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Biomedical subjects

J R Sutton

Publications and source records attributed to J R Sutton.

At least 109 records · Page 6Linked to original sources
PubMed1983

Effect of glycogen depletion on the ventilatory response to exercise.

Five male subjects performed two graded exercise studies, one during control conditions and the other after reduction of muscle glycogen content by repeated maximum exercise and a high fat-protein diet. Reduction in preexercise muscle glycogen from 59.1 to 17.1 mumol X g-1 (n = 3) was associated with a 14% reduction in maximum power output but no change in maximum O2 intake; at any given power output O2 intake, heart rate, and ventilation (VE) were significantly higher, CO2 output (VCO2) was similar, and the respiratory exchange ratio was lower during glycogen depletion compared with control. The higher VE during glycogen depletion was associated with a higher VE/VCO2 ratio, lower end-tidal and mixed venous CO2 partial pressures, and higher blood pH than in the control studies. Changes in exercise VE accompanying glycogen depletion were not explained by changes in CO2 flux to the lungs suggesting that other factors served to modulate VE in these experimental conditions.

Adult↗
PubMed1983

The effects of intravenous infusion of saline on lung density, lung volumes, nitrogen washout, computed tomographic scans, and chest radiographs in humans.

In this study we examined the effect of a 15% increase in extracellular fluid volume on lung density, lung volumes, nitrogen washout, chest radiographs and computerized tomographic (CT) scans of the thorax in 5 volunteers. The objective of the study was to determine the sensitivity of these techniques in detecting small changes in lung water. Lung density was measured by a gamma ray Compton scatter technique and with an Ohio nuclear delta 2020 CT scanner. We measured or derived functional residual capacity, residual volume (RV), vital capacity (VC), and total lung capacity by helium dilution. Single-breath nitrogen washout was used to measure closing volume and the slope of phase III nitrogen washout (delta N2). Chest radiographs were taken in the posteroanterior and lateral projections. With the CT scanner we obtained slices 1 cm thick through the bases of the lungs and at 6 and 12 cm up from the bases. All these measurements were made before and 20 to 90 min after the intravenous infusion of 30 ml/kg body weight of warm saline over a period of 20 min. The most striking findings were a 24% increase in delta N2, a 14% increase in RV, and a 4.5% decrease in VC. Chest radiographs and the CT scans showed an increase in the size of the azygos veins. There was no change in Compton scatter density or the CT numbers. These results suggest that (1) tests of small airway function, such as RV and delta N2, are more sensitive than radiographic techniques to small increases in lung water, (2) there is some protection of the lung to increases in extracellular fluid volume.

Adult↗
PubMed1983

Operation Everest II.

OEII is an ambitious and complex project which is only possible through the full and enthusiastic support of the U.S. Army Institute of Environmental Medicine. The support staff at the hypobaric chamber will man the chamber controls 24 hours a day throughout the study, and full use of laboratories and equipment has been assured. We will maximize the opportunities for research by involving many other scientists active in altitude research, and with widely differing areas of expertise. Many measurements will be made at extreme altitudes which--at least today--are not possible in the mountain environment. Though some may be possible in a hospital setting, using hypoxic patients, OEII is the only method by which the adjustments to graded induced hypoxia can be studied from their beginning. Thus we will not only shed light on the ability of healthy persons to work on the highest point on earth, but also on the mechanisms which permit survival of many seriously ill patients.

Acclimatization↗
PubMed1982

Muscle ultrastructural characteristics of elite powerlifters and bodybuilders.

Muscle ultrastructure of a group of subjects possessing extreme hypertrophy was compared with that of a control group which had undergone 6 months of heavy resistance training. Two needle biopsies were taken from triceps brachii of two international calibre powerlifters and five elite bodybuilders. In addition, samples were taken from five healthy volunteers before and after 6 months of training of the elbow extensors. One biopsy was prepared for electron microscopy and analyzed stereologically, and the other was stained for myosin ATPase activity and photographed under the light microscope. Despite large differences in elbow extension strength and arm girth there was no significant difference in fibre areas or percentages of fibre types between the elite group and the trained controls. This suggests that the elite group possessed a greater total number of muscle fibres than the controls did. Mitochondrial volume density of the elite group was similar to that of the control group following training but significantly less (p less than 0.05) than the pretraining control measurements. Myofibrillar volume density was significantly lower and cytoplasmic volume density significantly higher in the elite group than in the trained controls. There was a considerably higher incidence of structural abnormalities including central nuclei and atrophied fibres in the elite group than in the control group, which might possibly have been associated with the use of anabolic steroids by the elite group.

Adult↗
PubMed1982

Activation by exercise of human skeletal muscle pyruvate dehydrogenase in vivo.

1. The activity of pyruvate dehydrogenase in its active and inactive forms was measured in biopsy samples obtained from the vastus lateralis muscle of healthy subjects before and after exercise. 2. At rest, 40 +/- 4% (mean +/- SEM) of the enzyme was in the active form. 3. After progressive aerobic exercise to exhaustion (n = 5), 88 +/- 2.3% was in the active form. 4. After intermittent supramaximal short-term exercise (1 min exercise, 3 min rest) to exhaustion (n = 6), 60 +/- 2.2% was in the active form. 5. After isometric maximal exercise of 65 +/- 3.6 s duration (n = 3), only 39 +/- 1% of the enzyme was in the active form. 6. Muscle glycogen depletion was greatest with intermittent exercise and least with isometric maximal exercise; in contrast, the increase in muscle lactate was least with progressive exercise (1.3 to 9.4 mumol/g), intermediate in intermittent maximal exercise (1.2 to 13.1 mumol/g) and greatest after isometric exercise (1.8 to 17.6 mumol/g). There were no significant differences between the three studies in the changes in lactate/pyruvate ratios. 7. In three subjects who exercised with one leg, activation of the enzyme was twice as great in the exercise as in the inactive leg. 8. The ratio of active to total enzyme in biopsies of resting muscle was greater in four well-trained athletes than in four untrained control subjects (70% compared with 41% respectively). 9. The activation of pyruvate dehydrogenase appears to play an important part in regulating the use of glycogen and glucose during exercise in man.

Adult↗
PubMed1982

Impaired cardiac "acceleration" at the onset of exercise in patients with coronary disease.

The responses to two levels of exercise (400 and 800 kpm/min) were studied in nine untrained healthy subjects and seven patients with coronary artery disease. Measurements were made over 20-s time intervals to obtain the half times (t1/2) of the asymptotic rise in cardiac frequency (fc), O2 intake (VO2), CO2 output (VCO2), and ventilation (VE). Complete data were obtained in both groups at 400 kpm/min, but only in healthy subjects at 800 kpm/min, as patients were unable to exercise for longer than 2 min at this power. At the onset of 400 kpm/min, t1/2 for VO2 was similar, but t1/2 for fc, VCO2, and VE were all longer in the patients. At 800 kpm/min there was a delay in VO2 in the patients before stopping exercise. In patients and healthy subjects t1/2 for VCO2 and VE, but not VO2, were related to t1/2 for fc. The results emphasized the importance of tissue CO2 storage in attenuating the delivery of CO2 to the lungs and thus delayed the ventilatory response to a step increase in power output.

Adult↗
PubMed1981

High-altitude retinopathy.

Thirty-nine healthy subjects were examined before and after a stay at 5,360 m by ophthalmoscopy and by retinal photography. Twenty of them were also tested for visual acuity, scotomata, and capillary leakage. Vascular engorgement and tortuosity and disc hyperemia were seen in all subjects at altitude and are a "normal" response to hypoxia. Twenty-two (56%) of the subjects had retinal hemorrhages and one showed "cotton-wool spots". These changes are abnormal reactions and are considered high-altitude retinopathy. After maximal exertion on a cycle ergometer, fresh hemorrhages were observed in seven of 34 subjects. The incidence of hemorrhage associated with exercise was significantly greater than predicted. Fluorescein leakage was noted after exercise in eight of 20 persons tested and was associated with exercise-induced hemorrhages. Two persons developed premacular hemorrhages.

Adult↗
PubMed1981

Effect of PH on muscle glycolysis during exercise.

1. Five males were studied on three occasions, after oral administration of CaCO3 (control), NH4Cl (acidosis) and NaHCO3 (alkalosis), in a dose of 0.3 g/kg, taken over a 3 h period at rest. The subjects then exercised on a cycle ergometer for 20 min at 33% maximal oxygen uptake (VO2 max.), followed by 20 min at 66% and at 95% VO2 max. until exhaustion. 2. Endurance at 95% VO2 max. was longest with alkalosis (5.44 +/- 1.05 min), shortest with acidosis (3.13 +/- 0.97 min) and intermediate in the control study (4.56 +/- 1.31 min); venous blood pH at exhaustion was 7.33 +/- 0.02 (mean +/- 1 SEM), 7.13 +/- 0.02 and 7.26 +/- 0.02 respectively. 3. Concentrations of plasma lactate at exhaustion were 7.10 +/- 0.8 mmol/1 4.0 +/- 0.5 and 7.9 +/- 0.9 mmol/l in the control, acidosis and alkalosis studies respectively. 4. Muscle lactate increased most from rest to exhaustion with alkalosis to 17.1 +/- 2.5 mumol/g and least with acidosis to 12.2 +/- 1.4 mumol/g. Muscle glycogen depletion was comparable in control and alkalosis studies. 5. The lower plasma lactate concentration during exercise in acidosis compared with control and alkalosis appears to be due to an inhibition of muscle glycolysis combined with a reduction in lactate efflux from muscle.

Acidosis↗
PubMed1981

Ventilation in exercise studied with circulatory occlusion.

Five male subjects exercised on a cycle ergometer (100 W) for 8 min; circulation to the legs was occluded by cuffs during the first 2 and last 2 min. Ventilation (VE), oxygen intake (VO2), and carbon dioxide output (VCO2) were measured breath by breath. Repeat studies were used to follow arterial PCO2 (PaCO2) and rebreathing mixed venous PCO2 (PVCO2). The results were compared to studies without cuffing, but which were otherwise identical. The initial period of cuffing was associated with marked hyperpnea, high VE/VCO2 ratio, and low PaCO2 and PVCO2. Following release of occlusion at the end of the first 2 min, there was an immediate fall in VE, followed by an increase after an average of 12 s. VE/VCO2 fell and end-tidal PCO2 rose after 4-5 s and reached control values after 12 s. Studies during rebreathing established that CO2 reached the lungs from the legs 4-5 s after release of occlusion, and control PVCO2 was reached after 12 s. Repeated occlusion for the final 2 min of exercise was associated with hyperpnea of similar degree to the initial occlusion. An identical study performed in a patient with absent ventilatory response to CO2 and reduced ventilatory response to exercise showed normal hyperventilatory response to cuffing but did not show an increase in ventilation associated with the arrival of CO2 in the lungs, following release of occlusion. The studies confirmed the importance of CO2 in mediating rapid changes in ventilation during exercise.

Carbon Dioxide↗
PubMed1981

Effects of menstrual cycle on blood lactate, O2 delivery, and performance during exercise.

The effects of the menstrual cycle on cardiorespiratory variables, blood lactate, and performance were studied in exercising females. Nine healthy subjects, 20--24 yr of age, were investigated in midfollicular and midluteal phases of the menstrual cycle at 33, 66, and 90% of maximum power output (light, heavy, and exhaustive exercise). Occurrence of ovulation was confirmed in all subjects by measurement of progesterone, which increased from 0.6 +/- 0.1 (mean +/- SE) in the follicular to 8.9 +/- 2.2 ng/ml in the luteal phase. There was no difference in heart rate (HR), ventilation, O2 uptake, or CO2 output between the two phases during light and heavy exercise, and there was no difference in HR at exhaustion. Cardiac output measured midway through light and heavy exercise periods was not affected by the phase of testing. Time for which exhaustive exercise could be maintained increased from 1.57 +/- 0.32 in the follicular to 2.97 +/- 0.63 min in the luteal phase (P less than 0.02). Blood lactate was higher in the follicular phase after heavy exercise (6.62 +/- 0.8 vs. 4.92 +/- 0.5 mmol/l) (P less than 0.05) and at exhaustion (8.12 +/- 0.9 vs. 6.76 +/- 0.6 mmol/L) (P less than 0.01). A further study showed no effect of cycle phase on lactate disappearance during exercise. We conclude that while aerobic performance and the cardiorespiratory adaptations to exercise are not influenced by the phase of the menstrual cycle, performance of high-intensity exercise is improved, and lactate production appears to be decreased in the luteal phase when estradiol and progesterone levels are elevated.

Adult↗
PubMed1981

Drugs used in metabolic disorders.

Diabetes mellitus is quantitatively the most frequently occurring important metabolic disorder, and exercise has always played an important role in the management of diabetic patients. Exercise increases insulin sensitivity and enhances glucose uptake into muscle. However, the insulin-dependent diabetic is at risk of developing hypoglycemia during exercise. This, in part, is due to the enhanced uptake of insulin from the injection site during exercise and an increased delivery of insulin to the liver, inhibiting hepatic glycogenolysis. Also discussed in this review are drugs, thyroid disease and exercise, anabolic steroids and exercise, glucocorticoids, plasma cortisol and the suppression of cortisol responses to exercise in patients on high-dose steroid therapy.

Adrenal Cortex Hormones↗
PubMed1981

Reasons for dropout from exercise programs in post-coronary patients.

The dropout rate in the 7-yr Ontario Exercise Heart Collaborative Study of post-coronary men engaged in exercise programs was examined in order to determine possible contributing factors. A questionnaire pertaining to psychosocial and program-related variables was distributed to 728 subjects who were previously assigned randomly on the basis of four prognostic risk factors (occupation, personality, hypertension, and angina) into exercise groups: low intensity exercise (LIE), and high intensity exercise (HIE). Comparisons of answers by the 639 respondents (266 dropouts; 373 compliers) were made initially by chi-square analysis to determine significant categories of questions and, subsequently, by a logistic transform to determine the specific questions which related significantly to the dropout rate. It was found that three main categories were associated with a high dropout rate: convenience aspects of the exercise center, perceptions of the exercise program, and family/lifestyle factors. These three main categories should be carefully considered when designing and implementing potential compliance-improving strategies for secondary prevention exercise programs entailing long-term adherence.

Angina Pectoris↗