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Biomedical subjects

R A Wilson

Publications and source records attributed to R A Wilson.

At least 235 records · Page 13Linked to original sources
PubMed1985

Effect of a delay in commencing imaging on the ability to detect transient thallium defects.

Sixty patients, 42 with coronary disease and 18 normals, were studied to assess the impact of a delay following exercise in commencing thallium imaging on the sensitivity for detecting ischemic transient defects. Three sets of images were obtained beginning 2 min, 18 min, and 2 hr after exercise. Each patient's images were separated into two pairs of studies for analysis: 2 min-2 hr and 18 min-2 hr. Of the 42 patients with coronary disease, a greater number had transient defects detected on the 2 min-2 hr compared with the 18 min-2 hr study (22 compared with 14, p less than 0.05). False positives were not increased by earlier imaging. We conclude that a modest (18 min) delay obtaining the first set of images causes a significant reduction in the ability to detect transient thallium defects, and that imaging should begin several minutes after exercise.

Adult↗
PubMed1984

Transient ST-segment depression as a marker of myocardial ischemia during daily life.

Patients with angina and coronary artery disease (CAD) have many episodes of transient ST-segment depression during ordinary daily life, and these are often asymptomatic. To investigate this signal as a marker of myocardial ischemia, 30 patients with chronic stable angina and CAD underwent positron tomography, recording the regional myocardial uptake of rubidium-82, pain and ST-segment changes before, during and after 59 technically satisfactory exercise tests, 35 cold pressor tests and 22 episodes of unprovoked ST depression. Exercise resulted in 53 episodes of ST depression with angina and in 5 episodes without pain. After cold pressor tests, there were 3 episodes of ST depression and pain and 12 of painless ST depression. Only 9 episodes of unprovoked ST depression were accompanied by pain. Tomography showed independent evidence of ischemia in 63 (97%) of the total 65 episodes of ST depression with angina and in all 30 episodes of painless ST depression. In each patient perfusion defects occurred in the same myocardial segment during painful and painless ST depression and responses were significantly different from those in 16 normal subjects studied in the same way. These findings support the use of transient ST depression in continuous monitoring to assess the activity of CAD, but only in patients with typical angina pectoris, ST depression during exercise and proved CAD. They strengthen the evidence derived from ambulatory monitoring for a wider picture of the disease than is generally appreciated, with more frequent episodes of silent myocardial ischemia than of angina pectoris.

Adult↗
PubMed1984

Silent myocardial ischaemia due to mental stress.

Patients with angina and coronary disease have many episodes of symptomless transient myocardial ischaemia, most of which cannot be explained by physical exertion. 16 patients with typical stable angina pectoris were examined to test the hypothesis that these episodes can be triggered off by ordinary daily events, such as changes in mental activity. Regional myocardial perfusion and ischaemia were assessed by measurement of the uptake of rubidium-82 with positron tomography after mental arithmetic and physical exercise. With mental arithmetic, 12 (75%) patients had abnormalities of regional perfusion, accompanied in only 6 by ST-segment depression and in 4 of these 6 by angina, leaving 6 patients with perfusion abnormalities but neither pain nor electrocardiographic changes. After exercise, all the patients showed abnormal regional myocardial perfusion in the segments that became ischaemic with mental arithmetic. This was accompanied by ST depression in all and angina in 15. The association between mental activity and myocardial ischaemia may operate frequently during everyday life and may explain many of the transient and symptomless electrocardiographic changes in patients with coronary disease.

Activities of Daily Living↗
PubMed1984

Preparation of human serum [methyl-11C]methylalbumin microspheres and human serum [methyl-11C]methylalbumin for clinical use.

Safely-injectable suspensions of human serum [methyl-11 C] methylalbumin microspheres have been prepared via the reaction of human serum albumin microspheres with [11C]methyl iodide, itself prepared in a novel one-pot synthesis from cyclotron-produced [11C]carbon dioxide. The preparation takes only 30 min from the end of radionuclide production and proceeds in 22% radiochemical yield based on the activity of [11C]carbon dioxide used and decay-corrected. It has been shown that such microspheres are highly stable in vivo and may be used as reference blood flow markers in positron emission tomography (PET). Similarly, safely-injectable and radiochemically pure solutions of human serum [methyl-11C] methylalbumin have been prepared in 31% radiochemical yield and in 40 min from the end of [11C]carbon dioxide production via the reaction of [11C]methyl iodide with human serum albumin. This radiopharmaceutical is intended for studies of lung permeability and blood-brain barrier permeability by PET.

Animals↗
PubMed1984

Schistosoma mansoni: cellular reactions to challenge infections in the cheek pouch skin of chronically infected Chinese hamsters.

The cellular reactions to the migration of challenge schistosomula of Schistosoma mansoni through the cheek pouch skin in Chinese hamsters immunized 20 weeks previously via the abdomen has been investigated at the ultrastructural level. The composition of the leucocytic infiltrate into the dermis and epidermis changed with time after infection. At 24 and 48 h the infiltrate was composed mainly of neutrophils and mononuclear cells. At 72 h fewer neutrophils but more eosinophils were present. The interaction of the leucocytes with the challenge schistosomula is described. Degranulation of eosinophils at the cell-parasite interface has been observed. Despite the fact that approximately 30% of 48 h schistosomula and 50% of 72 h schistosomula examined had adherent leucocytes only a few of the parasites exhibited signs of damage, consisting of tegumental vacuolation and changes in the electron opacity of the tegumental cytoplasm. There was no strong evidence of increased attrition of challenge schistosomula in the cheek pouch skin relative to the primary infection, although some dead challenge parasites were observed. It is concluded that a substantial proportion of the attrition of challenge infections in the Chinese hamster occurs at a post-dermal location.

Animals↗
PubMed1984

Validation of quantitation of regional myocardial blood flow in vivo with 11C-labeled human albumin microspheres and positron emission tomography.

Use of radiolabeled microspheres is a standard method to measure regional myocardial perfusion in animals. Human albumin microspheres have been given safely to patients, but positron-emitting 68Ga-labeled human albumin microspheres are characterized by an unstable radiolabel. A new labeling procedure that covalently binds 11C (t1/2 = 20.3 min) to human albumin microspheres via 11CH3I was developed. Seven open-chest and two closed-chest dogs were studied. Reference and 11C-labeled human albumin microspheres (2 to 25 mCi) were both injected into the left atrium. Positron tomographic images were obtained of the myocardial distribution of the 11C-labeled microspheres. Timed arterial withdrawal was used for both reference gamma-labeled microspheres and 11C-labeled human albumin microspheres. Myocardial tissue samples matched to tomographic slices were well-counted for calculation of reference values of regional myocardial perfusion. Serial venous blood samples for residual 11C activity of 30 and 60 min after injection were less than 1% of the myocardial 11C concentration demonstrating a stable 11C bond to the human albumin microspheres. Regional myocardial perfusion calculated by this technique correlated well with values obtained with reference microspheres (r = .97) over a range of 0.2 to 3.5 ml/min/g. Correction for wall thickness improved the slope of the regression equation from y = 0.71 x -0.03 to y = 0.88 X -0.05. Thus, 11C human albumin microspheres are stable radiochemically and can be used as a quantitative measure of regional myocardial perfusion.

Animals↗
PubMed1984

Changing validity of the cirrhosis mortality--alcoholic beverage sales construct: U.S. trends, 1970-1977.

Data on cirrhosis mortality and alcoholic beverage sales were studied for the period 1970-1977 in the U.S. The relationship between cirrhosis mortality and sales was examined by sex and by type of beverage (beer, wine or distilled spirits). Time-series analyses showed that, during this period, total cirrhosis mortality decreased an average of 1.5% per year, sales increased 0.7% per year and alcohol-related cirrhosis mortality increased 2.6% per year. In any given year, however, these factors were highly correlated. Also, the relative ranking of the states remained stable, suggesting internal consistency of record-keeping. Misestimates of cirrhosis mortality based on sales were examined. Cross-sectional data indicated that sales were positively related to cirrhosis mortality but time-series analyses suggested that increases in sales were associated with decreases in total cirrhosis mortality and increases in the percentage of alcohol-related cirrhosis mortality. Time-series and regression analyses suggested the strong influence of factors external to the basic sales--cirrhosis mortality model and suggested that multiple indicators would be better than cirrhosis mortality and sales, alone or in combination, to estimate the magnitude of alcohol problems.

Alcoholic Beverages↗
PubMed1984

Biochemical and serologic properties of Escherichia coli isolated from cows with acute mastitis.

Biochemical and serologic characteristics of 184 Escherichia coli isolates from cows with acute mastitis were determined. Trends or patterns unique to bovine isolates were not observed, except for the frequency of adonitol fermentation, which was positive in 84 (45.6%) of the cultures. Growth on Tergitol-7 agar had 3 types of colony morphologic characteristics; of these, the rough and intermediate textures predominated over those with smooth colony surfaces. A large variety of serovars was detected; the majority occurring as single isolates within a herd. Few K antigens were typeable. Only 2 isolates contained the K99 antigen. Seemingly, E coli organisms isolated from cows with acute mastitis cannot be distinguished as a specific pathogenic group on the basis of biochemical and serotest reactions.

Acute Disease↗
PubMed1983

An ambulatory ventricular function monitor: validation and preliminary clinical results.

A device for the continuous measurement of left ventricular (LV) function was tested in a series of 34 subjects. The instrument consisted of 2 arrays of radiation sensitive cadmium telluride detectors held in place over the region of the left ventricle and lung by a vest-like garment (hence the name VEST). The VEST electronic instrumentation included analog-to-digital converters, a battery pack, microprocessor and gating device, which were worn in a back pack. Data generated by the VEST, including the digitized average electrocardiogram, RR interval, counts/13 ms in each radiation detector, and time since commencement of data recording, were recorded on a cassette tape recorder every 2 minutes for subsequent analysis. At the conclusion of conventional multigated blood pool imaging, the VEST was positioned and worn by the subjects while supine, standing in place and walking. The correlation of ejection fraction calculated independently from the VEST and scintillation camera data was greater than 0.95. The inter-record reproducibility of the ejection fraction measured by the VEST in sedentary subjects was less than 3%.

Ambulatory Care↗
PubMed1983

Radionuclide-determined changes in pulmonary blood volume and thallium lung uptake in patients with coronary artery disease.

UNLABELLED: Exercise-induced increases in radionuclide-determined pulmonary blood volume (PBV) and thallium lung uptake have been described in patients with coronary artery disease (CAD) and have been shown to correlate with transient exercise-induced left ventricular dysfunction. To compare these 2 techniques in the same patients, 74 patients (59 with and 15 without significant CAD) underwent supine bicycle exercise twice on the same day--first for thallium myocardial and lung imaging and then for technetium-99m gated blood pool imaging for the PBV ratio determination. Thallium activity of lung and myocardium was determined to calculate thallium lung/heart ratio. Relative changes in PBV from rest to exercise were expressed as a ratio of pulmonary counts (exercise/rest). Previously reported normal ranges for thallium lung/heart ratio and PBV ratio were used. The PBV ratio and thallium lung/heart ratio were abnormal in 71 and 36%, respectively, of patients with CAD (p less than 0.01). Both ratios were normal in all patients without CAD. Although the resting ejection fractions did not differ significantly in patients with normal versus those with abnormal PBV ratios or thallium lung/heart ratios, abnormal PBV ratios and thallium lung/heart ratios were associated with an exercise-induced decrease in ejection fraction. Propranolol use was significantly higher in patients with abnormal than in those with normal thallium lung/heart ratios (p less than 0.01). No significant difference in propranolol use was present in patients with abnormal or normal PBV ratios. IN CONCLUSION: (1) the prevalence of an abnormal thallium lung/heart ratio is less than that of the PBV ratio in patients with CAD; (2) both tests are normal in normal control subjects; (3) propranolol does not cause abnormal results in normal control subjects; however, propranolol may influence lung thallium uptake in patients with CAD; and (4) when both tests are abnormal, there is a high likelihood of multivessel disease.

Adult↗
PubMed1983

Tegument surface membranes of adult Schistosoma mansoni: development of a method for their isolation.

Several approaches to surface membrane stripping have been applied to the adult schistosome. Membrane removal was evaluated by the use of different extrinsic and intrinsic markers of which alkaline phosphatase proved to be the most reliable. After initial studies employing incubation of worms in buffer alone, Triton X-100 or freeze/thaw, the last method was chosen for development. The final method applies a single freeze/thaw step to adult worms in balanced salt solution followed by short bursts of agitation on a vortex mixer to release the tegument. Differential and density gradient steps subsequently yield a final membrane pellet enriched over 130 times in surface alkaline phosphatase. The method has been characterized during its development using electron microscopy and enzyme markers for contaminant worm fractions.

Alkaline Phosphatase↗
PubMed1983

Identification of exposed components on the surface of adult Schistosoma mansoni by lactoperoxidase-catalysed iodination.

Adult schistosomes have been labelled with 125I using the lactoperoxidase-catalysed technique modified to cause minimal worm damage. After surface membrane removal and characterization, at least 13 labelled proteins were identified together with a large amount of labelled glycolipids, free fatty acids and phospholipids, especially phosphatidyl ethanolamine. Cationised ferritin has been used to stimulate surface membrane turnover of iodinated worms and the shedding of covalently bound 125I-counts used as an index of turnover. Finally worms have been iodinated before and after stimulation of membrane turnover in chemically defined media and the patterns of labelled proteins were compared.

Alkaline Phosphatase↗
PubMed1983

Schistosoma mansoni: migration and attrition of irradiated and challenge schistosomula in the mouse.

The fate of irradiated, immunizing cercariae and challenge schistosomula was investigated in mice using a quantitative, histological technique which would appear to be more efficient in estimating parasite numbers in skin and lungs than does the tissue mincing and incubation recovery technique used previously by other workers. There was evidence for slight retardation of irradiated (20 krad.) parasite migration in skin, but death of schistosomula in the skin appeared negligible. It was observed that the majority of irradiated parasites remained in the lungs until at least day 21 after infection, and that most schistosomula observed at this time were dead. In mice immunized with irradiated cercariae there was no evidence of attrition of the challenge infection in the skin. The migration profile of challenge parasites in the lungs of immunized animals was not significantly different from that of normal parasites in the lungs of naive animals. Dead challenge parasites were observed in the lungs but their numbers were not considered great enough to account for the final attrition measured by perfusion. It is suggested that the remainder of the attrition of challenge schistosomula may occur in the systemic and/or hepatic portal circulation.

Animals↗
PubMed1983

The relationship between the age of Schistosoma mansoni cercariae and their ability to penetrate and infect the mammalian host.

The ability of the cercariae of Schistosoma mansoni to penetrate the tails of mice was shown to remain constant throughout their lives. However, their capacity to establish themselves and then reach maturity decreased as they aged. The abdominal route of penetration produced consistently higher maturation rates than the tail route. Significantly different maturation rates were obtained by modifying the standard tail infection technique. Evidence is presented that age-related mortality of schistosomula occurs within 24 h of penetration and may be associated with the exhaustion of energy reserves during the penetration of the stratum corneum. The relationship of this age-related mortality to 'mass mortality' is discussed.

Age Factors↗
PubMed1983

Exercise testing in asymptomatic or minimally symptomatic aortic regurgitation: relationship of left ventricular ejection fraction to left ventricular filling pressure during exercise.

Exercise radionuclide angiography is being used to evaluate left ventricular function in patients with aortic regurgitation. Ejection fraction is the most common variable analyzed. To better understand the rest and exercise ejection fraction in this setting, 20 patients with asymptomatic or minimally symptomatic severe aortic regurgitation were studied. All underwent simultaneous supine exercise radionuclide angiography and pulmonary gas exchange measurement and underwent rest and exercise measurement of pulmonary artery wedge pressure (PAWP) during cardiac catheterization. Eight patients had a peak exercise PAWP less than 15 mm Hg (group 1) and 12 had a peak exercise PAWP greater than or equal to 15 mm Hg (group 2). Group 1 patients were younger and more were in New York Heart Association class I. Group 1 patients also had a higher mean rest ejection fraction (0.64 +/- 0.08 vs 0.49 +/- 0.13, p less than 0.01, higher exercise ejection fraction (0.63 +/- 0.10 vs 0.40 +/- 0.18, p less than 0.01), lower end-systolic volume (38 +/- 13 vs 79 +/- 36 ml/m2, p less than 0.01) and higher peak oxygen uptake (24.9 +/- 5.1 vs 16.6 +/- 4.9 ml/kg/min, p less than 0.01) than group 2 patients. However, the two groups had similar cardiothoracic ratios, changes in ejection fractions with exercise, and rest and exercise regurgitant indexes. Using multiple regression analysis, the best correlate of the exercise PAWP was peak oxygen uptake (r = -0.78, p less than 0.01). No other measurement added significantly to the regression. When peak oxygen uptake was excluded, rest and exercise ejection fraction also correlated significantly (r = -0.62 and r = -0.60, respectively, p less than 0.01). Patients with asymptomatic or minimally symptomatic severe aortic regurgitation have a wide spectrum of cardiac performance in terms of the PAWP during exercise. The absolute rest and exercise ejection fraction and the level of exercise achieved are noninvasive variables that correlate with exercise PAWP in aortic regurgitation, but the change in ejection fraction with exercise by itself is not.

Adolescent↗