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Biomedical subjects

M Lehmann

Publications and source records attributed to M Lehmann.

At least 325 records · Page 18Linked to original sources
PubMed1983

Identification of transferrin as the principal plutonium-binding protein in the blood serum and liver cytosol of rats: immunological and chromatographic studies.

An analysis of 239Pu-labelled protein complexes in serum and liver cytosol fractions prepared from rats injected intravenously with 239Pu-citrate indicated that among the possible metal-binding proteins, ferritin, transferrin and metallothionein, 239Pu was bound almost exclusively to transferrin. The method employed for the quantitative determination of 239Pu-transferrin was chromatography on immobilized rabbit anti-rat apo-transferrin. There was no evidence that transferrins from serum and liver cytosol are serologically different. The residual blood content of perfused and non-perfused liver was measured using 51Cr-labelled red blood cells and the amounts of blood-derived 239Pu and 239Pu-transferrin in the liver cytosol were calculated. The results are discussed with respect to the possible role of transferrin in the uptake of Pu into cells.

Animals↗
PubMed1983

Atrioventricular sequential pacing: differential effect on retrograde conduction related to level of impulse collision.

Patients with DDD pacemakers who have intact retrograde conduction are known to be at risk of developing ventricular and "endless loop" tachycardia. To address this problem, a pacing protocol was designed in which V2A2 conduction was assessed in 16 patients during ventricular pacing alone (standard method) and during paced atrioventricular (AV) sequential drive (AV sequential method); the results were then compared. In eight of 16 patients who had intact retrograde conduction with both methods (group 1), the V2A2 intervals were significantly shorter (by 60 to 340 msec) with the AV sequential method. In the remaining eight patients, who demonstrated V2A2 block with the standard method, no V2A2 block occurred with the AV sequential method. In this study, two sets of AV intervals were programmed to produce collision of the two impulses (atrial and ventricular), either in the AV node or the His-Purkinje system (HPS). The site of V2A2 facilitation was related to the site of impulse collision. These results can be explained by earlier excitation by the atrial impulse (of AV node and/or HPS) during AV sequential pacing. However, in some cases it was evident that antegrade propagation of the atrial impulse was responsible for subsequent facilitation. The data suggest that assessment of retrograde conduction in candidates for DDD pacemakers can be made most accurately by the AV sequential method.

Adult↗
PubMed1983

[Two-dimensional stress echocardiography and plasma catecholamine measurements in the evaluation of the physiologically hypertrophied heart].

Two-dimensional stress echocardiography was performed in 8 untrained subjects, 8 long-distance runners, and 8 cyclists. The ergometric investigation was performed with subjects in supine position on a bicycle ergometer with increasing work loads of 50 Watts. At each working level, lactate, norepinephrine, and epinephrine were measured. The long-distance runners and the cyclists had an equal maximum oxygen uptake when tested with treadmill or bicycle ergometer. Absolute and relative heart volumes also showed the same amount of hypertrophy. In spite of this, lactate, catecholamines, and heart rate of the long-distance runners rose earlier during the supine ergometer test. End-diastolic volume and stroke volume in the cyclists increased significantly more (delta EDV = 15%, delta SV = 32%) than in the long-distance runners (delta EDV = 1%, delta SV = 13%) and untrained subjects (delta EDV = 5%, delta SV = 9%). It is assumed that this difference in heart function is caused by diminished sympathetic activity, which is dependent on the aerobic capacity of the working muscles.

Adolescent↗
PubMed1983

[Hemodynamics, plasma catecholamine behavior and beta-adrenergic receptor density in trained and untrained subjects and cardiac insufficiency patients].

Swan-Ganz semifloating balloon-tipped catheters were introduced in 6 endurance-trained subjects, 7 untrained volunteers, 29 patients suffering from coronary heart disease, 8 patients with right heart insufficiency induced by chronic obstructive syndromes, and 8 patients with idiopathic congestive cardiomyopathy. All subjects except the patients with resting cardiac insufficiency performed graded ergometric tests during the catheter investigation. Hemodynamic values, plasma noradrenaline and adrenaline (in all subjects), and beta-adrenergic receptor density on intact polymorphonuclear leucocytes (in 6 endurance-trained subjects, 5 untrained healthy volunteers, and 6 patients with left heart insufficiency) were determined. For all subjects investigated, significant correlations were observed between resting plasma catecholamine levels and resting hemodynamic values, such as stroke volume (r = 0.47, p less than 0.001), cardiac output (r = 0.32, p less than 0.05), heart rate (r = 0.37, p less than 0.01), pulmonary vascular resistance (r = 0.52, p less than 0.001), and total vascular resistance (r = 0.40, p less than 0.01). An inverse relationship existed between the resting catecholamine levels and the performance ability. Catecholamine levels were approximately three- to fourfold higher and the beta-adrenergic receptor density approximately two- to threefold lower in patients with left heart insufficiency than in healthy untrained subjects. The plasma catecholamine levels were lower and the beta-adrenergic receptor density approximately 60% greater in trained subjects. The beta-adrenergic receptor density may be a critical dynamic parameter for the modulation of sympathetic effects.

Adult↗
PubMed1983

[Determination of beta-receptors on intact polymorphonuclear leukocytes in autologous plasma].

The binding of tritium labelled radioligand dihydroalprenolol was investigated on live polymorphonuclear leukocytes of 6 endurance trained (VO2 max. 65.7 +/- 2.0 ml/kg . min), and 9 non-endurance trained subjects (VO2 max. 52.0 +/- 4.0 ml/kg . min). The specific binding of dihydroalprenolol is seen as an indicator of the beta-receptor density. The specific binding of dihydroalprenolol is defined as the difference between the total binding and that amount of dihydroalprenolol that could not be displaced. The leukocytes were reincubated for the binding studies in their autologous plasma. The specific binding of dihydroalprenolol on live polymorphonuclear leukocytes shows a levelling off behaviour at a concentration of approximately 2 nmol/l dihydroalprenolol in trained as well as in untrained subjects. The specific binding amounts to about 85% (0.1 nmol/l dihydroalprenolol) to 51% (2.0 nmol/l dihydroalprenolol) of the total binding. Based on Scatchard analysis, Bmax was determined as 41.2 fmol/10(7) cells (trained subjects) and 21.6 fmol/10(7) cells (untrained subjects). KD is 0.44 nmol/l dihydroalprenolol (untrained subjects), and 0.49 nmol/l dihydroalprenolol (trained subjects). The beta-adrenergic binding sites are approximately 1300 (untrained subjects), and 2500 binding sites/cell (trained subjects). The specific binding of dihydroalprenolol on live polymorphonuclear leukocytes is significantly higher in trained than in untrained subjects. This training dependent change in beta-receptor density may be an indicator of an increased sensitivity to catecholamines.

Alprenolol↗
PubMed1983

The metabolism of radiohafnium in rats and hamsters: a possible analog of plutonium for metabolic studies.

The metabolism of radiohafnium (175Hf + 181Hf) was studied in male Sprague-Dawley rats and Chinese hamsters for periods of up to 168 days. The results were compared with similar data for 239Pu in the same rat strain. In rats and hamsters the radiohafnium organ distribution was skeleton greater than skin greater than muscle greater than liver at about 7 days postinjection. Retention of radiohafnium and plutonium was similar in plasma and liver, as were the retention times observed for other organs: Absorption of radiohafnium from the gastrointestinal tract of rats was less than 0.05%. Biochemical studies showed that the radiohafnium was bound mainly to the iron-transport protein, transferrin, in blood plasma and in the liver cytosol of both the rat and the hamster, as has been observed also for plutonium. The metabolic behavior of radiohafnium mimics, to a large extent, that of plutonium, and it is suggested that radiohafnium can serve as a non-alpha-particle-emitting analog of plutonium for metabolic, biochemical, and selected human investigations.

Animals↗
PubMed1983

[Simultaneous determination of hemodynamics and plasma catecholamines in trained and untrained subjects and patients with contraction disorders of the heart during rest and physical activity].

6 trained (TS) and 7 untrained (US) subjects and 16 patients (P) with left ventricular dysfunction were investigated by means of a Swan-Ganz floating catheter during graded bicycle ergometry in a supine position. 9 P suffered from a myocardial infarction and 10 were known to be hypertensive; 10 suffered from acute coronary insufficiency during exercise. Hemodynamic values, free plasma catecholamines, and heart volume at rest were determined in all cases. The relative heart volume was increased training-dependent in the TS as compared with US and P. In TS stroke volume increased more than in US, whereas in P a heart-rate-dependent adaptation of cardiac output was observed during exercise. In P cardiac output was slightly reduced during exercise and the arteriovenous oxygen difference augmented. Systolic and diastolic pulmonary artery pressure, pulmonary wedge pressure, and peripheral diastolic arterial pressure rose more in P during exercise than in TS and US. TS showed reduced, whereas P showed increased levels of circulating free plasma catecholamines (norepinephrine and epinephrine). Training-dependent changes in hemodynamic values and catecholamine levels were seen as an economic adaptation of the heart to physical stress, and the results in the patients were interpreted as indicating an uneconomic stress adaptation. In patients with disturbed left ventricular function, extracardiac compensatory mechanisms such as enhanced sympathetic activity and increased arteriovenous oxygen difference are necessary for the adaptation to physical stress.

Arrhythmias, Cardiac↗
PubMed1983

[Sensitivity of free and conjugated plasma catecholamines as indicators of left ventricular contraction disorder of the heart].

Hemodynamic parameters were measured (using a Swan-Ganz semifloating balloon-tipped catheter) and free and conjugated catecholamines were assessed radioenzymatically in plasma from the pulmonary artery in 6 patients (5 postinfarction patients, 1 with idiopathic congestive cardiomyopathy; 56 +/- 7 years old) and 6 healthy control subjects (48 +/- 6 years old). The tests were carried out at rest and during bicycle ergometry in the supine position at incremented work loads. Neither at rest nor during exercise was cardiac output in patients and controls significantly different. The mean capillary wedge pressure (PCPm) was elevated above control values in 1 patient at rest and in all patients during exercise. This may be indicative of impaired left ventricular contractility. The mean ergometric exercise level in patients was 100 w, in the control group 187 w. Conjugated plasma catecholamines showed no exercise dependency, and there were no significant differences between patients and controls. Free dopamine comprised less than 5% of the whole dopamine fraction, free noradrenaline and free adrenaline less than 50% of their fractions. A significant exercise dependency was observed in the case of free noradrenaline and adrenaline in patients and controls; at the same exercise levels, the increase in free noradrenaline was significantly higher in patients than in control subjects (p less than 0.01). During exercise, a correlation between free plasma noradrenaline and PCPm (r = 0.60, p less than 0.01) was observed, but not with certainty in patients (r = 0.27). The free plasma noradrenaline may be seen as a sensitive sympathetic indicator of impaired left ventricular contractility.

Adult↗
PubMed1982

[Catecholamine excretion during physical exercise and mental performance].

The basal and exercise-induced heart rates, lactate levels, and the adrenaline and noradrenaline excretions in the urine were measured during different types of physical exercise and mental performance: during moderate physical exercise (Ia, n = 12), submaximal physical exercise (Ib, n = 24), during moderate mental performance (motorway driving, IIa and IIb, n = 25), higher-grade mental performance (driving car-simulator, III, n = 14), and during submaximal mental performance (car racing, IV, n = 48). The moderate physical exercise and moderate mental performance could not be differentiated from one another, or from the higher-grade mental performance using the above-mentioned parameters. Both the submaximal physical exercise and mental performance resulted in a comparable lactate acidosis, heart rate increase, and noradrenaline excretion; the excretion of adrenaline is, however, 3 times higher after submaximal mental performance, than after submaximal physical exercise. The ratio of adrenaline to noradrenaline excretion changed from approximately 1:4 (during physical exercise and moderate mental performance) to approximately 1:2 during submaximal mental performance. The excretion of adrenaline and the ratio of adrenaline to noradrenaline excretion can therefore be used to differentiate between higher-grade mental performance and physical exercise. These parameters can be easily measured without discomfort to the subjects.

Acidosis↗
PubMed1982

[Catecholamines, Cardiocirculatory, and Metabolic Response During Graduated and Continuously Increasing Exercise].

Adrenaline, noradrenaline, glucose, glycerol and the free fatty acids (FFA) in the blood, as well as the heart rate and oxygen intake, were tested in six healthy male volunteers (age: 28 +/- 6 years) during graduated (I) and continuously (II) increasing bicycle ergometric exercise (upright body position). The maximum heart rate, the VO2 max, the maximum lactate and FFA concentration show no significant difference, whereas adrenaline, noradrenaline and the glucose levels are significantly lower, and the glycerol concentration is slightly higher during the maximum test II as compared with test I. At some submaximum exercise levels, the lactate concentration and the heart rate are slightly lower, adrenaline and noradrenaline are significantly lower during test II; the FFA, glycerol and the oxygen intake do not show any significant difference. The duration of exercise was similar in both tests. The total work was about 50% lower in test II, and the maximum performance was slightly higher as compared with test I. These results could have significance for the planning of working conditions, the rehabilitation of patients, and the organisation of training for athletes.

Adult↗
PubMed1982

[Effect of selective and non-selective adrenoceptor blockade during physical work on energy metabolism and sympatho-adrenergic system (author's transl)].

The influence of an acute beta-adrenoceptor blockade on work capacity, oxygen intake, plasma catecholamines, and on energy metabolism was investigated in 9 healthy subjects during graduated ergometric exercise. The examinations were carried out after p.o. administration of 10 mg bunitrolol (BU), methypranol (ME) and placebo in random sequence. The exercise capacity shows a 15% decrease after both beta-blockers; heart rate shows a maximum 20% (BU) and 25% (ME) reduction, respectively. On account of the greater sympathetic intrinsic activity BU does not influence the resting heart rate, in contrast to ME (-8%; p greater than 0.05). BU leads to a decrease of the catecholamine levels (with low sympathetic tone), which is assumed to be caused by an effect on presynaptic receptors. At the same submaximum exercise levels plasma catecholamines are higher after BU and ME than after placebo; however, the maximum levels are not reached with placebo. In relation to the relative oxygen intake, which is inhibited by 4-6% by BU and ME (p greater than 0.05), the differences of the catecholamines decrease in performance caused by beta-blockade. BU does not show an influence on lactate, glucose, free fatty acids, and glycerin and thus represents a more selective blockade. ME inhibits lipolysis (measured by the glycerin level) by a maximum of approx. 50%. Lactate level increase is approx. 30% lower with ME. Glucose level decrease is approx. 20% higher with ME than with placebo.

Adrenergic beta-Antagonists↗