bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of Renin Activity in Human Plasma
Authors: PICKENS PETER T. , BUMPUS F. MERLIN , LLOYD A. MURRAY , SMEBY ROBERT R. , PAGE LRVINE H. 
Published: June 2012

A method is described for estimating plasma renin activity by using renin substrate present in plasma. This method differs from other indirect renin assay methods by (1) incubation in the absence of ions thus establishing conditions for zero order kinetics for the reaction between endogeneous renin and substrate and (2) the use of angiotensinase inhibitors di-sodium ethylenediamine tetraacetic acid (
EDTA
) and d-isopropylfluorophosphate (DFP). Recoveries of renin added to plasma in levels similar to those occurring in plasma are 85%
SD
±7%.

The incubation was done at pH 5.5 which was shown to be the optimum for human renin reacting with human substrate.
By incubating human plasma samples with known quantities of human renin, evidence was obtained suggesting that factors other than enzyme or total substrate concentrations affect the velocity of angiotensin formation. This variability of reaction rate may be explained by the existence of an inhibitor or activator in this system or by a variation in the type of substrate.
Cardioversion and Digitalis Drugs: Changed Threshold to Electric Shock in Digitalized Animals
Authors: LOWN BERNARD , KLEIGER ROBERT , WILLIAMS JAMES 
Published: June 2012

The relationships between the action of digitalis drugs and the effects of cardioversion were studied in 44 dogs. Ventricular tachycardia provoked by either acetyl strophanthidin (AS) or ouabain could not be reverted to sinus rhythm by DC shock. When ventricular fibrillation was induced electrically during digitalis toxicity, defibrillation could be accomplished readily but the toxic arrhythmia due to digitalis remained unaltered. When ventricular fibrillation was induced by AS, it was also unaffected by repeated high energy discharges.
In control animals the median energy to produce ventricular tachycardia by electrical discharge was 400 watt-seconds. Repeated electrical shocks did not change the level of energy required to produce ventricular tachycardia. However, following recovery from ouabain-induced ventricular tachycardia, the electrical threshold for ventricular tachycardia was 0.2 watt-second. A similar but less consistent response was noted after AS-induced ventricular tachycardia. The sensitization to electrical shock lasted for five to ten minutes after AS and for approximately one hour after recovery from ouabain toxicity. This same phenomenon of sensitization to electrical discharge was observed during digitalization. About 80% of the potentially toxic dose of ouabain had to be administered before the electrical threshold was lowered.
The sensitivity to DC shock in the digitalized animal was not related to any specific phase of the cardiac cycle. Digitalization did not change the duration, location or energy limits of the ventricular vulnerable period.
These experiments lead to the following conclusions of clinical importance: 1) Cardioversion will not be effective in arrhythmias induced by digitalis toxicity and 2) in the presence of overdigitalization cardioversion discharge may provoke serious disturbance of rhythm.
Effect of Velocity Gradient on the Clotting Time of Blood and on the Consistency of Clots Formed in Vitro
Authors: Dintenfass Leopold 
Published: June 2012

Clotting times of human blood and rheology of blood clots have been determined by means of a cone-in-cone viscometer, a ring-in-ring adapter, and a variable-frequency thromboviscometer. The last represents a variable frequency version of the thrombelastograph.
The results of clotting time tests on blood samples from 118 donors indicate clearly that clotting time is a function of the velocity gradient at which clotting takes place. Clotting time decreases as the velocity gradient increases.

Consistency of blood coagula depends on the velocity gradient at which coagula are formed. Consistency, or viscosity, of coagula decreases when the velocity gradient increases. While the viscosity of clots formed at low rates of shear is of the order of 100 poises, coagula formed at intermediate rates of shear exhibit viscosity of a few decipoises. Viscosity of blood is not significantly altered if coagulation takes place at rates of shear near 400 sec
-1
.
Functional Distribution of Right and Left Stellate Innervation to the Ventricles
Authors: Yanowitz Frank , Preston James B. , Abildskov J. A. 
Published: June 2012

Changes of the electrocardiogram and of ventricular refractory period were measured following either unilateral stellate ganglion stimulation or ablation in the open chest dog preparation.
Right stellate ganglionectomy or left stellate stimulation produces prolonged Q-T intervals and increased T-wave amplitude. Left stellate ganglionectomy or right stellate stimulation produces increased T-wave negativity without measurable change in the Q-T interval.
The differing patterns of electrocardiographic wave form resulting from changes in sympathetic tone mediated by right and left stellate innervation could be correlated with changes in ventricular refractory period. Following right stellate ganglionectomy, refractory period prolongations were most marked over the anterior ventricular surface; left stellate ganglionectomy produced the greatest prolongation on the posterior surface.
Although the right and left stellate innervations of the ventricles overlap, the left stellate influence is predominant over the posterior wall of the ventricles, while right stellate influence dominates the anterior ventricular walls.
The electrocardiographic form changes observed following unilateral alteration of sympathetic tone paralleled those electrocardiographic abnormalities seen in patients with lesions of the central nervous system, suggesting a possible functional explanation for these clinical findings.
Hemodynamic and Metabolic Effects of Hemorrhage in Man, with Particular Reference to the Splanchnic Circulation
Authors: Price Henry L. , Deutsch Stanley , Marshall Bryan E. , Stephen George W. , Behar Marjam G. , Neufeld Gordon R. 
Published: June 2012

1. Eleven normal subjects were studied before and after removal of 15 to 20% of their blood volume within 35 minutes.
2. This amount of blood loss did not produce conspicuous effects upon any of the usually measured circulatory or metabolic parameters.
3. The results suggest that the splanchnic circulation functions as an important blood reservoir in man, that it can be preferentially depleted of blood by a mechanism which does not automatically increase vascular resistance, and that the ability of our subjects to tolerate blood loss was attributable in large part to this response.
Specialized Conducting Fibers in the Interatrial Band
Authors: Wagner Michael L. , Lazzara Ralph , Weiss Robert M. , Hoffman Brian F. 
Published: June 2012

The interatrial band (Bachmann's bundle) was studied both in situ, in the adult dog, and in vitro, using excised canine atria. Electrograms recorded from this structure in the intact animal had a double intrinsic deflection during sinus rhythm, and responded to rapid rates of atrial stimulation with alternation in both configuration and cycle length. Potassium infusions which produced atrial arrest with a sinoventricular rhythm did not abolish electrical activity in the interatrial band.
Single fibers of the interatrial band, studied in vitro with microelectrodes, had distinctive transmembrane potentials different from those of ordinary atrial muscle fibers. Action potentials were characterized particularly by a high rising velocity (maximum dv/dt), of the same magnitude as that recorded from Purkinje fibers, and a prominent plateau. These fibers were sensitive to acetylcholine and more resistant to potassium arrest than ordinary atrial fibers. Conduction velocity in the interatrial band was consistently higher than in ordinary atrial muscle. Plots of sequential activation time against linear distance showed different conduction velocities in parallel linear paths, with the highest velocity in the path on the crest of the interatrial band. Due to rapid conduction through the interatrial band, simultaneous activation of right and left atrial points was demonstrated.
It is concluded: 1) The interatrial band is not a homogeneous structure, but contains two fiber types. 2) In addition to ordinary atrial muscle, specialized conducting fibers are present in the interatrial band. 3) Impulse spread in the interatrial band is not radial or uniform. Rather, it occurs through several linear paths which probably have infrequent cross-connections.
A Study of the Mechanisms Involved in the Pulmonary Arterial Pressor Response to Hypoxia
Authors: BERGOFSKY EDWARD H. , HOLTZMAN SEYMOUR 
Published: June 2012

The mechanisms underlying the pulmonary arterial pressor response to hypoxia have been investigated by studying specimens of pulmonary and systemic vascular smooth muscle and the isolated pulmonary and systemic circulations. Hypoxia caused a unique and reversible loss of potassium and gain in sodium by pulmonary arterial smooth muscle that did not occur in pulmonary veins or systemic arteries. These changes in electrolyte concentrations were calculated by the Nernst equation to be associated with depolarization of the smooth muscle cell of the pulmonary artery. Moreover, artificial hyperpolarization and depolarization in the isolated perfused pulmonary circulation were attended by blunting and accentuation, respectively, of the pulmonary arterial pressor response to hypoxia.
Such data suggest that one of the actions of hypoxia on the pulmonary circulation involves a depolarization of the muscle cell so that it is closer to its excitatory threshold and thereby more readily able to diminish the cross-sectional area of the pulmonary vascular bed.
Effects of Sympathetic Nerve Stimulation on the Pulmonary Arterial Tree of the Isolated Lobe Perfused in Situ
Authors: INGRAM ROLAND H. , SZIDON J. PETER , SKALAK RICHARD , FISHMAN ALFRED P. 
Published: June 2012

The hemodynamic response to sympathetic nerve stimulation (SNS) was studied in canine lung lobes isolated in situ and perfused with a pulsatile pump. For the same input pulse, both the rate of rise and the rate of fall of pulmonary arterial pressure increased during SNS; the peak systolic pressure was also higher during SNS, whereas diastolic pressure levels were either at, or below, control levels. The increase in pulse pressure produced little or no change in mean pulmonary artery pressure and resistance. During SNS, compliance per unit length in large arteries fell, pulse wave velocity increased, and elastic modulus increased. Phenoxybenzamine produced opposite changes. Norepinephrine injections increased resistance and produced smaller compliance changes than SNS.
Flow loads imposed by short bursts of rapid pump rate at constant stroke volume caused increments of vascular volume which returned to control levels after return to the slower rate. Volume increments were smaller and restoration rates faster during SNS than during control. After phenoxybenzamine, volume increments were larger and restoration rates slower than control.
The results indicate that the distensibility of the large pulmonary arteries and the precapillary bed is decreased during sympathetic stimulation, while calculated resistance is not changed.
Arterial Wall Vibration Distal to Stenoses in Isolated Arteries of Dog and Man
Authors: FOREMAN JOHN E. K. , HUTCHISON KENNETH J. 
Published: June 2012

It has been suggested that poststenotic weakening of arterial walls is caused by arterial wall vibration and structural fatigue initiated by pressure disturbances in turbulent blood flow. We examined the frequency spectra of wall vibration downstream from experimental arterial stenoses and compared them with the natural resonant vibration characteristics of the artery walls.
Spectra of arterial wall displacement of isolated perfused dog and human arteries were measured with a noncontacting capacitance transducer during conditions of fluid flow through the artery; resonant vibration characteristics were determined during pure sine and random sound stimulation of the artery walls in the absence of flow.
It is concluded that fluid flow through isolated arteries with an experimental stenosis excites the artery wall to vibrate over a wide range of frequencies within which are discrete frequencies that coincide with the resonant frequencies of the artery wall.
Hydrodynamic Forces in Dissecting Aneurysms
Authors: PROKOP EDWARD K. , PALMER ROGER F. , WHEAT MYRON W. 
Published: June 2012

It has been argued that pulse wave characteristics are important factors in extension and rupture of acute dissecting aneurysms. To test this, a standard model of an aorta was constructed, consisting of an outer layer of Tygon tubing and an inner layer of rubber cement. An "intimal tear" was produced and the "aorta" was subjected to nonpulsatile and pulsatile flow with increasing increments of pressure.
With nonpulsatile flow alone (97 experiments) no dissection occurred at pressures up to 400 mm Hg. Pulsatile flow produced rapid and usually complete dissection with a maximum systolic pressure of 120 mm Hg.

The extent of dissection per pulse was related to dp/dt
max
in the fluid. No dissection occurred until a critical value of dp/dt
max
(790 mm Hg/sec) was reached. Dog aortas were then used in place of the Tygon tube "aorta" with similar results; i.e., dissection did not occur with nonpulsatile flow, but did occur with pulsatile flow (3800 mm Hg/sec). The dissecting dog aorta ruptured to the outside or reentered the vessel lumen.

It was concluded that pulse wave characteristics, particularly dp/dt
max
, are important in the propagation of dissection.
Protective Role of Increased Myocardial Glycogen Stores in Cardiac Anoxia in the Rat
Authors: SCHEUER JAMES , STEZOSKI S. William 
Published: June 2012

To determine whether increased glycogen stores might protect the heart against anoxia, experiments were performed in the isolated perfused rat heart. Marked differences in cardiac glycogen were produced by comparing hearts from rats previously treated with reserpine with hearts from control rats. Lesser differences in cardiac glycogen were produced in hearts by perfusing them for 15 minutes without glucose (0 mM glucose) or with 20 mM glucose. Both groups were then studied during a 5-minute anoxic cycle with 5 mM glucose as the exogenous substrate. Hearts from the reserpine-treated rats had higher left ventricular pressures, maximal rate of left ventricular pressure rise, and lactate output after 2 minutes of anoxia than the hearts from control rats. Similar but less marked mechanical differences were observed between 0 mM glucose and 20 mM glucose hearts. The mechanical differences during anoxia between the two groups were not abolished by simultaneous L-norepinephrine administration. Hearts with greater initial glycogen stores had higher glycogenolytic rates, and proportionately more lactate was produced from glycogen than from glucose. Thus, anaerobic ATP production per mole of hexose was greater in hearts with higher glycogen stores. Calculated ATP production was also greater in hearts from the reserpine-treated rats than in those from control animals.
These studies demonstrate that both marked and minor elevations in cardiac glycogen are associated with greater glycolytic reserve and improved mechanical resistance to anoxia. This appears to be mainly due to enhanced glycogenolysis and anaerobic ATP production.
Hypercoagulability Induced by Hyperlipemia in Rat, Rabbit and Man
Authors: Renoud S. , Lecompte S. 
Published: June 2012

Feeding a butter-rich diet to rats induced a "hypercoagulable state," since multiple large thrombi were observed in response to injection of
S. typhosa
endotoxin but the same stimulus was ineffective in rats fed a corn oil-rich diet or laboratory chow. In vitro hypercoagulability was noted in blood from the butter-fed rats, the recalcification plasma clotting time (PCT) being reduced by 34 to 45% in comparison with the controls. When a phospholipid suspension replaced the platelets in the plasma clotting test, the reduction was only 5 to 15%, but it was 31 and 43% when the platelets of these rats were washed and resuspended in a given standard plasma. Since lipid extract of these platelets could largely reproduce their activity, the factor involved must have been factor 3.

A similar result was obtained in rabbits fed a butter or corn oil diet, or laboratory chow, indicating that, in this species also, the hypercoagulability in response to hyperlipemia was largely due to factor 3. In addition, in rats and rabbits fed butter, the platelets were more susceptible to thrombin-induced aggregation.
In 27 human subjects of either sex and various ages, the state of coagulability as determined by the PCT was also mostly related to the platelet factor 3 activity, which was negatively correlated with serum cholesterol.
Effects of Norepinephrine on Coronary Circulation and Left Ventricular Dynamics in the Conscious Dog
Authors: VATNER STEPHEN F. , HIGGINS CHARLES B. , BRAUNWALD EUGENE 
Published: June 2012

The effects of norepinephrine (0.1 and 1.0 µg/kg, iv) on coronary blood flow and resistance, left ventricular pressure and diameter, dP/dt, (dP/dt)/P, and the velocity (V
ISO
) of myocardial fiber shortening were studied in conscious dogs. When the heart rate was held constant, norepinephrine caused an initial reduction in coronary vascular resistance which was associated with increases in mean arterial blood pressure, systolic left ventricular pressure, end-diastolic diameter, dP/dt, (dP/dt)/P, and V
ISO
. After this brief coronary vasodilator response, a sustained increase occurred in mean coronary vascular resistance (+0.55 ± 0.07 mm Hg/ml min
-1
), and increases persisted in mean arterial blood pressure (+67 ± 7 mm Hg), left ventricular systolic pressure (+74 ± 6 mm Hg), left ventricular end-diastolic pressure (+4 ± 1 mm Hg), left ventricular internal diameter (+1.3 ± 0.3 mm), peak dP/dt (+1660 mm Hg/sec), (dP/dt)/P (+15 ± 2 sec
-1
), and V
ISO
(+11 ± 2 mm/sec); coronary sinus Po
2
decreased. Beta-receptor blockade prevented the inotropic effects of norepinephrine, attenuated the early coronary vasodilator effects, and increased the late vasoconstrictor effects. Alpha-receptor blockade abolished the late coronary vasoconstrictor effects of norepinephrine; only dilatation occurred. In contrast to the effects of norepinephrine in conscious dogs without autonomic blockade	, norepinephrine (1.0 µg/kg, iv) failed to produce late coronary vasoconstriction in anesthetized, open-chest dogs; only dilatation occurred. Thus, in the normal, conscious dog, norepinephrine exerts an important coronary vasoconstrictor effect which is sufficiently intense to counteract completely the simultaneous tendency toward metabolic vasodilatation.
Ventricular Endomyocardial Pathology Produced by Chronic Cardiac Lymphatic Obstruction in the Dog
Authors: MILLER ALBERT J. , PICK RUTH , KATZ LOUIS N. , Jones Charles , Ellis Anthony , Malasan John 
Published: June 2012

Chronic impairment of cardiac lymph flow was successfully accomplished in 22 dogs after preliminary anatomic studies revealed a feasible surgical technic. The anatomic and surgical details are presented. Gross and microscopic studies were possible in 19 of the operated animals, 3 of which died spontaneously, and 16 of which were sacrificed at varying time intervals between 2 and 16 weeks after surgery. Two of the 19 dogs were completely normal on gross and histologic examination. Abnormalities found in the remaining 17 animals included left and right ventricular subendocardial hemorrhages, increased elastic and fibrous tissue in the left ventricular endocardium, and opacification of the mitral valve leaflets.
It is concluded that chronic impairment of cardiac lymph drainage is productive of significant endomyocardial pathology. These observations are considered to be important as possible etiologic mechanisms in endomyocardial fibrosis and endocardial fibroelastosis. The cardiac lymphatics merit continued intensive investigation, inasmuch as they surely have an important role in cardiac physiology and pathology. Their importance may encompass a far broader area than suggested above. They may be related to the so-called nutritional cardiopathies. The fibroplastic effects of serotonin might occur through an effect on the cardiac lymphatics. Impairment of heart lymph flow may be important in endocarditis and myocarditis of certain types, for it is known that chronic lymphatic obstruction predisposes to recurrent inflammation and infection in the affected parts.
Incidence of Infective Endocarditis Caused by Viridans Group Streptococci Before and After Publication of the 2007 American Heart Association's Endocarditis Prevention Guidelines
Authors: DeSimone Daniel C. , Tleyjeh Imad M. , Correa de Sa Daniel D. , Anavekar Nandan S. , Lahr Brian D. , Sohail Muhammad R. , Steckelberg James M. , Wilson Walter R. , Baddour Larry M. 
Published: June 2012

Background—
The American Heart Association published updated guidelines for infective endocarditis (IE) prevention in 2007 that markedly restricted the use of antibiotic prophylaxis in certain at-risk patients undergoing dental and other invasive procedures. The incidence of IE caused by viridans group streptococci (VGS) in the United States after publication of the 2007 American Heart Association guidelines has not been reported.

Methods and Results—

We performed a population-based review of all definite or possible cases of VGS-IE using the Rochester Epidemiology Project of Olmsted County, Minnesota. Patient demographics and microbiological data were collected for all VGS-IE cases diagnosed from January 1, 1999, through December 31, 2010. We also examined the Nationwide Inpatient Sample hospital discharge database to determine the number of VGS-IE cases included between 1999 and 2009. We identified 22 cases with VGS-IE in Olmsted County over the 12-year study period. Rates of incidence (per 100 000 person-years) during time intervals of 1999–2002, 2003–2006, and 2007–2010 were 3.19 (95% confidence interval, 1.20–5.17), 2.48 (95% confidence interval, 0.85–4.10), and 0.77 (95% confidence interval, 0.00–1.64), respectively (
P
=0.061 from Poisson regression). The number of hospital discharges with a VGS-IE diagnosis in the Nationwide Inpatient Sample database during 1999–2002, 2003–2006, and 2007–2009 ranged between 15 318 to 15 938, 16 214 to 17 433, and 14 728 to 15 479, respectively.

Conclusions—
On the basis of data complete through 2010, there has been no perceivable increase in the incidence of VGS-IE in Olmsted County, Minnesota, since the publication of the 2007 American Heart Association endocarditis prevention guidelines.