Biomedical subjects
Publications and source records attributed to J Cannon.
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BACKGROUND AND PURPOSE: Proton magnetic resonance spectroscopy (MRS) can be used to study metabolite abnormalities in the brains of stroke patients. We have used it to examine the relations between the metabolites in the infarct (N-acetylaspartate [NAA] and lactate) and the time lapse from stroke to MRS, the presenting neurological deficit, infarct size and swelling (on MRI), blood flow to the infarct (estimated by transcranial Doppler ultrasound), and clinical outcome. METHODS: Patients with symptoms of a moderate to large cortical infarct underwent serial proton MRS (Siemens 1.5 Magnetom) within 4 days, from 5 to 10, and from 11 to 35 days after the stroke. A long echo time PRESS single voxel or chemical shift imaging acquisition was used. Transcranial Doppler ultrasound was performed daily in the first week and twice per week thereafter until the final MRS. Clinical features and baseline demographic data were collected independently by a stroke physician and 6-month outcome by postal questionnaire. RESULTS: Fifty patients underwent at least 1 MRS examination. Reduced NAA in the infarct within the first 4 days was related to the clinical stroke syndrome, more extensive infarction, more severely reduced blood supply to the infarct, and the presence of lactate. The presence of lactate was related to large infarcts and reduced NAA. Swelling in the infarct was most closely associated with large infarcts and reduced blood supply but not reduced NAA or the presence of lactate. Clinical outcome was most closely related to the extent of the infarct (more than to the clinical syndrome)--the larger the infarct the worse the outcome--but not to the metabolite concentrations alone. CONCLUSIONS: The reduction in NAA (but not the presence of lactate) in a visible infarct was related to the reduction in blood flow to the infarct, which in turn was related to infarct extent and clinical outcome.
OBJECT: The authors sought to determine whether the increased pulsatility of aneurysms, compared with normal intracranial arteries, on color "power" transcranial Doppler (TCD) ultrasound was due to a true change in aneurysm size and whether aneurysm dimensions change with intracranial pressure (ICP). METHODS: The authors studied nine patients who had suffered recent subarachnoid hemorrhages complicated by hydrocephalus requiring intraventricular cerebrospinal fluid drainage, in whom the presence of an aneurysm was confirmed on angiographic examination. Color "power" TCD studies of the intracranial arteries and aneurysm were obtained through the temporal bone window before and after insertion of the ventricular drain and then at different known ICPs. Of the nine patients studied, four were examined both before and after insertion of a ventricular drain. At high ICPs, aneurysms appeared very "pulsatile" and the maximum cross-sectional area was small, whereas at low ICPs, aneurysms appeared larger and were much less pulsatile. The normal arteries did not change significantly in terms of pulsatility or maximum cross-sectional area at different levels of ICP. CONCLUSIONS: The change in aneurysm size visualized with the aid of color power TCD is likely to be real. Aneurysm dimensions vary with ICP levels; the lesions are larger and less pulsatile at low ICPs and smaller but more pulsatile at high ICPs.
alpha-Amylase and hemicellulase, derived from culture of Aspergillus species, are commonly added to flour as improvers during baking. Two cases of women occupationally sensitized to alpha-amylase who developed allergic symptoms after eating baked bread have been reported. With a randomized, controlled study design, we have investigated whether similar responses occur in those sensitized to Aspergillus species. Seventeen subjects with positive skin prick tests to Aspergillus fumigatus were studied. Symptomatic and physiologic responses after ingestion of bread baked with alpha-amylase and hemicellulase were compared, in a crossover fashion, with those after ingestion of bread baked without enzymes. No increase in respiratory or other symptoms, lung function, or nonspecific bronchial hyperreactivity was reported after ingestion of the enzyme-containing bread. We conclude that important clinical reactions to alpha-amylase and hemicellulase in baked bread do not frequently occur in those sensitized to Aspergillus species.
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We studied the reproducibility of metabolite signals (from N-acetyl aspartate [NAA], choline, and creatine) measured with a standard single-voxel proton magnetic resonance spectroscopy technique (PRESS, TE = 135 ms, 8 ml VOI) in vitro and in two groups of normal volunteers. Spectral peak areas were quantified both by integration and by curve-fitting. In the in vitro study, the "between-days" variability (coefficient of variation [CV]) of measurements ranged from 0.9% to 2.3%. In the first group of volunteers (n = 12), single voxel spectroscopic measurements (8 ml VOI, 256 acquisitions [ACQs]) were made from mirror-image parts of the right and left hemispheres on 2 separate days. The "between-days" CV of measurements ranged from 9% to 18% for metabolite areas, and from 10% to 26% for metabolite area ratios. There were no significant differences between quantification method or hemisphere. After checking and optimising the MR scanner performance (in fact, it was virtually optimal), the second group (n = 4) each had six sequential single voxel spectroscopic measurements (each of 64 ACQs) from the right hemisphere (without moving the voxel) on each of 4 separate days. Even when the metabolites were measured from the same place in the same hemisphere sequentially six times in a 20-min period, the "within-run" CVs ranged from 4.4% to 17.2% for metabolite areas and from 9.7% to 17.0% for metabolite area ratios. The between-days CVs for the subjects ranged from 7.7% to 25.8% (metabolite areas) and from 10.1% to 22.6% (metabolite area ratios). The variability is due to a combination of random noise, subject motion, baseline artefacts in the spectra, and uncertainties in repositioning the VOIs. It is likely to represent the best reproducibility possible with 8-ml VOIs in cooperative, healthy volunteers carefully positioned on each occasion in a standard clinical scanner. Changes in metabolite levels in individuals must therefore be of the order of 20-40% before we can be reasonably confident of measuring them. Reproducibility in patients, who may be less cooperative, will probably be no better, and this must be taken into account in the interpretation of MRS studies in patients with brain pathology; for example, stroke, head injury, and tumours.
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Occupational asthma in two women employed in the manufacture of condoms is reported. The spores of Lycopodium clavatum, used as a rubber dusting agent, were identified as the causative agent.
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The relationship between the cyclophosphamide metabolite acrolein and hemorrhagic cystitis is well documented. Its role in inducing bladder cancer is not clear. There are at least 35 cases of cyclophosphamide-associated bladder cancer in the literature to date. We report 3 additional cases of transitional cell carcinoma of the bladder. Literature assessing the relative risk of bladder cancer associated with cyclophosphamide therapy is reviewed as are methods for decreasing the toxic effects on the urothelium of the metabolite acrolein.
The hypothesis tested in this study was that despite the presence of severe postischemic myocardial dysfunction ("stunning"), the extraction and subsequent intracellular washout of thallium 201 should be preserved as long as irreversible sarcolemmal membrane injury was avoided. To produce myocardial stunning, 19 open-chested dogs with a critical left anterior descending coronary artery (LAD) stenosis underwent 10 5-minute periods of total LAD occlusion, each interspersed by 10 minutes of reperfusion by reflow through the critical stenosis. In another 12 control dogs observed for the same time period, no LAD occlusions were performed after placement of the critical stenosis. Hemodynamics, regional myocardial thickening by quantitative two-dimensional echocardiography, and microsphere-determined regional blood flows were serially measured. In 18 stunned dogs, systolic thickening in the LAD zone was markedly reduced to 0.4 +/- 2.4% at 40 minutes after the 10th reperfusion period compared with 32.5 +/- 2.2% thickening (p less than 0.001) in 12 control dogs at a matched time. The 201Tl first-pass extraction fraction determined by a double-isotope method using intracoronary 201Tl administration was comparable after the 10th reflow in a subgroup of 13 stunned (0.78) and six control (0.79) dogs. The T1/2 for the intracellular washout rate was also not significantly different in another group of six stunned (60 +/- 13 minutes) and six control (53 +/- 14 minutes) dogs, nor was the percentage of the 201Tl dose initially distributed in the interstitial compartment (11 +/- 3% vs. 7 +/- 2%). Systemic hemodynamics and regional flows were comparable in the two groups at 40 minutes after the 10th reflow. No dog had evidence of myocardial necrosis by triphenyl tetrazolium chloride staining. Thus, normal myocardial 201Tl extraction and washout kinetics are observed in a canine model of severe postischemic dysfunction (stunning) produced by repetitive brief LAD occlusions. These findings might have important clinical implications concerning the application of rest 201Tl scintigraphy for evaluation of perfusion and viability in patients with coronary artery disease and regional myocardial asynergy that is ultimately reversible.
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