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  • 1970-1974  (14)
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  • 1
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    Diurnal rhythm of the pituitary-adrenocortical response to stress: effect of constant light and constant darkness (1970)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The existence of a biological rhythm in the response of animals to noxious stimuli and drugs is well known. However, the mechanism of this response is not well understood. This study was undertaken to describe the existence of a diurnal rhythm in the hypothalamic-pituitary-adrenocortical system before and after stress in female rats kept in controlled environmental conditions in 12L:12D, 24L:OD, or OL:24D. Plasma ACTH and plasma corticosterone concentrations were compared in unstressed animals. The time pattern in the response to stress was determined at four hourly intervals during a 24 hr period in which plasma ACTH and plasma corticosterone were measured at different time intervals. The stress response varied considerably with time of day in both magnitude and duration. The adrenals of rats exposed to constant light for 45 days atrophied, whereas the adrenals of animals kept in constant dark for the same period did not differ significantly from those of controls kept in 12L:12D. The increase in plasma ACTH in response to stress was greater both in the animals maintained in constant light and in constant dark than in the 12L:12D controls. Homeostatic mechanisms involved in these changes are discussed.
    Keywords: Life Sciences (General)
    Type: Life sciences and space research (ISSN 0075-9422); Volume 8; 240-6
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  • 2
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    Mechanisms of action of light on circadian rhythms in the monkey (1970)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Light is considered by many investigators to be the primary Zeitgeber for most physiologic rhythms. In order to study the effects on biorhythms of changing photoperiods and to provide information on the nature of the wave forms and the mechanisms of entrainment, unrestrained male monkeys (Cebus albifrons, Macaca nemestrina) were maintained in a sound-proofed environmental chamber. The Cebus was initially maintained on a 12L:12D schedule; it was subjected to a 180 degrees phase shift for 14 days, then returned to the original photoperiod. In two experiments (24 days; 27 days each) the same monkey was again maintained on a 12L:12D schedule which was gradually altered to a constant light environment. Deep body temperature (DBT) data were obtained with miniature radiotransmitters. Locomotor activity (LMA) was measured by strain gauges. Under the 12L:12D regimens the Macaca DBT cycles were uniform as to phase and wave form for over 60 weeks. These wave forms were analyzed by the use of periodogram and correlogram analyses and by fitting to the Volterra Integro-Differential Equation. Phase angle relationships between Zeitgeber and physiologic parameters were characterized. After the photoperiod phase shift the DBT cycle rephased in about 9 days. During the rephasing process the wave form changed. The shapes of the wave forms of DBT and activity were maintained with increasing light until an 18L:6D photoperiod was reached. The rhythms were entrained to the onset of darkness rather than lights on. Major and minor periods of LMA were detected. Hysteresis diagrams showed that DBT led the onset of major LA by 6 hr and the end of major activity by 2 hr.
    Keywords: Life Sciences (General)
    Type: Life sciences and space research (ISSN 0075-9422); Volume 8; 247-58
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  • 3
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    Circadian rhythm asynchrony in man during hypokinesis. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Posture and exercise were investigated as synchronizers of certain physiologic rhythms in eight healthy male subjects in a defined environment. Four subjects exercised during bed rest. Body temperature (BT), heart rate, plasma thyroid hormone, and plasma steroid data were obtained from the subjects for a 6-day ambulatory equilibration period before bed rest, 56 days of bed rest, and a 10-day recovery period after bed rest. The results indicate that the mechanism regulating the circadian rhythmicity of the cardiovascular system is rigorously controlled and independent of the endocrine system, while the BT rhythm is more closely aligned to the endocrine system.
    Keywords: BIOSCIENCES
    Type: Journal of Applied Physiology; 33; Nov. 197
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  • 4
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    Method for analyses of cyclic physiological data that are nonstationary in time. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The proposed method of studying biologic rhythms permits the biologist to view physiological data dynamically without assuming that the data are stationary in time. Vector representation of data points is employed, and the summation of the vectors (train of vectors) produces a summation dial that is able to detect dynamic changes in the time of the peak as well as random walks (arrhythmia).
    Keywords: BIOSCIENCES
    Type: Journal of Applied Physiology; 33; Nov. 197
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  • 5
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    Thyroid and adrenal cortical rhythmicity during bed rest. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The effects of prolonged bed rest on adrenocortical and thyroid function were assessed in eight healthy males, aged 20-40 years, who were submitted to bed rest for 56 days on a 14L:10D regimen (lights-on, 9:00 AM). Four of these subjects exercised three times daily throughout the experiment. Circulating cortisol, triiodothyronine, and thyroxine, concentrations were determined in blood samples drawn at four hourly intervals for 48-hr periods before, 10, 20, 30, 42, and 54 days during, and 10 days post-bed rest. Significant fluctuations in the circulating levels of all three hormones occurred with peaks at 7:30 AM. The suggestion is advanced that thyroid rhythms may be posture dependent.
    Keywords: BIOSCIENCES
    Type: Journal of Applied Physiology; 33; Nov. 197
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  • 6
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    Fifty-six days of bedrest: Glucose, insulin and growth hormone (1973)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: AEROSPACE MEDICINE
    Type: Life Sci. Publ., Vol. 1; 2 p
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  • 7
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    Phase relationships between circadian rhythms and the environment in humans during hypokinesis (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: BIOSCIENCES
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  • 8
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    Noradrenergic control of circadian rhythms in Cebus albifrons (1973)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: AEROSPACE MEDICINE
    Type: Life Sci. Publ., Vol. 1; 7 p
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  • 9
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    Resynchronization rated of a psychomotor test rhythm in man following translongitudinal flights (1973)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: AEROSPACE MEDICINE
    Type: Life Sci. Publ., Vol. 1; 2 p
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  • 10
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    Circadian, endocrine, and metabolic effects of prolonged bedrest: Two 56-day bedrest studies (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two bedrest studies of 56 days each have been conducted to evaluate the effects of prolonged bedrest on circadian synchrony and endocrine and metabolic function. Measurements included the pituitary-adrenal, thyroid, parathyroid, insulin-glucose-growth hormones, catecholamine excretion, body temperature, and heart rate. The results indicated that a rigorous regimen of exercise did not prevent the endocrine and metabolic effects of prolonged bedrest. Changes in circadian, endocrine, and metabolic functions in bedrest appear to be due to changes in hydrostatic pressure and lack of postural cues rather than to inactivity, confinement, or the bleeding schedule. Prolonged bedrest, particularly beyond 24 days, resulted in rhythm desynchronization in spite of well regulated light/dark cycles, temperature, humidity, activity, and meal times and meal composition and in increased lability of all endocrine parameter measured. It also resulted in an apparent insensitivity of the glucose response to insulin, of cortisol secretion to ACTH, and of growth hormone secretion to hypoglycemia.
    Keywords: BIOSCIENCES
    Type: NASA-TM-X-3051 , A-5339
    Format: application/pdf
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