摘要:

The effect of exercise on the pulmonary circulation was studied in a group of 6 intact dogs and in a second group of 4 subjected to ligation and division of the left pulmonary artery. Observations were made with the dogs standing and running on a horizontal treadmill up to the maximal speed they could maintain for periods of at least 2 minutes, usually 12 or 14 km./hr.Continuous records were made of the difference in pressure between the main pulmonary artery (PA) and a pulmonary-artery wedge (PAW) position. Cardiac output was determined by the indicator-dilution method, with injection of indocyanine (cardiogreen) dye into the main pulmonary artery and continuous sampling from the root of the aorta. The mean transit time of indicator betweell the pulmonary and aortic valves was obtained from the dilution curves, a correction being made for the transit time through the sampling apparatus. From these measurements the blood volume of the lungs and left heart chambers was derived.In the intact dogs, cardiac output increased approximately threefold from rest to severe exercise. There was an increase of only 12 per cent to 50 per cent in PA minus PAW pressure. Thus a continued fall occurred in pulmonary vascular resistance. The blood volume of the lungs and left heart of 3 intact dogs was measured. In 2 it did not change through the range of activity, and in the third the increase with maximal exercise was 18 per cent.The dogs with ligated left pulmonary artery also showed a threefold increase in output with severe exercise. Since the entire output passed through a single lung, the effect on the pulmonary vessels was comparable to that of a sixfold increase in output in a normal dog. Despite such large flows, in 3 of 4 dogs the difference between PA and PAW pressure rose only 37 per cent to 50 per cent. The volume of blood in the lungs and left heart was unchanged between rest and 8 km./hr., and at higher speeds showed a 0 per cent to about 20 per cent increase.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

To assess the ability of an injection of Cr51-tagged red cells and one of T 1824 to measure a standard part of the total blood volume, two types of experiments have been done. First, three or four successive injections were made, separated by the sampling period of 80 minutes, in both intact and splenectomized dogs under different anesthetic regimes. The tagged cells gave total cell volumes showing no trend away from the expected value, based on the first determination and the cells lost in the sample taken, and the standard deviation was but 3.0 per cent. There was no real difference in this error depending upon the anesthesia. The T 1824 measured plasma volume tended to become progressively greater than the expected value with each injection. This trend could not be corrected out on the basis of either a plasma specific gravity or a hematocrit change. The standard deviation was three times larger than for the cell volume. Part of this variability might be related to fluctuations in dye concentration away from the bestfit slope, as were quite common at various times during the sampling period. Yet, plasma volumes based on the concentration shown at any particular time (e.g., 10 minutes) gave slightly worse agreement with the expected. The second experiment involved measurements of cell and plasma volume after three successive bleedings. Here both volumes were greater than the expected, with the standard deviation of the cell volume still less than that of the plasma volume. Curiously enough, T 1824 could follow the changes in plasma volume in these bleeding experiments a little better than it could reproduce the same volume in essentially normovolemic dogs.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Cholesterol-fed cockerels were subjected five days of each week to repetitive unavoidable shocks preceded by warning signals. The birds rapidly developed the intended conditioned emotional reaction. Comparison of these chicks with nonstressed cholesterol-fed cockerels over several months gave no iadication that this type of stress influenced weight gain, blood lipid level, or the development of atherosclerosis.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Changes in systemic vascular volume, in venous return, and in the distensibility of the venous system were studied in an experimental canine preparation. The use of an extracorporeal circulation permitted complete exclusion of the heart and lungs and allowed continuous measurement of alterations of intravascular blood volume and of venous return to the oxygenator. Brief occlusion of the venous outflow line permitted the inscription of venous pressure-volume curves. Hypotension in the isolated carotid sinuses, the administration of catecholamines or of acetylcholine resulted in venoconstriction, evidenced by a decrease in vascular volume, an increase in venous return, and flattening of the venous occlusiou curves. Conversely, carotid sinus hypertension or the administration of trimethaphan produced venodilatation, a decline in venous return, and an increase in vascular volume. The significance of these observations in the regulation of cardiac output is discussed.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Inotropic and chronotropic effects of guanethidine and bretylium have been observed in heart-lung preparations made from normal and chronically reserpinized dogs. Guanethidine (0.3 to 30 mg.) in the untreated preparation had marked positive inotropic and chronotropic effects, whereas after pretreatment with reserpine it had a striking negative inotropic effect and no effect on heart rate. Guanethidine given to preparations made from animals pretreated with guanethidine had a negative inotropic effect smaller than that seen after reserpine pretreatment. Bretylium (0.3 to 30 mg.) in the untreated preparation had both positive inotropic and positive chronotropic effects. In the chronically reserpinized animal, the positive inotropic effect of bretylium persisted though it was reduced to about one-quarter of the original size. The positive chronotropic effect of bretylium in this circumstance was reversed to a negative chronotropic effect. These effects are interpreted as indirect but strong evidence that: (1) guanethidine and bretylium exert at least part of their initial positive inotropic and chronotropic effects by a release of catecholamines; and (2) in the amine-depleted heart, guanethidine has an intrinsic negative inotropic effect, whereas bretylium has an intrinsic positive inotropic effect.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The effect was determined of changes in heart rate and of intracoronary isoproterenol, levarterenol, and epinephrine on coronary flow in the stopped and beating heart. It was possible by this means to estimate the relative action of these variables on the extravascular and intravascular resistance of the coronary bed in a heart perfused at constant pressure. As heart rate was increased extravascular resistance rose, but intravascular resistance fell to a greater extent indicating a fall in net coronary resistance. Isoproterenol had the greatest and epinephrine the least effect in decreasing the total coronary resistance. The three drugs tested caused only a small fall in extravascular resistance. Since the effect was small, it was concluded that extravascular resistance can be ignored in determining the direct effect of these drugs upon the coronary vasculature.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The distribution of Rb86Cl in the canine myocardium was determined at 20 seconds, 10 minutes, and 19 hours after administration of isotope. The uptake of Rb8620 seconds after injection is related to blood flow, and the myocardial distribution of isotope probably closely reflects the apportionment of coronary blood flow. The isotope was uniformly divided between the various regions of the left ventricle and averaged 6.4 per cent of the injected dose per 100 Gm. of tissue. This value exceeded the fractional uptake of 4.3 per cent for the right ventricle and 3.7 per cent for the atria.After 19 hours, the Rb86content serves virtually as a tracer for potassium. After this interval, the myocardial distribution of Rb86closely followed previously published reports of the relative potassium contents of the various myocardial regions.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The rubidium fractionation technique has been used to make comparative measurements of functional perfusion rates in the gastrointestinal tract of relatively undisturbed but fasted and anesthetized rats. The duodenum has the highest functional perfusion rate per unit mass of the entire digestive tract; the stomach is less than half as well perfused. The remainder of the tract to the rectosigmoid shows a progressive decrease. The small intestine shows a progressive increase in functional flow per unit mass from the pylorus to the ligament of Treitz and then a progressive decrease, most marked in the jejunum to the ileocecal valve. Blood flow values to other structures of the gastrointestinal tract are also given.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Papillary muscle strips from hypertrophied left ventricles of 17 rats were tested for tension developed in response to electrical stimulation in a perfused, oxygenated, isometric muscle chamber. The maximum tension developed was significantly greater per unit weight than that developed by papillary muscles from normal ventricles. Greater tension was also developed by the papillary muscles from hypertrophied hearts when tested with an anaerobic perfusate.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Cholesterol-fat diets are markedly more atherogenic when fed to a strain of pigeons susceptible to spontaneous atherosclerosis, as compared to a strain resistant to the disease. A breed of pigeons intermediate in susceptibility was found to be intermediate in their response to a high cholesterol-high fat diet. Serum cholesterol levels were similar among the three breeds.The White Carneau pigeons developed lesions complicated by connective tissue proliferation while the Autosexing Kings and Racing Homers developed merely “pure atheroma” or “fatty streaks.”

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID