摘要:

We used single-breath CO diffusing capacity to study the effect of changes in pulmonary arterial and left atrial pressures on pulmonary capillary blood volume in 15 supine dogs whose lungs were perfused with a nonpulsatile pump. Effect of pulmonary arterial pressure: When left atrial pressure measured relative to the bottom of the lungs ≤ alveolar pressure, increasing pulmonary arterial pressure increased diffusing capacity markedly (mean, 0.71 ml/min × mm Hg per mm Hg change in pulmonary arterial pressure). When left atrial pressure ≥ alveolar pressure plus the height of the lungs, increasing pulmonary arterial pressure had less effect on diffusing capacity, although blood flow was increased through a wide range (mean, 0.22 ml/min × mm Hg CO per mm Hg increase in pulmonary arterial pressure). Effect of left atrial pressure: At zero flow, increasing left atrial pressure increased diffusing capacity markedly; when pulmonary arterial pressure was high, increasing left atrial pressure had no significant effect on diffusing capacity. Increasing bronchial arterial pressure from 0 to 150 mm Hg or inhaling 10.5% CO2had no effect on diffusing capacity. Injection into the pulmonary artery of glass microspheres decreased diffusing capacity only when left atrial pressure was low; their effect was exaggerated when pulmonary arterial pressure was high in the control state.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

A strain of rats that will predictably develop experimental hypertension by means of different techniques was used to study NaCl-induced hypertension. Observations were continued for 1 year after weaning unless death intervened. Among groups of rats on 0.4, 1, 2, 4, and 8% NaCl chow, respectively, blood pressures generally rose as dietary NaCl increased. Average blood pressures ranged from 146.8 mm Hg in the group on the lowest, to 210.2 mm Hg in the group with the highest NaCl intakes. Morbidity and mortality also increased. Even transient high NaCl diets were capable of inducing permanent hypertension; 4 of 34 rats on 8% NaCl chow for only 2 weeks after weaning had pressures of 180 to 206 mm Hg, although most rats did not become significantly more hypertensive than those on the low (0.4%) NaCl diet. When this same diet was continued for a total of 6 weeks in a group of 29 animals, the blood pressure averaged 198.6 mm Hg. The age at which the high NaCl intake began also influenced the course of the hypertension. Weanling rats rapidly developed fulminating hypertension on the high NaCl diet. After 3 months on this regimen, the average pressure of 40 rats exceeded 200 mm Hg, and 35 animals were dead or terminally ill. In rats that were older when high NaCl diets were started, hypertension developed more slowly and was less fulminant. Among 38 rats in which NaCl was not begun until 3 or 6 months past weaning, blood pressures averaged 175 to 180 mm Hg after 3 months on NaCl; 31 appeared in good health but none survived 8 months.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Cardiac and aortic pressures were recorded after stellate ganglionectomy and vagotomy. Acute heart block was produced by injecting the atrioventricular node, and atrial and ventricular systoles were controlled electronically to occur independently or in any desired relationship. Angiocardiograms recorded on video tape after injections of 4 ml 69% Renovist into the left ventricle were analyzed with a videodensitometer able to detect small refluxes of contrast medium into the left atrium and correlate them with phases of the cardiac cycle. When ventricular driving was temporarily suspended but atrial driving continued, pressure records indicated mitral valve closure after each atrial systole, but reflux of contrast medium into the atrium occurred after each systole not followed by a normally sequenced ventricular systole. Driving with a 2: 1 atrioventricular stimulation resulted in reflux, with the alternate atrial contraction dissociated from ventricular systole. Thus, the mitral valve was not effectively closed by atrial systoles that were not followed by normally sequenced ventricular systoles.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Abalance method was used to investigate the viscometric behavior and aggregation properties of blood at very low shear rates. The system was essentially a parallel-plate viscometer, consisting of a thin brass plate suspended by a fine wire from one end of an analytical beam balance. The yield shear stress of a sample was obtained directly by recording stress relaxation curves. Results were obtained for homogeneous Newtonian and non-Newtonian fluids and for blood and various red cell suspensions. It was found that human and canine blood behave as fluids exhibiting a yield stress. Suspensions of red cells in saline had much smaller values of yield stress, which is consistent with greatly diminished erythrocyte aggregation when fibrinogen is lacking. Measured values of the yield stress were in the range of 0.001 to 0.1 dynes/cm2.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Lidoflazine, a newly developed coronary vasodilator, greatly enhances the coronary vasodilating action of adenosine and ATP. Experiments were designed to study the combined coronary vasodilating effects of adenosine and lidoflazine and to quantify the enhancement of coronary vasodilation of adenosine and ATP by prior administration of lidoflazine. Results of the experiments showed that the combined coronary vasodilating effects of adenosine and lidoflazine can be classified as supra-additive. For 3 hours after the administration of lidoflazine there was a great intensification (20 to 150 times) of the vasodilating action of adenosine or ATP. An adenosine-sparing effect of lidoflazine in whole blood was also demonstrated, and the enhancement of adenosine action is in part related to this effect. It is suggested that lidoflazine may also produce a change in the sensitivity of the smooth muscle of the coronary vessels to the direct or indirect action of adenosine.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

An indicator dilution method for measuring oscillatory flow in a vessel is analyzed in terms of a mixing chamber with a constant volume. For the correct measurement of mean flow, the time constant of detection of the indicator should be very much shorter than the shortest time constant of the mixing volume. The performance of such a system was examined with a thermal indicator. Although the apparent mixing volume was found not to be constant but to vary with flow, the method showed no significant error in the measurement of mean flow. There was no significant “distance distortion error” when the indicator was detected at two different points downstream from the site of infusion; this was attributed to the pattern of mixing, with detection within or close to the limits of the mixing volume. It is concluded that a properly designed indicator dilution system can measure mean blood flow without significant error, even when there is an socillatory component.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Interruption of anterior fibers of the left bundle branch system together with right bundle branch block was accomplished experimentally in canine and primate hearts. In both species the electrocardiographic effects included a major alteration of the mean electrical axis to a superior and anterior direction. Epicardial excitation was markedly delayed anteriorly, causing widening of the QRS complex in standard electrocardiographic leads. Normal outward intramural spread of excitation in anterior regions of the left ventricle was reversed after left anterior arborization block alone. After addition of right bundle branch block, intramural spread of excitation was again directed outwardly but was markedly delayed in endocardial onset. Electrical effects of these blocks could be “corrected” individually or in combination by introducing synchronized electrical stimuli distal to each lesion. A scheme is proposed by which various forms of intraventricular conduction disturbance can be defined in terms of block of one or more divisions of a three-pronged system of rapid ventricular excitation.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID