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Biomedical subjects

S Walton

Publications and source records attributed to S Walton.

At least 19 recordsLinked to original sources
PubMed2006

Blood oxygen level-dependent (BOLD) magnetic resonance imaging in patients with dypiridamole induced ischaemia; a PET comparative study.

BACKGROUND: Blood oxygen level-dependent (BOLD) MRI relies on changes in deoxyhaemoglobin level in tissues under stress for signal variation and may be used for detection of ischaemic myocardium. METHODS: 15 patients with stress induced myocardial ischaemia on PET scanning underwent rest and dypiridamole stress MRI using a double breath-hold T2-weighted, ECG gated sequence to produce BOLD contrast images and cine-MRI for wall thickening assessment. Signal change on BOLD MRI and wall thickening were compared between rest and stress images in ischaemic and non-ischaemic myocardial segments. RESULTS: Using PET, 156 segments were identified with reversible ischaemia and 324 as non-ischaemic. The ischaemic segments were found on BOLD MRI to have an average signal change between rest and stress of -16.7% compared to -14% in the non-ischaemic segments (p=0.04). The average wall thickening was 7.8 mm in the ischaemic segments compared with 9.5 mm in the non-ischaemic segments (p<0.0001). CONCLUSION: BOLD MRI with wall thickening assessment may differentiate ischaemic from non-ischaemic myocardium in patients with stress induced myocardial ischaemia. Larger studies with improved spatial resolution would help define a threshold for detection of ischaemia as well as determine this technique's sensitivity and specificity.

Aged↗
PubMed2006

Blood oxygen level dependent (BOLD) MRI: A novel technique for the detection of myocardial ischemia.

BACKGROUND: Blood oxygen level dependent (BOLD) T2* MRI detects signal variance within the myocardium based on changes in the deoxyhaemoglobin level following pharmacological stress, and it has the potential to identify areas of myocardial ischemia. The aim of the present study was to assess the utility of BOLD T2* MRI in the detection of myocardial ischemia in patients with an existing diagnosis of coronary artery disease. METHOD: Twenty-one patients with established three-vessel coronary artery disease on coronary angiography underwent rest and dipyridamole stress MRI using a double breath-hold T2* weighted ECG gated sequence. Analysis was performed on multiple short-axis slices of the heart, projected as a bull's eye. The myocardium was divided into three coronary territories, yielding 63 territories in total. A signal change between rest and stress of more than +/-4% was significant, implying a change in deoxyhaemoglobin concentration. A signal decrease or no changes denote the presence of ischemia, while a signal increase indicates no ischemia. RESULTS: All images were of sufficient quality for signal intensity analysis. In 12/63 territories (19%), a significant signal increase following stress was detected. A significant signal decrease was detected in 34/63 territories (54%), and in 17/63 territories (27%) there was a non-significant change. The presence of a perfusion defect was identified, therefore, in 51/63 (81%), based on the signal difference between rest and stress. CONCLUSION: Changes in myocardial oxygen level appear to be detectable by BOLD T2* MRI without using contrast media. Further, larger comparative studies are required to evaluate the diagnostic and prognostic impact of this technique and to compare it to the gold standard methods for the detection of myocardial ischemia.

Journal Article↗
PubMed2006

Intraindividual, right-left comparison of topical methyl aminolaevulinate-photodynamic therapy and cryotherapy in subjects with actinic keratoses: a multicentre, randomized controlled study.

BACKGROUND: Actinic keratosis (AK), the most common premalignant skin condition, can represent a management challenge. Treatment should not only be effective, but also well tolerated and allow for good cosmesis on typical sun-exposed highly visible body sites. OBJECTIVES: The primary objective was to compare the lesion response and subject preference for topical methyl aminolaevulinate (MAL)-photodynamic therapy (PDT) vs. cryotherapy for the treatment of AK. METHODS: In this 24-week, multicentre, randomized, intraindividual (right-left) study, subjects received both one treatment session of MAL-PDT and a double freeze-thaw cryotherapy; the treatments were randomly allocated to either side of the face/scalp. Lesions with a noncomplete response were retreated after 12 weeks. The primary assessments were the subject's overall preference and lesion response at week 24. Secondary assessments included lesion response at week 12, cosmetic outcome, subject and investigator cosmetic outcome preference at week 24, and investigator overall preference at week 24. Skin discomfort and adverse events were also evaluated. RESULTS: In total, 119 subjects with 1,501 lesions were included in the study. At week 12, treatment with MAL-PDT resulted in a significantly larger rate of cured lesions relative to cryotherapy (percentage lesion reduction from baseline: 86.9% vs. 76.2%; P < 0.001). At week 24, both treatment groups showed a high rate of cured lesions (89.1% for MAL-PDT vs. 86.1% for cryotherapy; P = 0.20; 95% confidence interval: -1.62 to 7.67). Results for subject and investigator preferences as well as cosmetic outcome favoured MAL-PDT. Both treatment regimens were safe and well tolerated. CONCLUSIONS: The present study shows that, when treated with both MAL-PDT and cryotherapy, subjects significantly prefer MAL-PDT treatment for AK. MAL-PDT is an attractive treatment option for AK, with comparable efficacy and superior cosmetic outcomes compared with double freeze-thaw cryotherapy.

Aged↗
PubMed2005

Cardiac herniation following pneumonectomy--an old complication revisited.

Cardiac herniation is a recognised complication of pneumonectomy when a pericardial defect has been made during resection. This complication is very rare and, with the increasing preference for more limited resections, is even less frequently encountered now than it was several decades ago. Uncorrected cardiac herniation is usually lethal, with a high incidence of morbidity and mortality even after correction. We present a case of left-sided cardiac herniation following intrapericardial pneumonectomy to illustrate the difficulty of making this rare diagnosis. Aetiology, pathophysiology, clinical picture and diagnosis of cardiac herniation are reviewed. We also describe the treatment and prevention of this serious complication. Cardiac herniation should be considered in any patient with acute deterioration after pneumonectomy.

Cardiomyopathies↗
PubMed2003

Adherence to proton pump inhibitors or H2-receptor antagonists during the use of non-steroidal anti-inflammatory drugs.

BACKGROUND: The efficacy of proton pump inhibitors (PPIs) or histamine-2 receptor antagonists (H2RAs) prescribed as prophylaxis for NSAID-related upper gastrointestinal (UGI) toxicity is dependent upon patient adherence. AIM: To describe patient adherence to prophylactically prescribed PPIs and H2RAs in the clinical setting. METHODS: We conducted a retrospective observational cohort study using the Integrated Primary Care Information Project database. The study population consisted of incident non-specific NSAID users prescribed a PPI or H2RA specifically as prophylaxis for NSAID-related UGI toxicity. Patients were classified as non-adherent if < 75% of days of NSAID use were covered by one of these agents, and as continuing users after discontinuation of NSAID use if they had a renewed prescription for these agents after their last NSAID prescription. RESULTS: The study cohort comprised 784 patients: 374 with H2RAs, 405 with PPIs, and 5 with both PPI and H2RA. Eighty-five percent of H2RA users and 7% of PPI users were prescribed these drugs at doses below the minimum recommended/effective dose for NSAID-associated gastroduodenal ulcer prophylaxis. Thirty-seven percent of patients were non-adherent. The lowest rate of non-adherence was associated with the first NSAID prescription (9%), increasing to 61% for patients with >/= 3 prescriptions. In a cohort of subjects who stopped their NSAID and were followed for up to 2 years (n = 711), there was significant persistent use of acid suppressive agents; 40% of patients had at least one additional prescription for the acid suppressive agent after stopping NSAIDs, and> 30% received enough drug to cover a period longer than 2 months after stopping their NSAID. CONCLUSIONS: The pattern of PPI and H2RA prescriptions, when prescribed as prophylactic strategy, does not correspond with the pattern of NSAID use. Physicians should consider the medical impact of non-adherence with dual therapies and the impact of prolonged use of GPAs on treatment cost.

Adult↗
PubMed2003

Detection of scarred and viable myocardium using a new magnetic resonance imaging technique: blood oxygen level dependent (BOLD) MRI.

BACKGROUND: The identification of viable myocardium in patients with impaired left ventricular contraction secondary to coronary heart disease is important clinically as such myocardium is likely to benefit from revascularisation. Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) relies on changes in deoxyhaemoglobin concentration under stress for signal generation and could be used for the differentiation between scarred and viable myocardium. AIM: To assess the signal change on BOLD MRI in viable and scarred myocardium as identified by positron emission tomography (PET). METHOD: 19 patients with impaired left ventricular contraction and at least one akinetic area were enrolled. They underwent rest and dipyridamole stress MRI, using a double breath hold T2* weighted, ECG gated sequence to produce BOLD contrast images, and cine-MRI for wall thickening assessment. Dynamic perfusion and metabolic PET images followed the MRI. Signal change on BOLD MRI and the wall thickening were compared between rest and stress images in hibernating and scarred segments identified by PET on two short axis slices of mid ventricle, with eight segments each. RESULTS: Using PET, 68 segments were identified as hibernating and 42 as scarred. The hibernating segments were found on BOLD MRI to have an average signal change between rest and stress of -9.53%, compared with -2.15% in the scarred segments (p = 0.008). The average wall thickening was 8.7 mm in the hibernating segments compared with 5.9 mm in the scarred segments (p < 0.0001). CONCLUSIONS: BOLD MRI with wall thickening may differentiate scarred and viable myocardium and help identify suitable patients for revascularisation. Further larger studies are needed to establish a threshold for detection, sensitivity, and specificity.

Aged↗
PubMed2002

The mitochondrial 12S gene is a suitable marker of populations of Sarcoptes scabiei from wombats, dogs and humans in Australia.

We sequenced part of the mitochondrial 12S ribosomal RNA gene of 23 specimens of Sarcoptes scabiei from eight wombats, one dog and three humans. Twelve of the 326 nucleotide positions varied among these mites and there were nine haplotypes (sequences) that differed by 1-8 nucleotides. Phylogenetic analyses indicated that these mites were from two lineages: (1) mites from wombats from Victoria, Australia, and mites from the humans and dog from the Northern Territory, Australia (haplotypes 1-4, 9); and (2) mites from the humans and dog from the Northern Territory (haplotypes 5-8). Mites from the three different hosts (wombats, a dog and humans) had not diverged phylogenetically; rather, these mites had similar 12S sequences. Thus, we conclude that these mites from wombats, humans and a dog are closely related, and that they diverged from a common ancestor relatively recently. This conclusion is consistent with the argument that people and/or their dogs introduced to Australia the S. scabiei mites that infect wombats in Australia . So, S. scabiei, which has been blamed for the extinction of populations of wombats in Australia, may be a parasitic mite that was introduced to Australia with people and/or their dogs. These data show that the mitochondrial 12S rRNA gene may be a suitable population marker of S. scabiei from wombats, dogs and humans in Australia.

Animals↗
PubMed2002

Food intake and body measurements of Atlantic bottlenose dolphins (Tursiops truncates) in captivity.

The food consumption (recorded in kg of individual fish species), body length and mass of 11 Atlantic bottlenose dolphins kept first at Windsor Safari Park, UK (1979-1993/1994), and later at Harderwijk Marine Mammal Park, The Netherlands (1993/1994-1995) are reported. This broad-scale, longitudinal study is based on historical data that were originally recorded for short-term husbandry purposes. The chemical composition and caloric value of the diet were variable and were not recorded. The food intake quantities should therefore be viewed as rough weight estimates of what wild conspecifics might eat (depending on their diet). The average annual food consumption of adult males and non-pregnant, non-lactating females was approximately 2000 kg of fish (estimated at 176 x 10(5) kJ). Food consumption showed little increase during gestation, but was 58-97% higher during lactation than during similar periods in non-reproductive years. All six calves began to eat solid food within a year of birth although suckling continued for 14-37 months after birth. The pattern of food intake of mothers and calves varied substantially between suckling periods. No seasonal changes in food consumption were detected, although there were small seasonal changes in water temperature. Births occurred at various times of year, since the timing of mating varied between years. The animals' body length increased rapidly during the first 3 years of life after which the growth rate decreased. Body length reached asymptote at approximately 270 cm. Adults of both sexes weighed around 260 kg. The relationship between standard body length (in cm) and body mass (in kg), although based on a small sample size (n = 16), can be expressed as body mass = 17.261e(0.0156(body length-100)). Animals weighing 155-225 kg consumed between 2 and 4% of their body mass per day.

Animal Husbandry↗
PubMed2001

Does the presence of hibernating myocardium in patients with impaired left ventricular contraction affect QT dispersion?

BACKGROUND: Hibernating myocardium is associated with increased cardiovascular events. Increased QT dispersion on the surface electrocardiogram is a marker for serious ventricular arrhythmias. In this study, we determine whether hibernating myocardium is associated with increased QT dispersion in patients with coronary artery disease and impaired left ventricular contraction. METHODS: Positron emission tomography with (13)N-ammonia and (18)F-fluorodeoxyglucose determined the presence of metabolic-perfusion mismatch defect. QT dispersion was measured by means of a digitizing tablet with validated software. QT intervals were measured on two separate occasions by two investigators blinded to the result of the positron emission tomography scans. RESULTS: Forty-two patients with impaired left ventricular contraction were studied. They were divided into two groups: group A was made up of patients with mismatch defects (n = 26) and group B was made up of patients with no mismatch defects (n = 16). The mean (SD) QT dispersion measurements were 61.7 +/- 29.8 ms and 70 +/- 24.6 ms for groups A and B, respectively (not significant). When the patients were divided according to the dominant viability status of the impaired myocardial segment, a similar result was found. The patients whose impaired myocardium was dominantly hibernating (n = 19) had a mean QT dispersion of 66.4 +/- 31.9 ms compared with 63.6 +/- 24.8 ms in the patients whose impaired myocardium was mainly scarred (not significant). CONCLUSIONS: QT dispersion is not affected by the presence of hibernating myocardium and is therefore not clinically useful in identifying patients with this phenomenon. This is in contrast with recent reports by other groups and calls for further investigation of this dichotomy.

Ammonia↗
PubMed2001

Endothelin-1 during and after cardiopulmonary bypass: association to graft sensitivity and postoperative recovery.

OBJECTIVE: Our objectives are 2-fold: (1) to serially measure the release of endothelin and graft-conduit endothelin sensitivity during and after coronary artery bypass grafting and (2) to define potential relationships of changes in endothelin levels to perioperative parameters. METHODS: Endothelin plasma content was measured in patients (n = 105) undergoing bypass grafting from select vascular compartments before operations and at specific intervals up to 24 hours postoperatively. Endothelin sensitivity was determined in isolated internal thoracic artery segments. RESULTS: Systemic arterial and pulmonary arterial endothelin levels were increased by approximately 50% immediately after bypass grafting and increased by another 85% during the first 24 hours postoperatively. Endothelin levels were highest in patients with prolonged ventilatory requirements and extended stays in the intensive care unit (10.2 +/- 0.8 vs 13.2 +/- 1.1 fmol/mL, P =.02, and 9.8 +/- 0.7 vs 13.9 +/- 1.2 fmol/mL, P =.01, respectively. Endothelin sensitivity of the internal thoracic artery was increased in patients requiring prolonged vasodilator support with nitroglycerin. CONCLUSIONS: Systemic and pulmonary arterial endothelin levels remained increased for at least 24 hours postoperatively. Prolonged pharmacologic management and increased intensive care unit stay were associated with increased systemic endothelin release and heightened graft-conduit sensitivity to endothelin.

Analysis of Variance↗
PubMed2000

Quantitation of rat lacrimal secretion: a novel sandwich ELISA with high sensitivity.

Modulation of lacrimal acinar cell tear secretion may involve multiple factors acting both in subtle and pronounced ways. Functional screens of recombinant protein products arising from gene array technologies, or protein fractions derived from lacrimal conditioned media or extracellular matrix, will require a highly sensitive assay capable of monitoring tear protein secretion by small replicate cultures. To improve significantly on current methods, a rat- and mouse-specific sandwich ELISA was developed. For this purpose, chickens and rabbits were immunized with serum-free secretion media from carbachol and VIP-stimulated rat lacrimal acinar cell cultures. Immune sera were characterized by ELISA, Western blotting and immunohistochemistry, and subsequently optimized for use in a sandwich ELISA. Both antisera detected a wide range of different rat tear proteins, and immunostained only the secretory granule-rich juxtalumenal region in sections of rat lacrimal gland. Chicken, but not rabbit, antiserum cross-reacted with rabbit and human tears. In sandwich ELISA, capture with purified chicken immunoglobulin fraction and detection with rabbit antiserum detected as little as 1 ng ml-1 tear protein in 10,000-fold diluted rat secretion medium--a level of sensitivity 8000 times greater than the rat tear peroxidase assay. Such specificity and sensitivity greatly reduce the quantity of media needed for assay, and makes feasible functional screens for scarce factors that may influence lacrimal secretory processes, and in turn possibly play a role in human lacrimal insufficiency syndromes.

Animals↗
PubMed2000

Adductor spasmodic dysphonia and muscular tension dysphonia: acoustic analysis of sustained phonation and reading.

Acoustic phonatory events were identified in 10 women diagnosed with adductor spasmodic dysphonia (ADSD) and compared to 5 women and 5 men diagnosed with muscle tension dysphonia (MTD). The three acoustic parameters examined during sustained vowel production and reading included phonatory breaks, aperiodicity, and frequency shifts. Intra- and intermeasurer correlations showed high reliability for the measures. Findings indicated that those with ADSD produced a greater number of aberrant acoustic events than those with MTD. The results suggested that: (1) only those with ADSD show evidence of phonatory breaks during vocalization, albeit a sustained vowel or voicing during reading; (2) those with ADSD demonstrate greater variation in the type of aberrant acoustic events produced as a function of speech task. The latter point suggests that control of the larynx varies as a function of task demand, a finding not evident in the functionally based disorder of MTD. MTD is a disorder that often presents itself in a similar clinical manner to ADSD because of its perceptual commonalties and resembling laryngoscopic characteristics. The acoustic analysis presented in this study could be used as a method to assist in distinguishing between the two disorder types.

Acoustics↗