摘要:

A method has been developed for characterizing quantitatively, and for removing from indicator dilution curves, the distortion introduced by catheter sampling systems.The method involves a specially constructed cuvette and analog computer analysis of the curves recorded by densitometers placed at the entrance of the catheter and at points downstream.This method of correction of distortion is based on a general theory of function transformation which is applicable to all situations and not upon empirically established constants which are only valid in special situations.The geometry (coiling, bending) of the catheter has been found to affect the distortion. Disruption of the flow pattern by insertion of a braided wire in the lumen causes less variation of the distortion caused by bending and coiling.Distortion was not significantly affected by change in blood temperature in our system.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Aortic preparations of 70 rabbits including the vasa vasorum were perfused in vitro by oxygenated saline under a pressure of 100 mm Hg. The main branches of the aorta were ligated and the perfusate, which irrigates the aortic lumen, but not the vasa vasorum, was sampled every minute. The samples were assayed for thromboplastic activity by means of the calcium clotting time. The calcium clotting time was shortened significantly in samples taken one, two, and three minutes after injection of 0.005 μg epinephrine. The response was present in perfusing with Tyrode's solution as well as with 0.9% NaCl but was absent if oxygen was withheld from the solution. Larger dose of epinephrine (0.05 μg) caused an initial shortening of the calcium clotting time, followed by a prolongation in two out of five cases. Still larger doses (0.5 μg) or much smaller ones (0.0005 μg) were without effect.In the aortas of rabbits which were pretreated by 5 mg/kg of nialamide two hours before removing the aorta, the previously mentioned effect of epinephrine was prevented. However, direct perfusion of the aortic preparation by a nialamide mixture in vitro did not prevent the release of thromboplastic active substance by epinephrine.Norepinephrine in doses of 0.005, 0.05, and 0.5 μg was found to be ineffective. These observations may explain the effects of epinephrine on the clotting time of blood originally described by Cannon and Gray.5

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Hypopotassemia was produced in dogs by hemodialysis or by intravenous administration of glucose with insulin. Both methods resulted in a similar decrease in plasma K concentration and similar ECG changes although K was withdrawn from the cells during dialysis while it entered the cells during glucose-insulin infusion. The maximal plasma K decrease occurred after two hours of dialysis or glucose-insulin infusion; administration of glucose-insulin after dialysis resulted in no further plasma potassium decrease. However, dialysis after glucose-insulin infusion caused further lowering of plasma potassium. The ECG changes were evaluated in relation to changes in plasma K concentration. The most consistent effects of hypopotassemia were in decreasing order: increased duration of the QRS complex, increased duration of the QTcinterval and increase in amplitude of the P wave. Correlation coefficients (R) between these ECG changes and the plasma K decreases were of the order −0.48 to −0.54. The ECG changes failed to show even a weak correlation with absolute plasma K concentrations or with calculated changes in intracellular K.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The influence of acute changes in systemic hemodynamics on the rate of oxygen utilization by the left ventricle has been studied in intact anesthetized dogs. Certain types of hemodynamic changes caused reproducible alterations in the relationship between oxygen consumption of the left ventricle and its external mechanical work. The relationship of left ventricular minute oxygen consumption to the product of mean systolic aortic pressure and systolic ejection period per minute was constant over an extreme range of varied types of hemodynamic alterations. Changes in oxygen consumption were proportionately less than concomitant changes in heart rate. These findings are in accord with previous studies of isolated heart preparations.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

1. A group of weanling rats was made anemic by an Fe- and Cu-deficient diet consisting of cow's milk. An appropriate control group receiving Fe and Cu in addition to milk was also studied. After 86–105 days, the rats were sacrificed; hematocrit levels, heart weights, DNA, RNA, and protein concentrations were determined. Total DNA, RNA, and protein contents of the hearts were calculated.2. Statistical analysis showed a significantly increased mean heart weight, decreased DNA concentration, increased RNA to DNA ratio, and increased total RNA and protein content in the hearts of the anemie group of rats versus the control rats. There were no statistically significant changes in RNA concentration or total DNA content of the hearts.3. These data are interpreted as showing that the predominant cellular change in cardiae enlargement in the rat with dietary Fe-and Cu-deficiency is that of increase in size of the myocardial cell.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The techniques of macro- and micro-tissue clearance were used to study reactive hyperemia. Clearance of radioactive iodide from gross injection sites in muscles of rabbits and clearance of micro-injected diffusible dye from the exposed, directly observed spinotrapezius of rats gave evidence for an exact quantitative repayment of effective blood flow debt. In both types of preparation a subnormal clearance followed a thermally induced hyperemia as an apparent compensation. The exact quantitative repayment and compensation support the hypothesis that local effective blood flow is in a steady-state relation to the local concentration in tissue fluid of some agent with vasodilating properties.It is suggested that an extension of this method to studies of vasodilatation induced by drugs or other chemicals might offer an approach to identification of the normal vasodilator, and to physiological proof of its exact nature.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Measurements were made of simultaneous pulmonary artery wedge (PAw) and left ventricular diastolic (LVed) pressures 39 times during 21 venous and left ventricular cardiac catheterization studies in eight animals with brisket disease. Each animal was studied during the acute phase of the disease. The remaining 13 studies were carried out in six animals at various intervals during spontaneous recovery from pulmonary hypertension and heart failure. A pressure gradient between PAwand LVed(δP) which averaged 14.6 ± 1.6 (SE) mm Hg was demonstrated in 12 measurements during seven studies in four animals (group A). The δP in 27 measurements during 14 studies in six animals averaged 2.4 ±0.8 mm Hg (group B). Venous resistance (Rv) represented 39±5% of the total resistance (RT) of pulmonary vessels in group A and 13±4% in group B studies. The δP and Rv/RTin group A animals are consistent with findings caused by pulmonary venous obstruction. The obstruction was interpreted to represent the effect of pulmonary venoconstriction.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The intracranial pressures of conscious, lightly anesthetized and fully anesthetized dogs were altered by means of previously implanted intraventricular cannulas, while systemic arterial pressures were simultaneously measured. One vertebral artery was occluded in all these experiments by the catheter used to record aortic pressure. Increased intracranial pressure, which probably acts by reducing cerebral blood flow, caused a rise in systemic arterial pressure whose magnitude depended on the presence and depth of anesthesia. When anesthesia was not used, but when the animals were resting quietly, a significant pressor response occurred within the physiological range of CSF pressure. The response was typically of slow onset, developing over a period of one half to two minutes. It was reproducible, but tended to diminish gradually in the course of several hours if the experiment was continued, although it could be restored if CSF pressure was further increased.The pulse rate tended to increase slightly, or remain the same, providing CSF pressure was not increased too greatly or too rapidly. Respiratory effects were variable, but most commonly a slightly increased rate and depth of respiration occurred at first, with a return towards normal as the systemic arterial pressure rose.Similar responses were seen during bilateral artery occlusion, by means of previously implanted inflatable cuffs, in dogs whose carotid sinuses had been excised. These effects were also slow in onset, and were accompanied by comparable respiratory changes. In anesthetized animals with intact carotid arteries, bilateral vertebral artery occlusion produced negligible pressor effects, but was found to augment the response to increased intracranial pressure.Observations in four dogs with chronic experimental renal hypertension did not reveal notable differences, except that these animals may be less sensitive than normal to increases in intracranial pressure.The results of these experiments are compatible with the hypothesis that basal systemic arterial pressure during sleep in some degree depends on the cerebrovascular resistance, although it will be important to determine the nature of the slow adaptation seen in these experiments. If this adaptation is brought about by compensatory cerebral vasodilation, this investigation is in accord with the concept of Dickinson and Thomson that some forms of chronic high blood pressure in man might be initiated by cerebral artery occlusion or narrowing of sufficient severity and extent to prevent adequate compensatory vasodilation.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Phasic flow in the canine septal artery was recorded with an orifice meter supplied by pulsatile aortic pressure. Flow patterns were recorded when right ventricular pressure was normal and contrasted with those following elevation of right ventricular pressure in order to minimize the dynamic effect of the superficial component of the artery. Results indicate that elevation of right ventricular pressure increases the early systolic backflow, largely prevents mid-systolic forward flow, and accentuates early diastolic flow. It is suggested that this pattern does not represent that in arterioles in deep layers of the myocardium.In other experiments the septal artery was perfused through an orifice meter at variable pressures to determine the pressure required to negate mid-systolic flow at high right ventricular pressures. The results indicate that pressures considerably above aortic or right ventricular systolic pressures are required to generate forward mid-systolic septal flow.The mean septal flow was quantitated in terms of total common left inflow. It was found that an average of 16.0% of common left flow enters the septal artery. The significance of this has been discussed in terms of its relationship to the venous drainage of common left coronary arterial inflow.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID