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Biomedical subjects

R Sivertsson

Publications and source records attributed to R Sivertsson.

At least 73 records · Page 4Linked to original sources
PubMed1977

Peripheral haemodynamics in essential hypertension.

Previous studies have indicated the existance of haemodynamically important structural vascular changes in patients and animals with hypertension. Possible pathophysiological implications of these changes are discussed. Two studies dealing with the question of reversibility of the structural changes on long-term blood pressure lowering therapy are described. The results indicate that the changes are partially but not completely reversible.

Adrenergic beta-Antagonists↗
PubMed1977

Oxygen consumption and contractile force during vibrations of cat soleus muscle.

The influence of longitudinal vibrations (50 Hz, 0.4 mm) on isometric twitch force development (4 Hz), blood flow and oxygen consumption was studied in the acutely denervated soleus muscle of the anesthetized cat. It was found that the sinusoidal vibrations reduced the twitch amplitude by 60 per cent whereas oxygen consumption and blood flow were lowered by 15 per cent only. Similar reduction in twitch force was also obtained by lowering the nerve stimulation intensity (4 Hz). This was associated with a diminution in oxygen consumption, the degree of which was linearly related to the attenuation of active force, i.e. the number of activated motor units. The results are in agreement with previous observations as to the mechanical effect of vibrations on active force in smooth and striated muscle. They demonstrate that vibrations prevent the contractile response with maintained high oxygen consumption which adds further support to the hypothesis forwarded by Joyce et al. (1969) that vibrations cause increased rate of detachment of actin-myosin cross-links. In addition it appears possible that vibrations to some extent prevent formation of such cross-links.

Animals↗
PubMed1977

Transurethral stone extraction with a vibrating basket catheter.

In a recent in vitro study, mechanical vibration was shown to facilitate, considerably, both the passing of a basket catheter beyond an artificial ureteral stone as well as the extraction of a calculus. Therefore, a device by which vibration can be transmitted to the basket of a modified stone extractor was developed for clinical application. The basket moves to and fro with an amplitude of 2-4 mm and a frequency of 40-60 Hz. An experimental follow-up study was performed in dogs to find out whether the vibration procedure as such induced injuries to the ureters. Modified stone extractors were passed up bilaterally into the ureters of 11 dogs. Vibration was applied in a standardized manner to one side, the other non-vibrated side served as a control. Postoperatively, 5 dogs were followed during 4-5 weeks with repeated urographies. Specimens of the ureters were examined microscopically when the dogs were sacrificed. No complications which could be ascribed to the vibration procedure as such were observed. The vibration technique was tried also in a pilot study comprising 14 patients with distal ureteral stones; in 9 patients, the stones were successfully extracted. Of the remaining 5 patients in whom the stone extraction failed, 3 passed the stone spontaneously and in 2 ureterolithotomies were performed. No complications were encountered.

Animals↗
PubMed1977

Blood flow in the calves during surgery.

The volume flow in the calves was measured by means of plethysmography in 14 patients who had a cholecystectomy and in 3 patients who had a wedge biopsy of the breast. The blood flow increased 100% during abdominal surgery, while no change was observed during the extraabdominal operation. When the legs were placed horizontally during cholecystectomy clear signs of venous pooling were observed. Venous pooling in the calves increased when pillows were placed in the popliteal fossae to prevent over-stretching of the knees. Elevation of the legs 20 degrees in the hip joints decreased the venous stasis considerably. Except for intermittent effects on the circulation caused by strong retraction of the intestines, no clear-cut change in the degree of venous stasis was observed during the course of a cholecystectomy.

Adult↗
PubMed1976

Evidence for peripheral vascular involvement in mild elevation of blood pressure in man.

1. Cardiac output at rest, intra-arterial blood pressure and hand blood flow at maximal vasodilatation were studied in two groups of 18-25 year-old men: forty-four with mild blood pressure elevation were referred from a military enlistment centre, and twenty-nine normotensive volunteers were mainly recruited from the same enlistment centre. 2. The study group was characterized by a significantly higher cardiac index at rest, and a significantly higher blood flow resistance in the hand at maximal vasodilatation than the control group, indicating the presence of structural modifications in the resistance vessels of patients with mild blood pressure elevation. 3. The tendency to increased vascular resistance in the blood vessels of the hand at maximal vasodilatation was more pronounced in patients with a normal cardiac index than in those with a high index. This suggests inclusion in the study group of tense, anxious individuals with an elevated cardiac index but otherwise normal circulation, but does not exclude the possibility that these patients may develop structural changes later on.

Adolescent↗
PubMed1976

Effects of blood pressure reduction on the structural vascular abnormality in skin and muscle vascular beds in human essential hypertension.

1. Vascular resistance at maximal vasodilatation was examined in two vascular beds in two groups of hypertensive patients and in normotensive control subjects before and during anti-hypertensive therapy in the hypertension groups. 2. In one group of twelve untreated patients with essential hypertension, examined with plethysmography and intra-arterial blood pressure recording, a significantly higher vascular resistance at maximal vasodilatation was found in the hands compared with normotensive control subjects matched for age, sex, weight and height. This indicated a structural vascular abnormality in the patient group. 3. After 5 years of anti-hypertensive therapy in the patient group the difference in vascular resistance between patients and control subjects had decreased significantly, indicating a reversibility of the structural vascular abnormality. 4. Vascular resistance at maximal vasodilatation was examined in the calves of twelve untreated patients with essential hypertension and fourteen normotensive control subjects. Plethysmographic technique and indirect blood pressure recordings were used. A significantly higher vascular resistance was found in patients than in control subjects, indicating a structural vascular abnormality also in this vascular bed. 5. Anti-hypertensive treatment for 6 months in the patient group did not change vascular resistance at maximal dilatation, indicating that the structural vascular abnormality remained. 6. During acute reduction of blood pressure in hypertension by means of trimethaphan infusion, blood pressure and blood flow to the hands were reduced proportionally with no change of vascular resistance at maximal vasodilatation. 7. This indicates that resistance at maximal dilatation was unaffected by the acute reduction of blood pressure, in contrast to the findings after prolonged reduction of blood pressure in this vascular bed.

Blood Flow Velocity↗
PubMed1976

Haemodynamics studies in young men with mild blood pressure elevation.

The cardiac output at rest, and the intra-arterial blood pressure and hand blood flow at maximal vasodilation were determined in two groups of men aged 18-22 years. 44 patients were referred from a military enlistment centre because of mild blood pressure elevation, and 29 normotensive volunteers were mainly recruited from the same enlistment centre. In addition, in a majority of subjects in both groups the auscultatory blood pressure of both parents was determined. The patients were characterized by a significantly higher cardiac index at rest, and a significantly higher vascular resistance in the hand blood vessels at maximal vasodilation than the controls, indicating the presence of structural alterations in the resistance vessels of these subjects with only very mild blood pressure elevation. The tendency to increased vascular resistance in the hand blood vessels at maximal vasodilation was more prominent in patients with a normal cardiac index than in those with a high index. This suggests inclusion in the patient group of tense, anxious individuals with an elevated cardiac index but otherwise normal circulation, but does not exclude the possibility that these patients may develop structural vascular changes later on. The parents' blood pressure was higher in the group of patients, both for patients with a normal and those with a high cardiac index, compared to the parents of the controls.

Adolescent↗
PubMed1976

Vibration-induced changes in vascular tone.

Longitudinal mechanical vibrations in sonic range (10-100 Hz) and of moderate amplitude (50-500) considerably reduce the contractile force of smooth muscle as well as striated muscle. Experiments elucidating the mechanism behind this effect are described. The inhibition of the contractile force is probably due to a direct interference with the action of the contractile proteins. Vibrations are supposed to increase the rate with which the interfilamentary crosslinks are broken. Thereby the number of established crosslinks is reduced and thus the force. Finally a hypothesis concerning the possible role fo this phenomenon in the pathogenesis of vibration induced Raynaud syndrome is forwarded.

Animals↗
PubMed1976

Peripheral arterial insufficiency, effect of physical training on walking tolerance, calf blood flow, and blood flow resistance.

Twenty-three patients with intermittent claudication were submitted to physical training during 4-6 months. Eleven other patients with intermittent claudication served as a control group and were given placebo tablets during the same period. The aim of the investigation was to study the influence of physical training on the blood flow conditions in the calf. The effect of treatment on walking tolerance, on calf blood flow, blood flow resistance, and systolic blood pressure graident between the systemic circulation and the vascular bed in the calf was studied. Half a year after the end of the treatment period the patients were reexamined. The walking tolerance increased in both groups but more in the trained group. The increase in walking tolerance even in the control group was caused by the fact that the control group began to train to some extent. In neither group the maximal calf blood flow changed significantly compared with the pretreatment values. The maximal blood flow showed an increasing trend in the training group after a period fo 4 months compared with the control goupr (2p greater than 0.10). The blood flow resistance at maximal dilatation did not change significantly as compared with the initial values in any of the groups, but there was a significant difference (2p greater than 0.05) between the two groups with a decrease in the training group after 4 months. The changes in maximal calf blood flow and the changes in blood flow resistance at maximal dilatation were not related to the changes in walking tolerance. Half a year after the treatment period the walking tolerance had not decreased and there was no difference between the two groups. The maximal calf blood flow, the blood flow resistance, and the systolic pressure gradient were unchanged in comparison with the pretreatment values and there were no statistically significant differences between the two groups. The small changes in blood flow conditions observed after physical training cannot be the only factor explaining the well known improvement in walking tolerance. However, training may cause a redistribution of the blood flow in the working muscle.

Aged↗
PubMed1975

Vibration-induced inhibition of vascular smooth muscle contraction.

Vascular smooth muscle is known to be exposed to an oscillating strain under physiological and patho-physiological conditions as well as in different occupational and environmental situations. The effect of vibrations of smooth muscle seems to be largly 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 plus or minus 50-500 mum) and frequency of vibration (1-400 Hz) as well as on the prevailing level of active and passive forces. Vibration caused only small and inconsistant reductions of passive force of 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 dilation 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 diameters.

Animals↗