ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Experimental coarctation of the aorta has been produced in rats. Animals with the clip above both renal arteries have been compared with animals with the clip below both renal arteries and with dummy operated rats. The fore- and hindlimb blood pressures, heart weights and perfusion pressure, and norepinephrine responses of the isolated perfused hindquarters have been measured.Only the animals with a clip above the renal arteries developed hypertension and hypertrophy of the heart. The increase in blood pressure was progressive, requiring about 10 days to reach hypertensive levels. Such animals showed an increase in the norepinephrine responses and in the perfusion pressure of hindlimb blood vessels when compared with either of the other two groups. The differences are statistically significant. In rats with clips above the renal arteries, there is a highly significant regression line of hindlimb norepinephrine responses on hindlimb perfusion pressure and of either of these values on heart weight.It is considered: (a) that the hypertension in experimental coarctation of the aorta is not purely mechanical and the kidneys are essential for the development of this type of hypertension; and (b) that the increase in the norepinephrine responses and in the perfusion pressure found in the hindquarter vascular bed of rats with coarctation of the aorta above the renal arteries is not secondary to the hypertension as such, but in some way is related to the mechanism that produces the hypertension in experimental coarctation of the aorta.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

DNP (2,4 dinitrophenol), in concentrations of 2 to 5 × 10−5M produced changes in transmembrane action potential in both the Purkinje and ventricular muscle fibers of the isolated perfused hog heart; however, the time of initiation and rate of change of the different phases of the action potential in the two fibers varied. In the Purkinje fiber, the earliest and most pronounced alteration was a loss in overshoot resulting in a decrease in amplitude of the action potential. Shortly thereafter, the action potential duration shortened, and membrane resting potential decreased. In the ventricular muscle fiber, the earliest and most prominent change was a shortening of action potential duration. This was followed by loss in overshoot and decrease in amplitude of action potential. The membrane resting potential declined but was not significantly different from that noted in Purkinje fiber. The changes in both fibers were reversed completely by washing with Tyrode's solution. The earlier and more pronounced shortening of action potential duration in ventricular muscle fiber as compared to Purkinje is attributed to a greater need of the former for metabolic energy. It may also be conjectured that the greater shortening of action potential duration in ventricular fiber is due to a more marked inhibitory effect of K+influx by 2,4 dinitrophenol in this fiber with the K+influx coupled to metabolic energy. To account for the more enhanced loss in overshoot in Purkinje fiber, it is suggested that 2,4 dinitrophenol has a greater modifying effect on Purkinje fiber membrane or on its Na+carrying system. This results in an earlier and more pronounced decrease in Na+influx in this fiber as compared with ventricular muscle fiber.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Changes in blood pressure and the electrocardiogram were studied before and after the stimulation of the hypothalamus (anterior, lateral, and posterior) and the reticular formation of the pons in anesthetized cats.The stimulation of the anterior hypothalamus produced a rise of blood pressure and usually bradycardia; tachycardia was rarely observed. Arrhythmias were not observed, and the electrocardiographic changes consisted only of slight ST elevation and deepening of the T waves. Stimulation of the lateral hypothalamus produced a rise in blood pressure of a lesser magnitude than that of the anterior hypothalamus but was associated with a transitory phase of A-V dissociation and frequent premature systoles. Stimulation of the posterolateral hypothalamus resulted in the same rise in blood pressure as that of stimulation of the lateral hypothalamus and was accompanied by nodal rhythms, aberrant ventricular conduction, and fusion beats. Stimulation of the reticular formation produced a rise in blood pressure similar to stimulation of the lateral and posterolateral hypothalamus and was associated with slight tachycardia, widening of the QRS complexes, transitory A-V dissociation with nodal escapes and ectopic beats of ventricular origin, and fusion beats.These findings suggest that: (1) the hypothalamus serves as a pathway for cardiac neurovegetative stimuli, probably via the reticular formation, producing predominantly sinus node depression; (2) the posterolateral hypothalamus and reticular formation have similar functions in the production of cardiac arrhythmia.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The circulating splanchnic cell and plasma volumes were measured with the regional dilution technique in splenectomized dogs under sodium pentobarbital. For a 10-kg dog, the average circulating splanchnic cell volume is 56 (SEm= 5.0) ml and the average circulating splanchnic plasma volume is 98 (SEm= 7.2) ml. These values represent 20% of the total plasma volume respectively. The splanchnic cell percentage, averaging 36.3% (SEm= 1.32%), is significantly lower than the large vessel cell percentage (average 42.4%) and is almost equal to the overall cell percentage. The splanehnic Fcellsvalue averages 0.86 and is almost the same as the overall Fcellsvalue. Therefore, the splanchnic circulation contains a portion of the total “extra plasma” in proportion to the blood volume in this region. The splanchnic mean circulation time of the plasma (average 42 seconds) is significantly longer than that of the cells (average 33 seconds).

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

After the subcutaneous injection of histamine (3 mg/kg), changes in splanchnic and systemic circulation were studied in splenectomized dogs under sodium pentobarbital. The estimated splanchnic blood flow (BSP clearance and extraction) decreased by 67%. The extent of the decrease was almost the same as that for the mean arterial pressure; thus the splanchnic vascular resistance remained unchanged. This unchanged splanchnic resistance was ascribed to a combination of arteriolar dilatation and hepatic venoconstriction, and the latter was indicated by the increase in the wedged hepatic venous pressure in the face of a decreased flow. The ciculating splanchnic blood volume (equilibration technique) was not significantly changed after histamine, but there was a decrease in the splanchnic cell percentage. Therefore, the evidence indicates that during histamine shock there was a shift of blood from the hepatic veins to the capillaries, rather than a pooling of blood in the splanchnic circulation. The decrease in the splanchnic cell percentage was about the same as the decrease in the overall cell percentage. The venoconstriction in the hepatic circulation and probably also that in the other circuits contributed to a reduction in venous return. The cardiac output (indicator dilution method) decreased by an average of 51%. The total peripheral resistance decreased by an average of 39%. The drastic and persistent arterial hypotension in histamine shock was due to decreases in both the cardiac output and the peripheral resistance.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The resistivity of tissues of the thorax of dogs has been measured in situ under nearly normal conditions. Additional data have been obtained from humans.Approximate values of tissue resistivity found are 160 ohm-cm for blood, 2,000 ohm-cm for lung, 2,500 ohm-cm for fat, 700 ohm-cm for liver, 250 and 550 ohm-cm (anisotropic) for heart muscle and 150 and 2,500 ohm-cm (anisotropic) for skeletal muscle. Reasons for the differences between these and previously reported values have been found, and in some cases, verified experimentally. Predictions of whole trunk resistivity based on anatomical data and these measurements are within 8% of actual trunk measurements.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Electrocardiograms were recorded by needle electrodes in 137 of 166 rabbit fetuses at 10½ to 31 days. Invariably, electrocardiograms were obtainable from the 12th day on, which in the rabbit is an early stage of development. The earliest electrocardiogram was obtained at 10 days, 22 hours, corresponding to about five weeks in human development. Sinus rhythm was evident from the start. The wave form consists of a pair of complexes 50 to 200 msec apart. The first complex is quite variable but appears to be atrial in origin; the second is surprisingly constant and appears to be ventricular.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

It is known that the cardiac necroses produced by 9α-fluorocortisol (F-COL) plus Na2HPO4are prevented by the administration of chlorides or potassium salts. In this paper it is shown that various chlorides not only significantly correct the depletion of myocardial potassium elicited by F-COL + Na2HPO4but increase the potassium concentration in the heart of normal animals.In view of these facts and of earlier experiments that have shown that F-COL alone diminishes cardiac potassium without producing necrosis, it is concluded that the depletion of potassium is necessary, but not sufficient, for the development of infarctoid cardiopathy and that the protective electrolytes (chlorides and potassium salts) act through the correction of this abnormality of the potassium level in the heart.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The use of I131antipyrine for determining coronary blood flow in intact dogs is described. The correlation with the simultaneous nitrous oxide method was 0.91 ωm0.22. Partition coefficient and tissue equilibration were directly determined (1.04 ω 0.13). The method as applied requires only two minutes of sampling and is adaptable to direct writing methods.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID