bluuebunny/crossref_metadata_2025_split huggingface dataset:
Forward and Backward Transmission of Pressure Waves in the Pulmonary Vascular Bed of the Dog
Authors: CARO COLIN G. , BERGEL DEREK H. , SEED W. ANTHONY 
Published: June 2012

Pressures were measured in lobar pulmonary arteries, veins, and left atria of anesthetized open-chest dogs. Observations were made before and after snaring the lobar vessels and before and after infusing dextran to raise the mean pressure. Pressure waves were subjected to harmonic analysis. Forward (artery to vein) and backward (vein to artery) transmission (output/input pressure) and transmission ratios (forward/backward transmission) were calculated for each harmonic.
At low frequencies, forward transmission was increased by dextran, but backward transmission was unaffected. At low frequencies and high mean pressures the bed was nonsymmetrical, forward transmission being several times greater than backward at the same mean pressure (transmission ratio >1).
The findings were analyzed with the aid of simple models. Nonsymmetry at low frequencies and high mean pressures appears to be due to arterial exceeding venous compliance. The findings and resulting theory are pertinent to the understanding of the shape and amplitude of arterial "wedge"-pressure traces.
Blood Flow through Terminal Arterial Vessels after Denervation of the Bat Wing
Authors: WIEDEMAN MARY P. 
Published: June 2012

Previous studies of microcirculation in the denervated wing of the unanesthetized bat showed that major arterial vessels increased markedly in diameter and lost their ability to contract spontaneously. Arteriolar vessels did not show such an increase in diameter, and furthermore their spontaneous contractile activity increased. These observations led to the idea that regulation of blood flow and blood pressure might be continued to some degree in the absence of central nervous control through enhanced activity of arteriolar vessels which just precede the capillary nets.
Therefore a thorough study by direct microscopic observation of the behavior of arterial vessels in the following surgical and pharmacological denervation was made. The data support the hypothesis that loss of tone and loss of contractile activity in the large arterial vessels following denervation produce an increase of tone and activity in the smaller, more distally located vessels, thereby causing a redistribution of the site of regulation of flow through capillary nets. The largest arterial vessels showed and increase in average diameter of 38% after surgical denervation, while the terminal arterioles showed a decrease in average diameter of 24%. Neither phenoxybenzamine (Dibenzyline) norpentolinium (Ansolysen) were as effective as surgical denervation in producing relaxation of the large arterial vessels. Neither drug inhibited spontaneous contractile activity of the terminal vessels.
Microelectrode Study of Delayed Conduction in the Canine Right Bundle Branch
Authors: WENNEMARK JAMES R. , RUESTA VICTOR J. , BRODY DANIEL A. 
Published: June 2012

The electrophysiology of conduction delay was investigated in the semi-isolated right bundle branch of 30 large mongrel dogs. Delay was produced by the external application of an electric blocking current to the bundle branch. Multiple recordings with glass capillary microelectrodes revealed two basic deflections associated with the delay phenomenon. An initial, or leading, deflection originated from the proximal or leading edge of the block and was rapidly transmitted through the block with progressive decay of voltage and rise velocity. A second, or trailing, deflection originated from the regenerative response at the distal or trailing edge of the block and was rapidly transmitted retrograde into the block, with progressive decay of voltage and rise velocity. The transmitted potentials appeared to be electrotonic in nature.
The leading deflection appeared to be the transmitted event which maintained a conduction ratio of 1:1 through the block. The magnitude of delay was then related to the time required for this deflection to reach the threshold potential and initiate a regenerative response in the trailing portion of the block where the cells were less affected by the blocking current.
Simultaneous Measurements of Radii and Wall Thickness of Microvessels in the Anesthetized Rat
Authors: Baez Silvio 
Published: June 2012

The purpose of this investigation was to measure the radius and wall thickness of small blood vessels in mesentery and striated (cremaster) muscle in the anesthestized rat. Using the method of image-splitting, the vessel images were sheared at magnifications of 3,OOOx and 6,500x on the video screen.
In the resting state, the mean lumen values for the thinnest portion of endothelial capillary were 4.1 ± 1.2µ (SD) in cremaster and 5.6 ± 1.3µ (SD) in mesentery. Lumen and total diameter were also greater at several levels of precapillary arterioles in mesentery than similar vessels in cremaster, suggesting that smaller vessel size in cremaster might be characteristic of this tissue. Vasoconstriction of up to 50% from resting state is associated with an increase in wall thickness and a decrease in lumen to wall ratio due to a disproportional decrease in radius (inner greater than outer radius). Similarly, an increase in vessel radius in a proportion 4 to 1 (inner greater than outer) was sustained up to about 60% of vasodilatation.
In 13 out of 14 vessels, little or no change in wall cross-sectional area occurred in the face of marked changes in lumen cross-sectional area (–95%,+205%). This strongly suggests that other modifications such as changes in length, swelling, or shrinkage would be relatively unimportant during dynamic changes in wall thickness.
Mechanism Initiating Ventricular Fibrillation Demonstrated in Cultured Ventricular Muscle Tissue
Authors: SANO TOYOMI , SAWANOBORI TOHRU 
Published: June 2012

Ventricular muscle strips of the rat embryo heart were used for tissue culture preparations without adding trypsin. Fibrillation-like arrhythmia was induced by adding aconitine or strophanthin, and the potentials were recorded with one or two microelectrodes. The tracing by one microelectrode was no different than tracings from fibrillating adult mammalian hearts. The size and shape of the action potential varied beat by beat, and its time of appearance was quite irregular and rapid. But, when tracings obtained simultaneously by two microelectrodes were compared, most of the action potentials were roughly synchronous and thus unlike adult cardiac fibrillation. This ruled out the possibility of multiple reentry or multifocal origin in this preparation.
Because of the small size of the cultured tissue, reentry of the excitation wave probably could not occur, and the conclusion that fibrillation originated from a single focus is thus supported. Three varieties of the onset of fibrillation, i.e., gradual increase of tachycardia with progressively steeper slow diastolic depolarization, a prominent positive afterpotential followed by a negative afterpotential, and abortive action potentials superimposed on the repolarization of the preceding action potentials or on the negative afterpotential, supported the unifocal onset.
Response of the Main Pulmonary Artery of Dogs to Neuronally Released Versus Blood-Borne Norepinephrine
Authors: INGRAM ROLAND H. , SZIDON JAN P. , FISHMAN ALFRED P. 
Published: June 2012

The effects of sympathetic nerve stimulation and of norepinephrine infusions on the dynamic elastic properties of the main pulmonary artery were studied in 20 anesthetized, open-chest dogs. Pulmonary arterial pressure and diameter were linearly related between 5 to 45 mm Hg and at heart rates of 40 to 200 beats/min. Sympathetic nerve stimulation changed the stiffness (pressure-diameter slope) of the pulmonary artery by +35%; infusion of norepinephrine (0.25 µg/kg/min) by only +14%. Diameter intercepts, determined by extrapolation of the linear pressure-diameter line, were unchanged during stimulation, but decreased significantly during the infusion of norepinephrine. Local application of norepinephrine to the wall duplicated the changes produced by sympathetic nerve stimulation.
Histologically, the arrangement of smooth muscle in the outer layers of the media of the artery suggested linkage of smooth muscle with continuous elastic fibers, whereas smooth-muscle cells of the deeper layers of the media appeared to connect with each other, and elastic fibers were discontinuous. The topical application of elastase to the outer wall effected a loss of elastic fibers in the outer layers of the media. After elastase, neither stimulation nor norepinephrine infusions increased stiffness; diameter intercepts decreased with both.
The observations are consistent with the idea that stiffening of this artery during nerve stimulation is produced by contraction of smooth muscle attached to elastic fibers and that the anatomical arrangement for stiffening is located in the outer layer of the media, where the sympathetic nerve endings are located. In contrast, blood-borne norepinephrine stimulates predominantly the inner layers.
Direct Current Make and Break Thresholds for Pacemaker Electrodes on the Canine Ventricle
Authors: DEKKER EGBART 
Published: June 2012

Thresholds to anodal make, anodal break, cathodal make and cathodal break have been studied throughout the cardiac cycle in 13 dogs under pentobarbital anesthesia.
Unipolar direct current pulses were applied through epicardial pacemaker electrodes to the left ventricle. Make and break responses were separated by letting the break and make occur in the refractory periods of the following and preceding cycle, respectively.
Four distinct threshold interval curves were obtained from each of 17 electrodes. The anodal break and cathodal break curves showed an early diastolic dip. Dips were deepest in the anodal break curves. These also had the shortest effective refractory period. Thresholds for cathodal make and anodal make first dipped steeply, then gradually sloped down towards end-diastolic levels. The magnitude of end-diastolic mean threshold values increased in the following order: cathodal make, anodal make, cathodal break, anodal break.
Comparison of threshold interval curves for make and break responses with those for shorter rectangular anodal and cathodal curves throughout the cardiac cycle supports the hypothesis that the threshold behavior to a short rectangular pulse is determined by whichever of two thresholdsis lowest: make or break at that particular cycle interval.
Indirect Induction of Vascular Damage by X-Irradiation
Authors: LEVY CHARLES K. 
Published: June 2012

The changes in petechial susceptibility of the vessels of hamster cheek to the moccasin venom test have been compared in shielded and irradiated pouches of the same animal which had received median lethal doses of x-irradiation. There was no statistically significant difference demonstrable between the irradiated and controlled cheek pouches, but both showed a greater hemorrhagic response than was found in the cheek pouches of unirradiated control animals.
Similar results were found when the diffusion of intradermally injected Evans blue was used as an indication of x-irradiation damage. The shielded and the exposed areas both showed enhanced permeability to the dye when compared with the unirradiated control animals.
These results suggest that some indirect factor or factors are involved in the vascular and permeability changes following exposure to ionizing radiation.
Electrolytes and Arterial Muscle Contractility
Authors: DODD W. ALAN , DANIEL EDWIN E. 
Published: June 2012

Arterial contractility in response to various drugs was studied in media designed to alter ionic gradients of sodium and potassium across the cell membrane. Tissues were analyzed to determine the effects of these procedures on tissue electrolytes and to demonstrate any correlation between tissue electrolytes and response.
It was found that the contractile responses progressively decreased in sodium-free media, disappearing in 2 to 2½ hours. A decrease in external potassium, initially caused a potentiation of response. Thereafter, a decreased response was manifested, yet contractility remained even after 7 to 8 hours in potassium free medium. Increased external potassium caused an increase in response.
There was no correlation between the content of sodium and potassium and response in potassium-free solutions, but in sodium-free solutions a positive correlation between contractility and potassium content existed.
Chloride appeared to exist in 2 fractions, a diffusible fraction, and a more tightly bound fraction. Calculation of the ECFV based on the bound chloride yielded values which otherwise would have been absurd.
Sodium appeared to be distributed in 3 fractions; diffusible and extracellular, not diffusible over the duration of our experiments and slowly diffusible and presumably intracellular, the latter fraction being possibly capable of cation exchange.
Evidence obtained does not suggest that the sodium gradient, per se, is responsible for contractility. The concentration of intracellular potassium does not influence contractility directly. However, the potassium gradient may in part determine vascular muscle contractility.
Effect of Addition and Removal of a Kidney Transplant in Renal and Adrenocortical Hypertensive Rats
Authors: GOMEZ A. H. , HOOBLER S. W. , BLAQUIER P. 
Published: June 2012

A method is described for preparing and studying the acute effect of renal transplants on the blood pressure of the rat. In such a preparation, renal blood flow, urine flow, and blood pressure are well maintained over a period of several hours. In hypertension of less than 6 months' duration following renal ligation or desoxycorticosterone administration, the transplant consistently reduced the blood pressure and in 36 out of 44 experiments normotensive levels were achieved in 30 to 40 minutes. Exclusion of the kidney permitted a gradual restoration of the hypertension. When the blood pressure was elevated by infusions of renin or angiotensin, the blood pressure did not fall after the transplantation procedure. Introduction of kidney tissue after the hypertension had lasted for 6 months or more reduced the blood pressure in only 10 of 23 experiments, suggesting that after the passage of time irreversible vascular changes had occurred.
The mechanism by which the transplant lowers the blood pressure is unknown, but such factors as the creation of an area of low vascular resistance, the release of non-specific depressor substances into the circulation, and the external loss of a pressor substance into the urine seem to be excluded. Reasons are given for suspecting that the antihypertensive action of normal kidney tissue is a specific metabolic or incretory effect, rather than an excretory action related to urine formation.
Effect of Prolonged Periods of Anoxia on Atrioventricular Conduction and Cardiac Muscle
Authors: COFFMAN CAPT. JAY D. , LEWIS F. BRUCE , GREGG DONALD E. 
Published: June 2012

The return of A-V conduction according to the electrocardiogram, the ability to maintain the blood pressure, the cardiac muscle ATP, the coronary venous pH, lactic acid, and potassium were studied to delineate the effects on the heart of prolonged periods of anoxia in dogs maintained on an extracorporeal circulation. Myocardial anoxia for 100 minutes was the limit for return of A-V conduction in all dogs in these experiments. Only 2 of 5 hearts anoxic for 120 minutes, and 1 of 3 hearts anoxic for 150 minutes regained A-V conduction. One heart subjected to anoxia for 165 minutes did not show A-V conduction on reperfusion of the coronary arteries.
The dogs whose hearts were subjected to periods of anoxia longer than 100 minutes could not maintain the blood pressure on removal from the extracorporeal circulation. This was due to the development of an unusual firmness of the left ventricular muscle, usually appearing after 90 minutes of anoxia and progressing to involve the entire heart. This firmness was not reversible on reperfusion of the heart. Since A-V conduction and speed of conduction returned in some of these firm hearts, it was concluded that there was earlier permanent damage to the myocardial muscle than to the conduction system during anoxia.
Cardiac muscle ATP values were not definitely changed after 30 minutes of anoxia, but were decreased and regenerated on reperfusion of the heart after 60 minutes of anoxia. The low levels of ATP did not return toward normal on reperfusion of the heart after 90 and 120 minutes of myocardial anoxia. Additional experiments on anoxic hearts of nonperfused dogs also demonstrated the marked decrease in ATP levels. In both types of studies, the earliest onsets of firmness showed some correlation with low ATP levels. The high lactic acid levels and low pH values of the coronary venous blood found after long periods of anoxia may be related to the failure of ATP regeneration and to the onset of firmness in these hearts.
Potassium arrest of hearts subjected to anoxia showed no difference in the return of A-V conduction, in the ability to maintain blood pressure on removal from the extracorporeal circulation, in the onset or degree of myocardial firmness, nor in the levels of cardiac muscle ATP, coronary venous pH, and lactic acid, from the anoxic, nonarrested hearts.
The variability of the effect of anoxia on A-V conduction and myocardial muscle of different hearts by the parameters measured in this study is stressed.
Labeled Phosphate Distribution in Working and Nonworking Myocardium
Authors: TSUBOI KENNETH K. , BUCKLEY NANCY M. , ZEIG NORMAN J. 
Published: June 2012

Investigation of phosphate metabolism with the aid of labeled phosphorus has been carried out, using isolated heart preparations in which only the left ventricles perform external work. The corresponding right ventricles in such preparations perform no external work with the unique experimental advantage of a single heart, providing simultaneously both working and "resting" (nonworking) metabolic states.
Comparative incorporation of labeled phosphorus into nucleotide phosphate groups, non-nucleotide soluble phosphorylated components, phospholipids and ribose nucleic acid was examined as a function of cardiac work. Incorporation of the label into the rapidly exchanged high-energy phosphate groups was found to be restricted by a prior rate--limiting entry of the externally perfused isotope into the cells, thereby precluding a measure of turnover of these groups by this technic. Differences could not be demonstrated in isotope incorporation in either the phospholipids or RNA of working as compared to nonworking myocardium. It was concluded from these results that RNA is clearly not involved in energy reactions associated with cardiac work function. Phospholipid participation, on the other hand, could be clearly excluded only insofar as the phosphate moiety of these compounds is concerned.
Information relevant to a mechanism of phosphate entry into cardiac cells was obtained in which a phosphorylation of hexose appeared to be involved. The composition of cardiac tissue with respect to nucleotide and non-nucleotide soluble components was examined in working and nonworkiug myocardium. Differences in composition were not found with respect to these constituents. A major component appearing in extracts of cardiac tissue was found and subsequently identified to be α-glycerophosphate. On the basis of isotope incorporation data, it was concluded that its metabolic source was of carbohydrate rather than phospholipid origin.
Effect of Ethanol on Serum Cholesterol Concentration in Dog and Man
Authors: GRANDE FRANCISCO , HAY LYLE J. , HEUPEL H. WILLIAM , AMATUZIO DONALD S. 
Published: June 2012

The effect of ethanol on serum cholesterol concentration has been studied in normal male dogs subsisting on diets of low cholesterol content. Daily administration of 1.65 Gm. ethanol/Kg, of body weight produced significant increases of serum cholesterol in dogs when fed either a low-fat diet (4 per cent of fat calories) or a high-fat (40 per cent) diet. The mean cholesterol increase after 2 weeks of ethanol administration was 52 mg./100 ml. (SE, 8.2) for 8 dogs on the low-fat diet, and 75 (SE, 6.6) for 24 dogs on the high-fat (lard) diet. No significant difference was found between the mean increases of serum cholesterol produced by ethanol administration, using either the high-fat diet of saturated fat (lard) or that of unsaturated fat (sunflower oil). Serum cholesterol concentration decreases rapidly after discontinuing the administration of ethanol, reaching the prealcohol levels in 2 to 3 weeks. The higher levels of serum cholesterol are maintained as long as the administration of ethanol continues. Sodium acetate, when given at the same molar quantity as ethanol, failed to produce any change of serum cholesterol concentration in the dog.
The effect of ethanol administration on serum cholesterol concentration in man was tested in 2 switchback experiments, comparing the effects of alcohol and those of a supplement of syrup of equal calorie value while the men were eating a normal diet containing 38 per cent of fat calories. When 0.45 Gm. ethanol/ Kg./day were given to 59 normal men for 3 weeks, no significant difference of serum cholesterol concentration was observed between the values on syrup and on alcohol. However, the administration of 1.35 Gm./Kg./ day to 14 men produced a mean increase of serum cholesterol concentration of 18 mg./100 ml. (SE, 5.0) within 1 week. The individual increases of serum cholesterol are correlated with the intrinsic cholesterol levels of the subjects (r = + 0.67, p > 0.01). It is concluded that ethanol increases serum cholesterol concentration in the dog and man. The response in the dog is much greater than that observed in the human subjects.
Factors Affecting the Filling of the Frog's Ventricle After Isotonic Contraction
Authors: HENNACY RICHARD A. , OGDEN ERIC 
Published: June 2012

A measurable factor determining the filling of the heart is the opposition that the myocardium offers to being stretched. This is expressed as "renitence," which is the ratio of filling pressure to the rate of inflow. Isolated frog ventricle was connected to a vessel containing Ringer's solution at a fixed head of pressure. Change in the volume of the heart was recorded optically. From these time-volume curves, renitence was calculated.
For the frog ventricle filling and emptying against a fixed head of pressure, the renitence during the filling period first decreases, passes through a minimum, and then increases. The minimum and average renitences occurring during a cycle appeared to be increased by cooling, a rise in filling pressure, pentobarbital or a combination of hypoxia and acidity.
The renitence early during the filling cycle is largely determined by the residual tension from the previous systole, and the subsequent increase seems to be determined by the elastic properties of the myocardium.