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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cardiovascular responses to cold stress were investigated in hypertensive patients. There were few differences in the changes under cold stress of the serum catecholamine concentration between the juvenile group and middle-aged group. In the juvenile group, a remarkable increase in TPR was observed under cold stress, suggesting that the vascular reactivity is increased and at the same time the cardiac response to inotropic action was increased under cold stress. On the contrary, in the middle-aged group, there was less increase in TPR under cold stress and no increase in inotropic action was observed. From such results, hyperreactivity to stress in the cardiovascular system is thought to be an important factor in the pathogenesis of essential hypertension. Such cardiovascular responses are seen more easily in juvenile hypertension or initial stage of essential hypertension. In the hypertensive patients after middle-age, organic changes will develop by the repeated pressure load to the cardiovascular system caused by various stimulations and the reactivity of cardiovascular system to stress becomes less manifest.
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PMID:Stress as a causative factor of essential hypertension and its influence on the cardiovascular system. 115 88

1. In 7 patients with hypertension, aldosteronism, and low plasma renin (6 patients with a solitary adrenal adenoma, 1 patient with bilateral adrenal hyperplasia) circulatory reflexes (Valsalva's maneuver, head-up tilt and cold pressure test) were examined. Furthermore, the reactivity to the pressor action of tyramine and norepinephrine was determined. For comparison 10 patients with essential hypertension were studied. 2. In 4 of the 7 patients with primary aldosteronism no overshoot following Valsalva's maneuver could be observed. Compared to the patients with essential hypertension the mean overshoot in the patients with primary aldosteronism was significantly reduced. The decrease in blood pressure during head-up tilt was significantly more pronounced in the patients with primary aldosteronism. However, both groups did not differ in their reaction to the cold pressure test. In the patients with primary aldosteronism responsiveness to tyramine was significantly reduced compared to the patients with essential hypertension. No significant difference was observed in the reactivity to norepinephrine between both groups studied. 3. The results point towards a disturbance of the sympathetic nervous system in patients with primary aldosteronism.
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PMID:[Circulatory reflexes in primary aldosteronism (author's transl)]. 121 78

Previous investigations have suggested that significant hypotension during hemodialysis may result from abnormalities of sympathetic nervous system activity. To further evaluate these phenomena, plasma dopamine beta-hydroxylase (D beta H) and cold pressor test (proposed indexes of efferent sympathetic nervous system activity) and amyl nitrite inhalation (an index of the entire baroreceptor reflex arc) were studied in two groups of patients: group I, patients exhibiting a mean arterial pressure decrease to less than 70 mm Hg during less than 10% of dialyses; group II (hemodialysis hypotension), patients with a mean arterial pressure decrease to less than 70 mm Hg during more than 90% of dialyses. The groups were similar with respect to plasma renin activity, renin response to ultrafiltration, age, duration of dialysis, nerve conduction velocity, plasma protein concentration, hematocrit, dialysis weight change, resting heart rate, sex, race, blood pressure and heart rate response to cold pressor test, and 125I-albumin plasma volume. Supine mean arterial pressure was higher in patients with hemodialysis hypotension than in patients without hemodialysis hypotension (group I) both before and after dialysis. Plasma D beta H activity was significantly higher in patients with hemodialysis hypotension (group II) than in group I both before and after dialysis. Amyl nitrite inhalation, expressed as change in delta R-R interval/mean arterial pressure decrease, was less in hemodialysis hypotension patients. These results suggest that hemodialysis hypotension may result from a lesion in the baroreceptors, cardiopulmonary receptors, or visceral afferent nerves. Furthermore, elevated mean arterial pressure in patients with hemodialysis hypotension may be neurogenic in origin, as reflected by plasma D beta H activity, and appears similar to the hypertension that follows baroreceptor deafferentation of experimental animals.
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PMID:Adrenergic regulation of blood pressure in chronic renal failure. 126 65

Elevated blood pressure in psychophysiological studies of borderline hypertension is frequently attributed to the effects of increased sympathetic tone, and with few exceptions, the potential parasympathetic contributions have not been considered. Furthermore, of the investigations that have addressed vagal influences upon blood pressure, most have employed invasive pharmacological assessment of parasympathetic tone. In this study, cardiac parasympathetic and beta-adrenergic influences in borderline hypertension were evaluated noninvasively employing respiratory sinus arrhythmia as a vagal index and preejection period as a sympathetic index of cardiac functioning. Subjects were 30 borderline hypertensive and 23 normotensive males (age range, 24-45 years). The ECG, blood pressure, impedance cardiography, and respiration were measured during two baselines (initial and post-task), a memory-comparison reaction time task, the cold pressor, and CO2-rebreathing. Results indicated tonic differences between groups in all cardiovascular variables across tasks, with the exception of pre-ejection period, which showed no group effects at all. Hypertensives additionally manifested somewhat heightened systolic blood pressure reactivity and attenuated cardiac parasympathetic responsivity to specific tasks. Our findings provide no support for an exaggerated cardiac beta-adrenergic tonic level or reactivity in borderline hypertensives. On the other hand, the consistently lower magnitude of respiratory sinus arrhythmia in our hypertensives suggests that reduced parasympathetic control may be involved in the pathophysiology of hypertension.
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PMID:Cardiac autonomic mechanisms associated with borderline hypertension under varying behavioral demands: evidence for attenuated parasympathetic tone but not for enhanced beta-adrenergic activity. 133 72

1. The role of the presynaptic adrenoceptor subtypes in man was investigated based on observation of the changes in blood pressure (delta BP) and plasma noradrenaline concentration (delta NA) with the cold pressor test (CPT). 2. The CPT was well reproducible for BP and NA when performed at a 2 week interval in patients with mild hypertension. 3. After administration for 4 weeks, guanfacine (Gf; alpha 2-adrenoceptor agonist) decreased the delta NA response to CPT. 4. After administration for 2 or 4 weeks, bunazosin (Bu; alpha 1-adrenoceptor antagonist) atenolol (At; beta 1-adrenoceptor antagonist) and nadolol (Nd; non-selective beta-adrenoceptor antagonist) did not affect the delta NA response to CPT. 5. Both Gf and Bu decreased the systolic blood pressure response (delta SBP) to CPT after 4 weeks of the administration. Neither At nor Nd significantly changed the delta SBP response to CPT. 6. It is likely that Gf stimulated the presynaptic alpha 2 adrenoceptors at the sympathetic nerve endings as well as the central alpha 2 adrenoceptors, inhibiting the release of noradrenaline. It is unlikely that Bu, At and Nd exerted any clearly defined action on the presynaptic adrenoceptors in human hypertensive subjects.
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PMID:A comparison of guanfacine, bunazosin, atenolol and nadolol on blood pressure and plasma noradrenaline responses to cold pressor testing. 135 84

A reduced venous compliance and/or inadequate venoconstriction could impair hemodynamics during hemodialysis. Therefore, compliance and reactivity of the peripheral venous system were assessed in hemodialysis patients and controls using strain gauge plethysmography. Reactivity of the venous system towards an efferent sympathetic stimulus was assessed using a cold pressor test. Results showed that venous compliance was reduced in hypertensive hemodialysis patients compared to normotensive dialysis patients (P = 0.013) and normotensive controls (P = 0.004). After one dosage with a directly acting venodilator (nitroglycerin 5 mg s.l.) and 3 days of treatment with an alpha 1-sympathicolytic agent (Doxazosin 2 mg), venous compliance remained unaltered in hypertensive dialysis patients. During the cold pressor test, the blood pressure response, rise in noradrenaline levels and decline in venous compliance were normal in hemodialysis patients. However, their response to the Valsalva manoeuver was significantly impaired (P = 0.011) compared to healthy controls. We conclude that hypertension, not renal failure, causes the reduction of peripheral venous compliance in hemodialysis patients, for which structural factors might be responsible. Despite the existence of autonomous neuropathy, the reaction of the peripheral venous system towards an efferent sympathetic stimulus is intact in hemodialysis patients.
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PMID:Compliance and reactivity of the peripheral venous system in chronic intermittent hemodialysis. 135 48

To clarify the role of the renal and hypothalamic noradrenergic systems in the antihypertensive actions of dietary potassium supplementation in salt-loaded spontaneously hypertensive rats (SHR), we measured systolic blood pressure and norepinephrine turnover, which was determined from the rate of decline of tissue norepinephrine concentration after the administration of alpha-methyl-p-tyrosine, in 5-week-old SHR or age-matched Wistar-Kyoto (WKY) rats eating normal-NaCl (0.66%) or high-NaCl (8%) diet with supplementation of 8% KCl. In WKY rats, neither high-sodium nor high-potassium diets had an effect on blood pressure with no change in renal or hypothalamic norepinephrine turnover. In SHR, however, salt loading accelerated the development of hypertension. Potassium supplementation did not affect blood pressure in normal-sodium SHR but attenuated the rise in blood pressure with salt loads. Correspondingly, renal norepinephrine turnover in SHR was increased compared with that of WKY rats, and salt loading further potentiated the increased turnover in the kidney; however, no changes in hypothalamic turnover occurred. Potassium supplementation attenuated the rise in blood pressure with salt loads and the increased renal turnover. Stimulation of sympathetic discharge by cold exposure after the administration of alpha-methyl-p-tyrosine produced marked depletion of norepinephrine in most tissues. The loss of norepinephrine was significantly greater in both kidney and hypothalamus of salt-loaded SHR than in those of normal-sodium SHR, but potassium could normalize this. Thus, potassium not only diminished the increased renal norepinephrine turnover in the kidney under normal conditions but also attenuated the augmented renal and hypothalamic norepinephrine turnover by cold stress in salt-loaded SHR.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertension 1992 Oct
PMID:Role of hypothalamic-renal noradrenergic systems in hypotensive action of potassium. 135 21

Examination is performed on 87 miners from mine for copper production subject to intensive local vibrations with average rate of increase (K) of the norms for the individual octave frequencies 2.4 times for 3 h exposure of the working shift, as well as to intensive noise--113-115 dB/A equivalent level, general dust--23 mg/m3, fine dust--3.5 mg/m3 and fine quartz--0.43 mg/m3. There are data for vibration effect--changes in the cold test, vibration sensoriness, ultra sound sonometry, in all miners. In a significant part of them are established dyslipoproteinemia--increase of triglycerides, total and LDL cholesterol, values beyond reference (mainly above the norm) of 10 electrolytes and microelements in blood serum (blood). An extremely high prevalence of the cases and the days of total morbidity with temporary disability (respectively 189.7 and 2935 per 100), with predominance in its structure of diseases of the central and peripheral nervous systems, hypertension disease, etc. The importance of vibrations for disorder in the metabolic processes in the organism and development of temporary diseases are underlined.
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PMID:[Lipid and mineral metabolism and morbidity with temporary loss of work capacity in miners]. 136 39

Neurochemical changes in the extracellular fluid of the rostral ventrolateral medulla (RVLM) were produced by changes in arterial blood pressure. Blood pressure was raised or lowered with systemic infusions of phenylephrine or nitroprusside and neurochemicals were recovered from RVLM by in vivo microdialysis. A dialysis probe 300 microns in diameter and 500 microns in length was stereotaxically implanted in the RVLM of the urethane-anesthetized rat. Sterile physiological Ringer's solution was perfused at a rate of 1.5 microliter/min. The perfusate was collected under ice-cold conditions every 15 min for the assay of epinephrine, dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), ascorbic acid, and uric acid. After stable baseline neurochemical concentrations were achieved, animals were infused with phenylephrine or nitroprusside intravenously to raise or lower the blood pressure. Increasing blood pressure 50 mm Hg above the baseline value by phenylephrine led to a significant reduction in heart rate and a reduction in extracellular epinephrine and DOPAC concentrations. The 5-HIAA concentration was increased during the hypertensive drug infusion. There were no changes in the concentrations of ascorbic acid or uric acid. Hypotension produced by nitroprusside (-20 mm Hg) led to neurochemical changes which were the reciprocal of those seen during hypertension. During hypotension, heart rate increased as did the extracellular fluid epinephrine concentration. The 5-HIAA concentration fell with hypotension and remained depressed following the nitroprusside infusion. Ascorbic acid and uric acid concentrations did not change during hypotension but ascorbic acid did increase after the nitroprusside infusion stopped. These data provide direct evidence that epinephrine release in RVLM is linked to changes in systemic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Drug-induced changes in blood pressure lead to changes in extracellular concentrations of epinephrine, dihydroxyphenylacetic acid, and 5-hydroxyindoleacetic acid in the rostral ventrolateral medulla of the rat. 137 44

Fourteen women with hypertension of pregnancy and who were in their last trimester were subjected to three standardized physical stress tests before and after 1-2 weeks of treatment with 5 mg of isradipine twice daily. Their blood pressure and heart rate responses to the isometric handgrip exercise, the cold pressor test, and the orthostatic tilt test were recorded. Treatment with isradipine reduced systolic and diastolic blood pressures significantly at rest. However, although the diastolic blood pressure was reduced during the stress tests, the decrease was significant only during cold pressor testing.
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PMID:Effect of isradipine on responses to standardized physical stress tests in hypertension of pregnancy. 137 50


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