Chick pineal serotonin acetyltransferase: a diurnal cycle maintained <i>in vitro</i> and its regulation by light

Wainwright, S. D.; Wainwright, Lillian K.

doi:10.1139/o79-088

Cited by 59 publications

(24 citation statements)

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“…the circadian rhythm of the enzyme activity is driven by a clock systemthe suprachiasmatic nuclei of the hypothalamus -which is entrained by the photoperiod via the eyes [3,35,42]. In con trast, the chick and lizard pineal organs contain a more or less self-sustained oscillator involved in the control of NAT and melatonin circadian rhythmicities [I, 2,38,49]. Al though behavioral studies in fish [34] indicate that the pi neal organ acts on other components of the circadian sys tem, it is still unknown whether it contains or not a circa dian oscillator driving the indolic output.…”

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Rhythmic Melatonin Biosynthesis in a Photoreceptive Pineal Organ: A Study in the Pike

et al. 1987

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Activities of pineal N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase, involved in the biosynthesis of melatonin from serotonin, were assessed over 24 h in the pineal organ of pikes (Esox lucius, L.; teleosts) entrained to natural (winter) environmental conditions. Only NAT activity exhibited daily changes, rising at the onset of darkness and resuming low values shortly before the end of the scotophase. The rhythm was damped under constant darkness, lower and higher values being shifted towards intermediate ones. NAT activity was lowered under constant light; however, a significant increase was seen at the end of the subjective night, suggesting the existence of a low-amplitude rhythm. Illumination of the pikes at the middle of the scotophase induced inactivation of roughly half of the maximal NAT activity, possibly indicating the existence of one photolabile and one photostable enzymatic component. Under natural conditions, radioassayable melatonin of the pike pineal organ displayed daily variations which paralleled those of NAT activity. Melatonin production thus appears to reflect the daily changes of NAT, synchronized to the light/dark cycle.

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Rhythmic Melatonin Biosynthesis in a Photoreceptive Pineal Organ: A Study in the Pike

et al. 1987

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“…Isolated avian pineal glands also produce melatonin rhythmically in vitro, although their rhythms have not yet been tested for temperature compensation (13)(14)(15)(16). Our initial experiments with avian pineals in culture were stimulated by the results of a long series of behavioral experiments with the locomotor rhythms of house sparrows that strongly indicated that the pineal contained circadian oscillators (17)(18)(19).…”

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Temperature-compensated circadian clock in the pineal of Anolis.

Menaker¹,

Wisner²

1983

Proc. Natl. Acad. Sci. U.S.A.

148

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The pineal organ of the lizard Anolis carolinensis can be maintained for up to 10 days in superfused organ culture. During this time it synthesizes and releases melatonin into the medium flowing slowly over it. Collection of timed aliquots of medium and subsequent analysis for melatonin by radioimmunoassay reveal circadian rhythms of melatonin output by the isolated pineal. These rhythms persist for many cycles in constant darkness and at several constant ambient temperatures ranging from 22 to 370C. The period of the rhythm is temperature compensated (QIo 1.14) and the rhythm is synchronized by light-dark cycles imposed on the cultured gland. This isolated vertebrate organ displays the three major properties of circadian systems and must therefore contain one or more circadian oscillators.

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“…Four laboratories have documented an increase and decrease in N-acetyltransferase activity in isolated pineals for at least 24 hr in organ culture (15)(16)(17)(18)(19).…”

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Circadian rhythms of melatonin release from individual superfused chicken pineal glands in vitro.

Takahashi

Hamm

Menaker

1980

Proc. Natl. Acad. Sci. U.S.A.

222

104

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The pineal gland of birds contains one or more circadian oscillators that play a major role in overall temporal organization. We have developed a flow-through culture system for the isolated pineal by which we can measure the release of melatonin continuously from suerrfused glands over long pr riods of time. Chicken pineals release melatonin rhythmically, and these rhythms persist in vitro with a circadian oscillation. In light cycles the release of melatonin is strongly rhythmic; however, in constant conditions the amplitude of the rhythm is lower and appears to be damping. Light has at least two effects upon the isolated pineal: cyclic light input synchronizes the rhythm, and acute light exposure at ni ht rapidly inhibits melatonin release. The Behavioral and biochemical experiments strongly suggest that the avian pineal gland contains, or is, a circadian oscillator that plays a major role in the overall temporal organization of the animal (for review, see ref. 1). Removal of the pineal eliminates the free-running circadian rhythms of locomotor activity and body temperature in the house sparrow (2, 3). Transplantation of pineal tissue into the anterior chamber of the eye rapidly restores rhythmicity in arrhythmic pinealectomized sparrows and transfers the phase of the donor's rhythm to the host (4-6). These results argue that the pineal gland functions as a pacemaker within the circadian system of the house sparrow.Apart from the pineal's role in controlling behavioral rhythms, the biochemistry of the avian pineal itself is dramatically rhythmic. The melatonin content of chicken pineals oscillates in a circadian fashion (7,8) and contributes to a rhythm of melatonin in the serum (9). The synthesis of melatonin in the chicken pineal appears to be regulated by the activity of the enzyme serotonin N-acetyltransferase (7), which oscillates with a circadian period in vivo (10). The regulation of the rhythm of pineal N-acetyltransferase-which in rats is under the control of norepinephrine from the sympathetic fibers that innervate the pineal (11-13)-appears to be different in birds (14). Although it is not clear how the oscillation in N-acetyltransferase activity in the avian pineal is generated, it is consistent with the data to conclude that the controlling mechanism is within rather than external to the pineal.Recent experiments have established several important properties that are expressed by the isolated pineal gland in organ culture. Four laboratories have documented an increase and decrease in N-acetyltransferase activity in isolated pineals for at least 24 hr in organ culture (15)(16)(17)(18)(19).Kasal et al. (17) have shown that the rhythm persists for two cycles in constant darkness with a circadian period in vitro. However, the difficulty in measuring rhythms in populations MATERIALS AND METHODS Chemicals. Carrier-free, high-specific-activity 125I was purchased from Amersham. Melatonin was purchased from Sigma. Normal rabbit gamma globulin was purchased from Cappel Laboratories (Cochranville...

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Chick pineal serotonin acetyltransferase: a diurnal cycle maintained in vitro and its regulation by light

Cited by 59 publications

References 0 publications

Rhythmic Melatonin Biosynthesis in a Photoreceptive Pineal Organ: A Study in the Pike

Rhythmic Melatonin Biosynthesis in a Photoreceptive Pineal Organ: A Study in the Pike

Temperature-compensated circadian clock in the pineal of Anolis.

Circadian rhythms of melatonin release from individual superfused chicken pineal glands in vitro.

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