ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The contribution of the fastigial nucleus and the vestibular nerves (eighth cranial nerves) to the orthostatic reflexes in anesthetized, paralyzed cats was studied. Bilateral lesions of the rostral fastigial nucleus resulted in impairment of the reflex changes in blood pressure, femoral arterial flow, and resistance evoked by head-up tilting to 30° or 60°. The deficit consisted of an increase in the magnitude of the initial fall in blood pressure during tilting. The effects on blood pressure were paralleled by decreased vasoconstriction in the femoral artery. Extracranial lesions of the vestibular nerves produced comparable deficits which were not enhanced by subsequent lesions of the fastigial nucleus. Denervation of the baroreceptors impaired the reflexes, and subsequent lesion of the fastigial nucleus increased this deficit. The pressor response evoked by electrical stimulation of the rostral fastigial nucleus also reversed the deficit in orthostasis produced by hemorrhage. Small doses of sodium pentobarbital which did not alter the resting blood pressure or the pressor response to carotid occlusion impaired the responses to stimulation of the fastigial nucleus and tilting. Therefore, the rostral fastigial nucleus, which might be triggered by the vestibular apparatus, appears to participate in concert with the baroreceptors in the initiation and possibly the maintenance of the orthostatic reflexes.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The mechanism of action of peptide inhibitors on angiotensin I-converting enzyme (Al-converting enzyme) was studied in relation to the substrate requirements of the enzyme in vivo in the dog lung and in vitro in plasma. 1-d-Asp-8-Ile-AI prepared by the solid-phase technique was compared with the known peptide inhibitors of Al-converting enzyme. BPP5a(Pyr-Lys-Trp-Ala-Pro) and SQ 20881 (Pyr-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro)125I-1-d-Asp-8-Ile-AI was evaluated for susceptibility to cleavage by the Al-converting enzyme. In vitro and in vivo,125I-1-d-Asp-8-Ile-AI or BPP5ain 50,000-fold molar excess produced only a slight delay in conversion of1251-AI to125I-angiotension II (AII); SQ 20881 blocked conversion completely. In vivo, l-d-Asp-8-Ile-AI or BPP5ainjected into the pulmonary circulation in 250-fold molar excess (250 nmole/kg) did not cause a diminution in the pressor response to AI administered 30 seconds later; SQ 20881 blocked the pressor response to Al for 60–90 minutes. 1-d-Asp-8-Ile-AI was a poor substrate for converting enzyme, since125I-1-d-Asp-8-Ile-AI was not converted to125I-1-d-Asp-8-Ile-AII, and unlabeled 1-d-Asp-8-Ile-AI did not block the pressor response to exogenous AII.125I-1-d-Asp-8-lle-AI was stable in plasma and in the pulmonary circulation The results suggest that since 1-d-Asp-8-Ile-AI is neither a substrate nor a blocker, substitution of the aliphatic residue Ile in the 8 position of AI may prevent binding to an active site in the AI-converting enzyme.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

A total of 16 rabbits developed atherosclerosis after receiving a diet containing 1% cholesterol and 6% sunflower seed oil for up to 67 weeks. Their mean blood pressure rose from 85 to 114 mm Hg. The aortic arch region was isolated and perfused with Krebs-Henseleit solution, and the impulse activity of 70 single aortic and 8 right subclavian baroreceptor fibers was studied during step increases and decreases in perfusion pressure. The threshold pressure of the aortic baroreceptor fibers from the atherosclerotic rabbits was only slightly higher (P> 0.4) than that of 29 fibers from 17 normal rabbits, but the impulse frequency was less (P< 0.02). The gradient of the impulse frequency-pressure curves (0.73 impulses/sec mm Hg−1), was significantly lower (P< 0.01) than normal (1.19 impulses/sec mm Hg−1), as was the gradient of the curves from the right subclavian baroreceptor region. The curves resulting from first increasing and then decreasing the perfusion pressure were more separated in the atherosclerotic rabbits than they were in the normal rabbits. There was a correlation between the amount of the reduction in the sensitivity of the aortic baroreceptors and the length of time the rabbits had been on the lipemic diet (r= 0.96). The changes in the baroreceptor activity were associated with a reduction in the distensibility of the perfused area and with histological lesions in the baroreceptors and the arterial walls. The mild hypertension in the atherosclerotic rabbits could partly be accounted for by the reduction in aortic baroreceptor activity. Similar mechanisms might contribute to blood pressure anomalies in humans with atherosclerosis.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The effects of an extracellular sodium (Na) concentration of 200 mM on function, ionic exchange, and water movements were examined in the vascularly perfused rabbit intraventricular septum. When the perfusate was switched from 1.42 mM Na to 200 mM Na, dP/dt fell 20.4% over 2 minutes; dP/dt then recovered to the control level. The time course of the functional recovery correlated with the uptake of Na into the slowly exchangeable fraction of the tissue, and the rate of recovery in 200 mM Na depended on the frequency of contraction of the preparation. During perfusion with 200 mM Na, a 41% increase in slow-phase Na content compared with the content during perfusion with 142 mM Na was observed. The hyperosmolar perfusate induced a 21% cellular dehydration within 10 minutes as estimated from measurement of 10-minute35SO4space and total tissue water. The time course of dehydration was much more rapid than the time course of functional recovery. Calcium (Ca) influx during the period when dP/dt had returned to control levels in 200 mM Na was the same as it was during a control period in 1.42 mM Na. Thus, there appears to be a Na-Ca exchange system which enhances Ca influx and thus causes an inotropic effect in response to an increase in intracellular Na concentration.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The baroreceptor fibers which arise from the aortic arch course centrally within the vagus nerve in the dog, and they usually follow this path in the cat. Near the origin of the superior laryngeal nerve, a separate branch of the cervical vagus (the cervical aortic nerve) arises. Previously, it was thought that this nerve contained all the important baroreceptor afferents. Aortic baroreceptor fibers that are not within the cervical aortic nerve were studied in the anesthetized cat and dog after cervical aortic and carotid sinus nerves had been sectioned. Some experiments were acute, but most were conducted 13–60 days after nerve section (to allow transected nerves to degenerate). After degeneration, baroreceptor activity was found in the peripheral aortic nerves in most animals. The sensory terminals of the surviving baroreceptor fibers were on the aortic arch on the left side and at the root of the right subclavian artery on the right side. In one of four chronic cats, four of eight chronic dogs after degeneration, and one of three animals in acute experiments a depressor response (8–70 mm Hg in chronic and 10 mm Hg in acute experiments) followed stimulation of the peripheral aortic nerve. The surviving aortic baroreceptor fibers coursed centrally in the cervical vagus.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

In eight male subjects the blood volume was changed (± 10%) by hemorrhage and transfusion. One cycle of blood infusion and withdrawal or hemorrhage and reinfusion was completed within 9 minutes. The effective compliance of the total circulation was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume. The effective compliance was 2.3 ml/mm Hg kg−1body weight. This procedure was repeated while the capacity of the circulatory system was restricted by infusion of norepinephrine (15 μg/min), lower body positive pressure, or both. The compliance values thus obtained were: norepinephrine 1.7 ml/mm Hg kg−1body weight, lower body positive pressure 1.2 ml/mm Hg kg−1body weight, and both norepinephrine and lower body positive pressure 0.9 ml/mm Hg kg−1body weight. The effective compliance of the intrathoracic vascular bed was assumed to be between 1.2 ml/mm Hg kg−1body weight (lower body positive pressure) and 0.9 ml/mm Hg kg−1body weight (norepinephrine and lower body positive pressure). These values constitute 55% and 42% of the effective compliance of the total circulation, respectively.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The effect of sodium depletion on the dose-response relationships of angiotensin II to aldosterone and blood pressure was studied. Arterial plasma angiotensin II and aldosterone and arterial blood pressure were measured before and during the incremental infusion of angiotensin II into sodium-replete and sodium-deplete subjects. Sodium depletion caused a distinct steepening of the angiotensin Il-aldosterone dose-response curves in four of five subjects and a concurrent diminution in the pressor effect of angiotensin II. Administration of angiotensin II did not demonstrably alter the half-life of aldosterone. Sodium depletion did not change the plasma concentrations of sodium or potassium, but it was accompanied by a significant increase in plasma levels of 11-hydroxycorticosteroids and magnesium. The contrasting effects of sodium depletion on the aldosterone and the pressor dose-response curves favored sodium retention. These results are consistent with an important role for the renin-angiotensin system in the control of aldosterone secretion in man.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

In anesthetized vagotomized cats with both carotid arteries occluded, stretch of the walls of the thoracic aorta performed without obstructing aortic blood flow induced reflex increases in arterial blood pressure (systolic: 136 ± 4 [SE] to 170 ± 7 mm Hg), heart rate (230 ± 10 to 236 ± 11 beats/min), and maximum rate of rise of left ventricular pressure (dP/dt max) (2,337 ± 256 to 3,155 ± 302 mm Hg/sec). In cats with spinal transection (C1), similar increases were observed. These responses were abolished by infiltrating the walls of the thoracic aorta with xylocaine. In adrenalectomized cats with intact central nervous systems, reflex responses were reduced but were still statistically significant. Phenoxybenzamine abolished the pressor response but not the increases in heart rate and dP/dt max. Propranolol drastically reduced the increases in heart rate and dP/dt max but not the pressor response. It is concluded that stretch of the thoracic aorta induced an increase in sympathetic activity affecting the heart, the peripheral vessels, and, probably, the adrenal glands through a spinal reflex.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

The control of the local supply of oxygen to a skeletal muscle vascular bed was analyzed by: (1) determining if a relative oxygen lack causes vascular dilation, (2) ascertaining the vascular elements responsible for the dilation, and (3) attempting to elucidate the mechanism of the dilation. When the concentration of oxygen in the inspiratory air was reduced from that in room air to 18% without increasing the carbon dioxide concentration or inducing a fall in systemic arterial blood pressure, a dilation significant at the 5% level was observed in the terminal arterioles, the metarterioles, and the distribution arterioles of the cremaster muscle of the rat; all of these vessels were oriented transversely to the skeletal muscle fibers and had diameters of less than 40μ. The magnitude of the dilation, expressed as a percent of the control diameter, was inversely related to the vessel's average control diameter. No significant dilation was noted in the precapillary sphincters or the major arterioles with control diameters greater than 40μ. Intra-arterial injections of sodium cyanide produced responses that paralleled in relative magnitude those observed in similar vessels during hypoxia. The microcirculatory adjustments to mild systemic hypoxia were not altered by pharmacological blockade of sympathetic ganglia or α, β, γ, or histaminergic receptors.

ISSN:0009-7330    

出版商:OVID    

年代:1974

数据来源: OVID