K
Karl-Arne Stokkan
Researcher at University of Tromsø
Publications - 64
Citations - 3874
Karl-Arne Stokkan is an academic researcher from University of Tromsø. The author has contributed to research in topics: Melatonin & Pineal gland. The author has an hindex of 27, co-authored 64 publications receiving 3584 citations. Previous affiliations of Karl-Arne Stokkan include University of Texas System & University of Texas Health Science Center at San Antonio.
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Journal ArticleDOI
Entrainment of the Circadian Clock in the Liver by Feeding
TL;DR: It is demonstrated that feeding cycles can entrain the liver independently of the SCN and the light cycle, and the need to reexamine the mammalian circadian hierarchy is suggested, raising the possibility that peripheral circadian oscillators like those in the liver may be coupled to theSCN primarily through rhythmic behavior, such as feeding.
Journal ArticleDOI
Circadian organization in reindeer
Bob van Oort,Nicholas J. C. Tyler,Menno P. Gerkema,Lars P. Folkow,Arnoldus Schytte Blix,Karl-Arne Stokkan +5 more
TL;DR: The continuous lighting conditions of summer and of winter at high latitudes cause a loss in daily rhythmic activity in reindeer living far above the Arctic Circle, suggesting that this seasonal absence of circadian rhythmicity may be a ubiquitous trait among resident polar vertebrates.
Journal ArticleDOI
A Circadian Clock Is Not Required in an Arctic Mammal
TL;DR: It is shown that the melatonin rhythm of reindeer (Rangifer tarandus) is acutely responsive to the light/dark cycle but not to circadian phase, and also that two key clock genes monitored in reindeers fibroblast cells display little, if any, circadian rhythmicity.
Journal ArticleDOI
Marked rapid alterations in nocturnal pineal serotonin metabolism in mice and rats exposed to weak intermittent magnetic fields
TL;DR: The results indicate that the metabolism of serotonin in the pineal is quickly affected by the exposure of animals to a magnetic field.
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Where clocks are redundant: weak circadian mechanisms in reindeer living under polar photic conditions
TL;DR: The combination of a weak photic response, weak circadian mechanisms and a weak social synchronization reduces the constraints of biological timing in an environment which is effectively non-rhythmic most of the year and permits expression of the basic ultradian pattern of ruminant activity.