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Biomedical subjects

J Keul

Publications and source records attributed to J Keul.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1990

ECG variants and cardiac arrhythmias in athletes: clinical relevance and prognostic importance.

These findings permit the following conclusions on cardiac changes induced by high-performance sports and high levels of training. Sinus bradycardia and AV block can frequently be observed in athletes, but they do not require attention as long as they are asymptomatic or do not produce pauses exceeding 4 seconds. Persistent rather than transient second-degree AV block or Mobitz second- or third-degree AV block is an extremely unusual finding even in athletes and should be considered a sign of organic lesions until proved otherwise. Supraventricular and AV node ectopic beats are not more frequent in athletes than in the general population except for atrial fibrillation. WPW syndrome is of particular importance, since rapid conduction to the ventricle via the accessory AV pathway is possible, especially if there is a tendency toward atrial fibrillation. Likewise caution is required in athletes with hypertrophic cardiomyopathy. Here hemodynamic deterioration must be anticipated with the occurrence of supraventricular tachycardia. Simple ventricular arrhythmias occur among athletes with the same frequency as in the general population, but they usually disappear with exercise. The occurrence of complex ventricular forms of arrhythmia should always prompt cardiologic examination in search of underlying cardiac disease, particularly hypertrophic or dilated cardiomyopathy. The presence of ventricular arrhythmias without evidence of underlying heart disease does not indicate a special or increased risk of sudden cardiac death. A higher incidence of right and/or left ventricular hypertrophy, exercise-reversible ST elevation, and exercise-reversible changes in T waves (T negativity, sharp and/or excessive T waves) can be considered physiologic changes in the ECGs of athletes. These changes correlate closely with the type of sports activity and degree of training and are reversible when the activity is stopped. Horizontal ST segment depression are by contrast very rare in athletes and should always be clarified by cardiologic examination. Exercise-induced sudden cardiac death in athletes is unusual without preexisting heart disease. The cause of sudden cardiac death among athletes less than 40 years of age can be predominantely ascribed to congenital heart diseases (such as hypertrophic cardiomyopathy or coronary anomalies). In athletes more than 40 years of age and with increasing age, coronary heart disease is the most frequent autopsy finding. A corresponding risk stratification should take these partial dangers into account.

Arrhythmias, Cardiac↗
PubMed1990

[Acute cardiovascular and metabolic changes in interval and endurance training in selected patients following aortocoronary bypass operation].

UNLABELLED: This study compared the acute changes of cardiovascular and metabolic reactions during interval and continuous training after coronary bypass surgery. Two groups of 9 male patients (age: 59 +/- 4 and 56 +/- 6 years, resp.) each trained on bicycle ergometer start on post-operative days 24 and 26, resp. In both training groups training heart rate was set at 86% of individual maximum heart rate. In the last week of training the exercise intensity in the group of patients who were trained by the continuous method was at 83 watts, and at 20:121 watts in the group of patients who were trained by interval method (rest:work each 1:1 min). At this exercise training that lasted for 20 min the acute response of heart rate, blood pressure, rate-pressure product, glucose, lactate and catecholamines was measured. RESULTS: In both methods there were no significant differences in systolic and diastolic pressure, rate-pressure product, in glucose or catecholamine levels. However, there was a significantly higher rate of lactate in the second 10 min of the interval training. And, in spite of higher peripheral exercise intensity by interval training, there was no higher cardiac work than by the continuous training. These findings suggest that interval training strains the oxidative capacity of the trained muscles in a more intensive and direct way than does continuous training.

Adult↗
PubMed1990

[Effects of interval versus endurance training of increasing performance, cardiovascular function, metabolism and catecholamines in selected patients after aortocoronary bypass operation].

This paper reports the effect of endurance exercise training on bicycle ergometer by interval method (work and interval each 1:1 min) and continuous method on increase of physical performance, decrease of heart rate, rate-pressure-product, glucose, lactate, and catecholamines. Two groups of nine male patients (aged 59 +/- 4 vs 56 +/- 6 (mean +/- SD)) after coronary bypass surgery each participated in the inpatient rehabilitation training. Training started 24 and 26 days, resp., after surgery and lasted for 3.5 weeks. Frequency and duration of exercise training: Monday-Friday 1 x 20 min and 1 x 25 min per day; Saturday/Sunday each 1 x 25 min per day. In the interval group and the continuous group the exercise training intensity was set at 86% of individual max. heart rate. In the last week of training mean exercise intensity was at 83 watts in the group of patients who were trained by the continuous method and at 20:121 watts in the group of patients who were trained by the interval method. Before and after the training period patients underwent a multistage bicycle ergometer exercise test in sitting position. Beginning at 25 w, each stage was increased by 25 w, whereby each stage lasted 3 min. Cutoff criteria were heart rate (220 - age x 0.85) and/or fatigue of the leg muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Doping--also a problem in general practice?].

In 1986, the Medical Commission of the IOC defined doping as the use of pharmacological substances belonging to disallowed groups of active substances (stimulants, narcotics, anabolic steroids, beta-blockers, diuretics). With certain restrictions, this applies also to alcohol, local anesthetics and corticosteroids. The use of disallowed methods (blood doping, manipulation of a urine sample) is also forbidden. These days the greatest importance is attached to anabolic steroids (including testosterone), since these substances--discontinued in good time--cannot be detected on the day of competition but still have a promoting effect on performance. Competitive sports prepared the way here for the use of anabolic steroids in general athletics and in particular usually non-olympic sports (such as bodybuilding). Against this background, effects, adverse effects and the risks of anabolic steroid use are discussed. The aim must be to prevent the use of doping, especially in uncontrollable general sports, by promoting proper awareness.

Anabolic Agents↗
PubMed1989

Blood and serum status of water- and fat-soluble vitamins in athletes and non-athletes.

Water- and fat-soluble vitamins have a key function in many metabolic processes and are of special importance for athletic performance. The water-soluble vitamins thiamine, riboflavin, and pyridoxine as well as the fat-soluble vitamins beta-carotene, retinol, and alpha-tocopherol were determined by methods based on high-pressure liquid chromatography (HPLC) in serum or blood of non-athletes and athletes of different sports such as bodybuilders, cyclists, cross-country skiers, marathon runners, and swimmers. The values for the water-soluble vitamin were much higher in athletes, whereas the values for the fat-soluble vitamins were not much different compared to those found in non-athletes.

Adult↗
PubMed1989

The long-term involution of physiological cardiomegaly and cardiac hypertrophy.

The long-term involution of physiological cardiomegaly and cardiac hypertrophy. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 244-249, 1989. Forty-five former athletes in endurance disciplines, primarily Olympic medalists and World Cup, European Cup, and German champions, for whom results of an exercise ECG and radiological heart volume measurement were available from their active competitive phase, were examined. The study protocol included clinical examination, laboratory controls, resting and exercise ECG, determination of cardiac volume, and one- and two-dimensional echocardiographic examination. Of the 45 former athletes contacted, 38 appeared for examination. Of these, four presented with heart disease (two with infarction, one with aortic stenosis, and one with arrhythmia). The remaining 34 were divided into groups of still active (more than 300 kcal.wk-1) and inactive (less than 300 kcal.wk-1) athletes. The interval between the first and second examination averaged 23 yr. The active former athletes showed a weight increase of 5.2% (P less than 0.01) and a reduction of 14% in ergometric performance (P less than 0.02). The inactive group had a marked weight increase of 17.4% (P less than 0.001); the ergometric performance was lowered by 20% (P less than 0.001). The absolute heart size had decreased in the active group by 6.1% (NS) and the relative heart size by 10.7% (P less than 0.005); the corresponding values in the inactive group were 4.5% (NS) and 18% (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1989

[Regression of hypertension-induced left heart enlargement in an endurance athlete treated with verapamil RR].

In October 1987, Stage II arterial hypertension, probably of primary genesis, was diagnosed in a 52-year-old male patient. There was marked left-ventricular hypertrophy (left-ventricular muscle mass 224g, corresponding to 2.99 g/kg: mass-volume ratio of the left ventricle 1.9 g/ml; end-diastolic septum thickness 15 mm, posterior wall thickness 13 mm). The patient is engaged in endurance sports for 5-12h each week and participates regularly in competitions. He was not advised to terminate athletic activities. The patient's submaximum performance (supine ergometry) is 3.3 watts per kg body weight. Under therapy with 2 x 240 g Verapamil per day, blood pressure decreased in the course of a year by 30/30 mm Hg at rest and 30/20 mm Hg at a specified exercise level. The left ventricular muscle mass decreased by about 70g, the mass-volume ratio normalized to 1.3 g/ml.

Blood Pressure↗
PubMed1989

[Form, size and function of the sports heart--differentiation from pathological findings].

Dependent on the nature, intensity and scope of muscular exercise, regular athletic training can result in changes in the size and form of the heart, which can be recorded by radiologic and echocardiographic techniques. Brief anaerobic exercise and purely static forms of training (sprint, strength sports) do not produce substantial increases in the size of the heart, but a rotund heart shape with rounding of the cardiac tip and in some cases a discrete increase in the wall thickness of the ventricular myocardium is frequently observed. Dependent on the scope of the training and the intensity, aerobic, endurance-oriented training (endurance sports) can induce considerable enlargement of all cardiac chambers with a change in the cardiac configuration, which is most nearly comparable to combination mitral vitium. Comparison of physiological hypertrophy of the athletic heart with pathological forms of cardiac hypertrophy (such as cardiomyopathies) is in many cases not unequivocally possible with plain X-ray films, but it is usually successful with echocardiographic examination methods.

Adult↗
PubMed1989

Plasma catecholamine and cardiovascular responses to nifedipine in hypertensives WHO-stage II.

77 patients with arterial hypertension were consecutively examined. An evaluable echocardiogram could be recorded for 75 patients. 54 (72%) had non-pathological cardiac findings, 15 (20%) showed concentric left ventricular hypertrophy of the heart (mean left ventricular muscle mass (LVM) 2.5 g/kg or 113 g/m2; mean LVM/EDV 1.6 g/ml). 6 patients had an excentric hypertrophy of the left ventricle (8%). The influence of 10 mg nifedipine (Adalat) sublingual on the heart, blood pressure and sympathetic activity was examined in 15 patients with left ventricular hypertrophy of the heart. 5-10 min after administration, a significant decrease in systolic and diastolic pressures (p less than 0.05) and an increase in plasma noradrenaline (p less than 0.05) and heart rate (p less than 0.01) could be registered. The thickness of the posterior wall and septum decreased in 8 to 10 of the 15 patients, EDV, shortening fraction and ejection fraction increased in 8 of the 15 patients. A reduction in peripheral resistance, sympathetic counterregulation accompanied by an increase in heart rate, shortening and ejection fractions with increased enddiastolic volume and decrease in wall thickness can be observed as the gross effect in the majority of the 15 patients with left ventricular concentric hypertrophy. The decrease in wall thickness as a relaxation effect should not be confused with a regression of hypertrophy, whereby the mass-volume ratio shifts toward the normal range under nifedipine.

Administration, Sublingual↗
PubMed1989

[Hypertension, the heart and physical activity (sports)].

Cross-sectional analyses show a lower incidence of hypertension among endurance athletes compared to the general population, but not among strength athletes or high-performance swimmers. The favorable influence of increased physical activity of the endurance type on cardiovascular regulation is based on peripheral adaptation processes with a reduction in sympathetic tone and elevation of parasympathetic tone. The results are a reduction in catecholamine release, in heart rate, and in mean arterial pressure at the same exercise level. Following chronic strength training there is also a slight reduction in catecholamine levels at the same time the vagal activity decreases, so that no reduction in heart rate and pressure, and thus no economization of cardiac work results. Thus, endurance training is suited for prevention and also for the reduction of blood pressure in primary hypertension and for cardiac relief, while strength training is not. In the case of hypertension, physical activity may only be engaged in when the cardiac functional status and other organ impairments are known. The stages of cardiac adaptation and damage, particularly the differentiation between concentric and eccentric hypertrophy, are particularly important. Exercise ECG and echocardiography are therefore obligatory measures prior to initiating physical activity and for continuous monitoring of hypertension. In primary hypertension Stage I (70-80% according to WHO), in which no cardiac hypertrophy is present, endurance training may be started without drug therapy if diastolic pressure is not greater than 104 mmHg and systolic pressure up to 170 mmHg (mild hypertension). Additional drug therapy does not show any convincing advantages. Higher pressures require adjuvant drug therapy. In concentric cardiac hypertrophy (Stage II), there is clear indication for the use of hypotensive drugs. An endurance sport is to be recommended additionally after normalization of blood pressure; the regression of cardiac hypertrophy should be examined within one year. In eccentric hypertrophy (damage stage), "training" is not indicated in addition to drug therapy, but rather physical therapy according to defined exercise capacity. The selection of medications for reducing blood pressure in sportsmen must take into consideration that they have varying performance limiting effects, which may be an essential factor in compliance.

Blood Pressure↗
PubMed1989

[Serum and whole blood concentrations of fat and water soluble vitamins in normal persons and athletes].

Water-and fat-soluble vitamins have a key function in many metabolic processes and are of special importance for athletes. The water-soluble vitamins thiamine, riboflavin and pyridoxine and the fat-soluble vitamins beta-carotene, retinol and alpha-tocopherol were determined by High-Pressure-Liquid-Chromatography (HPLC). The mean serum values in non athletes (ng/ml) were for thiamine 9.23 +/- 3.62, riboflavin 6.17 +/- 2.46 and pyridoxine 12.41 +/- 4.59; the blood values for thiamine 20.12 +/- 7.58, riboflavin 13.43 +/- 3.97 and pyridoxine 18.75 +/- 6.66. The mean values of the fat-soluble vitamins were for beta-carotene 3.76 +/- 252 micrograms/l, retinol 598 +/- 141 micrograms/l and alpha-tocopherol 12.6 +/- 2.9 mg/l. The values of athletes (of different sport disciplines) for the water-soluble vitamins were much higher compared to the values found in non-athletes whereas the values for the fat-soluble vitamins were not much different.

Adult↗
PubMed1988

Isoelectric focusing of apolipoproteins in immobilized pH gradients: improved determination of apolipoprotein E phenotypes.

A method for isoelectric focusing of apolipoprotein E in an immobilized pH gradient with added carrier ampholytes has been developed. This method is an improvement over conventional isoelectric focusing of apolipoprotein E with respect to resolution, reproducibility, and simplicity. Since monosialo isoforms are resolved from the normally cofocusing asialo isoforms, unique patterns are obtained for all 6 common apolipoprotein E phenotypes. The method can also be applied to the screening of apolipoprotein A and C isoforms. Delipidated very low density lipoproteins (VLDL) have been used as the source of apolipoprotein E and C. Apolipoprotein A isoforms were focused directly from detergent-treated serum. Immunodetection of apolipoprotein E using capillary transfer was found to be compatible with the described method.

Apolipoproteins↗
PubMed1988

Influence of probucol administration on lipoprotein cholesterol and apolipoproteins in normolipemic males.

In order to interpret the known lipoprotein changes in probucol-treated patients, serum concentrations of apolipoproteins (A-I, A-II, B, C-II, C-III, E) were measured before, during and after probucol administration (2 X 500 mg p.d.), in 16 healthy males (30.3 +/- 5.6 years old). Cholesterol concentrations were determined in LDL and VLDL fractions as well as in HDL subfractions which were isolated by preparative ultracentrifugation. In addition, apolipoprotein A-I and A-II concentrations were measured in the HDL subfractions. Compared with the baseline values, significant apolipoprotein changes were found in the serum apolipoprotein A-I (151 +/- 18 to 115 +/- 31 mg/dl; P less than 0.001) and C-II levels during administration. The HDL subfraction analysis showed that the decrease of HDL-cholesterol and apolipoprotein A-I (59.9 +/- 23.5 to 34.4 +/- 16.4 mg/dl, P less than 0.001, and 65.7 +/- 49.0 to 37.5 +/- 23.5 mg/dl, P less than 0.05, respectively) was predominantly related to the HDL2b subfraction (d = 1.063-1.100 g/ml).

Adult↗
PubMed1988

Ski-flying: related catecholamine excretion compared with cross-country skiing.

We examined the catecholamine excretion and its performance-diagnostic relevance in athletes of the German National Team during ski-flying and cross-country skiing. Five athletes were examined during the 1986 World Championship ski-flying competition and eight athletes during a 24-km cross-country qualification test. There is little doubt that the special competitive conditions have considerable influence on the usefulness of these data. We decided to publish the results anyway since the results may expand our knowledge about the performance-diagnostic relevance of catecholamine excretion under competitive conditions. During cross-country skiing, the average noradrenaline elimination (1166 pmol.min-1) was about 150% higher and the average adrenaline elimination (243 pmol.min-1) about 30% lower than during ski-flying. The noradrenaline-adrenaline ratio was about 4.8 in cross-country skiing and 1.3-1.5 in ski-flying. Catecholamine excretion does, as expected, therefore permit differentiation of the various strains on the organism. The impression with respect to performance-diagnostic relevance arises that successful athletes show a more stable and lower excretion of noradrenaline under competitive conditions. This can only be a preliminary statement; it should serve to stimulate discussion and further investigations of the problem.

Catecholamines↗