bluuebunny/crossref_metadata_2025 huggingface dataset:
Endothelium-dependent vascular responses in normotensive and hypertensive Dahl rats.
Authors: Lüscher T F , Raij L , Vanhoutte P M
Published: June 2012

Experiments were designed to study endothelium-dependent responses in salt-sensitive (DS) and salt-resistant Dahl rats (DR). The rats were fed a low sodium (0.1% NaCl) or high sodium (8% NaCl) diet for 8 weeks. Blood pressure in DS fed a high sodium diet was higher than that in the remaining animals. Aortic rings with and without endothelium were suspended for isometric tension recording. Acetylcholine, adenosine 5'-diphosphate, and thrombin induced endothelium-dependent relaxations that were significantly depressed in the aorta of DS fed a high sodium diet. The relaxations in response to sodium nitroprusside were only slightly, but significantly, depressed in DS fed a high sodium diet. Removal of the endothelium greatly enhanced the response to serotonin and norepinephrine. In rings with, but not without, endothelium taken from rats fed a high sodium diet, the tension developed in response to serotonin and norepinephrine was significantly greater than that in animals fed a low sodium diet. These experiments indicate that endothelium-dependent relaxations to acetylcholine, adenosine 5'-diphosphate, and thrombin are depressed in hypertensive Dahl rats; this effect probably reflects a decreased release of endothelium-derived relaxing factor(s), although structural changes might contribute; and the responsiveness to vasoconstrictor agents is increased in DS and DR fed a high sodium diet. These findings may indicate differential effects of blood pressure and dietary salt on endothelial function.
Alerting reaction and rise in blood pressure during measurement by physician and nurse.
Authors: Mancia G , Parati G , Pomidossi G , Grassi G , Casadei R , Zanchetti A
Published: June 2012

Blood pressure was monitored by a continuous intra-arterial recording in 46 subjects to investigate whether the alarm reaction and the blood pressure and heart rate increases that occur during cuff blood pressure measurement made by a physician 1) attenuate when the physician's visit is repeated several times and 2) are less pronounced if a nurse measures the blood pressure. In 16 subjects the peak mean blood pressure and heart rate rises that occurred in the early part of the physician's first visit (22.6 +/- 1.8 mm Hg and 17.7 +/- 1.7 beats/min) were virtually identical to those occurring during three subsequent visits by the same physician throughout a 2-day intra-arterial blood pressure monitoring. The less pronounced pressor and tachycardic responses observed in the last part of the physician's visit also were virtually identical among the four visits. In contrast, in 30 other subjects the blood pressure and heart rate rises that occurred during the nurse's visit were 46.7% and 42.1% less (p less than 0.01) than those occurring during the physician's visit. The late and less pronounced pressor and tachycardic responses to the visit were also significantly less (p less than 0.01) in the former than in the latter condition. These results indicate that the error of overestimation of blood pressure inherent in cuff blood pressure measurement by a physician cannot be avoided by repeated visits by the physician over a short time span. It clearly can be reduced, however, if blood pressure measurements are performed by a nurse.
Intracellular calcium and sodium in hypertensive patients.
Authors: Cooper R S , Shamsi N , Katz S
Published: June 2012

Untreated subjects with mild to moderate hypertension were compared with normotensive controls recruited from the same ambulatory screening clinic. All subjects were black. Resting levels of cytosolic free calcium were estimated in washed platelets with the fluorescent intracellular probe fura 2, and sodium and potassium were measured in red blood cells. Calcium levels were 21% higher in the hypertensive subjects (p = 0.02), and a 9% increase in sodium was observed in an expanded sample (p = 0.04). Neither intracellular calcium nor intracellular sodium had a significant linear correlation with blood pressure when hypertensive subjects and controls were examined separately or when the two groups were combined. Potassium was slightly but not significantly increased in hypertensive subjects. Among the participants for whom both calcium and sodium measurements were available, a weak, nonsignificant correlation between these ions was noted (r = 0.2; n = 48). This correlation was significant among participants in the control group examined separately (r = 0.3; n = 33; p = 0.05). Although the measurements were performed in different cell lines, these findings demonstrate increases in both intracellular calcium and sodium in hypertensive humans.
Inhibition of sympathoadrenal activity by atrial natriuretic factor in dogs.
Authors: Holtz J , Sommer O , Bassenge E
Published: June 2012

In six conscious, trained dogs, maintained on a normal sodium intake of 2 to 4 mEq/kg/day, sympathetic activity was assessed as the release rate of norepinephrine and epinephrine during 15-minute i.v. infusions of human alpha-atrial natriuretic factor. Mean arterial pressure (as a percentage of control +/- SEM) during randomized infusions of 0.03, 0.1, 0.3, or 1.0 microgram/kg/min was 99 +/- 1, 95 +/- 1 (p less than 0.05), 93 +/- 1 (p less than 0.01), or 79 +/- 6% (p less than 0.001), respectively, but no tachycardia and no augmentation of the norepinephrine release rate (up to 0.3 microgram/kg/min) were observed, which is in contrast to comparable hypotension induced by hydralazine or nitroglycerin. The release rate of epinephrine (control, 6.7 +/- 0.6 ng/kg/min) declined immediately during infusions of atrial natriuretic factor to a minimum of 49 +/- 5% of control (p less than 0.001) during 0.1 microgram/kg/min and to 63 +/- 5% (0.1 greater than p greater than 0.05) or 95 +/- 13% (not significant) during 0.3 or 1.0 microgram/kg/min. Steady state arterial plasma concentrations of atrial natriuretic factor were 39 +/- 10 pg/ml (n = 6) during infusions of saline and 284 +/- 24 pg/ml (n = 6) and 1520 +/- 300 pg/ml (n = 9) during 0.03 and 0.1 microgram/kg/min infusions of the factor.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiovascular responses to acute stress in young-to-old spontaneously hypertensive rats.
Authors: Yamamoto J , Nakai M , Natsume T
Published: June 2012

Age-related changes in circulatory responses to short-term shaker stress were investigated in conscious spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Hemodynamics (microspheres) were measured at 8, 24, 48, and 96 weeks of age, and plasma catecholamines were measured at 8 and 96 weeks. At rest, elevated mean arterial pressure was associated with unaltered cardiac index and heart rate in SHR compared with WKY at all ages. Regional blood flow was largely similar in both strains, except for a reduced renal flow in 96-week-old SHR. Cardiac index and most regional blood flow tended to or did decline in both strains between 8 and 96 weeks. Plasma catecholamines were similar in both strains at 8 and 96 weeks. Shaker stress evoked responses similar to defense reactions in both strains. The incremental responses in mean arterial pressure, heart rate, cardiac index, and cerebral, skeletal muscle, and myocardial flow and the decremental responses in splanchnic, renal, and skin flow were greater in SHR than in WKY, particularly at 8 weeks. Most of these responses tended to or did decline between 8 and 96 weeks in both strains. The plasma catecholamine responses were also greater in SHR at 8 and 96 weeks, and they did not differ in either strain between these ages. Thus, circulatory and sympathoadrenal reactivity to acute stress were enhanced in SHR compared with WKY, independently of age.(ABSTRACT TRUNCATED AT 250 WORDS)
Evidence that prostacyclin mediates the vascular action of magnesium in humans.
Authors: Nadler J L , Goodson S , Rude R K
Published: June 2012

Evidence in vitro and in humans suggest that Mg2+ can alter systemic and renal vascular tone. However, the mechanism of these effects is not known. The role of vasodilator prostaglandin release and Ca2+ flux in Mg2+-induced changes in blood pressure and renal blood flow was studied in 10 normal subjects maintained on a fixed 80-mEq Na+ and K+ diet. Magnesium sulfate infused at 200 mg/hr for 3 hours reduced systolic and diastolic blood pressure within 1 hour (from 119 +/- 2 [SEM] to 109 +/- 4 mm Hg systolic; from 74 +/- 3 to 64 +/- 4 mm Hg diastolic; p less than 0.02). This hypotensive response was seen in all subjects and persisted for 3 hours. The pulse rate did not change, but renal blood flow (p-aminohippurate clearance) increased (from 902 +/- 78 to 1108 +/- 130 ml/min/1.73 m2; p less than 0.05). The Mg2+ infusion produced a significant increase in the excretion of the stable prostaglandin I2 (PGI2) metabolite 6-keto-PGF1 alpha (from 96 +/- 12 to 154 +/- 16 ng/g creatinine; p less than 0.01). In contrast, urinary PGE2 was not altered (328 +/- 75 vs 399 +/- 145 ng/g creatinine; p greater than 0.6). To evaluate the functional role of PGI2 release, the cyclooxygenase inhibitors indomethacin (75 mg) or ibuprofen (600 mg) were given before the Mg2+ infusion. Both cyclooxygenase blockers, given in doses that inhibited immunoreactive 6-keto-PGF1 alpha release, completely prevented the Mg2+-induced decline in blood pressure and increased renal blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)
Exaggerated renal vasodilator response to calcium entry blockade in first-degree relatives of essential hypertensive subjects.
Authors: Blackshear J L , Garnic D , Williams G H , Harrington D P , Hollenberg N K
Published: June 2012

Because an inherited renal factor may contribute to essential hypertension in humans, the study of family members is attractive. To assess the determinants of renal vascular tone, graded doses of either diltiazem (10-1000 micrograms/min) or acetylcholine (1-100 micrograms/min) were infused into the renal artery in 52 normotensive subjects, 16 with and 36 without a family history of hypertension when they were in balance on either a 10-mEq or 200-mEq sodium intake. Renal blood flow was measured with 133Xe. Restricted sodium intake potentiated renal vascular responses to diltiazem (p less than 0.01), suggesting a role for angiotensin as a determinant. In four subjects with no family history of hypertension on a 200-mEq sodium intake, angiotensin II in subpressor doses (1 ng/kg/min i.v.) induced renal vasoconstriction and enhanced the renal vasodilator action of diltiazem (p less than 0.001). In subjects with a family history of hypertension, the renal vascular response to diltiazem was enhanced (p less than 0.01) despite similar values of plasma renin activity, angiotensin II concentration, and sodium excretion. Because responses to acetylcholine were modified neither by sodium intake nor by family history, specificity for diltiazem was suggested. The intriguing possibility is raised that the enhanced renal vascular response to diltiazem reflects an abnormality in the control of renal vascular tone in the offspring of essential hypertensive subjects.
Atrial natriuretic factor inhibits central angiotensin II pressor responses.
Authors: Casto R , Hilbig J , Schroeder G , Stock G
Published: June 2012

Intracerebroventricular (i.c.v.) administration of human atrial natriuretic factor (ANF), fragment 1-25, in the dose range 3 to 20 micrograms/kg did not alter resting arterial pressure or heart rate in rats anesthetized with chloralose/urethan (60:600 mg/kg i.p.), while angiotensin II (ANG II), 1 microgram/kg, produced a significant increase in arterial pressure after i.c.v. application. This pressor effect induced by ANG II was abolished by simultaneous administration of ANF (3 micrograms/kg i.c.v.). In isolated strips of rabbit aorta preconstricted with ANG II (10 nM), ANF caused a dose-dependent relaxation. In intact rats, the increase in blood pressure following intravenously administered ANG II (0.1 and 1 microgram/kg) was not altered by the highest dose of ANF (20 micrograms/kg) given intracerebroventricularly. These results suggest that atrial peptides may play an important role in the regulation of blood pressure by interacting with both the central and peripheral actions of ANG II. Inhibition of the central pressor action of angiotensin by ANF appears to be independent of any direct peripheral effect of the atrial peptides.
Possible association of MN locus haplotypes with essential hypertension.
Authors: Heise E R , Moore M A , Reid Q B , Goodman H O
Published: June 2012

Five multigenerational kindreds with familial hypertension were typed for human leukocyte antigen (HLA) and blood group antigens to investigate genetic factors that influence variability in blood pressure. Pedigree analysis revealed that children of matings in which both parents were hypertensive had a significantly greater risk of hypertension than children of matings in which one parent or neither parent was hypertensive. Blood types N and MN were abnormally distributed among hypertensive as compared with normotensive members of white but not black families. The distribution of ABO and Rh types was not significantly different between hypertensive and normotensive siblings. When all possible pairings of siblings were examined for HLA haplotype sharing, abnormal distributions were observed among hypertensive sib pairs whereas the expected mendelian segregation was observed among hypertensive-normotensive sib pairs and normotensive-normotensive sib pairs. These results suggest the genetic factors controlling variation in blood pressure may include loci in the region of the MN locus on chromosome 4 and, possibly, the major histocompatibility complex on chromosome 6.
Fundamental Difference in the Reactivity of the Blood Vessels in Skin Compared with those in Muscle
Authors: LANIER JOHN T. , GREEN HAROLD D. , HARDAWAY JOHN , JOHNSON HOOPER D. , DONALD WILLIAM B.
Published: June 2012

Blood flow was measured with the electromagnetic flowmeter in the saphenous artery bed (cutaneous) and in the distal femoral and popliteal beds (muscle). The effects of ischemia and of intra-arterial injection with methacholine, l-epinephrine and l-norepinephrine were studied before and again after each injection of progressively increased doses of antiadrenergic drugs. These studies indicate a fundamental difference between the reactivity of cutaneous and muscular vascular beds.
Further Experimental Evidence that Pulmonary Capillary Pressures Do Not Reflect Cyclic Changes in Left Atrial Pressure (Mitral Lesions and Pulmonary Embolism)
Authors: ANKENEY JAY L.
Published: June 2012

Wedged catheter pressures (PC) were compared with those in the aorta, left atrium, and pulmonary artery before and after production of mitral stenosis, insufficiency, and pulmonary embolism. In general it was found that "PC" pressures follow closely changes in left atrial pressures even when pulmonary artery pressure changes in an opposite direction (for example, pulmonary embolism). However, properly recorded "PC" pressure pulses did not display the large cyclic pressure variations recorded from the left atrium during mitral stenosis and insufficiency. It is concluded that pressures recorded through a properly wedged catheter represent the constant pulmonary capillary pressure but do not reflect cyclic pressure variations in the left atrium.
Nucleotide Metabolism in Cardiac Activity
Authors: KHAIRALLAH PHILIP A. , MOMMAERTS W. F. H. M.
Published: June 2012

The application of ion-exchange chromatography for the determination of adenosine nucleotides in mammalian hearts is described. It is found that 1 gram ventricular muscle contains nearly 5 x 10
-6
mole of adenine nucleotides, presumably present as ATP in the relaxed heart in vivo. After isolation of the heart, breakdown of ATP takes place especially under anaerobic conditions, and the reaction products AMP and IMP diffuse into the medium. Effects upon these reactions of glucose, glutamic acid and excess potassium are suggested by preliminary experiments.
Prevention of Coronary Atherosclerosis by Estrogen-Androgen Administration in the Cholesterol-Fed Chick
Authors: STAMLER JEREMIAH , PICK RUTH , KATZ LOUIS N.
Published: June 2012

Estrogens are highly effective both prophylactically and therapeutically against cholesterol-induced coronary atherogenesis in cockerels. The relative immunity of premenopausal women to coronary sclerosis may be related to the presence of these ovarian hormones. Therefore, estrogens may be useful in the treatment of human coronary atherosclerosis. With this object in mind, the elimination of the feminizing effects of estrogens would be highly desirable. The present experiments prove that concomitant exhibition of androgens and estrogens maintain masculine sex characteristics without interfering with the beneficent effect of estrogens on the coronary arteries in cockerels.
The Dynamics of Both Right and Left Ventricles at Rest and During Exercise in Patients with Heart Failure
Authors: LEWIS BENJAMIN M. , HOUSSAY HECTOR E. , HAYNES FLORENCE W. , DEXTER LEWIS
Published: June 2012

Right auricular pressure, pulmonary "capillary" pressure (a measure of left auricular pressure) and cardiac output were measured at rest and during exercise in 14 patients with cardiovascular disease affecting primarily the left ventricle. In five patients these measurements were normal at rest, in nine abnormal. In all physiologic abnormalities developed on exercise in the sequence: increased pulmonary "capillary" pressure, increased right auricular pressure, decreased cardiac output. Definite abnormalities of left ventricular function were demonstrable when right ventricular function was entirely normal. These results are discussed in relation to the clinical status of the patients.
Further Evidence that the Pulmonary Capillary Venous Pressure Pulse in Man Reflects Cyclic Pressure Changes in the Left Atrium
Authors: WERKÖ LARS , VARNAUSKAS E. , ELIASCH H. , LAGERLÖF H. , SENNING A. , THOMASSON B.
Published: June 2012

In four cases of atrial septal defect and in one case of mitral stenosis, the pressure pulse was recorded in the left atrium, in the first four cases through catheters, and in the fifth through a needle introduced through the chest wall. The pressure pulse was compared with pulmonary capillary pressure recorded simultaneously or nearly so. Good agreement was found both in shape and height of the two pressure pulses.
The Influence of the Pulmonary Arterial Pressure on the Pulmonary Capillary Venous Pressure in Man
Authors: WERKÖ LARS , VARNAUSKAS E. , ELIASCH H. , THOMASSON B.
Published: June 2012

In two cases with a well-defined pulmonary capillary venous pressure pulse, the lobular pulmonary artery was occluded with a balloon while the pulmonary capillary venous pressure was registered. There was no change in the tracing obtained. In two other cases positive pressure respiration almost completely damped out the pulmonary capillary venous pressure variations, but the mean pressure remained virtually unchanged. It is concluded that the pulmonary arterial pulse wave usually does not cause artefacts in the pulmonary capillary venous tracing. Cyclic changes in pulmonary capillary venous pressure cannot be studied while the subject is on positive pressure respiration.
The Production of Experimental Congestive Heart Failure in Rabbits
Authors: ALEXANDER NATALIE , EDMONDSON HUGH A. , DRURY DOUGLAS R.
Published: June 2012

Observations were made on blood pressure, heart size, and physiologic state of 33 rabbits subjected to severe constriction of the abdominal aorta. Two-thirds of the rabbits developed symptoms of congestive heart failure and died within two weeks. Autopsy findings revealed acute passive congestion of liver and lungs in the majority of cases and chronic passive congestion of liver and heart failure cells in lungs in some animals which survived a month or more. Advantages of this method are simplicity of operative procedure and high incidence of heart failure.
Myocardial Carbohydrate Metabolism in Normal Dogs, with Effects of Hyperglycemia and Starvation
Authors: GOODALE WALTER T. , HACKEL DONALD B.
Published: June 2012

Myocardial metabolism of Nembutalized normal intact dogs was studied with the aid of the coronary sinus catheterization technic. Oxygen, glucose, lactate and pyruvate were extracted by the heart in direct relation to the arterial level of each substance, independently of the others. Pyruvate and lactate showed a high myocarcdial extraction coefficient, but the normal low arterial levels at rest prevented them from together accounting for more than 50 per cent of the total myocardial energy requirements. Glucose was not utilized below a mean threshold of 54 mg. per cent, but with normal arterial levels of 70 to 120 mg. per cent, glucose extraction was sufficient to provide the major potential source of fuel for myocardial oxidative energy. During starvation, the heart probably derived its energy from fat, as indicated by a myocardial respiratory quotient near 0.70, and a low myocardial carbohydrate extraction.
Aortic Arteriosclerosis in the Dog After Localized Aortic X-lrradiation
Authors: Lindsay Stuart , Kohn Henry I. , Dakin Richard L. , Jew Jack
Published: June 2012

Localized segments of the abdominal aortas of 18 dogs were irradiated with 50-kv. x-rays in doses ranging from 1,500 to 5,500 r (at the ventral surface of the aorta), and were examined histologically at intervals ranging from 2 to 48 weeks after irradiation. Arteriosclerosis developed at the irradiated sites and was significantly more severe than that which occurred in nonirradiated control sites in the abdominal aorta. There was evidence that severity of arteriosclerosis increased with time following irradiation of the aorta. There was less pronounced arteriosclerosis after 3,000 to 5,500 r than after 1,500 to 2,500 r. It appeared that the larger doses of x-rays inhibited the full development of the late lesions, although presumably causing more initial primary damage. X-irradiation appeared to be followed by the development of arteriosclerotic lesions similar to those that occur naturally in old dogs. It is proposed that irradiation may selectively cause injury of the internal elastic membrane, and that this degenerative phenomenon is followed by the development of intimal fibrosis and plaque formation.
Effects of Bradykinin on the Systemic and Coronary Vascular Bed of the Intact Dog
Authors: MAXWELL G. M. , ELLIOTT R. B. , KNEEBONE G. M.
Published: June 2012

Bradykinin, in the circumstances of this study, increased heart rate, cardiac output, and coronary blood flow. Systemic, pulmonary, and coronary vascular resistances decreased; these changes were not entirely due to the decrease in systemic and pulmonary arterial pressures. The changes in myocardial oxygen and carbon dioxide metabolism were mostly related to the increase in coronary blood flow. Bradykinin was found to be associated with a decrease in cardiac efficiency.
Antithrombotic Effect of Monamine Oxidase Inhibitor (Nialamide)
Authors: Shimamoto Takio , Ishioka Tadao , Fujita Tsutomu
Published: June 2012

A new type of antithrombotic substance, nialamide, was compared with phenindione and warfarin in its preventive effect against experimental thrombosis produced in rabbits. One hundred fifty-seven rabbits were subjected to quantitative traumatization of the endothelial surface of the retroauricular artery and marginal vein of the ear. Pretreatment of animals with 3 to 5 mg./Kg. of nialamide, which did not prolong the one-stage prothrombin time, was much more effective in preventing thrombosis than either phenindione or warfarin, both of which prolonged the prothrombin time markedly. Even in the animals pretreated by 600 to 900 mg. of phenindione, which reduced the prothrombin activity to less than 6 per cent, the preventive effect of phenindione is significantly less than the antithrombotic effect of 3 to 5 mg./Kg. of nialamide. Pretreatment of animals with 1.5 mg./Kg. of nialamide was found to be ineffective. However, the concomitant application of subeffective doses of both phenindione, 150 mg., and nialamide, 1.5 mg., was found to be effective. On the other hand, the addition of phenindione, even in doses as large as 300 to 900 mg., to an effective dose of nialamide, 3 to 5 mg./Kg., did not further enhance the antithrombotic effect of nialamide. The antithrombotic effect of nialamide was not shown to be significantly modified by sympathectomy or by denervation of the blood vessels tested. Nialamide was found to prevent the aggregation of platelets on the injured endothelial surface.
Intercoronary Reflex
Authors: Guzman Santiago V. , Swenson Edward , Jones Malcolm
Published: June 2012

The effect of coronary embolization on the coronary vascular bed was studied in the intact anesthetized dog utilizing the technique of coronary artery catheterization without opening the thorax. Two coronary arterial catheters were inserted via the carotids, one into the anterior descending branch and the other into the circumflex branch of the left coronary artery. Coronary vascular visualization was accomplished by routine roentgenography and by cinefluorography (using an image intensifier and 16- and 35-mm. motion picture film at 48 to 60 frames/sec.) of the heart after injection of a radiopaque dye into a coronary vessel. The results following coronary embolization showed that in both the embolized and nonembolized coronary vessels there was: (1) marked decrease in the size of the coronary vascular bed, (2) reflux of the injected contrast substance into the other coronary artery or into the aorta, (3) considerable delay in the disappearance time of the injected radiopaque material. Under the conditions of our experiments, these results can be interpreted as evidence of a generalized left coronary vasoconstriction following embolization of a branch of the left coronary artery. This was prevented to a great extent by the prior injection of atropine.
Cerebral Circulatory Effects of Acutely Induced Hypervolemia in Human Subjects
Authors: Eisenberg Seymour
Published: June 2012

Expansion of the blood volume with 5 per cent albumin solution was associated with a 32 per cent increase in cerebral blood flow and a commensurate decrease in cerebral vascular resistance. Expansion of the intravascular volume with whole blood was not associated with any consistent cerebral hemodynamic alteration. It is suggested that the response of the cerebral circulation was largely governed by the factitious "anemia" induced by the selective expansion of the plasma volume.
Experimental Dissection of Media of Aorta by Pressure
Authors: Hirst Albert E. , Johns Varner J.
Published: June 2012

The pressure required to produce intramural dissection was determined by injection of water into the media of strips of aorta obtained at postmortem examination. The mean pressure required reached a maximum in the second and third decades and decreased gradually thereafter. No differences in the pressure required was noted when comparisons were made by race, sex, different segments of the aorta, different strata of the media, or in the region of atherosclerotic lesions. Pregnancy (postpartum state) did not decrease the resistance in two instances. A slight increase in the pressure required was observed in the aortas of patients with hypertensive disease, and a marked increase was encountered in the presence of syphilitic aortitis. The resistance of the aorta in spontaneously occurring dissecting aneurysm was variable; one case had a normal resistance while the other was impaired.

The authors postulate that a solitary focus of medial degeneration strategically located is an adequate stimulus for dissection. Subsequently, rupture of vasa vasorum into this weakened area results in a rapidly expanding bleb. The pressure required to produce further enlargement of the bleb will vary inversely with its diameter, thus tending to extend the dissection. This mechanism may explain the frequent finding of an histologically normal aorta in random sections from cases with extensive intramural dissection.
Contour of Electrically Induced Premature Ventricular Beats Before and After Experimental Myocardial Infarction in Dog
Authors: Paine Emmons G. , McDonough Michael , Soloff Louis A.
Published: June 2012

Ventricular premature beats were produced by stimulating electrodes inserted into the anterolateral right ventricular and into the midlateral left ventricular wall of 13 openchest anesthetized dogs. In 9 of the 13, acute myocardial infarction deformed the final deflection of the experimentally induced ventricular extrasystoles so that they mimicked the diagnostic pattern present in the beats of sinus origin. In 4 of the 13, no changes occurred in either the extrasystoles or in the beats of sinus origin until the infarcted region was brought into contact with the thoracic wall, at which time diagnostic patterns of infarction appeared in both types of ventricular complexes. Reinfarction produced by ligating an additional coronary branch produced comparable changes in the final deflection of the premature and sinus-propagated beat. These findings suggest that the inscription of the terminal deflections of premature ventricular beats is dominated by events within the infarcted region. They support the clinical concept that the configuration of ventricular extrasystoles may be of value in the recognition of acute myocardial infarction. The findings do not explain, however, the occasional absence of diagnostic findings in ventricular premature beats in electrocardiograms otherwise diagnostic of human myocardial infarction.
Chronic Experimental Hypertension in Dogs after Constriction of Brachiocephalic and Left Subclavian Arteries
Authors: Hawthorne Edward W. , Mandal A. K.
Published: June 2012

In summary, the studies suggest that:

(1) Simultaneous and controlled constriction of the brachiocephalic and left subclavian arteries resulted in chronic femoral hypertension in seven dogs.

(2) This hypertension is associated heniodynamically with an increase in cardiac index due mainly to an increased stroke volume.

(3) The suggestion is made that the initiating mechanism for this type of experimental hypertension is a chronic decrease in endosinal pulse pressure.
Relationship of Pulmonary Artery-Wedge Pressure to Left Atrial Pressure in Man
Authors: Luchsinger Peter C. , Seipp Harry W. , Patel Dali J.
Published: June 2012

The pulmonary artery-wedge and left atrial pressures were recorded simultaneously in 11 patients during a control state, during norepinephrine infusion, as well as during positive and negative intra-alveolar pressures. A good correlation (r = 0.95) found between the two pressures permits the use of corrected pulmonary artery-wedge pressure in calculation of pulmonary vascular resistance under control and test conditions.
Adjustment of Reflex Bradycardia to Elevated Arterial Pressure in Conscious Rabbits
Authors: Alexander Natalie , De Cuir Marjorie
Published: June 2012

Angiotensin was infused into intact, conscious rabbits to produce a continuous, moderate elevation of arterial pressure. The reflex cardiac rate response was studied. Within two hours of initial drop in heart rate, average time 37 minutes for 13 rabbits, the heart rate began to rise. The rates of rise were between 1.2 and 6.0 per cent of the initial drop per minute. Thus, in the presence of elevated arterial pressure, the cardiac reflex mechanism can adjust so that heart rate reaches control values within an average time of one hour in most animals. One additional animal showed no tendency for adjustment in over seven hours of infusion. The time between start of heart rate rise and restoration of 50 per cent of the initial drop was directly related to the sensitivity of the initial reflex response, i.e., heart rate drop per mm. Hg increase in diastolic pressure. Most of the animals developed a postinfusion tachycardia which was directly related to the amount of increase in heart rate attained by the end of the infusion. We conclude that in the presence of continuously elevated arterial pressure, the reflex cardiac slowing mechanism can adjust within a relatively short time, and the evidence that this represents a resetting of the mechanism within the central nervous system is discussed.
Bradykinin-Induced Increase in Total and Effective Blood Flow in Skeletal Muscle
Authors: Paldino Rita L. , Hyman Chester , Lenthall Jim
Published: June 2012

The effect of the synthetic peptide, bradykinin, on total and nutritional blood flow through mammalian skeletal muscle in anesthetized rats, cats, and rabbits was studied. The intra-arterial administration of the drug consistently and significantly increases total blood flow through the gastrocuemius muscle of chloralose-anesthetized cats and rabbits. A similar increase in clearance of the dye "Water Blue" from microinjection sites in the spino-trapezius muscle of the rat and clearance of iodide ions from skeletal muscle in the larger species was established. Bradykinin causes active dilatation of the nutritional circulation as well as increased total blood flow through muscle.
Comparison of Effectiveness of Autologous and Nonautologous Plasma in Oligemic Shock in Dogs
Authors: Elias George L. , Gurd Fraser N. , Hampson Lawrence G. , Burgen Arnold S. V.
Published: June 2012

A comparison has been made between the effectiveness of nonautologous and autologous plasma as a plasma volume expander in dogs made severely oligemic by acute hemorrhage. No difference was found in their effectiveness in expanding plasma volume or in raising blood pressure. It is suggested that the reactions seen in normal dogs are suppressed in oligemic dogs by catecholamines liberated in response to hypotension.
Pressure-Radius Relationship in Large Blood Vessels of Man
Authors: Luchsinger Peter C. , Sachs Murray , Patel Dali J.
Published: June 2012

The radius of the pulmonary arteries and of the descending thoracic aorta in man was measured by angiographic techniques. Simultaneously with angiocardiography, pressure measurements were carried out, permitting calculation of radius-pressure (ΔR/ΔP) relationships. The results obtained by this method are similar to those obtained by other methods in which the vessel radius was measured more directly.
Electrocardiogram, Myocardial Oxygen and Contraction in Scar and Collaterally Supplied Muscle After Experimental Coronary Ligation
Authors: Sayen John J. , Sheldon Warner F. , Peirce George , Katcher Aaron H. , Kuo Peter T.
Published: June 2012

Studies of myocardial electrocardiograms, oxygen, and cinematographic muscle contraction were carried out in dogs during coronary branch ligation and after 2 to 12 weeks' recovery. Scars were found in 12 of 13 animals. Five were transmural at some point and seven entirely subendocardial. Myocardial electrocardiographic abnormalities were found in every animal with a scar. Epicardial electrocardiographic abnormalities (localized Q waves or low R waves) were roughly conterminous with the surface projection of the entire extent of all transmural scars and of six out of seven subendocardial scars. Precordial leads were abnormal in only three animals, all with transmural scars. Responses to oxygen inhalation, hypoxia, and levarterenol for these animals were within the range of normal variation, but there was a tendency to develop ventricular fibrillation, unrelated to the amount of scar. Study of the acute ischemic dysfunction consequent to coronary ligation is not of great value for the interpretation of the situation at re-exploration two or more weeks later. The behavior of recovered collaterally supplied muscle, assessable by the techniques employed in these studies (provided that epicardial thickening has been avoided by minimizing exposure and trauma at the time of ligation), has relevance to many human coronary disease situations in which regional circulation is carried on by intramyocardial or small caliber vessels.
Phasic and Mean Blood Flow in the Canine Septal Artery and an Estimate of Systolic Resistance in Deep Myocardial Vessels
Authors: ECKSTEIN RICHARD W. , MOIR THOMAS W. , DRISCOL THOMAS E.
Published: June 2012

Phasic flow in the canine septal artery was recorded with an orifice meter supplied by pulsatile aortic pressure. Flow patterns were recorded when right ventricular pressure was normal and contrasted with those following elevation of right ventricular pressure in order to minimize the dynamic effect of the superficial component of the artery. Results indicate that elevation of right ventricular pressure increases the early systolic backflow, largely prevents mid-systolic forward flow, and accentuates early diastolic flow. It is suggested that this pattern does not represent that in arterioles in deep layers of the myocardium.

In other experiments the septal artery was perfused through an orifice meter at variable pressures to determine the pressure required to negate mid-systolic flow at high right ventricular pressures. The results indicate that pressures considerably above aortic or right ventricular systolic pressures are required to generate forward mid-systolic septal flow.

The mean septal flow was quantitated in terms of total common left inflow. It was found that an average of 16.0% of common left flow enters the septal artery. The significance of this has been discussed in terms of its relationship to the venous drainage of common left coronary arterial inflow.
Study of the Relationship Between the Neurotransmitter Store and Adrenergic Nerve Block Induced by Reserpine and Guanethidine
Authors: GAFFNEY THOMAS E. , CHIDSEY CHARLES A. , BRAUNWALD EUGENE
Published: June 2012

The heart rate response to cardioaccelerator nerve stimulation and the corresponding levels of myocardial norepinephrine content were determined and correlated in dogs at various time intervals following the intravenous injection of either 3 mg/kg reserpine, or 10 mg/kg guanethidine. Guanethidine produced complete blockade of the cardiac accelerator response before producing measurable myocardial depletion of norepinephrine. In contrast, reserpine reduced the positive chronotropic response to cardioaccelerator nerve stimulation only after myocardial norepinephrine levels have been reduced to approximately 0.3 µg/g. An infusion of norepinephrine did not restore the heart rate response to cardioaccelerator nerve stimulation in either the reserpine or guanethidine treated dogs. These data suggest that the interference with adrenergic transmission produced by guanethidine is independent of changes in the level of stored adrenergic transmitter. The reserpine-induced blockade of adrenergic transmission may ultimately be dependent upon the mission may ultimately be dependent upon the depletion of adrenergic transmitter, but almost complete depletion of stored adrenergic transmitter must occur before reserpine-induced adrenergic blockade occurs.
Effects of Low Oxygen and of Carbon Monoxide on the Renal Circulation in Unanesthetized Rabbits
Authors: KORNER PAUL I. , Yvonne Pascoe
Published: June 2012

The effects of breathing 9.6% O
2
in N
2
and of breathing 0.1% to 0.2% CO in air on the renal blood flow (RBF), glomerular filtration rate (GFR) and renal PAH extraction ratio were studied in the unanesthetized rabbit in relation to changes in cardiac output, heart rate, blood pressure and ventilation. All experiments were carried out during moderate water and mannitol diuresis. The RBF and GFR were reduced in both types of hypoxia but this effect was produced by different mechanisms. With low O
2
mixtures reduction in RBF and GFR occurred mainly as a result of nervous vasoconstriction acting on the afferent arteriole. The arterial chemoreceptors played a part in the production of vasoconstriction. With carbon monoxide, reduction in RBF and GFR occurred mainly as a result of passive reduction in blood pressure, and only slight transient nervous vasoconstriction could be demonstrated in the early period of exposure to this gas. The results suggest that differences in arterial oxygen pressure (Pa

o
o2

) were of major importance in accounting for the differences in renal circulatory effects of low O
2
mixtures and CO in the rabbit.
Dimensions of Blood Vessels from Distributing Artery to Collecting Vein
Authors: WIEDEMAN MARY P.
Published: June 2012

Measurements of lengths, diameters, and numbers of post-capillary vessels were made in the bat's wing. The cross-sectional area and capacity in the various portions of the vascular bed were calculated.

The greatest total cross-sectional area in the entire vascular bed was found in the venules, a result not in agreement with similar reports made by others using measurements from vessels in fixed preparations. This discrepancy probably results from disagreement regarding the diameter of capillary vessels.

Calculations to determine the per cent of total volume in each portion of the vascular bed showed that the venous system accounts for as much as 80% of the total vascular volume.
Hemodynamic Correlates of the Various Components of the First Heart Sound
Authors: SHAH P. M. , MORI M. , MACCANON D. M. , LUISADA A. A.
Published: June 2012

Previous studies in this laboratory having demonstrated that AV valve closure is not directly responsible for the rapid vibrations of the first heart sound, the mechanism of production of this "sound" was studied further in 30 experiments in dogs. The experiments were performed with multiple pressure catheterization, and intracardiac phonocatheterization, and were compared with external phonocardiograms and electrocardiograms. In 10 experiments, the first derivatives of the left and right ventricular pressures were also recorded. In four experiments, direct epicardial and arterial sound tracings were obtained.

These experiments revealed that three groups of vibrations, or components, were often visible in the external phonocardiogram, and in intracardiac and epicardial tracings. The first component follows the onset of left ventricular pressure rise and closure of the mitral valve but coincides with the rapid rise of the first derivative of LV pressure. The second component has no relationship with right heart events, occurs before aortic valve opening, and coincides with the sudden change of course of the first derivative of LV pressure. The third component occurs slightly after aortic valve opening, and seems related to sudden increase of aortic wall tension. It is probably the physiological equivalent of the aortic "ejection sound." Thus, the first two components are both left ventricular in origin while the third is of aortic origin.
Theory of Use of Indicators to Measure Blood Flow and Extracellular Volume and Calculation of Transcapillary Movement of Tracers
Authors: ZIERLER KENNETH L.
Published: June 2012

For indicators or tracers injected into the vascular system and sampled at some other portion of the vascular system, the indicator dilution curve supplies a measure of blood or plasma flow through the system even if the indicator is not confined to the blood vessels, providing only that it eventually all return to the circulation prior to the sampling site.

Mean transit time of the indicator through the system multiplied by the measured flow determines the volume through which the indicator is distributed. This volume is independent of capillary permeability to the indicator if the indicator enters interstitial fluid at all.

Of indicator coursing through the vascular system, the fraction crossing capillaries into interstitial fluid is inversely proportional to the mean transit time of the indicator across capillaries, through interstitial fluid and back into capillaries. The constant of proportionality is the ratio of interstitial fluid volume to plasma flow through the system.

The fraction of a substance crossing capillary walls and returning can be calculated if the frequency function of transit times into, through and out of interstitial fluid can be measured. The equations cannot be solved if this frequency function is not measured.

However, because this frequency function falls to zero much more slowly than other frequency functions through which tracer concentration is apt to be convoluted, capilary permeability may be estimated graphically. The graphic estimate applies even to substances that do not return completely to the vascular bed.
Renal Pressor System and Neurogenic Control of Arterial Pressure
Authors: MCCUBBIN JAMES W. , PAGE IRVINE H.
Published: June 2012

Angiotensin has an effect on the sympathetic nervous system which results in an enhanced response to agents and procedures that cause release of endogenous norepinephrine while having little or no effect on response to exogenous norepinephrine. The effect is peripheral, it does not appear to involve sensitization of norepinephrine receptors, it is dependent upon a functionally intact sympathetic nervous system, and it appears unrelated to the direct vasoconstrictor action of angiotensin. The response to tyramine is increased in both acute and chronic renal hypertension; this suggests that only very small amounts of angiotensin, difficult to detect by present assay methods, continue to have an effect on the sympathetic nervous system in chronic renal hypertension. By intensifying the effect of normal neurogenic vasomotor activity, this action of angiotensin, along with the upward shift of threshold and range of response of the carotid sinus buffer mechanism, might account to a major degree for the large neurogenic component of chronic renal hypertension.
Isometric Time-Tension Relationships as an Index of Myocardial Contractility
Authors: SIEGEL JOHN H. , SONNENBLICK EDMUND H.
Published: June 2012

The mechanics of isometric contraction in the heart were studied in both isolated papillary muscle and in an innervated, isovolumetric heart in situ. The maximum rate of development of isometric tension (dp/dt) and the integrated isometric tension (IIT), were studied on a beat-to-beat basis. The results indicate: 1) At a given heart rate, both the IIT as well as dp/dt vary directionally as changes in end diastolic volume and fiber length. During isometric contraction, the ratio dp/dt/IIT is independent of changes in fiber length, and remains a constant for any given state of contractility. 2) At a constant heart rate, and at constant volume, cardiac sympathetic nerve stimulation markedly increases dp/dt and IIT. The ratio dp/dt/IIT is elevated to a new constant which is also independent of fiber length. 3) Increasing heart rate increases the ratio dp/dt/IIT. This increase is, however, small compared to the increase in this ratio produced by sympathetic stimulation at the same rate. 4) The effects of heart rate and sympathetic stimulation are additive. 5) Differences have been noted between the manner in which norepinephrine, calcium, and acetyl strophanthidin alter the mechanics of the isovolumetric ventricle. This evaluation of the myocardial contraction is also uninfluenced by the adequacy of ventricular relaxation. 6) Comparison of the isovolumetric ventricle with isolated papillary muscle yielded directly analogous results, indicating that the properties observed were intrinsic to cardiac muscle and are not dependent upon structural arrangements in the intact heart. It is suggested that this ratio dp/dt/IIT is a quantitative measure of the contractility of the myocardium.