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Biomedical subjects

J Aschoff

Publications and source records attributed to J Aschoff.

At least 73 records · Page 4Linked to original sources
PubMed1971

Human circadian rhythms in continuous darkness: entrainment by social cues.

Three groups of two subjects each were kept in underground chambers, first for 4 days in an artificial light-dark cycle, and thereafter for 4 days in complete darkness. They lived on a rigorous time schedule. Physiological as well as psychological functions were measured at 3-hour intervals. There were no differences in the results between the two sections of the experiment. Social cues are sufficient to entrain human circadian rhythms, and absence of light has no immediate effect on the functions measured.

17-Hydroxycorticosteroids↗
PubMed1967

Human circadian rhythms in activity, body temperature and other functions.

From earlier studies in the field of 24-hr rhythms, it has been concluded that the rhythm is an exogenous one, governed by social influences on behavior and, perhaps, by cosmic stimuli. Recently, new steps have been made in two directions: 1) the phase-relationships between many rhythmic functions have been described in detail; 2) it has been demonstrated that the rhythm is based on an endogenous, self-sustained oscillation. In conditions of isolation, subjects show a 'circadian' rhythm whose frequency deviates from that of the earth's rotation. In case of such free-running rhythms, it may happen that different functions show different frequencies (internal desynchronization), suggesting that there exists a multiplicity of oscillators in the organism. The implications of these findings for problems in applied physiology are exemplified by the results of experiments in which organisms were exposed to shifts of the entraining light-dark cycle (simulating flights in eastward or westward direction). Re-entrainment lasts longer (and hence also the time of diminished efficiency) after a westward than after an eastward flight.

Biological Clocks↗
PubMedDate not supplied

Re-entrainment of circadian rhythms after phase-shifts of the Zeitgeber.

To describe anabrupt shift of the Zeitgeber sufficiently, it is necessary to indicate whether the phase has been advanced or delayed, for how many hours it has been shifted, and what part of the Zeitgeber has been lengthened or shortened respectively. The entrained circadian system usually follows a shift of the Zeitgeber in the same direction and by an equal amount. However, there can be exceptions to both of these rules: a) an instantaneous 12-h shift of a (symmertric) Zeitgeber always represents a delya (= doubling of one-half of its period). In contrast to this, the gradual re-entrainment of the circadian system can be accompalished by either advances or by delays (Fig. 2), it can occur in both dirctions simultaneously by splitting the rhythmic variable (Fig. 1),or it can represent an apparent advance not distinghushable from a delay ( Fig. 6); b) after complietion of re-entraiment, the phase-angle difference psi between organism and Zeitgeber an differ systematically from the pre-shift psi-value...

Activity Cycles↗