A practical method to simulate realistic reduced-exposure CT images by the addition of computationally generated noise.

Computed tomography (CT) scanning protocols should be optimized to minimize the radiation dose necessary for imaging. The addition of computationally generated noise to the CT images facilitates dose reduction. The objective of this study was to develop a noise addition method that reproduces the complexity of the noise texture present in clinical images with directionality that varies over images according to the underlying anatomy, requiring only Digital Imaging and Communications in Medicine (DICOM) images as input data and commonly available phantoms for calibration. The developed method is based on the estimation of projection data by forward projection from images, the addition of Poisson noise, and the reconstruction of new images. The method was validated by applying it to images acquired from cylindrical and thoracic phantoms using source images with exposures up to 49 mAs and target images between 39 and 5 mAs. 2D noise spectra were derived for regions of interest in the generated low-dose images and compared with those from the scanner-acquired low-dose images. The root mean square difference between the standard deviations of noise was 4%, except for very low exposures in peripheral regions of the cylindrical phantom. The noise spectra from the corresponding regions of interest exhibited remarkable agreement, indicating that the complex nature of the noise was reproduced. A practical method for adding noise to CT images was presented, and the magnitudes of noise and spectral content were validated. This method may be used to optimize CT imaging.

A Method of Correcting for the Effect of Temperature on Low-Contrast Penetration Measurement in Urethane Phantoms.

Urethane-based test objects are routinely used for ultrasound quality assurance because of their durability and robustness. The acoustic properties of these phantoms including speed of sound and attenuation, however, have a strong dependence on temperature. Reliable measurement of low-contrast penetration, which is widely used for ultrasound system quality assurance testing, with these phantoms is therefore problematic. To alleviate this, a correction method was proposed using speed of sound estimated by measuring filament target separation. The method was developed using a range of 17 transducer geometry and frequency combinations across 5 ultrasound systems and validated using a further 5 systems. This was found to reduce the uncertainty of low-contrast penetration measurement from an average 17.6 mm to 4.9 mm over the temperature range 8°C to 32°C. This represents a greater than threefold improvement in precision of low-contrast penetration measurement.

Can a renal nurse assess fluid status using ultrasound on the inferior vena cava? A cross-sectional interrater study.

INTRODUCTION: Ultrasound of the inferior vena cava (IVC-US) has been used to estimate intravascular volume status and fluid removal during a hemodialysis session. Usually, renal nurses rely on other, imprecise methods to determine ultrafiltration. To date, no study has examined whether renal nurses can reliably perform ultrasound for volume assessment and for potential prevention of intradialytic hypotension. This pilot study aimed to determine if a renal nurse could master the skill of performing and correctly interpreting Point of Care Ultrasound on patients receiving hemodialysis. METHODS: After receiving theoretical training and performing 100 training scans, a renal nurse performed 60 ultrasound scans on 10 patients. These were categorized by the nurse into hypovolemic, euvolemic, or hypervolemic through measurement of the maximal diameter and degree of collapse of the IVC. Scans were subsequently assessed for adequacy and quality by two sonologists, who were blinded to each other's and the nurse's results. FINDINGS: The interrater reliability of 60 scans was good, with intraclass correlation 0.79 (95% confidence interval (CI) =0.63-0.87) and with a good interrater agreement for the following estimation of intravascular volume (Cohen's weighted Kappa κw = 0.62), when comparing the nurse to an expert sonographer. DISCUSSION: A renal nurse can reliably perform ultrasound of the IVC in hemodialysis patients, obtaining high quality scans for volume assessment of hemodialysis patients. This novel approach could be more routinely applied by other renal nurses to obtain objective measures of patient volume status in the dialysis setting.

Is Grey Level a Suitable Alternative to Low-Contrast Penetration as a Serial Measure of Sensitivity in Computerised Ultrasound Quality Assurance?

The aim of this study was to test the hypothesis that grey levels are a suitable alternative measure of sensitivity in ultrasound imaging quality assurance, as there are several caveats in the use of penetration depth. In a primary cohort of nine probes, where measurements had been made for 6 to 34 mo, both penetration depth and mean grey level fell below tolerance for six probes; both penetration depth and mean grey level remained within tolerance for three probes. In a secondary cohort where a measurement programme had been in place for a shorter period, grey level and/or penetration depth fell below tolerance in 15 of 66 probes; the sensitivity and specificity of at least 10% loss of grey level in predicting >5% loss in penetration depth were 91% and 93%, respectively. A loss of grey level accompanies a loss of penetration and provides a suitable alternative measure of sensitivity.

Use of ultrasound by registered nurses-a systematic literature review.

BACKGROUND: In Western Australia (WA), most stable patients undergoing haemodialysis receive treatment in a satellite setting where no doctors are on-site during treatment hours, so nurses must make critical decisions about fluid removal. Some patients regularly experience adverse events during dialysis (intradialytic), often due to excessive ultrafiltration goals, with intradialytic hypotension being particularly challenging. Ultrasound of the inferior vena cava has been previously demonstrated being a rapid and non-invasive method for volume assessment on haemodialysis patients, thus could hold valuable information for the treating nurse. AIM: This paper examines the existing literature in regards to the use of ultrasound measurements of the inferior vena cava in patients on haemodialysis for objective assessment of their intravascular volume status by renal nurses. METHOD: A systematic literature review was performed within medical and nursing databases including CINAHL Plus with Full Text, SCOPUS, Web of Science and MEDLINE. RESULTS: Renal nurses are conscious of the significance of intradialytic hypotension and have only limited options for its prevention. Ultrasound of the inferior vena cava could add another objective dimension for intravascular volume assessment and prevention of intradialytic hypotension, but to date renal nurses have not been using this technique. CONCLUSIONS: Ultrasound of the inferior vena cava has the potential to assist in defining the ultrafiltration goal for that particular dialysis session, thus reducing the risk of intradialytic hypotension. Additionally, it has potential to change current renal nursing practice when added to clinical nursing assessment methods. Further studies are required to validate this assessment tool carried out by a renal nurse compared with a skilled ultrasonographer.

Effects of emergency department Care Coordination Team referrals in older people presenting with a fall.

OBJECTIVES: The study aims to describe the characteristics of patients presenting to an ED with a fall and evaluate multidisciplinary Care Coordination Team (CCT) referrals on patient outcomes. METHODS: A single-centred retrospective analysis of electronic data at an adult tertiary hospital was performed using data from 2004 to 2009 of presentations for patients aged 65 years or over with a fall. The primary outcome measure was representation to hospital within 30 days, comparing patients referred to CCT and those not referred. Secondary outcomes were differences in demographic characteristics, mode of arrival, triage score and readmission. RESULTS: The proportion of ED patients presenting with a fall and their mean age is stable over time. From 2006 to 2009, 5162 fallers were referred to CCT in a decreasing trend, but with increased urgency. Statistically significant predictors for being referred to CCT were increasing age, being female, arriving by ambulance, being transferred from a nursing home and higher socioeconomic category. Arrival by ambulance and a history of previous falls were associated with representation and readmission. A decreasing trend from 2006 to 2009 was seen in rate ratios and odds ratios via regression modelling for both representation and readmission in patients referred to CCT. CONCLUSION: Maturing of the CCT is associated with a decrease in representation and readmission rate. Over time, the CCT attended higher urgency patients associated with stable admission rates. These associations were not significant and the clinical effectiveness of ED CCTs requires further examination.

Activation of glial FGFRs is essential in glial migration, proliferation, and survival and in glia-neuron signaling during olfactory system development.

Development of the adult olfactory system of the moth Manduca sexta depends on reciprocal interactions between olfactory receptor neuron (ORN) axons growing in from the periphery and centrally-derived glial cells. Early-arriving ORN axons induce a subset of glial cells to proliferate and migrate to form an axon-sorting zone, in which later-arriving ORN axons will change their axonal neighbors and change their direction of outgrowth in order to travel with like axons to their target areas in the olfactory (antennal) lobe. These newly fasciculated axon bundles will terminate in protoglomeruli, the formation of which induces other glial cells to migrate to surround them. Glial cells do not migrate unless ORN axons are present, axons fail to fasciculate and target correctly without sufficient glial cells, and protoglomeruli are not maintained without a glial surround. We have shown previously that Epidermal Growth Factor receptors and the IgCAMs Neuroglian and Fasciclin II play a role in the ORN responses to glial cells. In the present work, we present evidence for the importance of glial Fibroblast Growth Factor receptors in glial migration, proliferation, and survival in this developing pathway. We also report changes in growth patterns of ORN axons and of the dendrites of olfactory (antennal lobe) neurons following blockade of glial FGFR activation that suggest that glial FGFR activation is important in reciprocal communication between neurons and glial cells.

Analysis of 22,655 presentations with back pain to Perth emergency departments over five years.

BACKGROUND: Back pain is a significant cause of disability in the community, but the impact on Emergency Departments (EDs) has not been formally studied. Patients with back pain often require significant time and resources in the ED. AIMS: To examine the characteristics of patients presenting with back pain to the ED, including final diagnosis, demographics of those attending and temporal distribution of presentations. METHODS: Emergency presentations in the metropolitan area of Perth, Western Australia, for 2000-2004 were searched using a linked database covering all the major hospitals (Emergency Care Hospitalisation and Outcome Study database). All presentations with the triage code for back pain were extracted and analysed. RESULTS: A total of 22,655 presentations with back pain were identified, representing 1.9% of total presentations. Simple muscular or non-specific back pain accounted for only 43.8% of presentations, with other causes such as renal colic and pyelonephritis accounting for the majority. The young (<15 years old) and elderly (>75 years old) were more likely to have non-muscular causes for their back pain. Muscular back pain presentations occurred mostly between 0800 and 1600, with high proportions presenting on the weekends. Patients with simple muscular back pain spent a mean of 4.4 h in the ED, representing a significant outlay of resources. CONCLUSION: Back pain has a significant impact on EDs, and staff should be alert for another pathology presenting as back pain. There is a need for multidisciplinary back pain teams to be available 7 days a week, but only during the day.

Cardiovascular mortality in men with erectile dysfunction: increased risk but not inevitable.

INTRODUCTION: It is unclear whether men with erectile dysfunction (ED) ultimately die of cardiovascular (CV) causes. AIM: This study examined the causes of death in men with ED and their risk of CV death. METHODS: Based on statutory death registrations and hospital morbidity data, the risk of CV death in men with ED in a linked-data study was assessed against the CV mortality risk in a reference male population. MAIN OUTCOME MEASURES: Deaths from CV causes as proportions of all deaths. Age-specific rate, mortality rate ratio (MRR), standardized mortality rate ratio (SMRR), and adjusted hazard ratio (HR). RESULTS: CV mortality was 4.0%. Compared with the reference population, the risk of CV death was higher in men with ED (SMRR 2.2; 95% confidence interval [CI] 1.6, 3.0). Risk of CV mortality was higher in men with CV disease prior to ED (adjusted HR 1.7; 95% CI 1.1, 2.6) or with history of hospital admissions for CV events (adjusted HR 2.2; 95% CI 1.3, 3.8), compared with those without the respective history. MRR was significantly increased in the 40-69 years age group (MRR 4.1; 95% CI 3.2, 5.2). The median time interval between manifestation of ED and CV death was 10.0 years. A greater proportion of deaths from oncological than from CV causes (25.0% vs. 10.8%) occurred within the first 5 years of the manifestation of ED. CONCLUSIONS: Although the risk of CV mortality is greater in men with ED, almost as many men die of oncological as of CV causes, with a higher proportion of oncological deaths occurring sooner subsequent to the first manifestation of ED.

Cell adhesion molecules in context: CAM function depends on the neighborhood.

Cell adhesion molecules (CAMs) are now known to mediate much more than adhesion between cells and between cells and the extracellular matrix. Work by many researchers has illuminated their roles in modulating activation of molecules such as receptor tyrosine kinases, with subsequent effects on cell survival, migration, and process extension. CAMs also are known to serve as substrates for proteases which can create diffusible fragments capable of signaling independently from the CAM. The diversity of interactions is further modulated by membrane rafts, which can co-localize or separate potential signaling partners to affect the likelihood of a given signaling pathway being activated. Given the ever-growing number of known CAMs and the fact that their heterophilic binding in cis or in trans can affect their interactions with other molecules, including membrane-bound receptors, one would predict a wide range of effects attributable to a particular CAM in a particular cell at a particular stage of development. The function(s) of a given CAM must therefore be considered in the context of the history of the cell expressing it and the repertoire of molecules expressed both by that cell and its neighbors.

Direct and glia-mediated effects of GABA on development of central olfactory neurons.

Previously studied for its role in processing olfactory information in the antennal lobe, GABA also may shape development of the olfactory pathway, acting either through or on glial cells. Early in development, the dendrites of GABAergic neurons extend to the glial border that surrounds the nascent olfactory lobe neuropil. These neuropil glia express both GABAA and GABAB receptors, about half of the glia in acute cultures responded to GABA with small outward currents, and about a third responded with small transient increases in intracellular calcium. The neuronal classes that express GABA in vivo, the local interneurons and a subset of projection neurons, also do so in culture. Exposure to GABA in culture increased the size and complexity of local interneurons, but had no effect on glial morphology. The presence of glia alone did not affect neuronal morphology, but in the presence of both glia and GABA, the growth-enhancing effects of GABA on cultured antennal lobe neurons were eliminated. Contact between the glial cells and the neurons was not necessary. Operating in vivo, these antagonistic effects, one direct and one glia mediated, could help to sculpt the densely branched, tufted arbors that are characteristic of neurons innervating olfactory glomeruli.

Paediatric frequent attenders at emergency departments: a linked-data population study.

AIM: To characterise the phenomena of paediatric frequent attenders (FAs) to emergency departments (EDs) in Perth. METHODS: A linked data population study of all children (<15 years) attending Perth hospital EDs between 1 July 2000 and 31 December 2006. FAs attending five or more times annually were assessed for demographic characteristics, mode of arrival, urgency, clinical conditions and disposition by frequency of attendance. RESULTS: Over 6.5 years, 229, 883 children contributed to 378, 068 annualised chains of events (mean 1.5). Most children (98.2%) attended EDs less than five times a year. The more frequently children attended, the more likely they were to be male, younger, self-referred, have respiratory or infectious disorders, and to arrive by ambulance. Characteristics of those attending 0-4 (n= 371 171) and 5-9 (n= 6405) times per year were broadly similar, while those attending 10-19 times per year (n= 461) were more urgent, had a higher frequency of respiratory disease and higher admission rates (all P < 0.001). Those attending more than 20 times a year (n= 31) had serious chronic illness. CONCLUSIONS: Frequent attenders of 5-9 times a year may be no sicker or more in need of hospital services than those who attend less frequently. The preponderance of respiratory and infectious disorders across all FA groups suggests these could be the focus of further research. We advocate a holistic approach to take into account parental expectations, and a systems approach to change ED attendance behaviour.

Localization of a GABA transporter to glial cells in the developing and adult olfactory pathway of the moth Manduca sexta.

Glial cells have several critical roles in the developing and adult olfactory (antennal) lobe of the moth Manduca sexta. Early in development, glial cells occupy discrete regions of the developing olfactory pathway and processes of gamma-aminobutyric acid (GABA)ergic neurons extend into some of these regions. Because GABA is known to have developmental effects in a variety of systems, we explored the possibility that the glial cells express a GABA transporter that could regulate GABA levels to which olfactory neurons and glial cells are exposed. By using an antibody raised against a characterized high-affinity M. sexta GABA transporter with high sequence homology to known mammalian GABA transporters (Mbungu et al. [1995] Arch. Biochem. Biophys. 318:489-497; Umesh and Gill [2002] J. Comp. Neurol. 448:388-398), we found that the GABA transporter is localized to subsets of centrally derived glial cells during metamorphic adult development. The transporter persists into adulthood in a subset of the neuropil-associated glial cells, but its distribution pattern as determined by light-and electron-microscopic-level immunocytochemistry indicates that it could not serve to regulate GABA concentration in the synaptic cleft. Instead, its role is more likely to regulate extracellular GABA levels within the glomerular neuropil. Expression in the sorting zone glial cells disappears after the period of olfactory receptor axon ingrowth, but may be important during ingrowth if GABA regulates axon growth. Glial cells take up GABA, and that uptake can be blocked by L-2,4-diaminobutyric acid (DABA). This is the first molecular evidence that the central glial cell population in this pathway is heterogeneous.

Erectile dysfunction as a predictor for subsequent atherosclerotic cardiovascular events: findings from a linked-data study.

INTRODUCTION: In spite of the mounting interest in the nexus between erectile dysfunction (ED) and cardiovascular (CV) diseases, there is little published information on the role of ED as a predictor for subsequent CV events. AIM: This study aimed to investigate the role of ED as a predictor for atherosclerotic CV events subsequent to the manifestation of ED. Method. The investigation involved the retrospective study of data on a cohort of men with ED linked to hospital morbidity data and death registrations. By using the linked data, the incidence rates of atherosclerotic CV events subsequent to the manifestation of ED were estimated in men with ED and no atherosclerotic CV disease reported prior to the manifestation of ED. The risk of subsequent atherosclerotic CV events in men with ED was assessed by comparing these incidence rates with those in the general male population. MAIN OUTCOME MEASURE: Standardized incidence rate ratio (SIRR), comparing the incidence of atherosclerotic CV events subsequent to the manifestation of ED in a cohort of 1,660 men with ED to the incidence in the general male population. RESULTS: On the basis of hospital admissions and death registrations, men with ED had a statistically significantly higher incidence of atherosclerotic CV events (SIRR 2.2; 95% confidence interval 1.9, 2.4). There were significantly increased incidence rate ratios in all age groups younger than 70 years, with a statistically highly significant downward trend with increase of age (P < 0.0001) across these age groups. Younger age at first manifestation of ED, cigarette smoking, presence of comorbidities and socioeconomic disadvantage were all associated with higher hazard ratios for subsequent atherosclerotic CV events. CONCLUSIONS: The findings show that ED is not only significantly associated with but is also strongly predictive of subsequent atherosclerotic CV events. This is even more striking when ED presents at a younger age.

Short-term risk of adverse outcome is significantly higher in patients returning an abnormal troponin result when tested in the emergency department.

OBJECTIVE: Describe short-term mortality and hospitalization outcomes in patients undergoing troponin testing in Western Australia tertiary public hospital ED. METHODS: Retrospective cohort study of adults presenting to urban tertiary ED between July 2000 and December 2004, and undergoing troponin inhibitory or tropomyosin binding testing. Patient data relating to ED attendance, troponins, hospitalization and death were linked using probabilistic data linkage. Troponin results were dichotomized (normal/abnormal) according to hospitals' cut-offs across various time periods. Presentations undergoing ED troponin testing, provided that it was not within 28 days of a previous discharge involving ED troponin testing, met study inclusion criteria. Logistical regression analyses quantified risk of subsequent hospitalization and death. RESULTS: A total of 119 646 troponin tests were performed during 83 635 ED presentations involving 54 214 patients. For the 73 965 ED presentations meeting the study criteria, 6779 (9.2%) recorded an abnormal peak troponin level and 168 (2.5%) of these presentations were discharged directly from ED. After adjusting for covariates, those discharged directly from ED with abnormal troponin results were significantly more likely to die within 2 days (OR 60.4, 95% CI 31.9-114.2), 7 days (OR 31.2, 95% CI 17.9-54.3) and 28 days (OR 19.4, 95% CI 12.5-30.1) of discharge, compared with those with normal troponin results. Adjusted odds of subsequent hospital admission within 28 days following discharge from ED were 3.3 (95% CI 2.4-4.5) times greater for presentations with abnormal versus normal troponin results. CONCLUSION: An abnormal ED troponin result appears to be associated with increased risk of subsequent hospitalization and death within 28 days of discharge.

Roles of specific membrane lipid domains in EGF receptor activation and cell adhesion molecule stabilization in a developing olfactory system.

BACKGROUND: Reciprocal interactions between glial cells and olfactory receptor neurons (ORNs) cause ORN axons entering the brain to sort, to fasciculate into bundles destined for specific glomeruli, and to form stable protoglomeruli in the developing olfactory system of an experimentally advantageous animal species, the moth Manduca sexta. Epidermal growth factor receptors (EGFRs) and the cell adhesion molecules (IgCAMs) neuroglian and fasciclin II are known to be important players in these processes. METHODOLOGY/PRINCIPAL FINDINGS: We report in situ and cell-culture studies that suggest a role for glycosphingolipid-rich membrane subdomains in neuron-glia interactions. Disruption of these subdomains by the use of methyl-beta-cyclodextrin results in loss of EGFR activation, depletion of fasciclin II in ORN axons, and loss of neuroglian stabilization in the membrane. At the cellular level, disruption leads to aberrant ORN axon trajectories, small antennal lobes, abnormal arrays of olfactory glomerul, and loss of normal glial cell migration. CONCLUSIONS/SIGNIFICANCE: We propose that glycosphingolipid-rich membrane subdomains (possible membrane rafts or platforms) are essential for IgCAM-mediated EGFR activation and for anchoring of neuroglian to the cytoskeleton, both required for normal extension and sorting of ORN axons.

Emergency Department diagnosis of pulmonary embolism is associated with significantly reduced mortality: a linked data population study.

OBJECTIVES: We characterized patients admitted via ED with a principal hospital discharge diagnosis of pulmonary embolism (PE) and compared mortality of those diagnosed in the ED with those diagnosed after admission. METHODS: Patients with a hospital discharge diagnosis ICD 10 I26 presenting to the ED in Perth, Western Australia between 1 July 2000 and 30 December 2006 had records from the Emergency Department Information System linked to the Western Australian Hospital Morbidity Data System and the death registry. RESULTS: Of 2250 patients (mean age 60.4), 1227 (54.5%) were female. Of 1931 patients with an ED diagnosis recorded, 1207 (62.5%) were diagnosed with PE in ED. Of these, 383 (17.0%) had presented to an ED within 28 days previously, 142 (37.1%) with either chest pain or breathing problems, with 207 (54.0%) admitted but not receiving a principal hospital discharge diagnosis of PE. There were 127 (5.6%) in-hospital deaths. Controlling for age and comorbidity with logistic regression, patients diagnosed with PE in ED were less likely to die in hospital, within 7 and 30 days of ED arrival, than those diagnosed after admission (adjusted OR 0.31, 95% CI 0.20-0.47; adjusted OR 0.32, 95% CI 0.19-0.53; adjusted OR 0.30, 95% CI 0.20-0.44; respectively). CONCLUSION: Making the diagnosis of PE in ED was associated with a substantial survival advantage that persisted after hospital discharge.

Use of emergency departments by older people from residential care: a population based study.

OBJECTIVE: to investigate the differences between emergency department (ED) presentations of older people who do and do not live in residential care facilities (RCFs). DESIGN: a population-based retrospective cohort study. ED records linked to ambulance and hospital morbidity records. SETTING: public EDs in Perth, Western Australia. SUBJECTS: all patients 65 years and older who presented to EDs between 1 January 2003 and 31 December 2006 (n = 97,161). MEASUREMENTS: patient demographic and clinical characteristics. Logistic regression was used to model the effect of living in RCFs on the likelihood of a particular ED diagnosis, hospital admission and in-hospital death. RESULTS: the age-sex standardised rate of ED presentation for those living in RCFs was 1.69 times that of community dwellers. Compared to community dwellers, people from RCFs were older (mean age 84.7 years vs. 76.0 years, P < 0.001) and a lower proportion were male (28.7% vs. 46.7%, P < 0.001). Adjusting for age and sex revealed that people from RCFs were more likely to be diagnosed with pneumonia/influenza [odds ratio (OR) 1.94, 95% confidence interval (CI) = 1.72-2.19], urinary tract infections (OR 1.72, 95% CI 1.49-1.98) or hip fractures (OR 1.16, 95% CI 1.03-1.32); less likely to be diagnosed with circulatory system diseases (OR 0.69, 95% CI 0.64-0.75) or neoplasms (OR 0.47, 95% CI 0.31-0.72); more likely to be admitted (OR 1.13, 95% CI 1.06-1.20) and to die in hospital (OR 1.57, 95% CI 1.40-1.75). CONCLUSION: there are different patterns of ED presentations and hospital admissions of older people who do and do not live in RCFs. The appropriateness of these differences is uncertain.

Frequent attenders at emergency departments: a linked-data population study of adult patients.

OBJECTIVES: To examine the characteristics of adult patient attendances to emergency departments (EDs) in Perth hospitals by patients' frequency of attendance. DESIGN, SETTING AND PARTICIPANTS: A linked-data population study of adults (aged > or = 15 years) attending all nine Perth hospital EDs between 1 July 2000 and 31 December 2006. MAIN OUTCOME MEASURES: Proportion of frequent attenders (FAs; those attending five or more times annually); and demographic characteristics, mode of arrival at the ED, disposition (admission, transfer, discharge or death), urgency and clinical conditions by frequency of attendance. RESULTS: There was a mean of 1.5 attendances per individual per year, resulting in 1 583 924 attendances by 663 309 individuals over the 6.5 years of the study. Most patients (97.6%) attended Perth EDs fewer than five times a year. The more frequently patients attended, the more likely they were to be male, middle-aged and late-middle-aged, have self-referred, have mental and behavioural disorders and alcohol intoxication, to not wait to be assessed, and to arrive by ambulance. The groups of patients attending between 5-9 and 10-19 times per year (97.4% of FAs) had more urgent conditions, more circulatory system disease and higher admission rates than all other patients. CONCLUSION: Most FAs at Perth EDs present fewer than 20 times a year and have more serious and urgent illness than other patients, more often requiring inpatient services. A very small minority of patients (around 100 patients/year) attends 20 or more times a year, many with mental and behavioural disorders and alcohol intoxication not requiring hospital admission.

Activation of epidermal growth factor receptor mediates receptor axon sorting and extension in the developing olfactory system of the moth Manduca sexta.

During development of the adult olfactory system of the moth Manduca sexta, olfactory receptor neurons extend axons from the olfactory epithelium in the antenna into the brain. As they arrive at the brain, interactions with centrally derived glial cells cause axons to sort and fasciculate with other axons destined to innervate the same glomeruli. Here we report studies indicating that activation of the epidermal growth factor receptor (EGFR) is involved in axon ingrowth and targeting. Blocking the EGFR kinase domain pharmacologically leads to stalling of many axons in the sorting zone and nerve layer as well as abnormal axonal fasciculation in the sorting zone. We also find that neuroglian, an IgCAM known to activate the EGFR through homophilic interactions in other systems, is transiently present on olfactory receptor neuron axons and on glia during the critical stages of the sorting process. The neuroglian is resistant to extraction with Triton X-100 in the sorting zone and nerve layer, possibly indicating its stabilization by homophilic binding in these regions. Our results suggest a mechanism whereby neuroglian molecules on axons and possibly sorting zone glia bind homophilically, leading to activation of EGFRs, with subsequent effects on axon sorting, pathfinding, and extension, and glomerulus development.