摘要:

Using radioactive oxygen (O15), carbon monoxide and carbon dioxide with external counting over the chest, it is possible to measure perfusion and diffusion per unit of lung volume. Patients with mitral stenosis, particularly those with high pulmonary artery pressures, may show a higher blood flow through the upper zone of the lung than the lower. This distribution of blood flow is the reverse of that found in normal subjects. The observed changes in blood flow are consistent with the radiological and pathological changes in the pulmonary vascular tree in mitral stenosis.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The suggestion that the pathogenesis of adrenal-regeneration hypertension might involve sensitization to the hypertensive properties of corticosterone by the period of cortical insufficiency which follows adrenal enucleation has been investigated. Nonhypertensive doses of corticosterone were given to uninephrectomized, salt-treated and adrenalectomized rats after periods of insufficiency of variable length and to similar rats bearing regenerating adrenals, beginning such treatment at intervals after enucleation. The following conclusions have been drawn from the data obtained: (1) Adrenal cortical insufficiency for as long as 2 weeks did not sensitize to the hypertension-inducing property of corticosterone; (2) Corticosterone administration to rats bearing regenerating adrenals, beginning treatment up to 3 weeks after operation, did not enhance the development of hypertension or increase the severity of vascular lesions.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Electrocardiograms recorded with a direct-coupled amplifier and recordings of intramyocardial and intracellular potentials were used to determine the nature of the S-T segment shift after myocardial injury. Immediately after coronary artery ligation in the dog, both true S-T and T-Q changes are produced. Lack of responsiveness to the activation wave in the injured area does not account for the initial change in the S-T segment. Changes in the intracellular action potential can be correlated with the electrocardiographic changes. Immediately after injury, cells in the injured area usually repolarize more rapidly than normal cells and this change is significantly correlated with S-T segment shifts. A decrease in resting potential, generally oc curring later than the action potential changes, is similarly correlated with T-Q segment changes.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

In open-chest dogs the circulation was carried on a heart-lung machine. The right heart and the left atrium were drained. A balloon was placed in the virtually bloodless left ventricle and filled with a known volume of air at the beginning of an experiment; left ventricular pressure was recorded after a steady state had become established. After this control observation, the preparation was exposed to experimental maneuvers, such as variation of the systemic flow rate or changes of the air volume in the balloon. At one or more later stages of the same experiment, the balloon was emptied, the heart was allowed to beat empty for several minutes, and the standard observation was again repeated. Comparison of left ventricular pressures from the initial and later observations showed that the diastolic pressure in the left ventricle increased in the course of the experiment even though other conditions were comparable. From this we conclude that experimental maneuvers injuring the heart muscle reduce its distensibility. The water content of injured hearts was abnormally elevated; myocardial edema is therefore not excluded as one of the mechanisms explaining the reduced distensibility of injured heart muscle.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The marked intensification of experimental left ventricular failure by veno-arterial pumping which was seen in earlier experiments suggested changes of myocardial elasticity as a mechanism. Two experimental procedures were therefore applied here, in which the pressure in the coronary arteries and veins could be varied at will, where the left ventricle was distended by an air-filled balloon, and where the coronary tree did not communicate with the left ventricle. Changes of the coronary arterial or venous pressures were accompanied by homodirectional changes of the left ventricular diastolic pressure which were of large magnitude and which could not be explained by unobserved blood flow into the left ventricle or by other factors.The inverse relationship between coronary vascular pressures and myocardial distensibility was probably caused by the increasing volume of blood which was retained in the coronary arteries and veins when the coronary arterial or venous pressures were increased. This passive increase in coronary blood volume (turgor) must have changed the resiliency of the coronary tree. The changed elastic properties of the coronary tree then resulted in a change of the elastic properties of the heart.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Electrophysiologic mapping experiments on the excitation of the A-V node of isolated rabbit heart have been performed with intracellular microelectrodes. An area of tissue showing peculiar physiologic characteristics was shown to coincide, at least in part, with the histologic A-V node and His bundle. Three functional regions have been determined in the physiologic mapping of the A-V node. The middle layer (N) shows signs of decremental conduction and is the site of the slowest propagation velocity in the A-V node. The other layers are transitional regions between the N layer and atrium (AN) or the His bundle (NH). The AN layer shows a progressively slower propagation velocity as the N region is approached. The same holds for the NH region. A precise correlation between these findings and the 3 existent histologic layers remains to be determined. The existence of an area of peculiar tissue just above the A-V valves and encircling the A-V orifice has been confirmed. This area is continuous with the AN layer of the functional A-V node and has been named the atrioventricular ring (AVR) on the assumption that it is a remnant of the embryonic A-V ring. Wenckebach cycles and A-V block of nodal origin are tentatively explained as resulting from increased decrement in the middle nodal layer (N).

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The effect of ethanol on serum cholesterol concentration has been studied in normal male dogs subsisting on diets of low cholesterol content. Daily administration of 1.65 Gm. ethanol/Kg, of body weight produced significant increases of serum cholesterol in dogs when fed either a low-fat diet (4 per cent of fat calories) or a high-fat (40 per cent) diet. The mean cholesterol increase after 2 weeks of ethanol administration was 52 mg./100 ml. (SE, 8.2) for 8 dogs on the low-fat diet, and 75 (SE, 6.6) for 24 dogs on the high-fat (lard) diet. No significant difference was found between the mean increases of serum cholesterol produced by ethanol administration, using either the high-fat diet of saturated fat (lard) or that of unsaturated fat (sunflower oil). Serum cholesterol concentration decreases rapidly after discontinuing the administration of ethanol, reaching the prealcohol levels in 2 to 3 weeks. The higher levels of serum cholesterol are maintained as long as the administration of ethanol continues. Sodium acetate, when given at the same molar quantity as ethanol, failed to produce any change of serum cholesterol concentration in the dog.The effect of ethanol administration on serum cholesterol concentration in man was tested in 2 switchback experiments, comparing the effects of alcohol and those of a supplement of syrup of equal calorie value while the men were eating a normal diet containing 38 per cent of fat calories. When 0.45 Gm. ethanol/ Kg./day were given to 59 normal men for 3 weeks, no significant difference of serum cholesterol concentration was observed between the values on syrup and on alcohol. However, the administration of 1.35 Gm./Kg./ day to 14 men produced a mean increase of serum cholesterol concentration of 18 mg./100 ml. (SE, 5.0) within 1 week. The individual increases of serum cholesterol are correlated with the intrinsic cholesterol levels of the subjects (r = + 0.67, p > 0.01). It is concluded that ethanol increases serum cholesterol concentration in the dog and man. The response in the dog is much greater than that observed in the human subjects.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

In vitro estimation of aortic QO2in normal rabbits revealed the thoracic portion to be lower than that of the arch and abdominal segments. These latter were not significantly different. Renal hypertension, cortisone administration and their combination with or without cholesterol feeding resulted in significant elevations of the oxygen consumption of all segments. The thoracic portion under these conditions was lowest and that of the arch was greater than that observed in the abdominal aorta. A depression of QO2was observed in the aortas from normotensive rabbits subjected to cholesterol feeding with or without cortisone treatment.Although these findings indicate that hypertension and cortisone may profoundly alter the metabolic activity of the aorta, they could not be correlated with the degrees of cholesterol atherosclerosis observed in the various experimental situations explored.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

A measurable factor determining the filling of the heart is the opposition that the myocardium offers to being stretched. This is expressed as “renitence,” which is the ratio of filling pressure to the rate of inflow. Isolated frog ventricle was connected to a vessel containing Ringer's solution at a fixed head of pressure. Change in the volume of the heart was recorded optically. From these time-volume curves, renitence was calculated.For the frog ventricle filling and emptying against a fixed head of pressure, the renitence during the filling period first decreases, passes through a minimum, and then increases. The minimum and average renitences occurring during a cycle appeared to be increased by cooling, a rise in filling pressure, pentobarbital or a combination of hypoxia and acidity.The renitence early during the filling cycle is largely determined by the residual tension from the previous systole, and the subsequent increase seems to be determined by the elastic properties of the myocardium.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Thirty-six isolated frog ventricles were attached to an inflow cannula with stopcocks that could permit direct systolic ejection back into the reservoir, return flow back to the reservoir by another route through a valve, or isochorie contractions. The heart, enclosed in a container with a “U” tube outlet, produced pressure changes (extra-cardiac) which could be used in determining the in-flow rate and transmural pressures. The rate of change of the transmural pressure was calculated for the frog ventricle during early diastole. This value was taken as a measurement of the rate of relaxation. The effects of epinephrine (.02 μg./ml.) were studied. At low filling pressures without valves (and therefore with outflow pressure equal to inflow pressure), epinephrine slows the rate of relaxation, although other inotropic effects, such as an increase in stroke volumes, are present. If, however, the heart contracts against a high outflow pressure or resistance the rate of relaxation is increased by epinephrine. The slowing of relaxation in the former case is a result of filling commencing before relaxation is complete. In the isochoric heart, epinephrine does not change the time of positive tension, but does accelerate the relaxation after contraction.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID