PubMed Health⌕ Search

Biomedical subjects

A C MacDonald

Publications and source records attributed to A C MacDonald.

At least 37 records · Page 2Linked to original sources
PubMed1985

Studies of bile lipids and bile acids of wild North American black bears in Nova Scotia, showing a high content of ursodeoxycholic acid.

Does ursodeoxycholic acid (UDC) production protect hibernating species of Ursidae against gallstone disease? Five wild bears (Ursis Americana) were studied. Older bears had more UDC than younger ones, suggesting UDC production is an acquired phenomena. Bile salt pools were 10 times larger than that of man and were characteristically conjugated with Taurine alone. The relative composition of the principal lipids in bear bile fell well within the range of cholesterol solubility. Cholesterol gallstones are not reported in Ursidae, probably because of the large bile acid pool and high UDC content.

Animals↗
PubMed1985

The zinc, copper, and selenium status of a selected sample of Canadian elderly women.

The zinc, copper, and selenium status of 90 noninstitutionalized Canadian elderly women (M age = 70.3 years) in a university community and consuming self-selected diets was assessed using hair and serum trace element levels and dietary trace element intakes. Mean (+/- SD) serum zinc and copper levels (analyzed via atomic absorption spectrophotometry, AA) were 1.09 +/- 0.13 and 1.22 +/- 0.29 micrograms/ml, respectively. Mean serum selenium (+/- SD) (analyzed via instrumental neutron activation analysis (INAA) was 0.115 +/- 0.03 micrograms/ml. Median hair trace element values, analyzed via INAA, were 156 for zinc, 12.8 for copper, and 0.63 micrograms/g for selenium. Mean (+/- SD) daily dietary intakes determined via chemical analysis of 1-day diet duplicates were 1.2 +/- .06 mg/d for copper (via AA), 7.6 +/- 3.3 mg/d and 77.6 +/- 44.5 micrograms/d for zinc and selenium (via INAA), respectively, whereas mean copper and zinc intakes (+/- SD) calculated from 3-day records were 1.6 +/- 0.7 and 10.1 +/- 3.5 mg/day, respectively. Median hair and serum trace element values were above the levels associated with deficiencies. Thus the zinc, copper and selenium status of these elderly women appeared adequate.

Aged↗
PubMed1985

Dietary chromium and manganese intakes of a selected sample of Canadian elderly women.

Energy, manganese and chromium intakes of a selected sample of 90 free-living Canadian women (mean age 66.2 +/- 6.2 years) living in a university community and consuming self-selected diets were assessed by chemical analyses of 24-h duplicate diets and via three-day dietary records, collected by the subjects. Mean gross energy intake (determined via bomb calorimetry) was 6.0 +/- 2.4 MJ (1435 +/- 580 kcal) and mean intake of manganese (determined via atomic absorption spectrophotometry) was 3.8 +/- 2.1 mg/day, respectively. Mean and median chromium intakes, analysed via instrumental neutron activation analysis were 96.4 and 77.4 micrograms/day, respectively. The manganese and chromium densities of these diets were higher compared to diets for pre-menopausal women studied earlier, attributed in part to the higher (P less than 0.0003) median intake of tea (360 g) vs 180 g for the pre-menopausal women. No significant differences between the pre and post-menopausal groups in mean intakes (in g) of any other food groups investigated, were found. Silver-plated cutlery may also be a source of adventitious chromium in the diets of these post-menopausal subjects. Nevertheless 22 per cent of the subjects had chromium intakes based on one day duplicate diets, below the US suggested safe limit, which if representative of their habitual chromium intakes, may result in chromium depletion.

Aged↗
PubMed1983

Estimation of ursodeoxycholic acid in human and bear biles using Clostridium absonum 7 beta-hydroxysteroid dehydrogenase.

Ursodeoxycholic acid was estimated in bile samples from humans and wild North American black bears using 7 beta-hydroxysteroid dehydrogenase purified from Clostridium absonum by Procion Red affinity chromatography. The percentage ursodeoxycholic acid was calculated by two methods: (a) 7 beta-hydroxyl groups were quantified using 7 beta-hydroxysteroid dehydrogenase and 3 alpha-hydroxyl groups (total bile acids) were quantified using 3 alpha-hydroxysteroid dehydrogenase. The percentage ursodeoxycholic acid was calculated on the basis of [7 beta-hydroxyl groups]/[3 alpha-hydroxyl groups] X 100. (b) Bile was hydrolyzed with sodium hydroxide and subjected to thin-layer chromatography. Bands corresponding to cholic acid, chenodeoxycholic acid plus deoxycholic acid, and ursodeoxycholic acid were identified by the use of standards and Komarowsky's spray reagent. Total bile acids and total ursodeoxycholic acid were measured by elution of silica gel in unsprayed areas corresponding to the bile acid standards and quantification of the total bile acid in each eluate. Direct comparison of these methods validated the use of 7 beta-hydroxysteroid dehydrogenase in the estimation of ursodeoxycholic acid in the biles of black bears and of patients fed ursodeoxycholic acid for cholesterol gallstone dissolution. Relative percentages of ursodeoxycholic acid were 8-24% in four bears and 22 and 27% in the patients ingesting 500 and 750 mg ursodeoxycholic acid per day for 3 months, respectively. Predictably lower values were obtained in two control subjects and one patient ingesting 750 mg chenodeoxycholic acid per day for 3 months.

Animals↗
PubMed1981

Left ventricular function during graded exercise in patients with coronary artery disease and in control subjects.

The left ventricular function of 30 patients with coronary artery disease and 11 control subjects was studied by electrocardiography gated cardiac blood pool scintigraphy as the participants lay on their backs and either rested or exercised on a cycle ergometer at graded levels on intensity. The control subject showed a progressive increase in ejection fraction from rest (51% +/- 7%) to intermediate (56% +/- 10%, P less than 0.05) and maximum levels of exercise (64% +/- 10%, P less than 0.001). All the patients showed a decrease in ejection fraction from rest (42% +/- 16%) to their maximal level of exercise (36% +/- 11%, P less than 0.001). However, the response of some of the patients to intermediate exercise ranged from a decrease or no change to an increase in ejection fraction. Thus, exercise at maximal intensity is necessary to induce the left ventricular dysfunction that is diagnostic of coronary artery disease.

Coronary Disease↗
PubMed1981

Improved long-term survival following myocardial revascularization in patients with severe left ventricular dysfunction.

The natural history of patients with coronary artery disease associated with poor left ventricular (LV) function is dismal. This report analyzes the efficacy of myocardial revascularization in this subset of patients with coronary artery disease manifesting severe LV dysfunction on the basis of LV angiography, LV ejection fraction (LVEF), and left ventricular end-diastolic pressure (LVEDP). For the 2 1/2 year period ending November, 1977, 59 consecutive patients with coronary artery disease complicated by severe LV dysfunction underwent aorta-coronary bypass at the University of Western Ontario. All patients had angina refractory to medical therapy. Objective criteria for compromised LV function included the presence of three or more dysfunctional (hypokinetic of akinetic) segments on biplane LV angiography. Eighty-three percent (49/59) of patients had triple-vessel coronary artery disease. The mean LVEF for the series was 0.28 and the mean LVEDP was 18 mm Hg. The duration of follow-up was 24 to 60 months (mean 37 months), with follow-up survival data available on 100% of patients. The hospital mortality was 1.7% (1/59), and there were nine late deaths. The 5 year actuarial survival rate (+/- SEM) was 80% +/- 6%. Of the 44 long-term survivors available for direct assessment, 98% (43/44) report improvement with respect to angina and 66% (29/44) are totally asymptomatic. Eighty percent (28/35) of the long-term survivors under the age of 65 years are currently employed. These results indicate that myocardial revascularization can be performed in patients with severe ischemic LV dysfunction at very low risk and, further, that operation results in a dramatic improvement in survival expectations compared with optimal medical therapy.

Aged↗
PubMed1979

Hepatic blood flow and metabolism.

The relationship between liver blood flow and hepatic metabolism remains unclear. An animal model as well as a methodology that permits simultaneous assessment of both of these functions are proposed. Several fractions of inspired oxygen were used to produce arterial oxygen levels commonly seen in clinical practice; these ranged from hyperoxemia to established hypoxemia. Over this range there were no considerable changes in transhepatic blood flow, but there were considerable changes in hepatic metabolism as shown by measurements of the hepatic parenchymal pH, transhepatic oxygen consumption, and lactic acid use. Of these, the parenchymal pH seems to be the most sensitive indicator of metabolic events.

Animals↗
PubMed1979

Low-cost comprehensive data system for cardiac patients.

Functional systems to collect, store and retrieve clinical, hemodynamic, and angiographic information are needed to serve clinical research and quality control in the cardiac laboratory. Computers are ideally suited for this application, but high investment and maintenance costs are a barrier for their wider use. A low-cost data processing and procedure reporting system was developed using a programmable calculator, a floppy disk drive, and a printer. Files have been started on 750 consecutive adult patients undergoing cardiac catheterization and angiography. Each file contains a clinical profile (CP), angiographic interpretation (Al), and hemodynamic data. CP and Al are coded according to a data base definition appropriate for patient care (procedure report) and research analysis. Data input is simplified by the use of multiple choice forms and prompts appearing on the calculator alphanumeric display. One floppy disk may hold 400 patient files. Immediate access to stored information for cross reference, computations, and statistical work is possible in all patients, a patient category, or an individual case. Stored items may be retrieved in coded form for analysis or translated into sentences to generate a multiple-copy procedure report. Follow-up information may be subsequently added to the patient file. Operation requires minimal training and little expertise in computer technology.

Coronary Disease↗
PubMed1979

Exercise electrocardiography and myocardial perfusion imaging in the diagnosis of coronary artery disease: preliminary report.

Exercise electrocardiography and rest/exercise myocardial perfusion imaging with thallium-201 were performed in 43 patients with typical angina or atypical chest pain; the results were correlated with those of coronary arteriography. Exercise electrocardiography sensitivity was 65%, specificity was 78%, predictive value for a positive result was 73% and for a negative result was 93%. The low sensitivity of the exercise electrocardiogram was mainly due to the number (13 of 43, 30%) of inconclusive results (no ST-segment change on the electrocardiogram, but failure to attain the target rate), most of which were in the group with typical angina. The predictive value of exercise electrocardiography for both a positive and negative result was excellent in typical angina. In patients with atypical chest pain, the negative predictive value was high (90%) but the positive predictive value was very low (50%). The sensitivity of myocardial perfusion imaging was 71%, specificity was 59%, positive predictive value was 52% and negative predictive value 89%. The low specificity of this test is related to the number of false-positive results obtained, most of which occurred in the group with atypical pain. When the results of exercise electrocardiography and myocardial perfusion imaging are combined, the sensitivity is increased but specificity is unacceptably low. However, myocardial perfusion imaging in patients with an inconclusive result from exercise electrocardiography (most of them in the group with typical angina) showed a sensitivity of 80%, specificity of 88%, positive predictive value of 80% and negative predictive value of 100%.

Coronary Circulation↗
PubMedDate not supplied

Use of 5 French catheters for cardiac catheterization and coronary angiography: a critical review.

With the number of outpatient cardiac catheterizations increasing, much attention has recently been focused on the use of 5 French catheters for cardiac catheterization and selective coronary angiography. However, there are few reports in the literature regarding the technical aspects of their use or the quality of cineangiograms obtained. We reviewed our experience with these catheters in our first 100 consecutive cases. All cineangiograms were diagnostic, though 9% were deemed only of fair quality (incomplete luminal filling in some frames) by two experienced observers. Technical problems encountered with the use of these catheters included instability of the right Judkin's catheter in the right coronary ostium owing to high torquability, streaming of contrast during left coronary injections, and difficulty entering the left ventricle with a pig-tail catheter.

Cardiac Catheterization↗
PubMedDate not supplied

Molybdenum requirements in low-birth-weight infants receiving parenteral and enteral nutrition.

BACKGROUND: Molybdenum (Mo) is an essential trace element required by three enzymatic systems, yet there are no reports of Mo deficiency in infants. Low-birth-weight infants (LBW) might be at risk for Mo deficiency because they are born before adequate stores for Mo can be acquired, they have rapid growth requiring increased intakes, and they frequently receive supplemental parenteral nutrition (SPN) and total parenteral nutrition (TPN) unsupplemented with molybdenum. METHODS: To investigate Mo requirements of LBW infants (n = 16; birth weight, 1336+/-351 g; gestational age, 29.8+/-2.5 weeks; M+/-SD), the authors collected all feeds, urine, and feces prior to TPN (baseline, n = 16, collections = 16), during TPN (n = 9, collections = 19), during SPN (n = 13, collections = 17), and after one week of full oral feeds (FOFs) of formula or human milk (FOF, n = 16, collections = 16). RESULTS: Infant weights at collection times were: 1.3+/-0.3 g, 1.27+/-0.4 g, 1.4+/-0.3 g, and 1.7+/-0.5 g, respectively. Mo intake was 0.03+/-0.1 microg/d, 0.34+/-0.1 microg/d, 1.25+/-1.7 microg/d, and 6.1+/-2.5 microg/d. Mo output was 0.64+/-0.6, 0.34+/-0.5, 0.68+/-0.8, and 4.1+/-2.5 microg/d. Mo balance at these times was -0.60+/-0.5, -0.001+/-0.5, 0.57+/-1.9, and 2.0+/-2.9 microg/d. Mo balance increased with time, yet some infants were always in negative balance, even though Mo intakes exceeded recommendations. CONCLUSIONS: The authors speculate that an intravenous intake of 1 microg/kg/d (10 nmol/kg/d) and an oral intake of 4-6 microg/kg/d (40-60 nmol/kg/d) would be adequate for the LBW infant.

Enteral Nutrition↗