Publications by authors named "Hugh Lemonde"

5 Publications

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Performance of laboratory tests used to measure blood phenylalanine for the monitoring of patients with phenylketonuria.

J Inherit Metab Dis 2020 03 2;43(2):179-188. Epub 2019 Oct 2.

Biochemical Sciences, Viapath, Guys & St Thomas' NHSFT, London, UK.

Analysis of blood phenylalanine is central to the monitoring of patients with phenylketonuria (PKU) and age-related phenylalanine target treatment-ranges (0-12 years; 120-360 μmol/L, and >12 years; 120-600 μmol/L) are recommended in order to prevent adverse neurological outcomes. These target treatment-ranges are based upon plasma phenylalanine concentrations. However, patients are routinely monitored using dried bloodspot (DBS) specimens due to the convenience of collection. Significant differences exist between phenylalanine concentrations in plasma and DBS, with phenylalanine concentrations in DBS specimens analyzed by flow-injection analysis tandem mass spectrometry reported to be 18% to 28% lower than paired plasma concentrations analyzed using ion-exchange chromatography. DBS specimens with phenylalanine concentrations of 360 and 600 μmol/L, at the critical upper-target treatment-range thresholds would be plasma equivalents of 461 and 768 μmol/L, respectively, when a reported difference of 28% is taken into account. Furthermore, analytical test imprecision and bias in conjunction with pre-analytical factors such as volume and quality of blood applied to filter paper collection devices to produce DBS specimens affect the final test results. Reporting of inaccurate patient results when comparing DBS results to target treatment-ranges based on plasma concentrations, together with inter-laboratory imprecision could have a significant impact on patient management resulting in inappropriate dietary change and potentially adverse patient outcomes. This review is intended to provide perspective on the issues related to the measurement of phenylalanine in blood specimens and to provide direction for the future needs of PKU patients to ensure reliable monitoring of metabolic control using the target treatment-ranges.
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http://dx.doi.org/10.1002/jimd.12163DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7957320PMC
March 2020

Bi-allelic Mutations in NDUFA6 Establish Its Role in Early-Onset Isolated Mitochondrial Complex I Deficiency.

Am J Hum Genet 2018 10 20;103(4):592-601. Epub 2018 Sep 20.

Department of Pediatrics and Adolescent Medicine, Division of Pediatric Neurology, University Medical Center Göttingen, 37075 Göttingen, Germany.

Isolated complex I deficiency is a common biochemical phenotype observed in pediatric mitochondrial disease and often arises as a consequence of pathogenic variants affecting one of the ∼65 genes encoding the complex I structural subunits or assembly factors. Such genetic heterogeneity means that application of next-generation sequencing technologies to undiagnosed cohorts has been a catalyst for genetic diagnosis and gene-disease associations. We describe the clinical and molecular genetic investigations of four unrelated children who presented with neuroradiological findings and/or elevated lactate levels, highly suggestive of an underlying mitochondrial diagnosis. Next-generation sequencing identified bi-allelic variants in NDUFA6, encoding a 15 kDa LYR-motif-containing complex I subunit that forms part of the Q-module. Functional investigations using subjects' fibroblast cell lines demonstrated complex I assembly defects, which were characterized in detail by mass-spectrometry-based complexome profiling. This confirmed a marked reduction in incorporated NDUFA6 and a concomitant reduction in other Q-module subunits, including NDUFAB1, NDUFA7, and NDUFA12. Lentiviral transduction of subjects' fibroblasts showed normalization of complex I. These data also support supercomplex formation, whereby the ∼830 kDa complex I intermediate (consisting of the P- and Q-modules) is in complex with assembled complex III and IV holoenzymes despite lacking the N-module. Interestingly, RNA-sequencing data provided evidence that the consensus RefSeq accession number does not correspond to the predominant transcript in clinically relevant tissues, prompting revision of the NDUFA6 RefSeq transcript and highlighting not only the importance of thorough variant interpretation but also the assessment of appropriate transcripts for analysis.
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http://dx.doi.org/10.1016/j.ajhg.2018.08.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174280PMC
October 2018

A new method for the rapid diagnosis of protein N-linked congenital disorders of glycosylation.

J Proteome Res 2013 Jul 17;12(7):3471-9. Epub 2013 Jun 17.

Biochemistry Research Group, Clinical and Molecular Genetics Unit, Institute of Child Health & Great Ormond Street Hospital, University College London, United Kingdom.

The Congenital Disorders of Glycosylation (CDG) are a devastating group of genetic disorders that encompass a spectrum of glycosylation defects and are characterized by the underglycosylation of or the presence of abnormal glycans on glycoproteins. The N-linked CDG disorders (Type I and II) are usually diagnosed in chemical pathology laboratories by an abnormal serum transferrin isoelectric focusing (IEF) pattern. Transferrin has been the protein of choice for CDG analysis because it is well characterized, highly abundant, and easily detected in plasma. However, IEF provides limited information on the glycosylation defect and requires a separate and extensive glycan analysis to diagnose CDG Type II. We have therefore developed a simple bead-based immunoaffinity and mass spectrometry-based assay to address these issues. Our method uses immuno-purified transferrin and proteolytic digestion followed by a rapid 30 min mass spectral analysis and allows us to identify both micro- and macroheterogeneity of transferrin by sequencing of peptides and glycopeptides. In summary, we have developed a simple, rapid test for N-linked glycosylation disorders that is a significant improvement on existing laboratory tests currently used for investigating defective N-linked glycosylation.
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http://dx.doi.org/10.1021/pr400328gDOI Listing
July 2013

Junior physician's use of Web 2.0 for information seeking and medical education: a qualitative study.

Int J Med Inform 2009 Oct 5;78(10):645-55. Epub 2009 Jun 5.

Department of Information Systems, ESADE Business School, Av. Pederables 60-62, 08034 Barcelona, Spain.

Background: Web 2.0 internet tools and methods have attracted considerable attention as a means to improve health care delivery. Despite evidence demonstrating their use by medical professionals, there is no detailed research describing how Web 2.0 influences physicians' daily clinical practice. Hence this study examines Web 2.0 use by 35 junior physicians in clinical settings to further understand their impact on medical practice.

Method: Diaries and interviews encompassing 177 days of internet use or 444 search incidents, analyzed via thematic analysis.

Results: Results indicate that 53% of internet visits employed user-generated or Web 2.0 content, with Google and Wikipedia used by 80% and 70% of physicians, respectively. Despite awareness of information credibility risks with Web 2.0 content, it has a role in information seeking for both clinical decisions and medical education. This is enabled by the ability to cross check information and the diverse needs for background and non-verified information.

Conclusion: Web 2.0 use represents a profound departure from previous learning and decision processes which were normally controlled by senior medical staff or medical schools. There is widespread concern with the risk of poor quality information with Web 2.0 use, and the manner in which physicians are using it suggest effective use derives from the mitigating actions by the individual physician. Three alternative policy options are identified to manage this risk and improve efficiency in Web 2.0's use.
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http://dx.doi.org/10.1016/j.ijmedinf.2009.04.008DOI Listing
October 2009

Optimisation of bile production during normothermic preservation of porcine livers.

Am J Transplant 2002 Aug;2(7):593-9

Nuffield Department of Surgery Oxford University, UK.

Machine perfusion of livers may provide a mechanism for extended preservation of marginal donor organs before transplantation, as well as a method for viability assessment. It has proved possible in a series of experimental porcine liver perfusions to maintain liver viability for up to 72 h. However, a reduction in bile production with associated histological evidence of cholestasis was seen after 10 h of perfusion, damaging the biliary canaliculi during the preservation period and leaving these organs in an unacceptable condition for transplantation. It was proposed that reduction in bile production was the result of a relentless depletion of available bile salts, gut recirculation not being possible and de-novo synthesis being unable to keep up with loss. This was proved by measuring porcine native bile acids within serial perfusate and bile samples using gas chromatography mass spectrophotometry. It was shown that all three native pig bile acids were decreased to 30% of their original value by 20 h of unsupplemented perfusion. An infusion of taurocholate managed to maintain bile production at physiological levels throughout the 20-h period (8 mL/h +/- 0.75). It was successfully incorporated by the porcine livers into bile. We propose to use this circuit as a novel means of preserving donor livers for transplantation in which the organ is maintained at normal body temperature and perfused with blood. This will reduce ischaemia reperfusion injury and may enable prolonged preservation. The modification described ensures optimal bile production over the entire perfusion period, preventing inspissation and subsequent damage to the canaliculus.
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http://dx.doi.org/10.1034/j.1600-6143.2002.20703.xDOI Listing
August 2002