Melbourne Medical School Collected Works - Research Publications
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ItemTwo Distinct Populations of Exosomes Are Released from LIM1863 Colon Carcinoma Cell-derived Organoids(ELSEVIER, 2013-03-01)Exosomes are naturally occurring biological nanomembranous vesicles (∼40 to 100 nm) of endocytic origin that are released from diverse cell types into the extracellular space. They have pleiotropic functions such as antigen presentation and intercellular transfer of protein cargo, mRNA, microRNA, lipids, and oncogenic potential. Here we describe the isolation, via sequential immunocapture using anti-A33- and anti-EpCAM-coupled magnetic beads, of two distinct populations of exosomes released from organoids derived from human colon carcinoma cell line LIM1863. The exosome populations (A33-Exos and EpCAM-Exos) could not be distinguished via electron microscopy and contained stereotypical exosome markers such as TSG101, Alix, and HSP70. The salient finding of this study, revealed via gel-based LC-MS/MS, was the exclusive identification in EpCAM-Exos of the classical apical trafficking molecules CD63 (LAMP3), mucin 13 and the apical intestinal enzyme sucrase isomaltase and increased expression of dipeptidyl peptidase IV and the apically restricted pentaspan membrane glycoprotein prominin 1. In contrast, the A33-Exos preparation was enriched with basolateral trafficking molecules such as early endosome antigen 1, the Golgi membrane protein ADP-ribosylation factor, and clathrin. Our observations are consistent with EpCAM- and A33-Exos being released from the apical and basolateral surfaces, respectively, and the EpCAM-Exos proteome profile with widely published stereotypical exosomes. A proteome analysis of LIM1863-derived shed microvesicles (sMVs) was also performed in order to clearly distinguish A33- and EpCAM-Exos from sMVs. Intriguingly, several members of the MHC class I family of antigen presentation molecules were exclusively observed in A33-Exos, whereas neither MHC class I nor MHC class II molecules were observed via MS in EpCAM-Exos. Additionally, we report for the first time in any extracellular vesicle study the colocalization of EpCAM, claudin-7, and CD44 in EpCAM-Exos. Given that these molecules are known to complex together to promote tumor progression, further characterization of exosome subpopulations will enable a deeper understanding of their possible role in regulation of the tumor microenvironment.
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ItemA new technique for assessing arterial pressure wave forms and central pressure with tissue Doppler.(Springer Science and Business Media LLC, 2007-01-31)BACKGROUND: Non-invasive assessment of arterial pressure wave forms using applanation tonometry of the radial or carotid arteries can be technically challenging and has not found wide clinical application. 2D imaging of the common carotid arteries is routinely used and we sought to determine whether arterial waveform measurements could be derived from tissue Doppler imaging (TDI) of the carotid artery. METHODS: We studied 91 subjects (52 men, age 52 +/- 14 years) with and without cardiovascular disease. Tonometry was performed on the carotid artery simultaneously with pulsed wave Doppler of the LVOT and acquired digitally. Longitudinal 2D images of the common carotid artery with and without TDI were also acquired digitally and both TDI and tonometry were calibrated using mean and diastolic cuff pressure and analysed off line. RESULTS: Correlation between central pressure by TDI and tonometry was excellent for maximum pressure (r = 0.97, p < 0.0001). The mean differences between central pressures derived by TDI and tonometry were minimal (systolic 5.36 +/- 5.5 mmHg; diastolic 1.2 +/- 1.2 mmHg). CONCLUSION: Imaging of the common carotid artery motion with tissue Doppler may permit acquisition of a waveform analogous to that from tonometry. This method may simplify estimation of central arterial pressure and calculation of total arterial compliance.
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ItemBaseline characteristics of patients in the Reduction of Events with Darbepoetin alfa in Heart Failure trial (RED-HF).(Wiley, 2013-03)AIMS: This report describes the baseline characteristics of patients in the Reduction of Events with Darbepoetin alfa in Heart Failure trial (RED-HF) which is testing the hypothesis that anaemia correction with darbepoetin alfa will reduce the composite endpoint of death from any cause or hospital admission for worsening heart failure, and improve other outcomes. METHODS AND RESULTS: Key demographic, clinical, and laboratory findings, along with baseline treatment, are reported and compared with those of patients in other recent clinical trials in heart failure. Compared with other recent trials, RED-HF enrolled more elderly [mean age 70 (SD 11.4) years], female (41%), and black (9%) patients. RED-HF patients more often had diabetes (46%) and renal impairment (72% had an estimated glomerular filtration rate < 60 mL/min/1.73 m2). Patients in RED-HF had heart failure of longer duration [5.3 (5.4) years], worse NYHA class (35% II, 63% III, and 2% IV), and more signs of congestion. Mean EF was 30% (6.8%). RED-HF patients were well treated at randomization, and pharmacological therapy at baseline was broadly similar to that of other recent trials, taking account of study-specific inclusion/exclusion criteria. Median (interquartile range) haemoglobin at baseline was 112 (106-117) g/L. CONCLUSION: The anaemic patients enrolled in RED-HF were older, moderately to markedly symptomatic, and had extensive co-morbidity.
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ItemWhat Limits Cardiac Performance during Exercise in Normal Subjects and in Healthy Fontan Patients?(HINDAWI LTD, 2010-01-01)Exercise is an important determinant of health but is significantly reduced in the patient with a univentricular circulation. Normal exercise physiology mandates an increase in pulmonary artery pressures which places an increased work demand on the right ventricle (RV). In a biventricular circulation with pathological increases in pulmonary vascular resistance and/or reductions in RV function, exercise-induced augmentation of cardiac output is limited. Left ventricular preload reserve is dependent upon flow through the pulmonary circulation and this requires adequate RV performance. In the Fontan patient, the reasons for exercise intolerance are complex. In those patients with myocardial dysfunction or other pathologies of the circulatory components, it is likely that these abnormalities serve as a limitation to cardiac performance during exercise. However, in the healthy Fontan patient, it may be the absence of a sub-pulmonary pump which limits normal increases in pulmonary pressures, trans-pulmonary flow requirements and cardiac output. If so, performance will be exquisitely dependent on pulmonary vascular resistance. This provides a potential explanation as to why pulmonary vasodilators may improve exercise tolerance. As has recently been demonstrated, these agents may offer an important new treatment strategy which directly addresses the physiological limitations in the Fontan patient.
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ItemUse and Limitations of E/e' to Assess Left Ventricular Filling Pressure by Echocardiography.(Korean Society of Echocardiography, 2011-12)Measurement of left ventricular (LV) filling pressure is useful in decision making and prediction of outcomes in various cardiovascular diseases. Invasive cardiac catheterization has been the gold standard in LV filling pressure measurement, but carries the risk of complications and has a similar predictive value for clinical outcomes compared with non-invasive LV filling pressure estimation by echocardiography. A variety of echocardiographic measurement methods have been suggested to estimate LV filling pressure. The most frequently used method for this purpose is the ratio between early mitral inflow velocity and mitral annular early diastolic velocity (E/e'), which has become central in the guidelines for diastolic evaluation. This review will discuss the use the E/e' ratio in prediction of LV filling pressure and its potential pitfalls.
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ItemTime from symptoms to definitive diagnosis of idiopathic pulmonary arterial hypertension: The delay study(SAGE PUBLICATIONS INC, 2013-01-01)Survival rates for patients with idiopathic pulmonary arterial hypertension (IPAH) have improved with the introduction of PAH-specific therapies. However, the time between patient-reported onset of symptoms and a definitive diagnosis of IPAH is consistently delayed. We conducted a retrospective, multi-center, descriptive investigation in order to (a) understand what factors contribute to persistent diagnostic delays, and (b) examine the time from initial symptom onset to a definitive diagnosis of IPAH. Between January 2007 and December 2008, we enrolled consecutively diagnosed adults with IPAH from four tertiary referral centers in Australia. Screening of patient records and "one-on-one" interviews were used to determine the time from patient-described initial symptoms to a diagnosis of IPAH, confirmed by right heart catheterization (RHC). Thirty-two participants (69% female) were studied. Mean age at symptom onset was 56 ± 16.4 years and 96% reported exertional dyspnea. Mean time from symptom onset to diagnosis was 47 ± 34 months with patients subsequently aged 60 ± 17.3 years. Patients reported 5.3 ± 3.8 GP visits and 3.0 ± 2.1 specialist reviews before being seen at a pulmonary hypertension (PH) center. Advanced age, number of general practitioner (GP) visits, heart rate, and systolic blood pressure at the time of diagnosis were significantly associated with the observed delay. We found a significant delay of 3.9 years from symptom onset to a diagnosis of IPAH in Australia. Exertional dyspnea is the most common presenting symptom. Current practice within Australia does not appear to have the specific capacity for timely, multi-factorial evaluation of breathlessness and potential IPAH.
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ItemWomen Versus Men with Chronic Atrial Fibrillation: Insights from the Standard Versus Atrial Fibrillation spEcific managemenT studY (SAFETY)(PUBLIC LIBRARY SCIENCE, 2013-05-29)BACKGROUND: Gender-based clinical differences are increasingly being identified as having significant influence on the outcomes of patients with cardiovascular disease (CVD), including atrial fibrillation (AF). OBJECTIVE: To perform detailed clinical phenotyping on a cohort of hospitalised patients with chronic forms of AF to understand if gender-based differences exist in the clinical presentation, thrombo-embolic risk and therapeutic management of high risk patients hospitalised with chronic AF. METHODS: We are undertaking the Standard versus Atrial Fibrillation spEcific managemenT studY (SAFETY) - a multi-centre, randomised controlled trial of an AF-specific management intervention versus usual care. Extensive baseline profiling of recruited patients was undertaken to identify gender-specific differences for risk delineation. RESULTS: We screened 2,438 patients with AF and recruited 335 into SAFETY. Of these, 48.1% were women who were, on average, 5 years older than their male counterparts. Women and men displayed divergent antecedent profiles, with women having a higher thrombo-embolic risk but being prescribed similar treatment regimens. More women than men presented to hospital with co-morbid thyroid dysfunction, depression, renal impairment and obesity. In contrast, more men presented with coronary artery disease (CAD) and/or chronic obstructive pulmonary disease (COPD). Even when data was age-adjusted, women were more likely to live alone (odds ratio [OR] 2.33; 95% confidence interval [CI] 1.47 to 3.69), have non-tertiary education (OR 2.69; 95% CI 1.61 to 4.48) and be symptomatic (OR 1.93; 95% CI 1.06 to 3.52). CONCLUSION: Health care providers should be cognisant of gender-specific differences in an attempt to individualise and, hence, optimise the management of patients with chronic AF and reduce potential morbidity and mortality.
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ItemAssessing cardiovascular risk in regional areas: the Healthy Hearts - Beyond City Limits program(BMC, 2012-09-03)BACKGROUND: Cardiovascular disease (CVD) is more prevalent in regional and remote Australia compared to metropolitan areas. The aim of Healthy Hearts was to determine age and sex specific CVD risk factor levels and the potential value of national risk clinics. METHODS: Healthy Hearts was an observational research study conducted in four purposefully selected higher risk communities in regional Victoria, Australia. The main outcome measures were the proportion of participants with CVD risk factors with group comparisons to determine the adjusted likelihood of elevated risk factor levels. Trained personnel used a standardized protocol over four weeks per community to measure CVD risk factor levels, estimate absolute CVD risk and provide feedback and advice. RESULTS: A total of 2125 self-selected participants were assessed (mean age 58 ± 15 years, 57% women). Overall, CVD risk factors were highly prevalent. More men than women had ≥ 2 modifiable CVD risk factors (76% vs. 68%, p < .001), pre-existing CVD (20 vs. 15%, p < .01) and a major ECG abnormality requiring follow-up (15% vs. 7%, p < .001) . Less men reported depressive symptoms compared to women (28% vs. 22%, p < .01). A higher proportion of women were obese (adjusted OR 1.36, 95% CI 1.13 to 1.63), and physically inactive (adjusted OR 1.32, 95% CI 1.07 to 1.63). CONCLUSIONS: High CVD risk factor levels were confirmed for regional Victoria. Close engagement with individuals and communities provides scope for the application of regional risk management clinics to reduce the burden of CVD risk in regional Australia.
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ItemThe 12-lead ECG in peripartum cardiomyopathy(CLINICS CARDIVE PUBL PTY LTD, 2012-07-01)BACKGROUND: The value of the 12-lead electrocardiogram (ECG) to provide prognostic information in the deadly and disabling syndrome peripartum cardiomyopathy (PPCM) is unknown. AIMS: To determine the prevalence of major and minor ECG abnormalities in PPCM patients at the time of diagnosis, and to establish whether there are ECG correlates of persistent left ventricular dysfunction and/or clinical stability at six months of follow up, where available. METHODS: Twelve-lead ECGs were performed at the point of diagnosis on 78 consecutive women presenting with PPCM to two tertiary centres in South Africa and 44 cases (56%) at the six-month follow up. Blinded Minnesota coding identified major ECG abnormalities and minor ECG changes. RESULTS: The cohort mainly comprised young women of black African ancestry (90%) [mean age 29 ± 7 years and median body mass index 24.3 (IQR: 22.7-27.5) kg/m(2)]. The majority of cases (n = 70; 90%) presented in sinus rhythm (mean heart rate 100 ± 21 beats/min). At baseline, at least one ECG Abnormality/variant was detected in 96% of cases. Major ECG abnormalities and minor changes were detected in 49% (95% CI: 37-60%) and 62% (95% CI: 51-74%) of cases, respectively; the most common being T-wave changes (59%), p-wave abnormality (29%) and QRS-axis deviation (25%). Of the 44 cases (56%) reviewed at six months, normalisation of the 12-lead ECG occurred in 25%; the most labile ECG features being heart rate (mean reduction of 27 beats/min; p < 0.001) and abnormal QRS axis (36 vs 14%; p = 0.014). On an adjusted basis, major T-wave abnormalities on the baseline 12-lead ECG were associated with lower left ventricular ejection fraction (LVEF) at baseline (average of -9%, 95% CI: -1 to -16; p = 0.03) and at six months (-12%; 95% CI: -4 to -24; p = 0.006). Similarly, baseline ST-segment elevation was also associated with lower LVEF at six months (-25%; 95% CI: -0.7 to -50; p = 0.04). CONCLUSIONS: In this unique study, we found that almost all women suffering from PPCM had an 'abnormal' 12-lead ECG. Pending more definitive studies, the ECG appears to be a useful adjunctive tool in both screening and prognostication in resource-poor settings.
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ItemImpact of a pharmacist-prepared interim residential care medication administration chart on gaps in continuity of medication management after discharge from hospital to residential care: a prospective pre- and post-intervention study (MedGap Study).(BMJ, 2012)OBJECTIVES: To test the impact of a hospital pharmacist-prepared interim residential care medication administration chart (IRCMAC) on medication administration errors and use of locum medical services after discharge from hospital to residential care. DESIGN: Prospective pre-intervention and post-intervention study. SETTING: One major acute care hospital and one subacute aged-care hospital; 128 residential care facilities (RCF) in Victoria, Australia. PARTICIPANTS: 428 patients (median age 84 years, IQR 79-88) discharged to a RCF from an inpatient ward over two 12-week periods. INTERVENTION: Seven-day IRCMAC auto-populated with patient and medication data from the hospitals' pharmacy dispensing software, completed and signed by a hospital pharmacist and sent with the patient to the RCF. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary end points were the proportion of patients with one or more missed or significantly delayed (>50% of prescribed dose interval) medication doses, and the proportion of patients whose RCF medication chart was written by a locum doctor, in the 24 h after discharge. Secondary end points included RCF staff and general practitioners' opinions about the IRCMAC. RESULTS: The number of patients who experienced one or more missed or delayed doses fell from 37/202 (18.3%) to 6/226 (2.7%) (difference in percentages 15.6%, 95% CI 9.5% to 21.9%, p<0.001). The number of patients whose RCF medication chart was written by a locum doctor fell from 66/202 (32.7%) to 25/226 (11.1%) (difference in percentages 21.6%, 95% CI 13.5% to 29.7%, p<0.001). For 189/226 (83.6%) discharges, RCF staff reported that the IRCMAC improved continuity of care; 31/35 (88.6%) general practitioners said that the IRCMAC reduced the urgency for them to attend the RCF and 35/35 (100%) said that IRCMACs should be provided for all patients discharged to a RCF. CONCLUSIONS: A hospital pharmacist-prepared IRCMAC significantly reduced medication errors and use of locum medical services after discharge from hospital to residential care.