摘要:

In an effort to produce a preparation for the study of sodium excretion in chronic left heart failure a graft anastomosis was created between the left subclavian artery and the left atrium in five dogs. This resulted in chronic progressive elevation of left ventricular end diastolic and left atrial pressures. Maximal left ventricular end diastolic pressures ranged between 18 and 30 mm Hg, 10 to 20 weeks postoperatively. There was only a slight rise in right ventricular diastolic pressure and no clinical evidence of right heart failure.Cardiac outputs remained within normal limits in all animals. Serial electrocardiograms disclosed the development of left ventricular hypertrophy and left ventricular hypertrophy and dilatation were observed at postmortem examination. One dog which survived with a patent shunt for more than a year had right as well as left ventricular hypertrophy but no right heart failure. Glomerular filtration rates, renal plasma flow and excretion of rapidly infused isotonic saline remained unaltered even at the highest levels of left ventricular end diastolic pressure. Although the development of left and eventually right ventricular hypertrophy, the chronic and progressive elevation of left ventricular end diastolic, mean left atrial and pulmonary arterial pressure, with only slight elevation of right ventricular end diastolic pressure, were regarded as characteristic features of isolated left ventricular failure, the propriety of this term may be questioned in view of the unaltered cardiac output and renal hemodynamics. But the observations do indicate that marked elevation of left ventricular end diastolic and presumably pulmonary venocapillary pressure, such as occur in left heart failure, do not impair renal excretion of sodium.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The transmyocardial temperature gradient was measured in both right and left ventricles and in the septum of the dog by percutaneous ventricular puncture, using a no. 21 thin-wall needle fitted with a thermocouple stylus. The outer half of the left ventricular myocardium was invariably warmer than the endocardium. The peak temperature of the right ventricle was located midway between the endocardium and epicardium. The midseptal region was found to have a higher temperature than either its right or left endocardial aspects. The left ventricular cavity was cooler than the right ventricular cavity by a mean of 0.1°C.The transmyocardial temperature gradient was measured successfully in the left ventricle of two patients with cardiac disease. As in the dog, the outer layers of the myocardium were warmer than either the endocardium or cavity in these two patients. In one patient the T waves in the left precordial leads were negative and in the other the T waves were upright in the same lead.The location of peak temperature consistently in the outer half of the left ventricular wall may partly explain the normal upright T wave and may contribute to a more rapid recovery in the outer layers of the ventricle compared with the inner layers. However, reversal of the T wave must be explained by other factors and it is apparent that the polarity of the T wave is not governed exclusively by the transmyocardial temperature gradient.The transmyocardial temperature gradient may be explained partly on the basis of differences in heat removal by blood flow in the coronary system as well as in the ventricular cavity. The latter was found to be an important factor, because during ventricular fibrillation the transmyocardial temperature gradient was abolished.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Simultaneous recordings of isometric tension and muscle membrane potential have been made in the sympathetic nerve-pulmonary artery preparation of the rabbit. The mean resting membrane potential recorded intracellularly was 51.5 mv. Sympathetic nerve stimulation andl-norepinephrine caused contraction without change in the membrane potential and in the absence of action potentials. Increase in extracellular potassium initiated both depolarization and contraction, although these two processes exhibited different latencies and time courses. The significance of these findings is discussed in relation to recent findings of dissociation in smooth muscle between contraction and membrane potential changes.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

1. Human myocardial blood flow has been measured by the determination of precordial radioactivity after the injection of solutions of radioactive gas directly into the coronary arteries following coronary arteriography.2. The accuracy of radioactive gas measurements has been established in dog experiments by comparison with coronary blood flow simultaneously measured by rotameter.3. This method has two major advantages over the existing methods of measuring human myocardial blood flow. Firstly, the right and left coronary circulations can be studied separately, this being the only method whereby the right circulation can be studied in man. Secondly, anatomical and physiological correlations are readily available as arteriography is an essential feature of the method.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The object of these experiments was to evaluate the hydrostatic pressure and hydraulic permeability of the tooth pulp in situ. A small hole was drilled through the enamel and dentin to the dentinal-pulpal junction in canines and third incisors of anesthetized dogs. A threaded cannula filled with mammalian Ringer's solution was screwed into the hole and connected to a microsyringe and a pressure transducer of very low compliance.Pressure was recorded when the cannula was first inserted into the hole; then small amounts of fluid were injected into the system or withdrawn from the system using the micro-syringe. The equilibrium pressure (Peq), measured after transients had disappeared, was fairly constant for a given tooth over long periods of time. Referred to tooth level (which was approximately heart level),Peqaveraged 57 mm Hg (range 38 to 78 mm Hg) in the ten teeth tested. Superimposed upon the steady value was a random deviation (± 3 mm Hg), a hysteresis effect resulting in a higher pressure if the measurement had been preceded by injection of fluid rather than withdrawal (± 3 mm Hg), and a continuous drift with time ( + 3 mm Hg/hr).The hydrostatic permeability was calculated from the rate of fluid flow when the pressure was above or below its steady state value. When the pressure was high (fluid being forced into the pulp) flow averaged about 0.33 μl/hr-mm Hg over the rangePeqtoPeq+ 20 mm Hg. When the pressure was low (fluid being withdrawn from the tooth), flow averaged about 0.14 μl/hr-mm Hg over the rangePeqtoPeq− 20 mm Hg.It is concluded thatPeqprobably represents the true hydrostatic tissue pressure normally existing within the tooth pulp. This implies a high capillary pressure and thus a relatively high resistance in the venous side of the pulp circulation. The interpretation of hydraulic permeability is not certain, but this quantity probably is related to the ease with which fluid passes into or out of the pulp capillaries.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Conditions under which an apparently non-propagated atrial (concealed) response facilitated the passage of a subsequent response to the ventricle are described. Analysis of the time relations of atrial and ventricular events suggest that the apparent facilitation results from a dissociation of two pathways through the A-V node.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Renin secretion was found to be controlled by a renal baroreceptor rather than by ischemia. Development of a sensitive assay technique that detects renin in small quantities of renal venous and peripheral arterial plasma has permitted the demonstration that the rate of renin secretion varies inversely with the level of arterial pressure independently of renal blood flow.When mean renal perfusion pressure was reduced 5 to 40 mm Hg by a constricting band around the aorta above the level of the renal arteries, increased renin secretion commenced within 60 seeonds. Reductions of this magnitude did not necessarily cause mean perfusion pressure to fall below control levels of diastolic perfusion pressure. Rises in perfusion pressure had the reverse effect, reducing the rate of renin secretion again without measurable change in renal blood flow. Compression of the kidney within an oncometer by an applied forece of from 15 to 40 mm Hg also caused increases in the rate of renin secretion in the absence of change in total renal blood flow. Reduction of pulse pressure alone did not provoke secretion of renin, nor did reduced oxygen tension, or renal ischemia. Rise in perfusion pressure due to occlusion of the common carotid arteries was associated with reduction in the rate of renin secretion.A small amount of renin was secreted continuously under the conditions of these experiments; physiologic changes in mean perfusion pressure served to alter the rate. This suggests that a renal baroreceptor mechanism regulates renin secretion under normal circumstances and that arterial pressure tends to stabilize at a level at which renin secretion is minimal.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

1. Electrograms have been recorded simultaneously from the right atrium, bundle of His, and both ventricles, together with the lead II electrocardiogram in dogs receiving cyclopropane and oxygen. Following the administration of norepinephrine, both bigeminal rhythms and monofocal ventricular tachycardias were observed.2. In our studies both the coupled and the monofocal ventricular beats originated distal to the His electrode.3. The mechanism of the coupled beats could not be analyzed using either gross or intracellular recording methods; the monofocal tachycardias appeared to result from increased pacemaker activity in the ventricular conducting system.4. The present results emphasize the hazards of proposing mechanisms to explain arrhythmias solely on the basis of electrocardiographic evidence.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

In the June 1964 issue (volume XIV, no. 6, page 519) graphs above the words Figure 3 and Figure 4 are transposed. The graph, headed EXP. 1-11-63, EPINEPHRINE, placed by mistake at top of page, left, should have appeared at lower right of same page, over the designation Figure 4 and legend. Conversely the graph headed EXP. 1-16-63(B), L. STELL. STIM., placed by mistake at lower right of page 519, should have appeared at upper left of same page over the designation Figure 3 and legend. In summary the figure numbers and legends were correctly placed but the graphs were transposed.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The disappearance of exogenous adenosine from blood is principally due to its degradation into inosine and hypoxanthine by the enzymes present in the erythrocytes. In the presence of intact red cells, Persantin (RA-8 or 2,6-Bis (diethanolamino) -4,8-dipiperidinopyrimido-(5,4-d)-pyrimidine) effectively prevents the disappearance of adenosine. Although Persantin inhibits adenosine deaminase its adenosine-sparing action in whole blood is more likely due to a reduction in permeability of the red cell membrane to adenosine. This property of Persantin makes possible its use as a tool in investigation of the role of adenine nucleotide derivatives in the regulation of the coronary circulation.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID