Extending the diabetic retinopathy screening intervals in Singapore: methodology and preliminary findings of a cohort study

BACKGROUND

The Diabetic Retinopathy Extended Screening Study (DRESS) aims to develop and validate a new DR/diabetic macular edema (DME) risk stratification model in patients with Type 2 diabetes (DM) to identify low-risk groups who can be safely assigned to biennial or triennial screening intervals. We describe the study methodology, participants' baseline characteristics, and preliminary DR progression rates at the first annual follow-up.

METHODS

DRESS is a 3-year ongoing longitudinal study of patients with T2DM and no or mild non-proliferative DR (NPDR, non-referable) who underwent teleophthalmic screening under the Singapore integrated Diabetic Retinopathy Programme (SiDRP) at four SingHealth Polyclinics. Patients with referable DR/DME (> mild NPDR) or ungradable fundus images were excluded. Sociodemographic, lifestyle, medical and clinical information was obtained from medical records and interviewer-administered questionnaires at baseline. These data are extracted from medical records at 12, 24 and 36 months post-enrollment. Baseline descriptive characteristics stratified by DR severity at baseline and rates of progression to referable DR at 12-month follow-up were calculated.

RESULTS

Of 5,840 eligible patients, 78.3% (n = 4,570, median [interquartile range [IQR] age 61.0 [55-67] years; 54.7% male; 68.0% Chinese) completed the baseline assessment. At baseline, 97.4% and 2.6% had none and mild NPDR (worse eye), respectively. Most participants had hypertension (79.2%) and dyslipidemia (92.8%); and almost half were obese (43.4%, BMI ≥ 27.5 kg/m2). Participants without DR (vs mild DR) reported shorter DM duration, and had lower haemoglobin A1c, triglycerides and urine albumin/creatinine ratio (all p < 0.05). To date, we have extracted 41.8% (n = 1909) of the 12-month follow-up data. Of these, 99.7% (n = 1,904) did not progress to referable DR. Those who progressed to referable DR status (0.3%) had no DR at baseline.

CONCLUSIONS

In our prospective study of patients with T2DM and non-referable DR attending polyclinics, we found extremely low annual DR progression rates. These preliminary results suggest that extending screening intervals beyond 12 months may be viable and safe for most participants, although our 3-year follow up data are needed to substantiate this claim and develop the risk stratification model to identify low-risk patients with T2DM who can be assigned biennial or triennial screening intervals.

Chest computed tomography analysis of lung sparing morphology: differentiation of COVID-19 pneumonia from influenza pneumonia and bacterial pneumonia using the arched bridge and vacuole signs

INTRODUCTION

This study evaluated the arched bridge and vacuole signs, which constitute morphological patterns of lung sparing in coronavirus disease 2019 (COVID-19), then examined whether these signs could be used to differentiate COVID-19 pneumonia from influenza pneumonia or bacterial pneumonia.

METHODS

In total, 187 patients were included: 66 patients with COVID-19 pneumonia, 50 patients with influenza pneumonia and positive computed tomography findings, and 71 patients with bacterial pneumonia and positive computed tomography findings. Images were independently reviewed by two radiologists. The incidences of the arched bridge sign and/or vacuole sign were compared among the COVID-19 pneumonia, influenza pneumonia, and bacterial pneumonia groups.

RESULTS

The arched bridge sign was much more common among patients with COVID-19 pneumonia (42/66, 63.6%) than among patients with influenza pneumonia (4/50, 8.0%; P<0.001) or bacterial pneumonia (4/71, 5.6%; P<0.001). The vacuole sign was also much more common among patients with COVID-19 pneumonia (14/66, 21.2%) than among patients with influenza pneumonia (1/50, 2.0%; P=0.005) or bacterial pneumonia (1/71, 1.4%; P<0.001). The signs occurred together in 11 (16.7%) patients with COVID-19 pneumonia, but they did not occur together in patients with influenza pneumonia or bacterial pneumonia. The arched bridge and vacuole signs predicted COVID-19 pneumonia with respective specificities of 93.4% and 98.4%.

CONCLUSION

The arched bridge and vacuole signs are much more common in patients with COVID-19 pneumonia and can help differentiate COVID-19 pneumonia from influenza and bacterial pneumonia.

Lower risk of gout in sodium glucose cotransporter 2 (SGLT2) inhibitors versus dipeptidyl peptidase-4 (DPP4) inhibitors in type-2 diabetes patients: a propensity score-matched study

Background

The effects of sodium-glucose cotransporter 2 inhibitors (SGLT2I) versus dipeptidyl peptidase-4 inhibitors (DPP4I) on the risk of new gout diagnosis have not been explored. This study aims to compare the effects of SGLT2I against DPP4I on gout risks in a Chinese population.

Methods

This was a retrospective population-based cohort study of patients with type-2 diabetes mellitus treated with SGLT2I or DPP4I between January 1st, 2015 and December 31st, 2020 in Hong Kong. The study outcomes are new-onset gout and all-cause mortality. Propensity score matching (1:1 ratio) between SGLT2I and DPP4I was performed. Univariable and multivariable Cox regression analysis models were conducted. Competing risks models and multiple approaches based on the propensity score were applied.

Patients

This study included 60996 patients (median age: 62.3 years old, 54.96% males; SGLTI group: n=21690; DPP4I group: n=39306).

Results

In the matched cohort, 1096 developed gout (IR: 2.52%) and 2195 died (IR: 5.05%). Univariable Cox regression showed that SGLT2I use was associated with lower risks of new diagnosis of gout (hazard ratio [HR]: 0.34; 95% confidence interval [CI]: 0.30–0.39; P-value&lt;0.0001) and all-cause mortality (HR: 0.35; 95% CI: 0.32–0.39; P-value&lt;0.0001) compared to DPP4I. The associated remained for both new diagnosis of gout (HR: 0.46; 95% CI: 0.37–0.57; P-value&lt;0.0001) and all-cause mortality (HR: 0.38; 95% CI: 0.33–0.44; P-value&lt;0.0001) after adjusting for significant demographics, past comorbidities, and non-SGLT2I/DPP4I medications. The risks of gout were lowered in each types of SGLT2I. The results were consistent on competing risk and other propensity score approaches analyses.

Conclusions

SGLT2I use was associated with lower risks of new gout diagnosis compared to DPP4I use.

Funding Acknowledgement

Type of funding sources: None.

Predictive value of neutrophil-to-lymphocyte ratio for atrial fibrillation and stroke in type 2 diabetes mellitus: a population-based cohort study

Introduction

Neutrophil-to-lymphocyte ratio (NLR) is a routinely available biomarker that reflects systemic inflammation. The study evaluated the predictive value of NLR for ischemic stroke and atrial fibrillation (AF) in patients with type 2 diabetes mellitus.

Methods

This was a population-based cohort study of patients with type 2 diabetes mellitus and complete blood count tests at baseline between January 1st, 2009 to December 31st, 2009 at government-funded hospitals/clinics in Hong Kong. Follow-up was until December 31st, 2019 or death.

Results

A total of 85351 patients (age=67.6±13.2 years old, male=48.8%, follow-up=3101±1441 days) were included. Univariable Cox regression found that increased NLR at quartiles 2, 3 and 4 was significantly associated with higher risks of new onset ischemic stroke (HR: 1.28 [1.20–1.37], P&lt;0.001, HR: 1.41 [1.32–1.51], P&lt;0.001 and HR: 1.38 [1.29–1.47], P&lt;0.001) and AF (hazard ratio [HR]: 1.09 [1.02–1.17], P&lt;0.015; HR: 1.28 [1.20–1.37], P&lt;0.001; HR: 1.39 [1.31–1.49], P&lt;0.001) compared to quartile 1. On multivariable analysis, NLR remained a significant predictor of ischemic stroke risk for quartiles 2 and 3 (quartile 2: HR: 1.14 [1.05, 1.22], p=0.001; quartile 3: HR: 1.14 [1.06, 1.23], p&lt;0.001) but not quartile 4 (HR: 1.08 [0.994, 1.17], p=0.070). By contrast, NLR was not predictive of AF after adjusting for confounders (quartile 2: HR: 0.966 [0.874, 1.07], p=0.499; quartile 3: HR: 0.978 [0.884, 1.08], p=0.661; quartile 4: HR: 1.05 [0.935, 1.16], p=0.462).

Conclusion

NLR is a significant predictor of new onset ischaemic stroke but not AF after adjusting for significant confounders.

Funding Acknowledgement

Type of funding sources: None.

Age-Related Performance in Using a Fully Immersive and Automated Virtual Reality System to Assess Cognitive Function

Introduction

Cognition generally declines gradually over time due to progressive degeneration of the brain, leading to dementia and eventual loss of independent functions. The rate of regression varies among the six cognitive domains (perceptual motor, executive function, complex attention, learning and memory, social cognition and language). Current modality of cognitive assessment using neuropsychological paper-and-pencil screening tools for cognitive impairment such as the Montreal Cognitive Assessment (MoCA) has limitations and is influenced by age. Virtual reality (VR) is considered as a potential alternative tool to assess cognition. A novel, fully immersive automated VR system (Cognitive Assessment using Virtual Reality, CAVIRE) has been developed to assess the six cognitive domains. As cognition is associated with age, VR performance is postulated to vary with age using this system.

Aims

This is a feasibility study to evaluate the VR performance of cognitively healthy adults aged between 35 and 74 years old, based on the performance score and completion time using the CAVIRE system.

Methods

Conducted in a public primary care clinic in Singapore, 25 multi-ethnic Asian adults were recruited in each of the four age groups in years: (1) 35–44; (2) 45–54; (3) 55–64, and (4) 65–74. The eligibility criteria included a MoCA score of 26 or higher to reflect normal cognition and understanding English instructions. They completed common daily activities ranging from brushing teething to shopping, across 13 VR segments. Their performances scores and completion time were automatically computed by the CAVIRE system. These VR performance indices were compared across the four age groups using one-way ANOVA, F-test of the hypothesis, followed by pair-wise comparisons in the event of a significant F-test (p < 0.05).

Results

One participant dropped out from Group 1. The demographic characteristics of 99 participants were similar across the 4 age groups. Overall, younger participants in Groups 1 and 2 attained higher VR performance scores and shorter completion time, compared to those in Groups 3 and 4, in all six cognitive domains (all p < 0.05).

Conclusion

The CAVIRE VR performance scores and completion time significantly differ between the younger and older Asian participants with normal cognition. Enhancements to the system are needed to establish the age-group specific normal performance indices.

Programmed Cell Death 1 (PD-1) and Programmed Cell Death Ligand 1 (PD-L1) inhibitors and adverse cardiovascular events: a population-based study

Funding Acknowledgements

Type of funding sources: None.

OnBehalf

Cardiovascular Analytics Group

Background

Programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors are major classes of immune checkpoint inhibitors that are increasingly used for cancer treatment. However, they are associated with adverse cardiovascular events.

Purpose

To evaluate the cardiotoxicity of PD-1 and PD-L1 inhibitors, the present study aims to examine the incidence of new-onset cardiac complications in patients receiving PD-1 or PD-L1 inhibitors.

Methods

Patients receiving PD-1 or PD-L1 inhibitors since their launch up to December 31st, 2019 without pre-existing cardiac complications were included. Patient data were obtained using a territory-wide electronic health record database. The primary outcome was a composite of incident heart failure (HF), acute myocardial infarction (AMI), atrial fibrillation (AF) or atrial flutter followed up to August 31st, 2020. Propensity score matching between PD-L1 and PD-1 inhibitor use with a 1:1 ratio for patient demographics and comorbidities was performed.

Results

A total of 1925 patients were included. Over a median follow-up of 136 days (interquartile range [IQR]: 42-279), 318 (16.51%) patients met the primary outcome after PD-1/PD-L1 treatment: 242 (incidence rate [IR]: 12.57%) with HF, 38 (IR: 1.97%) with AMI, 53 (IR: 2.75%) with AF, 6 (IR: 0.31%) with atrial flutter. Compared with PD-1 inhibitor treatment, PD-L1 inhibitor treatment was significantly associated with a lower risk of composite outcome after matching (HR: 0.78, 95% CI: [0.62-0.99], P value = 0.0417). Patients who developed cardiovascular complications had shorter average readmission intervals and more hospitalization episodes after treatment with PD-1/PD-L1 inhibitors both before and after matching (P value &lt; 0.0001).

Conclusions

Compared with PD-1 inhibitor users, PD-L1 inhibitor users had a significantly lower risk of new-onset composite cardiovascular complications. Abstract Figure. Kaplan-Meier survival curve

Clustering analysis based on automated electrocardiographic measurements to identify prognostically distinct phenotypes in patients hospitalized for heart failure: a retrospective cohort study

Funding Acknowledgements

Type of funding sources: None.

Background

Heart failure (HF) is a heterogeneous disease with complex structural and electrophysiological derangements of the heart. Attempts to classify HF from the electrophysiological perspective are lacking.

Purpose

To use electrocardiographic (ECG) data for phenotypic classification of patients with HF.

Methods

In this retrospective cohort study, all adult patients hospitalized for HF during 2010-2016 at a tertiary center were included. Automated measurements of the first ECG obtained during the index admission were recorded. K-means clustering using premorbid conditions and selected ECG measurements were used to classify the cohort into four mutually exclusive clusters. The primary (all-cause and cardiovascular mortality) and secondary (ventricular arrhythmia (VA)) outcomes were compared between clusters using Cox regression analysis.

Results

In total, 2849 patients (1363 males, age 75.1 ± 13.4 years) were included. Over a mean follow-up period of 5.37 ± 4.10 years, all-cause and cardiovascular mortality occurred in 2071 (72.7%) and 600 (21.1%) patients respectively, while VA occurred in 110 patients (3.9%). Cluster 1 was characterised by a low heart rate and low ventricular activation time (VAT). Cluster 2 was characterised by old age, low absolute QRS area, and high QTc and QT dispersion. Cluster 3 was characterised by young age, and left ventricular hypertrophy (LVH), and few had history of VA. Cluster 4 was characterised by wide QRS, hypertension, ischaemic heart disease, high VAT, and high absolute T wave area. Cluster 4 had the highest and cluster 1 the lowest risks of all-cause (hazard ratio (HR) 2.96 [1.09, 1.50], p = 0.003; Figure A) and cardiovascular mortality (HR 2.90 [1.15, 2.11], p = 0.004; Figure B). Meanwhile, cluster 2 had the highest risk of VA (HR 2.23 [1.09, 3.85], p = 0.025; Figure C) while clusters 1 and 3 similarly had the lowest risks.

Conclusion

HF presents with clinically and electrophysiologically distinct phenotypes. Clustering analysis is useful in identifying HF phenotypes which are prognostically significant. Abstract Figures A, B, and C

Comparison of Time Taken to Assess Cognitive Function Using a Fully Immersive and Automated Virtual Reality System vs. the Montreal Cognitive Assessment

Introduction: Dementia is increasingly prevalent globally. Existing questionnaire-based cognitive assessment tools may not comprehensively assess cognitive function and real-time task-performance across all cognitive domains. CAVIRE (Cognitive Assessment by VIrtual REality), a fully immersive virtual reality system incorporating automated audio-visual instructions and a scoring matrix was developed to assess the six cognitive domains, with potential to maintain consistency in execution of the testing environment and possibly time-saving in busy primary care practice. Aims: This is a feasibility study to compare the completion times of the questionnaire-based Montreal Cognitive Assessment (MoCA) and the CAVIRE in cognitively-healthy Asian adults aged between 35 and 74 years, overall, and in and across each 10-year age group (35-44; 45-54; 55-64; 65-74). Methods: A total of 100 participants with a MoCA score of 26 or more were recruited equally into the four 10-year age groups at a primary care clinic in Singapore. Completion time for the MoCA assessment for each participant was recorded. They were assessed using the CAVIRE, comprising 13 segments featuring common everyday activities assessing all six cognitive domains, and the completion time was also recorded through the embedded automated scoring and timing framework. Results: Completion time for CAVIRE as compared to MoCA was significantly (p < 0.01) shorter, overall (mean difference: 74.9 (SD) seconds) and in each age group. Younger, vs. older, participants completed both the MoCA and CAVIRE tasks in a shorter time. There was a greater variability in the completion time for the MoCA, most markedly in the oldest group, whereas completion time was less variable for the CAVIRE tasks in all age groups, with most consistency in the 45-54 year-age group. Conclusion: We demonstrate almost equivalent completion times for a VR and a questionnaire-based cognition assessment, with inter-age group variation in VR completion time synonymous to that in conventional screening methods. The CAVIRE has the potential to be an alternative screening modality for cognition in the primary care setting.

Paediatric/young versus adult patients with congenital long QT syndrome or catecholaminergic polymorphic ventricular tachycardia

Introduction

Congenital long QT syndrome (LQTS) and catecholaminergic ventricular tachycardia (CPVT) are less prevalent cardiac ion channelopathies than Brugada syndrome in Asia. The present study compared paediatric/young and adult patients with these conditions.

Method

This was a territory-wide retrospective cohort study of consecutive patients diagnosed with congenital LQTS and CPVT attending public hospitals in Hong Kong. The primary outcome was spontaneous ventricular tachycardia/ventricular fibrillation (VT/VF).

Results

A total of 142 congenital LQTS (mean onset age= 27±23 years old) and 16 CPVT (mean presentation age=11±4 years old) patients were included. For congenital LQTS, arrhythmias other than VT/VF (HR=4.67, 95% confidence interval = [1.53–14.3], p=0.007), initial VT/VF (HR=3.25 [1.29–8.16], p=0.012) and Schwartz score (HR=1.90 [1.11–3.26], p=0.020) were predictive of the primary outcome for the overall cohort, whilst arrhythmias other than VT/VF (HR=5.41 [1.36–21.4], p=0.016) and Schwartz score (HR=4.67 [1.48–14.7], p=0.009) were predictive for the adult subgroup (&gt;25 years old; n=58). All CPVT patients presented before the age of 25 but no significant predictors of VT/VF were identified. A random survival forest model identified initial VT/VF, Schwartz score, initial QTc interval, family history of LQTS, initially asymptomatic, and arrhythmias other than VT/VF as the most important variables for risk prediction in LQTS, and initial VT/VF/sudden cardiac death, palpitations, QTc, initially symptomatic and heart rate in CPVT.

Conclusion

Clinical and ECG presentation vary between the pediatric/young and adult congenital LQTS population. All CPVT patients presented before the age of 25. Machine learning models achieved more accurate VT/VF prediction.

Funding Acknowledgement

Type of funding sources: None. Kaplan-Meier survival curve for LQTSKaplan-Meier survival curve for CPVT

Risk stratification score for acute myocardial infarction and sudden cardiac death in type 2 diabetes mellitus

Funding Acknowledgements

Type of funding sources: None.

Introduction

Acute myocardial infarction (AMI) and sudden cardiac death (SCD) are major cardiovascular adverse outcomes in patients with type 2 diabetic mellitus. Although there are many risk scores on composite outcomes of major cardiovascular adverse outcomes or cardiovascular mortality for diabetic patients, these existing scores did not account for the difference in pathogenesis and prognosis between acute coronary syndrome and lethal ventricular arrhythmias. Furthermore, recent studies reported that HbA1c and lipid levels, which were often accounted for in these risk scores, have J/U-shaped relationships with adverse outcomes.

Purpose

The present study aims to evaluate the application of incorporating non-linear J/U-shaped relationships between mean HbA1c and cholesterol levels into risk scores for predicting for AMI and non-AMI related SCD respectively, amongst type 2 diabetes mellitus patients.

Methods

This was a territory-wide cohort study of patients with type 2 diabetes mellitus above the age 40 and free from prior AMI and SCD, with or without prescriptions of anti-diabetic agents between January 1st, 2009 to December 31st, 2009 at government-funded hospitals and clinics in Hong Kong. Risk scores were developed for predicting incident AMI and non-AMI related SCD. The performance of conditional inference survival forest (CISF) model compared to that of random survival forests (RSF) model and multivariate Cox model.

Results

This study included 261308 patients (age = 66.0 ± 11.8 years old, male = 47.6%, follow-up duration = 3552 ± 1201 days, diabetes duration = 4.77 ± 2.29 years). Mean HbA1c and high-density lipoprotein-cholesterol (HDL-C) were significant predictors of AMI under multivariate Cox regression and were linearly associated with AMI. Mean HbA1c and total cholesterol were significant multivariate predictors with a J-shaped relationship with non-AMI related SCD. The AMI and SCD risk scores had an area-under-the-curve (AUC) of 0.666 (95% confidence interval (CI)= [0.662, 0.669]) and 0.677 (95% CI= [0.673, 0.682]), respectively. CISF significantly improves prediction performance of both outcomes compared to RSF and multivariate Cox models.

Conclusions

A holistic combination of demographic, clinical, and laboratory indices can be used for the risk stratification of type 2 diabetic patients against AMI and SCD.

A Fully-Immersive and Automated Virtual Reality System to Assess the Six Domains of Cognition: Protocol for a Feasibility Study

Introduction: Dementia is increasing in prevalence in aging populations. Current questionnaire-based cognitive assessments may not comprehensively assess cognitive function and real-time task-performance. Virtual reality (VR) technology has been used in cognitive assessments but existing systems have limited scope in evaluating all cognitive domains. We have developed a novel, fully-immersive VR system (CAVIRE: Cognitive Assessment by VIrtual REality), which incorporates automated audio-visual instructions. An automated scoring matrix to assess the six cognitive domains—perceptual-motor function, executive function, complex attention, social cognition, learning and memory, and language—is embedded in the CAVIRE system.

Aims: The primary aim is to evaluate the feasibility of using the CAVIRE system to assess cognitive function of participants across different age groups from 35 to 84 years old. The secondary aims are to determine the CAVIRE performance-indices (completion time and scores) of the participants and to assess their acceptability toward the use of CAVIRE as a modality for cognitive assessment.

Methods: One hundred and seventy-five participants will be assessed by CAVIRE at a primary care clinic in Singapore. They will be first assessed using questionnaires: Montreal Cognitive Assessment (MoCA), Abbreviated Mental Test (AMT), Mini-Mental State Examination (MMSE), Basic Activities of Daily Living (BADLs), Instrumental Activities of Daily Living (IADLs). Those aged 65–84 years will be grouped into cognitively intact (n = 50, MoCA score ≥ 26) and cognitively impaired (n = 50, MoCA < 26). The CAVIRE performance-indices of cognitively healthy younger participants aged 35–64 years (n = 75) will serve as benchmark references. CAVIRE auto-computes the participant's performance-indices in 13 different segments. The tasks include domestic chores, memory, shopping, and social interactions. The proportion of participants who complete the entire VR assessment in each age group will be evaluated as feasibility indicators. The CAVIRE performance-indices will be compared across the different age groups. Feedback on the acceptability of the CAVIRE system will be collated and compared among the participants across the age groups.

Significance: CAVIRE is designed to assess the six domains of cognitive function using VR. The results of this feasibility study will provide insights for the implementation of the CAVIRE system as an alternative modality of cognitive assessment in the community.

P5014The NPAC score for predicting survival after incident acute myocardial infarction

Background

Risk stratification in acute myocardial infarction (AMI) is important for guiding clinical management. Current risk scores are mostly derived from clinical trials with stringent patient selection. We aimed to establish and evaluate a composite scoring system to predict short-term mortality after index episodes of AMI, independent of electrocardiography (ECG) pattern, in a large real-world cohort.

Methods

Using electronic health records, patients admitted to our regional teaching hospital (derivation cohort, n=2127) and an independent tertiary care center (validation cohort, n=1276) with index acute myocardial infarction between January 2013 and December 2017 as confirmed by principal diagnosis and laboratory findings, were identified retrospectively.

Results

Univariate logistic regression was used as the primary model to identify potential contributors to mortality. Stepwise forward likelihood ratio logistic regression revealed that neutrophil-to-lymphocyte ratio, peripheral vascular disease, age, and serum creatinine (NPAC) were significant predictors for 90-day mortality (Hosmer-Lemeshow test, P=0.21). Each component of the NPAC score was weighted by beta-coefficients in multivariate analysis. The C-statistic of the NPAC score was 0.75, which was higher than the conventional Charlson's score (C-statistic=0.63). Application of a deep learning model to our dataset improved the accuracy of classification with a C-statistic of 0.81.

Multivariate binary logistic regression Variable β Adjusted Odds ratio (95% CI) P-value Points Age ≥65 years 1.304 3.68 (2.63–5.17) <0.001 2 Peripheral vascular disease 1.109 3.03 (1.52–6.04) 0.002 2 NLRt ≥9.51 1.100 2.73 (2.12–3.51) <0.001 1 Creatinine≥109 μmol/L 1.003 3.00 (2.35–3.85) <0.001 2

NPAC deep learning model

Conclusions

The NPAC score comprised of four items from routine laboratory parameters and basic clinical information and can facilitate early identification of cases at risk of short-term mortality following index myocardial infarction. Deep learning model can serve as a gate-keeper to provide more accurate prediction to facilitate clinical decision making.

Virtual Reality for Screening of Cognitive Function in Older Persons: Comparative Study

Background

The prevalence of dementia, which presents as cognitive decline in one or more cognitive domains affecting function, is increasing worldwide. Traditional cognitive screening tools for dementia have their limitations, with emphasis on memory and, to a lesser extent, on the cognitive domain of executive function. The use of virtual reality (VR) in screening for cognitive function in older persons is promising, but evidence for its use is sparse.

Objective

The primary aim was to examine the feasibility and acceptability of using VR to screen for cognitive impairment in older persons in a primary care setting. The secondary aim was to assess the module’s ability to discriminate between cognitively intact and cognitively impaired participants.

Methods

A comparative study was conducted at a public primary care clinic in Singapore, where persons aged 65-85 years were recruited based on a cut-off score of 26 on the Montreal Cognitive Assessment (MoCA) scale. They participated in a VR module for assessment of their learning and memory, perceptual-motor function, and executive function. Each participant was evaluated by the total performance score (range: 0-700) upon completion of the study. A questionnaire was also administered to assess their perception of and attitude toward VR.

Results

A total of 37 participants in Group 1 (cognitively intact; MoCA score≥26) and 23 participants in Group 2 (cognitively impaired; MoCA score<26) were assessed. The mean time to completion of the study was 19.1 (SD 3.6) minutes in Group 1 and 20.4 (3.4) minutes in Group 2. Mean feedback scores ranged from 3.80 to 4.48 (max=5) in favor of VR. The total performance score in Group 1 (552.0, SD 57.2) was higher than that in Group 2 (476.1, SD 61.9; P<.001) and exhibited a moderate positive correlation with scores from other cognitive screening tools: Abbreviated Mental Test (0.312), Mini-Mental State Examination (0.373), and MoCA (0.427). A receiver operating characteristic curve analysis for the relationship between the total performance score and the presence of cognitive impairment showed an area under curve of 0.821 (95% CI 0.714-0.928).

Conclusions

We demonstrated the feasibility of using a VR-based screening tool for cognitive function in older persons in primary care, who were largely in favor of this tool.

Comparison of high-flow nasal cannula versus oxygen face mask for environmental bacterial contamination in critically ill pneumonia patients: a randomized controlled crossover trial

Whereas high-flow nasal cannula use is gaining prevalence, its high gas flow raises concerns about aerosolization of infectious particles and spread of infection. This randomized controlled crossover non-inferiority trial (N = 20) evaluated the degree of environmental contamination by viable bacteria associated with the use of high-flow nasal cannula compared with conventional oxygen mask for critically ill patients with Gram-negative pneumonia. The results show that high-flow nasal cannula use was not associated with increased air or contact surface contamination by either Gram-negative bacteria or total bacteria, suggesting that additional infection control measures are not required.

Atrial fibrillation patients who sustained warfarin-associated intracerebral haemorrhage have poor neurological outcomes: results from a matched case series

INTRODUCTION

Coagulopathy-associated intracerebral haemorrhage has become increasingly common because of the rising demand in the ageing population for anticoagulation for atrial fibrillation. This study compared the clinical features and neurological outcomes of intracerebral haemorrhage in patients with atrial fibrillation who were prescribed warfarin with those who were not.

METHODS

This was a retrospective matched case series of patients with intracerebral haemorrhage from three tertiary hospitals in Hong Kong from 1 January 2006 to 31 December 2011. Patients who developed intracerebral haemorrhage and who were prescribed warfarin for atrial fibrillation (ICH-W group) were compared with those with intracerebral haemorrhage and not prescribed warfarin (ICH-C group); they were matched for age and gender in 1:1 ratio. Clinical features and neurological outcomes were compared, and the impact of coagulopathy on haematoma size was also studied.

RESULTS

We identified 114 patients in the ICH-W group with a mean age of 75 years. Both ICH-W and ICH-C groups had a median intracerebral haemorrhage score of 2. There was a non-statistically significant trend of higher intracerebral haemorrhage volume in the ICH-W group (12.9 mL vs 10.5 mL). The median modified Rankin Scale and the proportion with good recovery (modified Rankin Scale score ≤3) at 6 months were comparable. Nonetheless, ICH-W patients had higher hospital mortality (51.8% vs 36.0%; P=0.02) and 6-month mortality (60.5% vs 43.0%; P=0.01) than ICH-C patients. Overall, 60% of ICH-W patients had their admission international normalised ratio within the therapeutic range during intracerebral haemorrhage, and 14% had a subtherapeutic admission international normalised ratio. International normalised ratio at admission was not associated with intracerebral haemorrhage volume or neurological outcome.

CONCLUSION

Warfarin-associated intracerebral haemorrhage in patients with atrial fibrillation carried a higher stroke mortality than the non-warfarinised patients.

A randomized controlled trial of 2 protocols for weaning cardiac surgical patients receiving adaptive support ventilation

PURPOSE

This study aims to compare the effectiveness of weaning with adaptive support ventilation (ASV) incorporating progressively reduced or constant target minute ventilation in the protocol in postoperative care after cardiac surgery.

MATERIAL AND METHODS

A randomized controlled unblinded study of 52 patients after elective coronary artery bypass surgery was carried out to determine whether a protocol incorporating a decremental target minute ventilation (DTMV) results in more rapid weaning of patients ventilated in ASV mode compared to a protocol incorporating a constant target minute ventilation.

RESULTS

Median duration of mechanical ventilation (145 vs 309 minutes; P = .001) and intubation (225 vs 423 minutes; P = .005) were significantly shorter in the DTMV group. There was no difference in adverse effects (42% vs 46%) or mortality (0% vs 0%) between the 2 groups.

CONCLUSIONS

Use of a DTMV protocol for postoperative ventilation of cardiac surgical patients in ASV mode results in a shorter duration of ventilation and intubation without evidence of increased risk of adverse effects.

Rosuvastatin improves endothelial function in db/db mice: role of angiotensin II type 1 receptors and oxidative stress

BACKGROUND AND PURPOSE

HMG-CoA reductase inhibitors, statins, with lipid-reducing properties combat against atherosclerosis and diabetes. The favourable modulation of endothelial function may play a significant role in this effect. The present study aimed to investigate the cellular mechanisms responsible for the therapeutic benefits of rosuvastatin in ameliorating diabetes-associated endothelial dysfunction.

EXPERIMENTAL APPROACH

Twelve-week-old db/db diabetic mice were treated with rosuvastatin at 20 mg·kg⁻¹ ·day⁻¹ p.o.for 6 weeks. Isometric force was measured in isolated aortae and renal arteries. Protein expressions including angiotensin II type 1 receptor (AT₁R), NOX4, p22(phox) , p67(phox) , Rac-1, nitrotyrosine, phospho-ERK1/2 and phospho-p38 were determined by Western blotting, while reactive oxygen species (ROS) accumulation in the vascular wall was evaluated by dihydroethidium fluorescence and lucigenin assay.

KEY RESULTS

Rosuvastatin treatment of db/db mice reversed the impaired ACh-induced endothelium-dependent dilatations in both renal arteries and aortae and prevented the exaggerated contractions to angiotensin II and phenylephrine in db/db mouse renal arteries and aortae. Rosuvastatin reduced the elevated expressions of AT₁R, p22(phox) and p67(phox) , NOX4, Rac1, nitrotyrosine and phosphorylation of ERK1/2 and p38 MAPK and inhibited ROS production in aortae from db/db mice.

CONCLUSIONS AND IMPLICATIONS

The vasoprotective effects of rosuvastatin are attributed to an increase in NO bioavailability, which is probably achieved by its inhibition of ROS production from the AT₁R-NAD(P)H oxidase cascade.

Relative contribution of individual oxidized components in ox-LDL to inhibition on endothelium-dependent relaxation in rat aorta

BACKGROUND AND AIM

Oxidized low-density lipoprotein (ox-LDL) causes atherosclerosis and endothelial dysfunction. No study up to the present date has examined the relative contribution of all the oxidized components in ox-LDL to inhibition on vascular function. Our aim was to investigate the effects of individual oxidized components at concentrations similar to those in ox-LDL on the impairment of endothelium-dependent relaxation in rat aorta.

METHODS AND RESULTS

Rat thoracic aorta was pre-treated with lysophosphatidylcholine (LPC), cholesterol oxidized products (COPs), oxidized linoleic acid (ox-18:2) and oxidized linolenic acid (ox-18:3) at concentrations similar to those in human ox-LDL. Ox-LDL as a whole caused 61% inhibition while LPC, COPs and ox-18:2 at concentrations similar to those in ox-LDL caused 12%, 24% and 19% inhibition, respectively, on endothelium-dependent relaxation, suggesting that COPs produced the most adverse effect followed by ox-18:2 and LPC in an additional way. Three COPs including 7-ketocholesterol, 7α-hydroxycholesterol and 7β-hydroxycholesterol showed inhibition on endothelium-dependent relaxation with E(max) being reduced to 79-87% compared with the control E(max) (95%). At Western blot analysis phosphorylation of eNOS at Ser1177 site and total eNOS were not altered by ox-LDL treatment, indicating that ox-LDL did not affect nitric oxide (NO) synthesis capacity. Ox-LDL might react directly with NO and lower NO bioavailability.

CONCLUSION

The present study demonstrated the relative contribution of individual oxidized components in ox-LDL in the inhibition of endothelium-dependent relaxation in rat aorta. This inhibitory effect could be caused by the reduction of NO bioactivity.

Rapid determination of total Kjeldahl nitrogen using microwave digestion

A closed-vessel microwave digestion process for the determination of total Kjeldahl nitrogen (TKN) has been developed for sewage and wastewater. TKN values obtained from the microwave digestion method were in excellent agreement with those of the thermal digestion method. The accuracy of both analytical methods is comparable. In comparison to the conventional thermal digestion, the microwave method shortened the time required for complete digestion from 4 h to 25 min, and also decreased the maximum digestion temperature from 380 degrees C to 200 degrees C. This developed method may contribute to a significant reduction in sample digestion time, resulting in an increase in analytical throughput. The microwave digestion method developed in this study could be a rapid and efficient means for TKN determination for sewage wastewater and sludge.

Establishment of a model of cortical bone repair in mice

A model of cortical bone repair has been established for use in mice. The cortical defect consisted of a hole drilled through the entire diameter of the tibial diaphysis. The hematoma that initially filled the drill site was invaded by cells of mesenchymal appearance within 5 days of injury. Trabeculae of mineralized woven bone were present throughout the drill site by day 9. A reaction in the periosteum adjacent to the drill site, consisting of both new bone and cartilage formation, preceded deposition of bone tissue in the drill site. New woven bone was modeled to restore the marrow cavity to normal by 4 weeks after injury, and almost normal cortical structure was achieved by 6 weeks after injury. Immunohistochemical studies indicated that type III collagen was expressed within the drill site by day 5, reached a peak at day 7, and was diminished by day 9. In contrast, type I collagen was first detectable in the drill site at day 7, and staining was more intense by day 9. Osteopontin expression in the drill site coincided with the process of mineralization of new bone in this location. The model of bone repair described here provides a method for inducing reproducible bone lesions in a readily identifiable location in mice. It will be useful in the investigation of bone cell function in mouse strains that have been subjected to genetic manipulation.

Ferromagnetic Ordering in a Diamond-Like Cyano-Bridged Mn(II) Ru(III) Bimetallic Coordination Polymer

Cyano-mediated interaction of the alternating high-spin Mn(II) centers and low-spin Ru(III) centers in {Mn[Ru(acac)2 (CN)2 ]2 }n (Hacac=acetylacetone) results in long-range ferromagnetic ordering below 3.6 K. This novel Mn(II) Ru(III) coordination polymer, which has a diamond-like structure, was constructed from [Ru(acac)2 (CN)2 ](-) and Mn(2+) ions.

Changing specificity of neurotransmitter regulation of rapid dendritic remodeling during synaptogenesis

Wiring the developing nervous system requires appropriate contact between presynaptic axons and postsynaptic dendrites. Rapid movements of filopodia-like structures on immature dendrites are thought to facilitate initial synaptogenic contact with axons. Here we show that not only can different forms of neurotransmission regulate dendritic filopodial motility, but they do so in a developmentally regulated manner, suggestive of a specific relationship between the action of a neurotransmitter and the corresponding type of synapse being formed.

Synthesis, characterisation, crystal structures, reactivity, and electrochemistry of ruthenium-nitrido, ruthenium-cobalt-imido and ruthenapyrrolidone carbonyl clusters containing alkyne ligands

Thermolysis of [Ru3(CO)9(mu3-NOMe)(mu3-eta2-PhC2Ph)] (1) with two equivalents of [Cp*Co(CO)2] in THF afforded four new clusters, brown [Ru5(CO)8(mu-CO)3(eta5-C5Me5)(mu5-N)(mu4-eta2-PhC2Ph)] (2), green [Ru3Co2(CO)7(mu3-CO)(eta5-C5Me5)2(mu3-NH)[mu4-eta8-C6H4-C(H)C(Ph)]] (3), orange [Ru3(CO)7(mu-eta6-C5Me4CH2)[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (4) and pale yellow [Ru2(CO)6[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (5). Cluster 2 is a pentaruthenium mu5-nitrido complex, in which the five metal atoms are arranged in a novel "spiked" square-planar metal skeleton with a quadruply bridging alkyne ligand. The mu5-nitrido N atom exhibits an unusually low frequency chemical shift in its 15N NMR spectrum. Cluster 3 contains a triangular Ru2Co-imido moiety linked to a ruthenium-cobaltocene through the mu4-eta8-C6H4C(H)C(Ph) ligand. Clusters 4 and 5 are both metallapyrrolidone complexes, in which interaction of diphenylacetylene with CO and the NOMe nitrene moiety were observed. In 4, one methyl group of the Cp* ring is activated and interacts with a ruthenium atom. The "distorted" Ru3Co butterfly nitrido complex [Ru3Co(CO)5(eta5-C5Me5)(mu4-N)(mu3-eta2-PhC2Ph)(mu-I)2I] (6) was isolated from the reaction of 1 with [Cp*Co(CO)I2] heated under reflux in THF, in which a Ru-Ru wing edge is missing. Two bridging and one terminal iodides were found to be placed along the two Ru-Ru wing edges and at a hinge Ru atom, respectively. The redox properties of the selected compounds in this study were investigated by using cyclic voltammetry and controlled potential coulometry. 15N magnetic resonance spectroscopy studies were also performed on these clusters.

Ruthenium(II) ammine and hydrazine complexes with [N(Ph2PQ)2]- (Q = S, Se) ligands

Reactions of coordinatively unsaturated Ru[N(Ph2PQ)2]2(PPh3) (Q = S (1), Se (2)) with pyridine (py), SO2, and NH3 afford the corresponding 18e adducts Ru[N(Ph2PQ)2]2(PPh3)(L) (Q = S, L = NH3 (5); Q = Se, L = py (3), SO2 (4), NH3 (6)). The molecular structures of complexes 2 and 6 are determined. The geometry around Ru in 2 is pseudo square pyramidal with PPh3 occupying the apical position, while that in 6 is pseudooctahedral with PPh3 and NH3 mutually cis. The Ru-P distances in 2 and 6 are 2.2025(11) and 2.2778(11) A, respectively. The Ru-N bond length in 6 is 2.185(3) A. Treatment of 1 or 2 with substituted hydrazines L or NH2OH yields the respective adducts Ru[N(Ph2PQ)2]2(PPh3)(L) (Q = S, L = NH2NH2 (12), t-BuNHNH2 (14), l-aminopiperidine (C5H10NNH2) (15); Q = Se, L = PhCONHNH2 (7), PhNHNH2 (8), NH2OH (9), t-BuNHNH2 (10), C5H10NNH2 (11), NH2NH2 (13)), which are isolated as mixtures of their trans and cis isomers. The structures of cis-14 and cis-15 are characterized by X-ray crystallography. In both molecular structures, the ruthenium adopts a pseudooctahedral arrangement with PPh3 and hydrazine mutually cis. The Ru-N bond lengths in cis-14.CH2Cl2 and cis-15 are 2.152(3) and 2.101(3) A, respectively. The Ru-N-N bond angles in cis-14.CH2Cl2 and cis-15 are 120.5(4) and 129.0(2) degrees, respectively. Treatment of 1 with hydrazine monohydrate leads to the isolation of yellow 5 and red trans-Ru[N(Ph2PS)2]2(NH3)(H2O) (16), which are characterized by mass spectrometry, 1H NMR spectroscopy, and elemental analyses. The geometry around ruthenium in 16 is pseudooctahedral with the NH3 and H2O ligands mutually trans. The Ru-O and Ru-N bond distances are 2.118(4) and 2.142(6) A, respectively. Oxidation reactions of the above ruthenium hydrazine complexes are also studied.

Multicolor "DiOlistic" labeling of the nervous system using lipophilic dye combinations

We describe a technique for rapid labeling of a large number of cells in the nervous system with many different colors. By delivering lipophilic dye-coated particles to neuronal preparations with a "gene gun," individual neurons and glia whose membranes are contacted by the particles are quickly labeled. Using particles that are each coated with different combinations of various lipophilic dyes, many cells within a complex neuronal network can be simultaneously labeled with a wide variety of colors. This approach is most effective in living material but also labels previously fixed material. In living material, labeled neurons continue to show normal synaptic responses and undergo dendritic remodeling. This technique is thus useful for studying structural plasticity of neuronal circuits in living preparations. In addition, the Golgi-like labeling of neurons with many different colors provides a novel way to study neuronal connectivity.

Rapid dendritic remodeling in the developing retina: dependence on neurotransmission and reciprocal regulation by Rac and Rho

We demonstrate that within the intact and spontaneously active retina, dendritic processes of ganglion cells exhibit rapid and extensive movements during the period of synaptogenesis. Marked restructuring occurs in seconds, but structural changes are relatively balanced across the dendritic arbor, maintaining overall arbor size and complexity over hours. Dendritic motility is regulated by spontaneous glutamatergic transmission. Both the rate and extent of the movements are decreased by antagonists to NMDA and non-NMDA glutamate receptors but are unaffected by tetrodotoxin, a sodium channel blocker. The dendritic movements are actin dependent and are controlled by the Rho family of small GTPases. Transfection of dominant-negative and constitutively active mutants into ganglion cells showed that Rac and Rho exert reciprocal effects on motility. We suggest that the Rho family of small GTPases could integrate activity-dependent and -independent signals from afferents, thereby adjusting target motility and maximizing the chance for initial contact and subsequent synaptogenesis.

Rapid dendritic movements during synapse formation and rearrangement

Major technical advances in the imaging of live cells have led to a recent flurry of studies demonstrating how dendrites remodel dynamically during development. Taken together with our current understanding of axonal development, these studies help provide a more unified picture of how neural circuits might be formed altered or maintained throughout life.

Developmental changes in the neurotransmitter regulation of correlated spontaneous retinal activity

Synchronized spontaneous rhythmic activity is a feature common to many parts of the developing nervous system. In the early visual system, before vision, developing circuits in the retina generate synchronized patterns of bursting activity that contain information useful for patterning connections between retinal ganglion cells and their central targets. However, how developing retinal circuits generate and regulate these spontaneous activity patterns is still incompletely understood. Here we show that in developing retinal circuits, the nature of excitatory neurotransmission driving correlated bursting activity in ganglion cells is not fixed but undergoes a developmental shift from cholinergic to glutamatergic transmission. In addition, we show that this shift occurs as presynaptic glutamatergic bipolar cells form functional connections onto the ganglion cells, implicating the role of bipolar cells in providing endogenous drive to bursting activity later in development. This transition coincides with the period when subsets of ganglion cells (On and Off cells) develop distinct activity patterns that are thought to underlie the refinement of their connectivity with their central targets. Here, our results suggest that the differences in activity patterns of On and Off ganglion cells may be conferred by differential synaptic drive from On and Off bipolar cells, respectively. Taken together, our results suggest that the regulation of patterned spontaneous activity by neurotransmitters undergoes systematic change as new cellular elements are added to developing circuits and also that these new elements can help specify distinct activity patterns appropriate for shaping connectivity patterns at later ages.

Human JIK, a novel member of the STE20 kinase family that inhibits JNK and is negatively regulated by epidermal growth factor

Mammalian members related to Saccharomyces cerevisiae serine/threonine kinase STE20 can be divided into two subfamilies based on their structure and function. The PAK subfamily is characterized by an N-terminal p21-binding domain (also known as CRIB domain), a C-terminal kinase domain, and is regulated by the small GTP-binding proteins Rac1 and Cdc42Hs. The second group is represented by the GCK-like members, which contain an N-terminal catalytic domain and lack the p21-binding domain. Some of them have been demonstrated to induce c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) cascade, while others have been shown to be activated by a subset of stress conditions or apoptotic agents, although little is known about their specific function. Here, we have identified a novel human STE20-related serine/threonine kinase, belonging to the GCK-like subfamily. This kinase does not induce the JNK/SAPK pathway, but, instead, inhibits the basal activity of JNK/SAPK, and diminishes its activation in response to human epidermal growth factor (EGF). Therefore, we designated this molecule JIK for JNK/SAPK-inhibitory kinase. The inhibition of JNK/SAPK signaling pathway by JIK was found to occur between the EGF receptor and the small GTP-binding proteins Rac1 and Cdc42Hs. In contrast, JIK does not activate nor does it inhibit ERK2, ERK6, p38, or ERK5. Furthermore, JIK kinase activity is not modulated by any exogenous stimuli, but, interestingly, it is dramatically decreased upon EGF receptor activation. Thus, JIK might represent the first member of the STE20 kinase family whose activity can be negatively regulated by tyrosine kinase receptors, and whose downstream targets inhibit, rather than enhance, JNK/SAPK activation.

A novel peptide-SH3 interaction

SH3 domains constitute a family of protein-protein interaction modules that bind to peptides displaying an X-proline-X-X-proline (XPXXP) consensus. We report that the SH3 domain of Eps8, a substrate of receptor and non-receptor tyrosine kinases, displays a novel and unique binding preference. By a combination of approaches including (i) screening of phage-displayed random peptide libraries, (ii) mapping of the binding regions on three physiological interactors of Eps8, (iii) alanine scanning of binding peptides and (iv) in vitro cross-linking, we demonstrate that a proline-X-X-aspartate-tyrosine (PXXDY) consensus is indispensable for binding to the SH3 domain of Eps8. Screening of the Expressed Sequence Tags database allowed the identification of three Eps8-related genes, whose SH3s also display unusual binding preferences and constitute a phylogenetically distinct subfamily within the SH3 family. Thus, Eps8 identifies a novel family of SH3-containing proteins that do not bind to canonical XPXXP-containing peptides, and that establish distinct interactions in the signaling network.

Muurolane sesquiterpenes from illicium tsangii

A dichloromethane extract of Illicium tsangii has yielded five novel muurolane sesquiterpenes (1, 2, 6, 7, 9) and three new menthane monoterpenes (10-12) in addition to several known compounds. Biogenetic relationships among the sesquiterpenes are discussed.

Developmentally regulated spontaneous activity in the embryonic chick retina

Even before birth and the onset of sensory experience, neural activity plays an important role in shaping the vertebrate nervous system. In the embryonic chick visual system, activity in the retina before vision has been implicated in the refinement of retinotopic maps, the elimination of transient projections, and the survival of a full complement of neurons. In this study, we report the detection of a physiological substrate for these phenomena: waves of spontaneous activity in the ganglion cell layer of the embryonic chick retina. The activity is robust and highly patterned, taking the form of large amplitude, rhythmic, and wide-ranging waves of excitation that propagate across the retina. Activity waves are most prominent and organized between embryonic days 13-18, coinciding with the developmental period during which retinal axons refine their connections in their targets. The spatial and temporal features of the patterns observed are consistent with the role of activity patterns in shaping eye-specific projections and retinotopic maps but inconsistent with the hypothesis that they specify lamina-specific projections in the tectum. Antagonists of glutamatergic and glycinergic transmission and of gap junctional communication suppress spontaneous activity, whereas antagonists to GABAergic transmission potentiate it. Based on these results, we propose that spontaneous activity in the ganglion cells is regulated by chemical inputs from both bipolar and amacrine cells and by gap junctional coupling involving ganglion cells.

The SH3 domain of Eps8 exists as a novel intertwined dimer

SH3 domains are structurally well-characterized as monomeric modular units of protein structure that mediate protein-protein recognition in numerous signal transduction proteins. The X-ray crystallographic structure of the Eps8 SH3 domain reveals a novel variation of the canonical SH3 fold: the SH3 domain from Eps8 is a dimer formed by strand interchange. In addition, co-immunoprecipitation experiments show that intact Eps8 is multimeric in vivo. Hence, the SH3 domain of Eps8 may represent a dimerization motif.

Application of homonuclear 3D NMR experiments and 1D analogs to study the conformation of sialyl Lewis(x) bound to E-selectin

The conformation of the sialyl Lewis(x) tetrasaccharide bound to E-selectin was previously determined from transfer NOE (trNOE) experiments in conjunction with a distance-geometry analysis. However, the orientation of the tetrasaccharide ligand in the binding site of E-selectin is still unknown. It can be predicted that the accurate quantitative analysis of all trNOEs, including those originating from spin diffusion, is one key to analyze the orientation of sialyl Lewis(x) in the binding pocket of E-selectin. Therefore, we applied homonuclear 3D NMR experiments and 1D analogs to obtain trNOEs that could not unambiguously be assigned from previous 2D trNOESY spectra, due to severe resonance-signal overlap. A 3D TOCSY-trNOESY experiment, a 1D TOCSY-trNOESY experiment, and a 1D trNOESY-TOCSY experiment of the sialyl Lewis(x)/E-selectin complex furnished new interglycosidic trNOEs and provided additional information for the interpretation of trNOEs that have been described before. A 2D trROESY spectrum of the sialyl Lewis(x)/E-selectin complex allowed one to identify the amount of spin-diffusion contributions to trNOEs. Finally, an unambiguous assignment of all trNOEs, and an analysis of spin-diffusion pathways, was obtained, creating a basis for a quantitative analysis of trNOEs in the sialyl Lewis(x)/E-selectin complex.

Isolation and characterization of e3B1, an eps8 binding protein that regulates cell growth

Eps8, a substrate of receptor tyrosine kinases, is an SH3 domain containing protein that plays an important role in mitogenic signaling. To determine the cellular function of eps8, we used the SH3 domain of eps8 to screen a human fibroblast M426 expression library and identified, a full-length cDNA clone of 3.2 kb. We designated this clone e3B1 for eps8 SH3 domain binding protein 1. Northern analysis revealed that expression of e3B1 mRNA was ubiquitous in human tissues. The e3B1 gene encodes a SH3 domain containing protein. We show that anti-e3B1 antibodies detect three cytosolic protein species of 65, 68 and 72 kDa in cell lysate isolated from asynchronously growing NIH3T3 cells. E3B1 binds to the SH3 domain of eps8 and Abl in vitro. We also demonstrated that e3B1 associates with eps8 in vivo. Phosphatase digestion and phosphoamino acid analysis revealed that p65e3B1 is a phosphoserine containing protein and p72e3B1 and p68e3B1 are hyperserine-phosphorylated form of p65e3B1. We further determined that the p65e3B1 was the most abundant in serum-starved NIH/EGFR cells. Time course studies initiated by the addition of epidermal growth factor (EGF) revealed that the p72e3B1 started to accumulate at 4 h, peaked at 8 h and remained high until 24 h. Finally, we demonstrate that NIH/EGFR fibroblasts overexpressing e3B1 grow more slowly relative to matched controls.

RN-tre identifies a family of tre-related proteins displaying a novel potential protein binding domain

Eps8 is a recently identified SH3-containing substrate for tyrosine kinase receptors. To understand the role of eps8 in receptor-mediated signaling, we cloned cDNAs encoding proteins that bind to its SH3 domain. One of these cDNAs predicts the synthesis of an 828 amino acid protein with homology to the N-terminal region of the tre oncogene. We designated this protein RN-tre for Related to the N-terminus of tre. RN-tre is ubiquitously expressed and maps to 10p13, a region known to be involved in translocations in various leukemias. In addition, a 10p13 monosomy syndrome, characterized by developmental alterations, has been reported. The regional homology between RN-tre and tre, which is limited to their N-terminal portion, prompted us to investigate the origin of the tre oncogene transcriptional unit. We were able to show that tre is the fusion product of a 5' genetic element, homologous to RN-tre and a 3' element, encoding a de-ubiquinating enzyme. Moreover, we identified, within the N-terminus of RN-tre and tre, a domain (named TrH, for Tre Homology), which is conserved within several proteins from yeast to mammals and has protein-binding properties in vitro.

RN-tre specifically binds to the SH3 domain of eps8 with high affinity and confers growth advantage to NIH3T3 upon carboxy-terminal truncation

We isolated a cDNA encoding a protein, RN-tre, which shows homology to the N-terminus of the tre oncogene product and has SH3-binding ability as well as an evolutionarily conserved domain, termed TrH, with protein-binding ability in vitro. In the present study, we identify the product of the RN-tre gene as a 97-100 kDa protein. We demonstrate stable association in vivo and in vitro between RN-tre and eps8, mediated by the SH3 domain of the latter. In vitro, RN-tre displayed remarkable preference for binding to the eps8-SH3, as compared to eight other SH3s. The Kd for the in vitro interaction between RN-tre and eps8-SH3 was between 10(-8) and 10(-7) M. A role for RN-tre in cell proliferation was suggested by the finding that a C-terminal truncated mutant was able to confer proliferative advantage and reduced serum-requirement to NIH3T3 fibroblasts. Finally, comparison of the structure and biological activities of RN-tre and of the tre oncogene product, provided insight into the mechanism of oncogenic activation of tre.

A protein-binding domain, EH, identified in the receptor tyrosine kinase substrate Eps15 and conserved in evolution

In this report we structurally and functionally define a binding domain that is involved in protein association and that we have designated EH (for Eps15 homology domain). This domain was identified in the tyrosine kinase substrate Eps15 on the basis of regional conservation with several heterogeneous proteins of yeast and nematode. The EH domain spans about 70 amino acids and shows approximately 60% overall amino acid conservation. We demonstrated the ability of the EH domain to specifically bind cytosolic proteins in normal and malignant cells of mesenchymal, epithelial, and hematopoietic origin. These observations prompted our search for additional EH-containing proteins in mammalian cells. Using an EH domain-specific probe derived from the eps15 cDNA, we cloned and characterized a cDNA encoding an EH-containing protein with overall similarity to Eps15; we designated this protein Eps15r (for Eps15-related). Structural comparison of Eps15 and Eps15r defines a family of signal transducers possessing extensive networking abilities including EH-mediated binding and association with Src homology 3-containing proteins.

Expression of the receptor tyrosine kinase substrate genes eps8 and eps15 during mouse development

Receptor tyrosine kinases (RTKs) control proliferation and differentiation through their ability to bind and/or phosphorylate intracellular substrates. The repertoire of substrates recruited by different RTK is largely overlapping. It is not clear, therefore, how a cell distinguishes among signals originating from different RTKs. One possibility is that selective availability of substrates participates in the regulation of this process. To gain insight into this issue, we studied the expression pattern, during mouse embryogenesis, of the eps8 and eps15 genes, which encode two recently identified RTK substrates. Both genes are expressed from E 10 in a restricted fashion. eps8 is first expressed in frontonasal neural crest-derived cells, in the mesenchyme of branchial arches and in the liver primordium. At E 12.5-E 14, eps8 is additionally expressed in the central nervous system (CNS) in a regional restricted pattern at the met-mesencephalic transition area and in the developing submandibular salivary glands. eps15 is expressed at E 10 in the liver primordium, in the spinal ganglia and in the encephalic ganglia derived from the hindbrain neural crest. In addition, at E 12.5-E 14, eps15 is expressed, along all the CNS, in the ventricular zone where undifferentiated neuroblasts are located. The regional pattern of developmental expression of these two substrates sharply contrasts with their ubiquitous expression in adults, raising the possibility that their expression during embryogenesis is linked to selective proliferative and/or differentiative responses of specific neuroectodermal regions and body organs.

Quantitative analysis of Grb2-Sos1 interaction: the N-terminal SH3 domain of Grb2 mediates affinity

Grb2 is an adaptor protein that links receptor and cytoplasmic tyrosine kinases to the Ras signalling pathway by binding the Ras-specific guanine nucleotide exchange factor, Sos1, through its SH3 domains. The Grb2-SH3 domain binding has been localized to the carboxy-terminal two hundred amino acids of Sos1 (Sos1-c). By using real time biospecific interaction analysis (BIAcore), we studied the kinetic parameters and binding affinity of the Grb2-Sos1-c interaction. The binding of Grb2 to Sos1-c is a high affinity interaction with a moderate association rate (9.45 x 10(4) per M per s), a slow dissociation rate (13.8 x 10(-5) s), and an affinity constant of 1.48 nM. BIAcore measurements on isolated N-terminal and C-terminal SH3 domains (NSH3 and CSH3) further indicate that the high affinity Grb2-Sos1-c interaction is primarily mediated through the NSH3 domain (Kd = 1.68 nM). The CSH3 domain shows substantially reduced binding to Sos1-c in these measurements. Inhibition studies with BIAcore using proline rich peptides derived from the C-terminus of Sos1 show that there is a single major binding site for Grb2 in Sos1. This binding site is contained within the peptide N20, which corresponds to amino acids 1143-1162 of Sos1. This peptide completely blocks the Grb2-Sos1-c and NSH3-Sos1-c interactions with IC50 values of 8 microM and 4 microM respectively. The discrete interaction between the NSH3 domain and the N20 peptide may be amenable for drug discovery through screening or peptidomimetic approaches.

Constitutive phosphorylation of eps8 in tumor cell lines: relevance to malignant transformation

eps8, a recently identified tyrosine kinase substrate, has been shown to augment epidermal growth factor (EGF) responsiveness, implicating it in EGF receptor (EGFR)-mediated mitogenic signaling. We investigated the status of eps8 phosphorylation in normal and transformed cells and the role of eps8 in transformation. In NIH 3T3 cells overexpressing EGFR (NIH-EGFR), eps8 becomes rapidly phosphorylated upon EGF stimulation. At receptor-saturating doses of EGF, approximately 30% of the eps8 pool is tyrosine phosphorylated. Under physiological conditions of activation (i.e., at low receptor occupancy), corresponding to the 50% effective dose of EGF for mitogenesis, approximately 3 to 4% of the eps8 contains phosphotyrosine. In human tumor cell lines, we detected constitutive tyrosine phosphorylation of eps8, with a stoichiometry (approximately 5%) similar to that associated with potent mitogenic response in NIH-EGFR cells. Overexpression of eps8 was able to transform NIH 3T3 cells under limiting conditions of activation of the EGFR pathway. Concomitant tyrosine phosphorylation of eps8 and shc, but not of rasGAP, phospholipase C-gamma, and eps15, was frequently detected in tumor cells. This suggested that eps8 and shc might be part of a pathway which is preferentially selected in some tumors. Cooperation between these two transducers was further indicated by the finding of their in vivo association. This association was, at least in part, dependent on recognition of shc by the SH3 domain of eps8. Our results indicate that eps8 is physiologically part of the EGFR-activated signaling and that its alterations can contribute to the malignant phenotype.

Direct binding of eps8 to the juxtamembrane domain of EGFR is phosphotyrosine- and SH2-independent

Several signal transducers bind through their SH2 domains to phosphotyrosine-containing motifs present in receptor tyrosine kinases (RTKs). However, the juxtamembrane regions of the epidermal growth factor receptor (EGFR) and of the related erbB-2 protein, while important in mitogenic signaling, lack demonstrable tyrosine phosphorylation sites, suggesting that other modalities of receptor-transducer interactions exist. A candidate for investigating this type of association is p97eps8, a recently described substrate for RTKs. p97eps8 is phosphorylated by several RTKs, associates with EGFR in vivo and, upon overexpression, enhances the transduction of EGFR-mediated mitogenic signals. Here we report that eps8 binds directly to the juxtamembrane region of EGFR through a domain that does not bear resemblance to SH2 domains and by a mechanism that does not require the presence of phosphotyrosine residues. Thus, the physical association between EGFR and eps8 represents a novel interaction between RTKs and their substrates.