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Biomedical subjects

J Keul

Publications and source records attributed to J Keul.

At least 163 records · Page 9Linked to original sources
PubMed1986

Alpha-2-adrenoreceptor density on intact platelets and adrenaline-induced platelet aggregation in endurance- and nonendurance-trained subjects.

Alpha-2-adrenoreceptor density on intact platelets was evaluated in 17 sportsmen, 8 of whom were endurance-trained athletes. Receptor density was determined as being equivalent to 3H-Yohimbine, specifically bound on intact platelets. Adrenaline-induced aggregation of platelets in vitro was additionally ascertained. Bmax (maximal binding) and KD (dissociation constant) were significantly lower in endurance-trained athletes (148 fmol per 10(9) platelets, KD = 0.92 nmol) than in the nine nonendurance-trained individuals (284 fmol, KD = 1.79 nmol, P less than 0.01), amounting to 89 receptors per cell (endurance-trained subjects) and 171 (nonendurance-trained subjects). No significant change of receptor density or affinity was observed subsequent to exhaustive exercise in the group of eight endurance-trained individuals. Bmax values and oxygen uptake capacity correlated negatively (r = -0.78, P less than 0.001) and Bmax values and induced platelet aggregation in vitro positively (r = 0.79, P less than 0.001). Data may indicate a reduced sensitivity of platelets in endurance-trained subjects.

Adult↗
PubMed1986

Skeletal muscle enzyme activities in healthy young subjects.

In three groups of healthy young subjects (n = 33; mean ages 6.4, 13.5, 17.1 years), muscle enzyme activities (creatine kinase, hexose phosphate isomerase, aldolase, pyruvate kinase, lactate dehydrogenase, citrate synthase, fumarase) of the vastus lateralis muscle were investigated to show age-dependent variations. A significant age-dependent increase in aldolase (P less than 0.05) and pyruvate kinase (P less than 0.01) activity and a decrease in fumarase activity (P less than 0.01) were computed. In relation to the age-dependent variation, maximum LDH activities could be measured at an age of 12-14 years; significantly decreased activities of the glycolytic enzymes could only be found in the youngest group.

Adolescent↗
PubMed1986

[Primary orthostatic hypotension].

We studied a 25-year-old man suffering from primary orthostatic hypotension whose blood pressure decreased to 65/45 mm Hg during orthostasis and to 95/70 mm Hg during ergometric exercise (50 and 100 watt), and whose heart rate responses were inadequate. Resting catecholamine levels were within the normal range and did not show any significant increase related to orthostasis or to ergometric exercise. Hypersensitivity was observed to low doses of intravenous noradrenaline and isoproterenol. Specific binding of 3H-Yohimbine to intact platelets revealed a normal number of alpha-2-adrenoreceptors in agreement with the adrenaline-induced platelet aggregation in vitro, which was, however, in contrast to hypersensitivity to noradrenaline. Specific 3H-Dihydroalprenolol binding to intact polymorphonuclear leucocytes revealed an increased beta-2-adrenoreceptor density in agreement with hypersensitivity to Isoproterenol. Prescription of Fludrocortison improved orthostatic hypotension.

Adult↗
PubMed1985

[Energy yield during physical exertion].

Every energy demanding process in the skeletal muscle is associated with the use of adenosinetriphosphate, the essential muscular high-energy phosphate. ATP is rephosphorylated by ADP (= adenosine diphosphate) and this process depends on the type, intensity and duration of the physical exercise. At the beginning of a vigorous physical exercise utilization of intramuscular ATP and phosphocreatine is predominant (= anaerobic-alactacide energy yielding). Then the ATP rephosphorylation based on the conversion of glycogen and glucose to lactate, especially by an exercise duration till 2 min (= anaerobic-alactacide energy yielding). Toward this duration or if the exertion intensity at start has been below 60 to 70% of maximal physical performance, ADP is rephosphorylated during oxidative phosphorylation by the skeletal muscle mitochondria using glycogen, glucose or free fatty acids as energy fuel. Training, age and sex may influence anaerobic and aerobic energy-yielding as well as metabolism and ultrastructure of skeletal muscle.

Adenosine Triphosphate↗
PubMed1985

[Excretion of free dopamine, noradrenaline and adrenaline in 190 males in relation to age and blood pressure].

The 24-h urinary excretion of free catecholamines was evaluated in: 62 healthy and 20 hypertensive (primary hypertension, stage 1 and 2) male subjects, less than or equal to 39 years of age, and in 64 healthy and 44 hypertensive (primary hypertension, stage II and III) male subjects greater than or equal to 40 years of age. Noradrenaline excretion correlates positively with the age, based on the date of all 190 subjects (r = 0.29, P less than 0.001) and for the 126 healthy subjects (r = 0.37, P less than 0.001), however not for the 64 hypertensive patients. Adrenaline and dopamine excretion does not show any significant correlation with the age of the investigated subjects, neither for all 190 subjects nor for the different groups. The noradrenaline-adrenaline ratio also correlates positively with the age (r = 0.28, P less than 0.001, n = 190). The younger hypertensives (less than or equal to 39 years of age) show a slightly but not significantly higher noradrenaline excretion; this, however, is significantly higher in the group of older hypertensive subjects (P less than 0.05; greater than or equal to 40 years of age). No significant differences are recognizable for adrenaline and dopamine excretion between normotensive and hypertensive subjects.

Adult↗
PubMed1985

[Conjugated plasma catecholamines are lower in power athletes at rest and in physical work than in untrained probands].

Lower levels of free plasma catecholamines, noradrenaline and adrenaline were recently described in statically trained athletes under identical work loads during incremental cycling as compared with untrained control subjects. These differences point to a control of sympathetic activity by static training. Theme of the presented investigation is the question of additional training-dependent alterations of the conjugated plasma catecholamines in statically trained athletes. Eight competition weight lifters (21 +/- 2 years of age; 73 +/- 10 kg body weight) and seven untrained healthy control subjects (26 +/- 6 years; 75 +/- 4 kg) were investigated. The conjugated catecholamines were radioenzymatically determined as the difference between total and free catecholamines. The investigated subjects performed an incremental, exhaustive bicycle ergometric test in an upright body position. Before exercise, the levels of conjugated plasma dopamine (P less than 0.10), of conjugated noradrenaline (P less than 0.001) and conjugated adrenaline (P less than 0.10) are 2-3 times lower in statically trained athletes than those of the control subjects. The conjugated catecholamines did not show any significant changes during exercise, the significant differences between both groups (P less than 0.05-P less than 0.01) were therefore also observed during exercise. In contrast to the free plasma catecholamine responses, the conjugated catecholamine fractions are seen as indicators of long term alterations of the sympathetic activity.

Adult↗
PubMed1985

Ferritin in erythrocytes and plasma of patients with iron overload.

Erythrocyte and plasma ferritin was followed in 13 patients with iron overload undergoing phlebotomies for at least 6 months in comparison with untreated patients and normal males. Plasma ferritin was widely scattered with an average of only twice the normal, whereas erythrocyte ferritin was highly elevated to about twelve times the normal (p less than 0.0001). - The time course of plasma and erythrocyte ferritin during phlebotomy therapy was analyzed in 3 patients with idiopathic hemochromatosis. Three stages were established: 1. plasma ferritin dropped gradually into the normal range while erythrocyte ferritin remained high, 2. appropriate phlebotomies maintained normal plasma ferritin and high erythrocyte ferritin, and indicated a monthly uptake of dietary iron of 150-200 mg at a steady state, 3. at low plasma ferritin levels, erythrocyte ferritin was rapidly decreased by further intensive phlebotomy therapy. Based on the presumed net removal of iron, 1 microgram/l plasma ferritin was equivalent to 3-6 mg of body iron and 1 microgram/l erythrocyte ferritin to somewhat less than 1 mg of body iron. - An elevated erythrocyte ferritin during phlebotomy therapy in iron overload not only depends on body iron stores like plasma ferritin but may also be regulated by the activity of erythropoiesis.

Adult↗
PubMed1985

Capillary-venous differences of free plasma catecholamines at rest and during graded exercise.

Levels of free plasma catecholamines were simultaneously determined in 10 cyclists using capillary blood from one ear lobe and venous blood from one cubital vein. Catecholamine concentrations were higher in the ear lobe blood than in the venous blood at rest and during graded exercise. Average differences amounted to 1.7 nmol X 1(-1) (dopamine), 2.1 nmol X 1(-1) (noradrenaline) and 1.9 nmol X 1(-1) (adrenaline) at rest and increased only to 8.8 nmol X 1(-1) for noradrenaline during exercise. We assume that higher concentrations of dopamine and adrenaline in the capillary blood point to a significant neuronal release of these catecholamines, similar to noradrenaline. Catecholamine concentrations in capillary blood may better reflect sympathetic drive and delivery of catecholamines to the circulation than the concentrations in venous blood.

Adult↗
PubMed1985

Influence of maximum aerobic capacity and relative body weight on the lipoprotein profile in athletes.

The relationship between the individual maximum aerobic capacity (MAC) as well as the relative body weight (BW) and the corresponding lipoprotein profile was studied in male national-class athletes (n = 120, 18-36 years old). Using a stepwise regression analysis, it was shown that only the apoliprotein A-I and HDL cholesterol levels correlated primarily with the maximum aerobic capacity, whereas the serum concentrations of total cholesterol, triglycerides, apo B and LDL cholesterol as well as the apo B/apo A-I ratio were significantly dependent on the relative body weight. Only the HDL/tot. cholesterol ratio was significantly related to both variables, MAC and BW (r = 0.570; P less than 0.001).

Adolescent↗
PubMed1985

Plasma catecholamine and blood lactate cumulation during incremental exhaustive exercise.

Six healthy male subjects performed two different incremental treadmill tests. Test 1 started at a velocity of 8 km.h-1 and was increased by 2 km.h-1 steps until subjective exhaustion was reached. The running time was 3 min per step with 30-s interruptions between two successive steps. In test 2, identical work loads were imposed on the subjects. However, there were 30-min recovery periods between two successive exercise steps. Heart rate, oxygen uptake (only in test 1), blood lactate, and free plasma catecholamine levels were simultaneously estimated during both testings and additionally at the end of each 30-min recovery period in test 2. Subjects reached 57 +/- 6 ml.kg-1. min-1 oxygen uptake. Only slight lactate and catecholamine differences were observed between both tests at moderate work loads. Lactate levels (+30%) as well as noradrenaline and adrenaline responses (+60%-90%) were higher in the cumulative experiment (test 1) at work loads corresponding to 70%-80% of the oxygen uptake capacity as compared to the noncumulative testing procedure (test 2). A further increase of these differences to approximately 50% (lactate), 156% (noradrenaline), and 165% (adrenaline) has to be considered to be near the exhaustion level. In conclusion, during incremental treadmill exercise in a cumulative design, a significant cumulation effect leads to an overproportional increase of lactate and catecholamine levels at submaximal--maximal work loads.

Adult↗
PubMed1985

[Estimation of heart size--x-ray versus 2-dimensional echocardiography].

Radiologic heart volume measurement (HV) and two dimensional echocardiographic estimation of left ventricular volume and ejection fraction (EF) were carried out in 108 healthy subjects and 68 patients with hypertony, dilatative cardiomyopathy and hypertrophic-obstructive cardiomyopathy (HOCM). Healthy subjects show a close relationship between echocardiographic determined volume and absolute heart volume (HV), in patients with hypertony, dilatative cardiomyopathy and HOCM there is also a significant correlation. However, no correlation exists between EF and HV and HV/kg in patients with hypertony and HOCM, whereas patients with dilatative cardiomyopathy show a high significant inverse relationship. It is concluded that these results are caused by great differences in muscle mass. The clinical value of radiologic heart volume as a parameter of left ventricular systolic function seems to be low and depends on cause of the heart enlargement.

Cardiac Volume↗
PubMed1985

[Capacity for regression of the athletic heart].

Dynamic exercise leads to an increase in heart size and to hypertrophy depending on the intensity and extent of training. The maximum of left ventricular muscle mass is reached at 3.5 g/kg, which is 70-80% higher compared to untrained subjects. The mass/volume ratio remains constant (left ventricle 1.0-1.2 g/ml). Systolic wall stress and ejection fraction of the enlarged left ventricle do not change. No heart hypertrophy can be found in athletes carrying out maximum static exercise. Heart size and heart hypertrophy regress when training stops completely. The velocity of regression is not exactly known, a maximum regression of 10-15% within three weeks is probable. Investigations of former athletes show a decrease of heart size and heart hypertrophy, especially when related to body weight. The degree of regression depends on the actual physical activity; another factor may be the duration of the competition activity. It is supposed that only a small degree of training prevents the decrease of heart enlargement, heart hypertrophy and higher performance ability. Damage to the cardiovascular system caused by maximum exercise training cannot be found.

Cardiac Output↗
PubMed1985

[Free and conjugated plasma catecholamines, lactate behavior and oxygen uptake at rest and in staged physical exertion as well as alpha receptor density in intact thrombocytes in trained athletes].

The influence of chronic static training on free and conjugated plasma catecholamines was investigated in 8 statically trained athletes (21 +/- 2 years of age) at rest and during incremental ergometric cycling. Plasma catecholamines are seen as biochemical indicators of the over-all sympathetic activity. Alpha-2-adrenoreceptors were additionally determined as one parameter of the organism's sensitivity to catecholamines. During modest and heavy exercise, free plasma noradrenaline and adrenaline are comparably low in statically and endurance trained athletes. They are lower than in untrained subjects. During exhaustion, however, free adrenaline responses of the statically trained athletes only amount to 30-50% of the concentrations observed in endurance trained athletes and untrained subjects. Free plasma dopamine and conjugated plasma catecholamines do not show any significant changes during ergometric exercise. Free and conjugated catecholamines correlate positively. Positive correlations are also observed between blood pressure and plasma catecholamines. These correlations however are clearer between conjugated catecholamines and blood pressure. This is also recognizable for the negative correlation between alpha-2-receptor density on intact platelets (1078 +/- 323 binding sites per cell) and conjugated catecholamines. In conclusion, statically trained athletes also show an alteration of sympathetic tone (catecholamines) comparable to that observed in endurance trained athletes. Maximal adrenaline responses however are lower in statically trained athletes than in endurance trained or untrained subjects. The alpha-adrenoreceptor density on intact thrombocytes seems to be increased in statically trained athletes.

Adult↗
PubMed1985

[Excretion of free catecholamines in relation to age, sex and blood pressure].

The influence of age, sex and hypertension on urinary excretion of free catecholamines was evaluated in 190 men (64 hypertensive patients) and 75 women (10 hypertensive patients). Noradrenaline correlates positively with age in healthy men (r = 0.37, p less than 0.001) and women (r = 0.36, p less than 0.001). Adrenaline and dopamine do not show any significant correlation with age. Noradrenaline excretion is slightly higher in young (less than or equal to 39 years of age) and significantly higher in old (greater than or equal to 40 years of age) hypertensive patients than in age-matched control subjects. Noradrenaline (32 +/- 15 micrograms X 24 h-1) and adrenaline excretion (9 +/- 7 micrograms X 24 h-1) are lower in the group of younger women than in younger men (52 +/- 23 and 19 +/- 12 micrograms X 24 h-1). We assume that the lower excretion of free catecholamines in younger women is significant for a lower sympathetic activity.

Adult↗