bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vasodilator Action of Guanethidine
Authors: Abboud Francois M. , Eckstein John W. 
Published: June 2012

The cardiovascular effects of intravenous guanethidine were measured in animals treated with reserpine. The action of intraarterial guanethidine was studied also in perfused forelegs of dogs. The following conclusions were reached:
1. There was no significant increase in cardiac output, heart rate, or systemic arterial pressure following intravenous guanethidine in treated animals; only sustained vasodilatation was observed.
2. The vasodilatation was caused by a local action of the drug on vascular smooth muscle. The dilatation became more pronounced following depletion of catecholamines with reserpine and repeated administration of guanethidine.

3. The dilatation did not appear to be mediated through the release of catecholamines, histamine, or acetylcholine. It may have resulted, at least in part, from stimulation of
beta
adrenergic receptors or other "dilator receptors" which are blocked by dichloroisoproterenol.
Release of a Thromboplastic Substance from Arterial Walls by Epinephrine
Authors: SHIMAMOTO TAKIO , ISHIOKA TADAO 
Published: June 2012

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
Pressor Effect of Increased Cerebrospinal Fluid Pressure and Vertebral Artery Occlusion With and Without Anesthesia
Authors: DICKINSON C. J. , MCCUBBIN J. W. 
Published: June 2012

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.
Non-Newtonian Rheology of Human Blood - Effect of Fibrinogen Deduced by "Subtraction"
Authors: MERRILL EDWARD W. , COKELET GILES C. , BRITTEN ANTHONY , WELLS ROE E. 
Published: June 2012

A study of the rheological properties of human blood, from donors in normal health, was carried out by means of a coaxial cylinder viscometer designed to measure very small levels of stress under conditions of "creeping" flow.
It was found that under these conditions of measurement the rheological properties could be conveniently presented by plotting the square root of shear stress against square root of shear rate. For normal blood, a nearly linear relation is found on such a plot, and the intercept on the stress axis at zero shear rate represents the square root of yield stress, separate determination of which is made by other means.
Similar plots for (i) defibrinated blood and (ii) suspensions of red cells in isotonic saline solution reveal no yield stress. Thus it is concluded that fibrinogen is essential for the existence of yield stress in human blood. Furthermore, the approximate linearity, for normal blood, of the square root of shear stress with square root of shear rate, and the yield stress intercept, are of great interest inasmuch as mathematically identical relations ensue according to an equation developed by Casson based on a physical model in which the elementary particles of a suspension are capable of reversible association into rod-like structures, the length of which is controlled by the shear rate. It is of interest to consider the Casson model in the light of rouleaux formation and the relation of fibrinogen to rouleaux formation.
Viscosity and Clotting of Blood in Venous Thrombosis and Coronary Occlusions
Authors: DINTENFASS LEOPOLD 
Published: June 2012

Viscosity of blood was measured in the absence of anticoagulants by means of an improved cone-in-cone viscometer. Data obtained in a study of a series of patients suffering from venous thrombosis and coronary occlusion were compared with data from a control group of healthy subjects. The probability that the large difference in viscosity observed between normal and abnormal blood is due to chance is approximately 1 in 1,000,000. The viscosity of blood remains constant, at any rate of shear, during the first two to four minutes after removal of blood. Clotting starts after various time periods, depending not only on the intrinsic properties of the particular blood sample, but also on the velocity gradient at which such clotting takes place.
The following general trends were established : at 36°C the onset of clotting is much more rapid at high rates of shear than at low rates of shear. It appears, however, that at lowered temperatures this trend is reversed.
The causes of aggregation of red cells, and the role of this aggregation in clotting, are discussed. It is emphasized that blood is thixotropic, i.e., that its viscosity is both time and rate-of-shear dependent. Thixotropy of blood is due, mainly, to a reversible aggregation of red cells. This suggests the existence of intermittent sedimentation of red cell aggregates during flow in blood vessels. Owing to the existence of a velocity profile, in which the axial region is under zero or near-zero rate of shear, such aggregates should be present especially in large veins and arteries. It appears that an increased thixotropy and viscosity are symptomatic of some thrombotic states.
Spontaneous Coronary Arteriosclerosis in Repeatedly Bred Male and Female Rats
Authors: WEXLER BERNARD C. 
Published: June 2012

Repeatedly bred male and female rats of several strains develop arteriosclerosis spontaneously, irrespective of diet. The severity of the lesions differs between male and female breeders. The morphology and pathogenesis of these lesions have been found to be the same in all of the strains examined. Once the process of arteriosclerosis has been initiated within the abdominal aorta, the subendocardial and medium-sized myocardial coronary arteries also show degenerative changes. The large epicardial coronary arteries become arteriosclerotic only when the process of arteriosclerosis has become severe and generally distributed throughout the aorta.
The smaller subendocardial lesions are characterized by occlusive swelling of medial muscle cells and by the presence of vacuoles. These vacuoles react negatively to lipid stains but stain positively for mucopolysaccharide. The myocardial arteries show endothelial hyperplasia, elastosis and accumulations of mucopolysaccharides, especially in the region of fragmented elastic elements. The mucopolysaccharide-rich endothelial cushions eventually become fibrosed. The epicardial arteries show intense accumulations of calcium-mucopolysaccharide complexes. These arteries become greatly distended and can be detected grossly because of their size and tortuosity.
Acute and chronic myocardial infarct-like lesions are found but these cannot be associated with specific coronary thrombi or arteriosclerotic lesions. Valvular scarring, calcification of the papillary muscles and disappearance of myocardial mast cells has been correlated with advancing arteriosclerosis.
The relation between the intensity of coronary arteriosclerosis and the frequency of breeding, the sex of the animal, and the strain indicates that the pathogenesis of this disease in breeder rats is probably governed by hormonal factors, e.g., sex and adrenal steroids, as well as by genetic factors.
Multiple Recording During Electrically Induced Atrial Fibrillation
Authors: SANO TOYOMI , SCHER ALLEN M. 
Published: June 2012

1. Atrial fibrillation was induced in dogs by single electrical shocks. Close bipolar direct electrograms were taken from various parts of the atrium; as many as 22 electrograms and a standard lead II electrocardiogram were recorded simultaneously. Initial phase and recovery phase of fibrillation were analyzed.
2. In the initial phase of atrial fibrillation, local firing consisting of rapid tachysystole of 996 to 3000 per minute was observed near the stimulating point in most experiments. Except for the leads showing local firing, the interval between beats at each recording point tended to be constant, and a time gap between two successive beats was observed. A propagation pattern could be plotted which seemed to start from the origin of local firing; some beats were conducted only locally, and others (every second, third or fourth discharge) were conducted widely. The cause of atrial fibrillation was considered to be local firing of one small area of the atrium, i.e., the unifocal theory of the origin of atrial fibrillation was supported.
3. During recovery from atrial fibrillation, features similar to those seen in the initial phase often appeared, although local firing disappeared. In some experiments, the atrium was separated electrically into a few groups of cells beating independently, and in others a "circus pathway" appeared to exist in the last beat. It seems that electrical separation of the atrium into many parts and circus movements, or multiple re-entry, may develop during the course of fibrillation, and that these phenomena perpetuate atrial fibrillation.
4. During the last beat of atrial fibrillation, the time required for all cells to depolarize was occasionally less than the duration of the normal sinus beat. A similar phenomenon was sometimes observed in the premature beats following atrial fibrillation.
Hypersecretion of Aldosterone in Dogs with a Chronic Aortic-caval Fistula and High Output Heart Failure
Authors: DAVIS JAMES O. , URQUHART JOHN , HIGGINS JAMES T. , RUBIN ELLIS C. , HARTROFT PHYLLIS M. 
Published: June 2012

Hypersecretion of aldosterone occurred at the onset of signs of congestive heart failure in a large series of dogs with a large infrarenal aortic-caval fistula. There was evidence of right heart failure in all animals and in four of the dogs râles or frank pulmonary edema was present. Marked sodium retention and ascites or edema were consistent findings and in the majority of the animals central venous pressure was elevated.
Hypophysectomy was followed by a striking fall in both aldosterone and corticosterone secretion but in several animals hypersecretion of aldosterone was evident in the absence of the anterior pituitary. Subsequent acute bilateral nephrectomy of these hypophysectomized dogs resulted in a marked drop of aldosterone secretion to a very low level, and a precipitous fall in arterial pressure frequently occurred. An intravenous infusion of a saline extract of each animal's kidneys produced a striking elevation in aldosterone output; corticosterone secretion and arterial pressure increased consistently. The kidneys of these dogs with heart failure secondary to an A-V fistula frequently showed hypergranulation and hyperplasia of the juxtaglomerular cells. The present findings suggest that the increased rate of aldosterone secretion was mediated by the renin-angiotensin system.
Measurements of arterial pressure and renal hemodynamic function demonstrated a fall of mean renal arterial pressure, glomerular filtration rate, and renal plasma flow, whereas arterial pulse pressure above the fistula and presumably in the kidneys was increased. The data suggest that decreased pulse pressure is unnecessary for activation of the renal mechanism leading to hyperaldosteronism.
Principal Factor Waveforms of the Thoracic QRS Complex
Authors: HORAN LEO G. , FLOWERS NANCY C. , BRODY DANIEL A. 
Published: June 2012

High-speed, high-fidelity recordings from 150 to 180 systematically spaced points over the thoracic surface of both a dog and a man have yielded detailed maps of QRS waveforms. With the aid of digital computer analysis, these waveforms have been resolved into the minimum number of mathematically uncorrelated waveforms necessary for adequate resynthesis of all the original QRS complexes. Under the conditions imposed by the experimental design, seven (in the dog) and eight (in the man) such waveforms, or principal factors, were found. Maps were constructed for both the contribution of each principal factor to the various regions of the chest and also for the degree of reproducibility of the original waveforms by successive addition of the principal factors.
The first three factors accounted for an average of 92.8% of the available information on the chest in the dog and 85.4% in the man. A resynthesis of over 99% of the information was achieved for both subjects when all remaining principal factors were also employed. This necessity for more than three factors or generating functions for reproduction of all the known surface potentials was interpreted as strong support to the equivalent multipole concept of the electrocardiographic generator. In addition, the reduction of total surface information into a compact set of waveforms of specified distribution opens an experimental avenue to the examination of such concepts in living subjects.
Spontaneous Arteriosclerosis of the Mesenteric, Renal, and Peripheral Arteries of Repeatedly Bred Rats
Authors: WEXLER BERNARD C. , Kwallek Jo tee , Conatser Dilman 
Published: June 2012

Repeatedly bred male and female rats develop arteriosclerosis spontaneously. The arteriosclerosis appears to be accelerated by breeding because virgin rats of comparable age do not develop arterial disease. The arterial lesions begin in the abdominal aorta and consist of subendothelial swelling, mucopolysaccharide accumulation and eventual fibrosis. With continued, active breeding, the arterial lesions continue to increase in severity in the abdominal aorta, becoming grossly visible in the female breeder and of microscopic proportions in the male breeder.
Concomitant with the increasing severity of arteriosclerosis in the abdominal aorta, the mesenteric arteries and the visceral branches also show increasing numbers of arterial lesions. The lesions in the mesenteric and visceral branches are of varied morphology. The main renal artery, for example, shows fibromuscular dysplasia, its hilar portion displays intimal basophilia and elastosis and the intrarenal branches develop intimal cushions.
The male breeder develops severe, grossly visible lesions in the proximal portions of the iliac arteries, the lesions becoming less complex distally. The female breeder shows no grossly visible lesions in the iliac arteries but arteriosclerosis is severe throughout the length of the arteries to the extremities, the severity of these lesions being proportional to the arteriosclerosis in the abdominal aorta and its branches.
Reduction by Hyperbaric Oxygenation of the Mortality from Ventricular Fibrillation Following Coronary Artery Ligation
Authors: CHARDACK WILLIAM M. , GAGE ANDREW A. , FEDERICO ANTHONY J. , CUSICK JOHN K. , MATSUMOTO PAUL J. H. , LANPHIER EDWARD H. 
Published: June 2012

The effect of the inhalation of hyperbaric oxygen on the incidence of ventricular fibrillation following ligation of the circumflex coronary artery was studied in 151 dogs weighing 17 kg or more.
Fifty-two per cent of the animals in the control group (room air, 1 atm abs) survived the challenge of this ligation. Survival increased to 60.4, 70, and 77.8% in the groups given 100% oxygen at an ambient pressure of 1, 2, and 4 atm abs, respectively. The orderly progression in the proportion of survivals is impressive but only approaches statistical significance.
The results of these experiments are less dramatic than those previously reported by others. They do point out the need for cautious clinical trial in rigidly controlled series.
Neurogenic Hypertension in the Rat
Authors: KRIEGER EDUARDO M. 
Published: June 2012

Several techniques of radical denervation of the sino-aortic depressor areas were tried in order to produce a permanent neurogenic hypertension in the rat. The aortic depressor fibers were interrupted at the neck level by resecting the nerves which usually exhibit baroreceptor activity, namely, isolated aortic nerve, sympathetic, and laryngeal nerves. The carotid sinus was denervated by stripping the carotid bifurcation and painting with phenol. When the carotid bifurcation was resected bilaterally, in a one-stage operation, all rats showed symptoms of cerebral ischemia, dying shortly thereafter.
Isolated denervation of the aortic baroreceptors was followed by a transitory hypertension. No changes in preasure were observed when only the carotid sinuses were denervated. A few rats in which the usual baroreceptor pathways were interrupted, except the superior laryngeal nerve, developed chronic hypertension. Yet, to obtain consistently permanent hypertension it was necessary to include in the denervation every baroreceptor route.
A simple one-stage operation for complete sino-aortic baroreceptor denervation is described. This procedure was used in 140 rats that were then studied for periods up to one year. All the operated animals presented some degree of hypertension. Blood pressure measurements made during the first week showed even then that the rats were hypertensive. This observation suggests that in the rat no latent period for the appearance of neurogenic hypertension is present. Hypertension was permanent in 75% of the rats observed up to one year; blood pressure returned to normal values in the remaining 25%, usually after the third month. Extirpation of the adrenal medulla had no effect on the evolution of the hypertension in the denervated rats.
Blood pressure was measured repeatedly in unanesthetized rats by tail plethysmography. Pressure values determined by this method, though 10 to 20 mm Hg lower, approximated the mean arterial pressure recorded directly from the femoral artery in normotensive and hypertensive rats. The hypertension in denervated rats included an increase of systolic as well as diastolic pressure. The heart rates of quiet hypertensive rats were within the normal range and, in general, no close correlation was observed between increases in blood pressure and elevations in heart rate. Normal rats have marked fluctuations in both pressure and heart rate when walking or when stimulated; these fluctuations were much greater in the neurogenic hypertensive animals. Moreover, the hypertensive rats showed large oscillations of blood pressure synchronous with respiratory movements particularly when the latter were slower and deeper than normal.
The rats seemed to tolerate both the denervation and the hypertension very well. Histological examination of tissues from hypertensive rats showed myocardial hypertrophy and a thickening of the basement membrane of the glomerular capsule. The severity of the latter abnormality was closely associated with the duration of the hypertension.
Pulmonary Vascular Impedance in the Dog
Authors: BERGEL DEREK H. , MILNOR WILLIAM R. 
Published: June 2012

Pulmonary vascular hydraulic input impedance was measured in 13 anesthetized openchest dogs with normal sinus rhythm, and 2 dogs with surgically induced atrioventricular block, by means of electromagnetic flowmeters and strain gauge manometers of known frequency response. The linearity of the pulmonary bed was evaluated by measuring impedance while the heart rate, and hence the pulsatile input to the bed, was varied.
The pulmonary bed behaved as a quasilinear system, within the limits of accuracy of the methods employed and the range of frequencies tested. The use of input impedance, or oscillatory pressure/flow ratio, to describe some characteristics of the bed is therefore justifiable, and analogies with linear models like the simple transmission line are not unreasonable.

The characteristic input impedance averaged 3,094 dyne sec cm
-5
kg, or about one-third the magnitude of the pulmonary vascular resistance, and was therefore a significant part of the total opposition that must be overcome in moving blood through the lungs. This impedance to pulsatile flow is not included in calculations of resistance from mean pressure and flow measurements.

The pattern of the impedance spectrum suggested that reflections originating from arteries 1.0 mm and less in diameter play a large role in determining input impedance and its variations with frequency. Pulmonary vasoconstriction by 5-hydroxytryptamine (serotonin) altered the impedance pattern in a manner consistent with increased wave reflection and displacement of the dominant reflecting sites to positions nearer the main pulmonary artery. Capillary compression by increased intra-alveolar pressure also increased reflection, but did not alter the sites of reflection significantly, providing further evidence that the normal impedance pattern and its modification by serotonin are both determined by the characteristics of the arterial part of the bed.