bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Selective Coronary Embolization on Coronary Blood Flow and Coronary Sinus Venous Blood Oxygen Saturation in Dogs
Authors: West James W. , Kobayashi Tachio , Anderson Fred S. 
Published: June 2012

The cardiovascular effects of selective coronary embolization were studied with improved techniques in an attempt to obtain evidence for the existence of intercoronary reflexes and their role in potentiating myocardial ischemia.
These studies demonstrated that embolization of the coronary arterial bed by lycopodium spores produced an initial marked decrease in coronary blood flow followed by a maintained (approximately 10 minutes) increase which was accompanied by an increase in coronary sinus venous oxygen saturation. Supporting evidence was obtained from selective coronary angiograms and from changes in coronary vascular resistance. Attempts at eliminating these responses by certain autonomic blocking agents (atropine, hydralazine, tetraethylammonium chloride, hexamethonium, and dibozane), surgical denervation of the heart, and adrenalectomy were all ineffective. Experimental evidence obtained by comparing the initial effect of embolization with pitressin vasoconstriction and coronary occlusion all led to the conclusion that reflex coronary spasm does not occur during coronary occlusion. The cause of the initial decrease in coronary blood flow during embolization (lycopodium spores) is, therefore, mechanical block within the distribution of the vessel by the emboli.
Renin, A Physiologic Regulator of Renal Hemodynamics?
Authors: Schmid Herman E. 
Published: June 2012

1. Injections of hog renin and formation of antirenin in the dog will prevent or reduce the elevation of blood pressure associated with constriction of the renal arteries, but will not affect the systemic blood pressure in the normal animal.
2. The kidneys of both the normal and renal artery constricted animal respond with an increase in renin content during hog-renin injections which correlates closely with the serum antirenin titer.
3. The juxtaglomerular cell appears to be the site of renin formation and in this location may affect postglomerular vascular resistance.
4. Dogs with high titers of antirenin apparently have a reduced capacity to respond to an alteration in postglomerular resistance.
5. It is proposed that renin formation is controlled normally by a pressure-sensitive feedback mechanism operating across the glomerulus between the juxtaglomerular cell and postglomerular resistance.
Hemodynamic Changes in Fetal Lamb in Utero in Response to Asphyxia, Hypoxia, and Hypercapnia
Authors: Assali N. S. , Holm L. W. , Sehgal N. 
Published: June 2012

The effects of hypoxia (administration of 10 per cent O
2
in N
2
and constriction of the uterine arteries), of hypercapnia (administration of 8 per cent CO
2
in air), and of asphyxia (obstruction of the umbilical circulation) were studied on the fetus in utero in near-term pregnant ewes under spinal anesthesia.

Hypoxia and hypercapnia produced increases in the maternal arterial pressure, maternal heart rate, and uterine blood flow. Fetal arterial pressure and carotid and umbilical blood flows increased, while the fetal heart rate decreased. Fetal femoral flow decreased during hypoxia and increased during hypercapnia. There was a delay of five to six minutes between the initiation of hypoxia or hypercapnia and the appearance of fetal circulatory changes.
Transient reduction of uterine blood flow evoked insignificant hemodynamic alterations in the mother and fetus. A reduction of flow greater than 50 per cent of control values produced a fetal bradycardia along with increases in fetal arterial pressure, carotid and umbilical flows.
Constriction of the umbilical veins with the umbilical arteries intact produced a prompt bradycardia together with a decrease in fetal arterial pressure and regional blood flows. Constriction of the umbilical arteries alone also produced a bradycardia with an initial rise in arterial pressure and carotid flow. Similar changes were observed after cutting the umbilical cord. Elimination of the low resistance of the placenta played a major role in these changes.
Placing the lamb in the head-down position caused a marked increase in carotid blood flow without greatly modifying arterial pressure.
Comparison of Adrenergic Activation by Anticholinesterases and by Hypoxia
Authors: Varagić Vladislav M. , Beleslin Duŝan B. 
Published: June 2012

The hypertensive response to eserine in the rat is accompanied by an increase in lung resistance to inflation. Usually, these two effects do not occur simultaneously. The effects of acute hypoxemia on the blood pressure of the rat were found to be variable, ranging from a biphasic effect to a pure hypertension or hypotension. Inhalation of 11 per cent oxygen in nitrogen produced only a fall of blood pressure.
Bretylium was found to block the hypertensive response to eserine, while leaving intact the effect of eserine on the bronchi. On the other hand, bilateral vagotomy was found to block the effect of small doses of eserine on the bronchi and not to affect the blood pressure response to eserine.
Neostigmine caused a small rise of blood pressure and a very significant bronchoconstriction. It is concluded that bronchoconstriction and subsequent hypoxia might contribute to the hypertensive response to eserine in the curarized rat, but this mechanism does not seem to be of primary importance for a hypertensive action of eserine.
Hypocholesteremic Effect of Phenoxybenzamine (Dibenzyline), An Adrenergic Blocking Agent
Authors: Jagannathan S. N. , Srikantia S. G. , Gopalan C. 
Published: June 2012

The effect of an orally effective adrenergic blocking agent, Dibenzyline, on serum cholesterol levels was studied in human subjects and in monkeys on high-fat diets. In addition, the effect of the phenoxyethyl analogue of Dibenzyline, G-D 131, was also investigated in monkeys.
The studies showed that the increase in serum cholesterol level brought about by a high-fat diet in monkeys could be considerably reduced by supplementation with Dibenzyline. This hypocholesteremic action was also observed with the analogue of Dibenzyline, G-D 131, which does not possess the adrenergic blocking property. It appears, therefore, that the hypocholesteremic action of Dibenzyline is independent of its adrenergic blocking activity. When a high-fat diet which also contained a high amount of cholesterol was used, Dibenzyline retarded the increase in serum cholesterol of monkeys for a considerable length of time.
Administration of Dibenzyline, 10 mg. daily for 11 days, brought about a fall in serum cholesterol in two of the three human subjects and arrested the further increase in serum cholesterol in the third subject on a high-butterfat diet. All the subjects showed increased fecal elimination of cholic and dihydroxycholanic acids during the Dibenzyline-supplemented period, suggesting that the hypocholesteremic effect of the drug is at least partly mediated through increased elimination of cholesterol as bile acids.
Effect of Angiotensin on Juxtaglomerular Cells and Vessels of the Kidney
Authors: Katz Yale J. , Patek Paul R. , Bernick Sol 
Published: June 2012

Angiotensin II, given subcutaneously in pressor doses to rats three times a day, causes a prompt increase in the size and granulation of the juxtaglomerular cells. After one week of angiotensin injections, there is some loss of granules from these cells. Concurrently, degenerative changes develop in the intrarenal arteries. These changes may result from vasoconstriction in the vessels proximal to the afferent arterioles.
Epinephrine given in an amount similar in pressor effect to angiotensin II did not produce these changes. Vascular lesions were not seen in the heart, lung, brain, aorta, liver, and spleen of animals given angiotensin over the two-week injection period. This study provides additional evidence that the vessels of the kidney are uniquely sensitive to angiotensin.
Removal of Distortion from Indicator Dilution Curves with Analog Computer
Authors: COOPER JAMES K. , SCHWEIKERT J. ROBERT , ARNOLD THOMAS G. , LACY WILLIAM W. 
Published: June 2012

A method has been developed for characterizing quantitatively, and for removing from indicator dilution curves, the distortion introduced by catheter sampling systems.
The method involves a specially constructed cuvette and analog computer analysis of the curves recorded by densitometers placed at the entrance of the catheter and at points downstream.
This method of correction of distortion is based on a general theory of function transformation which is applicable to all situations and not upon empirically established constants which are only valid in special situations.
The geometry (coiling, bending) of the catheter has been found to affect the distortion. Disruption of the flow pattern by insertion of a braided wire in the lumen causes less variation of the distortion caused by bending and coiling.
Distortion was not significantly affected by change in blood temperature in our system.
Conduction of Cardiovascular Sound Along Arteries
Authors: FARBER J. JOB , PURVIS JAMES H. 
Published: June 2012

The velocity of the transmission of the second heart sound in the thoracic aorta of dogs was measured. The average velocity was found to be 5.7 meters per second. The figure agrees well with the published figures for the pulse wave velocity in the thoracic aorta of dogs.
It was shown in humans that the velocity with which the second heart sound is conducted along the carotid artery does not change appreciably with frequency between 25 and 100 cycles per second. The average increase in velocity of 2.7% per half octave increase in frequency is, with 30% probability, due to random errors.
The fraction of the energy of a murmur transmitted in the form of a transverse vibration along the abdominal aorta of dogs was estimated from recordings made before and after the transverse motion of the arterial wall was impeded with a clamp. Most of the energy of the murmur was found to be transmitted in the form of a transverse vibration in the aortic wall.
It was concluded that most of the energy of cardiovascular sound in arteries is transmitted in a mode which is exactly analogous to the transmission of the pulse wave.
Some puzzling features of intravascular sound conduction, such as the apparent transmission of murmurs mainly in the direction of flow, could be explained on this basis.
Myocardial Necrosis in Rats: Serum Enzymes, Adrenal Steroid and Histopathological Alterations
Authors: Wexler Bernard C. , Kittinger George W. , Springs Myra E. , Conatser DHman 
Published: June 2012

Acute infarctoid myocardial necrosis has been produced in virgin rats by injection of isoproterenol. The lesions are essentially identical, both grossly and microscopically, with naturally occurring acute infarcts which we have observed in arteriosclerotic breeder rats.
During the establishment of drug-induced necrosis the animals displayed signs of shock and congestive heart failure. Serum transaminases and lactic dehydrogenase levels underwent changes which coincided with the establishment and repair of the myocardial damage. The male rats had a higher mortality rate than the females. The male rats also developed more massive myocardial necrosis and showed a decreased capacity to repair myocardial damage. The adrenal glands became greatly hypertrophied and the thymus became severely involuted coincident with the acute establishment of the myocardial lesion. In vitro studies indicated that changes in adrenal function also accompanied the acute onset of myocardial destruction. The adrenal hypertrophy decreased during recovery from shock and during repair of the lesion.
Damping of Sound on the Chest Surface
Authors: FABER J. Job 
Published: June 2012

The damping of sound during its transmission over the chest wall was measured in humans in order to establish whether the heart sounds spread in two-dimensions over the chest wall from their auscultatory areas, or in three-dimensions directly from their origins deep in the body.
The damping of frequencies from 50 to 400 cycles/sec in soft tissues and ribs can be predicted by an equation which consists of a geometrical term and a term due to viscous damping.
The term which represents the viscous damping in the soft tissues and ribs of the chest wall is proportional to the square root of the frequency.
The value of the geometrical term suggested that the intensity of the sounds was inversely proportional to the distance travelled, rather than inversely proportional to the square of the distance travelled. The former relationship would apply if the sound travels in a two-dimensional plane of material rather than in a three-dimensional volume. This is consistent with our earlier finding that the heart sounds travel from the heart to their auscultatory areas on the chest and from there over the chest surface.
For frequencies under 100 cycles/sec, the chest wall appears to be homogenous. For frequencies above 100 cycles/sec, the damping is much less for transmission over the sternum than for transmission elsewhere on the precordium.
Sustained Depressor Effect of Renal Medullary Extract in the Normotensive Rat
Authors: LEE JAMES B. , HICKLER ROGER B. , SARAVIS CALVIN A. , THORN GEORGE W. 
Published: June 2012

Crude homogenates of rabbit, medulla produced a sustained depression of blood pressure when injected intravenously into the normotensive, anesthetized, pentolinium-treated rat. Similar activity was present in rat medulla, but not in extracts of renin-free cortex or certain nonrenal tissues.
The sustained depressor activity of medulary extract possessed different physiological and chemical characteristics from the shortacting nucleotide depressor activity which is present in both cortical and medullary extracts. In addition, prolonged medullary depressor activity was separable from medullary nucleotide activity by column chromatography.
The activity responsible for sustained depressor activity was a dialyzable, ethanol soluble, low molecular weight(<4500 mol wt) substance(s) which was resistant to a mixture of peptide hydrolases and destroyed by heating for one hour at 100°C.
Lipid Pattern in Experimental Canine Atherosclerosis
Authors: GUIDRY MARION A. , GEER JACK C. , ROBERTSON WILLIAM B. 
Published: June 2012

An experiment was conducted to compare the effects of feeding cholesterol alone, thiouracil alone, and cholesterol and thiouracil combined, on the serum lipids and arteries of dogs. These substances were added to a basal diet rich in linoleic acid. Serum cholesterol and total serum lipids were determined periodically during the four-month period of feeding, and serum and tissue lipids obtained at necropsy were fractionated and analyzed by silicic acid column and gas chromatography.
During the period of feeding the experimental diets, three levels of hypercholesterolemia and hyperlipemia were produced. The smallest increase over control levels occurred in the animals receiving cholesterol alone; an intermediate increase was produced in those receiving thiouracil alone; and the greatest increase occurred in the group receiving both cholesterol and thiouracil. The lipemia was proportional to the cholesterolemia in each of the experimental groups. Only those dogs receiving both cholesterol and thiouracil developed arterial lesions.
Coronary and Myocardial Actions of Angiotensin
Authors: FOWLER NOBLE O. , HOLMES JOHN C. 
Published: June 2012

In the dog heart-lung preparation, single injections of 40 µg angiotensin II produced consistently a biphasic response. Initial impairment of cardiac function was observed with decrease of cardiac output and of ventricular force, and with increase of atrial pressures. After 10 to 20 seconds, there was a positive inotropic effect, with an increase of cardiac output and of ventricular force, and a decrease in atrial pressures. Responses were comparable in reserpinized and nonreserpinized preparations. Tachyphylaxis to angiotensin was found consistently in the heart-lung preparation, with a regular decrease in response following second and third injections. A positive inotropic action of angiotensin II was demonstrated in the cat papillary muscle preparation. These studies demonstrated that angiotensin has a direct cardiac action, namely a positive inotropic effect. This action probably does not depend upon myocardial stores of catecholamines.
When the left anterior descending coronary artery of the dog was perfused with blood at a constant flow, single intracoronary injections of angiotensin (1.0 µg) consistently increased coronary resistance (6% to 92%). Continuous intracoronary infusion of angiotensin increased coronary vascular resistance when blood concentrations were as low as 0.42 µg/ liter. No evidence of initial cardiac depression or of increased coronary vascular resistance was found after norepinephrine.
It is concluded that the initial impairment of cardiac performance following angiotensin is caused at least in part by decreased coronary blood flow. Caution is suggested in the use of angiotensin in the treatment of human shock because of its action upon the coronary circulation.
Humoral Transmission of Cardiorespiratory Changes in Experimental Lung Embolism
Authors: Halmagyi DENIS F. J. , STARZECKI BOLESLAV , HORNER GEORGE J. 
Published: June 2012

Pairs of sheep were connected via a unilateral carotid-jugular anastomosis in fourteen experiments. With the cross circulation open, pulmonary embolism induced in the donor sheep produced a rise in pulmonary arterial pressure, a fall in lung compliance, and an increase in ventilation in the recipient animal. The transmitted effects were more pronounced with barium sulfate lung embolism than with blood clot lung embolism.
These observations are consistent with the assumption that in acute experimental lung embolism a humoral agent is being released causing constriction of the lung vessels and airways.
Cardiac Arrhythmias Produced by Catecholamines in Anesthetized Dogs
Authors: MOORE E. NEIL , MORSE HOWARD T. , PRICE HENRY L. 
Published: June 2012

1. Electrograms have been recorded simultaneously from the right atrium, bundle of His, and both ventricles, together with the lead II electrocardiogram in dogs receiving cyclopropane and oxygen. Following the administration of norepinephrine, both bigeminal rhythms and monofocal ventricular tachycardias were observed.
2. In our studies both the coupled and the monofocal ventricular beats originated distal to the His electrode.
3. The mechanism of the coupled beats could not be analyzed using either gross or intracellular recording methods; the monofocal tachycardias appeared to result from increased pacemaker activity in the ventricular conducting system.
4. The present results emphasize the hazards of proposing mechanisms to explain arrhythmias solely on the basis of electrocardiographic evidence.
Electrocardiographic Patterns During Resuscitation After Experimentally Induced Ventricular Fibrillation
Authors: MILLER DAVID I. , NACHLAS MARVIN M. 
Published: June 2012

Continuous closed-chest massage (mechanized and manual) and ventilation with pure oxygen were performed for 15 and 30-minute periods, to maintain viability in 43 dogs with electrically induced ventricular fibrillation. External countershocks were applied and 32 of the animals lived more than 48 hours. The return of electrical and hemodynamic functions of the heart, as well as the function of the central nervous system, were graded arbitrarily to characterize recovery from poor to excellent. Electrocardiographic changes (lead II) were studied in detail and compared with the gross result of survival or death, and also with more quantitative characterization of recovery.
When the initial electrocardiogram after defibrillation contained a P wave, the prognosis was most favorable. When the P wave was absent the amount of ST segment depression in the initial complex differentiated the better from the poorer results.
During the first hour following defibrillation, a variety of arrhythmias was noted, as well as varying degrees of change in the R, T, and ST portions of the electrocardiogram. The most serious arrhythmias, in decreasing severity, were idioventricular rhythm, atrio-ventricular block, and multiple premature ventricular contractions. Recovery was poorest when multiple arrhythmias occurred. Changes in the voltage of the R and T waves could not be correlated with prognosis. However, more favorable recoveries were noted in animals without significant changes in the ST segment than in animals having ST segment depression greater than 4 mm.
Interaction of Mean and Pulse Pressures in the Circulation of the Isolated Dog Tongue
Authors: ROVICK ALLEN A. , ROBERTSON PATRICIA A. 
Published: June 2012

In the isolated, perfused dog's tongue, alterations of pulse pressure, at constant mean pressure, can produce parallel or oppositely directed changes in blood flow or can leave the flow unaffected. Parallel changes occur when the vascular bed is passively distensible; opposite changes occur when active contraction of smooth muscle overcomes the effects of passive distensibility, and no change is found when the two effects balance. The first is seen at mean pressures below 80 mm Hg or peak pressures above 155 to 165 mm Hg. The other reactions are produced in the mean pressure range in which autoregulatory reactions occur, viz. opposite changes when the pulse pressure is low and no change under conditions close to in situ mean and pulse pressure. Even when pulse pressure has no observable influence on flow, therefore, it modifies vascular tone.
The active response of vascular smooth muscle to pulse pressure persists in part after the removal of the stimulus, opposing stress-relaxation of resistance vessels. Tissue weight changes reflect alterations in capacitance vessel volume which may vary in direction from the volume changes occurring in resistance vessels.
Cocaine-Induced Incomplete Bundle Branch Block in Dogs
Authors: WATT THOMAS B. , PRUITT RAYMOND D. 
Published: June 2012

Cocainization of a segment of the right or left bundle branch in the canine heart permitted observation of the phenomenon of incomplete bundle branch block in its dual expressions, namely, alterations in the action potential of the respective bundle branch and alterations in the ventricular complexes of the limb-lead electrocardiogram. As the effects of cocainization waned, the bundle action potential reflected intermediate stages between complete block of conduction and normal conduction. Likewise, the attendant ventricular complexes reflected intermediate stages between that form traditionally associated with complete block of the corresponding bundle and normal form. Characteristic shift in direction of the near-terminal QRS axis occurred with and without significant prolongation in QRS.
Cocainization of a segment of the common bundle resulted in first, second, or third degree atrioventricular block, unattended by changes in form of associated ventricular complexes. As in bundle branch block, regression of common bundle block occurred also in stepwise fashion.