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Biomedical subjects

B D Duscha

Publications and source records attributed to B D Duscha.

9 recordsLinked to original sources
PubMed2001

Normal skeletal muscle Na(+)-K(+) pump concentration in patients with chronic heart failure.

Intrinsic changes in skeletal muscle are being increasingly suspected as part of the underlying cause of exercise intolerance in patients with chronic heart failure (CHF). The objective of the present study was to determine whether differences existed between CHF patients and age-matched healthy controls in the concentration of skeletal muscle Na(+)-K(+)-ATPase (adenosine triphosphatase), a cation pump that functions to restore Na(+)-K(+) gradients and protect membrane excitability. Moreover, given the potency for physical activity in altering long-term regulation of the pump, an additional objective was to examine the role of activity level in pump expression in CHF patients. Na(+)-K(+)-ATPase concentration (pmol/g wet wt) determined in the vastus lateralis muscle of 27 CHF males (ejection fraction, 23 +/- 1.6%), using the vanadate facilitated [(3)H] ouabain binding technique, was not different (264 +/- 10) from 10 sedentary controls (268 +/- 19,P > 0.05). Similarly, no differences (P > 0.05) could be found between female patients (228 +/- 16, n = 7) and controls (243 +/- 13, n = 9). Differences between untrained control (294 +/- 20, n = 7), chronically active (251 +/- 20, n = 9), and trained (252 +/- 16, n = 6) CHF groups in Na(+)-K(+) pump expression were also insignificant. This study indicates that long-term regulation of Na(+)-K(+)-ATPase concentration is not altered in moderate CHF patients, regardless of the history of regular activity. However, the positive correlations (P < 0.05) that were observed between peak aerobic power (VO(2) peak) and Na(+)-K(+)-ATPase (r = 0.422) and VO(2) peak and maximal citrate synthase activity (r = 0.404) suggests a role for the skeletal muscle in explaining exercise intolerance in CHF patients.

Binding, Competitive↗
PubMed2001

Studies of a targeted risk reduction intervention through defined exercise (STRRIDE).

PURPOSE: The Studies of a Targeted Risk Reduction Intervention through Defined Exercise (STRRIDE) trial is a randomized controlled clinical trial designed to study the effects of exercise training regimens differing in dose (kcal.wk-1) and/or intensity (relative to peak VO2) on established cardiovascular risk factors and to investigate the peripheral biologic mechanisms through which chronic physical activity alters carbohydrate and lipid metabolism to result in improvements in these parameters of cardiovascular risk in humans. METHODS: We will recruit 384 subjects and randomly assign them to one of three exercise training regimens or to a sedentary control group. The recruiting goal is to attain a subject population that is 50% female and 30% ethnic minority. The overall strategy is to use graded exercise training regimens in moderately overweight subjects with impairments in insulin action and mild to moderate lipid abnormalities to investigate whether there are dose or intensity effects and whether adaptations in skeletal muscle (fiber type, metabolic capacity, and/or capillary surface area) account for improvements in insulin action and parameters of lipoprotein metabolism. We will study these variables before and after exercise training, and over the course of a 2-wk detraining period. The study sample size is chosen to power the study to examine differences in responses between subjects of different gender and ethnicity to exercise training with respect to the least sensitive parameter-skeletal muscle capillary density. RESULTS: The driving hypothesis is that improvements in cardiovascular risk parameters derived from habitual exercise are primarily mediated through adaptations occurring in skeletal muscle. CONCLUSION: Identification that amount and intensity of exercise matter for achieving general and specific health benefits and a better understanding of the peripheral mechanisms mediating the responses in carbohydrate and lipid metabolism to chronic physical activity will lead to better informed recommendations for those undertaking an exercise program to improve cardiovascular risk.

Adult↗
PubMed2001

Differences in skeletal muscle between men and women with chronic heart failure.

Men with chronic heart failure (CHF) have alterations in their skeletal muscle that are partially responsible for a decreased exercise tolerance. The purpose of this study was to investigate whether skeletal muscle alterations in women with CHF are similar to those observed in men and if these alterations are related to exercise intolerance. Twenty-five men and thirteen women with CHF performed a maximal exercise test for evaluation of peak oxygen consumption (VO(2)) and resting left ventricular ejection fraction, after which a biopsy of the vastus lateralis was performed. Twenty-one normal subjects (11 women, 10 men) were also studied. The relationship between muscle markers and peak VO(2) was consistent for CHF men and women. When controlling for gender, analysis showed that oxidative enzymes and capillary density are the best predictors of peak VO(2.) These results indicate that aerobically matched CHF men and women have no differences in skeletal muscle biochemistry and histology. However, when CHF groups were separated by peak exercise capacity of 4.5 metabolic equivalents (METs), CHF men with peak VO(2) >4.5 METs had increased citrate synthase and 3-hydroxyacyl-CoA dehydrogenase compared with CHF men with peak VO(2) <4.5 METs. CHF men with a lower peak VO(2) had increased capillary density compared with men with higher peak VO(2). These observations were not reproduced in CHF women. This suggests that differences may exist in how skeletal muscle adapts to decreasing peak VO(2) in patients with CHF.

Capillaries↗
PubMed1999

Capillary density of skeletal muscle: a contributing mechanism for exercise intolerance in class II-III chronic heart failure independent of other peripheral alterations.

OBJECTIVES: The study was conducted to determine if the capillary density of skeletal muscle is a potential contributor to exercise intolerance in class II-III chronic heart failure (CHF). BACKGROUND: Previous studies suggest that abnormalities in skeletal muscle histology, contractile protein content and enzymology contribute to exercise intolerance in CHF. METHODS: The present study examined skeletal muscle biopsies from 22 male patients with CHF compared with 10 age-matched normal male control patients. Aerobic capacities, myosin heavy chain (MHC) isoforms, enzymes, and capillary density were measured. RESULTS: The patients with CHF demonstrated a reduced peak oxygen consumption when compared to controls (15.0+/-2.5 vs. 19.8+/-5.0 ml x kg(-1) x min(-1), p <0.05). Using cell-specific antibodies to directly assess vascular density, there was a reduction in capillary density in CHF measured as the number of endothelial cells/fiber (1.42+/-0.28 vs. 1.74+/-0.35, p = 0.02). In CHF, capillary density was inversely related to maximal oxygen consumption (r = 0.479, p = 0.02). The MHC IIx isoform was found to be higher in patients with CHF versus normal subjects (28.5+/-13.6 vs. 19.5+/-9.4, p <0.05). CONCLUSIONS: There was a significant reduction in microvascular density in patients with CHF compared with the control group, without major differences in other usual histologic and biochemical aerobic markers. The inverse relationship with peak oxygen consumption seen in the CHF group suggests that a reduction in microvascular density of skeletal muscle may precede other skeletal muscle alterations and play a critical role in the exercise intolerance characteristic of patients with CHF.

Biopsy↗
PubMed1999

Altered expression of myosin heavy chain in the vastus lateralis muscle in patients with COPD.

This study was designed to further characterize peripheral skeletal muscle alterations in patients with chronic obstructive pulmonary disease (COPD) and to evaluate the possible relationship between myosin heavy chain (MyoHC) isoform expression and exercise tolerance in these individuals. MyoHC composition from biopsy of the vastus lateralis muscle was examined in 12 COPD patients (forced expiratory volume in one second (FEV1)=31+/-9% predicted, peak oxygen consumption (V'O2)=15+/-4 mL x kg(-1) x min(-1)) and 10 age-matched normal male subjects (peak V'O2=20+/-5 mL x kg(-1) x min(-1)). The proportion of MyoHC type I was smaller in COPD than in normals (27+/-17% versus 41+/-9%, p<0.05) with an increase in MyoHC type IIa (51+/-15% versus 39+/-9%, p<0.05) and the proportion of MyoHC type IIx being comparable between both groups. A significant relationship was found between peak V'Oo2 mL x kg(-1) x min(-1) and FEV1 % pred (r=0.91, p<0.0001) and the percentage of MyoHC type I (r=0.61, p=0.016). In stepwise multiple regression, only FEV1 % pred was found to be a significant determinant of peak V'O2 (p<0.0001). This variable explained 83% of the total variance of peak V'O2. In summary, this study showed considerable modifications in the phenotypic expression of the myosin heavy chain in the vastus lateralis muscle in patients with chronic obstructive pulmonary disease. An independent effect of myosin heavy chain expression on exercise capacity was not found. These results suggest that chronic inactivity and muscle deconditioning may not be the sole factors explaining peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease.

Aged↗
PubMed1997

Altered expression of myosin heavy chain in human skeletal muscle in chronic heart failure.

To explore further alterations in skeletal muscle in chronic heart failure (CHF), we examined myosin heavy chain (MHC) isoforms from biopsies of the vastus lateralis in nine male patients with class II-III (CHF) (left ventricular ejection fraction (LVEF) 26 +/- 11%, peak oxygen consumption (peak VO2) 12.6 +/- 2 mL.kg-1.min-1) and nine age-matched sedentary normal males (NL). The relative content of MHC isoforms I, IIa, and IIx was determined by gel electrophoresis as follows: The normal sedentary group (NL) had a higher percent of MHC type I when compared with the patients (NL 48.4 +/- 7% vs CHF patients 24 +/- 21.6%, P < 0.05, no difference between MCH IIa (NL 45.1 +/- 10.5% vs CHF 56.0 +/- 12.5%), and CHF patients had a higher relative content of MHC type IIx than did the normal group (NL 6.5 +/- 9.6% vs CHF 20.0 +/- 12.9%, P < 0.05. Three of nine patients had no detectable MHC type I. In patients relative expression of MHC type I (%) was related to peak VO2 (r = 0.70, P < 0.05). Our results indicate that major alterations in MHC isoform expression are present in skeletal muscle in CHF. These alterations parallel previously reported changes in fiber typing that may affect contractile function i skeletal muscle and possibly exercise performance. The absence of MHC type I in some CHF patients suggests that skeletal muscle changes in this disorder are not solely a result of deconditioning, buy may reflect a specific skeletal muscle myopathy in this disorder.

Adult↗
PubMed1995

A carbohydrate loading regimen improves high intensity, short duration exercise performance.

This investigation examined the effect of a carbohydrate loading regimen on high intensity, short duration run performance. Using a random crossover design, 8 trained runners completed a 15-min submaximal run and a performance run to exhaustion after two dietary treatments. The mixed diet (MD) contained 4.0 +/- 0.5 g.kg-1.d-1 of carbohydrate (CHO) for 6 days. The experimental diet (HCD) contained 4.5 +/- 0.5 g CHO.kg-1.d-1 for 3 days followed by 8.2 +/- 0.4 g CHO kg-1.d-1 for 3 days. Training consisted of daily runs of 90, 40, 40, 20, and 20 min at approximately 75% of VO2max. Day 6 was a rest day, and testing was completed on Day 7. Preexercise lactate, body weight, submaximal VO2, and heart rate did not differ significantly between treatments. Carbohydrate oxidation during submaximal running was higher (p < 0.05) after HCD than after MD. Time to exhaustion in the performance run was longer after HCD compared to MD. Results indicate that a carbohydrate loading regimen increases CHO oxidation during submaximal exercise and improves high intensity, short duration run performance.

Adult↗
PubMed1994

Skeletal muscle pH assessed by biochemical and 31P-MRS methods during exercise and recovery in men.

The present study was designed to compare evaluation of skeletal muscle metabolism (vastus lateralis) evaluated by 31P-magnetic resonance spectroscopy (MRS) and biochemical analysis. During identical isometric knee extensor exercise protocols to fatigue in eight men, biopsy samples were taken at rest, peak exercise, and 32 s postexercise and 31P-MRS data were collected continuously for phosphocreatine (PCr), pH, ATP, and P(i) at 8- or 32-s intervals. There was no difference in ATP or pH measurements between the two techniques at rest, during peak exercise, or in recovery. Corresponding measurements of pH by the two techniques were closely related (r = 0.88, P < 0.01), and pH measured by 31P-MRS was closely related to muscle lactate accumulation (r = -0.84, P < 0.001). The level of PCr at peak exercise, expressed as a percentage of the baseline value, was not different between the two techniques (42 +/- 15 vs. 46 +/- 15%). The results indicate that, in skeletal muscle in normal subjects, 1) measurements of pH and PCr at rest and during exercise do not differ between the 31P-MRS and biopsy techniques and 2) muscle pH measured by 31P-MRS is closely related to lactate accumulation in men. Our data suggest that direct comparison of results of studies of exercise metabolism using these two techniques is warranted.

Adenine Nucleotides↗