摘要:

Arterial contractility was investigated, using spiral and ring sections of dog, cat, rabbit, rat, and human vessels. Epinephrine produced contractions of all arterial tissue tested. Histamine invariably produced contractions. The phenomenon of variable sensitivity of arterial tissue to histamine was again demonstrated. Acetylcholine caused contractions of rabbit, cat, and rat aortas, but no contraction of the dog aorta, or dog and human femoral arteries was observed. Pitressin produced contraction of the rat aorta, and dog and human femoral arteries, but not of rabbit, dog or cat aortas.Using dog vessels, a difference in activity was observed between the aorta and the femoral artery. Greater reactivity in terms of maximum rate of tension increase and tension developed was seen in the smaller systemic arteries. A pharmacologic difference with respect to the action of pitressin was discovered between the aorta and the smaller arteries. Thus, general evidence is presented suggesting that data obtained in 1 species of animal on 1 type of tissue cannot be transferred without specific proof of its validity to data obtained in other species, or even in closely related tissues of the same species.An apparent antagonistic effect of pitressin on the pressor action of epinephrine was detected.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Arterial contractility in response to various drugs was studied in media designed to alter ionic gradients of sodium and potassium across the cell membrane. Tissues were analyzed to determine the effects of these procedures on tissue electrolytes and to demonstrate any correlation between tissue electrolytes and response.It was found that the contractile responses progressively decreased in sodium-free media, disappearing in 2 to 2½ hours. A decrease in external potassium, initially caused a potentiation of response. Thereafter, a decreased response was manifested, yet contractility remained even after 7 to 8 hours in potassium free medium. Increased external potassium caused an increase in response.There was no correlation between the content of sodium and potassium and response in potassium-free solutions, but in sodium-free solutions a positive correlation between contractility and potassium content existed.Chloride appeared to exist in 2 fractions, a diffusible fraction, and a more tightly bound fraction. Calculation of the ECFV based on the bound chloride yielded values which otherwise would have been absurd.Sodium appeared to be distributed in 3 fractions; diffusible and extracellular, not diffusible over the duration of our experiments and slowly diffusible and presumably intracellular, the latter fraction being possibly capable of cation exchange.Evidence obtained does not suggest that the sodium gradient, per se, is responsible for contractility. The concentration of intracellular potassium does not influence contractility directly. However, the potassium gradient may in part determine vascular muscle contractility.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

A method is described for preparing and studying the acute effect of renal transplants on the blood pressure of the rat. In such a preparation, renal blood flow, urine flow, and blood pressure are well maintained over a period of several hours. In hypertension of less than 6 months' duration following renal ligation or desoxycorticosterone administration, the transplant consistently reduced the blood pressure and in 36 out of 44 experiments normotensive levels were achieved in 30 to 40 minutes. Exclusion of the kidney permitted a gradual restoration of the hypertension. When the blood pressure was elevated by infusions of renin or angiotensin, the blood pressure did not fall after the transplantation procedure. Introduction of kidney tissue after the hypertension had lasted for 6 months or more reduced the blood pressure in only 10 of 23 experiments, suggesting that after the passage of time irreversible vascular changes had occurred.The mechanism by which the transplant lowers the blood pressure is unknown, but such factors as the creation of an area of low vascular resistance, the release of non-specific depressor substances into the circulation, and the external loss of a pressor substance into the urine seem to be excluded. Reasons are given for suspecting that the antihypertensive action of normal kidney tissue is a specific metabolic or incretory effect, rather than an excretory action related to urine formation.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Since ventricular fibrillation is the predominate cause of death following experimental coronary occlusion, measurement of the ventricular fibrillation threshold is recommended to assess the value of cardiac revascularization procedures. This determination is quantitative, precise and permits measurement under controlled circumstances. It was dissatisfaction with measurement of mortality rate following coronary occlusion in control and experimental animals (bioassay technic) that led to the adoption of the present more exact method.Acute ligation of the anterior descending branch of the left coronary artery causes an immediate drop in the fibrillation threshold to one-fifth of normal. This is not changed if one releases the artery and retests the animal with occlusion 5 to 6 months later. Implantation of the internal mammary artery into the myocardium of the left ventricle creates a greater resistance to ventricular fibrillation after coronary occlusion. In animals in which the internal mammary artery remained patent, the fibrillation threshold remained after coronary occlusion at 85 per cent (mean) of control without coronary occlusion. This was highly significant. If the internal mammary artery was thrombosed, as demonstrated by vinyl plastic injection technics, the fibrillation threshold dropped markedly after coronary occlusion and did not vary significantly from the controls. When the anterior descending branch of the left coronary artery was permanently ligated in 1 group of dogs, the expected decline of fibrillation threshold occurred. When the survivals from this group were retested 5 to 6 months later, the fibrillation threshold had increased slightly (not statistically significant) but remained below 50 per cent of control without coronary occlusion and significantly different from the threshold of animals with patent internal mammary artery implants.The results of this investigation suggest that a greater resistance to ventricular fibrillation associated with coronary occlusion can be achieved by operative means than by either mild or severe ischemia alone.

ISSN:0009-7330    

出版商:OVID    

年代:1960

数据来源: OVID

摘要:

Ions injected into the circumflex branch of the left coronary artery of the intact dog produce sequential electrocardiographic changes different from those produced by exposure of the entire heart to these ions. Of all substances tested, the contour of the surface electrocardiogram is most sensitive to potassium. The electrocardiographic sequence of alterations produced by potassium so injected are characteristic and similar to those produced by subtotal and total occlusion of a coronary artery.

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