摘要:

In order to evaluate pressure-volume characteristics of foot veins in patients with venous insufficiency compared with a control group, the foot-volumetric method was utilized, combined with intravenous pressure measurements. Calculations of compliance and elastance were performed within a fixed pressure interval, where the veins were filled or almost filled. The investigation demonstrates a lower compliance and a higher elastance in the varicose veins compared with the control cases. This is contrary to most previous investigations, in which the veins have not been fully distended, as the measurements were performed in the lying position with rather low venous pressure. Changes of compliance and elastance were most marked in cases with advanced venous disease and skin changes of the ankle region. The observed changes of a ‘greater stiffness’ of the foot-vascular system can be explained by fibrotic or phlebosclerotic changes. In addition to the observations of slightly altered elasticity factors, we observed volume changes after exercise which seem to be related to capillary filtrat

ISSN:1018-1172    

DOI:10.1159/000158034

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Intraarterial infusions of norepinephrine and dopamine markedly attenuated the mesenteric vasoconstrictor response to periarterial nerve stimulation in anesthetized cats, but did not attenuate the response to intravenous noiepinephrine. The degree of attenuation was independent of stimulation voltage, but inversely related to frequency. The results are compatible with previous in vitro evidence that NE and DA decrease adrenergic transmitter release during nerve stimulation.

ISSN:1018-1172    

DOI:10.1159/000158035

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Mechanical activity of the isolated portal vein and thoracic aorta of the guinea-pig was recorded and the effects of verapamil and D 600 (methoxy-verapamü) on the dose-response curves to noradrenaline were measured. Extracellular electrical activity in portal vein was also sometimes recorded. Two calcium activation mechanisms could be differentiated: a ‘spike activation mechanism’ (SAM) inhibited by verapamil and D 600, and a ‘spike-free activation mechanism’ (SFAM) resistant to these antagonists in their specific concentration range (up to 10–5 mol/l). In portal vein, both mechanisms were similarly dependent on extracellular calcium, indicating a D 600-resistant system for transmembrane calcium fluxes. The response of portal vein to increased potassium concentration was also tested. Species differences and differences in the specificity of various calcium antagonistic drugs complicate the picture of calcium antagonism in vascular smo

ISSN:1018-1172    

DOI:10.1159/000158036

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Vascular smooth muscle is known to be exposed to an oscillating strain under physiological and pathophysiological conditions as well as in different occupational and environmental situations. The effect of vibrations on smooth muscle seems to be largely unknown. In the present experiments on isolated preparations of the rat portal vein and the rabbit thoracic aorta, imposed sinusoidal changes in length were found to cause prompt reduction in active force, the extent of which was dependent on amplitude (1–10% of tissue length, peak to peak, i.e. approximately ± 50–500 µm) and frequency of vibration (1–400 Hz) as well as on the prevailing level of active and passive forces. Vibrations caused only small and inconsistant reductions of passive force of the vascular smooth muscle. The results are in accordance with the hypothesis that vibrations exert a direct action on the contractile process by causing an increased rate of detachment of actin-myosin cross-links. It is suggested that, in vivo, vibrations may affect the diameter of conduit arteries locally in the case of turbulent blood flow as seen in post-stenotic dilatation and arterio-venous anastomosis. Possibly, even the normal pulse pressure oscillations may sometimes tend to inhibit the smooth muscle activity in such arteries and thereby influence their di

ISSN:1018-1172    

DOI:10.1159/000158037

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

5-Hydroxytryptamine (5-HT), norepinephrine (NE), histamine (H) and potassium (K+ K+ 5-HT, K+ NE. Lysergic acid diethylamide (LSD) antagonizes the actions of 5-HT in a manner which progresses from surmountability to unsurmountability of the blockade depending on the concentration of LSD. The blockade exerted by LSD is reversed by washing. Phentolamine and diphenhydramine competitively antagonize the actions of NE and H, respectively. The potency of phentolamine and diphenhydramine in the cerebral arteries of the goat is similar to that determined in different tissues obtained from a variety of animal species. It is concluded that the cerebral arteries of the goat possess receptors for biogenic amines, the most effective of which is 5-HT; receptors for vasoactive peptides are ill defined.

ISSN:1018-1172    

DOI:10.1159/000158038

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effects of ajmaline on vascular smooth muscle were studied using helical aortic strips and portal veins of male rats. This report is based on the results of 104 mechanical experiments. In 30 additional experiments electrical activity was recorded simultaneously at different points of the preparation using extracellular methods (liquid paraffine or pressure electrodes technique). Ajmaline induces relaxation of aortic helical strips (activated by 2.0 µg/l norepinephrine) to 75% of initial tension in a dose of 0.6 mg/l, to 50% by 2.0 mg/l, and to 25% by 4–5 mg/l. The relaxation slope is shifted to the right by increasing the [Ca++]o from 2.0 to 4.0 mM, by increasing the initial norepinephrine concentration to 4.0–10 µg/l, or by KC1 depolarization, [K+]o ranging from 15 to 60 mM.The relaxing effect of ajmaline on aortic strips can partly be attributed to a change in electrical activity with a dose-dependent conduction impairment or block and, at high concentrations, also a decrease in the frequency of pacemaker excitations. Experiments on aortic strips in K+ contracture show relaxation independent of changes in phasic electrical events. Ajmaline ranging from 0.2 to 80–100 mg/l causes on the portal vein a marked increase in amplitude and a small decrease in frequency of rhythmical contractions. Integrated isometric force reaches 300% of initial values. The increasing amplitude of contractions is related to a prolongation of excitation trains, while the frequency and amplitude of the individual spike are reduced.Our results suggest that the effects of ajmaline on the mechanical and electrical activity of vascular smooth muscle may be partly related to a reduction in Ca++ and probably Na+ cond

ISSN:1018-1172    

DOI:10.1159/000158039

出版商:S. Karger AG    

年代:1975

数据来源: Karger