101
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McClorey G, Fall AM, Moulton HM, Iversen PL, Rasko JE, Ryan M, Fletcher S, Wilton SD. Induced dystrophin exon skipping in human muscle explants. Neuromuscul Disord 2006; 16:583-90. [PMID: 16919955 DOI: 10.1016/j.nmd.2006.05.017] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Revised: 05/15/2006] [Accepted: 05/26/2006] [Indexed: 10/24/2022]
Abstract
Antisense oligonucleotide (AO) manipulation of pre-mRNA splicing of the dystrophin gene is showing promise in overcoming Duchenne muscular dystrophy (DMD)-causing mutations. To date, this approach has been limited to studies using animal models or cultured human muscle cells, and evidence that AOs can induce exon skipping in human muscle has yet to be shown. In this study, we used different AO analogues to induce exon skipping in muscle explants derived from normal and DMD human tissue. We propose that inducing exon skipping in human muscle explants is closer to in vivo conditions than cells in monolayer cultures, and may minimize the numbers of participants in Phase I clinical studies to demonstrate proof of principle of exon skipping in human muscle.
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MESH Headings
- Animals
- Cells, Cultured
- DNA Mutational Analysis
- Dystrophin/biosynthesis
- Dystrophin/genetics
- Exons/genetics
- Genetic Predisposition to Disease/genetics
- Genetic Testing
- Genetic Therapy/methods
- Genetic Therapy/trends
- Humans
- Mice
- Mice, Inbred mdx
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/metabolism
- Muscular Dystrophy, Duchenne/physiopathology
- Mutation/genetics
- Oligonucleotides, Antisense/genetics
- Oligonucleotides, Antisense/pharmacology
- Oligonucleotides, Antisense/therapeutic use
- RNA Precursors/genetics
- RNA Splicing/genetics
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102
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Stanley AG, Fletcher S, Tan A, Barnett DB. Is warfarin a contraindication to thrombolysis in acute ST elevation myocardial infarction? Heart 2006; 92:1145-146. [PMID: 16844867 PMCID: PMC1861091 DOI: 10.1136/hrt.2005.062158] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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103
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McClorey G, Moulton HM, Iversen PL, Fletcher S, Wilton SD. Antisense oligonucleotide-induced exon skipping restores dystrophin expression in vitro in a canine model of DMD. Gene Ther 2006; 13:1373-81. [PMID: 16724091 DOI: 10.1038/sj.gt.3302800] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Manipulation of pre-mRNA splicing by antisense oligonucleotides (AOs) offers considerable potential for a number of genetic disorders. One of these is Duchenne muscular dystrophy (DMD), where mutations in the dystrophin gene typically result in premature termination of translation that causes a loss of functional protein. AOs can induce exon skipping such that the mutation is by-passed and the reading frame restored, producing an internally deleted protein similar to that found in the milder Becker muscular dystrophy. To date, this approach has been applied to the mdx mouse model in vitro and in vivo and in human myoblast cultures. Here, we report the application of AO-directed exon skipping to induce dystrophin expression in vitro in a canine model of DMD, golden retriever muscular dystrophy (GRMD). The efficacy of 2'-O-methyl phosphorothioate (2OMe), phosphorodiamidate morpholino oligomers (PMOs) and peptide-linked PMOs (PMO-Pep) to induce dystrophin expression was assessed. The 2OMe chemistry was only effective for short-term induction of corrected transcript and could not induce detectable dystrophin protein. The PMO chemistry generally induced limited exon skipping at only high concentrations; however, a low level of dystrophin protein was produced in treated cells. Use of the PMO-Pep, applied here for the first time to a DMD model, was able to induce high and sustained levels of exon skipping and induced the highest level of dystrophin expression with no apparent adverse effects upon the cells. The induction of dystrophin in the GRMD model offers the potential for further testing of AO delivery regimens in a larger animal model of DMD, in preparation for application in human clinical trials.
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104
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Kerr B, Bauman L, Ng J, Fletcher S, Aust R, MacLeod C, Hamed K, Averelt D, Worland S. O.106 Pharmakokinetics, safety, tolerability, and pharmacodynamics of the isatoribine oral prodrug ANA975 in a multidose phase 1 healthy volunteer study. J Clin Virol 2006. [DOI: 10.1016/s1386-6532(06)80102-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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105
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Wilton SD, Fletcher S. Antisense oligonucleotides, exon skipping and the dystrophin gene transcript. ACTA MYOLOGICA : MYOPATHIES AND CARDIOMYOPATHIES : OFFICIAL JOURNAL OF THE MEDITERRANEAN SOCIETY OF MYOLOGY 2005; 24:222-9. [PMID: 16629057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Antisense oligonucleotide induced exon skipping has recently emerged as a potential therapy to by-pass the consequences of many, but not all dystrophin mutations that lead to Duchenne muscular dystrophy. Targeted removal of one or more exons, to restore a disrupted reading frame, or omit a nonsense mutation, could lessen the consequences of an estimated 80% of dystrophin gene mutations. Promising in vitro and in vivo experiments in animal models of dystrophinopathies, as well as demonstration of induced exon skipping in cultured human myogenic cells have prompted considerable enthusiasm. Furthermore, advances in antisense oligonucleotide chemistries have resulted in the development of more stable and less toxic compounds, some of which are currently in Phase III clinical trials for selected antiviral applications. This review will summarize developments in induced exon skipping that have paved the way to clinical trials and some of the challenges and possible limitations.
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106
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Herbert KE, Fletcher S, Chauhan D, Ladapo A, Nirwan J, Munson S, Mistry P. Dietary supplementation with different vitamin C doses: no effect on oxidative DNA damage in healthy people. Eur J Nutr 2005; 45:97-104. [PMID: 16021530 DOI: 10.1007/s00394-005-0569-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Accepted: 05/24/2005] [Indexed: 11/24/2022]
Abstract
BACKGROUND Antioxidants are believed to prevent many types of disease. Some previous studies suggest that dietary supplementation with vitamin C results in a decrease in the level of one of the markers of oxidative damage-8-oxoguanine in the DNA of peripheral blood mononuclear cells (PBMC). AIM OF TRIAL: To investigate the effect of different dose levels of dietary supplementation with vitamin C on oxidative DNA damage. METHODS A randomised double-blind placebo-controlled trial was carried out using three different levels (80, 200 and 400 mg) of dietary vitamin C supplementation in a healthy population of 160 volunteers; supplementation was for a period of 15 weeks followed by a 10 week washout period. Peripheral blood samples were obtained every 5 weeks from baseline to 25 weeks. RESULTS An increase in PBMC vitamin C levels was not observed following supplementation in healthy volunteers. There was no effect found on 8-oxoguanine measured using HPLC with electrochemical detection for any of the three supplemented groups compared to placebo. 8-oxoadenine levels were below the limit of detection of the HPLC system used here. CONCLUSIONS Supplementation with vitamin C had little effect on cellular levels in this group of healthy individuals, suggesting their diets were replete in vitamin C. The dose range of vitamin C used did not affect oxidative damage in PBMC DNA.
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107
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Iliffe S, Curran HV, Collins R, Yuen Kee SC, Fletcher S, Woods B. Attitudes to long-term use of benzodiazepine hypnotics by older people in general practice: findings from interviews with service users and providers. Aging Ment Health 2004; 8:242-8. [PMID: 15203405 DOI: 10.1080/13607860410001669778] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The aim of this study was to explore beliefs and attitudes about continuing or stopping benzodiazepine hypnotics amongst older patients using such medicines, and amongst their general practitioners. One hundred and ninety two patients aged 65 and over who were long-term users of benzodiazepine hypnotics were recruited from 25 general practices in inner city and suburban London, as were 83 practice staff. The practices had been recruited into a randomised controlled trial of benzodiazepine withdrawal in long-term users. Semi-structured interviews were conducted with patients recruited to the trial, and non-standardized (conversational) interviews with practice staff. Sixty percent of long-term benzodiazepine users had taken their hypnotic for more than 10 years, and one-third for more than 20 years. Beliefs in the efficacy of hypnotics, and self-report of insomnia despite their use, varied according to the willingness to attempt withdrawal. The majority of patients reported no warnings from professionals about adverse effects of using benzodiazepine hypnotics. Half had tried to stop at some time but most attempts had been short-lived. Patients and doctors had distinctly different views of the advantages, disadvantages and risks of stopping benzodiazepine hypnotic use. Both increased patient awareness of the problems of long-term benzodiazepine use and an evidence-based approach to withdrawal efforts in primary care are necessary to reduce the consumption of medication that has little real benefit.
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108
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Wells KE, Fletcher S, Mann CJ, Wilton SD, Wells DJ. Enhanced in vivo delivery of antisense oligonucleotides to restore dystrophin expression in adult mdx mouse muscle. FEBS Lett 2003; 552:145-9. [PMID: 14527677 DOI: 10.1016/s0014-5793(03)00904-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The use of antisense oligonucleotides (AOs) to induce exon skipping leading to generation of an in-frame dystrophin protein product could be of benefit in around 70% of Duchenne muscular dystrophy patients. We describe the use of hyaluronidase enhanced electrotransfer to deliver uncomplexed 2'-O-methyl modified phosphorothioate AO to adult dystrophic mouse muscle, resulting in dystrophin expression in 20-30% of fibres in tibialis anterior muscle after a single injection. Although expression was transient, many of the corrected fibres initially showed levels of dystrophin expression well above the 20% of endogenous previously shown to be necessary for phenotypic correction of the dystrophic phenotype.
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MESH Headings
- Animals
- Base Sequence
- Dystrophin/chemistry
- Dystrophin/genetics
- Dystrophin/metabolism
- Electroporation/methods
- Genetic Therapy
- Humans
- Hyaluronoglucosaminidase
- Male
- Mice
- Mice, Inbred mdx
- Muscle, Skeletal/metabolism
- Muscular Dystrophy, Animal/genetics
- Muscular Dystrophy, Animal/metabolism
- Muscular Dystrophy, Animal/therapy
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/metabolism
- Muscular Dystrophy, Duchenne/therapy
- Oligodeoxyribonucleotides, Antisense/administration & dosage
- Oligodeoxyribonucleotides, Antisense/chemistry
- Oligodeoxyribonucleotides, Antisense/genetics
- Transduction, Genetic
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109
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Fletcher S. Reply. Nephrol Dial Transplant 2003. [DOI: 10.1093/ndt/gfg359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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110
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Curran HV, Collins R, Fletcher S, Kee SCY, Woods B, Iliffe S. Older adults and withdrawal from benzodiazepine hypnotics in general practice: effects on cognitive function, sleep, mood and quality of life. Psychol Med 2003; 33:1223-1237. [PMID: 14580077 DOI: 10.1017/s0033291703008213] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Older adults are the main recipients of repeat prescriptions for benzodiazepine (BZD) hypnotics. BZDs can impair cognitive function and may not aid sleep when taken continuously for years. This study therefore aimed to determine if withdrawing from BZDs leads to changes in patients' cognitive function, quality of life, mood and sleep. METHOD One hundred and ninety-two long-term users of BZD hypnotics, aged > or = 65 years, were identified in 25 general practices. One hundred and four who wished to withdraw were randomly allocated to one of two groups under double-blind, placebo controlled conditions: group A's BZD dose was tapered from week 1 of the trial; group B were given their usual dose for 12 weeks and then it was tapered. An additional group (C) of 35 patients who did not wish to withdraw from BZDs participated as 'continuers'. All patients were assessed at 0, 12 and 24 weeks and 50% were reassessed at 52 weeks. RESULTS Sixty per cent of patients had taken BZDs continuously for > 10 years; 27% for > 20 years. Of all patients beginning the trial, 80% had successfully withdrawn 6 months later. There was little difference between groups A and B, but these groups differed from continuers (C) in that the performance of the withdrawers on several cognitive/psychomotor tasks showed relative improvements at 24 or 52 weeks. Withdrawers and continuers did not differ in sleep or BZD withdrawal symptoms. CONCLUSIONS These results have clear implications for clinical practice. Withdrawal from BZDs produces some subtle cognitive advantages for older people, yet little in the way of withdrawal symptoms or emergent sleep difficulties. These findings also suggest that, taken long-term, BZDs do not aid sleep.
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111
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Fletcher S, Bowden SEH, Marrion NV. False interaction of syntaxin 1A with a Ca(2+)-activated K(+) channel revealed by co-immunoprecipitation and pull-down assays: implications for identification of protein-protein interactions. Neuropharmacology 2003; 44:817-27. [PMID: 12681380 DOI: 10.1016/s0028-3908(03)00049-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The techniques of co-immunoprecipitation and immunocytochemical co-labelling are classically used to identify protein-protein interactions. We have used an antibody to the rat small conductance calcium-activated potassium channel subtype 1 (rSK1) to immunoprecipitate proteins from rat brain. A 35 kDa protein was recognized by two monoclonal antibodies to syntaxin 1 and a polyclonal antibody to syntaxin 1A, but not by antibodies to syntaxins 2, 3 or 4. These data suggested that syntaxin 1A is specifically associated with rSK1 in rat brain. A GST construct of the carboxyl terminus of rSK1 was able to pull-down syntaxin 1A from rat brain. Immunocytochemistry showed somatic labelling for both rSK1 and syntaxin 1A in acutely dissociated hippocampal CA1 neurons, confirming that these proteins could interact in vivo. However, control immunoprecipitations showed that antibodies to eight potassium channels could also immunoprecipitate syntaxin, even though some of these channels would not be expected to reside in the same subcellular compartment. Mock immunoprecipitations and pull-down assays showed that syntaxin 1 could directly interact with sepharose and agarose resins. Hence immunoprecipitation and pull-down assays do not provide evidence that syntaxin is specifically associating with a protein, placing doubt on a number of reported interactions with syntaxin 1A.
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112
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Loveridge N, Fletcher S, Power J, Caballero-Alías AM, Das-Gupta V, Rushton N, Parker M, Reeve J, Pitsillides AA. Patterns of osteocytic endothelial nitric oxide synthase expression in the femoral neck cortex: differences between cases of intracapsular hip fracture and controls. Bone 2002; 30:866-71. [PMID: 12052455 DOI: 10.1016/s8756-3282(02)00732-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Evidence indicates that extensive amalgamation of adjacent resorbing osteons is responsible for destroying the microstructural integrity of the femoral neck's inferior cortex in osteoporotic hip fracture. Such osteonal amalgamation is likely to involve a failure to limit excessive resorption, but its mechanistic basis remains enigmatic. Nitric oxide (NO) inhibits osteoclastic bone destruction, and in normal bone cells its generation by endothelial nitric oxide synthase (eNOS, the predominant bone isoform) is enhanced by mechanical stimuli and estrogen, which both protect against fracture. To determine whether eNOS expression in osteocytes reflects their proposed role in regulating remodeling, we have examined patterns of osteocyte eNOS immunolabeling in the femoral neck cortex of seven cases of hip fracture and seven controls (females aged 68-96 years). The density of eNOS+ cells (mm(-2)) was 53% lower in the inferior cortex of the fracture cases (p < 0.0004), but was similar in the superior cortex. eNOS+ osteocytes were, on average, 22% further from their nearest blood supply, than osteocytes in general (p < 0.0001) and the nearest eNOS+ osteocyte was 57% further from its nearest canal surface (p < 0.0001). This differential distribution of eNOS+ osteocytes was significantly more pronounced in the cortices of fracture cases (p < 0.0001). We conclude that the normal regional and osteonal pattern of eNOS expression by osteocytes is disrupted in hip fracture, particularly at sites that are loaded most by physical activity. These results suggest that eNOS+ osteocytes may normally act as sentinels confining resorption within single osteons. A reduction in their number, coupled to an increase in their remoteness from canal surfaces, may thus permit the irreversible merging of resorbing osteons, and thus contribute to the marked increase in the fragility of osteoporotic bone.
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113
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Hewitt DA, Fletcher S, England GC. Test of canine sperm function in vitro using primary homologous oocytes with fluorescence and confocal microscopy. JOURNAL OF REPRODUCTION AND FERTILITY. SUPPLEMENT 2002; 57:127-36. [PMID: 11787139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
In vitro capacitated canine spermatozoa can interact with both mature and immature homologous oocytes in vitro, but it is difficult to determine whether spermatozoa have actually penetrated the oocyte or have simply bound to the zona pellucida. The aim of the first part of this study was to determine accurately the location of spermatozoa in relation to the oocyte by comparing observations made using confocal and fluorescence microscopy. The fluorescence technique had a sensitivity of 66%, and correctly identified 98% of the spermatozoa that had penetrated or bound oocytes and could discriminate between penetrated and bound spermatozoa with a sensitivity and specificity of 97% and 100%, respectively. This finding demonstrates that evaluation of the assay by fluorescence microscopy is reliable for detecting the presence and location of spermatozoa in relation to homologous oocytes. The aim of the second part of the study was to attempt to simplify the assay using fluorescence microscopy and immature oocytes. No significant difference was found between sperm interaction with mature and immature oocytes, which demonstrates that culturing oocytes before the assay has no benefit, and that the assay can be performed quickly and easily using non-cultured oocytes to provide rapid evidence of the fertilizing potential of spermatozoa.
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114
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Fletcher S, Carville KS, Howell JM, Mann CJ, Wilton SD. Evaluation of a short interspersed nucleotide element in the 3' untranslated region of the defective dystrophin gene of dogs with muscular dystrophy. Am J Vet Res 2001; 62:1964-8. [PMID: 11763189 DOI: 10.2460/ajvr.2001.62.1964] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To determine the distribution of a 231-base pair (bp) element in the dystrophin gene 3' untranslated region (UTR) in a colony of Golden Retrievers with muscular dystrophy and other unrelated dogs and to estimate the frequency of recombination for the canine dystrophin gene. ANIMALS 77 dogs from the Golden Retriever Muscular Dystrophy (GRMD) colony at the Murdoch Veterinary School and 30 unrelated dogs from the Murdoch University Veterinary Clinic. PROCEDURE Samples of blood or hair from dogs were used for amplification of DNA, using primers to the canine dystrophin 3' UTR. RESULTS The DNA from affected dogs generated a larger PCR product than that obtained from clinically normal dogs. Products were cloned and sequenced, and the difference in size was found to be attributable to a 231-bp short interspersed nucleotide element (SINE). The SINE was found in all affected dogs in the colony but not in most unaffected puppies in the colony. Eighteen of 19 dogs in the colony were heterozygous for the GRMD mutation, and 7 of 30 unrelated dogs also were heterozygous for the SINE. CONCLUSION AND CLINICAL RELEVANCE Evidence of recombination between the GRMD mutation and the SINE was observed in only 4 dogs (2 sets of littermates) in the GRMD colony. Incidence of this SINE in a few unrelated dogs suggests that this particular insertion into the dystrophin gene may have been a recent event. The SINE in the dystrophin 3' UTR did not have an apparent influence on dystrophin mRNA concentrations.
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115
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Kudera M, Nakagawa Y, Fletcher S, Hill HA. A voltammetric study of direct electron transfer to cytochrome c using a very large assembly of carbon microelectrodes. LAB ON A CHIP 2001; 1:127-131. [PMID: 15100872 DOI: 10.1039/b107541c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A very large assembly of more than 8000 carbon fibre microdisk electrodes was used to study direct electron transfer to cytochrome c. Near steady-state cyclic voltammograms were observed, which exhibited excellent signal-to-noise ratios despite the low concentrations of cytochrome c employed (1-50 microM). The high resolution of the voltammograms allowed the formal potential of the native form of cytochrome c to be determined over a range of solution pH.
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116
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van Dijk N, Fletcher S, Madden CE, Marken F. Nanocomposite electrodes made of carbon nanofibers and black wax. Anodic stripping voltammetry of zinc and lead. Analyst 2001; 126:1878-81. [PMID: 11763059 DOI: 10.1039/b104816n] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nanocomposite electrodes offer exciting new possibilities in electroanalytical chemistry. In this preliminary study, nanocomposite electrodes made of carbon nanofibers and black wax were characterized and investigated as novel substrates for metal deposition and stripping processes. Carbon nanofibers were grown from ethylene-hydrogen gas mixtures over Fe-Ni-Cu (85:10:5) nanoparticle catalysts at 600 degrees C and then embedded in Apiezon black wax under vacuum at 140 degrees C. The resulting nanocomposite electrodes showed (i) good conductivity, (ii) a wide potential window in aqueous solutions, (iii) low background currents, (iv) near steady state voltammetric responses with substantial Faradaic currents and (v) sharply peaked fast scan metal stripping responses. Zinc is a notoriously difficult metal to determine in aqueous solutions, because its deposition and stripping are accompanied by hydrogen evolution at extreme negative potentials. It therefore provided a challenging test for our new nanocomposite electrode. Although numerous complications associated with the hydrogen evolution process could not be eliminated, remarkably clear voltammograms could be obtained even at scan rates of 40 V s(-1).
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117
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Bowden SE, Fletcher S, Loane DJ, Marrion NV. Somatic colocalization of rat SK1 and D class (Ca(v)1.2) L-type calcium channels in rat CA1 hippocampal pyramidal neurons. J Neurosci 2001; 21:RC175. [PMID: 11588205 PMCID: PMC6763866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
In hippocampal neurons, the firing of a train of action potentials is terminated by generation of the slow afterhyperpolarization (AHP). Recordings from hippocampal slices have shown that the slow AHP likely results from the activation of small-conductance calcium-activated potassium (SK) channels by calcium (Ca(2+)) entry through L-type Ca(2+) channels. However, the relative localization of these two channel subtypes is not known. The cloning and characterization of three subtypes of SK channel has suggested that SK1 may underlie generation of the slow AHP. Using a novel antibody directed against rat SK1 (rSK1), it has been determined that the rSK1 channel is primarily in the soma of hippocampal CA1 neurons. In conjunction with antibodies directed against C (Ca(v)1.2) and D (Ca(v)1.3) class L-type Ca(2+) channel alpha1 subunits, it was observed that rSK1 channels were selectively colocalized with D class L-type channels. This colocalization supports the functional coupling of L-type and SK channels previously observed in cell-attached patches from hippocampal neurons. However, it appears contrary to the slow rise and decay of the slow AHP. Induction of delayed facilitation of L-type Ca(2+) channels in cell-attached patches from hippocampal neurons evoked delayed opening of coupled SK channels. Generation of ensemble currents produced waveforms identical to the ionic current underlying the slow AHP (I(sAHP)). Therefore, these data indicate that the slow AHP is somatic in origin, resulting from delayed facilitation of D class L-type Ca(2+) channels colocalized with rSK1 channels.
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118
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Millward RC, Madden CE, Sutherland I, Mortimer RJ, Fletcher S, Marken F. Directed assembly of multilayers--the case of Prussian blue. Chem Commun (Camb) 2001:1994-5. [PMID: 12240256 DOI: 10.1039/b106616c] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We introduce the concept of 'directed assembly' of multilayers on surfaces: the overall process involves the exposure of a surface to a series of solutions containing, alternately, adsorbable cations and adsorbable anions, and these are gradually built up into well-defined multilayer structures.
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119
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Russo LM, Fletcher S, Danford DA, Duncan K, Najdawi E. Persistent third aortic arch (carotid duct) associated with critical coarctation of the aorta. Echocardiography 2001; 18:621-2. [PMID: 11737976 DOI: 10.1046/j.1540-8175.2001.00621.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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120
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Gilbert R, Nalbantoglu J, Howell JM, Davies L, Fletcher S, Amalfitano A, Petrof BJ, Kamen A, Massie B, Karpati G. Dystrophin expression in muscle following gene transfer with a fully deleted ("gutted") adenovirus is markedly improved by trans-acting adenoviral gene products. Hum Gene Ther 2001; 12:1741-55. [PMID: 11560768 DOI: 10.1089/104303401750476249] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Helper-dependent adenoviruses (HDAd) are Ad vectors lacking all or most viral genes. They hold great promise for gene therapy of diseases such as Duchenne muscular dystrophy (DMD), because they are less immunogenic than E1/E3-deleted Ad (first-generation Ad or FGAd) and can carry the full-length (Fl) dystrophin (dys) cDNA (12 kb). We have compared the transgene expression of a HDAd (HDAdCMVDysFl) and a FGAd (FGAdCMV-dys) in cell culture (HeLa, C2C12 myotubes) and in the muscle of mdx mice (the mouse model for DMD). Both vectors encoded dystrophin regulated by the same cytomegalovirus (CMV) promoter. We demonstrate that the amount of dystrophin expressed was significantly higher after gene transfer with FGAdCMV-dys compared to HDAdCMVDysFl both in vitro and in vivo. However, gene transfer with HDAdCMVDysFl in the presence of a FGAd resulted in a significant increase of dystrophin expression indicating that gene products synthesized by the FGAd increase, in trans, the amount of dystrophin produced. This enhancement occurred in cell culture and after gene transfer in the muscle of mdx mice and dystrophic golden retriever (GRMD) dogs, another animal model for DMD. The E4 region of Ad is required for the enhancement, because no increase of dystrophin expression from HDAdCMVDysFl was observed in the presence of an E1/E4-deleted Ad in vitro and in vivo. The characterization of these enhancing gene products followed by their inclusion into an HDAd may be required to produce sufficient dystrophin to mitigate the pathology of DMD by HDAd-mediated gene transfer.
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121
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Fletcher S, Ly T, Duff RM, McC Howell J, Wilton SD. Cryptic splicing involving the splice site mutation in the canine model of Duchenne muscular dystrophy. Neuromuscul Disord 2001; 11:239-43. [PMID: 11297938 DOI: 10.1016/s0960-8966(00)00187-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Golden retriever muscular dystrophy arises from a mutation in the acceptor splice site of intron 6 of the dystrophin gene. Skipping of exon 7 disrupts the mRNA reading frame and results in premature termination of translation. We are using this animal model to evaluate treatments for Duchenne muscular dystrophy, including gene repair induced by chimeric oligonucleotides. After injection of golden retriever muscular dystrophy (GRMD) muscle with a chimeric oligonucleotide to repair the lesion, immunostaining revealed a modest increase in the number of dystrophin-positive fibres at the injection sites. Dystrophin gene transcripts containing exon 7 were detected by reverse transcription-polymerase chain reaction, suggesting that low levels of splice site correction may have occurred. However, DNA sequencing of these apparently normal dystrophin gene transcripts revealed that the first five bases of exon 7 were missing. It will be important to be aware of this phenomenon with respect to further gene correction studies in the canine model.
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MESH Headings
- Alternative Splicing/genetics
- Animals
- Chimera/genetics
- Disease Models, Animal
- Dogs
- Dystrophin/genetics
- Exons/genetics
- Female
- Frameshift Mutation/genetics
- Immunohistochemistry
- Male
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/metabolism
- Muscular Dystrophy, Duchenne/physiopathology
- Mutagenesis, Site-Directed/genetics
- Oligonucleotides/pharmacology
- RNA Splice Sites/genetics
- RNA, Messenger/genetics
- Reading Frames/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Transcription, Genetic/genetics
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O'Hara AJ, Howell JM, Taplin RH, Fletcher S, Lloyd F, Kakulas B, Lochmüller H, Karpati G. The spread of transgene expression at the site of gene construct injection. Muscle Nerve 2001; 24:488-95. [PMID: 11268020 DOI: 10.1002/mus.1031] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Seven 2-day-old golden retriever pups were given focal intramuscular injections of a first generation adenovirus-dystrophin minigene construct and adenovirus-beta-galactosidase construct as a 2:1 mixture into the left anterior tibial muscle. The spread of transgene expression within the anterior tibial muscle was compared with the spread of methylene blue dye after identical injection into the contralateral muscle. Transgene expression 5-7 days after intramuscular injection was shown to extend between 5.8 and 11.6 mm along the biopsied muscle length (range of biopsy lengths 11.1-12.2 mm). The level of transgene expression at 2-2.5-mm intervals from the site of injection was significantly related to the distance from the site of injection (dystrophin, P = 0.009; beta-galactosidase, P = 0.015). The spread of methylene blue dye within the anterior tibial muscle < or =24 h after identical intramuscular injection demonstrated a similar pattern to the transgene expression, with dye staining measured between 5.5 and 8.5 mm along the muscle sample length (range of biopsy lengths 5.6-15.6 mm). The greatest transgene expression and dye staining was measured 2-2.5 mm proximal to the site of injection with a maximum of 23% of muscle fibers expressing the dystrophin transgene, 95.2% expressing the beta-galactosidase transgene, and 98% of the tissue section stained with methylene blue dye. These results suggest transgene expression after focal intramuscular injection is relatively localized around the site of injection. Further research is required to develop techniques that will provide transgene expression throughout the length and breadth of a muscle.
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Mann CJ, Honeyman K, Cheng AJ, Ly T, Lloyd F, Fletcher S, Morgan JE, Partridge TA, Wilton SD. Antisense-induced exon skipping and synthesis of dystrophin in the mdx mouse. Proc Natl Acad Sci U S A 2001; 98:42-7. [PMID: 11120883 PMCID: PMC14541 DOI: 10.1073/pnas.98.1.42] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a severe muscle wasting disease arising from defects in the dystrophin gene, typically nonsense or frameshift mutations, that preclude the synthesis of a functional protein. A milder, allelic version of the disease, Becker muscular dystrophy, generally arises from in-frame deletions that allow synthesis of a shorter but still semifunctional protein. Therapies to introduce functional dystrophin into dystrophic tissue through either cell or gene replacement have not been successful to date. We report an alternative approach where 2'-O-methyl antisense oligoribonucleotides have been used to modify processing of the dystrophin pre-mRNA in the mdx mouse model of DMD. By targeting 2'-O-methyl antisense oligoribonucleotides to block motifs involved in normal dystrophin pre-mRNA splicing, we induced excision of exon 23, and the mdx nonsense mutation, without disrupting the reading frame. Exon 23 skipping was first optimized in vitro in transfected H-2K(b)-tsA58 mdx myoblasts and then induced in vivo. Immunohistochemical staining demonstrated the synthesis and correct subsarcolemmal localization of dystrophin and gamma-sarcoglycan in the mdx mouse after intramuscular delivery of antisense oligoribonucleotide:liposome complexes. This approach should reduce the severity of DMD by allowing a dystrophic gene transcript to be modified, such that it can be translated into a Becker-dystrophin-like protein.
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MESH Headings
- Animals
- Base Sequence
- Cells, Cultured
- Cytoskeletal Proteins/metabolism
- Disease Models, Animal
- Dystrophin/biosynthesis
- Dystrophin/genetics
- Exons/genetics
- Fluorescein
- Immunohistochemistry
- Injections, Intramuscular
- Introns/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Microscopy, Fluorescence
- Molecular Sequence Data
- Muscles/metabolism
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/therapy
- Oligoribonucleotides, Antisense/administration & dosage
- Oligoribonucleotides, Antisense/genetics
- Oligoribonucleotides, Antisense/therapeutic use
- Open Reading Frames/genetics
- Phosphatidylethanolamines/metabolism
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA Splicing/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Sarcoglycans
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124
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Sharma JC, Fletcher S, Vassallo M, Ross I. What influences outcome of stroke--pyrexia or dysphagia? Int J Clin Pract 2001; 55:17-20. [PMID: 11219313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/19/2023] Open
Abstract
To investigate the significance of pyrexia and dysphagia as risk factors for mortality at 90 days in patients admitted with an acute stroke when controlled with other confounding factors, 202 stroke patients admitted to acute medical wards were prospectively studied for demographic and neurological details, stroke syndromes and pathology. A number of other factors were recorded within three days of admission, including pyrexia and dysphagia. Cox's proportional hazards model was used to identify the effect of 10 factors on mortality at 90 days; 59 (29%) patients had died by 90 days. Univariate analysis revealed pyrexia and dysphagia to be independently and significantly associated with indices of stroke severity and 90 day mortality (p < 0.001 for both). Cox's proportional hazards model, however, revealed that stroke mortality was associated with dysphagia (relative risk 2.6, 95% CI 1.2-5.4; p = 0.009), pre-existing diabetes mellitus (2.4, CI 1.2-4.5; p = 0.006), higher age > 75 years (1.8, CI 1.0-3.1), ischaemic heart disease (2.1, CI 1.1-4.2, p = 0.025), total anterior circulation syndromes (2.8, CI 1.5-5.2) and previous stroke (1.8, CI 1.0-3.2, p = 0.028). Pyrexia was not a significant factor (p = 0.50). Although both pyrexia and dysphagia are associated with higher mortality in acute stroke patients, dysphagia was a significant variable predicting death at 90 days when controlled for other factors known to influence stroke mortality. Pyrexia is not significant when other variables are considered.
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Sharma JC, Fletcher S, Vassallo M, Ross I. Prognostic value of CT scan features in acute ischaemic stroke and relationship with clinical stroke syndromes. Int J Clin Pract 2000; 54:514-8. [PMID: 11198729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/19/2023] Open
Abstract
The aim of this prospective study was to investigate the value of CT scan in prognosis of acute ischaemic stroke patients as a variable additional to clinical stroke syndromes to develop a simple classification of CT scan features to provide a practical approach to prognosticate and manage such patients. One hundred and eight nine patients admitted with ischaemic stroke were investigated with a CT scan. CT scan features were classified into two groups: large infarct, LI (across more than one lobe) and non-large infarcts (N-LI) for all other features. Patients were also studied for clinical syndromes, analysing results for total anterior circulation syndrome (TACS). Outcome was measured as early post stroke Barthel index, acute phase and 3-month mortality. Patients with LI had features of severe strokes and had a lower Barthel index (p < 0.001), lower Glasgow coma score (p < 0.001), more association with incontinence (p < 0.001), pyrexia (p = 0.007) and dysphagia (p < 0.001). LI patients required higher level of care in acute wards and had a higher length of stay (p = 0.01). Both the LI and TACS individually had a significantly higher mortality (p < 0.001) and similar positive predictive value, sensitivity and specificity for 3-month mortality. While the combined factor of 'large infarct and TACS' provided the highest likelihood ratio (3.1) for mortality, the factor of 'large infarct or TACS' was the most sensitive (85%) to identify majority of patients at a risk of mortality. N-LI patients had a better prognosis. Classification of cerebral infarcts into large and non-large categories identifies patients who require higher level of care in acute wards and have a higher mortality. Combined factor of 'large infarct and/or TACS' identifies the majority of patients at risk of 3-month mortality as compared to either variable taken individually. CT scan features are complimentary to clinical syndromes for managing acute stroke patients.
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