摘要:

Elastic symmetry was studied in the middle descending thoracic aorta, abdominal aorta, and left common carotid artery under physiologic ranges of loading in ten dogs. A segment of the blood vessel was isolated and hung vertically. As the segment was pressurized, the radius, length, and the rotation of the lower end of the vessel were measured with respect to the fixed upper end. In addition, the angular displacement of a glass whisker initially placed perpendicularly through the wall was measured. From these data it was possible to calculate the values of shearing strains and elongating strains associated with pressurization and various imposed longitudinal stresses. The values of shearing strain varied from 0.003 to 0.115 over pressure ranges of 3 to 270 cm H2O. In all instances the values of shearing strain were much smaller than the corresponding elongating strains. It was concluded that the vessel has elastic properties that are nearly symmetrical about the planes perpendicular to principal stresses under physiologic loading, i.e., the vessel may be treated as a cylindrically orthotropic tube.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Cardiac hypertrophy was produced in rats by banding the ascending aorta. Increases in heart weight and RNA content occurred within 48 hours, indicating that hypertrophy develops rapidly. The total RNA content and the specific radioactivity of RNA labeled with3H-uridine were determined. The rate of RNA synthesis was estimated from these data and from the specific radioactivity of the myocardial uridine nucleotide pool. The rate of RNA synthesis in hearts of banded animals averaged four times greater than controls on the second postoperative day and about two to three times greater on the fourth to fifth postoperative days. An expansion of the myocardial uridine nucleotide pool was observed in banded rats, but the size of the myocardial adenosine nucleotide pool was not changed. No changesin base composition of 28S, 18S, or 4S RNA were observed following cardiac hypertrophy.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Transmembrane action potentials were recorded from embryonic rat hearts at ages between 10½ days of gestation and birth (21 to 22 days). The resting potential averaged 30 to 40 mv at 10½ days and increased to around 80 mv by birth. Two periods of rapid increase in resting potential were noted: 1) from 10½ to 13½ days and 2) from 19½ days of gestation to birth. The maximal upstroke velocity of the action potential increased as the resting potential increased. The duration of the ventricular and atrial action potentials was inversely related to heart rate, and their rate sensitivity decreased with age. The atrial action potential lost its rate sensitivity by 13½ days of gestation and the ventricular action potential lost its by birth. At 10½ days diastolic depolarization was found in the area of the ventricle proximate to the A-V junction, the left and right atria, and the sinus venosus. The velocity of the diastolic depolarization was greatestin the sinus venosus and least in the ventricle. The diastolic depolarization decreased with growth and was lost by 13½ days of gestation.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Radiotelemetry was used to study regional blood flow distribution in Alaska sled dogs during cross-country runs. Doppler ultrasonic flowmeter transducers were chronically implanted on the coronary, renal, and mesenteric arteries, terminal abdominal aorta, and ascending aorta or pulmonary artery, and a miniature blood pressure gauge was installed in the aorta or carotid artery. Flow and pressure data telemetered from dogs running on the trail were received and recorded remotely. The heart rate, 40 to 60/min in sleeping dogs, increased to 80 to 100/min when the dogs were ambulatory and to 100 to 150/min when the dogs were excited before a race. Heart rate accelerated to 300/min at the start of exercise and commonly remained at that level throughout prolonged runs. Aortic blood pressure averaged 130/90 mm Hg at rest, but the systolic pressure often exceeded 300 mm Hg when the dogs were running. A transient drop in mean pressure occurred at the onset of running, but mean pressure during sustained exercise was practically identical to that at rest. Flow in the terminal aorta increased 9 to 12 times and coronary flow 5 to 6 times, but mesenteric and renal flows were unchanged during violent, prolonged exercise. These findings contrast with diminished visceral flows recorded in exercising humans and suggest that compensatory redistribution of flow is not a significant reserve mechanism in these animals during exercise.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

The ionic basis of ventricular arrhythmias induced by a cardiac glycoside was studied in pentobarbital-anesthetized dogs. The effects of ouabain alone and in combination with hypothermia or pronethalol on myocardial and plasma Na+and K+were determined. Hypothermia (26°C) and pronethalol (15 mg/kg, iv) had similar effects on the standard lead II of the EGG, i.e., a decrease in heart rate and increases in P-R, QRS, and Q-T intervals. In the absence of ouabain, hypothermia and pronethalol each produced small and inconsistent changes in intracellular Na+and K+concentrations. Both hypothermia and pronethalol were found to significantly increase the threshold toxic dose of ouabain required to produce a ventricular arrhythmia within the test period of 90 minutes. Both pronethalol and hypothermia effectively prevented ouabaininduced changes in myocardial Na+and K+when arrhythmias were prevented. When sufficient ouabain was given to produce an arrhythmia, there was always a significant fall inmyocardial K+. In unprotected and in hypothermic animals, these arrhythmias were also associated with a significant increase in left ventricular Na+. The effect of ouabain on Na+was not significant in pronethalol-treated dogs.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Eight patients with acute respiratory failure secondary to chronic bronchitis were studied for up to 5 consecutive days following admission; cardiac output and intravascular pressures, blood volume, arterial blood gas tensions, and body weight were measured. These observations were also compared with further measurements made some weeks later just before the patient was discharged. The effects of oxygen and acetylcholine on the pulmonary circulation were also studied. Pulmonary arterial pressure was raised in all patients during their acute illness and had fallen substantially after recovery. The pulmonary arterial pressure throughout the study correlated directly with the arterial carbon dioxide and inversely with the arterial oxygen tensions. The inhalation of 24% and 28% oxygen and the infusion of acetylcholine into the pulmonary artery resulted in a fall in pulmonary arterial pressure, often to levels close to those subsequently seen after recovery from the acute illness. No significant change in cardiac output was observed. It is suggested that the acute pulmonary hypertension seen in these patients is due primarily to pulmonary vasoconstriction resulting from hypoxia.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

An electron-microscope study of the localization of acetylcholinesterase (AChE) has been made in the main uterine artery of the guinea pig, which is supplied by cholinergic dilator and adrenergic constrictor nerves. Large bundles of nonterminal axons were present in the outer adventitia, and terminal axons, containing numerous vesicles, were scattered through the inner adventitia up to 1μ away from the outer layer of smooth muscle cells. About 50% of these axons were within 0.2μ of a muscle cell; the minimum neuromuscular gap found was 0.05μ. No axons were within the media. The outer membranes of axons stained either heavily or lightly for AChE. These two distinct classes appear to represent cholinergic and noncholinergic axons, respectively. In late pregnancy, all cholinergic terminal axons which contained vesicles and were not separated from the muscle by Schwann or elastic tissue were associated with heavy postsynaptic staining which was restricted to that region of the muscle membrane adjacent to the axon. In tissue from virgin animals, most cholinergic terminal axons were associated with only scanty postsynaptic staining. The increase in postsynaptic AChE during pregnancy can be correlated with the increase in sensitivity of the arterial muscle to acetylcholine over this period. Assuming that the association of heavy AChE staining both pre- and postsynaptically is indicative of a functional cholinergic synapse, acetylcholine released up to 1μ away from the muscle may participate in transmission from vasodilator axons in this vessel. Since postsynaptic AChE staining is restricted to discrete areas on the outer muscle cells, probably only these cells are directly affected by transmitter released from nerves.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Studies were carried out during experimental heart failure induced in calves to compare the depletion of cardiac norepinephrine in the failing heart to the histochemical appearance of the adrenergic innervation in this tissue. A correlation has been established between the reduction of norepinephrine concentration and the changes in the distribution of the adrenergic neurotransmitter in the tissues. Absence of fluorescence in terminal varicose fibers in close association with cardiac muscle cells was characteristic of the failing heart. Little or no change occurred in preterminal fibers or in terminal fibers in connective tissue septa or around blood vessels. In two steers, recovery from heart failure was shown to be associated with a virtual restoration of the norepinephrine concentration and of thehistochemical appearance of the adrenergic nerve distribution in 28 days or less. These findings suggest that a reversible abnormality, possibly of neurotransmitter storage or synthesis, or both, is induced in the terminal portion of the cardiac adrenergic innervation as the result of the development of the failure state.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

The kinetics of norepinephrine (NE) metabolism in the heart was studied in genetically hypertensive and normotensive control Wistar rats. Concentrations of endogenous NE were similar in the two groups. However, rates of synthesis of NE were reduced in these hypertensive rats, whether calculated from the rate of decline (fractional turnover rate) of cardiac tritiated NE (3H-NE) after intravenous injection, or estimated from levels of14C-NE in the heart after injection of the precursor14C-L-tyrosine. In experiments with3H-NE the synthesis rate of NE was 30.2 ng/hour/g heart in control and 18.2 ng/hour/g heart in hypertensive rats. The levels of14C-NE found in the heart of normotensive rats given14C-tyrosine were up to 1.4 times those found in hypertensive rats. These findings indicate a reduced rate of release of NE in this form of hypertension and, rather than implicating NE as a primary factor, suggest a secondary, compensatory mechanism.

ISSN:0009-7330    

出版商:OVID    

年代:1969

数据来源: OVID