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Biomedical subjects

M Lehmann

Publications and source records attributed to M Lehmann.

At least 289 records · Page 16Linked to original sources
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

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

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

[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↗
PubMed1985

[Induced platelet aggregation in patients with coronary heart disease as well as trained and untrained control persons].

Induced in vitro platelet aggregation (adrenaline and collagen) and serum lipid levels were investigated in 21 postinfarction patients, in 11 of these patients subsequent to therapy with 46 +/- 14 mg nifedipine per os daily for one week and in 21 untrained, 16 endurance-trained, and 17 non-endurance-trained healthy male control subjects. Plasma catecholamine levels at rest (patients) and oxygen uptake capacity (control subjects) were determined in subgroups. Mean platelet aggregation was increased in patients (p less than 0.05) and was decreased both in endurance-trained subjects (p less than 0.05) and in the group of 11 patients subsequent to therapy with nifedipine (p less than 0.01), but platelet aggregation was slightly higher in non-endurance-trained individuals. Adrenaline-induced platelet aggregation correlated positively with collagen-induced aggregation (r = 0.72), with LDL-cholesterol fraction (r = 0.51) and negatively with oxygen uptake capacity (r = -0.49). Patients with increased LDL-cholesterol levels also showed increased plasma catecholamine levels (r = 0.49 and r = 0.43). Low aerobic capacity (oxygen uptake capacity), high LDL-cholesterol levels and plasma catecholamine concentrations indicate an increased induced platelet sensitivity in vitro.

Adult↗
PubMed1984

[Is the alpha adrenergic receptor density increased in intact thrombocytes in non-isometric trained athletes?].

Alpha-adrenoreceptors were determined as an equivalent to 3H-dihydroergocryptine (DHE) specifically bound on intact thrombocytes in five untrained volunteers (I), eight non-staticly trained sportsmen (II), and eight intensively staticly trained athletes (III). Bmax was 933 +/- 363 (I), 982 +/- 373 (II), and 1796 +/- 539 fmol DHE X 10(-9) thrombocytes (III). KD was 1.28 +/- 0.49 (I), 2.94 +/- 1.12 (II), and 3.58 +/- 1.07 nmol X l-1 (III). The number of binding sites per cell amounted to 561 +/- 202 (I), 589 +/- 224 (II), and 1078 +/- 323 (III). The thrombocytes of the staticly trained athletes showed a significantly higher number of binding sites and a slightly higher affinity (KD) than the other groups (p less than 0.01). However, a wide range of overlapping has to be considered. The biologic significance of these results and their transferability to other organs are open at present. It is the question whether an altered adrenoreceptor density may be one factor of a higher prevalence of hypertension in staticly trained athletes on which our research group has reported recently.

Blood Platelets↗
PubMed1984

Amino acid, ammonia and neurotransmitter concentrations in hepatic encephalopathy: serial analysis in plasma and cerebrospinal fluid during treatment with an adapted amino acid solution.

We evaluated changes of advanced liver disease and hepatic encephalopathy on the concentrations of amino acids (AA) and ammonia in plasma and cerebrospinal fluid (CSF) and of the neurotransmitters norepinephrine, dopamine and 5-hydroxytryptamine (5-HT) as well as the 5-hydroxyindole acetic acid (5-HIAA) in CSF before and at the end of a 3-day period of treatment with infusions enriched with branched chain amino acids (BCAA). The subjects studied were 13 patients with alcoholic cirrhosis and hepatic encephalopathy stages 1-3 (n = 8) and stage 4 (n = 5). The patients in coma stages 1-3 recovered during the treatment (survivors), those in coma stage 4 died before the study period was finished (non-survivors). The data emerging from this study show: Alterations of AA concentrations are much more pronounced in the CSF than in the plasma. In the case of tryptophan the alterations in plasma and CSF were inverse. Before the treatment the CSF-plasma ratios of the concentrations of BCAA and aromatic amino acids (AAA) are increased reflecting an activated transport of both the BCAA and AAA through the blood-brain barrier. High dose BCAA nearly normalized CSF concentrations and CSF-plasma ratios of AAA assuming that the treatment brought about an effective competition of cerebral uptake between BCAA and AAA. The CSF concentrations of ammonia and glutamine decreased significantly during treatment while the plasma concentrations changed only moderately. As to the neurotransmitters, only the concentrations of 5-HT and its metabolite 5-HIAA correlated with the clinical picture and with the concentration of their precursor AA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Facilitation of ventricular tachycardia induction with abrupt changes in ventricular cycle length.

The effect of abrupt short-to-long changes in cycle length (CL) on the postulated reentrant circuit of ventricular tachycardia (VT) was evaluated. This was performed using single and double ventricular extrastimuli in a group of 21 patients clinically suspected of having VT in whom VT could not be induced at comparable or shorter constant CLs. A second group of 10 patients without suspected VT was similarly studied. Compared with constant CLs of equal or shorter duration preceding the single or double ventricular extrastimuli, abrupt short-to-long CL changes resulted in (1) initiation of sustained VT in 13 of 21 patients in whom VT could not be induced at constant CLs despite the use of shorter S1S3 by 66 +/- 17 ms; (2) increased incidence of initiation of sustained VT after the V3 phenomenon resulting from macroreentry within the His-Purkinje system (Re-HPS); (3) a small but higher incidence of sustained VT due to sustained Re-HPS; and (4) no induction of sustained or nonsustained VT with either method in the second group of patients. These results provide additional support for reentry as the basis for sustained ventricular tachyarrhythmias. Abrupt short-to-long CL changes may be effective for initiating sustained VT in patients at risk for these arrhythmias.

Adult↗
PubMed1984

Plasma catecholamines, beta-adrenergic receptors, and isoproterenol sensitivity in endurance trained and non-endurance trained volunteers.

Six male non-endurance trained subjects (S) and six marathon runners (M) underwent graded treadmill exercise (T) and isoproterenol stimulation (I; 2 and 4 microgram X min-1). beta-adrenergic receptor density was additionally determined as the amount of 3H-Dihydroalprenolol (DHA) specifically bound on intact polymorphonuclear leucocytes. Heart rate, VO2 uptake, lactate, plasma noradrenaline, and adrenaline were estimated during T. Heart rate, stroke volume, cardiac output, as well as lactate, glucose, free fatty acids (FFA), and glycerol levels in the blood were determined during I. M showed the known training-dependent responses during T, such as lower heart rates, lactate levels, and plasma catecholamines at identical work loads, as well as higher VO2 max than S. I-induced cardiac output increase was quite similar in both groups. Stroke volume, however, increased significantly in M and stayed constant in S. Lactate decreased (S), glucose increased significantly (M), glycerol increased similarly in both groups, FFA rise was less marked in S. I-induced stroke volume response (I) may be indicative of a more economic regulation of heart work in M than S. Lactate decrease and less marked FFA increase, as observed in S, may be the result of a somewhat higher cardiac energy demand, dependent on less economic heart work. Higher DHA-binding as observed in M, as well as stroke volume response and glucose increase, may be indicators of a training-dependent rise in sensitivity to catecholamines. The unsolved question is, however, to what extent beta-receptor responses in intact blood cells are significant for receptor behavior in other organs.

Adult↗
PubMed1984

Functional characteristics of retrograde conduction in a pacing model of "endless loop tachycardia".

A pacing model was designed that stimulated "endless loop tachycardia," a complication found in the new generation of DDD (atrioventricular [AV] universal) pacemakers. The functional characteristics of the train of ventricular impulses simulating endless loop tachycardia were studied during both AV sequential pacing and basic ventricular drive. AV sequential pacing, by causing a decrease in ventriculoatrial (VA) conduction time of the first beat of the endless loop tachycardia, was associated with a decrease in the cycle length at which VA block occurred in 9 of 12 patients. The site of block was the His-Purkinje system in 4 of these 12 patients and the AV node in the remaining 8. At a cycle length with 1:1 VA conduction, a steady state VA conduction time was achieved in 2 to 4 beats (VA conduction time accommodation). The pattern of such accommodation depended on the site (His-Purkinje system versus AV node) of the maximal conduction delay. The steady state VA conduction time itself was altered with AV sequential pacing in patients showing His-Purkinje system delay, but not in patients with AV nodal delay. The results suggest that in most patients, the cycle length of VA block and the longest steady state VA conduction time will depend on the retrograde conduction time of the first beat of the tachycardia. In addition, pharmacologic measures to prevent or terminate endless loop tachycardia will have to take into account the fact that both the His-Purkinje system and the AV node can be the site of initial block.

Atrioventricular Node↗
PubMed1984

Effect of amiodarone on conduction and refractoriness of the His-Purkinje system in the human heart.

Although the antiarrhythmic aspect of amiodarone has been extensively studied, its effects on His-Purkinje system conduction and refractoriness have not been systematically investigated in human beings. In 24 patients, anterograde His-Purkinje system conduction (HV intervals) and variables of His-Purkinje system refractoriness using the ventricular extrastimulus (V2) technique were analyzed before and after long-term therapy with amiodarone. The mean duration of amiodarone therapy at the time of repeat study was 16.2 +/- 7.7 weeks (range 11 to 42). The anterograde His-Purkinje system conduction time (HV interval) measured 49.6 +/- 9.5 ms (range 40 to 80) before and 60.6 +/- 10.7 ms (range 45 to 90) after amiodarone (p less than 0.005). During retrograde refractory period studies, the longest V1V2 interval at which a retrograde His bundle potential (H2) emerged from the V2 electrogram (relative refractory period of the His-Purkinje system) was consistently longer after amiodarone as compared with the control period (376.4 +/- 46.6 versus 318.8 +/- 33.1 ms, p less than 0.005). Similarly, the shortest and longest His-Purkinje system conduction times ( V2H2 interval) at comparable V1V2 intervals were uniformly and significantly prolonged after administration of the drug. Amiodarone also abolished macroreentry in the His-Purkinje system in six of the nine patients who showed such reentry during the control period. The effective refractory period of the ventricular myocardium was also increased from a mean of 227.1 +/- 13.9 to 259.2 +/- 20.2 ms (p less than 0.005) in this series of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Age- and exercise-related sympathetic activity in untrained volunteers, trained athletes and patients with impaired left-ventricular contractility.

To study the influence of training, aging and left-ventricular contractility on the sympathetic nervous system, responses of plasma catecholamines and density of adrenoreceptors on intact blood cells were evaluated in 21 dynamically trained subjects, 8 statically trained weight lifters, 15 healthy young and 15 old control subjects, and 55 post-infarction patients. Plasma catecholamines are indicators of the overall sympathetic tone, while the density of adrenoreceptors is a cellular indicator of the sensitivity to catecholamines. Static and dynamic training result in lower catecholamine response at identical work loads during incremental ergometric tests. Higher density of beta 2 receptors on intact leucocytes and higher sensitivity to isoproterenol are seen in the dynamically trained test subjects. Higher density of alpha 2 receptors on intact thrombocytes is found in the weight lifters. Despite the training-dependent control of the sympathetic activity bradycardia occurs only in endurance-trained subjects, indicating an additionally increased vagal control. The exercise-related tachycardia of the weight lifters, on the other hand, points to an insufficient vagal control of the cardiac sinus rate. Decrease of physical fitness, as related to aging, a deficit in physical training and impaired left-ventricular contractility are connected with a higher sympathetic activity at identical work loads and a lower beta-receptor density on intact blood cells and, in cardiac patients, on myocardial cells as well (Bristow et al. 1982). Changes in the sympathetic system may amplify the age- and disease-dependent decrease of the cardiac function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗