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Hughes RK, Shiwani H, Rosmini S, Burke L, Pierce I, Castelletti S, Xue H, Kellman P, Lopes LR, Treibel T, Manisty C, Captur G, Davies R, Moon J. Improved diagnostic accuracy for apical hypertrophic cardiomyopathy. Eur Heart J 2022. [DOI: 10.1093/eurheartj/ehac544.1553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Introduction
The diagnosis of apical hypertrophic cardiomyopathy (ApHCM) is contingent on demonstrating apical maximum wall thickness (MWT) of ≥15mm; the same threshold as other HCM subtypes. However, the myocardium naturally tapers towards the apex in healthy individuals, so ≥15mm MWT is proportionately higher in the apex than in naturally thicker basal segments. Using cardiac magnetic resonance (CMR), relative ApHCM has been described (typical ECG features, loss of apical tapering, cavity obliteration but hypertrophy <15mm). Wall thickness measurement using machine learning now exceeds human performance.
Purpose
We aimed to redefine the optimal diagnostic threshold for ApHCM using segment-specific criteria based on a large cohort of healthy control subjects.
Methods
Segmental wall thickness was measured using healthy subjects from the UK Biobank using a clinically validated machine learning algorithm1,2. A normative reference range was established for all 16 segments, conditioned to body surface area (BSA), sex and age. Derived segment-specific wall thickness thresholds were used to define optimal disease thresholds for patients clinically managed with overt (MWT ≥15mm) and relative ApHCM (MWT <15mm, but typical ECG and imaging findings).
Results
4118 UK biobank subjects were used to define normal segmental thicknesses and reference ranges. These were applied to ApHCM (73 overt, 31 relative). There were no apical wall thickness age related differences. The upper limit of the 95% confidence interval corresponded to a combined maximum apical MWT for both males and females of 10.4mm using non-indexed measurement, or 5.6mm/m2 when indexed to BSA. Non-indexed segmental threshold identified 100% of ApHCM patients (true positives), 81% (25 of 31) relative ApHCM and 3% (115 of 4118) of healthy UK biobank subjects (false positives). Indexed segmental thresholds improved the diagnostic potential in relative ApHCM without an increase in false positives (100% of ApHCM patients, 84% (26 of 31) of relative ApHCM patients, and 3% healthy UK biobank (127 of 4118).
Conclusion
We propose new diagnostic criteria for ApHCM using segmental indexed apical wall thickness of >5.6 mm/m2 to better identify inappropriate apical hypertrophy in those whose wall thickness does not meet current criteria for diagnosis.
Funding Acknowledgement
Type of funding sources: Foundation. Main funding source(s): British Heart Foundation
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Affiliation(s)
- R K Hughes
- Barts Heart Centre , London , United Kingdom
| | - H Shiwani
- Barts Heart Centre , London , United Kingdom
| | - S Rosmini
- King's College Hospital , London , United Kingdom
| | - L Burke
- University College London , London , United Kingdom
| | - I Pierce
- Barts Heart Centre , London , United Kingdom
| | - S Castelletti
- Italian Auxological Institute San Luca Hospital , Milan , Italy
| | - H Xue
- National Institutes of Health , Bethesda , United States of America
| | - P Kellman
- National Institutes of Health , Bethesda , United States of America
| | - L R Lopes
- Barts Heart Centre , London , United Kingdom
| | - T Treibel
- Barts Heart Centre , London , United Kingdom
| | - C Manisty
- Barts Heart Centre , London , United Kingdom
| | - G Captur
- University College London , London , United Kingdom
| | - R Davies
- University College London , London , United Kingdom
| | - J Moon
- Barts Heart Centre , London , United Kingdom
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Malcolmson JW, Hughes RK, Shiwani H, Husselbury T, Procter W, Godec T, Davies R, Omahony C, Moon J, Dhinoja MB, Petersen SE, Mohiddin SA. Cardiac magnetic resonance imaging predictors of ventricular arrhythmia in mid-cavity obstructive hypertrophic cardiomyopathy. Eur Heart J 2022. [DOI: 10.1093/eurheartj/ehac544.257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Background/Introduction
Left ventricular (LV) mid-cavity obstruction (LVMCO) in hypertrophic cardiomyopathy (HCM) is an uncommon phenotypic feature predisposed to the formation of myocardial fibrosis and apical aneurysms (LVAA). These features may be independently proarrhythmic, and LVAA is considered a class 2a indication for implantable cardioverter defibrillator (ICD) in current US, but not European guidelines for the primary prevention of sudden cardiac death (SCD). Cardiac magnetic resonance (CMR) imaging is the preferred modality for detecting these and other phenotypic features critical to SCD risk assessment.
Purpose
To assess the ability of CMR imaging parameters to predict occurrence of non-sustained ventricular tachycardia (NSVT) in HCM patients with Doppler-derived evidence of LVMCO.
Methods
Multi-modality imaging records were retrospectively assessed to identify HCM patients with Doppler-LVMCO and CMR scans. CMR images were assessed by an investigator blinded to clinical status. Late gadolinium enhancement (LGE) was quantified using the full-width, half-maximum technique. CMR imaging parameters were assessed for predictive ability using Cox proportional hazards during univariate and multivariate analyses, accounting for time to event (NSVT or censorship of follow-up).
Results
The study cohort included 58 patients (57±11 years, 74% male) with a median follow-up of 6.2 (IQR 4.3) years. Mean mid-cavity gradient was 33±23 mmHg. NSVT was detected in 27/58 (47%) patients, was 4 beats or longer in 23/27 (85%) and was monomorphic in 21/27 (77%).
On univariate analysis, predictors of NSVT during follow-up include LV mass index (HR 1.02, 95% CI 1.00–1.04, p=0.03), LGE in grams (HR 1.04, 95% CI 1.01–1.06, p=0.005), and LVAA (HR 2.57, 95% CI 1.14–5.79, p=0.023). After multivariate adjustment (Table 2), none were significantly associated.
Conclusions
In LVMCO, magnitude of LV hypertrophy, extent of LGE and the presence of an apical aneurysm may not be independent predictors of ventricular arrhythmias. SCD algorithms based on qualitative assessments of these features may overestimate risk.
Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): National Institute of Health Research (NIHR)
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Affiliation(s)
- J W Malcolmson
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - R K Hughes
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - H Shiwani
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - T Husselbury
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - W Procter
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - T Godec
- William Harvey Research Institute , London , United Kingdom
| | - R Davies
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - C Omahony
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - J Moon
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - M B Dhinoja
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - S E Petersen
- Barts Health NHS Trust, Cardiology , London , United Kingdom
| | - S A Mohiddin
- Barts Health NHS Trust, Cardiology , London , United Kingdom
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Shiwani H, Hughes RK, Camaioni C, Augusto JB, Knott K, Rosmini S, Burke L, Pierce I, Moon JC, Davies RH. Asymmetric septal thickening is observed in hypertrophic cardiomyopathy mutation carriers without left ventricular hypertrophy: insights from AI analysis. Eur Heart J Cardiovasc Imaging 2022. [DOI: 10.1093/ehjci/jeac141.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Dr Hughes is supported by the British Heart Foundation (grant number FS/17/82/33222).
Background
Hypertrophic cardiomyopathy (HCM) is a common inherited cardiac disease characterised by left ventricular hypertrophy (LVH), often, with asymmetric septal thickening. Despite the prevalence of inherited mutations present in >50% of cases, there is variable phenotypic expression in those with abnormal sarcomere protein genes. In individuals with abnormal genes but without LVH, we hypothesised that there is subtle asymmetric septal hypertrophy, detectable by the increased precision offered by an artificial intelligence (AI) tool for measuring wall thickness.
Purpose
We explored the septal-lateral ratio measured by AI in individuals with an identified genotype but no left ventricular hypertrophy as a component of sub-clinical HCM.
Methods
43 individuals with identified genotype, but no left ventricular hypertrophy (G+LVH-) and 97 age-, sex- and disease-matched controls underwent CMR. Patients were excluded if they had a maximum wall thickness (MWT) of ≥13mm. A clinically validated AI tool was used to measure the MWT, for each segment in the 16-segment AHA model. The septal-lateral ratio was calculated using the septal segment with the largest MWT and the lateral segment with the largest MWT.
Results
The mean septal-lateral ratio of the G+LVH- patients was 1.22 (SD 0.22) and the mean septal-lateral ratio of the matched controls was 1.14 (SD 0.15) with a statistically significant mean difference of 0.08 (p=0.01). There was no significant difference between the MWT of the G+LVH- patients at 10.3mm (SD 2.2) and healthy volunteers at 10.1mm (SD 1.8) (p = 0.61).
Conclusion
G+LVH- patients have a 7% increase in their septal-lateral ratio compared with age-matched controls despite the lack of difference in the MWT. Using increased precision offered by AI, early features of HCM can be observed in patients without overt LVH.
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Affiliation(s)
- H Shiwani
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - R K Hughes
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - C Camaioni
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - J B Augusto
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - K Knott
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - S Rosmini
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - L Burke
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - I Pierce
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - J C Moon
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - R H Davies
- University College London , London , United Kingdom of Great Britain & Northern Ireland
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Shiwani H, Hughes RK, Camaioni C, Augusto JB, Knott K, Rosmini S, Khoury S, Malcolmson J, Kellman P, Xue H, Burke L, Pierce I, Moon JC, Davies RH. Improving the diagnostic accuracy of apical hypertrophic cardiomyopathy using machine learning. Eur Heart J Cardiovasc Imaging 2022. [DOI: 10.1093/ehjci/jeac141.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Dr Hughes is supported by the British Heart Foundation (grant number FS/17/82/33222).
Introduction
The imaging criteria for diagnosis of apical hypertrophic cardiomyopathy (ApHCM) is a maximum wall thickness (MWT) ≥15mm. CMR enables detection of subtle phenotypic features (e.g. loss of apical tapering, cavity obliteration) and coupled with characteristic electrocardiogram changes, ApHCM can be diagnosed without overt hypertrophy. However, these patients are not captured by current diagnostic criteria.
Purpose
We sought to use a machine learning tool to quantify wall thickness and identify patients with ‘relative’ ApHCM that do not reach current diagnostic thresholds.
Methods
CMR images from 4118 healthy participants from the UK Biobank were segmented automatically with a clinically validated machine learning algorithm and wall thickness measured at all point in the myocardium by solving a solution to Laplace’s equation. MWT were pooled into 16 AHA segments and indexed to body surface area (BSA). The non-indexed and indexed segmental upper limit of normal was calculated as the mean + 3 standard deviations (the equivalent of 95% confidence interval after correcting for multiple [16] comparisons using the Bonferroni method).
Results
73 overt ApHCM subjects (MWT>15mm) and 31 relative ApHCM subjects underwent CMR scanning. In healthy controls, the non-indexed (and indexed) upper limits were calculated for the apical-anterior 10.2mm (5.2 mm/m2), apical-septal 11.1mm (5.6 mm/m2), apical-inferior 10.5mm (5.3 mm/m2) and apical-lateral 10.1mm (5.2 mm/m2) segments. With a non-indexed cut-off, all (73 of 73) overt ApHCM and 84% (26 of 31) relative ApHCM were classified as having an abnormally thick apex. 3% (127 of 4118) of the healthy UK Biobank cohort were classified as abnormal, as expected. Using an indexed cut-off, all overt ApHCM and 87% (27/31) relative ApHCM were classified as abnormal, and 3% (123 of 4118) of the healthy UK Biobank cohort were misclassified.
Conclusion
We can successfully classify 87% of relative ApHCM patients from a normative reference range derived from a large cohort of healthy patients – a significant improvement on existing methods. We show that the specificity and sensitivity is increased when MWT is indexed to BSA. For practical clinical application, we recommend a cut-off of 10mm or an indexed cut-off of 5mm/m2 in any apical segment to diagnose apical LVH. Overt and relative apical HCM examplesHealthy controls AHA maps (non-indexed)
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Affiliation(s)
- H Shiwani
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - R K Hughes
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - C Camaioni
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - J B Augusto
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - K Knott
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - S Rosmini
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - S Khoury
- St George's University of London, Cardiovascular Clinical and Academic Group , London , United Kingdom of Great Britain & Northern Ireland
| | - J Malcolmson
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - P Kellman
- National Heart Lung and Blood Institute , Bethesda , United States of America
| | - H Xue
- National Heart Lung and Blood Institute , Bethesda , United States of America
| | - L Burke
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - I Pierce
- Barts Heart Centre , London , United Kingdom of Great Britain & Northern Ireland
| | - J C Moon
- University College London , London , United Kingdom of Great Britain & Northern Ireland
| | - R H Davies
- University College London , London , United Kingdom of Great Britain & Northern Ireland
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5
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Knott K, Augusto JB, Nordin S, Kozor R, Camaioni C, Xue H, Hughes RK, Manisty C, Brown LAE, Ramaswami U, Hughes D, Kellman P, Plein S, Moon JC. 304Quantitative perfusion mapping in Fabry disease. Eur Heart J Cardiovasc Imaging 2019. [DOI: 10.1093/ehjci/jez119.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- K Knott
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - J B Augusto
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - S Nordin
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - R Kozor
- University of Sydney, Sydney, Australia
| | - C Camaioni
- Barts Health NHS Trust, London, United Kingdom of Great Britain & Northern Ireland
| | - H Xue
- National Institutes of Health, Bethesda, United States of America
| | - R K Hughes
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - C Manisty
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - L A E Brown
- University of Leeds, Leeds, United Kingdom of Great Britain & Northern Ireland
| | - U Ramaswami
- Royal Free Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - D Hughes
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - P Kellman
- National Institutes of Health, Bethesda, United States of America
| | - S Plein
- University of Leeds, Leeds, United Kingdom of Great Britain & Northern Ireland
| | - J C Moon
- University College London, London, United Kingdom of Great Britain & Northern Ireland
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6
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Hughes RK, Camaioni C, Knott KD, Quinn E, Captur G, Syrris P, Kellman P, Elliott PM, Mohiddin S, Xue H, Lopes L, Moon J. 267Myocardial perfusion defects in genotype-positive hypertrophic cardiomyopathy without left ventricular hypertrophy. Eur Heart J Cardiovasc Imaging 2019. [DOI: 10.1093/ehjci/jez101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- R K Hughes
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - C Camaioni
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - K D Knott
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - E Quinn
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - G Captur
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - P Syrris
- University College London, London, United Kingdom of Great Britain & Northern Ireland
| | - P Kellman
- National Institutes of Health, Bethesda, United States of America
| | - P M Elliott
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - S Mohiddin
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - H Xue
- National Institutes of Health, Bethesda, United States of America
| | - L Lopes
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
| | - J Moon
- St Bartholomew"s Hospital, London, United Kingdom of Great Britain & Northern Ireland
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Hughes RK, Belfield EJ, Casey R. CYP74C3 and CYP74A1, plant cytochrome P450 enzymes whose activity is regulated by detergent micelle association, and proposed new rules for the classification of CYP74 enzymes. Biochem Soc Trans 2007; 34:1223-7. [PMID: 17073790 DOI: 10.1042/bst0341223] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
CYP74C3 (cytochrome P450 subfamily 74C3), an HPL (hydroperoxide lyase) from Medicago truncatula (barrel medic), and CYP74A1, an AOS (allene oxide synthase) from Arabidopsis thaliana, are key membrane-associated P450 enzymes in plant oxylipin metabolism. Both recombinant detergent-free enzymes are monomeric proteins with dual specificity and very low enzyme activity that can be massively activated with detergent. This effect is a result of the formation of a complex between the protein monomer and a single detergent micelle and, in the case of CYP74A1, has a major effect on the substrate specificity of the enzyme. Association with a detergent micelle without an effect on protein oligomeric state represents a new mechanism of activation for membrane-associated P450 enzymes. This may represent a second unifying feature of CYP74 enzymes, in addition to their known differences in reaction mechanism, which separates them functionally from more classical P450 enzymes. Highly concentrated and monodispersed samples of detergent-free CYP74C3 and CYP74A1 proteins should be suitable for structural resolution. On the basis of recent evidence for incorrect assignment of CYP74 function, using the current rules for CYP74 classification based on sequence relatedness, we propose an alternative based on substrate and product specificity for debate and discussion.
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Affiliation(s)
- R K Hughes
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
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Abstract
We have produced a model to define the linoleate-binding pocket of pea 9/13-lipoxygenase and have validated it by the construction and characterization of eight point mutants. Three of the mutations reduced, to varying degrees, the catalytic centre activity (kcat) of the enzyme with linoleate. In two of the mutants, reductions in turnover were associated with changes in iron-coordination. Multiple sequence alignments of recombinant plant and mammalian lipoxygenases of known positional specificity, and the results from numerous other mutagenesis and modelling studies, have been combined to discuss the possible role of the mutated residues in pea 9/13-lipoxygenase catalysis. A new nomenclature for recombinant plant lipoxygenases based on positional specificity has subsequently been proposed. The null-effect of mutating pea 9/13-lipoxygenase at the equivalent residue to that which controlled dual positional specificity in cucumber 13/9-lipoxygenase, strongly suggests that the mechanisms controlling dual positional specificity in pea 9/13-lipoxygenase and cucumber 13/9-lipoxygenase are different. This was supported from modelling of another isoform of pea lipoxygenase, pea 13/9-lipoxygenase. Dual positional specificity in pea lipoxygenases is more likely to be determined by the degree of penetration of the methyl terminus of linoleate and the volume of the linoleate-binding pocket rather than substrate orientation. A single model for positional specificity, that has proved to be inappropriate for arachidonate-binding to mammalian 5-, 12- and 15-lipoxygenases, would appear to be true also for linoleate-binding to plant 9- and 13-lipoxygenases.
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Affiliation(s)
- R K Hughes
- John Innes Centre, Norwich Research Park, Norwich, UK.
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9
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Hughes RK, West SI, Hornostaj AR, Lawson DM, Fairhurst SA, Sanchez RO, Hough P, Robinson BH, Casey R. Probing a novel potato lipoxygenase with dual positional specificity reveals primary determinants of substrate binding and requirements for a surface hydrophobic loop and has implications for the role of lipoxygenases in tubers. Biochem J 2001; 353:345-55. [PMID: 11139400 PMCID: PMC1221578 DOI: 10.1042/0264-6021:3530345] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A new potato tuber lipoxygenase full-length cDNA sequence (lox1:St:2) has been isolated from potato tubers and used to express in Escherichia coli and characterize a novel recombinant lipoxygenase (potato 13/9-lipoxygenase). Like most plant lipoxygenases it produced carbonyl compounds from linoleate (the preferred substrate) and was purified in the Fe(II) (ferrous) state. Typical of other potato tuber lipoxygenases, it produced 5-HPETE [5(S)-hydroperoxy-(6E, 8Z, 11Z, 14Z)-eicosatetraenoic acid] from arachidonate. In contrast to any other potato tuber lipoxygenase, it exhibited dual positional specificity and produced roughly equimolar amounts of 13- and 9-hydroperoxides (or only a slight molar excess of 9-hydroperoxides) from linoleate. We have used a homology model of pea 9/13-lipoxygenase to superimpose and compare the linoleate-binding pockets of different potato lipoxygenases of known positional specificity. We then tested this model by using site-directed mutagenesis to identify some primary determinants of linoleate binding to potato 13/9-lipoxygenase and concluded that the mechanism determining positional specificity described for a cucumber lipoxygenase does not apply to potato 13/9-lipoxygenase. This supports our previous studies on pea seed lipoxygenases for the role of pocket volume rather than inverse orientation as a determinant of dual positional specificity in plant lipoxygenases. We have also used deletion mutagenesis to identify a critical role in catalysis for a surface hydrophobic loop in potato 13/9-lipoxygenase and speculate that this may control substrate access. Although potato 13/9-lipoxygenase represents only a minor isoform in tubers, such evidence for a single lipoxygenase species with dual positional specificity in tubers has implications for the proposed role of potato lipoxygenases in the plant.
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Affiliation(s)
- R K Hughes
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, U.K
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10
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Wu Z, Robinson DS, Hughes RK, Casey R, Hardy D, West SI. Co-oxidation of beta-carotene catalyzed by soybean and recombinant pea lipoxygenases. J Agric Food Chem 1999; 47:4899-906. [PMID: 10606550 DOI: 10.1021/jf9901690] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A number of products including apocarotenal, epoxycarotenal, apocarotenone, and epoxycarotenone generated by lipoxygenase (LOX) catalyzed co-oxidation of beta-carotene have been tentatively identified through the use of GC/MS and HPLC combined with photodiode array detection. Because of the large number of high molecular weight products detected and their probable chemical structures, a co-oxidation mechanism is proposed that involves random attack along the alkene chain of the carotenoid by a LOX-generated linoleoylperoxyl radical. It is suggested that a direct release from the enzyme of the radical, which initiates the co-oxidation of beta-carotene, is greater for pea LOX-3 than for pea LOX-2 or soybean LOX-1. It is proposed that further products may be formed by free radical propagated reactions and that the formation of 1,10- and 1,14-dicarbonyl compounds may arise by secondary oxidation of the primary products.
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Affiliation(s)
- Z Wu
- Biocatalysts Ltd., Pontypridd, Mid-Glamorgan CF37 5UT, United Kingdom
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11
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Hughes RK, Wu Z, Robinson DS, Hardy D, West SI, Fairhurst SA, Casey R. Characterization of authentic recombinant pea-seed lipoxygenases with distinct properties and reaction mechanisms. Biochem J 1998; 333 ( Pt 1):33-43. [PMID: 9639559 PMCID: PMC1219552 DOI: 10.1042/bj3330033] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The two major isoforms of lipoxygenase (LOX-2 and LOX-3) from pea (Pisum sativum L. cv. Birte) seeds have been cloned and expressed from full-length cDNAs as soluble, active, non-fusion proteins in Escherichia coli. A comparison of both isoforms purified to apparent homogeneity from E. coli and pea seeds has confirmed the authenticity of the recombinant products and established the properties of the native enzymes. Despite 86% similarity at the amino acid sequence level, the enzymes have distinct properties. They have been characterized in terms of specific activity, Fe content, optimum pH, substrate and product specificity, apparent Km and Vmax for the preferred substrate, linoleic acid, and interfacial behaviour with linoleic acid. We have used this evidence, in addition to EPR spectroscopy of the hydroperoxide-activated enzymes and estimates of kcat/Km, to propose different reaction mechanisms for linoleic acid oxidation for the two isoforms. The differences relate primarily to carbonyl production from linoleic acid for which we propose a mechanism. This implicates the release of a peroxyl radical in an aerobic hydroperoxidase reaction, as the source of the carbonyl compounds formed by dismutation of the liberated peroxyl radical.
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Affiliation(s)
- R K Hughes
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, U.K.
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12
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Hughes RK, Perbal MC, Maule AJ, Hull R. Evidence for proteolytic processing of tobacco mosaic virus movement protein in Arabidopsis thaliana. Mol Plant Microbe Interact 1995; 8:658-665. [PMID: 7579611 DOI: 10.1094/mpmi-8-0658] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Two ecotypes of Arabidopsis thaliana were transformed with the gene encoding tobacco mosaic virus (TMV) movement protein (P30). P30 accumulated largely in a subcellular fraction containing cell wall components and as a soluble protein. The protein migrated in denaturing gels with an M(r) of 30K, significantly faster than P30 (M(r) approximately 34K) accumulating after expression in transgenic tobacco, Escherichia coli or Spodoptera frugiperda cells, or after virus multiplication in tobacco. The P30 from A. thaliana infected with TMV for 14 days comigrated with that from E. coli, but that from A. thaliana infected for 49 days was of the smaller size. The use of antisera specific for the N- or C-termini of P30 showed that in A. thaliana P30 was proteolytically processed at the N-terminus, a region essential for P30 function. The failure of these plants to complement a TMV P30 mutant indicated that processed P30 was nonfunctional, although the processing was not so rapid that it prevented the development of systemic infections with wild type TMV. The absence of detectable P30 phosphorylation in A. thaliana demonstrated that phosphorylation was not essential for movement protein function and suggested that this species may use proteolytic cleavage of the N-terminus as an alternative strategy to tobacco for deactivating P30.
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Affiliation(s)
- R K Hughes
- Department of Virus Research, John Innes Centre, Colney, Norwich, U.K
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Hughes RK, Doyle WA, Chovnick A, Whittle JR, Burke JF, Bray RC. Use of rosy mutant strains of Drosophila melanogaster to probe the structure and function of xanthine dehydrogenase. Biochem J 1992; 285 ( Pt 2):507-13. [PMID: 1637342 PMCID: PMC1132817 DOI: 10.1042/bj2850507] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The usefulness in structure/function studies of molybdenum-containing hydroxylases in work with rosy mutant strains of Drosophila melanogaster has been investigated. At least 23 such strains are available, each corresponding to a single known amino acid change in the xanthine dehydrogenase sequence. Sequence comparisons permit identification, with some certainty, of regions associated with the iron-sulphur centres and the pterin molybdenum cofactor of the enzyme. Procedures have been developed and rigorously tested for the assay in gel-filtered extracts of the flies, of different catalytic activities of xanthine dehydrogenase by the use of various oxidizing and reducing substrates. These methods have been applied to 11 different rosy mutant strains that map to different regions of the sequence. All the mutations studied cause characteristic activity changes in the enzyme. In general these are consistent with the accepted assignment of the cofactors to the different domains and with the known reactivities of the molybdenum, flavin and iron-sulphur centres. Most results are interpretable in terms of the mutation affecting electron transfer to or from one redox centre only. The activity data provide evidence that FAD and the NAD+/NADH binding sites are retained in mutants mapping to the flavin domain. Therefore, despite some indications from sequence comparisons, it is concluded that the structure of this domain of xanthine dehydrogenase cannot be directly related to that of other flavoproteins for which structural data are available. The data also indicate that the artificial electron acceptor phenazine methosulphate acts at the iron-sulphur centres and suggest that these centres may not be essential for electron transfer between molybdenum and flavin. The work emphasizes the importance of combined genetic and biochemical study of rosy mutant xanthine dehydrogenase variants in probing the structure and function of enzymes of this class.
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Affiliation(s)
- R K Hughes
- Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Brighton, U.K
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Hughes RK. Xanthine dehydrogenase from Drosophila melanogaster: purification and properties of the wild-type enzyme and of a variant lacking iron-sulfur centers. Biochemistry 1992; 31:3073-83. [PMID: 1313286 DOI: 10.1021/bi00127a007] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Xanthine dehydrogenase has been purified to homogeneity by conventional procedures from the wild-type strain of the fruit fly Drosophila melanogaster, as well as from a rosy mutant strain (E89----K, ry5231) known to carry a point mutation in the iron-sulfur domain of the enzyme. The wild-type enzyme had all the specific properties that are peculiar to the molybdenum-containing hydroxylases. It had normal contents of molybdenum, the pterin molybdenum cofactor, FAD, and iron-sulfur centers. EPR studies showed its molybdenum center to be quite indistinguishable from that of milk xanthine oxidase. As isolated, only about 10% of the enzyme was present in the functional form, with most or all of the remainder as the inactive desulfo form. It is suggested that this may be present in vivo. Extensive proteolysis accompanied by the development of oxidase activity took place during isolation, but dehydrogenase activity was retained. EPR properties of the reduced iron-sulfur centers, Fe-SI and Fe-SII, in the enzyme are very similar to those of the corresponding centers in milk xanthine oxidase. The E89----K mutant enzyme variant was in all respects closely similar to the wild-type enzyme, with the exception that it lacked both of the iron-sulfur centers. This was established both by its having the absorption spectrum of a simple flavoprotein and by the complete absence of EPR signals characteristic of iron-sulfur centers in the reduced enzyme. Despite the lack of iron-sulfur centers, the mutant enzyme had xanthine:NAD+ oxidoreductase activity indistinguishable from that of the wild-type enzyme. Stopped-flow measurements indicated that, as for the wild-type enzyme, reduction of the mutant enzyme was rate-limiting in turnover. Thus, the iron-sulfur centers appear irrelevant to the normal turnover of the wild-type enzyme with these substrates. However, activity to certain oxidizing substrates, particularly phenazine methosulfate, is abolished in the mutant enzyme variant. This is one of the first examples of deletion by genetic means of iron-sulfur centers from an iron-sulfur protein. The relevance of our findings both to the roles of iron-sulfur centers in other systems and to the nature of the oxidizing substrate for the Drosophila enzyme in vivo are briefly discussed.
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Affiliation(s)
- R K Hughes
- Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Brighton, U.K
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Hughes RK, Bennett B, Doyle WA, Burke JF, Chovnick A, Bray RC. Roles of molybdenum, FAD and iron-sulphur domains in molybdenum-containing hydroxylases: molecular genetic, kinetic and spectroscopic studies. Biochem Soc Trans 1991; 19:260S. [PMID: 1783109 DOI: 10.1042/bst019260s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- R K Hughes
- Biochemistry Laboratory, University of Sussex, Brighton
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Abstract
Two malignant fibrous histiocytomas arising primarily in the lung are described. The first was a large tumor of the right lower lobe in a 53-year-old man. The other tumor was found incidentally on routine roentgenograms in a 25-year-old woman and involved the left main pulmonary artery. The lesions could be resected but both patients developed early cerebral metastases. The neoplasms were predominantly fibroblastic, had a characteristic storiform pattern, and included large histiocytes with bizarre nuclei and a vacuolated cytoplasm. The ultrastructure of the cells in the fibroblastic areas was characterized by irregular nuclei and a cytoplasm with a well-developed endoplasmic reticulum and dilated cisternae. Some cells lacked the prominent endoplasmic reticulum of fibroblasts and others were characteristic histiocytes with numerous cytoplasmic lysosomes. The cases appear to be the first reported primary malignant fibrous histiocytomas of the lung.
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Tucker BL, Lindesmith GG, Stiles QR, Hughes RK, Meyer BW. Myocardial revascularization in patients 70 years of age and older. West J Med 1977; 126:179-83. [PMID: 306708 PMCID: PMC1237500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Myocardial revascularization has been carried out by us in 67 patients 70 years of age or older. Advanced coronary artery disease was found at angiography in more than two thirds of the patients. The postoperative morbidity and mortality compare very favorably with those in younger patients. The early and late mortality in the 67 patients was 4.5 percent and 6.0 percent, respectively. Fifty-seven survivors have been followed an average of 21 months; for most patients there has been a pronounced improvement in clinical classification. Properly selected, patients of advanced age can undergo successful revascularization surgical procedures. The adequacy of function of the left ventricle, proper timing of the surgical operation and an aggressive yet realistic approach seem to be major determinants for a good result.
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Stiles QR, Hughes RK, Lindesmith GG. The effectiveness of topical cardiac hypothermia. J Thorac Cardiovasc Surg 1977; 73:176-80. [PMID: 299902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The effectiveness of cooling the subendocardial myocardium by five different methods was evaluated in a group of 100 patients. The most effective and consistent method to cool the heart was by total body hypothermia with the heat exchanger in the cardiopulmonary bypass system. Myocardial temperature became equal to vena caval blood temperature after only a one minute lag. The least effective methods of myocardial cooling were those in which a bath of chilled fluid enveloped the outside surface of the heart, with and without aortic cross-clamping. The drop in ventricular septal temperature was so small that topical hypothermia, by itself, may be worthless. Two methods in wich chilled fluid was perfused through the coronary system produced a significant lowering of myocardial temperature. One of these methods employs coronary perfusion with a cold cardioplegic solution in addition to total body hypothermia. It is our current choice for myocardial protection during cross-clamping of the ascending aorta.
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Abstract
A simple method is described to correct saphenous vein bypass grafts that inadvertently have been made too long or too short or have become twisted. The essential feature of the technique is the use of a Satinsky vascular clamp to hold the divided ends of the vein and maintain their alignment during the repair. The most accessible portion of the vein is used as the site for the repair, leaving the aortic and coronary artery ends of the graft intact. While we have not had need to use the technique frequently, we have found it to be a simple method and believe it to be useful when such instances arise.
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Stiles QR, Lindesmith GG, Tucker BL, Hughes RK, Meyer BW. Experience with fifty repeat procedures for myocardial revascularization. J Thorac Cardiovasc Surg 1976; 72:849-53. [PMID: 994535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Fifty coronary reoperations were performed in 49 patients. The reasons for the operations were occluded or stenotic grafts in 23 patients, an inadequate first operation in 13, progression of coronary atherosclerosis in 3, and combinations of these reasons in 11. Mediastinal adhesions made the operations difficult and produced hazards. Six patients died from the operation. Seven surgical mishaps occurred, including damage to five functioning grafts from the previous operation and laceration of two ventricles. Nine patients had less than complete operations because angiographically demonstrated targets could not be found. Repeat angiography was performed on 9 of the surviving patients. Ten of the 14 new or revised grafts were found to be functioning. Although a repeat operation is more difficult technically and carries additional risks as compared with a first operation, the indications are thought to be the same for both first and secondary revascularization procedures. The increased risks of the repeat operations are compelling arguments to strive for complete revascularization at an initial operation in order to avoid the necessity of the second one.
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Stiles QR, Lindesmith GG, Tucker BL, Hughes RK, Meyer BW. Long-term follow-up of patients with coronary artery bypass grafts. Circulation 1976; 54:III32-4. [PMID: 1086744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A follow-up study of 1532 patients who had coronary artery bypass grafts from 1969 through 1974 revealed that the 5-year survival rate was substantially better than that recorded in previously published series of patients with similar disease demonstrated angiographically who did not undergo operation. Within this group of operated patients, those who had complete myocardial revascularization (i.e., three grafts for those with three-vessel disease) experienced a significantly better long-term prognosis than those who had fewer grafts than the number of vessels obstructed. The mortality curve in the completely revascularized patients was very similar to that of the general population of the United States, corrected to correspond to this patient sample in age and sex.
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Saksena DS, Parrish CM, Hughes RK, Fullmer CD. Sputum cytology in occult lung cancer. Rocky Mt Med J 1973; 70:33-6. [PMID: 4710726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Byrne JP, Hughes RK. Left heart bypass with a membrane oxygenator. J Thorac Cardiovasc Surg 1973; 65:795-801. [PMID: 4696879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Ghavamian M, Gutch CF, Hughes RK, Kopp KF, Kolff WJ. Pericardial tamponade in chronic-hemodialysis patients treatment by pericardectomy. Arch Intern Med 1973; 131:249-53. [PMID: 4682984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Wertheimer M, Hughes RK. Monitoring of coronary artery pressure during coronary artery perfusion. J Thorac Cardiovasc Surg 1972; 63:705-13. [PMID: 5028303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Depp DA, Hughes RK. Venovenous perfusion with a membrane oxygenator. J Thorac Cardiovasc Surg 1971; 62:658-62. [PMID: 5093822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Wertheimer M, Hughes RK. Scalene lymph node biopsy, Prevention of postoperative chylous fistula. Am J Surg 1971; 122:121-2. [PMID: 5091843 DOI: 10.1016/0002-9610(71)90364-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Hughes RK, Reemtsma K. Correction of coarctation of the aorta. Manometric determination of safety during test occlusion. J Thorac Cardiovasc Surg 1971; 62:31-3. [PMID: 5091683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Hughes RK, Carey JS, Reemtsma K. Operative internal rupture and Belsey hiatal hernia repair for reflux esophageal stricture. Ann Thorac Surg 1970; 9:203-8. [PMID: 5413745 DOI: 10.1016/s0003-4975(10)65491-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Hughes RK. Pericardial drainage at cardiac operations. Am J Surg 1968; 116:437-8. [PMID: 5675918 DOI: 10.1016/0002-9610(68)90237-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Plested WG, Tildon TT, Hughes RK. A philosophy of treatment of esophageal carcinoma. Am Surg 1968; 34:650-6. [PMID: 4175309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Carey JS, Hughes RK. Hemodynamic studies in open pneumothorax. J Thorac Cardiovasc Surg 1968; 55:538-45. [PMID: 4966968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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