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Biomedical subjects

G McNeill

Publications and source records attributed to G McNeill.

At least 37 records · Page 2Linked to original sources
PubMed1996

Sensitivity and specificity of QTc dispersion for identification of risk of cardiac death in patients with peripheral vascular disease.

OBJECTIVE: To determine whether QTc dispersion, which is easily obtained from a standard electrocardiogram, can predict those patients with peripheral vascular disease who will subsequently suffer a cardiac death, despite having no cardiac symptoms or signs. DESIGN: Patients with peripheral vascular disease were followed up for five years after they had had coronary angiography, radionuclide ventriculography, and their QTc dispersion calculated from their 12 lead electrocardiogram. SUBJECTS: 49 such patients were then divided into three groups: survivors (34), cardiac death (12), and non-cardiac death (3). MAIN OUTCOME MEASURE: Survival. RESULTS: The mean (SD; range) ejection fractions were similar in all three groups: survivors 45.9 (11.0; 27.0-52.0), cardiac death 44.0 (7.90; 28.5-59.0), and non-cardiac death 45.3 (4.55; 39.0-50.0). QTc dispersion was significantly prolonged in the cardiac death group compared with in the survivors (86.3(23.9; 41.0-139) v 56.5 (25.4; 25.0-164); P = 0.002). A QTc dispersion > or = 60 ms had a 92% sensitivity and 81% specificity in predicting cardiac death, QTc dispersion in patients with diffuse coronary artery disease was significantly (P < 0.05) greater than in those with no disease or disease affecting one, two, or three vessels. CONCLUSIONS: There is a strong link between QTc dispersion and cardiac death in patients with peripheral vascular disease. QTc dispersion may therefore be a cheap and non-invasive way of assessing the risk of cardiac death in patients with peripheral vascular disease.

Aged↗
PubMed1996

Relationship between anthropometric indices of body fat distribution and basal energy metabolism in healthy Maltese women.

A sample taken from a population (Maltese) with a high incidence of the metabolic complications of central obesity was studied to determine: (1) whether the standard Schofield equations adequately predict the basal metabolic rate (BMR) in this population; (2) whether the Maltese have a greater tendency for central obesity compared with other populations; (3) whether the distribution of body fat influences energy expenditure and fuel selection. Healthy women responding to a public advertisement were sampled randomly from the Maltese population. Correlation analysis and analysis of variance were used to study relationships between BMR and body composition. Anthropometric parameters (including body fat distribution indices, bioimpedance) and BMR were measured after an overnight fast. Six percent of the respondent were excluded because of recent illness, instability of diet or of body weight. Fifty subjects attended a clinic at the Medical School. The distribution of excess fat between central and peripheral areas in the Maltese population was similar to that reported for the British population. The Waist-hip ratio (WHR) reflected neither basal heat production (BMR) nor the contribution of fat oxidation to BMR. The Schofield equations systematically underestimated BMR by 5.4% +/- 0.86% (P < 0.05). The study suggests a limitation in using the Schofield equations for predicting BMR in the female Maltese population studied. It also suggests that the fat distribution between central and peripheral areas in this population has no effect on BMR.

Adipose Tissue↗
PubMed1996

The effect of protein intake on 24-h energy expenditure during energy restriction.

OBJECTIVE: To investigate whether protein intake influences the decline in energy expenditure during energy restriction. DESIGN: Cross-over study of three diets of 4.2 MJ/d for 7 days: one diet with 36% energy as protein and two with 15% energy as protein, one high in carbohydrate and the other high in fat. SUBJECTS: Two men and six women aged 31-57 y. BMI 27.B-34.1 kg/m2. MEASUREMENTS: 24-h energy expenditure (24-h EE), sleeping metabolic rate (SMR) and body weight on days 0 and 7 of each diet; 24-h urinary nitrogen excretion (24-h UN) on days 0-7 of each diet. RESULTS: 24-h EE and SMR declined on all three diets but the decrease was significantly less on the high protein diet than on the two low protein diets. Weight loss was similar on all three diets. 24-h UN was less than N intake on the high protein diet but greater than N intake on the two low protein diets. CONCLUSIONS: Maintaining protein intake reduces the decrease in energy expenditure during energy restriction.

Adult↗
PubMed1996

Comparisons between fat measurements by dual-energy X-ray absorptiometry, underwater weighing and magnetic resonance imaging in healthy women.

OBJECTIVE: To compare the results of measurements of total and regional fat by dual-energy X-ray absorptiometry (DXA), underwater weighing (UWW) and magnetic resonance imaging (MRI) in women. DESIGN: 13 volunteer pre-menopausal women measured with a Norland XR26 HS DXA instrument, hydrodensitometry equipment and a 0.08 Tesla MRI scanner. SETTING: Aberdeen Royal Infirmary. RESULTS: There were high correlations between measurements of total-body fat by the different techniques, but poor agreement. The mean values of fat as a percentage of the total body mass were UWW = 28.6%, DXA = 40.0%, MRI = 23.0%, although the MRI excluded the head, forearms and feet, estimated from the DXA measurements to contain 8% of the body fat. Although the correlations were apparently linear in the ranges examined, those including the Norland DXA had high intercepts. Bland and Altman plots showed no dependence of the differences on the degree of fatness. Evidence was obtained from in vivo comparisons and phantom measurements that the fat calibration of the Norland DXA had changed during a three year period, suggesting that fat calibration errors contributed to the MRI/DXA differences. Previous comparisons between the Norland DXA and other brands indicate that Hologic and Lunar instruments would show a closer agreement with MRI and UWW. Profiles of fat distribution along the body showed variations in the DXA/MRI ratio, particularly in the chest, with the DXA pattern thought to be the less accurate. The DXA measurements of bone mineral, fat and lean tissue were used to demonstrate the variable proportion of bone in fat-free tissue, leading to errors in UWW. CONCLUSIONS: Each method has its assumptions, which are often not sufficiently appreciated. Each method may be useful for testing and improving the assumptions in the other methods. No method can yet be regarded as a satisfactory reference technique.

Absorptiometry, Photon↗
PubMed1995

Energetic consequences of mild Giardia intestinalis infestation in Mexican children.

This study explored the effects of mild infestation with Giardia on energy intake and expenditure at rest and in activity in an urban Mexican population. Ten boys aged 6-10 y living in low-income sectors in northwest Mexico who had Giardia infestation were recruited. Energy intake, basal metabolic rate (BMR), and total free-living expenditure (TEE) measured by the doubly labeled water method were determined for 7 d during both infestation and after treatment. There was no significant difference in recorded energy intake between the two periods (7.76 and 7.70 MJ/d; P = 0.847). BMR showed no significant change in response to treatment; values were 4.79 and 4.86 MJ/d (P = 0.03). The mean TEE increased by almost 1 MJ/d in the Giardia-free period. This increase was observed in 8 of the 10 subjects; however, the overall change was not statistically significant (P = 0.08).

Animals↗
PubMed1994

The influence of exercise on the energy requirements of adult males in the UK.

Energy expenditure was measured over 10 d using the doubly-labelled water (DLW) and activity diary methods in summer and winter in subjects with 'light' occupations but leisure activities which ranged from 'non-active' to 'very active'. The basal metabolic rate (BMR) and the energy cost of activities were determined by indirect calorimetry. The Department of Health (1991) predicted BMR for the group (6.89 (SD 0.30) MJ/d; n 18) was not significantly different from the measured value (7.17 (SD 0.70) MJ/d; n 18). The range of DLW-derived expenditure values within the group was BMR x 1.41 to 2.41. The largest seasonal change within individuals was BMR x 0.5. The energy expenditure of the group as a whole was lower in winter (BMR x 1.88; SD 0.33; n 9) than summer (BMR x 2.01; SD 0.30; n 9) though the difference was not statistically significant. The average summer and winter DLW-derived expenditure was BMR x 1.96 (SD 0.31; n 17). The activity diary estimate of expenditure was BMR x 1.79 (SD 0.32; n 17). In a subset of the group who were representative of the most active 26% of all adult males in the UK, the DLW-derived expenditure was BMR x 2.08 (SD 0.24; n 11). This is higher than the highest Department of Health (1991) estimate of BMR x 1.6 for individuals in light occupations. The measured energy costs of low-intensity activities were similar to those presented in the Department of Health (1991) report but the value determined for running (BMR x 13.08; SD 2.4; n 6) was higher than the highest value in the report (BMR x 6 to 8). The results indicate that the recent Department of Health (1991) reference values for energy may underestimate the expenditure of a significant proportion of the UK population largely because the energy costs of activity used in the report to calculate expenditure do not accurately reflect those achieved during active leisure in individuals who take regular exercise.

Adult↗
PubMed1994

Imaging techniques for the assessment of body composition.

Three imaging methods, ultrasound imaging (UI), computer-assisted axial tomography (CAT) and magnetic resonance imaging (MRI), are widely used in medicine. Their application to the assessment of body composition in nutrition research is still being explored and developed. Ultrasound imaging yields poor image quality but, because it is cheap and safe, deserves further exploration. Both CAT and MRI can produce images with good discrimination among bone, muscle and adipose tissue. Movement artifacts tend to be more serious in MRI than in CAT due to the longer imaging time. On the other hand, the X-ray exposure in CAT is likely to limit its use in human nutrition research. Repeated measurements of tissue volumes by CAT and MRI give similar CV. In both CAT and MRI, intra-abdominal adipose tissue presents greater problems of measurement than subcutaneous adipose tissue. Validation studies with 77-kg pigs of MRI, using 13 slices, predicted total body lipid with residual standard deviation of 1.9%. In validating any of these methods, account should be take of the extent to which the information they give can augment that given by more simple measures like age and weight.

Animals↗
PubMed1994

Basal metabolic rate and body fatness of adult men in northern Mexico.

To investigate the possibility that overprediction of basal metabolic rate (BMR) of tropical populations is related to differences in fatness between tropical and temperate populations, 32 Mexican men aged 18-40 years underwent measurements of BMR and body fat content. The men were divided into four body mass index (BMI) groups (< 20, 20-25, 25-30 and 30-40). The mean weight was 78 (range 52-119) kg and the mean height was 1.75 (range 1.61-1.89) m. BMR was measured in the subjects after an overnight stay in a residential unit by a Deltatrac ventilated hood indirect calorimetry system. Body fat content was determined by 2H2O dilution. The relationship between BMR and body weight was analysed by linear regression and the equations derived were compared to the values predicted using the FAO/WHO/UNU (1985) equations. The FAO/WHO/UNU equations overestimated measured BMR by 9.8%, 9.6%, 7.8% and 5.5% in the four groups. The overall difference was 8.2%, which was statistically significant (P < 0.001). The intercepts of the two equations were significantly different (P < 0.001) by 532 kJ/day, but there was no significant difference between the slopes of the two regression equations. There was no significant difference between BMR/kg fat-free mass in the four BMI groups. The results therefore do not support the possibility that the overprediction of BMR in tropical populations by international prediction equations based on body weight is accounted for by differences in fatness between tropical and temperate populations.

Adipose Tissue↗
PubMed1992

The effect of environmental temperature and humidity on 24 h energy expenditure in men.

The effects of environmental temperature and humidity and their interaction on 24 h energy expenditure were measured using whole-body indirect calorimetry in eight normal-weight young men who wore standardized light clothing and followed a controlled activity regimen. A randomized-block experimental design was used, with temperature effects assessed by measurements at 20, 23, 26 and 30 degrees, while humidity was altered from ambient (50-65% relative humidity) to high (80-93% relative humidity) at 20 and 30 degrees only. There was no significant effect of humidity on 24 h energy expenditure at the two extreme temperatures in this range, though when periods of sleep and exercise were excluded the energy expenditure at high humidity was significantly higher than that ambient humidity (P < 0.02). The effect of temperature at ambient humidity levels showed lower values at 23 and 26 degrees than at 20 and 30 degrees (P < 0.02). The effect of temperature was not equally apparent in all components of the 24 h energy expenditure, as sleeping metabolic rate and the energy cost of walking and cycling showed no significant effect of temperature over this range. This raises the possibility that the effects of temperature are attributable to behavioural changes during the waking portion of the day rather than any non-shivering thermogenic mechanisms at tissue level.

Adult↗
PubMed1992

Lymphatic imaging in experimental filariasis using magnetic resonance.

RATIONALE AND OBJECTIVES: To evaluate acquired lymphatic abnormalities caused by filariasis, the authors examined the peripheral lymphatic system in normal ferrets and those chronically infected with Brugia malayi using magnetic resonance imaging (MRI). The findings were compared with previously obtained lymphangioscintigraphic (LAS) images in ferrets both with and without experimental filariasis. METHODS: Fifteen ferrets (11 infected with B. malayi and four noninfected controls) underwent whole body coronal MRI using a quadrature transmission-receive head coil at 0.5 Tesla operating at a resonant frequency of 21.5 mHz for protons with a 25-cm field of view. RESULTS: In contrast to normal animals, infected ferrets showed dilated hindlimb dermal lymphatic collaterals, enlarged high-signal intensity groin lymph nodes with punctate low-signal intensity centers and separate low-signal intensity spots with irregular thin channels, suggestive of nests of viable adult nematodes within tortuous lymphatics and nodes. MRI correlated with the LAS findings, and the interpretations were supported by light, scanning electron, and video microscopy. CONCLUSIONS: T2-weighted MRI in conjunction with LAS accurately depicts the peripheral lymphatic system in filarial-infected ferrets. These two modalities are useful complementary techniques to examine disorders characterized by lymphatic insufficiency.

Animals↗
PubMed1991

Influences of meal size on post-lunch changes in performance efficiency, mood, and cardiovascular function.

This study examined the effects of the size of the meal on post-lunch changes in attention, mood, blood pressure and pulse. Thirty-five females subjects were tested before and after lunch. One group (n = 12) were than given a normal-sized lunch, another (n = 11) were given a lunch designed to contain 40% more energy than their individual requirement and the third group (n = 12) had a lunch with an energy content 40% less than the estimated requirement. After lunch all groups of subjects reported that they felt more feeble, dreamy and bored, and less alert, excited, clear-headed, energetic, quick-witted, friendly, sociable and elated. However, the size of the meal did not alter the extent of the pre/post-meal differences. Similarly, there was no effect of meal size on pulse rate or blood pressure, although pre/post-meal differences were observed. In contrast, subjects who had a larger lunch than normal made more errors on focussed attention and search tasks (especially the search task) than those who had a normal-sized lunch or one which was smaller than normal.

Adult↗
PubMed1991

Body fat in lean and overweight women estimated by six methods.

Body fat content of seven lean women (body mass index (BMI) 20.6 (SD 1.8) kg/m2) and seven overweight women (BMI 31.1 (SD 3.3) kg/m2) was estimated by six different methods: underwater weighing (UWW), body-water dilution (BWD), whole-body counting (40K), skinfold thickness (SFT), bioelectrical impedance (BEI) and magnetic resonance imaging (MRI). Using UWW as the reference method, the differences between percentage fat by each other method and the percentage fat by UWW were calculated for each subject. The mean difference was lowest for SFT and highest for BWD. MRI showed the lowest variability in individual results, and 40K the highest. 40K and BWD methods used in combination gave better agreement with UWW results than either 40K or BWD methods alone. There was a weak negative correlation between the difference from the UWW results and percentage fat in the SFT measurements, but not in the BWD, 40K, BEI or MRI measurements, suggesting that for these methods the assumptions involved produced no greater inaccuracy in the overweight women than in the lean women. In all subjects the BEI offered little improvement over the traditional SFT measurements. The agreement between MRI and UWW estimates in both lean and overweight women suggests that MRI may be a satisfactory substitute for the more established methods of body fat estimation in adult women.

Adipose Tissue↗
PubMed1991

Total and subcutaneous adipose tissue in women: the measurement of distribution and accurate prediction of quantity by using magnetic resonance imaging.

Total and subcutaneous adipose tissue in seven lean and seven obese women were quantified using magnetic resonance imaging (MRI). The distributions of adipose tissues along the body were closely correlated: subcutaneous with total, both within and between lean and obese groups. Lean women had proportionally less adipose tissue in the lower thorax and upper abdomen than did obese women. Reducing the number of MRI scans from 17 to 4 did not increase the residual SD of predicted body adipose tissue (2.9 percent) when body density was used as the reference measure. MRI gave an estimate of total-body adipose tissue significantly closer to the value for fat percent produced when the results from five other techniques (skinfold thickness, underwater weighing, 40K whole-body counting, isotopic water dilution, and tetrapolar bioelectrical impedance) were averaged than when any other technique was used alone. MRI-determined percent body adipose tissue in women is close to, and proportional to, estimates derived by underwater weighing.

Abdomen↗
PubMed1991

Postprandial thermogenesis in post-obese women and weight-matched controls.

Postprandial thermogenesis was assessed on two occasions in six weight-stable post-obese women, with a mean weight loss of 21.9 (range 10.1-43.3) kg, and six control subjects who had never been overweight. The two groups of subjects were closely matched for weight, height, body mass index and age. The energy load of the test meal was proportional to each subject's energy requirement. Energy expenditure was monitored for 40 min before and 245 min after the meal by ventilated hood indirect calorimetry. Mean baseline energy expenditure was 3.65 (s.e.m. 0.22) kJ/min in the post-obese, and 3.73 (s.e.m. 0.17) kJ/min in the control subjects (P greater than 0.5). Mean postprandial energy expenditure was 4.50 (s.e.m. 0.25) kJ/min in the post-obese women and 4.61 (s.e.m. 0.18) kJ/min in the control women (P greater than 0.5). The mean thermic response, expressed as percentage of baseline energy expenditure, was 23.5 per cent (s.e.m. 1.4 per cent) in the post-obese and 24.1 per cent (s.e.m. 1.6 per cent) in the control subjects (P greater than 0.5). When expressed as percentage of the meal energy, the response was 7.9 per cent (s.e.m. 0.4 per cent) in the post-obese, and 7.4 per cent (s.e.m. 0.4 per cent) in the control subjects (P greater than 0.1). Reproducibility of duplicate measurements of postprandial thermogenesis, estimated as within-subject coefficient of variation, was 16.6 per cent when expressed as percentage increase over baseline energy expenditure, and 16.4 per cent when expressed as percentage of meal energy ingested. The present results do not support an impaired postprandial thermogenesis in women with a tendency to obesity, and suggest that part of the controversy in this field may be due to differences in study design and to the poor reproducibility of this measurement.

Adult↗
PubMed1990

Effect of vitamin and mineral supplementation on verbal and non-verbal reasoning of schoolchildren.

In a randomised controlled trial the effect of vitamin and mineral supplementation for seven months on performance in tests of reasoning was studied in 86 schoolchildren aged 11-13. A small, non-significant difference between the control and supplementation groups was found in a non-verbal test. The net difference in change in scores between the active and placebo groups was 2.4 units (95% CI-1.5 to 6.3). This direction of effect was not consistently seen with three other tests of non-verbal reasoning. Vitamin and mineral supplementation does not improve the performance of schoolchildren in tests of reasoning.

Administration, Oral↗