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Biomedical subjects

R R Wolfe

Publications and source records attributed to R R Wolfe.

At least 163 records · Page 9Linked to original sources
PubMed1993

Exercise increases muscle GLUT-4 levels and insulin action in subjects with impaired glucose tolerance.

A decline in insulin sensitivity is associated with aging, inactivity, and obesity. The effects of exercise training on glucose homeostasis independent of weight loss in older glucose-intolerant individuals are not well established. We examined the effects of exercise training on oral glucose tolerance, insulin action, and concentration of the GLUT-4 glucose transporters in skeletal muscle. Exercise training at 50 and 75% of heart rate reserve was performed for 12 wk in 18 individuals (age = 64 +/- 2, body fat = 37.0 +/- 1.5%). Peripheral insulin action was determined 96 h after the last exercise bout using a two-step hyperinsulinemic-euglycemic glucose clamp (insulin = 192 and 708 pmol/l). Percent body fat and fat-free mass (FFM) were unchanged with training. Diet composition, assessed by diet record, did not change over the 12 wk. Improved oral glucose tolerance was observed, as exhibited by lower plasma glucose concentrations after training (P < 0.05), whereas plasma insulin response remained unchanged. The rate of glucose disposal was unchanged during the low insulin concentration but increased 11.0% at the high insulin concentration (P < 0.05) after training (54.4 +/- 4.4 vs. 60.4 +/- 5.5 mumol.kg FFM-1.min-1). Skeletal muscle glycogen and GLUT-4 concentration increased 24 and 60%, respectively, with training. There was no direct relationship between the change in GLUT-4 protein and the change in glucose disposal rate. These findings demonstrate that chronic exercise training without changes in body composition improves peripheral insulin action in subjects with impaired glucose tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration.

Stable isotope tracers and indirect calorimetry were used to evaluate the regulation of endogenous fat and glucose metabolism in relation to exercise intensity and duration. Five trained subjects were studied during exercise intensities of 25, 65, and 85% of maximal oxygen consumption (VO2max). Plasma glucose tissue uptake and muscle glycogen oxidation increased in relation to exercise intensity. In contrast, peripheral lipolysis was stimulated maximally at the lowest exercise intensity, and fatty acid release into plasma decreased with increasing exercise intensity. Muscle triglyceride lipolysis was stimulated only at higher intensities. During 2 h of exercise at 65% VO2max plasma-derived substrate oxidation progressively increased over time, whereas muscle glycogen and triglyceride oxidation decreased. In recovery from high-intensity exercise, although the rate of lipolysis immediately decreased, the rate of release of fatty acids into plasma increased, indicating release of fatty acids from previously hydrolyzed triglycerides. We conclude that, whereas carbohydrate availability is regulated directly in relation to exercise intensity, the regulation of lipid metabolism seems to be more complex.

Adult↗
PubMed1993

Strenuous endurance training increases lipolysis and triglyceride-fatty acid cycling at rest.

Basal whole body lipid kinetics were evaluated in nine endurance-trained cyclists and 10 untrained healthy controls. The rate of appearance (Ra) of glycerol (an index of whole body lipolysis), the Ra of palmitate (an index of fatty acid release), and the rate of triglyceride-fatty acid cycling (reesterification of fatty acids released during lipolysis) were determined by infusing [2H5]glycerol and [2H2]palmitate in conjunction with indirect calorimetry. All subjects were studied while they were at rest after fasting overnight. Glycerol Ra and free fatty acid Ra in the athletes (7.33 +/- 0.68 and 14.88 +/- 1.35 mumol.kg-1 x min-1, respectively) were two- to threefold higher than the values in untrained control subjects (2.53 +/- 0.15 and 7.64 +/- 0.92 mumol.kg-1 x min-1, respectively; P < 0.02). The total rate of triglyceride-fatty acid cycling was approximately four-fold higher in the athletes (16.86 +/- 2.07 mumol.kg-1 x min-1) than in the control subjects (3.91 +/- 0.36 mumol.kg-1 x min-1). Plasma concentrations of insulin and catecholamines, hormones that regulate whole body lipid kinetics, were the same in both groups. We conclude that resting basal lipid kinetics are markedly increased in athletes involved in strenuous endurance training and that this enhances the potential for increasing fatty acid oxidation rapidly at the onset of exercise.

Adult↗
PubMed1993

Urea kinetics in humans at two levels of exercise intensity.

A primed constant infusion of [15N2]urea was used to quantify the response of urea production to exercise at 40 and 70% maximal oxygen consumption on a treadmill. Total urea production, urea production from recycled N, urea production from nonrecycled N, and urea N recycled back into body protein were calculated. Most components of urea kinetics were unaffected by exercise at either intensity. The rate of urea reincorporated into protein was significantly increased during exercise and recovery at both levels of exercise. We conclude that exercise does not stimulate urea production but that there may be an accelerated reincorporation of urea N back into body protein.

Adult↗
PubMed1993

Measuring intrasubject variability: use of the jacknife in doubly labeled water experiments.

The doubly labeled water technique measures energy expenditure; however, very little has appeared in the literature regarding estimation of the intrasubject variation. By use of a statistical resampling procedure called the jackknife, the standard deviation of the determination of energy expenditure in each subject is evaluated. Jackknife methods exploit the regression techniques that are already used with the doubly labeled water technique and are very easy to implement. Estimates of sample sizes for future experiments can easily be done with the jackknife. These formulas give the number of determinations of isotopic enrichment of hydrogen and oxygen over time that are needed to achieve a given degree of accuracy in estimating energy expenditure. An example with two human subjects illustrates the methodology of the jackknife.

Body Water↗
PubMed1993

Circulating immunoreactive endothelin-1 in children with pulmonary hypertension. Association with acute hypoxic pulmonary vasoreactivity.

To determine whether circulating levels of endothelin-1 (ET-1), a potent vasoconstrictor peptide, are elevated in children with pulmonary hypertension and related to the degree of hypoxic pulmonary vasoconstriction, we measured arterial and mixed venous plasma concentrations of immunoreactive ET-1 (irET-1) in 13 children during cardiac catheterization. Clinical diagnoses in seven children with pulmonary hypertension (PH) included chronic lung disease (four children), congenital heart disease after surgical repair (two children), and primary ("reactive") pulmonary hypertension (one child). Blood samples were simultaneously obtained from pulmonary artery (venous) and systemic arterial sites during baseline conditions. Plasma irET-1 was elevated in children with PH (12.3 +/- 3.4 versus 3.6 +/- 0.7 pg/ml, PH versus non-PH; p < 0.01). Arterial/venous irET-1 ratios in the PH group (1.1 +/- 0.2) were not different from those in the non-PH group. During acute hypoxia, mean Ppa increased from 27 +/- 3 to 40 +/- 5 mm Hg. Basal irET-1 correlated strongly with the degree of elevation of mean Ppa during acute hypoxia (r = 0.69; p < 0.02). We conclude that irET-1 levels are often elevated in children with PH, and they are strongly correlated with pulmonary vasoreactivity during acute hypoxia. Whether elevated irET-1 levels contribute directly to or are markers of altered pulmonary vascular tone and reactivity in children with PH remains speculative.

Blood Pressure↗
PubMed1993

Short-term effects of tumor necrosis factor on energy and substrate metabolism in dogs.

In vivo short-term effects of recombinant human TNF-alpha on lipolysis, FFA flux, fat oxidation, triglyceride-fatty acid cycling, and glucose kinetics were evaluated with stable isotopic tracers and indirect calorimetry along with monitoring of hemodynamic parameters in fasted dogs. High-dose TNF infusion (10 micrograms/kg) caused a fall in mean arterial pressure (P < 0.01), pulmonary arterial pressure (P < 0.001), and cardiac index (CI) (P < 0.05). The rate of appearance of glycerol (Ra glycerol) and the rate of appearance of FFA (Ra FFA) were decreased by 20% (P < 0.05) and by 42% (P < 0.01), respectively. Total fat oxidation fell by 23% (P < 0.05). In contrast, TNF infusion significantly increased glucose production by 13% (P < 0.05) and metabolic clearance rate of glucose by 25% (P < 0.01). However, TNF infusion did not change energy expenditure. Low-dose TNF infusion (3.5 micrograms/kg) caused changes similar in all respects, except magnitude, to the high-dose effects. There was a significant correlation between percent change of CI (delta CI) and percent change of rate of appearance of palmitate (Ra palmitate; delta Ra palmitate) (P < 0.0001, r = 0.69), Ra FFA (delta Ra FFA) (P < 0.0001, r = 0.60), and Ra glycerol (delta Ra glycerol) (P < 0.0329, r = 0.36). The correlation between delta CI and delta Ra palmitate was greater than the correlation between delta CI and delta Ra glycerol (P = 0.028). We conclude that the acute response to TNF causes a shift towards carbohydrate as an energy substrate in a dose-dependent manner by both decreasing the availability of FFAs and increasing glucose production.

Animals↗
PubMed1993

Metabolic response to burn injury: nutritional implications.

The response to critical illness involves alterations in all aspects of metabolic control, favoring catabolism of stored energy substrates and protein. Glucose production is accelerated, due principally to a chronic elevation in glucagon. Whereas glucose is available at increased rates, the muscle tissue is less responsive than normal to the stimulatory effect of insulin on glucose uptake. Stored triglyceride is also catabolized at a high rate, predominantly due to enhanced adrenergic activity. This causes the release of free fatty acids at a rate well in excess of their requirement for oxidation, leading to a high rate of reesterification and triglyceride transport in plasma. Protein metabolism is characterized by accelerated catabolism that is not balanced by a corresponding increase in synthesis. Whereas the mechanism for this response is not known, peripheral insulin resistance does not appear to be responsible.

Burns↗
PubMed1993

Cardiorespiratory responses to exercise of patients with aortic stenosis, pulmonary stenosis, and ventricular septal defect.

BACKGROUND: The purpose of this study was to determine exercise tolerance and cardiac response to exercise for a large cohort of adult subjects with aortic stenosis, pulmonary stenosis, or ventricular septal defect participating in the Second Natural History Study of Congenital Heart Defects (NHS-2). METHODS AND RESULTS: Exercise testing was performed on 134 of 235 NHS-2 full participants with aortic stenosis, 195 of 331 NHS-2 full participants with pulmonary stenosis, and 324 of 594 NHS-2 full participants with ventricular septal defect. A Bruce treadmill exercise protocol was used. Mean exercise duration for patients with aortic stenosis, pulmonary stenosis, and ventricular septal defect was 86.5%, 94.2%, and 90.8% of predicted, respectively. For patients with aortic stenosis, there was a direct relation between echocardiographic Doppler maximum transaortic gradient and ST segment change during exercise. ST segment change during exercise was very uncommon for patients with pulmonary stenosis. For patients with ventricular septal defect, there was an association between arrhythmias noted during exercise and the presence of associated aortic insufficiency. CONCLUSIONS: Although exercise duration was well preserved for patients with each of the three defects, exercise tolerance was subnormal.

Adult↗
PubMed1993

Occurrence risk for congenital heart defects in relatives of patients with aortic stenosis, pulmonary stenosis, or ventricular septal defect.

BACKGROUND: Knowledge of the risk of occurrence of congenital heart defects in offspring of individuals with a congenital heart defect is important for genetic counseling and understanding the etiology of congenital heart diseases. METHODS AND RESULTS: A portion of the questionnaire mailed to all patients in the Second Natural History Study of Congenital Heart Defects (NHS-2) addressed marital status, pregnancy, miscarriage, and presence or absence of congenital heart defects or other congenital malformations in first-degree relatives. Offspring were not examined as a part of the study. For male probands with aortic stenosis (AS), three of 251 offspring had congenital heart disease, whereas one of 72 offspring of female probands with AS had congenital heart disease. For patients with pulmonary stenosis (PS), three of 176 offspring of male probands had congenital heart disease, whereas eight of 205 offspring of female probands had congenital heart disease. For male probands with ventricular septal defect (VSD), 10 of 334 offspring had congenital heart defects, and 11 of 384 offspring of female probands with VSD had offspring with congenital heart defects. The prevalence rate for noncardiac congenital anomalies in offspring of probands was 2%. CONCLUSIONS: Based on known congenital heart defects in offspring of probands in the NHS-2, occurrence rates of congenital heart disease in children of subjects with AS, PS, and VSD were 1.2% (confidence interval [CI], 0.34-3.1%), 2.8% (CI, 1.4-5.1%), and 2.9% (CI, 1.8-4.4%), respectively.

Adolescent↗
PubMed1993

Bacterial endocarditis in patients with aortic stenosis, pulmonary stenosis, or ventricular septal defect.

BACKGROUND: All of the 2,401 patients with aortic stenosis (AS), pulmonary stenosis (PS), or ventricular septal defect (VSD) admitted to the First Natural History Study of Congenital Heart Defects between 1958 and 1965 were eligible for the Second Natural History Study. Most patients with severe defects were managed surgically, and most with mild defects were managed medically. Final examination in the first study was carried out 8 years after admission. METHODS AND RESULTS: For AS, the incidence rate of bacterial endocarditis (BE) was 27.1 per 10,000 person-years. The incidence rate was 15.7 per 10,000 person-years for those managed medically and 40.9 per 10,000 person-years for those managed surgically. Most patients managed surgically had severe AS, and severity was more important to the risk of BE than the method of management. For PS, only one of the 592 patients with PS experienced BE. For VSD, the incidence rate of BE was 14.5 per 10,000 person-years. Size of the VSD was not associated with risk of BE. The risk of BE before closure of the VSD was more than twice that after surgery. CONCLUSIONS: The incidence rate of BE was nearly 35-fold the population-based rate. The increased incidence in patients with AS after valvotomy was a function of severity of the defect and not a function of surgery. Presence of aortic regurgitation in patients with AS did not increase the risk of developing BE. Surgical closure of VSD lowered the risk of BE.

Adolescent↗
PubMed1993

Second natural history study of congenital heart defects. Results of treatment of patients with aortic valvar stenosis.

BACKGROUND: From 1958 to 1969, 462 patients (mostly children) with aortic stenosis were admitted to the First Natural History Study of Congenital Heart Defects (NHS-1) after cardiac catheterization. Most with gradients < 50 mm Hg were managed medically; most with gradients > or = 80 mm Hg had aortic valvotomy. Of those with gradients of 50-79 mm Hg, some were managed medically, and some were managed surgically. Most had a second cardiac catheterization at the conclusion of NHS-1. More than 15 years have elapsed since NHS-1, and most of the cohort are adults. This report (the Second Natural History Study [NHS-2]) addresses the long-term results of medical and surgical management. METHODS AND RESULTS: Of the original cohort of 462 patients, 440 were alive at completion of NHS-1. New data were obtained on 371 (80.3%) of the original cohort. Probability of 25-year survival was 92.4% for those admitted with gradients < 50 mm Hg and 81.0% for those with admission gradients > or = 50 mm Hg. More than half of the cardiac deaths were sudden and unexpected. Forty percent of patients managed medically during NHS-1 subsequently required surgical management. Almost 40% of operated patients required a second operation. Three percent of the original cohort subsequently had bacterial endocarditis. There was a higher-than-normal prevalence of serious arrhythmias. Of NHS-2 full participants, 92.3% were in New York Heart Association functional class I. Most patients had low Doppler mean gradients. Clinically, 46.6% had aortic valve regurgitation. The final clinical status was excellent in 29.9%, good in 22.8%, fair in 28.6%, and poor in 18.7%. CONCLUSIONS: Patients with gradients < 25 mm Hg can be followed medically; however, progressive stenosis can occur, and approximately 20% will require intervention. If the gradient is > or = 50 mm Hg, there is a risk of serious arrhythmias and, possibly, sudden death. If the gradient is > or = 80 mm Hg, intervention is clearly indicated; as techniques improve, delaying intervention in patients with gradients of 50-79 mm Hg may not be advantageous. Patients with gradients of 25-49 mm Hg can be followed medically with annual evaluation.

Adult↗
PubMed1993

Second natural history study of congenital heart defects. Results of treatment of patients with pulmonary valvar stenosis.

BACKGROUND: From 1958 to 1969, 592 patients (mostly children) with pulmonary stenosis were admitted to the First Natural History Study of Congenital Heart Defects (NHS-1) after cardiac catheterization. Most with gradients < 50 mm Hg were managed medically; most with gradients > or = 80 mm Hg had pulmonary valvotomy. Among these with gradients of 50-79 mm Hg, some were managed medically, and some were managed surgically. Most had a second cardiac catheterization at conclusion of NHS-1. More than 15 years had elapsed since NHS-1, and most of the cohort are adults. This report (Second Natural History Study) addresses the long-term results of medical and surgical management. METHODS AND RESULTS: Of the original cohort of 592 patients, 580 were alive at completion of NHS-1. New data were obtained on 464 (78.4%) of the original cohort. Probability of 25-year survival was 95.7%. Probability of survival was less (80%) in a subgroup of patients entering NHS-1 > 12 years old with cardiomegaly. Less than 20% of patients managed medically during NHS-1 subsequently required a valvotomy. Only 4% of operated patients required a second operation. Bacterial endocarditis occurred rarely. Ninety-seven percent were in New York Heart Association class I. There was a small but higher-than-normal prevalence of serious arrhythmias. Most patients, whether medically or surgically managed, had low Doppler maximum gradients. Final clinical status was excellent or good in 83%. CONCLUSIONS: Probability of survival is similar to that of the general population, and the vast majority of patients are asymptomatic. If valvotomy or valvuloplasty is required in a child, reoperation is rarely necessary. Patients with gradients < 25 mm Hg do not experience an increase in gradient. Patients with a gradient > or = 50 mm Hg should have valvotomy or valvuloplasty. Choice of management of patients with gradients of 40-49 mm Hg remains debatable.

Adult↗
PubMed1993

Second natural history study of congenital heart defects. Results of treatment of patients with ventricular septal defects.

BACKGROUND: From 1958 to 1969, 1,280 patients (mostly children) with ventricular septal defects (VSDs) were admitted to the First Natural History Study of Congenital Heart Defects (NHS-1) after cardiac catheterization. Most with small defects and Eisenmenger's syndrome were managed medically; most with large VSDs were managed surgically. Of those with moderate-size defects, some were managed medically, and some were managed surgically. Most had a second catheterization at the conclusion of NHS-1. More than 15 years have elapsed since NHS-1, and most of the cohort are adults. This report (Second Natural History Study) addresses the long-term results of medical and surgical management. METHODS AND RESULTS: Of an original cohort of 1,280 patients, 1,099 were alive at completion of NHS-1. New data were obtained on 976 (76.3%) of the original cohort. Probability of 25-year survival was 87%, and admission severity was the best predictor of survival. Of the 860 patients managed medically during NHS-1, 245 subsequently required surgical closure of the VSD. Only 5.5% of patients who had surgical closure required a second operation. On follow-up, there was a higher-than-normal prevalence of serious arrhythmias. Bacterial endocarditis occurred rarely. Of patients with small VSDs, 94.1% were in New York Heart Association functional class I. With the exception of those with Eisenmenger's syndrome, most patients had a final clinical status that was excellent or good. CONCLUSIONS: The majority of patients fared well. However, there was a higher-than-normal prevalence of serious arrhythmia and sudden death, including those with small VSDs.

Adolescent↗
PubMed1993

Second natural history study of congenital heart defects. Quality of life of patients with aortic stenosis, pulmonary stenosis, or ventricular septal defect.

BACKGROUND: Quality of life of patients with congenital heart defects is an important aspect of the assessment of outcome of medical and surgical treatment. METHODS AND RESULTS: All participants in the Second Natural History Study of Congenital Heart Defects who completed the study questionnaire were included in this analysis. The questionnaire completed by the patients included inquiries relative to medical history, marital and family life, self-perception of well-being, insurability, and employability. The following general observations were apparent. The study cohort reported a self-perception of health status that was similar to that of the general population. Second, 35-40% of patients had not had a cardiac evaluation within the previous 10 years. Third, 16% of the patients had no health insurance, and 35.7% of the patients had no life insurance. For the patients with pulmonary stenosis and ventricular septal defect, the percent who were married was less than that of the corresponding national age- and sex-specific population. For patients with aortic stenosis, the percent married was greater than that of the general population for some age groups. The proportion of divorced or separated individuals was similar to that of the general population. For all three defects, the level of educational attainment exceeded the national average. Last, unemployment rates were similar to national averages except for women with aortic stenosis, who had a significantly higher unemployment rate than did age- and sex-matched controls. CONCLUSIONS: Patients initially identified with aortic stenosis, pulmonary stenosis, or ventricular septal defect in 1959-1973 have a quality of life in the mid-1980s similar to that of the general US population.

Adult↗
PubMed1993

Arrhythmias in patients with valvar aortic stenosis, valvar pulmonary stenosis, and ventricular septal defect. Results of 24-hour ECG monitoring.

BACKGROUND: Arrhythmias are a significant source of morbidity and mortality in patients with congenital heart defects. METHODS AND RESULTS: As part of the Second Natural History Study of Congenital Heart Defects (NHS-2), 24-hour ambulatory ECG monitoring was performed for full participants in the study. At least 15.5 hours of monitoring was required for inclusion in the analysis. This was achieved for 755 (90.6%) of the patients. Multiform premature ventricular contractions, ventricular couplets, and ventricular tachycardia were considered "serious arrhythmias." For patients with aortic stenosis, the presence of "serious arrhythmias" was associated with higher left ventricular end-diastolic pressure, presence of aortic regurgitation, male sex, and presence of prior aortic valve replacement. For patients with pulmonary stenosis, only older age on admission to NHS-1 was significantly associated with "serious arrhythmias." For patients with ventricular septal defect, the variables associated with "serious arrhythmias" were different for medically and surgically managed patients. For medically managed patients, higher mean pulmonary artery pressure on admission to NHS-1 and older age on admission to NHS-2 were associated with the presence of serious arrhythmias. For surgically managed patients, higher New York Heart Association functional class and cardiomegaly were associated with serious arrhythmias. CONCLUSIONS: The prevalence of arrhythmias (especially ventricular arrhythmias) was higher for patients with aortic stenosis, pulmonary stenosis, or ventricular septal defect than for an historical control population. "Serious arrhythmias" were most frequently noted in patients with aortic stenosis who also had a higher incidence of sudden death. The prevalence of "serious arrhythmias" was second highest for patients with ventricular septal defect who had the second highest incidence of sudden death.

Adult↗