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  • 1980-1984  (6)
  • 1975-1979  (3)
Collection
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 45 (1983), S. 213-227 
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2006-01-16
    Description: Criteria are given for selecting the macaca mulatta as the analogue of the human in the study of cerebral circulation, particularly the control of the cerebral vascular bed during normal and stressful conditions. Topics discussed include surgical preparation of subject; responses to changes in arterial pressure, oxygen, and carbon dioxide; innervation of cerebral vessels; cerebral flow response to acceleration; and cerebral blood flow and cerebellar stimulation.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: The Use of Nonhuman Primates in Space; p 83-101
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  • 3
    Publication Date: 2019-06-28
    Description: Horizontally body-casted rhesus monkeys are used as an animal model in order to study the physiological changes known as cardiovascular deconditioning which occur during weightless conditions. No difference was found between the experimental and control animals in heart mitochondrial oxidative phosphorylation which indicates that no apparent changes occurred in the primary energy-producing system of the heart. A marked increase in cytochrome oxidase activity was observed in the casted primate heart mitochondria compared to controls, while a 25% decrease in respiratory substrate-supported calcium uptake was found in casted primate heart mitochondria compared to controls. Sacroplasmic reticulum isolated from the primate hearts revealed marked changes in calcium transport activities. It is concluded that the marked depression in cardiac sarcoplasmic reticulum functions indicates altered calcium homeostasis in the casted-primate heart which could be a factor in cardiovascular deconditioning.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 4
    Publication Date: 2019-06-28
    Description: Experiments were performed on horizontally casted primates (male rhesus monkeys) in order to note changes in blood volume caused by horizontal restraint, to compare orthostatic tolerance before and after casting using the responses to upright tilting, to begin to uncover the cardiovascular and neural mechanisms involved in deconditioning, and to compare the data with that obtained from bed-rested human subjects and from humans exposed to weightlessness. Bolus injections of norepinephrine of 2.0 microgram/kg, phenylephrine of 4.0 microgram/kg, and nitroprusside of 2.0 microgram/kg were administered; and aortic pressure and heart rate were recorded during the injections. The results indicate that the horizontally casted primate is a valid animal model for studying the effects of simulated zero-G on the human cardiovascular system.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: p. S-27
    Format: text
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  • 5
    Publication Date: 2019-06-28
    Description: The purpose of this study was to investigate the effects of long-term horizontal body position on baroreceptor reflex control of heart rate. Six male rhesus monkeys (6.2-9.4 kg) were given bolus injections of 4.0 microgram/kg, phenylephrine during each of the following conditions: awake, anesthetized (10 mg/kg ketamine HCl), and after beta-blockade (1 mg/kg propranolol HCl) before, 7, 14, and 28 days after being placed in a horizontal body cast. R-R interval vs. systolic arterial pressure was plotted, and the slope was determined by least-squares-fit linear regression. Baroreceptor slope was significantly reduced by 7 days of horizontal body position and remained attenuated throughout the 28-day restraint period both before and after beta-receptor blockade. These data are consistent with the thesis that prolonged exposure to a zero-gravity environment impairs autonomic reflex regulation of the cardiovascular system.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Journal of Applied Physiology: Respiratory; vol. 52
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  • 6
    Publication Date: 2019-06-28
    Description: To simulate the weightless condition, eight rhesus monkeys, instrumented with solid-state pressure transducers, were horizontally restrained in body casts for 28 days. Blood volume decreased an average of 13% after 14 days of restraint, due mainly to a drop in plasma volume. Aortic pressure and heart rate responses to norepinephrine and phenylephrine decreased after 14 days of restraint. The monkeys did not show a statistically significant decreased tolerance to a 90 deg sudden upright tilt after horizontal restraint. During the fifth week of casting, four animals were subjected to +Gz acceleration tests on a centrifuge. The acceleration tolerance of the casted monkeys was significantly reduced compared to four similarly instrumented control animals. These findings indicate that the cardiovascular deconditioning associated with simulated weightlessness results from an inability to maintain central blood volume during orthostatic stress.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 7
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    Unknown
    In:  Other Sources
    Publication Date: 2019-06-27
    Description: A fastigial pressor response has been elicited in the anesthetized mongrel dog. Stimulation within the rostral portions of this nucleus results in mean arterial pressure rises up to 150 mmHg above control. A proportional tachycardia is simultaneously evoked which may rapidly attain heart rates of 190 beats/min above control levels. Peak tachycardias immediately subside and often the heart rate declines below control values during stimulation while arterial pressure remains elevated. When either the carotid sinuses were isolated by ligation or a bilateral vagotomy was performed, the fastigial tachycardia was sustained. The response could still be attained when submaximal doses of alpha-chloralose anesthesia or high levels of barbiturates (30-40 mg/kg) were given. Both portions of the response result from widespread sympathetic activation; however, buffering of the response through the baroreceptor reflexes is only demonstrated in the cardiac segment of the response.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Journal of Applied Physiology; 41; Oct. 197
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  • 8
    Publication Date: 2019-06-27
    Description: The development of aerospace systems capable of very high levels of positive vertical accelerators stress has created a need for a better understanding of the cardiovascular responses to acceleration. Using a canine model, the heart and cardiovascular system were instrumented to continuously measure coronary blood flow, cardiac output, left ventricular and aortic root pressure, and oxygen saturation in the aorta, coronary sinus, and right ventricle. The animals were exposed to acceleration profiles up to +6 G, 120 s at peak G; a seatback angle of 45 deg was simulated in some experiments. Radiopaque contrast medium was injected to visualize the left ventricular chamber, coronary vasculature, aorta, and branches of the aorta. The results suggest mechanisms responsible for arrhythmias which may occur, and subendocardial hemorrhage which has been reported in other animals.
    Keywords: AEROSPACE MEDICINE
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  • 9
    Publication Date: 1983-10-01
    Print ISSN: 0066-4278
    Electronic ISSN: 1545-1585
    Topics: Biology , Medicine
    Published by Annual Reviews
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