bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dimensions of Blood Vessels from Distributing Artery to Collecting Vein
Authors: WIEDEMAN MARY P. 
Published: June 2012

Measurements of lengths, diameters, and numbers of post-capillary vessels were made in the bat's wing. The cross-sectional area and capacity in the various portions of the vascular bed were calculated.
The greatest total cross-sectional area in the entire vascular bed was found in the venules, a result not in agreement with similar reports made by others using measurements from vessels in fixed preparations. This discrepancy probably results from disagreement regarding the diameter of capillary vessels.
Calculations to determine the per cent of total volume in each portion of the vascular bed showed that the venous system accounts for as much as 80% of the total vascular volume.
Hemodynamic Correlates of the Various Components of the First Heart Sound
Authors: SHAH P. M. , MORI M. , MACCANON D. M. , LUISADA A. A. 
Published: June 2012

Previous studies in this laboratory having demonstrated that AV valve closure is not directly responsible for the rapid vibrations of the first heart sound, the mechanism of production of this "sound" was studied further in 30 experiments in dogs. The experiments were performed with multiple pressure catheterization, and intracardiac phonocatheterization, and were compared with external phonocardiograms and electrocardiograms. In 10 experiments, the first derivatives of the left and right ventricular pressures were also recorded. In four experiments, direct epicardial and arterial sound tracings were obtained.
These experiments revealed that three groups of vibrations, or components, were often visible in the external phonocardiogram, and in intracardiac and epicardial tracings. The first component follows the onset of left ventricular pressure rise and closure of the mitral valve but coincides with the rapid rise of the first derivative of LV pressure. The second component has no relationship with right heart events, occurs before aortic valve opening, and coincides with the sudden change of course of the first derivative of LV pressure. The third component occurs slightly after aortic valve opening, and seems related to sudden increase of aortic wall tension. It is probably the physiological equivalent of the aortic "ejection sound." Thus, the first two components are both left ventricular in origin while the third is of aortic origin.
Theory of Use of Indicators to Measure Blood Flow and Extracellular Volume and Calculation of Transcapillary Movement of Tracers
Authors: ZIERLER KENNETH L. 
Published: June 2012

For indicators or tracers injected into the vascular system and sampled at some other portion of the vascular system, the indicator dilution curve supplies a measure of blood or plasma flow through the system even if the indicator is not confined to the blood vessels, providing only that it eventually all return to the circulation prior to the sampling site.
Mean transit time of the indicator through the system multiplied by the measured flow determines the volume through which the indicator is distributed. This volume is independent of capillary permeability to the indicator if the indicator enters interstitial fluid at all.
Of indicator coursing through the vascular system, the fraction crossing capillaries into interstitial fluid is inversely proportional to the mean transit time of the indicator across capillaries, through interstitial fluid and back into capillaries. The constant of proportionality is the ratio of interstitial fluid volume to plasma flow through the system.
The fraction of a substance crossing capillary walls and returning can be calculated if the frequency function of transit times into, through and out of interstitial fluid can be measured. The equations cannot be solved if this frequency function is not measured.
However, because this frequency function falls to zero much more slowly than other frequency functions through which tracer concentration is apt to be convoluted, capilary permeability may be estimated graphically. The graphic estimate applies even to substances that do not return completely to the vascular bed.
Hydrodynamics of Aortic Blood Flow
Authors: FREIS EDWARD D. , HEATH WILLIAM C. 
Published: June 2012

A thermistor was used to record the temperature at regular intervals across the aortic diameter of dogs during the continuous infusion of cold indicator solution at various upstream locations. The results showed that the indicator mixed across the greater part of the diameter of the aorta in the ascending portion and proximal half of the arch but maintained a more streamlined pattern in the distal portion of the arch and descending thoracic aorta. These observations were confirmed by cineangiography. When two thermistors were located in different positions in the aortic root, and when cold saline was injected suddenly in their vicinity, the temperatures recorded by the two thermistors equalized immediately following the onset of systole. Sound waves also were detected during the systolic interval in the ascending but not in the descending aorta.
These findings are consistent with the presence of disturbed, but not necessarily turbulent flow in the ascending aorta; and with predominantly streamlined, but not necessarily completely laminar flow in the descending portion. The factors producing disturbed flow in the aortic root and the transition of flow to a more streamlined pattern in the descending portion are discussed in hydrodynamic terms.
It is postulated that during systole the blood ejected into the aorta separates from a slower moving boundary layer near the walls and at the edges of the valve cusps. This separation produces disturbed flow and mixing in the entering jet. While the thin layer adjacent to the walls as well as stagnant areas behind the valves do not fully mix with the central stream, they represent a relatively small proportion of the total aortic blood flow. Additional mixing is produced by the prominent backflow in early diastole and by the branchings of the coronary and brachiocephalic arteries.
Measurement of Local Blood Flow with Hydrogen Gas
Authors: AUKLAND KNUR , BOWER BRUCE F. , BERLINER ROBERT W. 
Published: June 2012

When a platinized platinum electrode is polarized at the potential of the standard calomel electrode, the current generated is proportional to the concentration of dissolved hydrogen gas. The effects of physiological variations in oxygen tension, pH, temperature, and ascorbic acid concentration were found to be negligible. Although absolute calibration in vivo is not possible, the rate of tissue hydrogen saturation or desaturation can be measured by needle-shaped electrodes inserted into the tissue. Arterial and venous concentration can be measured with catheter electrodes. Solubility of hydrogen gas in kidney slices was found to be the same as in blood. With the assumption that tissue is in instantaneous diffusion equilibrium with local venous blood with respect to hydrogen, the local blood flow per volume of tissue can be calculated according to the Fick principle from the rate of tissue desaturation when arterial concentration is lowered to zero.
The method was tested on dogs in myocardium, kidney, and skeletal muscle. Hydrogen was administered by respiration or by intra-arterial infusion of hydrogen-saturated saline, giving an arterial concentration of 3% to 5% saturation. Tissue desaturation curves were recorded simultaneously from two to three tissue electrodes. Good agreement with flow measured simultaneously with other methods was obtained in myocardium and renal cortex, while the data on skeletal muscle do not permit any definite conclusion. The main virtue of this method lies in the fact that repeated measurements of local blood flow can be obtained without access to arterial or local venous blood. Reliable measurements of regional blood flow were also obtained from continuously recorded venous desaturation curves, which also provide information on the distribution of blood flow.
Contribution of Baroreceptors to the Control of Renal Function
Authors: GILMORE JOSEPH P. 
Published: June 2012

Electrical stimulation of the left stellate ganglion of the dog is associated with an increase in urine flow, in electrolyte and total solute excretion, and in the renal clearance of inulin. These changes appear rapidly, are well maintained during prolonged stimulation, and stop soon after stimulation has ceased. The hemodynamic responses associated with these changes are an increase in arterial pulse pressure, an increase or no change in mean arterial blood pressure, and a decline in mean left atrial pressure. The diuretic response to stellate ganglion stimulation is diminished, but not abolished, by bilateral cervical vagotomy as are the changes in electrolyte excretion, total solute excretion, and the renal clearance of inulin. However, the hemodynamic responses are not greatly modified by cervical vagotomy. Vagotomy just above the diaphragm does not appear to modify these responses. The effect of vagotomy on the renal responses to stellate stimulation appears to be a result of sectioning baroreceptor afferent nerves which traverse the vagus nerves. The rapidity of the renal response to stellate stimulation, its temporal relation to the hemodynamic changes, and the effect of cervical vagotomy indicate that the diuresis is, to a large degree, secondary to withdrawal of renal sympathetic vasoconstrictor nerve discharge. The similarities between the renal responses to stellate stimulation and to intravenous infusions indicate that infusion diuresis may be mediated, at least in part, by the same mechanism.
When renal blood flow is measured directly in the perfused kidney, carotid occlusion is associated with little change or with a decrease in renal blood flow at a time when renal arterial pressure increases. When renal blood flow is maintained constant in the perfused kidney, carotid artery occlusion is associated with an increase in renal arterial pressure. The intrarenal administration of the adrenergic blocking agent, phenoxybenzamine, can prevent the increase in renal vascular resistance during carotid occlusion indicating that it is due to an adrenergic mechanism. The renal pressure-flow curve is displaced down and to the right during carotid occlusion; autoregulation of renal blood flow is still observed, although at a lower level of blood flow. All these changes indicate that the primary renal response to carotid occlusion is vasoconstriction mediated by the renal sympathetic nerves.
It is well-known that urine flow increases when renal arterial pressure is increased independent of a change in the activity of the renal vasoconstrictor nerves and independent of a change in renal blood flow. Consequently, the rise in arterial pressure associated with carotid occlusion can contribute directly to the response of the kidney to carotid occlusion. The variability of the changes in water and electrolyte excretion by the kidney during carotid occlusion may represent a varying contribution of direct and reflex mechanisms to the total response.
Structural Basis for the Static Mechanical Properties of the Aortic Media
Authors: WOLINSKY HARVEY , GLAGOV SEYMOUR 
Published: June 2012

The arrangement and interrelation of the structural components of the rabbit aorta were studied by light and electron microscopy. Segments of abdominal aorta were restored to in vivo length and fixed in formalin or osmic acid while intraluminal pressures ranging from 0 to 200 mm Hg were maintained by a constant pressure perfusion apparatus. Transverse, longitudinal, and tangential sections of vessels fixed at various distending pressures were examined. Micrometric measurements included vessel diameters and wall thickness, thickness and waviness of elastin lamellae and interlamellar distances.
With increasing pressures below the diastolic value, aortic radius increased and wall thickness decreased rapidly. Waviness of the tubular elastin lamellae decreased uniformly throughout the wall. Interlamellar distances decreased uniformly and markedly. Lamellar thicknesses decreased uniformly but much less than interlamellar distances. A fine fibrillary elastin network connected the thick lamellae. Collagen fibers showed no definite pattern of orientation.
At and above diastolic pressure radius and wall thickness changed little with increasing pressures. Elastin lamellae were straight and interlamellar distances were uniform; the fibrils of the interlamellar elastin net were arranged obliquely. Collagen fibers were arranged nearly circumferentially. Collagen and elastin fibers were closely intermingled in the narrow interlamellar space but no collagen-elastin connections were obserevd.
The mechanical properties and organization of the collagen and elastin components of the aortic media indicate that the wall normally functions as a "two-phase" material. At and above physiological pressures, circumferentially aligned collagen fibers of high tensile strength and relatively high modulus of elasticity bear most of the stressing force. Elastin lamellae and fibrils of relatively low modulus of elasticity distribute stressing forces uniformly.
Attempts to assess the role of medial pressure and tension gradients in the pathogenesis of aortic disease must take into account the special mechanical properties of this "two-phase" material.
Hemodynamic Aspects of Prolonged Infusion of Angiotensin into Unanesthetized Dogs
Authors: OLMSTED FREDERICK , PAGE IRVINE H. 
Published: June 2012

Arterial pressure, cardiac output, stroke volume, heart rate, and peripheral resistance have been recorded daily in eight trained, healthy dogs with implanted aortic flow probes and aortic catheters. After suitable control periods angiotensin
II
was infused for periods of from 2 to 29 days.

The effects observed were considered under four categories: 1) The immediate effects consisted of rise of arterial pressure, decrease of cardiac output and heart rate, rise of peripheral resistance and increased pulse pressure. Within five days all values tended to return to control levels unless the infusion rate of angiotensin was increased. 2) A chronic phase followed and, during this period, cardiac output was normal while arterial pressure and peripheral resistance were elevated. 3) After infusions were stopped pressure and peripheral resistance rapidly declined to be low normal, while cardiac output and heart rate rose to above normal. 4) A transient "malignant" phase was elicited by very large increases in the rate of angiotensin infusion, during which cardiac output and stroke volume were diminished while arterial pressure and peripheral resistance were increased greatly.
The hemodynamic changes resulting from prolonged angiotensin infusion were similar in some respects to those found by us during the onset of hypertension due to renal artery constriction in dogs. They differed, however, in that doses of angiotensin, which were great enough to induce arterial pressure elevations similar to those of chronic experimental renal hypertension, reduced stroke volume, and these higher pressures could not be maintained for more than a few days. Hypertension did not persist after discontinuing angiotensin even after 28 days of almost continuous infusion. There was a distinct tendency for the pressor response to diminish with passage of time; more angiotensin was required to maintain similar elevations of arterial pressure.
Equations for Measuring Blood Flow by External Monitoring of Radioisotopes
Authors: ZIERLER KENNETH L. 
Published: June 2012

It is possible by external monitoring alone to measure blood flow per unit volume through any vascular bed accessible to external monitoring of the radioactive tracer if the tracer input function or if the quantity of tracer entering the system is known. The methods proposed exploit the fact that the mean transit time through the system is the flow per unit volume of distribution of tracer. The equations are free of assumptions that require solutions as exponentials or any other specified frequency function of transit times.
If the input function is known, measurement of the concentration of tracer in blood leaving the part sensed by the external detector, combined with external detection of radioactivity, can lead to measurement of absolute blood flow.
Relationship of Pericardial to Pleural Pressure During Quiet Respiration and Cardiac Tamponade
Authors: MORGAN BEVERLY C. , GUNTHEROTH WARREN G. , DILLARD DAVID H. , Breazeale Donald G. , McGough George A. 
Published: June 2012

Pericardial pressure was studied in chronic experiments on dogs with relation to intrathoracic pressure in the normal state and in cardiac tamponade. In the normal resting animal, the two pressures were in good agreement throughout the respiratory cycle. The cardiac cycle produced superimposed pressure fluctuations amounting to 30% of the respiratory swings.
Adding saline to the pericardial sac produced sigmoid pressure-volume curves; tamponade required 100 to 330 ml of fluid. Although during tamponade the pericardial pressure greatly exceeded the intrathoracic pressure, the pericardial pressure invariably fell with inspiration, generally by the same amount as the intrathoracic pressure. The cardiac cycle produced greater pressure fluctuations (50% of the respiratory pressure fluctuations). The superior vena caval pressure always fell with inspiration in the normal state and during tamponade.
Hypovolemia did not change the resting pericardial pressure, but decreased the slope of the pressure-volume curve measured during cardiac tamponade. Hypervolemia increased the resting pericardial pressure considerably, and increased the slope of the pericardial pressure-volume curve.
The results suggest that pleural pressure is a reasonable approximation of the pericardial pressure in normal dogs. There appears to be no substantial evidence that pulsus paradoxus is due to failure of the pericardial sac to transmit inspiratory reductions of pleural pressure.
Functional Characteristics of the Left Ventricular Inflow and Outflow Tracts
Authors: PRIOLA DONALD V. , OSADJAN CHARLES E. , RANDALL WALTER C. 
Published: June 2012

Simultaneous pressures were recorded from the left ventricular inflow and outflow tracts in 14 dogs. In 10 the inflow tract entered systole 4 to 18 msec before the corresponding outflow tract. In 12 additional animals, differential pressure recordings from the two tracts confirmed precedence in the inflow tract. In four animals, strain gauge recordings from the epicardial surfaces of the inflow and outflow tracts exhibited asynchrony with precedence in the inflow tract.

Hearts excised from freshly-sacrificed animals or hearts stopped in diastole by KCI infusion showed a single, openly-communicating ventricular chamber. In contrast, hearts arrested in systole by infusion of CaCl
2
revealed a separation of the left ventricle by the apposition of the anterior and posterior papillary muscles and the dependent mitral valve leaflet.

The apparent conduction velocity of an impact pressure wave from inflow to outflow tract depended upon the portion of the cardiac cycle during which it was delivered. From a maximum of 14 M/sec in mid and late diastole, it decreased to 6.9 M/sec in early systole and 5.5 M/sec in early diastole. Complete attenuation of pressure wave transmission often occurred during maximum systole.
These data support the concept that the left ventricle may become separated, during systole, into an inflow and outflow tract. It appears that the division is accomplished by a change in the systolic ventricular architecture, with apposition of the anterior and posterior papillary muscles and the downward movement of the mitral valve leaflets. It is probable that this phenomenon is functional in hearts working near the lower limits of their systolic reserve.
Depression of Ventricular Contractility by Stimulation of the Vagus Nerves
Authors: DEGEEST HILAIRE , LEVY MATTHEW N. , ZIESKE HARRISON , LIPMAN RALPH I. 
Published: June 2012

In three different types of canine heart preparations, it was demonstrated that efferent vagal stimulation exerts a potent, negative inotropic influence upon the ventricular myocardium. In the paced, isovolumetric, left ventricle preparation, vagal stimulation evoked a reduction of left ventricular systolic pressure which, within limits, varied directly with the magnitude of the stimulus. Supramaximal stimulation elicited a mean reduction of 23% in the peak pressure generated by the left ventricle. No differences could be detected between the effects of the right and left vagi upon ventricular contractility. The percentage changes induced by vagal stimulation upon ventricular contractility in the paced heart were less than the percentage changes in heart rate induced in the spontaneously beating heart.
In a pumping heart preparation in which a constant rate of venous return was delivered to the left atrium, vagal stimulation consistently elicited an appreciable elevation of left ventricular end diastolic pressure. Another pumping heart preparation was employed in which changes in atrial transport function and mitral valve closure were excluded by the expedient of introducing a balloon into the left ventricle through an apical incision. This balloon was connected to an artificial external circuit with fixed venous reservoir height and peripheral resistance. Vagal stimulation consistently diminished stroke volume, "arterial" pressure, and stroke work in such a circuit.
Coronary Insufficiency: Relations Between Hemodynamic, Electrical, and Biochemical Parameters
Authors: Scheuer James , Brachfeld Norman 
Published: June 2012

Perfusion of the left coronary artery of open chest dogs at fixed control and ischemic flow rates demonstrated that ST alterations in the electrocardiogram were always associated with significant hemodynamic and metabolic changes. Decreased pressure time per minute, atrial hypertension, increased myocardial oxygen extraction, and the presence of excess lactate accompanied ischemia. In three dogs, hemodynamic changes, the presence of "excess lactate," or both, preceded significant electrocardiographic changes.
Whenever coronary flow was insufficient to meet myocardial oxygen demands, a series of metabolic shifts occurred. The most significant of these was inadequate aerobic energy production and stimulation of anaerobic glycolysis. This acceleration of anaerobic myocardial metabolism may be present without notably altering the surface electrocardiogram. The absence of ST shifts does not rule out the presence of concomitant and potentially severe myocardial ischemia.
Regional Cerebral low in Man Determined by Intral-artrial Injection of Radioactive Inert Gas
Authors: Høedt-Rasmussen K. , Sveinsdottir Edda , Lassen Niels A. 
Published: June 2012

The intra-arterial injection of a radioactive inert gas is described for measurement of regional cerebral blood flow in man from externally recorded clearance curves.
The stochastic analysis for calculating the average cerebral blood flow in ml/100 g/min is compared to an analysis of the curve into two compartments with fast and slow clearance rates representing flow in grey and white cerebral matter respectively. An estimate of the relative weight of the grey matter in the cerebral region counted from brain is also obtained.

A detailed description is given of the experimental procedure using krypton
85
or xenon
133
as the tracer gas. A brief injection time and short time constant in the recording ratemeter are important for obtaining a correct estimate of the maximal height of the curve. Mono-exponential extrapolation beyond the time of observation (usually 15 minutes) is employed. The practical procedure for calculating the results according to the stochastic and compartmental models are described with particular emphasis on the simple "10 minutes-average-flow-value, "
CBF
(10) which corresponds directly to the results of the classical Kety-Schmidt inert gas inhalation method for measurement of the average blood flow of the whole brain.