bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the Relation Between Ventricular Activation Sequence and the Hemodynamic State
Authors: ABILDSKOV J. A. , EICH ROBERT H. , HARUMI KENICHI , SMULYAN HAROLD 
Published: June 2012

Hemodynamic parameters including records of left and right ventricular pressure, aortic pressure, the first derivative of the left ventricular pressure curve, and carotid flow were recorded with different patterns of ventricular activation. Special measures were used to achieve a comparable role of the atrium in ventricular filling with the different ventricular activation patterns.
With an intact cardiac conduction system, definite but small differences in the hemodynamic parameters named were associated with different activation patterns. Normal ventricular activation produced slightly higher peak pressures in both ventricles and higher carotid flow than did abnormal activation. Each different activation pattern was associated with differences in the detailed shape of the ventricular pressure curves and with differences in the relative time of onset of pressure rise in right and left ventricles. When the specialized conduction system was blocked with large doses of ouabain, various patterns of ventricular activation were associated with marked differences of the hemodynamic parameters named. These findings may explain previously published conflicting results. They also suggest that disease of the conduction system may have a significant functional role in cardiac disease.
Pacemaker Periodicity in Atrial Fibrillation
Authors: BATTERSBY EDWARD J. 
Published: June 2012

The presence of a periodic component in the atrial waveform of patients with chronic atrial fibrillation can be demonstrated by the use of autocorrelation techniques, and is interpreted as evidence for the presence of a periodic or almost periodic pacemaking mechanism. In twelve patients the average rate of this periodic element was 421 per minute with a range of 346 to 528. No correlation is present between increasing rate and disorder of the waveform.
The presence of persistent random wavelets modifying the beat-to-beat spread of excitation generated by a periodic focal pacemaker is proposed as a unifying hypothesis explaining the variability of the atrial waveform in atrial fibrillation in man.
Coronary Arterial Lesions in Chickens
Authors: RATCLIFFE HERBERT L. , SNYDER ROBERT L. 
Published: June 2012

Single-comb, Hy-line white leghorns were hatched in one lot, brooded in one flock through 7 weeks, then assigned randomly to cages in one large room with 15 hours of light per day. The birds were studied in the following situations: a) separately caged cocks and hens, b) paired cocks and hens, and c) 3 cock-3 hen groups and 6 cock-6 hen groups. Basic space allowance was 2 square ft per bird which was increased to 8 square ft for some of the larger groups. Commercial rations and water were supplied ad libitum. Stenosing lesions of the intramural coronary arteries began development in cocks and hens before age 7 weeks (10 to 12 weeks before sexual maturity) and progressed with age. Progress, as measured by heart scores, was not influenced by space allowance but was related to social situation. The rate for separately caged cocks was significantly higher than for other birds. Cocks of the larger groups and cocks of the pairs were next in order, while heart scores for cocks of the smaller groups were third but not significantly higher than for grouped hens. Heart scores of grouped hens sometimes exceeded heart scores for cocks of corresponding groups.
High mean heart scores for grouped cocks correlated with high mean heart scores for hens of their groups, and low heart scores for grouped cocks with low scores for hens of their groups.
Hemodynamic Consequences of Induced Changes in Blood Volume
Authors: Conway James , Gellai Miklos 
Published: June 2012

The effects of transfusion or bleeding on cardiac output and blood pressure have been followed for periods of seven to ten hours in trained, conscious dogs.
When blood volume is increased by transfusion of blood, supplemented by dextran to minimize the expected change in hematocrit, cardiac output and blood pressure increase initially. After one and one-half hours the cardiac output returns to the initial level but blood pressure remains elevated and calculated peripheral resistance increases. This state has been maintained for a period of ten hours by repeated transfusion.
After bleeding, with replacement of packed cells, again to minimize the change in hematocrit, cardiac output decreases initially and peripheral resistance increases, but after three hours, output returns to its former level, and peripheral resistance falls below the control value. These changes become more prominent when a second hemorrhage is performed two hours after the first one. The reduction of resistance was then maintained for seven hours.
These findings demonstrate that the effects of changes in blood volume are not limited to the acute changes in cardiac output and filling pressure. After periods of one to three hours, changes in peripheral resistance also become evident.
Left Ventricular Volume Studies in Tranquilized Dogs with Local Anesthesia
Authors: Bristow J. David , Farrehi Cyrus , Ueland Kent 
Published: June 2012

Left ventricular volumes were estimated by thermodilution in unanesthetized dogs given the tranquilizer, perphenazine. During systole, the left ventricle emptied an average of 40% of its end-diastolic volume. This is a significantly greater proportion than observed previously during general anesthesia with several different agents.
Left ventricular mid-systolic wall force was calculated. Higher force values at a given end-diastolic volume occurred during intravenous infusion of norepinephrine. Methoxamine failed to change these relationships.
Electrical and Mechanical Responses of Vascular Smooth Muscle to Vasodilator Agents and Vasoactive Polypeptides
Authors: Keatinge William R. 
Published: June 2012

Amyl nitrite or sodium nitrite repolarised and relaxed sheep carotid arteries which had been depolarised and contracted by norepinephrine or histamine. These agents had little electrical or mechanical effect on unstimulated arteries. Epinephrine in the presence of phentolamine or Hydergine produced similar effects but the electrical changes were smaller and more variable than with the nitrites. All these agents could cause some relaxation, without electrical changes, of arteries which had been completely depolarised by potassium-rich solution.
Bradykinin and angiotensin, like acetylcholine, depolarised and contracted the arteries even after actions via nerves had been blocked by nicotine and other agents. The effects that they produced when in sustained high concentration were limited in duration. All three agents could contract arteries which were completely depolarised by potassium-rich solution, without any electrical change.
None of these relaxant or stimulant agents had any significant effect at 5°C.
In canine carotid arteries, norepinephrine produced depolarisation and contraction as it does in sheep carotid arteries, but acetylcholine had variable electrical and mechanical effects.
The results suggest that all these vasodilator and vasoconstrictor agents produce their mechanical effects on the arteries partly by changing the cell membrane potential and partly by other means.
Protracted Pressor Response to Angiotensin After Bilateral Nephrectomy in Rats
Authors: Gabelman Edward H. , Rondell Paul A. 
Published: June 2012

The pressor response of nephrectomized rats to an injection of renin is marked by a prolonged stable plateau. A similar, prolonged response to angiotensin has been demonstrated and the following aspects of this pressor effect were evaluated.
1. The protracted response was shown not to be due to a persistence of angiotensin in the blood of nephrectomized animals. There are several indications from unrelated studies that angiotensin is destroyed rapidly. Cross-circulation experiments indicate that during the protracted pressor phase blood levels of constrictor materials have fallen to undetectably low levels.
2. No evidence could be obtained to indicate that the neurogenic buffer system is involved in the development of the protracted response. Ganglionic blockade was ineffective in preventing its development.
3. The hemodynamic basis for the response must be a persistent increase in total peripheral resistance (TPR) since there is no increase in cardiac output (CO) in response to the angiotensin infusion. Before infusion, the CO of nephrectomized animals is higher than that of sham-operated control animals.
4. The increase in TPR must be due to an increase in geometric hindrance for no changes in hematocrit or in viscosity result from angiotensin infusion. Blood viscosity is lower in nephrectomized than in sham-operated animals, but this can account for only part of the lower pre-injection control pressure seen in this group.
It appears that in animals depleted of endogenous renin, a large infusion of angiotensin increases vascular resistance by some non-neurogenic, non-humoral mechanism which may represent another type of vascular tone.
Physical Factors Which Influence Vascular Caliber and Blood Flow
Authors: PETERSON LYSLE H. 
Published: June 2012

1. The radii of blood vessels constitute their major biological functions.
2. The radii of blood vessels are abnormally reduced in most forms of hypertension.
3. The radii of blood vessels are determined by distending pressure and by the geometry and stiffness of the wall material. The latter two factors determine the vessel tone. Thus, tone is defined by those factors which determine vessel radius with respect to distending pressure.
4. It is now possible to measure simultaneously the distending pressure and the factors which determine tone, as well as the radius of vessels. Thus, it is possible to quantitate the factors which determine vascular tone: elastic stiffness (E), viscous stiffness (R), radius (r), and wall thickness (8).
5. These factors have been studied in intact dogs, and the tone of the major vessels of the vascular tree has been mapped out.
6. As the vessel wall itself becomes stiffened, compensatory changes may occur in the geometry. As the vessel dilates and thins, the r/8 ratio enlarges, and the vessel becomes relatively more distensible.
7. Little is known about the changes within the vessel wall which are associated with the mechanical properties of the wall, such as smooth muscle, connective tissue, water and electrolyte concentrations and distributions, the nonhomogenous aspects of the tissue components, or the extent of isovolumetric considerations that are applicable.
8. One of the most challenging aspects of cardiovascular research is to define appropriately and measure the factors mentioned above. They certainly represent part of the key to understanding the etiology and development of hypertension.
Inhibition of Adrenergic Activity at a Locus Peripheral to the Brain and Spinal Cord
Authors: BECK LLOYD , DUCHARME DONALD W. , GEBBER GERARD L. , LEVIN JEROME A. , POLLARD ALBERT A. 
Published: June 2012

This report confirms that adrenergic discharge can be neurogenically inhibited at a site outside of the central nervous system. Centers controlling peripheral inhibition are located in both the spinal cord and the brain. The inhibition is of the competitive-equilibrium type and can be surmounted by increasing the frequency of lumbar sympathetic stimulation. Inhibition of adrenergic discharge at an extraspinal locus occurs in the dog and in two species of monkey. Confirming evidence for central inhibition of vasomotor activity was also obtained in the cat and dog.
Reflex dilatation can still be obtained after brain transections which abolish all neurogenic tone, confirming that reflex dilatation is in part active, and further showing that the centers that control active reflex dilatation and neurogenic tone can be differentiated by selected lesioning. The pathways in the spinal cord that mediate active reflex dilatation, adrenergic discharge, and inhibition of adrenergic discharge were explored.
Sensitization (loss of accommodation) of pressoreceptors in the carotid sinus of the dog vvas noted within two hours of maintained hypotension. Reaccommodation of pressoreceptors occurred rapidly when the blood pressure was returned to normal. Marked sensitization of the vasomotor center to inhibitory input occurred in the same time period. Deaccommodation to inhibitory input also took place rapidly.
Indirect Method for Measurement of Pressure in Blood Capillaries
Authors: INTAGLIETTA M. , ZWEIFACH B. W. 
Published: June 2012

The capillary hydrostatic pressure of blood was measured indirectly. We used a microneedle to occlude exposed mesenteric capillaries in rats and frogs without trauma and then determined the motion of the trapped red blood cells that resulted from the absorption or filtration of water through the capillary wall.
The trajectory of red cells was determined from enlarged timed photomicrographs that cover both sides of the occlusion. Gain or loss of water was measured by following the trajectory of two or more red cells to avoid errors due to injury and incomplete occlusion and extrapolating the motion to the instant of occlusion.
Pressures were calculated from Starling's formula for fluid exchange. We assumed that the tissue parameters are an unknown constant in acute preparations; we used available values of filtration coefficients and colloidal osmotic pressures. The results show that 70 to 80% of the capillaries tested lost fluid, and therefore, their blood hydraulic pressure was higher than colloidal osmotic pressure. The pressures calculated in this way were similar to those measured by techniques requiring puncture of the capillary wall. Capillary arteriovenous pressure differences were approximately 4 mm Hg.
Relation of Increase in Muscle Mass to Performance of Hypertrophied Right Ventricle in the Dog
Authors: GEHA ALEXANDER S. , DUFFY JOHN P. , SWAN H. J. C. 
Published: June 2012

Right ventricular hypertrophy was produced by chronic constriction (banding) of the pulmonary artery in the dog. Right ventricular muscle mass increased by 40% in 6 to 12 weeks after banding. Maximal work performance of this ventricle also increased; at 12 weeks the mean was 175% more than that of the normal right ventricle.
It was concluded that, per unit of gross myocardial mass, the work performance of the hypertrophied right ventricle of the dog was no less than that of the normal right ventricle.
Hydraulic Power Associated with Pulmonary Blood Flow and its Relation to Heart Rate
Authors: MILNOR WILLIAM R. , BERGEL DEREK H. , BARGAINER JACK D. 
Published: June 2012

Pulmonary vascular input impedance and hydraulic power were measured at various heart rates in 29 anesthetized and 5 unanesthetized dogs. Hydraulic power at the pulmonary veno-atrial junction was measured in 5 dogs. The pulmonary vascular impedance spectrum in the unanesthetized dogs did not differ significantly from that in the anesthetized dogs. Average pulmonary arterial power in the anesthetized dogs was 157 milliwatts (mw), of which 108 mw was associated with mean pressure and flow, and 49 mw with the pulsations around these means. Seventy-eight per cent of this input power was dissipated in passage through the pulmonary bed. Kinetic energy accounted for 7% of the total input power.
Because of a steep fall in impedance between zero and 3 cycles/sec, and a rate-dependent change in the harmonic structure of flow pulsations, there was an inverse relationship between heart rate and the input power for a given mean flow, up to 180 beats/min. Pulmonary vascular dimensions and elasticity, which determine impedance, thus embody a mechanism whereby tachycardia can increase pulmonary blood flow by as much as 35% with an increase in pulmonary arterial input power of less than 5%, without the intervention of vasomotor activity.
Cardiac Malformations in the Rat Induced by Maternal Hypercapnia with Hypoxia
Authors: HARING OLGA M. 
Published: June 2012

Forty-seven pregnant rats were exposed for 24 hours to a gas mixture of 6% carbon dioxide, 10% oxygen and 84% nitrogen on different days during gestation. The earliest exposure was on the fifth day after observed copulation, the latest on the sixteenth. The hearts of 370 newborn test rats were studied in serial sections and compared with those from 111 newborn control rats. The over-all incidence of cardiac malformations was 28.1% in the experimental animals and 4.5 % in the controls. In the test groups, severe structural anomalies resulted from exposures as early as the fifth day of gestation.
The results of the present and of previous experiments suggest that maternal hypercapnia in the presence of normal and low oxygen tensions is markedly teratogenic for the cardiovascular system in the rat.
Ventricular Nucleic Acid and Protein Levels with Myocardial Growth and Hypertrophy
Authors: GRIMM ARTHUR F. , KUBOTA RYO , WHITEHORN WILLIAM V. 
Published: June 2012

The myocardial DNA, RNA, actomyosin, and total protein concentrations were determined in rat ventricles ranging between 251 and 1635 mg. Three phases of myocardial growth were evident. Phase 1 (ventricular weights less than 550 mg): DNA concentrations remained relatively constant with increasing ventricular weight. The increasing total DNA per ventricle suggests continuing mitotic activity. Phase 2 (ventricular weights between 550 and 1000 mg): total DNA per ventricle remained relatively constant; with ventricular growth there was a progressive decrease in DNA concentrations. This would be the phase of true myocardial hypertrophy. Phase 3: DNA concentrations continued to slowly decrease although the total DNA per ventricle increased. It would appear that this is the result of a renewed synthesis of DNA.
In phases 1 and 2, the RNA concentrations progressively decreased, although the RNA/DNA ratio was increasing. This ratio appeared to reach its maximum value by the end of phase 2 and remain relatively constant in phase 3. Thus in phase 3, the concentrations of DNA and RNA simultaneously decreased to maintain this constant ratio. The ventricular total protein and ventricular actomyosin levels did not change over this range of ventricular weights.
Contractile Activity of Arterioles in the Bat Wing during Intraluminal Pressure Changes
Authors: WIEDEMAN MARY P. 
Published: June 2012

Spontaneous contractile activity in the smooth muscle cells that invest arteriolar vessels is widely variable. Arteriolar branches originating from the same parent vessel contract independently of one another with no similarity in frequency or duration of individual contractions.
Direct microscopic observations were made of these vessels in the wing of unanesthetized bats before and after surgical denervation or nerve block by procaine. A major artery of the wing was cannulated and buffered saline was perfused in retrograde fashion to produce periods of increased intra-arterial pressure. Elevation of intraluminal pressure led to enhanced contractile activity both before and after denervation of the vessels. It is concluded that these vessels respond by contraction to increased pressure and that the response is not dependent on nervous activity.
Direct Evidence of Nonuniform Distribution of Vagal Effects on Dog Atria
Authors: NINOMIYA ISHIO 
Published: June 2012

The duration of the monophasic action potential (APD), the interval between atrial beats and the delay time between excitation of the right and left atria of dogs were measured, using coaxial suction electrodes, before and during vagal stimulation.
The effect of vagal stimulation on the degree of shortening of APD varied at different recording sites in the atrium, the shortening being more pronounced in the right than in the left atrium. Threshold and rate of recovery after cessation of stimulation varied throughout the atrium. The results indicate that the vagal effect is nonuniformly distributed over the atrium.
The time difference between excitation of the right and left atria increased with vagal stimulation under the present experimental condition, suggesting that a reduction of synchrony of excitation occurred in the atrial myocardial fibers as a whole. The same conclusion was derived from analysis of the pattern of the P wave before and during vagal stimulation.
Extraction, Purification, and Assay of Human Renin Free of Angiotensinase
Authors: HAAS ERWIN , GOLDBLATT HARRY , GIPSON EDWIN C. , LEWIS LAVERA 
Published: June 2012

Three procedures are described for the extraction and purification of renin from 0.05 to 500 g of human kidneys. A uniform yield of renin, free of angiotensinase, resulted from all three procedures.
All tests for renin were carried out in dogs. When more than 10 g of renal tissue was used, renin was determined by the direct method; with smaller amounts, the indirect method, involving the production and the assay of angiotensin, was employed.
Renin substrate free of angiotensinase, suitable for the indirect assay of human renin, was prepared from pooled human serum by a simple procedure.
The angiotensinase-free renin and substrate permitted prolonged incubation for the production of the angiotensin required for the indirect assay. The mean ratio of angiotensin produced (unit per milliter of serum) to the amount of renin added (unit per milliliter of serum) was 1,482 for an 18-hour period of incubation. The large amount of angiotensin produced permitted the indirect assay of minute amounts of human renin (as little as 0.0005 unit, from 5 mg of renal tissue) in the dog. Unless the angiotensinase present in extracts of renal tissue or serum is first removed, the accurate, indirect assay of the renin is not possible.
Role of Histamine in Hypoxic Pulmonary Hypertension in the Rat
Authors: HAUGE ANTON , MELMON KENNETH L. 
Published: June 2012

The present investigation was undertaken to see if any of the naturally occurring vasoactive substances was likely to act as a mediator for the pulmonary vasoconstrictor response to acute alveolar hypoxia. Rats were treated with agents that deplete local stores of vasoactive amines or inhibit their synthesis. Lungs from these animals were isolated, ventilated, and perfused with homologous blood at constant volume inflow. Their pressor responses to 2- to 3-minute periods of ventilation hypoxia (2% O
2
) were observed.

The histamine-releasing agent 48/80 or the histidine decarboxylase inhibitor NSD 1055, or both, depleted 73% of the histamine in the lung but had no consistent effect on the pressor responses to hypoxia. When 48/80 (0.2 to 1 mg) was given in vitro, histamine in the lung was reduced to 10% of normal, or less, and the pressor response to alveolar hypoxia was completely abolished.
Reserpine, guanethidine, or alpha-methyl-tyrosine reduced catecholamine stores in heart tissue (as an index of general tissue changes) by a maximum of 90% and reserpine decreased serotonin in the lung by 93% without inhibiting the hypoxic pressor responses. The findings strengthen the concept that histamine mediates the pressor response to acute alveolar hypoxia in the rat.