Publications by authors named "Ciara Mahon"

18 Publications

  • Page 1 of 1

Prevalence and Disease Spectrum of Extracoronary Arterial Abnormalities in Spontaneous Coronary Artery Dissection.

JAMA Cardiol 2021 Nov 24. Epub 2021 Nov 24.

Department of Cardiovascular Sciences, University of Leicester, NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, United Kingdom.

Importance: Spontaneous coronary artery dissection (SCAD) has been associated with fibromuscular dysplasia (FMD) and other extracoronary arterial abnormalities. However, the prevalence, severity, and clinical relevance of these abnormalities remain unclear.

Objective: To assess the prevalence and spectrum of FMD and other extracoronary arterial abnormalities in patients with SCAD vs controls.

Design, Setting, And Participants: This case series included 173 patients with angiographically confirmed SCAD enrolled between January 1, 2015, and December 31, 2019. Imaging of extracoronary arterial beds was performed by magnetic resonance angiography (MRA). Forty-one healthy individuals were recruited to serve as controls for blinded interpretation of MRA findings. Patients were recruited from the UK national SCAD registry, which enrolls throughout the UK by referral from the primary care physician or patient self-referral through an online portal. Participants attended the national SCAD referral center for assessment and MRA.

Exposures: Both patients with SCAD and healthy controls underwent head-to-pelvis MRA (median time between SCAD event and MRA, 1 [IQR, 1-3] year).

Main Outcome And Measures: The diagnosis of FMD, arterial dissections, and aneurysms was established according to the International FMD Consensus. Arterial tortuosity was assessed both qualitatively (presence or absence of an S curve) and quantitatively (number of curves ≥45%; tortuosity index).

Results: Of the 173 patients with SCAD, 167 were women (96.5%); mean (SD) age at diagnosis was 44.5 (7.9) years. The prevalence of FMD was 31.8% (55 patients); 16 patients (29.1% of patients with FMD) had involvement of multiple vascular beds. Thirteen patients (7.5%) had extracoronary aneurysms and 3 patients (1.7%) had dissections. The prevalence and degree of arterial tortuosity were similar in patients and controls. In 43 patients imaged with both computed tomographic angiography and MRA, the identification of clinically significant remote arteriopathies was similar. Over a median 5-year follow-up, there were 2 noncardiovascular-associated deaths and 35 recurrent myocardial infarctions, but there were no primary extracoronary vascular events.

Conclusions And Relevance: In this case series with blinded analysis of patients with SCAD, severe multivessel FMD, aneurysms, and dissections were infrequent. The findings of this study suggest that, although brain-to-pelvis imaging allows detection of remote arteriopathies that may require follow-up, extracoronary vascular events appear to be rare.
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http://dx.doi.org/10.1001/jamacardio.2021.4690DOI Listing
November 2021

Clinical Significance of Partial Anomalous Pulmonary Venous Connections (Isolated and Atrial Septal Defect Associated) Determined by Cardiovascular Magnetic Resonance.

Circ Cardiovasc Imaging 2021 08 13;14(8):e012371. Epub 2021 Aug 13.

Cardiology Department & Cardiovascular Research Centre (S.H., B.A., C.M., G.T.G., A.J.B., F.A., S.K.P., S.V.B.-N., M.A.G., R.H.M., D.J.P., C.I.).

Background: Partial anomalous venous connections (PAPVC) are associated with left to right shunting and right heart dilatation. Identification of PAPVC has increased with widespread use of cross-sectional imaging modalities. However, management strategies are mostly based on expert opinion given the scarcity of data from large series. We aimed to define types and significance of isolated and atrial septal defect (ASD) associated PAPVC detected by cardiovascular magnetic resonance.

Methods: We retrospectively reviewed our cardiovascular magnetic resonance database from 2002 to 2018 to identify isolated or ASD-associated PAPVC cases.

Results: A total of 215 patients (median age 46 years; range, 6-83) with isolated or ASD-associated PAPVC were identified among 102 135 clinical cardiovascular magnetic resonance studies. Of these, 104 were isolated and 111 were associated with an ASD. Anomalous connection of right upper pulmonary vein was the most common single venous anomaly (99/215), but in the isolated PAPVC group there were more anomalous left than right upper pulmonary veins (39 versus 34). The Qp/Qs was significantly higher for isolated anomalous single right upper pulmonary vein than left upper pulmonary vein (1.6 versus 1.4 respectively; =0.01) as were right ventricular end-diastolic volumes (113.7±30.9 versus 90 [57-157] mL/m, =0.004). In the PAPVC with an ASD group, sinus venosus ASDs (82%) were associated with right-sided PAPVCs while both right and left-sided venous anomalies were seen in secundum ASDs (18%). In a substantial number of patients (30 out of 91) with sinus venosus ASDs, PAPVCs were more complex and involved more than a single anomalous right upper pulmonary vein; and in 5 patients with ASD, PAPVC was identified only after the ASD closure.

Conclusions: This large series provides descriptive and hemodynamic features for isolated and ASD-associated PAPVCs. Anomalous isolated right upper pulmonary vein may cause a significant shunt (Qp/Qs >1.5). PAPVC associated with sinus venosus and secundum ASDs might be more complex than a single anomalous pulmonary vein and missed before ASD correction.
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http://dx.doi.org/10.1161/CIRCIMAGING.120.012371DOI Listing
August 2021

Processing Body Image on Social Media: Gender Differences in Adolescent Boys' and Girls' Agency and Active Coping.

Front Psychol 2021 21;12:626763. Epub 2021 May 21.

School of Psychology, Trinity College Dublin, Dublin, Ireland.

Although scholars continue to debate the influence of social media on body image, increased social media use, especially engaging in appearance-related behaviors may be a potential risk factor for body dissatisfaction in adolescents. Little research has investigated how adolescents process appearance-related content and the potential strategies they use to protect body image perceptions on social media. To investigate coping strategies used by adolescents, four qualitative focus groups were conducted with 29 adolescents (23 girls) aged 15-16 years ( = 15.31, = 0.47) in mixed-gender Irish secondary schools. Thematic analysis revealed that adolescents employed many different behavioral strategies such as avoiding negative content and selecting positive content. Cognitive processing strategies such as critically evaluating body-related content, psychologically distancing from and positively reframing challenging content were also used, although less frequently. Boys appeared to exhibit greater positive agency over their bodies and social media use and tended to use more active coping styles than girls. Efforts to promote body image on social media such as body positive pages and exposing artificial social media content were considered limited in their effectiveness.
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http://dx.doi.org/10.3389/fpsyg.2021.626763DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8175666PMC
May 2021

Association of individual aortic leaflet calcification on paravalvular regurgitation and conduction abnormalities with self-expanding trans-catheter aortic valve insertion.

Quant Imaging Med Surg 2021 May;11(5):1970-1982

Royal Brompton and Harefield NHS Foundation Trust, London, UK.

Background: Complication rates of paravalvular aortic regurgitation (PVR) and permanent pacemaker insertion remain high in patients undergoing trans-catheter aortic valve insertion for severe aortic stenosis. The spatial distribution of calcium between individual aortic valve leaflets, and its potential role in these complications is gaining interest. We aimed to assess the accuracy of individual aortic valve leaflet calcium quantification, and to determine its effect on the frequency of these complications.

Methods: This was a retrospective study of 251 patients who underwent trans-catheter aortic valve insertion using the Evolut RTM valve. The off-line Terarecon software platform was used for Agatston scoring the short axis views.

Results: There was a correlation between the sum of the individual leaflet and the total aortic valve calcium score. There was a univariate association between an increase [per 100 Agatston unit (AU)] in both right coronary leaflet (RCL) and left coronary leaflet (LCL) calcium with the risk of PVR. There was an association between an increase in LCL calcium score (per 100 AU) and need for post-implantation balloon aortic valvuloplasty (BAV). There was no association between individual leaflet calcification on the risk of permanent pacemaker insertion.

Conclusions: This study supports the idea that a quantifiable and reproducible method of individual valve leaflet calcification score may serve as an independent risk factor for paravalvular regurgitation, beyond visual assessment of asymmetry. However, the same may not be true of spatial calcium distribution and permanent pacemaker implantation (PPI).
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http://dx.doi.org/10.21037/qims-20-1122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8047340PMC
May 2021

Dual-Energy CT Pulmonary Angiography (DECTPA) Quantifies Vasculopathy in Severe COVID-19 Pneumonia.

Radiol Cardiothorac Imaging 2020 Oct 29;2(5):e200428. Epub 2020 Oct 29.

Department of Imaging, Royal Brompton Hospital, London, UK (C.A.R., S.R.D., C.M., D.L.L., S.M., T.S., E.S., S.P.P, A.D.); Imperial College London, London, UK (N.J.); Anaesthesia and Critical Care, Royal Brompton Hospital, London, UK (S.P., C.B., B.V.P.); Department of Haematology, Imperial College London, London, UK and Department of Haematology, Royal Brompton Hospital, London, UK (D.J.A).

Background: The role of dual energy computed tomographic pulmonary angiography (DECTPA) in revealing vasculopathy in coronavirus disease 2019 (COVID-19) has not been fully explored.

Purpose: To evaluate the relationship between DECTPA and disease duration, right ventricular dysfunction (RVD), lung compliance, D-dimer and obstruction index in COVID-19 pneumonia.

Materials And Methods: This institutional review board approved this retrospective study, and waived the informed consent requirement. Between March-May 2020, 27 consecutive ventilated patients with severe COVID-19 pneumonia underwent DECTPA to diagnose pulmonary thrombus (PT); 11 underwent surveillance DECTPA 14 ±11.6 days later. Qualitative and quantitative analysis of perfused blood volume (PBV) maps recorded: i) perfusion defect 'pattern' (wedge-shaped, mottled or amorphous), ii) presence of PT and CT obstruction index (CTOI) and iii) PBV relative to pulmonary artery enhancement (PBV/PAenh); PBV/PAenh was also compared with seven healthy volunteers and correlated with D-Dimer and CTOI.

Results: Amorphous (n=21), mottled (n=4), and wedge-shaped (n=2) perfusion defects were observed (M=20; mean age=56 ±8.7 years). Mean extent of perfusion defects=36.1%±17.2. Acute PT was present in 11/27(40.7%) patients. Only wedge-shaped defects corresponded with PT (2/27, 7.4%). Mean CTOI was 2.6±5.4 out of 40. PBV/PAenh (18.2 ±4.2%) was lower than in healthy volunteers (27 ±13.9%, p = 0.002). PBV/PAenh correlated with disease duration (β = 0.13, p = 0.04), and inversely correlated with RVD (β = -7.2, p = 0.001), persisting after controlling for confounders. There were no linkages between PBV/PAenh and D-dimer or CTOI.

Conclusion: Perfusion defects and decreased PBV/PAenh are prevalent in severe COVID-19 pneumonia. PBV/PAenh correlates with disease duration and inversely correlates with RVD. PBV/PAenh may be an important marker of vasculopathy in severe COVID-19 pneumonia even in the absence of arterial thrombus.
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http://dx.doi.org/10.1148/ryct.2020200428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7605077PMC
October 2020

Inferior vena cava aneurysm in a patient with Ehlers-Danlos syndrome.

J Cardiovasc Comput Tomogr 2021 Jul-Aug;15(4):e94-e95. Epub 2021 Mar 13.

Royal Brompton and Harefield NHS Foundation Trust, UK; National Heart and Lung Institute, Imperial College London, UK.

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http://dx.doi.org/10.1016/j.jcct.2021.03.002DOI Listing
March 2021

Prevalence of Thrombotic Complications in ICU-Treated Patients With Coronavirus Disease 2019 Detected With Systematic CT Scanning.

Crit Care Med 2021 05;49(5):804-815

Royal Brompton Hospital, London, United Kingdom.

Objectives: Severe coronavirus disease 2019 is associated with an extensive pneumonitis and frequent coagulopathy. We sought the true prevalence of thrombotic complications in critically ill patients with severe coronavirus disease 2019 on the ICU, with or without extracorporeal membrane oxygenation.

Design: We undertook a single-center, retrospective analysis of 72 critically ill patients with coronavirus disease 2019-associated acute respiratory distress syndrome admitted to ICU. CT angiography of the thorax, abdomen, and pelvis were performed at admission as per routine institution protocols, with further imaging as clinically indicated. The prevalence of thrombotic complications and the relationship with coagulation parameters, other biomarkers, and survival were evaluated.

Setting: Coronavirus disease 2019 ICUs at a specialist cardiorespiratory center.

Patients: Seventy-two consecutive patients with coronavirus disease 2019 admitted to ICU during the study period (March 19, 2020, to June 23, 2020).

Interventions: None.

Measurements And Main Results: All but one patient received thromboprophylaxis or therapeutic anticoagulation. Among 72 patients (male:female = 74%; mean age: 52 ± 10; 35 on extracorporeal membrane oxygenation), there were 54 thrombotic complications in 42 patients (58%), comprising 34 pulmonary arterial (47%), 15 peripheral venous (21%), and five (7%) systemic arterial thromboses/end-organ embolic complications. In those with pulmonary arterial thromboses, 93% were identified incidentally on first screening CT with only 7% suspected clinically. Biomarkers of coagulation (e.g., d-dimer, fibrinogen level, and activated partial thromboplastin time) or inflammation (WBC count, C-reactive protein) did not discriminate between patients with or without thrombotic complications. Fifty-one patients (76%) survived to discharge; 17 (24%) patients died. Mortality was significantly greater in patients with detectable thrombus (33% vs 10%; p = 0.022).

Conclusions: There is a high prevalence of thrombotic complications, mainly pulmonary, among coronavirus disease 2019 patients admitted to ICU, despite anticoagulation. Detection of thrombus was usually incidental, not predicted by coagulation or inflammatory biomarkers, and associated with increased risk of death. Systematic CT imaging at admission should be considered in all coronavirus disease 2019 patients requiring ICU.
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http://dx.doi.org/10.1097/CCM.0000000000004890DOI Listing
May 2021

The mysterious needle in the heart: a case report.

Eur Heart J Case Rep 2020 Jun 3;4(3):1-4. Epub 2020 May 3.

Department of Cardiovascular Magnetic Resonance, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK.

Background: A 53-year-old female with dyspnoea and atypical chest pain. Her electrocardiogram demonstrated a left bundle branch block, transthoracic echocardiogram demonstrated a mildly impaired left ventricle ejection fraction, and coronary angiogram revealed unobstructed coronary arteries. She was referred for cardiovascular magnetic resonance (CMR) for structural and functional assessment. Her imaging revealed an unexpected finding of an off-resonance artefact within the ventricle wall. This material was secondary to a ferromagnetic material.

Case Summary: Chest X ray and computer tomography confirmed a needle-shaped structure in the ventricle wall. Understanding the basis of this off-resonance artefact aided in a new diagnosis, raised questions on the origin of the material, patient safety, and implementation of corrective strategies to optimize image acquisition.

Discussion: The continued development of CMR is revolutionizing our ability to establish diagnosis and guide patient treatment. The CMR sequences can be prone to artefact. This case highlights the importance of understanding the basis of CMR artefacts.
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http://dx.doi.org/10.1093/ehjcr/ytaa083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7534165PMC
June 2020

The effects of eating disorders in pregnancy on mother and baby: a review.

Psychiatr Danub 2019 Sep;31(Suppl 3):615-618

Sidney Sussex Cambridge, School of Clinical Medicine, University of Cambridge, Cambridge, UK.

The psychological and physiological interaction between anorexia and the pregnant state has a large intrapartum and postpartum impact on mother and baby. Current research has attempted to discern the short and long term effects of eating disorders (EDs) on pregnancy as well as mother and baby-related sequelae; however little is understood about which management strategies are likely to prove most successful in mitigating these risks. The incidence and effect of low pre-pregnancy body mass index (BMI) on obstetric outcomes, and possible health complications in the future child, has attracted widespread attention. Especially concerning is the fact that it has long been known that the incidence of EDs in women of childbearing age is not only the highest out of all age categories but also is on an increasing trajectory. This paper aims to highlight the recent evidence underpinning the management of pregnant women with EDs in the light of the discussed short and long term effects of the disorders on mother and baby. We shall focus on those women who have a previous diagnosis of an ED prior to being pregnant. Particular attention will be paid to those studies considering anorexia nervosa. We argue for the use of early intervention strategies for the management of pregnant women with eating disorders, and for the use of a multidisciplinary approach in the treatment of these patients with complex problems.
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September 2019

The wider effects of Paternal Post Natal Depression: An overview.

Psychiatr Danub 2019 Sep;31(Suppl 3):613-614

Sidney Sussex College, University of Cambridge, Cambridge UK,

Paternal Post Natal Depression (PPND), although becoming more prevalent, is still poorly recognised. Unfortunately, its effects and negative outcomes have not been as widely researched as that of maternal postnatal depression. PPND can affect the fathers parenting style and lead to a negative effect on their child's behaviour and social development. Furthermore, depressed fathers may feel unsupported and this can lead to problems with the marital relationship and be associated with concurrent maternal postnatal depression. Moreover, support services and interventional therapy come at a cost to the health service and therefore treating PPND can impact the economy. Identifying the effects PPND has is important as implementing reliable screening measures and better education may prevent negative outcomes.
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September 2019

Transcatheter Aortic Valve Replacement to Treat Liver Decompensation.

CASE (Phila) 2018 Oct 9;2(5):186-191. Epub 2018 Aug 9.

Royal Brompton Hospital, London, United Kingdom.

•Critical aortic stenosis can cause severe biventricular disease.•Painless jaundice can present secondary to severe biventricular failure.•TAVR treats high-risk critical aortic stenosis.•TAVR can reverse clinical and biochemical congestive hepatopathy.•High-risk TAVR can be performed using circulatory support.
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http://dx.doi.org/10.1016/j.case.2018.04.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6200695PMC
October 2018

A Review of the Anatomical and Histological Attributes of the Left Atrial Appendage with Descriptive Pathological Examination of Morphology and Histology.

J Atr Fibrillation 2018 Apr 30;10(6):1650. Epub 2018 Apr 30.

Saint Vincent's University Hospital, Dublin.

The left atrial appendage (LAA) has a key role in the embolic complications of atrial fibrillation (AF). It has been studied extensively, from recent interest in the thrombotic implications of various LAA morphologies to LAA occlusion and ablation. We collected eleven post-mortem LAA samples for visual analysis, two were not included due to poor sample quality. On examination of the nine remaining samples, several common patterns of pectinate muscle orientation were noted. The LAA samples were noted to have a smooth circumferential neck of muscular tissue giving rise to a dominant singular smooth trunk of papillary muscle in 6 cases and two trunks in 3 cases. These trunks were either shallow (5 samples) or more muscular and raised (4 samples). Shallow trunks tended to be wider than the raised trunks and may even be circumferential (2 samples). The main trunk arborized to give off papillary muscle branches down to third or fourth order branches. The samples were visually assessed for the percentage of smooth papillary muscle versus non-papillary recesses and were found to have ≤50% smooth muscle in 3 samples, 50-75% in 3 samples and >75% in 3 samples. We performed histological analysis of further LAA samples collected during cardiac surgery in a parallel study. We identified a distinct pattern of myocyte orientation from the neck, mid-section and apical section of the LAA demonstrating arborization of myocyte fibers with minimal communication in distal segments of the LAA. We feel that this information may help understanding of the issues surrounding LAA ablation strategies.
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http://dx.doi.org/10.4022/jafib.1650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6009783PMC
April 2018

Incidence of thromboembolism following detection by trans-oesophageal echocardiography of left atrial thrombus.

Int J Cardiol Heart Vasc 2015 Sep 1;8:95-97. Epub 2015 Jun 1.

Department of Cardiology, St. Vincent's University Hospital, Dublin 4, Ireland.

Background: Left atrial appendage (LAA) thrombus is an accepted risk factor for ischemic stroke. Following a literature review we were unable to identify a study that determined the incidence of ischemic stroke in patients with a confirmed LAA thrombus. The purpose of this study was to establish the incidence of ischemic stroke in patients with a LAA thrombus confirmed on trans-oesophageal echocardiography (TOE).

Method: A ten year retrospective single centre study was conducted for the period March 2005 to February 2014 in St. Vincent's University Hospital, Ireland. All TOE studies performed during this period were reviewed. A chart review was carried out on any patient who had a LAA thrombus, left atrial (LA) thrombus or pre-thrombus state identified. Charts were reviewed for documented neurological deficits consistent with ischemic stroke or transient ischemic attack within six months following TOE study.

Results: Overall 1903 TOE studies were reviewed. A total of 67 TOE studies detected a LAA thrombus, LA thrombus or pre-thrombus state. In the days prior to TOE, an ischemic stroke had occurred in two of the patients. Following detection of thrombus or pre-thrombus state on TOE and optimization of oral anti-coagulation (OAC), no patient had an ischemic stroke over the subsequent six months.

Conclusion: This is the only study to date that has looked at the incidence of ischemic stroke following a confirmed LAA thrombus, LA thrombus or pre-thrombus state. This single centre study found low stroke rates over a six month follow-up period in patients with a confirmed LAA thrombus, LA thrombus or pre-thrombus state and optimization of OAC. Larger studies would be required to confirm these findings.
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http://dx.doi.org/10.1016/j.ijcha.2015.05.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5497287PMC
September 2015

Frequent inaccuracies in ABCD2 scoring in non-stroke specialists' referrals to a daily Rapid Access Stroke Prevention service.

J Neurol Sci 2013 Sep 17;332(1-2):30-4. Epub 2013 Jul 17.

Department of Neurology, The Adelaide and Meath Hospital/National Children's Hospital, Trinity College Dublin, Ireland.

The 'accuracy' of age, blood pressure, clinical features, duration and diabetes (ABCD(2)) scoring by non-stroke specialists referring patients to a daily Rapid Access Stroke Prevention (RASP) service is unclear, as is the accuracy of ABCD(2) scoring by trainee residents. In this prospective study, referrals were classified as 'confirmed TIAs' if the stroke specialist confirmed a clinical diagnosis of possible, probable or definite TIA, and 'non-TIAs' if patients had a TIA mimic or completed stroke. ABCD(2) scores from referring physicians were compared with scores by experienced stroke specialists and neurology/geriatric medicine residents at a daily RASP clinic; inter-observer agreement was examined. Data from 101 referrals were analysed (mean age=60.0years, 58% male). The median interval between referral and clinic assessment was 1day. Of 101 referrals, 52 (52%) were 'non-TIAs': 45 (86%) of 52 were 'TIA mimics' and 7 (14%) of 52 were completed strokes. There was only 'fair' agreement in total ABCD(2) scoring between referring physicians and stroke specialists (κ=0.37). Agreement was 'excellent' between residents and stroke specialists (κ=0.91). Twenty of 29 patients scored as 'moderate to high risk' (score 4-6) by stroke specialists were scored 'low risk' (score 0-3) by referring physicians. ABCD(2) scoring by referring doctors is frequently inaccurate, with a tendency to underestimate stroke risk. These findings emphasise the importance of urgent specialist assessment of suspected TIA patients, and that ABCD(2) scores by non-stroke specialists cannot be relied upon in isolation to risk-stratify patients. Inter-observer agreement in ABCD(2) scoring was 'excellent' between residents and stroke specialists, indicating short-term training may improve accuracy.
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http://dx.doi.org/10.1016/j.jns.2013.05.030DOI Listing
September 2013

Comprehensive interrogation of a minimalist synthetic CDR-H3 library and its ability to generate antibodies with therapeutic potential.

J Mol Biol 2013 May 19;425(10):1712-30. Epub 2013 Feb 19.

Pfizer, Global Biotherapeutics Technologies, Grange Castle Business Park, Clondalkin, Dublin 22, Ireland.

We have generated large libraries of single-chain Fv antibody fragments (>10(10) transformants) containing unbiased amino acid diversity that is restricted to the central combining site of the stable, well-expressed DP47 and DPK22 germline V-genes. Library WySH2A was constructed to examine the potential for synthetic complementarity-determining region (CDR)-H3 diversity to act as the lone source of binding specificity. Library WySH2B was constructed to assess the necessity for diversification in both the H3 and L3. Both libraries provided diverse, specific antibodies, yielding a total of 243 unique hits against 7 different targets, but WySH2B produced fewer hits than WySH2A when selected in parallel. WySH2A also consistently produced hits of similar quality to WySH2B, demonstrating that the diversification of the CDR-L3 reduces library fitness. Despite the absence of deliberate bias in the library design, CDR length was strongly associated with the number of hits produced, leading to a functional loop length distribution profile that mimics the biases observed in the natural repertoire. A similar trend was also observed for the CDR-L3. After target selections, several key amino acids were enriched in the CDR-H3 (e.g., small and aromatic residues) while others were reduced (e.g., strongly charged residues) in a manner that was specific to position, preferentially occurred in CDR-H3 stem positions, and tended towards residues associated with loop stabilization. As proof of principle for the WySH2 libraries to produce viable lead candidate antibodies, 114 unique hits were produced against Delta-like ligand 4 (DLL4). Leads exhibited nanomolar binding affinities, highly specific staining of DLL4+ cells, and biochemical neutralization of DLL4-NOTCH1 interaction.
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http://dx.doi.org/10.1016/j.jmb.2013.02.015DOI Listing
May 2013

Bile acids modulate the Golgi membrane fission process via a protein kinase Ceta and protein kinase D-dependent pathway in colonic epithelial cells.

Carcinogenesis 2010 Apr 21;31(4):737-44. Epub 2010 Jan 21.

Department of Clinical Medicine, Institute of Molecular Medicine, Trinity College Dublin, Ireland.

Deoxycholic acid (DCA) is a secondary bile acid that modulates signalling pathways in epithelial cells. DCA has been implicated in pathogenesis of colon carcinoma, particularly by activation of the protein kinase C (PKC) pathway. Ursodeoxycholic acid (UDCA), a tertiary bile acid, has been observed to have chemopreventive effects. The aim of this study was to investigate the effect of DCA and UDCA on the subcellular localization and activity of PKCeta and its downstream effects on Golgi structure in a colon cancer cell model. PKCeta expression was localized to the Golgi in HCT116 colon cancer cells. DCA induced fragmentation of the Golgi in these cells following activation of PKCeta and its downstream effector protein kinase D (PKD). Pretreatment of cells with UDCA or a glucocorticoid, dexamethasone, inhibited DCA-induced PKCeta/PKD activation and Golgi fragmentation. Knockdown of glucocorticoid receptor (GR) expression using small interfering RNA or inhibition using the GR antagonist mifepristone attenuated the inhibitory effect of UDCA on Golgi fragmentation. Elevated serum and faecal levels of DCA have been previously reported in patients with ulcerative colitis (UC) and colon cancer. Analysis of Golgi architecture in vivo using tissue microarrays revealed Golgi fragmentation in UC and colorectal cancer tissue. We have demonstrated that DCA can disrupt the structure of the Golgi, an organelle critical for normal cell function. Inhibition of this DCA-induced Golgi fragmentation by UDCA was mediated via the GR. This represents a potential mechanism of observed chemopreventive effects of UDCA in benign and malignant disease of the colon.
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http://dx.doi.org/10.1093/carcin/bgq011DOI Listing
April 2010

Affinity maturation of a humanized rat antibody for anti-RAGE therapy: comprehensive mutagenesis reveals a high level of mutational plasticity both inside and outside the complementarity-determining regions.

J Mol Biol 2009 May 13;388(3):541-58. Epub 2009 Mar 13.

Wyeth Research Ireland, Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.

Antibodies that neutralize RAGE (receptor for advanced glycation end products)-ligand interactions have potential therapeutic applications in both acute and chronic diseases. We generated XT-M4, a rat anti-RAGE monoclonal antibody that has in vivo efficacy in an acute sepsis model. This antibody was subsequently humanized. To improve the affinity of this antibody for the treatment of chronic indications, we used random and targeted mutagenesis strategies in combination with ribosome and phage-display technologies, respectively, to generate libraries of XT-M4 variants. We identified a panel of single-chain Fv antibody fragments (scFv's) that was improved up to 110-fold in a homogeneous time-resolved fluorescence competition assay against parental XT-M4 immunoglobulin G (IgG). After reformatting to bivalent scFv-Fc fusions and IgGs, we observed similar gains in potency in the same assay. Further analysis of binding kinetics as IgG revealed multiple variants with subnanomolar apparent affinity that was dictated primarily by improvements in the off-rate. All variants also had improved binding to cell surface-expressed human RAGE, and all retained, or had improved, apparent affinity for mouse RAGE. F100bL in V(H) (variable region of the heavy chain) complementarity-determining region 3 (CDR3) was one of a number of key mutations that correlated with affinity improvements and was independently identified by both mutagenesis strategies. Random mutagenesis coupled with ribosome display and high-throughput screening revealed an unexpectedly high level of mutational plasticity across the whole length of the humanized scFv, suggesting greater scope for structural optimization outside of the primary antigen-combining site defined by V(H) CDR3 and V(kappa) CDR3. In summary, our comprehensive mutagenesis approach not only achieved the desired affinity maturation of XT-M4 but also defined multiple mutational hotspots across the antibody sequence, provided an insight into the specificity-determining residues of the antibody paratope, and identified additional sites within the CDR loops where human germ-line amino acids may be introduced without affecting function.
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http://dx.doi.org/10.1016/j.jmb.2009.03.019DOI Listing
May 2009
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