摘要:

The effects ofdl-propranolol,d-propranolol, and ICI 46037, a quaternary analog of propranolol, on the functional refractory period and conduction time of the atrioventricular transmission system were studied in anesthetized dogs.dl-Propranolol, 0.5 mg/kg, prolonged the functional refractory period, increased the conduction time, and reduced the maximum frequency of A-V transmission. Larger doses (5 mg/kg) produced only a small additional depression of A-V transmission. In contrast, neitherd-propranolol nor ICI 46037, 0.5 mg/kg, depressed A-V transmission. Larger doses of both drugs prolonged both the functional refractory period and the conduction time, the magnitude of the response being quantitatively similar to that produced by increasing the dose ofdl-propranolol from 0.5 mg/kg to 5 mg/kg.The intravenous administration of glucagon, 2 μg/kg, promptly restored normal A-V conduction in animals that had receiveddl- ord-propranolol, but was ineffective in those which had received ICI 46037. It was concluded that propranolol depresses A-V transmission by both specific (beta-receptor blockade) and nonspecific mechanisms, the former being the more important. In addition, it appears that glucagon is capable of reversing the cardiodepressant action of propranolol on A-V transmission, a finding which may have considerable clinical importance.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

The anesthetics chloroform, halothane, ethyl ether, and sodium pentobarbital, which have negative inotropic properties, were examined for effects on the calcium pump of the sarcoplasmic reticulum of the dog myocardium. Chloroform and sodium pentobarbital, at concentrations similar to those depressing cardiac contractility, inhibited calcium uptake. The concentration of halothane required to inhibit calcium uptake was ten times greater than that required to produce depression of contractility. Ether at concentrations eight times greater than those producing inhibition of contraction was completely without effect on calcium uptake. Chloroform and halothane depressed calcium uptake and calcium-stimulated ATPase activity in parallel, indicating that these agents do not uncouple transport from ATP hydrolysis. Sodium pentobarbital, in contrast, uncoupled transport from ATP hydrolysis.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

In anesthetized dogs the intravenous infusion of arginine vasotocin, 25 mU/min, or vasopressin, 10 mU/min, inhibited renin secretion when control secretion rates were normal or when they were elevated by complete ureteral occlusion. Vasotocin, 5 mU/min, or vasopressin, 1 mU/min, was ineffective. Direct intraarterial infusion of vasotocin, 5 mU/min, into the right kidney inhibited renin secretion by the right kidney only. Glomerular filtration rate and renal plasma flow were not changed, and mean arterial pressure was either not changed or was decreased. Vasotocin caused no change in urine flow but did produce a significant natriuresis secondary to decreased tubular reabsorption. The physiological implications of these polypeptide-renal relationships are discussed.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

A radioactive isotope dilution technique, in which two radioactive tracers were used simultaneously, was employed to investigate the nature of the hepatic arterial vascular bed or arterial vascular “space” in 22 isolated perfused canine livers. The technique continuously monitored the blood leaving the liver for radioactivity so that no assumptions had to be made regarding the representative nature of samples. The concept of an arterial vascular space was defined in terms of the mean circulation time of labeled red cells through the perfused organ, and the variation of this parameter with variations in arterial flow was considered; agreement with other published work was shown. The experiments on the size of the arterial vascular space showed a linear relationship between the arterial fraction of the blood occupying the total hepatic vascular bed and the arterial fraction of the total hepatic blood flow. The evidence from these experiments supported the idea that the artery and the portal vein share a large proportion of the total hepatic vascular bed.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

A method of estimating the magnitude and distribution of umbilical blood flow by means of radioactive microspheres in sheep fetuses in utero is described. Simultaneous measurements of total umbilical flow by this method and the steady-state diffusion technique showed agreement within ±11%. In 11 fetuses of 90 to 150 days gestational age, the distribution of umbilical flow to the intercotyledonary chorion was 6.2±0.8% of the total. This information has been used to estimate the effect of venous admixture of cotyledonary and noncotyledonary blood on the umbilical vein-uterine vein concentration difference of inert molecules with flow-limited transplacental clearance.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

The lipid changes that occur in the eyes and aortas of male Dutch belted rabbits maintained on 1% dietary cholesterol for 1 to 3 months were studied. In the cornea, iris, ciliary body, and aorta, the most noteworthy lipid change was in tissue cholesterol, which increased with increased time of feeding cholesterol. The phospholipid content of all the tissues increased to a lesser extent but followed the same pattern as cholesterol with respect to time. No changes in tissue triglyceride could be detected during the experimental period. The iris had the capacity to accumulate large amounts of cholesterol. The total iridic tissue (average wet weight, 75 mg/rabbit) accumulated an average of 10.2 mg of cholesterol after the rabbit had eaten a 1% cholesterol diet for 3 months; the average increase was 14.2 mg in aortic tissue (average wet weight = 380 mg/rabbit). The severity of disease graded visually correlated with the cholesterol concentration in the cornea and aorta. Using cholesterol concentration as the criterion, no significant correlation between aortic and corneal disease was found (P>0.10), but a good degree of correlation (P<0.01) existed between the severity of iridic and aortic involvement over the 3-month experimental period.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID