± 2 vs. 72 ± 2 %, P = 0.0020) and the eroded surface at the fracture site correlated with the surrounding trabecular area (adjusted R (2) = 0.63, P = 0.0010). CONCLUSION: In conclusion, exercise-induced inhibition of remodelling is offset at sites of fatigue fracture. Modelling of trabecular bone may contribute to unloading these regions, allowing repair by remodelling.
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ItemEffects of epithelial to mesenchymal transition on T cell targeting of melanoma cells.(Frontiers Media SA, 2014)Melanoma cells can switch phenotype in a manner similar to epithelial to mesenchymal transition (EMT). In this perspective article, we address the effects of such phenotype switching on T cell targeting of tumor cells. During the EMT-like switch in phenotype, a concomitant change in expression of multiple tumor antigens occurs. Melanoma cells undergoing EMT escape from killing by T cells specific for antigens whose expression is downregulated by this process. We discuss melanoma antigens whose expression is influenced by EMT. We assess the effect of changes in the expressed tumor antigen repertoire on T-cell mediated tumor recognition and killing. In addition to escape from T cell immunity via changes in antigen expression, mesenchymal-like melanoma cells are generally more resistant to classical chemotherapy and radiotherapy. However, we demonstrate that when targeting antigens whose expression is unaltered during EMT, the capacity of T cells to kill melanoma cell lines in vitro is not influenced by their phenotype. When considering immune therapies such as cancer vaccination, these data suggest escape from T cell killing due to phenotype switching in melanoma could potentially be avoided by careful selection of target antigen.
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ItemWidespread EEG Changes Precede Focal Seizures(PUBLIC LIBRARY SCIENCE, 2013-11-19)The process by which the brain transitions into an epileptic seizure is unknown. In this study, we investigated whether the transition to seizure is associated with changes in brain dynamics detectable in the wideband EEG, and whether differences exist across underlying pathologies. Depth electrode ictal EEG recordings from 40 consecutive patients with pharmacoresistant lesional focal epilepsy were low-pass filtered at 500 Hz and sampled at 2,000 Hz. Predefined EEG sections were selected immediately before (immediate preictal), and 30 seconds before the earliest EEG sign suggestive of seizure activity (baseline). Spectral analysis, visual inspection and discrete wavelet transform were used to detect standard (delta, theta, alpha, beta and gamma) and high-frequency bands (ripples and fast ripples). At the group level, each EEG frequency band activity increased significantly from baseline to the immediate preictal section, mostly in a progressive manner and independently of any modification in the state of vigilance. Preictal increases in each frequency band activity were widespread, being observed in the seizure-onset zone and lesional tissue, as well as in remote regions. These changes occurred in all the investigated pathologies (mesial temporal atrophy/sclerosis, local/regional cortical atrophy, and malformations of cortical development), but were more pronounced in mesial temporal atrophy/sclerosis. Our findings indicate that a brain state change with distinctive features, in the form of unidirectional changes across the entire EEG bandwidth, occurs immediately prior to seizure onset. We postulate that these changes might reflect a facilitating state of the brain which enables a susceptible region to generate seizures.
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ItemSedation depth and long-term mortality in mechanically ventilated critically ill adults: a prospective longitudinal multicentre cohort study(SPRINGER, 2013-05)PURPOSE: To ascertain the relationship among early (first 48 h) deep sedation, time to extubation, delirium and long-term mortality. METHODS: We conducted a multicentre prospective longitudinal cohort study in 11 Malaysian hospitals including medical/surgical patients (n = 259) who were sedated and ventilated ≥24 h. Patients were followed from ICU admission up to 28 days in ICU with 4-hourly sedation and daily delirium assessments and 180-day mortality. Deep sedation was defined as Richmond Agitation Sedation Score (RASS) ≤-3. RESULTS: The cohort had a mean (SD) age of 53.1 (15.9) years and APACHE II score of 21.3 (8.2) with hospital and 180-day mortality of 82 (31.7%) and 110/237 (46.4%). Patients were followed for 2,657 ICU days and underwent 13,836 RASS assessments. Midazolam prescription was predominant compared to propofol, given to 241 (93%) versus 72 (28%) patients (P < 0.0001) for 966 (39.6%) versus 183 (7.5%) study days respectively. Deep sedation occurred in (182/257) 71% patients at first assessment and in 159 (61%) patients and 1,658 (59%) of all RASS assessments at 48 h. Multivariable Cox proportional hazard regression analysis adjusting for a priori assigned covariates including sedative agents, diagnosis, age, APACHE II score, operative, elective, vasopressors and dialysis showed that early deep sedation was independently associated with longer time to extubation [hazard ratio (HR) 0.93, 95% confidence interval (CI) 0.89-0.97, P = 0.003], hospital death (HR 1.11, 95% CI 1.05-1.18, P < 0.001) and 180-day mortality (HR 1.09, 95% CI 1.04-1.15, P = 0.002), but not time to delirium (HR 0.98, P = 0.23). Delirium occurred in 114 (44%) of patients. CONCLUSION: Irrespective of sedative choice, early deep sedation was independently associated with delayed extubation and higher mortality, and thus was a potentially modifiable risk in interventional trials.
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ItemTeriflunomide reduces relapses with sequelae and relapses leading to hospitalizations: results from the TOWER study(SPRINGER HEIDELBERG, 2014-09)Teriflunomide is a once-daily oral immunomodulator approved for the treatment of relapsing-remitting multiple sclerosis. This post hoc analysis of the Phase III TOWER study evaluated the effects of teriflunomide treatment on five severe relapse outcomes: relapses with sequelae defined by an increase in Expanded Disability Status Scale (EDSS)/functional system (FS) score (sequelae-EDSS/FS) 30 days post relapse; relapses with sequelae defined by the investigator (sequelae-investigator); relapses leading to hospitalization; relapses treated with intravenous corticosteroids; and intense relapses using the definition of Panitch et al. from the EVIDENCE study based on specified increases in EDSS for severe relapses. Adjusted annualized rates for the five severe relapse outcomes were derived using a Poisson model with robust error variance, with treatment, baseline EDSS strata and region as covariates. Compared with placebo, teriflunomide significantly reduced annualized rates of relapses with sequelae-EDSS/FS [14 mg, 36.6 % (p = 0.0021); 7 mg, 31.3 % (p = 0.0104)] and sequelae-investigator [14 mg only, 53.5 % (p = 0.0004)], relapses leading to hospitalization [14 mg only, 33.6 % (p = 0.0155)], relapses requiring intravenous corticosteroids [14 mg, 35.7 % (p = 0.0002); 7 mg, 21.5 % (p = 0.0337)], and intense relapses [14 mg only, 52.5 % (p = 0.0015)]. Patients treated with teriflunomide 14 mg spent significantly fewer nights in hospital for relapse (p = 0.009) and had lower annualized rates of all hospitalizations (p = 0.030). Taken together, the positive effects of teriflunomide on severe relapses indicate that teriflunomide may reduce relapse-related healthcare costs.