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J Aschoff

Publications and source records attributed to J Aschoff.

At least 55 records · Page 3Linked to original sources
PubMed1979

Circadian rhythms: influences of internal and external factors on the period measured in constant conditions.

The article reviews most of the data available on the period tau of freerunning circadian rhythms, measured in constant conditions. Emphasis is placed on the effects of light intensity and ambient temperature on tau, with references to influences of other external as well as internal factors. In the introduction, examples are given of spontaneous and induced variations in tau and its dependence on the experimental history. The discussion concentrates largely on results obtained from arthropods and vertebrates.

Age Factors↗
PubMed1979

Circadian rhythms of locomotor activity in the squirrel monkey, Saimiri sciureus, under conditions of self-controlled light-dark cycles.

Locomotor activity was recorded from three squirrel monkeys, Saimiri sciureus, housed singly in cages inside a sound-proof chamber. Each animal was exposed twice to each of three conditions; continuous dim illumination (dim LL), continuous bright illumination (bright LL), and conditions in which the animal could turn on bright light by itself (self-controlled light-dark cycle: LDs). The mean circadian period, tau, the activity time, alpha, and the amount of activity, A, were computed for each single condition. It was found that, in LL, tau, alpha and A were positively correlated with the intensity of illumination. In LDs, tau was longer and A larger than in either dim or bright LL. The lengthening of tau in squirrel monkeys by a self-controlled light-dark cycle is compared with similar findings in birds and man, and is discussed in view of the observation that the tau-characteristics of diurnal mammals deviate from those known from other diurnal species of vertebrates.

Animals↗
PubMed1978

Circadian activity rhythms of the pig-tailed macaque, Macaca nemestrina, under constant illumination.

Locomotor activity was recorded in singly caged pig-tailed macaques Macaca nemestrina in constant conditions with intensities of illumination varying between 0.003 lux and 100 lux. Each animal was kept in at least 5 different conditions for 2-3 weeks each. Three quantities of the circadian rhythm: the period, the duration of activity as opposed to rest, and the amount of activity per period, could be shown to be positively correlated with light intensity. As in 6 other diurnal primate species, these findings contradict the so-called circadian rule according to which opposite correlations should exist between the circadian parameters and light intensity in diurnal and in nocturnal species of animals.

Activity Cycles↗
PubMed1978

[Circadian rhythms in the endocrine system (author's transl)].

In four sections, the contribution reviews data on 24-hour variations of cortisol, growth hormone, prolactine, testosterone, LH and FSH in the human plasma. 1) Experiments on isolated subjects show that the 24-h variation of cortisol is based on an endogenous circadian rhythm which can be independent from the rhythm of sleep and wakefulness. 2) The various pattern each of which has been described in good correspondence by several groups of authors, suggest a series of hormones with a strong circadian component (e.g. cortisol) to those with a weaker (testosterone) or even without a circadian component (FSH). 3) The sleep-wake-cycle influences the phase of hormone rhythms by various degrees; therefore, a uniform reference to sleep time seems preferable to a reference to local time in order to compare several rhythms. 4) The rhythms of cortisol and growth hormone as described in man agree satisfactorily with those in other vertebrate species.

Adrenal Cortex Hormones↗
PubMed1978

Phase relations between a circadian rhythm and its zeitgeber within the range of entrainment.

The regular day-night changes in tissues, physiologic functions, and behavior of organisms are based on endogenous rhythmic processes which under constant conditions continue with periods slightly deviating from 24 h. These 'circadian' rhythms have properties of self-sustained oscillators. Under natural conditions, circadian rhythms are synchronized (entrained) to 24 h by periodic factors in the environment, the so-called 'zeitgebers'. In the laboratory, circadian rhythms can also be entrained to periods other than 24 h within certain limits. Data on the phase relationship between the circadian rhythm and an entraining light-dark cycle for vertebrates, insects, plants, and unicellular organisms are reviewed.

Activity Cycles↗
PubMed1978

[Circadian rhythms in man (author's transl)].

The circadian system of man consists of a multiplicity of self-sustaining oscillators which are coupled to each other and which can be entrained by periodic factors in the environment, the zeitebers. From the interaction of these two forces results a high degree of temporal order within the organism. Freerunning circadian rhythms to be observed in isolated subjects living in constant conditions, usually have periods close to 25 h. The circadian system can split into components that freerun with different frequencies (internal desynchronization) and that partially can be entrained by zeitgeber. Analysis of the circadian organization has become of increasing importance for theory and practive in medicine.

Body Temperature↗
PubMed1976

Brain temperature in the unanaesthetized chicken: its circadian rhythm of responsiveness to light.

Temperatures were recorded continuously for up to 4 days in the brain of 8 unanaesthetized, moderately restrained male chickens, kept in light-dark cycles (LD) of 30:30 or 60:60 min duration. In all cases, brain temperature was higher in L than in D. Temperatures increased or decreased immediately after the light was turned on or off, respectively, but did not reach a new level until after about 30 min. Average values of temperature obtained during the last 10 min in L and D were used for further analysis. The changes of brain temperature due to changes in light intensity were super imposed to marked circadian oscillations. The computed differences between L- and D-values were found to be a function of the circadian phase. For 4 out of the 8 chickens a uniform circadian rhythm of responsiveness to light could be demonstrated, with two maxima coinciding with the ascending and descending circadian slope, respectively. In view of the evidence suggesting brain temperature as a reliable measure of the degree of arousal, it is concluded that light has a stronger arousing effect on the chicken in the morning and in the evening than in the middle of the day or the night.

Animals↗
PubMed1976

Human circadian rhythms: a multioscillatory system.

After a brief review on temporal order within the human organism and implications for chronopharmacology, the paper discusses evidence indicating that the human circadian system consists of a multiplicity of oscillators. Subjects who live in isolation without time cues show free-running circadian rhythms deviating from 24 hours. Often, the activity rhythm (wakefulness and sleep) and other rhythmic variables (e.g., temperature) have the same circadian period of about 25 hours (referred to as the state of internal synchronization) but on occasions the activity period may become substantially longer (e.g., 33 hours) while the other rhythms continue with a period of about 25 hours. Such a state is termed internal desynchronization. There are also cases where the activity rhythm can reach extreme values of about 50 hours; to such a circa-bi-dian rhythm other variables are again synchronized, but in a 2:1 ratio. Internal desynchronization can occur both by shortening and by lengthening the activity rhythm. In these two cases the periods of other rhythms also change slightly in a direction opposite to that of the activity rhythm, indicating a loss of coupling between two classes of basic oscillators that both influence the two groups of overt rhythms but by different extents.

17-Hydroxycorticosteroids↗
PubMed1973

Circadian rhythms of chicken brain temperatures.

1. Brain temperature was recorded continuously for up to 18 days in unanaesthetized adult male chickens. With the use of a guide box of plexiglas screwed into a trephine of the calvarium, several thermocouples could be inserted at various depths into the brain at the same time.2. While brain temperatures were being recorded, each chicken was placed in a small circular arena and kept either in a light-dark cycle (LD 12:12 hr) or in conditions of constant dim illumination (LL) within a soundproof chamber.3. Under LD-conditions, the range of oscillation (the difference between maximum and minimum within one period) in brain temperature at any one site was about 1.5 degrees C. During the 12 hr of light the temperature often reached a plateau for several hours. During darkness, a minimum of temperature was usually reached shortly after light-off. Brain temperature started to rise several hours before light-on.4. All eleven chickens tested under LL-conditions showed free running circadian rhythms of brain temperature, with mean periods varying between 22.75 and 25.00 hr (overall mean: 23.69 hr). The range of oscillation in LL-conditions was smaller than in LD-conditions, but was seldom less than 1.0 degrees C.5. In LD as well as in LL, continuous fluctuations of temperature with a much higher frequency were superimposed on the circadian cycle. The fluctuations occurred synchronously at all sites of the brain and were of the same order of magnitude (frequency and range) during wakefulness as during sleep.

Animals↗