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Biomedical subjects

J Keul

Publications and source records attributed to J Keul.

At least 19 recordsLinked to original sources
PubMed1992

Distribution of lipoprotein species (LpA-I, LpA-I:A-II) in serum and HDL subfractions of untrained and trained normolipemic men.

The distribution of lipoprotein species (LpA-I, LpA-I:A-II) in serum and within HDL subfractions (HDL2b, HDL2a, HDL3) was examined in 26 sedentary and 19 endurance trained normolipemic male individuals. The concentrations of lipids and apolipoproteins in serum and HDL subfractions and the concentrations of LpA-I and LpA-I:A-II were determined. Significant differences (Mann-Whitney-U-test) were found in serum concentrations of apoB (P < 0.05), apoA-II (P < 0.01) and LpA-I:A-II (P < 0.001). In HDL3 apoA-II concentration was significantly lower in the trained group (P < 0.05) but in HDL2 subclasses the concentrations of apoA-I and apoA-II did not differ between the groups. Despite similar concentrations of the two apolipoproteins, there were difference in the distribution of lipoprotein species within HDL2 subfractions. The concentrations of LpA-I did not differ, but the concentrations of LpA-I:A-II particles were higher in the trained group. Untrained and trained had similar concentrations of apoA-II (in HDL2b) but obviously more apoA-II containing particles and this leads to the assumption that within HDL2 of endurance trained individuals LpA-I:A-II particles have a lower apoA-II content compared with particles of untrained individuals. The data emphasize, that normolipemic individuals of different maximum oxygen uptake have a different distribution and composition of lipoprotein species (LpA-I, LpA-I:A-II).

Adult↗
PubMed1992

Training-overtraining: influence of a defined increase in training volume vs training intensity on performance, catecholamines and some metabolic parameters in experienced middle- and long-distance runners.

The influence of an increase in training volume (ITV; February 1989) vs intensity (ITI; February 1990) on performance, catecholamines, energy metabolism and serum lipids was examined in two studies on eight, and nine experienced middle- or long-distance runners; seven participated in both studies. During ITV, mean training volume was doubled from 85.9 km.week-1 (pretrial phase) to 174.6 km within 3 weeks. Some 96%-98% of the training was performed at 67 (SD 8)% of maximal performance. During ITI, speed-endurance, high-speed and interval runs increased within 3 weeks from 9 km.week-1 (pretrial phase) to 22.7 km.week-1 and the total training distance from 61.6 to 84.7 km.week-1. The ITV resulted in stagnation of running velocity at 4 mmol lactate concentration and a decrease in total running distance in the increment test. Heart rate, energy metabolic parameters, nocturnal urinary catecholamine excretion, low density, very low density lipoprotein-cholesterol and triglyceride concentrations decreased significantly; the exercise-related catecholamine plasma concentrations increased at an identical exercise intensity. The ITI produced an improvement in running velocity at 4 mmol lactate concentration and in total running distance in the increment test; heart rate, energy metabolic parameters, nocturnal catecholamine excretion, and serum lipids remained nearly constant, and the exercise-related plasma catecholamine concentrations decreased at an identical exercise intensity. The ITV-related changes in metabolism and catecholamines may have indicated an exhaustion syndrome in the majority of the athletes examined but this hypothesis has to be proven by future experimental studies.

Adult↗
PubMed1992

Probucol, incorporated into LDL particles in vivo, inhibits generation of lipid peroxides more effectively than endogenous antioxidants alone.

One of the first steps in lipid autoxidation leads to the generation of lipid peroxides (LPO). The time course of LPO generation during Cu++ catalyzed oxidation of LDL before and after treatment with probucol was determined in this study. Before analysis the samples had been stored for about 3 years at -20 degrees C. The results show that in LDL samples without probucol the total antioxidative potential had been depleted during the long-term storage. In contrast, LDL containing probucol showed almost no signs of lipid autoxidation. In addition, the ratio of vitamin E to cholesterol was significantly higher in serum samples containing probucol. We conclude that, in vivo, probucol is incorporated into LDL particles in concentrations high enough to inhibit even early steps of lipid autoxidation.

Antioxidants↗
PubMed1992

Training-overtraining: performance, and hormone levels, after a defined increase in training volume versus intensity in experienced middle- and long-distance runners.

Performance and hormones were determined in eight middle- and nine long-distance runners after an increase in training volume (ITV, February 1989) or intensity (ITI, February 1990). Seven runners participated in both studies. The objective was to cause an overtraining syndrome. The mean training volume of 85.9 km week-1 increased within 3 weeks to 176.6 km week-1 during ITV and 96-98% of training volume was performed as long-distance runs at mean(s.d.) 67(8)% of maximum capacity. Speed endurance, high-speed and interval runs averaging 9 km week-1 increased within 3 weeks to 22.7 km during ITI, and the total volume increased from 61.6 to 84.7 km. A plateau in endurance performance and decrease in maximum performance occurred during ITV, probably due to overtraining, with performance incompetence over months. Nocturnal catecholamine excretion decreased markedly (47-53%), contrary to exercise-related plasma catecholamine responses, which increased. Resting and exercise-related cortisol and aldosterone levels decreased. Improvement in endurance and maximum performance occurred during ITI indicating a failure to cause an overtraining syndrome in ITI. Decrease in noctural catecholamine excretion was clearly lower (9-26%), exercise-related catecholamine responses showed a significant decrease, cortisol and aldosterone levels remained almost constant, exercise-related prolactin levels decreased slightly. There were no differences in insulin, C-peptide, free testosterone, somatotropic hormone (STH), follicle stimulating hormone (FSH), luteinizing hormone (LH), thyroid stimulating hormone (TSH), tri-iodothyronine (T3) and thyroxine (T4). The decrease in nocturnal catecholamine excretion during ITV might indicate a decrease in intrinsic sympathetic activity in exhausted sportsmen. But it remains open whether this reflected a central nervous system incompetence.

Adult↗
PubMed1991

[Metabolic and cardiovascular adaptation and the performance of professional tennis players].

14 professional tennis players of world rank were examined (7 men, mean age 23 +/- 3 years; 7 women, mean age 18 +/- 2 years). Heart volume (HV) was 11.9 +/- 0.9 ml/kg in women, 12.7 +/- 1.3 ml/kg in men, 20-30% higher than in untrained persons. Correspondingly, end-diastolic (EDV) and end-systolic volume, left-ventricular muscle mass (LVM) and stroke volume (SV) were elevated, while contractility parameters as well as the ratios of SV and of LVM to EDV and HV were within normal limits. The changes are to be taken as adaptations in the sense of athlete's heart. Maximal treadmill speed was 18 km/h in women and 19.3 km/h in men, with maximal lactate levels of 9.3 mmol/l (women) and 11.4 mmol/l (men). Anaerobic threshold was reached at a treadmill speed of 13.3 km/h (women) and 14.8 km/h (men). These data indicate a good performance range and were clearly better than in earlier groups of tennis players. This adaptation requires additional interval and endurance training. In 11 tennis players the serum concentration of magnesium and in 5 that of iron was below the recommended lower limit (magnesium: 0.8 mmol/l; iron: 14 mumols/l). Serum concentrations of creatine kinase and of lactate dehydrogenase were always two to three times higher than normal, if tennis training had taken place the day before, but all other biochemical values were within normal limits.

Adaptation, Physiological↗
PubMed1991

[Tachycardic arrhythmias in athletes. Incidence, clinical relevance and prognostic significance].

Morphological and functional cardiac changes are found in all active athletes. Of particular interest would appear to be tachycardic arrhythmias, since they have been associated with cases of sudden death during sports activities. In comparison with patients with underlying cardiac disease, few data on the incidence and prognostic significance of tachycardic arrhythmias in athletes are available. The aim of the present study was to characterize and identify prognostically relevant tachycardic arrhythmias in this latter population.

Death, Sudden↗
PubMed1991

Influence of acute maximal exercise on lecithin:cholesterol acyltransferase activity in healthy adults of differing aerobic performance.

To document the possible influence of a single episode of maximal aerobic stress on the serum lecithin:cholesterol acyltransferase (LCAT) activity in subjects with differing histories of training, two groups of healthy male adults [controls (C), n = 18, 28.6 years, SD 5.2, 50.1 ml.kg-1.min-1 maximal O2 uptake (VO2max), SD 5.3; endurance trained athletes (T), n = 18, 31.4 years, SD 8.8, 65.0 ml.kg-1.min-1 VO2max, SD 2.8] were examined in a maximal aerobic stress test. In addition to the routine assessment of lipid status, LCAT activity was measured immediately before and after exercise. At rest nearly identical LCAT activity values were found in both groups: C 64.4 nmol.ml-1.h-1, SD 16.7 vs T 65.0 nmol.ml-1.h-1, SD 20.9. The post-exercise LCAT values induced by the maximal stress test increased significantly to (C) 95.7 nmol.ml-1.h-1, SD 23.5, +48.6%, P less than 0.001; (T) 83.5 nmol.ml-1.h-1, SD 24.3, +29.1%, P less than 0.01. Neither the pre nor the postexercise individual LCAT activity values showed any significant correlation to the corresponding data on physical performance.

Adolescent↗
PubMed1991

Training-overtraining. A prospective, experimental study with experienced middle- and long-distance runners.

Overtraining may be one frequent cause of stagnation or decrease in performance capacity of athletes. Israel (19) differentiates between addisonoid (parasympathetic) and basedowoid (sympathetic) overtraining, characterized by inhibition or excitation. We tried to induce an overtraining syndrome in 8 experienced middle- and long-distance runners, based on an increase in training volume from an average 85.9 km (week 1) to 115.1 km (week 2) and 143.1 km (week 3) to 174.6 km per week (week 4). The influence of this training on cardiovascular, metabolic and hormonal parameters was examined with special respect to plasma and urinary catecholamines. Laboratory testing including graded treadmill running was performed on the days 0, 14 and 28. Training was held six days each week, with nearly 30 km per day in the fourth week. A stagnation in endurance performance capacity (running velocity at the aerobic-anaerobic transition range) and a decrease in maximum working capacity were observed in 6 and a stagnation in 2 of the 8 sportsmen, indicated by a decrease in total running distance from 4719 + 912 m to 4361 + 788 m during incremental treadmill ergometry. The sportsmen could neither improve nor could they even approximately reach their personal records during the subsequent competitive season. Subjective complaints, classified on a four-point scale, increased from 1.2 (week 1) to 3.2 in week 4. Glucose, lactate, ammonia, glycerol, free fatty acids, albumin, LDL, VLDL cholesterol, hemoglobin level (transient), leukocytes, and heart rate (before and during exercise) decreased significantly. Urea, creatinine, uric acid, GOT, GPT, gamma-GT, serum electrolytes (except phosphate and calcium) remained constant at the measuring times, CPK was elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Hypothalamic-pituitary-adrenal axis function in elderly endurance athletes.

To explore the effects of repeated episodes of hypercortisolemia on hypothalamic-pituitary-adrenal axis regulation, we studied plasma ACTH and cortisol (CORT) responses to 100 micrograms human CRH (hCRH) in 10 dexamethasone (1.5 mg)-pretreated elderly endurance athletes who had abstained from physical activity for at least 48 h before testing and 13 sedentary age-matched controls. Basal CORT and ACTH levels were indistinguishable between runners and sedentary controls, whereas CORT responses to hCRH were significantly increased in endurance athletes, and ACTH responses tended to be higher in this group. Comparing the dexamethasone/hCRH test results of the runners with those of an age-matched sample of previously studied depressed patients (n = 9), similar hormone responses to CRH challenge were noted. The mechanisms underlying these alterations may either be a stepwise decrease in corticotropic sensitivity to the negative feedback signal leading to a switch to positive glucocorticoid feedback, an enhanced cosecretion of ACTH secretagogues such as vasopressin, or a combination of both. In conclusion, hypothalamic-pituitary-adrenal axis physiology seems to be determined by previous stressful events associated with hypercortisolemia, regardless of its etiology.

Adrenocorticotropic Hormone↗
PubMed1991

Clinical and therapeutic use of probucol.

Previous studies showed that probucol significantly lowered both LDL cholesterol and HDL cholesterol. In addition, there is evidence that as an essential antioxidant probucol causes variations in cellular interactions and cardiovascular functions in patients. Therefore, 14 hypercholesterolemic men were investigated before and during probucol treatment in order to document both serological and cardiovascular changes with special regard to (1) serum apolipoproteins (A-I, A-II, B, C-II, C-III, E) (2) composition and distribution of HDL and LDL subfractions, (3) cardiovascular performance using a maximum exercise stress test, and (4) induced platelet aggregation. In contrast to reduced total, LDL-, and HDL-cholesterol values, highly significant changes in serum apolipoproteins were found in apoA-I only; apoA-II was unchanged both in serum and in HDL subfractions. Despite unchanged serum apoB levels, the results showed that probucol has a significant influence on the composition (TG/FC ratio) of LDL particles of d less than 1.019 g/ml. In addition to lipoprotein-related changes, significant decreases in heart rate data and cardiac work and in lactic acid accumulation during exercise were induced by probucol administration; furthermore, adrenaline-induced platelet aggregation was also decreased. The results found significantly demonstrate that probucol acts by way of more mechanisms than cholesterol lowering alone. This aspect may be of special interest in the clinical use of probucol, because a coronary-risk-reducing therapy should not affect the lipoprotein profile only.

Adult↗
PubMed1990

[Prevention and therapy of obesity with diet and sports, an ambulatory therapy program for overweight children].

Dietary restriction together with ongoing power-orientated training provide best results in the therapy and prevention of obesity. Diet can reduce the resting metabolic rate by up to 20% within 14 days. Physical activity stimulates the resting metabolic rate and counteracts this energy saving effect, but is especially important for maintaining a steady state after weight reduction. Exercise reduces the risk factors accompanying obesity by favorable adaptation of the sympathoadrenergic system to physical activity. This can be seen in the effects on heart rate, stroke volume, blood pressure, as well as glycogenolytic and lipolytic activities. Body fat especially in the abdominal area, which is particularly connected with atherogenic risk, is diminished. Weight reduction is accompanied by a decrease of the cardioprotective cholesterol fraction. Diets high in unsaturated fatty acids combined with a staying power training have a synergistic effect: they reduce a decrease of HDL. It is difficult to demonstrate risk factors connected with overweight children. However, from the preventive medicine point of view it is advisable to start with therapeutic measures during childhood. In an out-patient pilot project we surveyed 18 obese children aged 9 to 13 years. The therapy plan consisted of dietary restriction (1200 kcal/d), an exercise program performed 3 times a week, and psychological assistance. All children of 12 to 13 years arrived at an overweight level less than 20%, the younger ones displayed a lower weight reduction effect. All 18 improved their aerobic capacity. In the 1st months of treatment, HDL-cholesterol decreased slightly, but increased above pre-treatment level, later on. We did not see any vitamin deficiencies during the therapeutic regimen.

Cardiovascular System↗
PubMed1990

[Effect of beta blockade on hemodynamics in physical exertion].

Beta-receptor blocking agents are known for more than 20 years. They are of definite use in the therapy of arterial hypertension and coronary heart disease. Beta-blockers lower the sympathoadrenergic discharge to the heart and circulation, particularly if the former is increased. Beta-blockers induce a negative chronotropic and inotropic effect and inhibit beta 2-mediated vasodilation. Thus beta-sympathicolysis during physical activity results in damping of heart rate increase and of elevation of cardiac contractility. Systolic blood pressure does not increase much, and usually there is no decline in diastolic blood pressure, due to elevated peripheral resistance. With adequate dosage, there may even be a slight increase in diastolic pressure, an effect eventually vaning in chronic therapy. Pulmonary capillary wedge pressure is elevated to above normal via inhibition of contractility and relaxation of the heart. Stroke volume, cardiac output and the double-product decrease, the arteriovenous oxygen difference under exercise increases clearly and the maximum aerobic performance capacity decrease in healthy individuals. In coronary patients, this may protect against cardiac overload and increase symptom-free physical work capacity, due to a relative decrease in the myocardial O2 requirement and improved coronary perfusion resulting from prolonged diastole. With verified indication (hypertensive-hyperkinetic impairments of cardiovascular function, coronary heart disease), the goal is an overlapping, endurance-oriented training to reduce the overall sympathetic activation, in order to minimize medication in the long run.

Adrenergic beta-Antagonists↗
PubMed1990

Structure of human low-density lipoprotein subfractions, determined by X-ray small-angle scattering.

The structure of low-density lipoprotein (LDL) particles from three different density ranges (LDL-1: d = 1.006-1.031 g/ml; LDL-3: d = 1.034-1.037 g/ml; LDL-6: d = 1.044-1.063 g/ml) was determined by X-ray small-angle scattering. By using a theoretical particle model, which accounted for the polydispersity of the samples, we were able to obtain fits of the scattering intensity that were inside the noise interval of the measured intensity. The assumption of deviations from radial symmetry is not supported by our data. This implies a spread-out conformation of the apolipoprotein B (apoB) molecule, which appears to be localized in the outer surface shell. A globular structure is not consistent with our data. Furthermore, different models exist concerning the structure of the cholesterol ester core below the phase transition temperature. The electron density data suggest an arrangement in which the steroid moieties are localized at average radii of 3.2 and 6.4 nm. Model calculations show that packing problems can only be avoided if approximately half of the acyl chains of each shell are pointing towards the center of the particle, the other half towards the surface. This arrangement of the acyl chains has never been proposed before. The LDL particles of different density classes differ mainly with respect to the size of the core but also with respect to the width of the surface shells. Model calculations show that the size of different LDL particles can be accurately predicted from the compositional data.

Apolipoproteins B↗
PubMed1990

Interval versus continuous exercise training after coronary bypass surgery: a comparison of training-induced acute reactions with respect to the effectiveness of the exercise methods.

In order to improve endurance by exercise on a bicycle ergometer, both the interval method (I) (exertion and recovery phases alternate each minute) and the continuous method (constant exertion) can be employed. We examined the effects of both methods on the following parameters: heart rate, blood pressure, rate-pressure product, glucose, lactate, and catecholamine levels, and physical performance. Two groups of nine male patients were trained daily on a bicycle ergometer for 3.5 weeks. These patients had undergone coronary bypass surgery 24 and/or 26 days before the training started. The training heart rate was set at 86% of the individual maximum heart rate. In the last week of training, the exercise intensity in both patient groups, following either I or C regimen, was 20:121 W and 83 W respectively. The exercise training lasted 20 minutes with the following findings: (1) there were no significant differences in blood pressure, rate-pressure product, rates of glucose and catecholamines, and (2) there was a significantly higher rate of lactate in the second ten minutes of the I training. Before and after the training period, the patients were subjected to a multistage bicycle ergometer exercise test (sitting). The following results obtained after the training favor the I method: (1) patients' physical performance increased (+0.63 vs. +0.26 W/kg; p less than 0.001); (2) heart rate was lower at rest (-9 vs. -4 beats/min; p less than 0.04) and at 75 W (-12 vs. -2 beats/min; p less than 0.02); (3) rate-pressure product was lower at rest (-1675 vs. -291; p less than 0.04) and at 75 W (-2810 vs. -735; p less than 0.05); (4) rate of lactate was lower at 75 W (-0.83 vs. -0.33 mmol/l; p less than 0.04); (5) catecholamines were not lowered by I or C training, and no differences between the two groups could be observed. Exercise training according to the I method involves both the aerobic and anaerobic capacity of the organism, whereas exercise training according to the C method involves only oxidative capacity. After coronary bypass surgery, the I method is better suited to increase physical performance and is more effective in economizing the cardiac function.

Adult↗
PubMed1990

Effects of age and physical performance capacity on distribution and composition of high-density lipoprotein subfractions in men.

The influences of age and maximal aerobic capacity (VO2max) on serum lipoproteins with special regard to the concentration, composition and distribution of high density lipoprotein (HDL) subfractions were investigated in 51 healthy males of different characteristics: younger than 35 years, untrained (n = 14, mean age 28.2 years, SD 6.0; VO2max, 47.9 ml.kg-1.min-1, SD 5.8) and trained (n = 11, mean age 27.9 years, SD 4.3; VO2max, 61.1 ml.kg-1.min-1, SD 5.1), older than 50 years untrained (n = 14, mean age 58.9 years, SD 5.9, VO2max, 29.3 ml.kg-1.min-1, SD 5.3) and trained (n = 12, mean age 59.3 years, SD 7.2, VO2max, 45.7 ml.kg-1.min-1, SD 7.7). The fasting-state serum concentrations of total cholesterol, tri-acylglycerol and lipoprotein-cholesterol were measured. The HDL-subfractions were separated by density (rho) gradient ultracentrifugation. Concentrations of cholesterol, cholesterylester, tri-acylglycerol, phospholipids, apolipoprotein (apo) A-I and A-II were measured in the subfractions HDL2b: rho = 1.063-1.100 g.ml-1; HDL2al: rho = 1.00-1.110 g.ml-1; HDL2a2: rho = 1.110-1.150 g.ml-1; HDL3: rho = 1.150-1.210 g.ml-1. Elderly untrained subjects showed increased serum concentrations of total-, very low- and low density lipoprotein-cholesterol and elevated tri-acylglycerol levels. The HDL-cholesterol concentration was decreased, due to reduced concentrations of HDL2-subfractions. Significant changes in the composition of HDL2-subfractions were found in elderly untrained subjects. The HDL2-subfractions had more protein, a decreased apoA-I:A-II ratio and less phospholipids in comparison to HDL2-subfractions from younger untrained and trained, and elderly trained subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗