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Biomedical subjects

G McNeill

Publications and source records attributed to G McNeill.

53 records · Page 3Linked to original sources
PubMed1990

Metabolism and nutritional adaptation to altered intakes of energy substrates.

Adaptive changes in energy expenditure to changes in energy intake are far less than previously believed once changes in body weight and physical activity are taken into account. Alterations in metabolic efficiency of +/- 10% in total energy expenditure are the limits of what can normally be expected on prolonged under- or overfeeding. The supposed twofold variation in energy requirements of adults is based on measurements of food intake, which, despite involving weighted intakes over a week, cannot be considered realistic. Subtle differences in the energetic responses to fat, protein, and carbohydrate signify the different effective energetic contribution of isoenergetic substrates and may account for the propensity to obesity in individuals and societies on a high-fat diet.

Adaptation, Physiological↗
PubMed1990

Comparison of a face-mask and a mouthpiece for measuring resting energy expenditure with the 'Oxylog'.

Resting energy expenditure measurements were made simultaneously with an Oxylog and a ventilated hood indirect calorimeter, using (a) the Oxylog with the original oronasal face-mask and (b) the Oxylog with a mouthpiece and a noseclip, both in 15 subjects. The mean difference between Oxylog energy expenditure, when used with the mouthpiece, and ventilated hood measurements was very small: -0.4% (p less than 0.4; n = 15). When used with the face-mask, the Oxylog tended to underestimate energy expenditure relative to the ventilated hood, the mean difference being -2.4% (p = 0.054; n = 13). In 2 subjects, the Oxylog face-mask showed obvious leaks. The subjects did not find the mouthpiece less comfortable than the face-mask, and there was no evidence that the mouthpiece disturbed respiration more than the face-mask. The Oxylog is therefore suitable for measurements of resting energy expenditure, but the use of a mouthpiece and noseclip is preferable to the use of the original Oxylog face-mask.

Adult↗
PubMed1988

The influence of meal composition on post-lunch changes in performance efficiency and mood.

Effects of meal composition on post-lunch changes in performance efficiency and mood were examined. Lunch had an effect on mood, with subjects feeling more lethargic, feeble, clumsy, muzzy, dreamy, bored and mentally slow after the meal. However, the composition of the lunch did not influence this effect. High starch and high sugar meals slowed reactions to visual stimuli presented in the periphery, whereas consumption of a high protein lunch was associated with greater susceptibility to distraction from stimuli close to the target. These results show that protein and carbohydrate meals affect different aspects of attention. That is, the behavioural effects of a meal depend both on its composition and on the particular nature of the activity being carried out.

Achievement↗
PubMed1988

Inter-individual differences in fasting nutrient oxidation and the influence of diet composition.

The pattern of fasting nutrient oxidation was measured in 11 healthy women of widely different body mass index by measurements of indirect calorimetry and urinary nitrogen excretion on 12 consecutive days. The women were given a diet of normal composition (44.5 per cent energy as carbohydrate; 40.7 per cent energy as fat) for 6 days and a high-carbohydrate diet (54.4 per cent energy as carbohydrate; 30.8 per cent energy as fat) for 6 days, in amounts designed to maintain energy balance for each woman. The differences in fasting respiratory quotient (RQ) between the women on the same diet were highly significant (P less than 0.001). The fasting RQ and the fasting carbohydrate and fat oxidation were significantly different between the two dietary periods, with the average difference in fasting RQ (0.027) being of similar magnitude to the difference in the food quotient (FQ) (0.026) between the two diets. The differences in fasting nutrient oxidation between individuals and between diets suggest differences in the extent of overnight carbohydrate storage as glycogen. There was no evidence that these differences were related to the tendency to gain weight in these subjects.

Adult↗
PubMed1988

Whole body lymphangioscintigraphy in ferrets chronically infected with Brugia malayi.

Whole body lymphangioscintigraphy was performed after intradermal injection of 99mtechnetium human serum albumin or antimony colloid in the distal hindlimbs and forelimbs of ferrets chronically infected with Brugia malayi. The findings were compared with control ferrets and those with surgical interruption of the iliac lymphatics. While only one infected ferret manifested chronic hindlimb lymphedema, all exhibited delayed transport of radioisotope from the hindpaw with obstruction in the groin, poor or absent visualization of central lymphatic channels and regional lymph nodes, a picture similar to that following surgically induced lymphatic obstruction. In control ferrets, there was prompt visualization of peripheral lymphatic channels and regional lymph nodes with sharper and more extensive channel visualization after radiolabeled albumin and more intense sustained nodal visualization after radiolabeled antimony colloid. This noninvasive technique provides a readily repeatable investigative tool adaptable to small animals to study the evolution of lymphatic filariasis and other conditions associated with lymphatic obstruction.

Animals↗
PubMed1987

The Oxylog oxygen consumption meter: a portable device for measurement of energy expenditure.

The Oxylog (PK Morgan, Kent, UK) is a recently developed portable device for measurement of oxygen consumption and energy expenditure in man. It incorporates a turbine flowmeter and two polarographic oxygen sensors and is powered by rechargeable batteries. Two instruments were modified for operation at low ventilation rates and used in simultaneous Oxylog and Douglas Bag measurements of resting metabolic rate (RMR) in nine healthy subjects. The coefficients of correlation between RMR measured by the two methods were +0.904 (p less than 0.02) and +0.934 (p less than 0.01) and the standard errors of the mean percent error in energy expenditure were +/- 2.0% and +/- 2.7% for the two instruments respectively. This suggests that the Oxylogs are sufficiently accurate for many field studies of energy expenditure.

Adult↗
PubMed1987

Defective vasodilation response to exercise in cutaneous precapillary vessels in diabetic humans.

Although anatomic abnormalities in capillary structure are well described in diabetes mellitus, physiologic responses of diabetic microcirculation are less clear. This study addresses whether cutaneous vasodilation occurs normally in diabetic subjects in response to a standard exercise of underlying muscle. The methods involve a washout analysis from forearm skin of the fast-moving isotope 133Xe and the diffusion-limited marker 111In-diethylenetriamine pentaacetic acid. Twenty-four normotensive type II diabetic patients of age (mean +/- SE) 59 +/- 1.4 yr were age and weight matched with 24 controls. Control subjects increased flow 50.6 +/- 6.4%, which was not different from the increase in diabetic subjects of 52.7 +/- 7.6%. Permeability-surface-area product (PS) increased in control subjects from 1.77 +/- 0.20 ml.min-1.100 g-1 to 3.79 +/- 0.50 (2P = .0001), whereas diabetic subjects did not show a change in PS (3.29 +/- 0.35 to 2.69 +/- 0.31). Resting PS was higher in diabetic than control subjects (P = .0003), perhaps indicating an already recruited capillary bed. During repetitive exercise, control subjects increased capillary density 125 +/- 27% (2P = .0001) above basal with a nonsignificant 14 +/- 8.4% decrease in mean capillary blood flow. Diabetic subjects responded with a nonsignificant decrease in capillary density and a significant 139 +/- 38% increase in capillary blood flow (2P = .001). It is concluded that, although overall vasodilation occurs normally in diabetic cutaneous circulation, the mechanism is different from the normal response in that flow increases by augmentation of capillary flow rather than by recruitment. This is consistent with the thesis promulgated by others that diabetic precapillary vessels have depressed vasodilatory responses or are already maximally vasodilated. The ability of diabetic subjects to vasodilate by augmentation was not correlated with years of diabetes or use of insulin and only slightly negatively correlated with random blood glucose levels (r = -.423, P less than .05).

Aged↗
PubMed1987

Basal metabolic rate of Indian men: no evidence of metabolic adaptation to a low plane of nutrition.

Basal metabolic rate (BMR) was measured in 58 men of a rural Indian population who had low body weight and body fat stores. Comparisons of subgroups of subjects of different socio-economic status and different nutritional status showed no evidence of differences in BMR when corrected for differences in body weight and body fat content. This suggests that metabolic adaptation did not account for differences in absolute BMR between subgroups of this population. The BMR values agreed well with values predicted by equations based on BMR measurements in Asian men of higher body weight, but were below values predicted by the new FAO/WHO/UNU prediction equations by an average of 12.1 per cent (P less than 0.0001). This overprediction could be a reflection of allometric or climatic influences on BMR rather than evidence for metabolic adaptation to a low plane of energy nutrition.

Adaptation, Physiological↗
PubMed1979

Spindle cell sarcoma of the pulmonary trunk: a case report with histochemistry and electron microscopy.

A further case of a spindle cell sarcoma of the pulmonary trunk is reported, with extension to the pulmonary valve and lungs. Some spindle cells contained glycogen and their cell walls acid mucosubstances. Electron microscopy showed two types of cell. The more common were polyhedral with poorly arranged fibrils in the cytoplasm and an abundant fuzzy coat. About 5 per cent of the cells contained neurosecretory granules.

Cardiovascular System↗
PubMed1975

Comparison of scalar and vector electrocardiographic diagnosis and localization of myocardial infarction.

A prospective study was made of 80 patients during typical clinical episodes of acute myocardial infarction with biochemical and scalar electrocardiographic confirmation. Nine patients had bundle-branch block and 12 had had previous episodes of myocardial infarction. Serial electrocardiograms and vectorcardiograms were recorded during the first week in hospital. The most striking finding was that in more than half the cases there was disagreement between the electrocardiogram and vectorcardiogram in the localizationof infarction. The earliest evidence of infarction in the electrocardiogram is often restricted to ST and T changes though in the corresponding vectorcardiograms evidence of infarction may be present in the QRS loop. In those cases in which both electrocardiogram and vectorcardiogram show QRS abnormalities these are frequently detected earlier in the vectorcardiogram, but the converse is rare.

Bundle-Branch Block↗