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Biomedical subjects

M Lehmann

Publications and source records attributed to M Lehmann.

At least 253 records · Page 14Linked to original sources
PubMed1988

Ecdysteroid receptors of the blowfly Calliphora vicina: partial purification and characterization of ecdysteroid binding.

A macromolecule with high affinity for the ecdysteroid analogue ponasterone A was isolated from nuclei of larvae of the blowfly Calliphora vicina. The ecdysteroid-binding molecule revealed characteristics of the moulting hormone receptor. It was sensitive towards protease but not towards nucleases. The nuclear protein had a limited binding capacity (0.2 pmol ponasterone A/mg protein), showed hormone analogue specificity and high affinity for ecdysteroids. Enzyme activities were present in the nuclear extract that metabolized ecdysteroids and thereby interfered with the binding assay. After their removal by DEAE-cellulose chromatography the ecdysteroid receptor preparation was stable at 20 degrees C for hours. This allowed a reliable determination of dissociation constants at equilibrium conditions. The hormone receptor complex had a KD of 1 nM, 30 nM, and 2000 nM with ponasterone A, 20-hydroxyecdysone, and ecdysone, respectively. The apparent molecular mass of the ecdysteroid receptor was 105,000 as determined by gel filtration.

Animals↗
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↗
PubMed1988

Sympatho-vagal changes induced by physical training in cardiac patients.

Heart-rate and blood pressure increase correlate proportionally to myocardial oxygen consumption. A 100% increase in stroke volume, however, is related to only a 10% increase in myocardial oxygen consumption (Sarnoff et al., 1958). An economical cardiac adaptation to exercise which results in a saving of myocardial oxygen requirements (Heiss et al., 1979) is therefore based on an increased stroke volume in relation to a moderate heart-rate response and a decrease in circulatory resistance, respectively. Such a cardiac adaptation to exercise can be observed in endurance-trained subjects, dependent on a reduction in sympathetic activity and an increase in vagal tone. This favourable change in sympatho-vagal tone can be expected in all subjects undergoing physical training (endurance training) and in part also in some cardiac patients subsequent to physical therapy. However, only an approximate normalization of impaired autonomic function can be observed as a result of physical therapy in patients with significantly reduced exercise capacity, and this in less than 50% of the investigated cardiac patients. In cardiac patients with normal exercise capacity and approximately normal or slightly decreased left ventricular function, a favourable improvement in autonomic function and an increase in exercise capacity can be expected in about 50% of cases. The possibility or the extent to which the prognosis of cardiac disease is affected by the change in autonomic function remains unclear, however.

Coronary Disease↗
PubMed1988

[Follow-up study of 48 athletes with stage I hypertension with and without pharmacotherapy].

We found in an earlier investigation that the frequency of hypertension is considerably lower among male athletes than in a random sample of the general population. The cases of hypertension in younger athletes are primarily hypertension stage I (WHO). We followed up on the question of the course of hypertension stage I and the possibility of spontaneous remission. For this, we observed 28 nonmedicated patients with hypertension stage I for 4.2 +/- 2.3 years, 20 patients undergoing drug therapy for 2.5 +/- 1.3 years, and 12 healthy athletes for 4.2 +/- 2.2 years. Under drug therapy, as expected, there was a normalization of both basic and exercise blood pressures. Fifty percent of patients without drug therapy showed remission of the elevated basic and exercise pressures after 2 to 3 years; 50% had an unchanged high pressure or deterioration. The transition of hypertension WHO stage I to stage II with regard to left ventricular hypertrophy could be ruled out echocardiographically in patients with a favorable course (remission). However, there was a tendency in this direction among patients with the least favorable course.

Adrenergic beta-Antagonists↗
PubMed1988

[Behavior of heart rate, blood pressure, lactate, glucose, noradrenaline and adrenaline level in coronary heart disease patients in the course of light swimming stress].

In previous investigations, we have been able to demonstrate that healthy individuals and CHD patients with normal exercise capacity experience changes in cardiovascular parameters, metabolism and sympathetic activity during light swimming exercise, changes which are not observed in seated bicycle ergometry at an exercise level of less than 2 W/kg-1. We have now examined 12 post-infarction patients (54.3 +/- 6 years) with limited exercise capacity (1.2 +/- 0.3 W/kg-1), who have been participating in physical therapy for 29 months (median time) under continuous medication. The examination comprised incremental seated bicycle ergometry and, approximately 60 min later, light swimming (2 to 3 x 2 min; speed v = 0.33 +/- 0.02 m.s-1; T = 28 degrees C). The changes in heart rate, blood pressure, lactate, glucose, adrenaline and noradrenaline levels during the swimming exercise were equivalent in mean value to ergometry at the 100 W level. Three patients had to discontinue swimming before the scheduled time, due to considerable arrhythmias. Three other patients stopped swimming because of subjective overexertion. The exercise reaction was less favorable among those unaccustomed to swimming than among regular swimmers.

Adult↗
PubMed1988

[Differential diagnosis: physiologic-pathologic hypertrophy of the heart. A case report].

We report on a 52-year-old asymptomatic patient, whom we have examined regularly since 1981. The principal finding is a marked terminal negativity of the T-wave in the extremities and left precordial chest leads in the electrocardiogram with regression at high exercise levels. The patient engages intensively in sports (running, cross-country skiing, gymnastics). His performance capacity is above normal at 4.5 (1981) and 3.8 watts/kg body weight (1988). The echographically determined left ventricular muscle mass (LVM) increased from 2.1-2.3 g/kg body weight to 2.9 g/kg, the end-diastolic thickness of the septum from 9 to 13, and the posterior wall from 8 to 12 mm. In physiological cardiac hypertrophy (athlete's heart), a LVM of 2.9 g/kg is not unusual, whereby the end-diastolic wall thickness does not, exceed 10 to 11 mm and the mass-volume ratio (LVM/end-diastolic ventricular volume) remains constant (about 1.2 g/ml) in contrast to the 1.75 g/ml in our patient. Thermodilution catheter examination of the heart showed a pathological increase in mean pulmonary capillary pressure (26 mm Hg) under exercise as an indication of impaired left-ventricular function. Normal myocardial scintigraphy (resting and exercise) and a lack of symptoms permit the exclusion of relevant coronary heart disease. We diagnosed non-obstructive hypertrophic cardiomyopathy. The problems of differentiating between physiological and pathological cardiac hypertrophies are discussed.

Cardiac Volume↗
PubMed1988

The vascularization of the peripheral nerve of chicken and rat.

The vascular system of the sciatic nerve of chicken and rats was examined by means of the microcorrosion casting technique and freeze-broken specimens. The main epineural vessels form two lateral and interfascicular vascular bundles which anastomose with one another and also with the peri- and endoneural plexuses. On epi- and perineural vessels one can find morphological correlates for regulative means such as sphincters. Even the endoneural vessels depict numerous anastomoses. The proximity of the vessels as well as the great number of anastomoses suggests a considerable compensatory potential with an adaptable perfusion rate in case of a partial breakdown of a plexus.

Animals↗
PubMed1987

Evaluation of long-term oral levodopa therapy in chronic congestive heart failure.

To evaluate the long-term effects of orally administered levodopa, 11 patients with chronic congestive heart failure (NYHA III-IV) were studied during maintenance therapy (30 +/- 1 days) and after withdrawal from levodopa. The daily levodopa dose was 4 g in six patients; because of side effects the levodopa dose was reduced to 2-3 g in the remaining patients. After withdrawal of levodopa, mean pulmonary capillary wedge pressure and mean right atrial pressure increased significantly (from 19 +/- 2 to 24 +/- 3 and from 7 +/- 2 to 9 +/- 2 mmHg, respectively). Effective renal plasma flow was 329 +/- 57 during levodopa therapy and decreased significantly to 252 +/- 27 ml/min after withdrawal of levodopa. The number of ventricular premature contractions and couplets increased during levodopa therapy and decreased again significantly after withdrawal of levodopa. No significant differences between on and off levodopa were observed in resting heart rate, arterial blood pressure, cardiac index, stroke work index, systemic vascular resistance, sodium and water excretion, or creatinine clearance. Seven patients improved on levodopa therapy by one NYHA class; four of these seven patients deteriorated again by one NYHA class after withdrawal of levodopa. Regarding both clinical and hemodynamic changes after withdrawal of levodopa, three patients were classified as responders to long-term levodopa therapy. All three responders received 4 g levodopa per day. Average dopamine plasma level was 5.3 +/- 0.8 ng/ml in the responder group and 2.0 +/- 0.5 ng/ml in the nonresponder group. Long-term administration of oral levodopa is associated with beneficial clinical and hemodynamic response in only a minority of patients with chronic congestive heart failure.

Administration, Oral↗
PubMed1987

[Effect of vitamins and iron on performance and recovery in humans and in sports anemia].

In sports, vitamins along with minerals, particularly iron, and the energy nutrients such as carbohydrates, are considered especially important. Frequently single or multiple vitamins in combination with other active substances such as iron, other minerals or carbohydrates are administered. In sports, vitamins are added to carbohydrate mixtures or electrolytes enriched with vitamins are offered and frequently used. There is no doubt that due to the numerous effects of vitamins, a connection must exist between the vitamin status and athletic performance capability. It can be concluded that vitamin deficiencies have a negative effect on physical and mental performance. The release of energy can only attain its maximum output when the organism has the required substances at its disposal. Iron is of central importance among these active substances, since its presence in haemoglobin is essential for the transport of oxygen and carbon dioxide, makes it possible for myoglobin to function as an oxygen supply depot and guarantees the functioning of internal respiration in the respiratory chain and various key enzymes. Muscle training increases not only the respiratory chain but also several other iron-rich enzymes. This makes even more astonishing the fact that a variety of recently published articles report on iron deficiency among athletes. The effect of the iron deficiency with anaemia (sports anaemia) is manifest in a reduction of aerobic capacity with an increase in lactate acidosis, greater fatigue, loss of appetite, muscular cramps and vasomotor disturbances.

Anemia, Hypochromic↗
PubMed1987

Sensitivity of the physiologically hypertrophied heart to isoproterenol.

Cardiovascular reactions to isoproterenol stimulation (2 and 4 micrograms/min for 12 min each) were evaluated in seven endurance-trained athletes (marathon runners, VO2 max 66.0 +/- 3.7 ml/kg) and seven untrained subjects (VO2 max 54.4 +/- 3.6 ml/kg). At rest and during stimulation, the heart rate, blood pressure as well as one-dimensional (end-diastolic and end-systolic dimensions, shortening fraction) and two-dimensional (end-diastolic and end-systolic volumes, ejection fraction, stroke volume, cardiac output) echocardiographic parameters were determined. The increase in the heart rate of the endurance-trained athletes (28%; 2 micrograms/min) (58%; 4 micrograms/min) was less than in the untrained controls (34%/76%). The blood pressure behaved similarly in both groups. The stroke volume of the endurance-trained subjects rose during stimulation (14%, 4 micrograms/min); the end-diastolic volume remained nearly constant as the end-systolic emptying increased. The stroke volume of the untrained subjects tended to decrease as the end-diastolic and end-systolic volumes were reduced. In absolute terms, the shortening fraction and ejection fraction were identical. Referring to the heart rate, however, they were elevated in the endurance-trained subjects. Hence, under isoproterenol the rise in heart rate was weaker and the increase in ventricular performance seemed to be stronger in the trained subjects compared to the untrained controls. The causes appear to be different regulative effects of the autonomic nervous system on the sinus node and the ventricular myocardium; intrinsic cardiac mechanisms remain to be discussed.

Adult↗
PubMed1987

Central and peripheral inhibition of angiotensin converting enzyme (ACE) in the SHR: correlation with the antihypertensive activity of ACE inhibitors.

A series of five structurally distinct ACE inhibitors were evaluated for their ability to inhibit tissue ACE activity in the SHR after oral administration. In the first series of experiments, the ACE inhibitors captopril, enalapril, pentopril, CGS 14824A and CGS 16617 were given to groups of SHR at doses that produced a 15 to 20 mm Hg reduction in blood pressure within 1 hour. Under these conditions of dose and time, only captopril significantly inhibited brain ACE activity (43%), whereas inhibition of serum ACE activity ranged from 72% to 99% with these agents. Inhibition of aortic ACE activity ranged from 54% to 87%, and lung ACE inhibition varied from 50% to 83%. In the second series of experiments, SHR were administered higher doses of each ACE inhibitor such that these compounds produced peak reductions in blood pressure (-25 mm Hg to -33 mm Hg) within a range of 2 to 6 hours. When tissue ACE activity was measured at the time corresponding to peak reduction in blood pressure, all five ACE inhibitors produced a significant inhibition of brain ACE activity ranging from 21% to 76%. Serum ACE activity was almost completely inhibited by these agents, with the exception of captopril (62% inhibition). The inhibition of aortic ACE activity ranged from 79% to 99%, while the inhibition of lung ACE activity did not increase under these conditions. These data suggest that ACE inhibitors may exert their maximal antihypertensive effects by inhibiting ACE in vascular tissues and brain.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

Physical training, vegetative regulation, and cardiac hypertrophy.

Dynamic physical training leads to functional and structural adaptations in the cardiovascular system. Functional changes, such as bradycardia, occur after only relatively little training and in advance of structural changes. They are the result of elevated parasympathetic tone at rest and reduced sympathetic activity in the submaximal range. Sympathetic activity cannot be correlated only with the plasma catecholamine level because the affinity and density of the beta-receptors and alpha receptors are influenced by training. In humans, endurance training appears to result in an elevation in beta 2-receptors and a decrease in alpha 2 receptors; the results of animal experiments are discrepant. Conformant, however, is the increased responsiveness of the myocardium to isoproterenol with respect to the mechanical response. Independent of this, other changes at the membrane level must be discussed since the intrinsic heart frequency is reduced in athletic individuals following autonomic blockade, even before hypertrophy can be observed. The functional changes remain intact or intensify when cardiac hypertrophy is induced by increased training. The maximum values for training-induced hypertrophy [left ventricular muscle mass (LVM) = 3.5 g/kg] are about 70-80% of the baseline weights (LVM = 2.1 g/kg). The left ventricle is enlarged during end diastole and end systole, the ejection fraction is normal, and the stroke volume is increased. The mass/volume ratio remains constant (LV = 1.2 g/ml), as does the maximum systolic wall stress (196 x 10 dyn/cm). Compared with pathological forms of hypertrophy and to the normal heart, the trained heart is capable of increasing the stroke volume considerably with exercise and maintaining the increase to a high-frequency range.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomegaly↗
PubMed1987

[The interleukin 2 receptor. A review of the literature].

The importance of the receptor ligand system IL 2-receptor and IL 2 for the regulation of the T-cell proliferation was confirmed recently. In this review most important points are discussed as biochemical data, regulation of the expression, monoclonal antibodies, binding behaviour, affinity and activation events. Other activation antigens are also discussed in a short part.

Amino Acid Sequence↗
PubMed1986

[Catecholamine behavior, adrenoreceptor density of intact cells and sensitivity to catecholamines in a patient with orthostatic hypotension].

We evaluated sympathetic nervous system function in a patient with primary orthostatic hypotension. Plasma catecholamine levels--except for dopamine levels--and urinary catecholamine excretion were decreased, alpha-adrenoreceptor responsiveness to noradrenaline and beta-adrenoreceptor responsiveness to isoproterenol were increased according to increased beta-2-adrenoreceptor density on intact polymorphonuclear leukocytes. Alpha-2-adrenoreceptor density on intact platelets and adrenaline-induced platelet aggregation in vitro, however, were unchanged. We evolved a therapeutic regimen with fludrocortisone, propranolol, and dihydroergotamine that allowed the patient to resume nearly a regular degree of mobility.

Aged↗