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The chick pineal gland exhibits circadian rhythms in melatonin synthesis under in vivo and in vitro conditions. A daily rhythm of melatonin production was first detectable in pineal glands isolated from chick embryos at embryonic day 16 and incubated under a LD cycle. All pineal glands isolated from 17-day-old and older embryos were rhythmic while no gland(More)
In this study, we investigated whether there was a diurnal difference in mitogen-activated protein kinase (p42/44(MAPK)) phosphorylation in the rat pineal gland. Under a lighting regimen with 12h of darkness, there was a two- to four-fold increase in phosphorylated levels of MAPK kinase 1/2 (MEK1/2) and p42/44(MAPK) 2h after onset of darkness, an increase(More)
Development of a daily rhythmicity in transcription of a gene encoding a rate-limiting enzyme of melatonin biosynthesis, the arylalkylamine-N-acetyltransferase (AA-NAT) was studied by northern blot analysis in pineal glands of 16 and 19-day-old embryos and 1, 4, 8, 11, and 14-day-old chicks. In a parallel experiment, melatonin content in pineal glands and(More)
The pineal cells of chick embryos incubated in vitro exhibited a daily rhythm of melatonin synthesis under a 12:12 light:dark (LD) cycle at the embryonic days 16 and 19. In order to elucidate whether cyclic adenosine monophosphate (cAMP)--a component of the melatonin generating system--is already at work in the embryonic period, we measured the effects of(More)
The levels of histamine (HA) and tele-methylhistamine (t-MeHA) in chick pineal gland were measured by RIA at two time points, i.e. at the end of the light (L) phase and in the middle of the dark (D) phase of 12 h: 12 h L:D cycle. The chick pineal gland showed high HA levels (12.19 and 13.09 ng/pineal at L and D, respectively). The t-MeHA content of chick(More)
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