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Biomedical subjects

J L Durstine

Publications and source records attributed to J L Durstine.

36 records · Page 2Linked to original sources
PubMed1996

Factors affecting fibrinolytic potential: cardiovascular fitness, body composition, and lipoprotein(a).

The purpose of the study was to determine the factors that affect basal (resting) and poststressor fibrinolytic activity or potential. Variables of interest included cardiovascular fitness (maximal oxygen consumption [Vo2max]), body fat, body mass index (BMI), and lipids/lipoproteins, including lipoprotein(a) [Lp(a)]. Blood was collected from 46 middle-aged men before and after a maximal exercise test. Pearson and Spearman correlation coefficients were calculated to determine associations between the variables of interest and tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) activities in the basal state and after stimulation with maximal exercise. Multiple regression analyses were also conducted to determine independent predictors of the fibrinolytic variables. Maximal exercise produced significant increases in t-PA activity and decreases in PAI-1 activity. Postexercise t-PA activity was inversely related to basal PAI-1 activity (r = -.34). Vo2max was positively correlated with t-PA activity (basal, r = .39; postexercise, r = .67) and inversely related to PAI-1 activity (basal, r = -.41; postexercise, r = -.42). Body fat was correlated with postexercise t-PA activity (r = -.60) and both basal and postexercise PAI-1 activity (r = .42), but the correlation with basal t-PA activity was not significant (P = .058). Postexercise t-PA activity was positively correlated (r = .37) with high-density lipoprotein cholesterol (HDL-C) and negatively correlated (r = -.42) with low-density lipoprotein cholesterol (LDL-C). Basal PAI-1 activity was negatively correlated with HDL-C (r = -.37), Lp(a) was not correlated with any fibrinolytic variable or fitness. Multiple regression analyses showed that Vo2max was an independent predictor of both basal and postexercise t-PA activity (R2 = .16 and .34, respectively). Triglyceride (TG) levels and Vo2max were significant independent predictors of PAI-1 activity (R2 = .31). In conclusion, cardiovascular fitness was a strong independent predictor of fibrinolytic potential. In addition, poststressor measures of fibrinolytic potential may provide more information about the fibrinolytic system than basal values.

Adult↗
PubMed1996

Effect of a single session of exercise on lipoprotein(a).

Lipoprotein(a) (Lp(a)) is bound to apolipoprotein B-100 by disulfide linkage and is associated in the upper density range of low density lipoprotein cholesterol. Persons with elevated concentrations of Lp(a) are regarded as having an increased risk for premature coronary artery disease. Although many studies exist evaluating the effects of a single session of exercise on lipids and lipoproteins, little information is available concerning the effects of exercise on Lp(a). Therefore, the purpose of this study was to determine the effects of a single exercise session on plasma Lp(a). Twelve physically active men completed two 30-min submaximal treadmill exercise sessions: low intensity (LI, 50% VO2max) and high intensity (HI, 80% VO2max). Blood samples were obtained immediately before and after exercise. Total cholesterol (LI: before 4.22 +/- 0.26, after 4.24 +/- 0.28; HI: before 4.24 +/- 0.31, after 4.11 +/- 0.28 mmol.l-1, mean +/- SE) and triglyceride (LI: before 1.14 +/- 0.16, after 1.06 +/- 0.16; HI: before 1.12 +/- 0.19, after 1.21 +/- 0.19 mmol.l-1) concentrations did not differ immediately after either exercise session, nor did Lp(a) concentrations differ immediately after either exercise session (LI: before 4.1 +/- 2.2, after 4.0 +/- 2.1: HI: before 3.9 +/- 2.2, after 3.7 +/- 2.0 mg.dl-1). These results suggest that neither a low nor a high intensity exercise session lasting 30 min in duration has an immediate effect on plasma Lp(a).

Adult↗
PubMed1994

Effects of maximal exercise and venous occlusion on fibrinolytic activity in physically active and inactive men.

The purposes of this study were to 1) characterize changes in fibrinolytic activity in response to maximal exercise and 5-min venous occlusion and 2) compare responses in men of various habitual physical activity levels. Tissue plasminogen activator (TPA) activity and plasminogen activator inhibitor 1 (PAI-1) activity were measured in 15 inactive, 15 regularly active, and 15 highly active men. Data were analyzed using a three-way analysis of variance with repeated measures. Pretest TPA activity was similar among groups. TPA activity increased postexercise with higher values seen in the active groups (P < 0.001). The highly active group also significantly increased TPA activity postvenous occlusion (P < 0.01). Pretest PAI-1 activity was different among groups, with the inactive group showing the highest activity and the highly active group the lowest (P < 0.05). PAI-1 activity decreased with exercise (P < 0.01) but did not change with venous occlusion. In conclusion, active men exhibited greater changes in fibrinolytic activity with maximal exercise and venous occlusion than inactive men. This enhanced fibrinolytic activity may be an important mechanism mediating the cardioprotective effect provided by regular physical activity.

Adult↗
PubMed1992

Altered cellular distribution of hexokinase in skeletal muscle after exercise.

The purpose of this study was to determine the effects of a single period of swim exercise to exhaustion on the cellular distribution of hexokinase in rat skeletal muscle. The gastrocnemius muscle from male rats exercised (n = 16) to exhaustion or allowed to remain inactive (n = 14) was analyzed for hexokinase activity (HK) in the whole muscle homogenate and the mitochondrial-rich fraction. Although exercise produced a slight, non-significant, increase in HK activity in the whole muscle homogenate (p less than 0.09), HK activity in the mitochondrial-rich fraction was significantly increased in the exercised muscle (p less than 0.02). This shift in the cellular distribution of HK is towards the more active mitochondrial bound form and indicates an enhanced regulation of HK activity during physical exercise.

Animals↗
PubMed1992

Effects of acute exercise intensity on plasma lipids and apolipoproteins in trained runners.

The purpose of this study was to determine the effects of exercise intensity on lipid and lipoprotein metabolism. Concentrations of triglyceride, cholesterol, high-density lipoprotein cholesterol (HDL-C) and its subfractions (HDL2-C and HDL3-C), low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, and apolipoproteins A-I, A-II, and B were measured. Ten well-trained runners completed treadmill exercise on two different occasions: a high-intensity session at 75% maximal oxygen consumption lasting 60 min and a low-intensity session at 50% maximal oxygen consumption lasting 90 min. Energy expenditure for each session was equal. Fasted blood samples were obtained 24 h before, immediately before, immediately after, and 1, 24, 48, and 72 h after each exercise session. No significant differences were found for the blood variables across time or between treatments. However, HDL-C and HDL2-C were slightly elevated on the days after each treatment. These results suggest that acute exercise sessions lasting less than 90 min, regardless of intensity, do not elicit plasma lipid, lipoprotein, and apolipoprotein changes in men who are habitually physically active and have high initial concentrations of HDL-C.

Adult↗
PubMed1992

Psychological and behavioral differences among females classified as bulimic, obligatory exerciser and normal control.

The compulsion to maintain a lean body shape while living in a society obsessed with food may encourage the use of dieting, binge eating and purging behaviors in young women. The body of literature on bulimia nervosa (Boskind-Lodahl and Sirlin 1977; Fairburn and Cooper 1984; Katzman and Wolchik 1984; Scott 1988) clearly establishes its relationship to the current American fashion for thinness and the value placed on physical attractiveness for self-esteem. This notion promotes a multitude of weight control strategies ranging from self-starvation (Humphrey 1983; Brownell and Foreyth 1986) to cigarette smoking (Klesges and Klesges 1988), many of which may have a profound influence on maintenance of good health. Similar to weight control, exercise behavior could be viewed as falling on a continuum from reasonable efforts to maintain physical fitness to a preoccupation with exercise that is far out of proportion to the expected benefits of a 30-minute, three to five day a week routine. Characteristics of obligatory exercise have been described by several researchers and include maintaining a rigid schedule of intense exercise; resisting temptation to lapse into nonexercising; feelings of guilt and anxiety when the exercise schedule is violated; compensatory increase in exercise to make up for lapses; pushing oneself even when tired, ill, or injured; mental preoccupation with exercise; and detailed recordkeeping on exercise (Yates et al. 1983; Blumenthal et al. 1984; Nudelman et al. 1988). In a competitive society, obsessive exercise behaviors may be linked to the development of rigid dietary guidelines while one strives toward the "optimal" lean-fat ratio of body composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Immediate and delayed effects of marathon running on lipids and lipoproteins in women.

The purpose of this investigation was to examine the immediate and delayed effects of prolonged strenuous exercise on plasma lipid and lipoprotein concentrations in female runners. Venous blood samples were collected from 12 female runners 24 h before, 10 min after, and 1, 3, and 5 d after running a 42 km marathon. Whole blood was analyzed for hematocrit and hemoglobin to determine plasma volume shifts. Plasma aliquots were assayed for total cholesterol, high-density lipoprotein cholesterol (HDL-C), and triglyceride concentrations, while low-density lipoprotein cholesterol (LDL-C) was estimated. Total cholesterol concentrations were significantly reduced 1 d following the exercise and were still lower 3 and 5 d post-marathon. LDL-C was lower immediately and 1 d after the marathon. HDL-C concentrations, corrected for changes in plasma volume, were elevated 24 h post-exercise. The ratio of HDL/total cholesterol was increased 24 h post-exercise. Triglyceride concentrations were elevated immediately following the marathon but returned to baseline levels by 24 h post-exercise. These results demonstrate that prolonged strenuous exercise in women produces changes in blood lipid profiles that can last for several days.

Adult↗
PubMed1986

Distribution of cyclic AMP phosphodiesterase in adipose tissue from trained rats.

Fat cells were isolated from sedentary and exercise trained female Sprague-Dawley rats and cyclic AMP phosphodiesterase (cyclic AMP-PDE) activities were determined from crude homogenates of the fat cells in the whole homogenate, P5, P48, and S48 fractions. Exercise training resulted in a significant increase in the mean specific activity of cyclic AMP-PDE (pmol X min-1 X mg-1) from the whole homogenate and S48 fraction at cyclic AMP concentrations of 4, 8, and 16 microM and in the P48 fraction at 8 and 16 microM cyclic AMP. Cyclic AMP-PDE kinetic plots according to Lineweaver-Burk for the calculation of Michaelis constants (Km) and maximum enzyme velocities (Vmax) were nonlinear, indicating both a low and high enzyme form. The Michaelis constants were significantly lower in trained rats than those of its control for the high Km form of cyclic AMP-PDE in the whole and soluble fractions and for the low Km form of the P5 particulate fraction. The Vmax of the high Km form of the P48 particulate fraction from trained animals was also significantly higher than that found in its control. Phosphodiesterase inhibition by methylxanthines in the various fractions was similar in both trained and sedentary animals. These changes in specific activity, Michaelis constants, and Vmax of cyclic AMP-PDE from crude homogenates of isolated fat cells from exercise trained animals may account for the decreased intracellular levels of cyclic AMP following catecholamine stimulation of isolated fat cells from trained rats.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

Lipoprotein and apolipoprotein distribution in Zucker rats following an endurance running program.

We examined the response to 12 weeks of endurance running of the obese Zucker rat and its lean littermate with regard to changes in serum lipids, lipoproteins and apoproteins. The obese Zucker rat is hyperlipoproteinemic, characterized by elevated serum triglyceride and cholesterol levels primarily associated with the very low density lipoprotein (VLDL) fraction. In lean Zucker rats, training did not affect the concentrations of serum lipids or apolipoproteins. In marked contrast, obese Zucker rats that were trained had significant decreases in serum concentrations of triglycerides, free and esterified cholesterol, and apolipoprotein B compared to their sedentary counterparts. Training obese rats caused an increase in the serum concentration of apolipoprotein E (HDL fraction). In contrast, training did not affect the concentration of Apo E in lean rats. The VLDL fraction was most affected by training obese rats showing marked 50-65% decreases in VLDL triglyceride and VLDL cholesterol. HDL cholesterol was unchanged in lean rats whereas training prompted a 29% increase in obese rats. These data show that exercise training altered the metabolic abnormalities of obese Zucker rats which are responsible for the accumulation in serum of VLDL, lipids and apolipoproteins.

Animals↗
PubMed1985

Serum lipoproteins of the Zucker rat in response to an endurance running program.

Previous studies have concluded that exercise training has resulted in increases in cholesterol associated with high-density lipoprotein (HDL). However, data regarding alterations in triglyceride, cholesterol, and the protein associated with the three major lipoproteins in a hyperlipoproteinemic state in response to exercise training are not available. Serum lipoprotein levels from normal and hyperlipoproteinemic Zucker rats were studied following 9 and 18 wk of treadmill running to determine the extent that the three major serum lipoprotein classes were affected. Nine weeks of treadmill running reduced serum triglyceride content in obese rats (sedentary, 294 +/- 19 [SE]; trained, 128 +/- 40 mg X dl-1) but did not affect total serum cholesterol (sedentary, 85 +/- 6; trained, 90 +/- 6 mg X dl-1). Serum very low-density lipoprotein from the trained obese rats contained lower levels of triglyceride (57%), cholesterol (46%), and protein (61%). HDL cholesterol (sedentary, 61 +/- 4; trained, 73 +/- 4 mg X dl-1) was increased by 14% in the obese rat. In the lean rat, HDL cholesterol was the only lipoprotein fraction altered following 9 wk of treadmill running. The data from this study indicate that hypertriglyceridemia can be reduced in the obese rat and that HDL cholesterol can be increased by physical activity requiring about 70% maximal aerobic capacity.

Animals↗
PubMed1983

Increases in HDL-cholesterol and the HDL/LDL cholesterol ratio during prolonged endurance exercise.

The influence of prolonged, low-intensity exercise (45% VO2max) until exhaustion on plasma lipid levels, in particular high-density lipoprotein cholesterol (HDL-C), and the time sequence associated with changes in these blood constituents was investigated in 10 trained subjects. The exercise consisted of walking on a motor-driven treadmill until exhaustion. Blood samples were drawn before, at 30 and 60 minutes after the beginning of exercise, at each hour thereafter until exhaustion, immediately before exhaustion, and after a 30-minute recovery period. At exhaustion the total cholesterol concentration was significantly elevated by 3% and rose another 3% during the recovery period. The HDL-C level was significantly elevated within two hours after the start of exercise and by exhaustion (about 4.5 hours of exercise) had risen to 52.5 +/- 2.3 mg X dL-1, which represented a 10.8% increase above the pre-exercise concentration (47.4 +/- 1.8 mg X dL-1). The HDL/LDL cholesterol ratio followed a pattern similar to that described for HDL-C. Plasma free fatty acids (FFA) also increased linearly during the exercise period but were not significantly correlated with HDL-C during exercise (r = 0.14). These results suggest that prolonged, low-intensity exercise can acutely improve the lipid profile of humans.

Adult↗
PubMed1982

Attenuation of blood pressure increases in Dahl salt-sensitive rats by exercise.

Systolic blood pressure was determined weekly to assess the development of hypertension in sedentary and active Dahl salt-sensitive (S) rats that were exercised by running at 20 m/min, 60 min/day, 5 days/wk. The marked rise in blood pressure that occurred with feeding 8% NaCl (wt/wt) diet in Dahl S rats could be attenuated by chronically practiced endurance running, but only if exercise at 20 m/min was started at the beginning of salt feeding. Under the same dietary feeding conditions, running at 27 m/min resulted in incomplete attenuation of hypertension. Further, running for 30 min/day was not as beneficial as running 60 min/day at 20 m/min. Delaying the start of exercise for 6 wk after the beginning of salt feeding did not result in reduction of hypertension in the S rat. These experiments indicate that increases in blood pressure can be prevented in Dahl S rats for 12 wk if running is initiated concomitantly with salt feeding. Blood pressure is not reduced if hypertension due to salt feeding has been continued for 6 wk. The results also indicate that there is an optimal exercise intensity, duration, or both, for controlling hypertension in Dahl rats.

Animals↗
PubMed1979

Physiologic effects on adult men of circuit strength training and jogging.

The purpose of this study was to determine the effects of 8 weeks of circuit strength training (CST) followed by 8 weeks of jogging and then 8 weeks, of CST or jogging. During the final 8 weeks, the subjects were randomly assigned to either CST or jogging groups. The subjects (n=16, x age = 29 yrs) exercised 3 days/week. The strength training involved 2 circuits of reciprocal exercises using isokinetic devices with 10 to 15 repetitions/set and 30 seconds of rest between sets. The subjects jogged 3 miles/day during the jogging program. After the initial 8 weeks of CST, significant changes were found in treadmill performance time, maximum oxygen uptake (VO2max), maximum pulmonary ventilation (VEmax), body fat, total skinfold fat, fat weight, lean weight, isotonic bench and leg press, and isokinetic slow speed, fast speed, and power endurance measures. The jogging program elicited significantly greater changes in treadmill performance time and VO2max. Further reductions were found in total skinfolds and waist girth during the jogging program. Leg strength was maintained during jogging but upper body strength was reduced significantly. Physiologic levels were maintained during the final 8 weeks and showed no differences between the CST and jogging groups.

Adult↗
PubMedDate not supplied

National Survey on Gender Differences in Cardiac Rehabilitation Programs. Patient characteristics and enrollment patterns.

PURPOSE: Cardiac rehabilitation (CR) programs have been shown to promote numerous health benefits among patients with active coronary heart disease (CHD), but little is known about the percentage of eligible CHD patients who enroll in CR. METHODS: A survey was performed of 500 randomly chosen CR programs in operation in the United States during 1990. Patient characteristics and enrollment data were combined with data from the 1990 National Hospital Discharge Survey to estimate the percentage of eligible patients who participated in early outpatient (Phase II) CR programs after myocardial infarction (MI), after coronary angioplasty (PTCA), or after coronary artery bypass surgery (CABS). RESULTS: Completed surveys were returned by 163 programs (32.6%) with information on 1,322 women and 1,418 men who enrolled in their programs in 1990. Women were older, more likely to be single, and had more traditional CHD risk factors than men. Only a minority of MI, PTCA, and CABS survivors enrolled in CR programs (10.8%, 10.3% and 23.4%, respectively). Enrollment was particularly low for post-MI and post-CABS women as compared with men: 6.9% versus 13.3% (P < .001), and 20.2% versus 24.6% (P < .001), respectively. Enrollment was generally lowest for nonwhites, those over age 65, and those living in the southern United States. CONCLUSIONS: Cardiac rehabilitation programs are used by a minority of eligible patients, particularly among women, nonwhites, and the elderly. To meet newly released national guidelines that recommend CR services for most patients recovering from MI, PTCA, or CABS, and to still contain costs, new methods need to be explored that can expand the delivery of CR services in clinical settings.

Aged↗
PubMedDate not supplied

Physical activity, physical fitness, and Framingham 10-year risk score: the cross-cultural activity participation study.

PURPOSE: Although physical activity and physical fitness are inversely and causally associated with coronary heart disease (CHD) morbidity and mortality, available equations for estimating CHD risk do not include scores for activity or fitness. Therefore, this study evaluated the association of physical fitness and moderate-intensity physical activity with the 10-year Framingham CHD risk estimate. METHODS: Cross-sectional analyses were performed on data from 137 healthy middle-aged women (53.9 +/- 9.9 yr; 28.3 +/- 6.0 kg/m2). Health histories, body composition, blood pressure, and blood samples were obtained from a clinical examination. Levels of moderate (3-6 METS) intensity physical activity, expressed as MET-minutes/day of energy expenditure, were derived from multiple 24-hour physical activity records. Physical fitness was quantified as duration of a symptom-limited maximal treadmill exercise test. RESULTS: After adjustment for race, body mass index (BMI), and hormone replacement status, a graded reduction in the Framingham risk score was observed across low (5.8%), moderate (4.0%), and high (3.6%) fitness levels (P for trend = 0.009). Women in both the moderate and high fitness categories had a lower (P < 0.01) risk score compared with their low fit counterparts. Significant differences in risk were not seen among low (3.9%), moderate (4.9%), and high (4.4%) physical activity groups. The lack of association between the risk score by physical activity may have been due to the homogeneity of activity levels among participants. Our findings reinforce existing data that show enhanced levels of fitness are associated with lower risk for CHD.

Coronary Disease↗