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At least 613 records · Page 34Linked to original sources
PubMed1991

Chronic ACE inhibition reduces intimal hyperplasia in experimental vein grafts.

Intimal hyperplasia is an important factor in the pathophysiology of vein graft failure. Local renin-angiotensin systems recently have been shown to modulate the development of intimal hyperplasia in arteries after intimal injury. The effect of chronic angiotensin-converting enzyme (ACE) inhibition on the development of intimal hyperplasia in experimental vein grafts was examined in this study. Ten New Zealand White rabbits received 10 mg/kg of captopril daily in their drinking water. One week later the right carotid artery was divided and bypassed with the reversed right external jugular vein in these rabbits and in 10 matched controls. Captopril was continued for 28 days after operation, when all the grafts were harvested. Five grafts from each group were perfusion fixed, and the intimal thickness in the proximal, middle, and distal segments was determined. Rings from the remaining grafts (n = 20 in each group) were studied in vitro under isometric tension, and their responses to norepinephrine (NE), histamine (HIST), serotonin (5-HT), angiotensin I (AI), and angiotensin II (AII) was measured. The intimal thickness of the proximal, middle, and distal segments of the captopril-treated grafts were significantly less than controls, being reduced in all segments by approximately 40% (p less than 0.0001). With regard to vasoreactivity, the captopril-treated grafts were hypersensitive to 5-HT (control ED50 5.5 +/- 0.5 X 10(-7) mol/L vs. captopril-treated 1.1 +/- 0.2 X 10(-6) mol/L; p less than 0.005) although the maximal response was significantly reduced (control 1.6 +/- 0.3 g vs. captopril-treated 0.8 +/- 0.1 g; p less than 0.05). There were no differences in sensitivity between control and captopril-treated rings with respect to NE, HIST, AI, or AII. Four of the ten captopril-treated segments, however, failed to respond to AI, and the maximal active tension of the responders was significantly reduced (control 0.47 +/- 0.06 g vs. 0.20 +/- 0.05 g; p less than 0.02). These results suggest that ACE is involved in the modulation of vein graft intimal hyperplasia, and that ACE inhibitors may have therapeutic applications in patients undergoing vein bypass procedures.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1994

Neurally mediated syncope with an update on indications and usefulness of head-upright tilt table testing and pharmacologic therapy.

Neurally mediated episodes of hypotension and bradycardia (neurocardiogenic syncope) are a common cause of recurrent syncope. Clinically, these episodes may present as an isolated event with an identifiable stimulus, or manifest as a syndrome of recurrent idiopathic syncopal events. The technique of head-upright tilt table testing has emerged as a safe and effective modality to identify individuals with this disorder. The use of isoproterenol as an adjunct to tilt table testing is widely employed although controversial. Whereas the mechanism of neurally mediated syncope is incompletely understood, effective therapies are available. Multiple pharmacologic agents, either alone or in combination, have proven effective in preventing recurrent episodes. The role of cardiac pacing as therapy for a subgroup of patients who manifest severe bradycardia or asystole remains controversial as well. Additional study is necessary to further define the mechanism of neurally mediated syncope, provide new therapeutic strategies, and perhaps provide alternative diagnostic techniques.

Bradycardia↗
PubMed2002

Relationship between muscle sympathetic nerve activity and large artery mechanical vessel wall properties in renal transplant patients.

OBJECTIVES: Renal transplant recipients (RTX) show a major impairment of large artery elastic wall properties. Sympathetic overactivity present in patients with renal disease has been shown to alter large artery elasticity; however, in RTX, this issue has not been addressed. The present study therefore investigated a possible relationship between sympathetic activity and large artery distensibility in RTX. METHODS: In 32 patients treated with calcineurin inhibitors (RTX-CI, cyclosporine n = 16, tacrolimus n = 16) mean arterial pressure (MAP, automatic sphygmomanometer), muscle sympathetic nerve activity (MSNA, microneurography) and distensibility coefficients of the brachial and carotid arteries (pulsed Doppler) were measured. Sixteen healthy volunteers (CTR), six patients with calcinneurin inhibitor-free immunosuppression (RTX-AZA) and 12 transplant patients after native kidney nephrectomy (RTX-NC) served as control groups. RESULTS: RTX-CI significantly increased MSNA compared to CTR (36 +/- 3 versus 16 +/- 2 bursts/min, P < 0.05, mean +/- SEM). Both brachial and carotid artery distensibility were decreased in RTX-CI compared to CTR (7 +/- 1 versus 13 +/- 1 +/- 10(-3) /kPa and 17 +/- 1 versus 25 +/- 2 x 10(-3) /kPa, respectively, both P < 0.05). In RTX-CI, a significant inverse correlation between brachial, but not carotid artery distensibility and MSNA (r = -0.46, P < 0.01, r = -0.12, not significant, respectively) was found. Correlation between brachial artery distensibility and MSNA remained statistically significant on separate analysis of cyclosporine- or tacrolimus-treated RTX and after correction for arterial diameter, blood pressure, graft function, age and sex by stepwise multiple regression analysis. Results in RTX-AZA were similar to those in RTX-CI. In contrast, in RTX-NC with MSNA not significantly different from CON (16.6 +/- 2.0 bursts/min), brachial artery distensibility was significantly higher compared to RTX-CI and RTX-AZA (14.2 +/- 2.0 x 10(-3) /kPa, P < 0.05, respectively). CONCLUSIONS: Increased sympathetic nerve activity in renal transplant patients is related to decreased distensibility of the muscular type brachial artery, but not the elastic type carotid artery.

Adult↗
PubMed1979

Vasovagal syncope in aircrew. Psychosocial aspects.

Twenty-four aircrew members with the diagnosis of vasovagal syncope were compared to 26 controls on variables of personality characteristics, psychosocial antecedents to the onset of their conditions, and hyperventilation experience. The syncope group was found to be younger, slightly less adaptable, and to have significantly more negative feelings about their work. The authors argue that syncope in aircrew should be considered from a psychosocial perspective as well as from a medical-neurological perspective.

Adaptation, Psychological↗
PubMed1983

The effect of bilateral adrenal demedullation on vascular reactivity and blood pressure in spontaneously hypertensive rats.

Bilateral adrenal demedullation of juvenile spontaneously hypertensive rats attenuated, but did not prevent, the development of hypertension. Neither did it affect the subsequent vascular reactivity to phenylephrine though it significantly reduced the vascular effects of sympathetic nerve stimulation. Demedullation of adult spontaneously hypertensive rats did not alter blood pressure, but did attenuate the pressor responses to both alpha-adrenoceptor agonists and sympathetic nerve stimulation. In acutely demedullated adult rats, vascular reactivity to sympathetic nerve stimulation, but not to exogenous amines, could be restored by slow i.v. infusion of adrenaline in a dose-dependent manner. The results support a possible facilitatory role for adrenaline in sympathetic neurotransmitter release, both during the development of genetic hypertension and in vascular responses to sympathetic nerve stimulation.

Adrenal Medulla↗
PubMed1967

The innervation of sheep mesenteric veins.

1. An isolated preparation of sheep mesenteric vein is described from which contractions of the longitudinal smooth muscle of the adventitia have been recorded in response to stimulation of intramural and periarterial nerves.2. The preparation did not respond to single stimuli but the relation between amplitude of response and frequency of stimulation was characteristic of that described for other smooth muscles innervated by sympathetic nerves.3. Responses were blocked by tetrodotoxin, guanethidine, and by a number of alpha-receptor blocking drugs. Responses to peri-arterial stimulation were unaffected by hexamethonium. It was concluded that the longitudinal smooth muscle is supplied with post-ganglionic noradrenergic motor nerves and the presence of such fibres in the adventitia was confirmed by fluorescence microscopy.4. Acetylcholine also caused contractions. Although a direct excitatory action on the smooth muscle could not be excluded, results suggest that acetylcholine may release noradrenaline from the axons of the sympathetic ground plexus.

Acetylcholine↗
PubMed1989

Direct evidence of active sympathetic vasodilatation in the skin of the human foot.

1. During operative aorto-femoral vascular reconstructions on sixteen patients, the sympathetic chain was stimulated electrically between the L2 and L4 ganglia while blood flow was monitored by laser doppler flowmeters from the skin on the sole of the foot and the ankle and by an electromagnetic flowmeter from the deep femoral artery. Epidural anaesthesia to at least the T6 level was used which excluded reflex effects. 2. Stimulation (10 Hz) at 1-12 mA current strengths for 30 s evoked both reductions and increases of blood flow in glabrous and hairy skin. Initial short-lasting flow increases (durations 9-19 s) followed by sustained decreases were common: sometimes there were sustained flow increases at low and decreases at high current strengths. 3. In the deep femoral artery (supplying predominantly muscle) only flow reductions were evoked. 4. The results provide evidence for sympathetically mediated vasodilatation in the skin of the human foot whereas leg muscles may be supplied by vasoconstrictor nerves only.

Aged↗