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J Aschoff

Publications and source records attributed to J Aschoff.

At least 37 records · Page 2Linked to original sources
PubMed1989

Masking of circadian activity rhythms in canaries by light and dark.

Canaries (Serinus canaria) were kept singly in cages placed in an artificially illuminated, soundproof cabinet. Perch-hopping activity was recorded by means of a computer system. In three series of experiments, the activity rhythms of the birds were entrained to 24 hr by light-dark (LD) cycles with 4, 12, or 20 hr of light (L), respectively. The intensity of illumination was 10 lux in L and 0.25 lux in darkness (D). Under LD 4:20 and 12:12, the intensity of D was increased daily at the same zeitgeber time to 1 lux for 1 hr (L pulse) during about 8 consecutive days. This sequence was followed by 8 days without L pulses before giving another series of L pulses at a different zeitgeber time. Under LD 20:4, the intensity of L was decreased to 1 lux for 1 hr (D pulse). The activity of all birds was more or less increased by the L pulses (positive masking) and decreased by the D pulses (negative masking). The level of masking activity during the L and D pulses depended on the circadian phase at which the pulses were administered. Positive masking by L pulses was minimal about 5 hr after the beginning of D, and increased steadily thereafter. Negative masking by D pulses was maximal at the beginning and the end of L, and minimal during the middle.

Animals↗
PubMed1988

VEP, physiological and psychological circadian variations in humans.

Amplitudes and latencies of components of visual evoked potentials (VEPs) were analysed during the 24-h cycle in humans. Circadian variations of other physiological parameters (oral temperature, urine volume and urinary potassium excretion) and of psychomotor performance (grip strength, tapping rate, visual reaction time and performance on a letter cancellation test) were also assessed. Eight male volunteers (aged 20-34 years) were tested twice over a period of 30 h. Test sessions took place every 3 h (1100 hours, 1400 hours etc.). VEPs were elicited by checkerboard pattern reversals. Significant circadian variations in the VEPs were found for the latencies of the P100 and N140 components, which were longest between 2 a.m. and 5 a.m. (P100: 103 ms; N140: 138 ms) and shortest at about 5 p.m. (P100: 97 ms; N140: 130 ms). Pronounced circadian variations were also observed in physiological parameters and in psychomotor performance measures. Circadian variation of oral temperature was correlated with the 24-h profiles of most of the other variables. Time courses of VEP latencies and oral temperature were moderately negatively correlated. However, from the data presented it seems premature to conclude that there is a common pacemaker for the circadian variations of the different parameters investigated.

Adult↗
PubMed1988

Masking of circadian activity rhythms in hamsters by darkness.

Wheel-running activity was recorded in male golden hamsters (Mesocricetus auratus) kept in constant dim illumination. For periods of several weeks the lights in the cabinet were turned off daily at the same time of day, either for 1 h or 2 h. Despite these periodically recurring dark pulses, the circadian activity rhythms continued to free-run, and consequently crossed through the pulses at a more or less regular speed. During a dark pulse, the activity was usually enhanced. The amount of these masking effects varied with the phase of the circadian cycle at which the pulse occurred. The responses were maximal a few hours after the onset of spontaneous activity, and minimal during the rest-time of the animal.

Animals↗
PubMed1986

Circadian activity rhythms in squirrel monkeys: entrainment by temperature cycles.

Eight squirrel monkeys (six male, two female), kept singly in wire-mesh cages, were housed in groups of three in a climatic chamber. Locomotor activity was recorded by means of photocell systems or mobile climbing trees. For time spans of several weeks, the animals were alternately exposed to each of three different conditions: (1) constant conditions at various levels of light intensity and ambient temperature; (2) a 24-hr light-dark (LD) cycle at constant temperature; (3) a 24-hr cycle of low (about 17 degrees C) and high (32 degrees C) temperature in constant illumination (LL). In constant conditions, the free-running activity rhythms always had periods longer than 24 hr, without systematic dependencies on ambient temperature, but with a tendency to lengthen the period when the intensity of illumination was increased. All animals were entrained by a weak LD zeitgeber (10:1 lux). Exposure to cycling ambient temperature resulted in entrainment in about 45% of all tests. Usually, the entrained animals were active during the cold fraction of the cycle, but some records suggested entrainment in a warm-active mode. In addition, temperature changes exerted strong masking effects, mainly with increases of activity during the warm fraction of the cycle.

Animals↗
PubMed1986

Meal timing in humans during isolation without time cues.

In an underground isolation unit, 46 subjects lived singly without time cues under conditions of self-selected light-dark (LDs) cycles or constant illumination (LL). They all developed free-running circadian rhythms that either remained internally synchronized (i.e., with equal periods in all functions; n = 24) or became desynchronized by a sudden lengthening (n = 14) or shortening (n = 8) of the sleep-wake cycle. Six further subjects were synchronized to 24 hr by an externally controlled LD cycle. All subjects had to prepare their own meals. Signals were given by the subjects when they woke up, had a meal, and retired. Of the 52 subjects, 43 consistently had three meals per "day," and 9 had two meals, irrespective of the length of the circadian cycle and despite the fact that, due to desynchronization, wakefulness varied from over 30 hr to less than 12 hr. The intervals between meals, between wake-up time and breakfast, and between last meal and bedtime were "stretched" or "compressed" in strong proportionality to the duration of wakefulness.

Adult↗
PubMed1986

Effects of feeding cycles on circadian rhythms in squirrel monkeys.

Squirrel monkeys (Saimiri sciureus) were housed singly in cages equipped with a tree for climbing to measure locomotor activity, and with a movable food cup that could be arrested automatically. The animals were kept in continuous dim illumination (LL), twice interrupted by several weeks of entrainment by a light-dark (LD) 12:12 cycle. Apart from three control sections in which the food cups were unlocked continuously (ad libitum feeding), food was accessible for 3 hr per day only, with interfeeding intervals varying from 23 to 26 hr (periodic restricted feeding, or RF). During LD entrainment, the imposition of an RF schedule resulted in anticipatory behaviors, represented by increased tugs at the food cup and a pause in locomotor activity preceding the feeding time. In LL, the animals showed free-running circadian rhythms of locomotor and "feeding" activity that nearly always persisted when ad libitum feeding was replaced by RF. The period (tau) of the free-running rhythm was slightly modulated in relation to the varying interfeeding intervals (T), but entrainment was never achieved except in one test with an animal whose tau was very close to T. It is concluded that periodic availability of food represents an extremely weak zeitgeber, if any, for the circadian pacemaker of squirrel monkeys.

Animals↗
PubMed1986

[Surgically treated carpal tunnel syndrome--clinical and electrophysiologic follow-up].

The carpal tunnel syndrome is described as a compression of the N. medianus under the retinaculum flexorum with the causes for this syndrome being of the most varied nature. The aetiology is multifactorial with frequent alterations of the connective tissue being observed in the histological specimen, i.e. chronic inflammatory proliferations or fibrotic degenerations. Direct pressure measurements have shown that the pressure is markedly higher both at rest and extension or flexion as compared to normal healthy subjects. An exact diagnosis requires a measurable prolongation of the distal motorial latency. Surgery is the treatment of choice to ensure perfect recovery. For this purpose the retinaculum flexorum must be entirely split, and our experiments have shown that the splitting of the epineurium yields good results. The microsurgical interfascicular neurolysis, however, should be considered in special cases only. Complaints tend to disappear fairly quickly in the majority of cases, i.e. pain recedes by 90%, sensitivity disorders by more than 70% and muscle atrophy by 50%. The operation enables a measurable improvement of the distal motorial latency. The incidence of postoperative complications is relatively low, and if they do occur, then they are negligible and without any bearing on the final surgical result. Persistent residual complaints are very often due to other accompanying diseases such as cervical vertebral column syndrome, cervical ribs etc.

Carpal Tunnel Syndrome↗
PubMed1985

On the perception of time during prolonged temporal isolation.

UNLABELLED: In an underground isolation unit, 42 subjects were living singly for time spans of at least 7 days up to more than a month. Except three who were entrained to 24 h by an externally controlled light-dark cycle (LD), subjects had no time cues and developed free-running circadian rhythms either in self-selected LD-cycles or in constant illumination. Each subject had to give a signal whenever he thought that 1 h had passed. In addition, 30 subjects produced short-time intervals within the range from 10 to 120 s. RESULTS: The 1-h estimates were longer than 1 h, and had a strong positive correlation with the duration of wakefulness alpha as well as with the length of the circadian cycle. The short time estimates were equally distributed between under- and over-estimation of the required interval, and they were neither correlated with the 1-h estimates nor with alpha. It is concluded that long and short time estimates are based on different mechanisms.

Adolescent↗
PubMed1984

Seasonality in freerunning circadian rhythms in man.

Retrospective analysis of data collected over 15 years in normal subjects isolated from time cures showed seasonal rhythms in the circadian period of the core temperature rhythm, in the amount of sleep (both shorter in spring and longer in autumn), and in the incidence of internal desynchronisation (most often in summer). Women slept longer than men at all times of year.

Body Temperature↗
PubMed1984

Circadian timing.

Explore the source record for details and available documents.

Body Temperature↗
PubMed1983

Effects of restricted daily feeding on freerunning circadian rhythms in rats.

Male rats were kept in conditions of constant dim illumination and alternately fed ad lib or for 2 or 4 hr per day only. Locomotor activity was recorded as wheel running and as activity in the cage by a microphone system. At selected days before, during and after restricted feeding (RF) blood samples were taken from the tail in 4-hr intervals for the determination of plasma corticosterone. Under both schedules of RF, the circadian rhythms of activity and of plasma corticosterone continued to freerun without significant changes in period or phase while the feeding times were anticipated by increases in activity and in plasma corticosterone. After the termination of RF, the anticipatory components persisted for several days and merged into the freerunning rhythms through transients. The results support the concept of two systems with oscillatory capacities: the freerunning system which is driven by a pacemaker and not affected by RF, and the anticipatory system which can be uncoupled from the freerunning system by an entraining feeding cycle.

Animals↗
PubMed1983

Effects of temperature on the circadian rhythm of pig-tailed macaques Macaca nemestrina.

Activity rhythms of pig-tailed macaques, Macaca nemestrina, were recorded under three different conditions: 1) constant illumination (LL) and constant ambient temperature; 2) light-dark (LD) cycles with 12 h of bright light and 12 h of dim light (LD 12:12) at constant ambient temperature; 3) cycles with 12 h of high (32 degrees C) and 12 h of low temperature (17 degrees C) in LL. In constant conditions the period of the free-running rhythm was positively correlated with light intensity. Ambient temperature had no systematic effect on the period in LL of 0.45 and 45 lx; when measured in 100 or 450 lx, the period was consistently longer at 32 than at 17 degrees C. Temperature cycles with a range of 15 degrees C resulted in entrainment in three adult animals, but not at all tests; two adults and a couple of young animals were never entrained. Entrainment by temperature was less accurate than that by LD. The results demonstrate that a temperature cycle can entrain the circadian activity rhythm of an homeothermic mammalian species but that it is a very weak zeitgeber compared with LD cycle.

Animals↗
PubMed1982

Visually evoked potentials in Friedreich's ataxia.

Visual evoked potentials to pattern-reversal stimulation have been recorded in 45 patients with Friedreich's ataxia. In six patients, no response could be obtained because of optic atrophy; altogether, pathological results were found in 25 patients (55%). Normal latencies were recorded in 20 patients (45%). No statistically significant connection could be drawn between the result of the VEP testing and visual acuity, age, or onset and duration of sickness, but there was a strikingly familiar accumulation of results. There is a good conformity between our results and the incidence of optic atrophy in later stages of the disease as shown by pathological-anatomical and epidemiological studies. We have demonstrated that optic nerve lesions in Friedreich's ataxia are not as rare as is frequently assumed and that the VEP is a valuable tool for detecting them. On the other hand, unfortunately, the VEP is of no help in the differential diagnosis of Friedreich's ataxia versus multiple sclerosis.

Adult↗
PubMed1981

[Clinical applications of visual evoked potentials for detection of chiasmal and postchiasmal lesions (author's transl)].

Visual evoked potentials (VEP) were recorded in 18 patients with pathologic processes confirmed by computerized tomography in the chiasmal (n = 9) and parietooccipital region (n = 9). Reactions from the right and left hemisphere could be recorded separately in spite of using a simple one-channel apparatus and electrodes only at Oz and Cz. In 17 cases changes of the VEP provided information concerning the localization and extension of the lesion. In chiasmal processes we found a prolongation of monocular latencies, and a delayed or extinguished reaction to half-field stimulation from temporal retinal areas. However, the VEP was often pathologic for half-field stimulation of the nasal hemiretina. Pathologic VEPs were not always accompanied by visual field defects. In contrary to patients with chiasmal processes no pathologic reaction could be found to full-field stimulation in parieto-occipital lesions. Only when the affected hemisphere was stimulated selectively were diminution of amplitudes, prolongation of latencies, or extinguished responses observed. The VEP changes were uniform despite the cause of the lesion (tumor, ischemia). In chiasmal and parieto-occipital processes the VEP supplements computerized tomography by detecting deficits in function. This method appears suitable for monitoring the course of disease before and after neurosurgery.

Brain Diseases↗
PubMed1981

The dependence of onset and duration of sleep on th circadian rhythm of rectal temperature.

The sleep-wake cycle and the circadian rhythm of rectal temperature were recorded in subjects who lived singly in an isolation unit. In 10 subjects, the freerunning rhythms remained internally synchronized, 10 other subjects showed internal desynchronization. Times of onset and end of bedrest ("sleep") were determined in each cycle and referred to the phase of the temperature rhythm. In the synchronized subjects, onset of sleep occurred, on the average, 1.34 h before the minimum of temperature, and end of sleep 6.94 h thereafter, with narrow distributions. The desynchronized subjects had a broad bimodal distribution of sleep onsets (peaks 6.3 and 1.3 h before the minimum); the duration of sleep varied between more than 15 h when sleep began about 10 h before the temperature minimum, and less than 4 h when sleep began several hours after the minimum. The dependence of sleep duration on body temperature is interpreted as a continuing action of the coupling forces between the two rhythms after mutual synchronization is lost.

Adult↗
PubMed1980

[On reproducibility of circadian rhythms in man (author's transl)].

On the basis of our own experimental data and those from the literature, the reproducibility of day-night variations in physiological functions--their 'circadian pattern'--is examined in five sections. They concern the problem of intra- and interindividual variability, demonstrated by the rhythm of deep body temperature, the dependence of the pattern on experimental conditions, and as further examples circadian rhythms in the endocrine system, in blood constituents, in blood pressure and in psychomotor performance. The survey is considered to contribute to the question of how important the circadian temporal structure may be in the search for reference values and hence in diagnosis.

Blood Cell Count↗