Work Jürgen Aschoff

1 work

1.1 work
1.2 aschoff s rule
1.3 later work
1.4 aschoff–wever model
1.5 influence on other researchers

work

aschoff provided strong foundation field of chronobiology through research on circadian rhythms , entrainment in many different organisms such rats, mice, birds, macaques, monkeys, , humans. research focused on understanding properties of circadian rhythms , how these rhythms can change in response stimuli. later work more applicable pathologies, such psychiatric disorders , dangers of shift work schedules, can result manipulating specific zeitgebers. aschoff s work in field of chronobiology introduced idea shifting 1 s light-dark cycle can result in harmful effects, such correlations mental illness.

early work

aschoff began research on physiology of thermoregulation self-experimentation. discovered there 24-hour rhythm of variation in body temperature. after these experiments, began investigating basic mechanisms of circadian rhythm. in 1950s, met , began collaborate erwin bünning , colin pittendrigh. aschoff began further experimentation studying circadian rhythms of birds , mice under constant conditions. results led conclusion circadian oscillations of biological processes innate , did not require prior exposure 24-hour day expressed.

aschoff applied these methods experiments human circadian rhythms building underground bunker isolate human subjects external environmental cues. subjects placed in bunker allowed turn lights on or off according own internal rhythms. after on twenty years of tracking sleep-wake cycles, body temperature, urine output, , other physiological , behavioral outputs, aschoff , collaborator rütger wever concluded humans have endogenous circadian oscillators. discovery has become foundation our understanding of many medical problems such aging, sleep disorders, , jet lag.

in 1960, aschoff coined term zeitgeber (from german time giver or synchronizer ) refer external, environmental cues synchronize endogenous oscillator environmental cycle. investigate properties of natural endogenous oscillators, aschoff exposed organisms constant conditions without zeitgeber cues (either constant light or constant darkness). observations paper formulated fundamental rules of biological clocks.

aschoff s rule

from experiments communicated in 1960, aschoff noted under constant light conditions, activity phase shortens in nocturnal organisms , lengthens in diurnal organisms. these trends termed alpha compression , alpha expansion, respectively. in tribute mentor, pittendrigh called observation aschoff s rule in 1960 publication, , designation remains today.

aschoff s rule related model of parametric entrainment, assumes continuous phase changes. aschoff , pittendrigh approached field different models of how oscillators entrain, resulted in different predictive models. aschoff s parametric model states entrainment occurs through gradual changes in clock adapt new light-dark cycle. although no longer recognized correct model in field, serge daan suggested in 1998 aschoff made qualitative contributions provide valuable alternatives inconsistencies in current field.

later work

much of aschoff s later work involved tests on human subjects. found absence of light-dark cycle not prevent humans entrainment. rather, knowing time of day social cues, such regular meal times, sufficient entrainment. aschoff found different circadian outputs such body temperature , locomotor activity can either internally synchronized or desynchronized depending on strength of zeitgeber. in constant darkness, rectal temperature , sleep onset , duration became desynchronized in subjects, , rectal temperature @ time of sleep onset correlated duration of bout of sleep. hypothesized internal desynchronization, phase differences resulting period differences between 2 circadian output processes, related many psychiatric disorders.

some of aschoff s later work integrated initial interest in thermoregulation work on circadian rhythm. found circadian rhythm in thermal conductance, measurement of heat transfer body. minimal conductance in mammals , birds oscillates circadian phase, wide range of conductance values. allows animals release heat during activity period, when have higher basal metabolism, conserve heat during rest period, when have lower basal metabolism. in birds, circadian rhythm in conductance results circadian rates of evaporative heat loss. in mammals, conductance oscillates circadian rhythms in body s heat resistance , blood flow rate.

following on temperature studies, found mammalian species can entrain temperature cycle, temperature weak zeitgeber compared light-dark cycle.

aschoff described masking signals inputs circumvent pacemaker nevertheless lead modulation of circadian behavior controlled pacemaker. parametric entrainment entrainment not result instant change in phase, governed phase response curve, in case of masking signals. term aschoff used phenomenon “arousal” due non-photic zeitgebers. data experimental assays show relationship between masking effects , phase, leading “demasking” effect whereby animals arrhythmic in constant conditions have free-running periods in high frequency light-dark cycles. aschoff concluded oscillator or circadian clock “integrates” on intensity of light has been exposed, , responds change in period of activity, seen in greenfinches, chaffinches, hamsters, , siskins. aschoff concluded, however, non-parametric effects, opposed parametric effects, principal source of entrainment.

aschoff–wever model

1) increase in duration of sunset advances phase of organism nocturnal , diurnal animals.

2) increase in strength of zeitgeber should increase sunset duration increases.

influence on other researchers

aschoff has published articles both pittendrigh , serge daan, latter pivotal researcher in chronobiology. in recent work, daan has attempted reconcile idea of parametric entrainment light proposed aschoff non-parametric model of entrainment proposed pittendrigh, , results 2008 paper daan s lab lend further evidence aschoff s model of parametric entrainment.

although aschoff’s collaboration gustav kramer never realized due latter’s sudden death, aschoff continued use birds model organisms , work ornithologists.