摘要:

Experiments with a rubber tube model of the aorta have demonstrated the presence of longitudinal waves in the wall of the tubing. This mode of vibration was predicted by Lamb from the theoretical considerations, but has not previously been described. The characteristics of “impact waves” in arteries and of the longitudinal mural waves in the model appear to be similar. Longitudinal waves undoubtedly influence the arterial pulse contour. Theoretically, the damping coefficient for them is the same as that for radial waves.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

A method is described for the measurement of the collateral pulmonary blood flow in the thoracotomized dog by utilization of a flow-meter which measures flow into an aortic sac from which the bronchial arteries arise. This preparation maintains the normal perfusing pressures and diminishes phase changes in the arterial pulse waves. The bronchial vascular resistance is increased by an increase in the insufflation air pressure, by bilateral vagotomy, or by the administration ofl-epinephrine into the bronchial arterial circulation. The bronchial vascular resistance was decreased after a transitory interruption of the bronchial arterial blood flow (reactive hyperemia). After administration of serotonin in the bronchial artery, a transient increase in resistance was followed by a marked decrease. Intrapulmonary vascular injections produced only a decrease in resistance. The present data demonstrate the sensitivity of the preparation described.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The effects of lipemia upon the coronary circulation and myocardial oxygenation, and arterial oxygen and carbon dioxide contents were studied in 13 control dogs and 20 animals with myocardial scars. Acutely induced lipemia caused a significant decrease in the cardiac output, coronary blood flow and myocardial oxygen consumption in both groups of animals. These changes were similar to those observed in experimental coronary artery embolization. The slow intravenous fat infusion did not cause a significant drop in the mean arterial pressures of these dogs. All animals in this series developed hyperpnea during fat infusion. There was a simultaneous lowering of the arterial oxygen saturation and carbon dioxide content. These changes were in some ways similar to those observed by other investigators in experimental pulmonary embolization. However, the slow fat infusion did not produce a significant elevation of the pulmonary arterial pressures of these dogs. These data suggest that the chylomicra, like most macromolecular substances, may produce mechanical interference to the coronary blood flow and impose a limitation to myocardial oxygenation, while the total oxygen consumption of the animal is unaltered by lipemia.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Spontaneous vasomotor activity, as evidenced by the presence of alpha or beta waves in the paw plethysmogram, was demonstrated in 10 sympathectomized, 4 denervated, and 8 (ganglionic or adrenergic) blockaded extremities in dogs. Alpha waves occur during natural sleep and during anesthesia. They are present after removal and denervation of the carotid and aortic chemoreceptors. They occur in the splenectoinized animal. Alpha waves are usually synchronous in a pair of normally innerverted extremities. They may be synchronous, asynchronous, or absent in one paw when one extremity (or both) is denervated or sympathectomized. The significance of this information is discussed in relation to the factors which may control spontaneous vasomotor activity.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

In anesthetized open-chest and closed-chest dogs subjected to plethora and hemorrhage, pressures were measured simultaneously in the right atrium, right and left ventricles, and the pleural and pericardial spaces. It was found that an increase in ventricular end-diastolic pressure above approximately 1 mm. Hg was associated with a rise in pericardial pressure of nearly the same amount. Thus, the practice of defining “effective” ventricular end-diastolic pressure as the difference between the ventricular and intrapleural pressure gives erroneous values when ventricular end-diastolic pressure is greater than a few mm. Hg. The true ventricular transmural pressure is the difference between ventricular end-diastolic and pericardial end-diastolic pressure and has a value of no more than 2 or 3 mm. Hg under all except the most abnormal circumstances. When ventricular end-diastolic pressure is greater than a few mm. Hg, the pericardial pressure at the end of systole is likewise elevated, but to a lesser degree. Thus, when ventricular end-diastolic pressure is elevated, the measured ventricular end-systolic pressure is greater than the pressure developed by ventricular muscular contraction because end-systolic pressure is the algebraic sum of the pressure developed by ventricular muscular contraction and the pressure in the pericardial space. This error in ventricular systolic pressure may be relatively large for the right and small for the left ventricle. Pericardial pressure decreases during ventricular systole, lowers the pressure on the outside of the atria, and thus, tends to draw blood into the right atrium during ventricular systole.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Studies were performed to determine the effects of phenylephrine in dogs under chloralose as influenced by mechanical buffering of blood pressure, adrenergic blockade produced by injection of phenoxybenzamine, and combination of the mechanical buffering of blood pressure and phenoxybenzamine administration. Chloralose did not interfere with and possibly mildly sensitized the cardioinhibitory response to phenylephrine. Tachyphylaxis did not occur when moderate doses of phenylephrine were injected at intervals of not less than 15 minutes. Either mechanical buffering or administration of phenoxybenzamine partially prevented the pressor response to phenylephrine, and the cardioinhibitory response correspondingly was less. When the increase in blood pressure was prevented entirely by mechanical buffering of blood pressure combined with phenoxybenzamine administration, phenylephrine caused either no change in heart rate or a mild acceleration. It is concluded that the decreases in heart rate which are observed following injection of phenylephrine, in the doses used in this study, are secondary to the adrenergic actions of the compound.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

One of the problems of Dicumarol administration has been determination of the adequacy of therapy. A fundamental stage in thrombus formation in the circulation is platelet clumping. Since platelets are involved in both hemostasis and thrombosis, a study of changes in platelet function may prove useful. The effects of Dicumarol on platelet clumping and adhesiveness have, therefore, been studied and related to changes in other clotting mechanisms.Comparison of platelet function in control periods and during Dicumarol administration shows that this drug lowers the adhesive index and prolongs the platelet clumping time to a highly significant degree. The accuracy of estimates of these 2 platelet functions given by 3 other tests, prothrombin time, whole blood clotting time and plasma activity in the thromboplastin generation tests have been compared. By any criterion, degree of correlation, consistency of regression slopes, intercepts or scatter about regression lines, clotting time was the most efficient of the 3 tests for evaluting platelet function. The prothrombin time was the least efficient. Furthermore, hemorrhage from excessive dosage was closely related to the platelet clumping time and clotting time. It should be pointed out, however, that in about one-third of the patients the prothrombin time was as good an index of platelet clumping time as clotting time. While prothrombin times done with 2 different sources of thromboplastin may give congruous results in untreated patients, considerable discrepancies may appear during Dicumarol therapy.If prothrombin time is to be used as a guide to Dicumarol therapy, it is important to establish in each patient separately its reliability as a measure of the behavior of the clotting mechanism as a whole. For those in whom it seems reliable, an individual “therapeutic range” should be determined. For other cases, some other suitable test should be employed. It is emphasized that regulation of Dicumarol dosage is an individual problem and that only those tests shown to be reliable indices of safe effective modifications of clotting mechanism in the individual patient should be used.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Electrical activity of the specialized conducting system (His bundle, bundle branches, false tendons and peripheral Purkinje fibers) of canine hearts has been recorded in situ through electrodes attached to the endocardium during total cardiopulmonary bypass. Simultaneous records from multiple sites have been correlated with electrocardiograms to indicate the sequence of activation of the specialized conducting system during normal and retrograde activation and during vagal stimulation. The results obtained indicate that the method employed has several advantages among which are an absence of injury at the recording site and an applicability to chronic studies.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

An attempt has been made to measure the capillary blood flows through the individual tissues of the ileum of normal dogs and those which were in endotoxin shock. The technic used was based upon the assumption that the uptake of D2O by the tissues was limited by the capillary flow. In loops from endotoxin shock dogs which were perfused at normal blood pressure (135 mm. Hg), the tissue perfusion ratios calculated on this assumption were reduced to about one-half of the control value in the mucosa and to about three-fourths in the submucosa and muscularis, despite the fact that total blood flow was unchanged. When the loops from shock dogs were perfused at the dog's pressure (70 mm. Hg), there was a further decrease of about 50 per cent in both the total blood flow and the tissue perfusion ratios. It is concluded that this reduction in tissue capillary flow, especially in the mucosa, may be the basis of the pathological changes in the intestine in endotoxin shock.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Seventy-one pregnant rats of a Sprague-Dawley strain were exposed for a single 24-hour period to a gas mixture of 6 per cent carbon dioxide, 20 per cent oxygen and 74 per cent nitrogen on different days during gestation. There were 530 offspring and these were compared with 159 newborn rats from 21 control dams. The incidence of cardiac malformations was 23.4 per cent in the test group and 6.8 per cent in the control group with the highest incidence in the test group occurring when the exposure was on the tenth day of gestation. Isolated ventricular septal defects, situated in the lower and posterior part of the muscle septum, were found in 8 cases, ventricular septal defects with overriding aorta in 24 cases and ventricular septal defects with partial transposition in 20 cases. Forty-seven of the abnormal hearts had a myocardial thickening accompanied by narrowing of the pulmonic or aortic outflow channel with or without other abnormalities, such as atresia of the mitral or tricuspid valves and hypoplasia of the aorta or pulmonary artery. There was a slight increase in perinatal mortality in the test group, and a lower frequency of male offspring. The average body weight was 18.9 per cent higher in the test group.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID