摘要:

We have made simultaneous measurements of the instantaneous flow in the main pulmonary artery using an electromagnetic flowmeter and the pulmonary capillaries using the nitrous oxide body plethysmograph method in six lightly anesthetized and spontaneously breathing dogs. We measured the transmission of the flow wave in the pulmonary arterial tree at a variety of heart rates and during alveolar hypoxia. Fourier analysis enabled us to study transmission in the intact animal in a way similar to that of imposed oscillations of flow in the isolated organ. The amplitude of the pulmonary capillary flow pulse was approximately half that in the main pulmonary artery. There was progressive decrease in amplitude from the first to the fourth harmonic in both the pulmonary arterial and pulmonary capillary flow pulses. Harmonics above the fourth were small and variable in amplitude. Transmission between pulmonary valve and capillaries was independent of heart rate. Hypoxia did not affect transmission. Assuming that the increase in resistance in this instance was due to precapillary vasoconstriction, this finding suggests that other factors may offset the effect of increase in resistance upon transmission.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Control of the coronary circulation by the carotid sinus was studied in intact, unanesthetized dogs instrumented with Doppler ultrasonic flow probes on the left circumflex coronary artery, miniature pressure gauges in the aorta, and stimulating electrodes on the carotid sinus nerves. A radiofrequency pacemaker was used to stimulate the nerves in dogs at rest, during sleep, exercise, and after autonomic blockade. Thirty-second periods of stimulation in the resting conscious dog resulted in an average decrease in aortic pressure of 28%, an average decrease in mean coronary flow of 7%, while heart rate decreased by 13% at the beginning of stimulation and then returned to control levels. Mean and late diastolic coronary resistances decreased by an average of 22% from control. Similar results occurred with carotid sinus nerve stimulation during sleep and during treadmill exercise. Combined beta-receptor blockade with propranolol and atropine prevented the changes in heart rate with carotid sinus nerve stimulation but not the decrease in arterial pressure or the coronary dilatation. After alpha-receptor blockade with phenoxybenzamine or sympathetic blockade with guanethidine, coronary dilatation was not observed with carotid sinus nerve stimulation. Thus sympathetic constrictor tone is present in the resting conscious dog and the coronary dilatation observed with electrical stimulation of the carotid sinus nerves is due to a reduction in resting sympathetic constrictor tone.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The frog retrolingual membrane was used as a model microcirculatory system for evaluating the role of neural control. Terminal arterioles were studied before and 2 to 21 days after topical application of 6-hydroxydopamine (6-HDA). When arterioles were visualized microscopically in vivo and stimulated directly with a microelectrode, 6-HDA reduced the normal, longitudinally conducted vasoconstriction to a local response. Current intensities needed for threshold responses averaged more than fourfold those of control thresholds. Nerve induced vasoconstriction was abolished, whereas nerve-induced vasodilation persisted after 6-HDA. Ultrastructurally, 6-HDA produced extensive degeneration only in perivascular nerves containing large granular vesicles, although vasomotor nerves with clear vesicles, vascular smooth muscle, Schwann cells, endothelial cells, motor end plates, and striated muscle appeared normal after 6-HDA treatment. Autoradiography and fluorescence histochemistry revealed that the perivascular nerves were no longer capable of taking up or binding exogenous catecholamine. The results indicate that topically applied 6-HDA produces selective dysfunction of adrenergic nerves correlated with fine structural degeneration. The absence of conducted vasoconstrictor responses in this preparation indicates their dependence on an intact adrenergic nerve supply.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The effects of hypothermia on the sympathetic neuroeffector junction were studied in the isolated perfused cat spleen. The experiments were aimed at determining the temperature dependence both of prejunctional events, i.e., efflux of norepinephrine from the sympathetic nerves in response to electrical stimulation or to indirectly acting sympathomimetic amines like tyramine or phenethylamine, and of postjunctional events, i.e., the contractile response of the smooth muscle to the norepinephrine liberated. Hypothermia was found to depress both the norepinephrine efflux in response to stimulation and the contractile response to the endogenous norepinephrine released, as well as to exogenous norepinephrine. However, these processes were found to respond differently to temperature change. Thus hypothermia depressed norepinephrine release as well as the pressor responses to tyramine and phenethylamine much more strongly than the corresponding responses to electrical nerve stimulation or the pressor response to exogenous norepinephrine. The results strongly support the concept that sympathomimetic amines release norepinephrine from sympathetic nerves by mechanisms which differ from those mediating norepinephrine release induced by depolarization.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Membrane potentials were recorded from a region of the left atrium close to the interatrial septum and from an atrial appendage. Pacemaker activity was induced after exposure to Ba2+. The magnitude of the resting potential and of the overshoot decreased with increasing [Ba2+]o, whereas duration of the action potential and rise time increased with increasing [Ba2+]o. Electrical stimulation for 5 sec at 1/sec to left atria showing automaticity produced bradycardia followed by tachycardia. Bradycardia was abolished by atropine; tachycardia was suppressed by propranolol and previous treatment with reserpine. At zero [Ca2+]o, threshold concentrations of Ba2+for inducing automaticity were lower than those at normal [Ca2+]o. Ba2+markedly prolonged the action potential plateau in solutions deprived of Ca2+. The size of the overshoot was increased and the rise time was shortened despite a significant reduction in the resting potential. Ba2+partly restored atrial contractility abolished at zero [Ca2+]o. Each electrical discharge evoked an individual contraction, and a sufficiently fast discharge led to summation of the contractions. Pacemaker activity induced by Ba2+was suppressed by adding Ca2+and Mg2+. The threshold potential was raised by Ca2+and Mg2+. Threshold concentrations of Ba2+for inducing automaticity were not influenced by previous treatment with reserpine.It is postulated that Ba2+antagonizes the movement of K+across the membrane, resulting in a decrease in the resting potential and a prolongation of the action potential duration, and that Ba2+serves as a current-carrying ion at zero [Ca2+]o. It seems unlikely that cardiac norepinephrine participates in pacemaker activity induced by Ba2+.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Rhesus monkeys subjected to the atherogenic stimulus of a high-fat, high-cholesterol diet showed significant coronary atheromatosis at the end of 17 months. Smaller fibrotic lesions with scant stainable lipid were found in animals that were subsequently fed either of two cholesterol-free diets for 40 months. The average cross-sectional area of the lumen was more than 80% greater in regression animals than in monkeys with baseline atherosclerosis. The data support the hypothesis that uncomplicated coronary atheromas may regress in primates in appropriate dietary settings.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID