摘要:

In a large series of canine heart-lung preparations, system volumes were determined by the T 1824 dye bolus teehnic of Hamilton. Results were compared with volumes independently determined by equilibration of label in a recirculating system. The mean differences of values in the largest group of experiments was 3.9 ml., and was not significantly different from zero. A small but significant mean difference in a second smaller group is discussed relative to the basic postulates of the method.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The isolated abdominal aorta was perfused in 6 cats and 2 dogs, and perfusion of the isolated superior mesenteric arterial system was performed in another 6 cats. In every experiment, wide variations in perfusion pressure produced no alterations in the systemic pressure, although it was responsive to manipulation of the carotid pressure. A comparison of the systemic pressure responses to mesenteric artery occlusion and to carotid artery occlusion prior to and following (1) high spinal transection in 2 cats or (2) venous perfusion of sodium thiopental in 3 cats showed an obliteration of the responses to carotid occlusion while the systemic response to oclusion of the mesenteric artery persisted. The results indicate that the systemic responses seen during mesenteric artery occlusion are probably caused by mechanical diversion of blood from one vascular bed to another and do not represent true reflex responses. The observations indicate that mesenteric pressure receptors do not contribute significantly to the reflex regulation of the systemic blood pressure.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Reserpine, serotonin, norepinephrine, 5-hydroxytryptophan and 3,4-dihydroxyphenylalanine had qualitatively the same cardiovascular effects when they were injected into a lateral ventricle or into the cisterna magna. All lowered arterial pressure, usually caused bradycardia despite prior section of the vagus nerves, and caused marked inhibition of the pressor response to occlusion of the common carotid arteries. Essentially the same results were obtained in unanesthetized as in anesthetized dogs. On a weight basis, norepinephrine was the more active amine tested and 5-hydroxytryptophan was more active than serotonin and 3,4 dihydroxyphenylalanine. Reserpine injected centrally had an effect equivalent to that of 20 or more times larger dosage given intravenously. All drugs were more active against the response to carotid occlusion than against the reflex pressor response to stimulation of a cut central end of a sciatic or vagus nerve. Decreased afferent electric activity of the carotid sinus nerve accompanied lowering of arterial pressure following central injection of small dosage, or intravenous injection of large dosage, of 5-hydroxytryptophan, indicating that the cardiovascular effects are not due to a direct action of 5-hydroxytryptophan on carotid sinus baroceptors.Central injection of an amine oxidase inhibitor, beta-phenylisopropylhydrazine, markedly augmented and prolonged the cardiovascular effects of the amines and of reserpine as well.These results are all consistent with, though they do not validate, the premise that the acute cardiovascular effects of reserpine are mediated centrally by serotonin and/or norepinephrine, either released from a bound and inactive to a free and active form, or formed by decarboxylation of their respective amino acids.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The hemodynamic changes following elevation of systemic arterial pressure and total systemic resistance by methoxamine were studied by right heart catheterization in 18 patients with mitral valve disease and 4 patients with no significant cardiovascular abnormality. This is the first detailed report of the circulatory effects of this drug in man. Changes in oxygen consumption, arterial oxygen saturation, stroke index and pulmonary artery to pulmonary “capillary” mean pressure gradient were insignificant. Forward cardiac index and heart rate decreased significantly while arteriovenous oxygen difference increased markedly in all groups of patients. The hemodynamic mechanisms involved in the changes observed during methoxamine infusion are discussed. Characteristic of patients with mitral insufficiency were significant increments of pulmonary arterial mean, pulmonary “capillary” mean, and pulmonary “capillary” V peak pressures. These subjects also had significantly greater increments in “left heart” resistance than patients without mitral insufficiency. An elevation of pulmonary “capillary” V peak pressure of 35 per cent or more of the elevation of systemic arterial systolic pressure was found to be a useful index of the presence of mitral insufficiency. Study of the pulmonary “capillary” pressure records during methoxamine infusion may obviate the necessity of left heart catheterization in the detection of significant mitral insufficiency.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

When coronary sinus and arterial plasma samples obtained during a period of ventricular tachycardia 8 to 11 hours after coronary ligation were analyzed for electrolyte concentrations, it was found that there was an increase in K and Mg and a decrease in Ca and Na. By comparison, when blood samples were taken from sham dogs 8 to 11 hours after the ligatures had simply been placed under the artery, no significant change in plasma cation concentrations over control values was observed. Infarcted ventricular tissue, as compared with noninfarcted tissue, contained an average of 5.1 mEq./100 Gm. wet weight more Na, 4.0 mEq./100 Gm. wet weight less K, and 1.12 mEq./100 Gm. wet weight less Mg.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

The mechanism causing renal vascular flow to vary less than proportional to changes in arterial-venous pressure gradient, was studied in isolated dog kidneys perfused with whole blood and with cell-free colloidal solutions. This autoregulation of renal flow rapidly deteriorated along with vascular reactivity to drugs when oxygenated polyvinyl-pyrrolidone-Locke solution was used for perfusion. This deterioration was prevented by the addition of plasma to the colloidal perfusate.During the first 2 seconds of suddenly raised arterial pressure, renal flow normally increased proportionately or slightly more than proportionately to the increase in arterial pressure; intrarenal venous pressure, needle tissue pressure and kidney weight rose simultaneously. During the next 4 seconds, increasing vascular resistance upstream from the intrarenal veins caused parallel reductions in renal flow, intrarenal venous pressure, needle tissue pressure and at times kidney weight. After brief rhythmical changes in prevenous segmental resistance, flow became steady to show intense autoregulation, while intrarenal venous pressure and needle tissue pressure remained relatively low.This genuine autoregulation of renal flow was abolished by cooling kidneys to 3 to 10 C, and by treatment with chloral hydrate and with procaine in concentrations rendering the smooth muscle of the renal blood vessels relatively inert to direct drug stimulants. On the other hand, at temperatures of 3 to 10 C., and usually with chloral hydrate treatment, a factitious and passive type of flow autoregulation was observed, caused by the effects of abnormally high tissue pressures.Renal flow autoregulation was not appreciably impaired by anesthetization of the intrarenal nerves by procaine in concentrations which did not simultaneously depress vascular smooth muscle reactivity. Yohimbine induced sympatholysis did not impair autoregulation, and Dibenzyline treatment to intrarenal sympatholysis depressed only slightly autoregulation of renal flow. It was not inhibited by γ-aminobutyric acid.Anoxic perfusion which did not appreciably depress the reactivity of intrarenal autonomic ganglia, impaired autoregulation moderately. The loss of autoregulation of renal flow, accompanied by vasoconstriction following severe hemorrhage in the kidney donor dog, was slowly reversible upon perfusion of the subsequently isolated kidney and was related to smooth muscle contracture within the arterial-arteriolar vasculature.It is concluded, that myogenic vasomotion in the renal arterial-arteriolar tree in response to the level of transmural vascular pressure is the fundamental cause of genuine renal circulatory autoregulation. It is furthermore suggested that the myocytes of the juxtaglomerular apparatus may act as myogenic pacemakers in the vasomotion responsible for the essentially perfect autoregulation of the normal kidney.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Results of experiments in rabbits in which the disappearance of Evans Blue labeled plasma proteins was used as a measure of vascular integrity, indicate that Dicumarol does increase the rate of loss of plasma proteins from the blood stream. This action does not occur immediately after the introduction of Dicumarol into the blood stream but requires a latent period of between 90 and 180 minutes. During this time there may actually be a decreased rate of loss from the blood.The degree of increase in the dye disappearance rate, although not directly correlated with the degree of hypoprothrombinemia, can be roughly correlated with the extent and severity of internal hemorrhage. These results tend to confirm the idea that vascular fragility, usually considered independent of vascular permeability, may in this instance be the preliminary manifestation of Dicumarol hemorrhagic diathesis.In experiments where the effect of Dicumarol on exchange of protein between plasma and the peritoneal cavity was measured, it has been found that the presence of vitamin K1in the blood in sufficient amount to completely block the hypoprothrombinemic action will also block the tendency toward increased protein exchange. Also, if Dicumarol is introduced into the peritoneal cavity rather than directly into the blood stream, the increase in transperitoneal protein exchange rate appears to be fairly proportional to the degree of hypoprothrombinemia.It is concluded that although the possibility of several independent actions of Dicumarol exists, one effecting vascular permeability and another inhibiting the elaboration of coagulation factors, it is more likely that the changes seen in vascular integrity are related to the effects of the drug on the coagulation mechanism by way of vitamin K inhibition.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID