摘要:

One method of measurement of the nonlinearity of a vascular system is to apply a sinusoidal input perfusion flow and to examine the resultant pressures and flows at the input and elsewhere in the system for harmonic content. Unfortunately the pump may contain much higher harmonic content than will be generated by the nonlinearities in the arterial system of dogs. If two fixed flow pumps are available and can simultaneously be used in parallel to perfuse the system at two incommensurate frequenciesf1andf2, then the appearance of intermodulation frequencies, such asf1+f2,f1–f2, will provide a sensitive measurement of nonlinearity. This scheme has been used, and the recorded measurements have been reduced to power spectral density form with the aid of a hybrid computer. The most important result of these studies is that the intermodulation scheme is shown to be a very sensitive method for detecting the presence of nonlinear characteristics in the arterial system of the dog, even though the system was found to be nearly linear. This scheme also proved useful in detecting changes in nonlinearity since, when injection of norepinephrine considerably increased the mean pressure, the nonlinearity was significantly less.

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 striking increase in the plasma renin level occurred in dogs with low output right heart failure secondary to tricuspid insufficiency and pulmonic stenosis and in three of five animals with high output failure produced by a large arteriovenous fistula. When dogs with a small arteriovenous fistula were given daily injections of DOCA, the renal sodium “escape” phenomenon occurred. In these animals, the level of plasma renin was suppressed during DOCA administration both during the initial period of sodium retention and also later when sodium balance was normal or negative. In contrast, when dogs with a larger arteriovenous fistula but without evidence of cardiac failure were given DOCA, they retained sodium and developed signs of congestive heart failure. However, in these animals with congestion and ascites, in contrast to the dogs that developed spontaneous high output failure, the plasma renin was low. Renin-substrate was unaltered in all of the experimental situations studied except for the decrease observed in dogs with low output right heart failure. In these animals, it seems likely that decreased renin-substrate was secondary to hepatic congestion and liver damage. The renin-angiotensin system does not seem to be related to the “escape” phenomenon, and renin does not appear to be the factor that makes the kidney unusually responsive to mineralocorticoids. Thus, in experimental heart failure the renin-angiotensin system was activated, but in the congestive syndrome produced by DOCA the plasma renin level was suppressed.

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 field study was made of the effect of β-adrenergic receptor blockade (propranolol; Kö 592) on the racing performance of six normal greyhounds and three with chronic extrinsic cardiac denervation. Records were made of the time to race a 5/16-mile course before and after blockade; the heart rate was recorded by telemetry. After the administration of the β-adrenergic receptor-blocking agent to the normal greyhound, racing time was slightly increased, and maximal heart rate was slighdy decreased. After blockade in the cardiac denervated greyhounds, racing time was prolonged, cardiac acceleration was severely limited, and the animals finished running in a state of collapse. The data indicated diat die cardiostimulant action of both sympathetic nerves and circulating catecholamines was necessary for maximal performance. After blockade of one or the other of these mechanisms, racing performance was slightly reduced from normal. Withdrawal of both adjuvants severely limited the performance of maximal exercise.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Previous studies have attempted to demonstrate the reversibility of rabbit atherosclerosis after discontinuance of cholesterol feeding or by other measures. These attempts have been largely unsuccessful. In all the studies, atherosclerosis was induced by cholesterol feeding for several months. At the end of these prolonged periods, the animals had advanced aortic lesions. The present study sought to determine whether a shorter exposure to an elevated blood cholesterol might produce lesions that were reversible.Rabbits were fed cholesterol until their serum levels reached at least 1000 mg/100 ml; cholesterol feeding was then discontinued. Serum cholesterol values rapidly returned to normal levels. Some were killed at the time of discontinuance of the cholesterol diet and the others at periods up to 300 days thereafter. The aortas were removed and analyzed chemically for cholesterol content. The results demonstrate that cholesterol feeding of short duration produces a significant lesion whose cholesterol content may decrease markedly some weeks after the serum cholesterol has returned to normal levels.

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:

When the sympathetic nerve supply (right recurrent cardiac nerve) to a ring of the pulmonary artery of the rabbit is stimulated repetitively in vitro at frequencies of 10/second or more, the following changes occur which are not seen after stimulation at lower frequencies. (1) The minimum number of pulses in a train needed to cause a just-detectable contractile response is reduced from a mean of 7 to unity; the higher the frequency of repetitive stimulation the fewer the number of repetitive pulses needed to effect this change. (2) The basal tone of the blood vessel exhibits fairly rapid, small, spontaneous fluctuations. (3) The resting or basal tone of the vessel slowly increases for 1/2 to 2 hours. It is speculated that changes 1 and 2 may be the result of an irreversible change in transmitter storage or release mechanisms.

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:

Combination of a histochemical fluorescence method for biogenic monoamines and staining of juxtaglomerular cell granules demonstrated sympathetic nerve terminals in the rat kidney in the walls of the parts of the juxtaglomerular arterioles that contain granulated cells. This forms a morphological basis for a direct influence of sympathetic nervous activity on the liberation of renin. The juxtaglomerular granules were nonfluorescent, an indication that, in the rat, the granulated juxtaglomerular cells are not equivalent to mast cells.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID