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At least 325 records · Page 18

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NASA NTRS1973

Otolithic influences on extraocular and intraocular muscles

Selective stimulation of utricular gravireceptors leads to gross activation of the bulbar reticular formation where a strong interaction with evoked spino-bulbo-spinal reflex activity occurs. The utricular neurons encountered by microelectrodes in the lateral vestibular nuclei show four types of elicited activity; two of these display an increased firing rate, and two exhibit pronounced inhibitory effects. Application of a stimulus of long duration and constant intensity to the utricle has shown that rapid adaptation of the peripheral receptors is a prominent feature. The effects of selective utricular stimulation upon eye movements, as recorded by the corneoretinal potential method, have been studied in experiments on cats and monkeys and it can be firmly stated that prolonged stimulation of the utricle can evoke strong primary nystagmus, followed by a secondary nystagmus at the cessation of stimulation. The action of utricular stimulation on ocular reflexes has been examined further, with particular attention to evoked pupillary reactions in both cats and monkeys: constriction during the fast phase of the brisk conjugate eye movement, and dilatation during the flow phase.

Gernandt, B. E.↗

NASA NTRS1975

Control mechanisms of circadian rhythms in body composition: Implications for manned spaceflight

The mechanisms that underlie the circadian variations in electrolyte content in body fluid compartments were investigated, and the mechanisms that control the oscillations were studied in order to investigate what effects internal desynchronization in such a system would have during manned space flight. The studies were performed using volunteer human subjects and squirrel monkeys. The intercompartmental distribution of potassium was examined when dietary intake, activity, and posture are held constant throughout each 24-hour day. A net flux of potassium was observed out of the body cell mass during the day and a reverse flux from the extracellular fluid into the body cell mass during the night, counterbalanced by changes in urinary potassium excretion. Experiments with monkeys provided evidence for the synchronization of renal potassium excretion by the rhythm of cortisol secretion with the light-dark cycle. Three models of the circadian timing system were formalized.

Ede, M. C. M.↗

NASA NTRS1977

Vestibular functions and sleep in space experiments

Physical indices of sleep were continuously monitored in an owl monkey living in a chamber continuously rotating at a constant angular velocity. The electrophysiological data obtained from chronically implanted electrodes was analyzed to determine the chronic effects of vestibular stimulation on sleep and wakefulness cycles. The interaction of linear and angular acceleration on the vestibulo-ocular reflex was investigated in three rhesus monkeys at various angular accelerations.

Perachio, A. A.↗

NASA NTRS1977

Consideration of other primate species as flight animals

The different types of primates which might be used as flight animals are surveyed, and the pros and cons of using them are discussed. Various factors suggest that the most desirable animals for space studies are the rhesus, pig-tailed, Java, and squirrel monkeys. The capuchin monkey has assets for certain types of space experimentation.

Geoffrey H. Bourne↗

NASA NTRS1977

Cortisol-mediated synchronization of circadian rhythm in urinary potassium excretion

Conscious chair-acclimatized squirrel monkeys (Saimiri sciureus) studied with lights on (600 lx) from 0800 to 2000 hr daily (LD 12:12) display a prominent circadian rhythm in renal potassium excretion. The characteristics of this rhythm were reproduced in adrenalectomized monkeys by infusing 5 mg cortisol and 0.001 mg aldosterone, or 5 mg cortisol alone, between 0800 and 0900 kr daily. When the timing of cortisol administration (with or without aldosterone) was phase-delayed by 8 hr, the urinary potassium rhythm resynchronized by 80% of the cortisol phase shift, but only after a transient response lasting 3-4 days. With the same daily dose of adrenal steroids given as a continuous infusion throughout each 24 hr, urinary potassium excretion showed free-running oscillations no longer synchronized to the light-dark cycle. These results indicate that the circadian rhythm of plasma cortisol concentration acts as an internal mediator in the circadian timing system, synchronizing a potentially autonomous oscillation in renal potassium excretion to environmental time cues and to other circadian rhythms within the animal.

Moore-Ede, M. C.↗

NASA NTRS1978

Comparison of synchronization of primate circadian rhythms by light and food

It is a well-documented fact that cycles of light and dark (LD) are the major entraining agent or 'zeitgeber' for circadian rhythms and that cycles of eating and fasting (EF) are capable of synchronizing a few circadian rhythms in the squirrel monkey. In this paper, by contrasting how these rhythms are timed by LD and EF cycles, the differential coupling to the oscillating system within adult male squirrel monkeys is examined. The variables measured are the rhythms of drinking, colonic temperature, and urinary potassium and water excretion. Attention is given to a comparison of the reproducibility of the averaged waveforms of the rhythms, the stability of the timing of a phase reference point, and the rate of resynchronization of these rhythms following an abrupt 8-hr phase delay in the zeitgeber. It is shown that the colonic temperature rhythm is more tightly controlled by LD than EF cycles, and that the drinking and urinary rhythms are more tightly coupled to EF than LD cycles.

Sulzman, F. M.↗

NASA NTRS1978

Circadian rhythm dissociation in an environment with conflicting temporal information

The relative contributions of light-dark (LD) cycles and eating-fasting (EF) cycles in providing temporal information to the circadian time-keeping system were examined in chair-acclimatized squirrel monkeys (Saimiri sciureus). The circadian rhythms of drinking, colonic temperature, urine volume, and urinary potassium excretion were measured with the LD and EF cycles providing either conflicting phases or periods. In conflicting phase experiments, animals were exposed to 24-hr LD cycles consisting of 12 hr of 600 lx followed by 12 hr of less than 1 lx and concurrent 24-hr EF cycles in which the animals ate for 3 hr and then fasted for 21 hr. One group had food available at the beginning and a second group at the end of the light period. In conflicting period experiments, monkeys were exposed to 23-hr LD cycles and 24-hr EF cycles. Analysis of the rhythms showed that both phase and period information were conveyed to the drinking and urinary rhythms by the EF cycle, and to the temperature rhythm by the LD cycle.

Sulzman, F. M.↗

NASA NTRS1979

Methodology for estimation of total body composition in laboratory mammals

A standardized dissection and chemical analysis procedure was developed for individual animals of several species in the size range mouse to monkey (15 g to 15 kg). The standardized procedure permits rigorous comparisons to be made both interspecifically and intraspecifically of organ weights and gross chemical composition in mammalian species series, and was applied successfully to laboratory mice, hamsters, rats, guinea pigs, and rabbits, as well as to macaque monkeys. The procedure is described in detail.

Pace, N.↗

NASA NTRS1981

A 14-day ground-based hypokinesia study in nonhuman primates: A compilation of results

A 14 day ground based hypokinesia study with rhesus monkeys was conducted to determine if a spaceflight of similar duration might affect bone remodeling and calcium homeostatis. The monkeys were placed in total body casts and sacrificed either immediately upon decasting or 14 days after decasting. Changes in vertebral strength were noted and further deterioration of bone strength continued during the recovery phase. Resorption in the vertebrae increased dramatically while formation decreased. Cortical bone formation was impaired in the long bones. The immobilized animals showed a progressive decrease in total serum calcium which rebounded upon remobilization. Most mandibular parameters remained unchanged during casting except for retardation of osteon birth or maturation rate and density distribution of matrix and mineral moieties.

Kazarian, L.↗

NASA NTRS1981

Physiological mechanisms of the nystagmus produced by rotations about an earth-horizontal axis

The physiological basis of the nystagmus produced by rotation about an earth-horizontal axis is investigated with particular emphasis on the unidirectional nystagmus attributed to a bias component. Eye movement recordings were made with dc electro-oculography in alert squirrel monkeys and afferent responses were recorded from semicircular canals and otolith receptors of anesthetized animals upon rotations in the pitch and yaw planes. The eye-movement recordings show the rotation responses in the squirrel monkey to resemble those of other species, including persistent horizontal and vertical nystagmuses during yaw and pitch rotations, respectively, a unidirectional nystagmus at low rotation speeds, and postrotatory responses of relatively small amplitude and duration. The vestibular nerve recordings do not show a directionally specific dc response that can account for the bias component, but instead exhibit sinusoidal responses of peak amplitudes 0-15 and 25-75 spikes/sec for the canals and otolith, respectively. Results thus indicate that the dc signal to the oculomotor centers responsible for the nystagmus is of central origin, most likely based on some transformation of the otolith signals.

Goldberg, J. M.↗

NASA NTRS1982

Chronic central vascular expansion induces hypokalemia in conscious primates

Central vascular expansion maintained for four days in conscious squirrel monkeys reconciles the apparently conflicting short-term fluid and electrolyte responses to water immersion and atrial balloon distension, with those described for prolonged weightlessness during space flight. The monkeys are subjected to an increased lower body positive air pressure (LBPP) of 20 torr which produces a 3 cm water increase in the central venous pressure. Results show a marked increase in the urinary excretion of sodium, potassium, and water during the firxt six hours of LBPP, and the diuresis is maintained throughout the period of LBPP, although the levels of sodium and potassium excretion decline after 24 hours of exposure. Plasma aldosterone transiently drops within the first three hours of LBPP, and then regains normal levels within 24 hours, after which time these levels are maintained despite the continued LBPP stimulus. It is suggested that the normal plasma aldosterone levels observed in the experiments, as well as during space flight, might, epresent a relative hyposecretion in terms of volume homeostasis and a relative hypersecretion with respect to plasma potassium regulation. Thus, kaliuresis and marked natriuresis is confined primarly to the first 24 hours of central volume expansion, a period for which comparable data from space flights are lacking.

Moore-Ede, M. C.↗

NASA NTRS1982

Status of joint US/USSR experiments planned for the Cosmos '83 biosatellite mission

The plans and status of the fourth joint US/USSR biosatellite experiment, scheduled to be conducted in the last half of 1983, are discussed. These experiments will be conducted on board an unmanned Soviet spacecraft and will involve two restrained Rhesus monkeys and 10 pregnant rats, as well as a variety of small plant and radiation biology experiments. Three of the joint studies will use the monkeys for studies of biorhythms, calcium homeostasis, and the cardiovascular system. The fourth experiment will study rodent embryogenesis and neonatal behavior and development following in utero exposure to spaceflight. Specialized sensors and battery powered hardware have been designed, fabricated, and qualified for flight.

Souza, K. A.↗

NASA NTRS1984

Primate body temperature and sleep responses to lower body positive pressure

Cephalic fluid shifts, induced by lower body positive pressure (LBPP) are known to influence various physiological systems (i.e., cardiovascular and renal). In earlier experiments, an apparent change in the arousal state of primates in such LBPP conditions was observed. This study was designed to examine the effects of LBPP on arousal state and body temperature level which is normally correlated with sleep. Chair-restrained male squirrel monkeys were exposed to 40 mmHg LBPP for 90-100 minutes between the daytime hours of 13:00-15:00. Each monkey was placed in a specially modified restraint chair to which they were highly trained. Deep body temperature (DBT) was collected from 10 animals. Sleep parameters were obtained from six animals chronically implanted for sleep recording. A video camera was used to observe each animal's apparent state of arousal. LBPP resulted in an approximate 0.9 C decrease in DBT. During video observation, some animals appeared drowsy during LBPP; however, sleep recording revealed no significant changes in the state of arousal. Thus, LBPP is capable of inducing a mild hyperthermia. Further, the mechanisms underlying the observed lowering of body temperature appear to be independent of arousal state.

Edgar, D. M.↗

NASA NTRS1986

Cataractogenic potential of ionizing radiations in animal models that simulate man

Aspects of experiments on radiation-induced lenticular opacification during the life spans of two animal models, the New Zealand white rabbit and the rhesus monkey, are compared and contrasted with published results from a life-span study of another animal model, the beagle dog, and the most recent data from the ongoing study of the survivors from radiation exposure at Hiroshima and Nagasaki. An important connection among the three animal studies is that all the measurements of cataract indices were made by one of the authors (Lee), so variation from personal subjectivity was reduced to a minimum. The primary objective of the rabbit experiments (radiations involved: Fe-56, Ar-40, and Ne-20 ions and Co-60 gamma photons) is an evaluation of hazards to astronauts from Galactic particulate radiations. An analogous evaluation of hazards from solar flares during space flight is being made with monkeys exposed to 32, 55, 138 and 400-MeV protons. Conclusions are drawn about the proper use of animal models to simulate radiation responses in man and the levels of radiation-induced lenticular opacification that pose risks to man in space.

Lett, J. T.↗

NASA NTRS1989

Automation of learning-set testing - The video-task paradigm

Researchers interested in studying discrimination learning in primates have typically utilized variations in the Wisconsin General Test Apparatus (WGTA). In the present experiment, a new testing apparatus for the study of primate learning is proposed. In the video-task paradigm, rhesus monkeys (Macaca mulatta) respond to computer-generated stimuli by manipulating a joystick. Using this apparatus, discrimination learning-set data for 2 monkeys were obtained. Performance on Trial 2 exceeded 80 percent within 200 discrimination learning problems. These data illustrate the utility of the video-task paradigm in comparative research. Additionally, the efficient learning and rich data that were characteristic of this study suggest several advantages of the present testing paradigm over traditional WGTA testing.

Washburn, David A.↗

NASA NTRS1990

Intrapericardial denervation - Radial artery blood flow and heart rate responses to LBNP

The effects of intrapericardial denervation on the radial artery blood flow velocity (RABFV) and heart rate (HR) responses to LBNP in rhesus monkeys were investigated by measuring the RABFV transcutaneously by a continuous-wave Doppler ultrasonic flowmeter in order to derive an index of forearm blood flow response to low (0 to -20 mm Hg) and high (0 to -60 mm Hg) ramp exposures during supine LBNP. Four of the eight subjects were subjected to efferent and afferent cardiac denervation. It was found that, during low levels of LBNP, monkeys with cardiac denervation exhibited no cardiopulmonary baroreceptor-mediated change in the RABFV or HR, unlike the intact animals, which showed steady decreases in RABFV during both high- and low-pressure protocols. It is suggested that forearm blood flow and HR responses to low-level LBNP, along with pharmacological challenge, are viable physiological tests for verifying the completeness of atrial and cardiopulmonary baroreceptor denervation.

Mckeever, Kenneth H.↗

NASA NTRS1992

Spacelab Life Sciences 3 biomedical research using the Rhesus Research Facility

In 1985, a letter of agreement was signed between the French space agency, CNES, and NASA, formally initiating a joint venture called the RHESUS Project. The goal of this project is to provide a facility to fly rhesus monkeys (Macaca mulatta) to support spaceflight experiments which are applicable but not practical to carry out on human subjects. Biomedical investigations in behavior/performance, immunology/microbiology, muscle physiology, cardiopulmonary physiology, bone/calcium physiology, regulatory physiology, and neurophysiology disciplines will be performed. The Rhesus Research Facility, hardware capable of supporting two adult rhesus monkeys in a microgravity environment, is being developed for a first flight on Spacelab Life Sciences in early 1996.

Ballard, R. W.↗

NASA NTRS1992

Human factors with nonhumans - Factors that affect computer-task performance

There are two general strategies that may be employed for 'doing human factors research with nonhuman animals'. First, one may use the methods of traditional human factors investigations to examine the nonhuman animal-to-machine interface. Alternatively, one might use performance by nonhuman animals as a surrogate for or model of performance by a human operator. Each of these approaches is illustrated with data in the present review. Chronic ambient noise was found to have a significant but inconsequential effect on computer-task performance by rhesus monkeys (Macaca mulatta). Additional data supported the generality of findings such as these to humans, showing that rhesus monkeys are appropriate models of human psychomotor performance. It is argued that ultimately the interface between comparative psychology and technology will depend on the coordinated use of both strategies of investigation.

Washburn, David A.↗