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At least 37 records · Page 2Linked to original sources
PubMed1994

Seasonal variations in the daily rhythm of melatonin and NAT activity in the Harderian gland, retina, pineal gland, and serum of the green frog, Rana esculenta.

Day-night variations of melatonin content and N-acetyltransferase (NAT) activity were studied in the Harderian gland (HG), retina, pineal gland, and serum of the green frog Rana esculenta. Throughout the year the retinal melatonin content was correlated with retinal NAT activity and was always higher than those in the pineal gland and HG. On the other hand, in these structures diurnal fluctuations in NAT activity were observed. There were clear seasonal differences in the magnitude of the nocturnal increase of retinal melatonin levels as well as in the nocturnal pattern of retinal NAT activity. In summer day-night variations of melatonin and NAT are absent. The prevailing photoperiod seems to affect melatonin and NAT circadian rhythms in R. esculenta.

Animals↗
PubMed1981

Biosynthesis of biopterin: adrenergic cyclic adenosine monophosphate-dependent inhibition in the pineal gland.

Pineal glands in organ culture synthesize and release biopterin and are able to maintain concentrations of biopterin occurring in vivo for up to 54 hours in vitro. The intracellular biopterin content is reduced 50 percent by treatment with l-norepinephrine or cyclic adenosine monophosphate derivatives, but not by d-norepinephrine. This is an indication that biopterin levels are regulated by an adrenergic cyclic adenosine monophosphate-dependent mechanism. The decline in tissue biopterin content, produced mainly by inhibited of biosynthesis, is maximal at 6 hours and is not associated with either an increase in biopterin release or a shift in the reduction state of the biopterin.

1-Methyl-3-isobutylxanthine↗
PubMed1980

LHRH incorporation in normal and denervated pineal gland, and in pineal gland of rats with constant estrous-anovulatory syndrome: a preliminary study.

Pineal gland and superior sympathetic cervical ganglia accumulated intravenously injected 3H-LHRH in an amount significantly higher than anterior and posterior hypothalamus, cerebral cortex and pituitary gland, the latter a specific target for LHRH. The prior administration of unlabelled LHRH significantly decreased the 3H-LHRH incorporation only in pineal and pituitary gland. Autoradiography showed that the radiolabel was localized at the level of the pinealocytes, with a seemingly, prevalent distribution of grains on the cellular contours. Pineal incorporation of LHRH was not significantly modified by either acute or chronic bilateral cervical ganglionectomy, although acute ganglionectomy resulted in a slight decrease in LHRH accumulation by pineal gland. Constant estrous anovulatory syndromes induced by either frontal hypothalamic deafferentation, or continuous illumination, or neonatal androgenization did not appear to modify the LHRH incorporation in either pineal gland or cervical ganglia. On the basis of these results, pineal gland is supposed to be a target organ for LHRH.

Animals↗
PubMed1986

S-antigen immunoreactivity in human pineal glands and pineal parenchymal tumors. A monoclonal antibody study.

Using a four-step immunoperoxidase (PAP) method and the monoclonal antibody MAbA9-C6 (MAbA9-C6), which defines an epitope of the retinal S-antigen (S-Ag), we investigated the S-Ag immunoreactivity in human fetal, newborn, infantile and adult pineal glands and in 13 human pineal parenchymal tumors. S-Ag immunoreactivity was demonstrated in a few cells in one of the four fetal and in both infantile glands. Eight of nine adult pineal glands contained isolated MAbA9-C6-positive cells. In two of seven pineocytomas showing neuronal or gangliogliomatous differentiation a few scattered cells displayed S-Ag positivity; two of four pineoblastomas contained small groups of strongly immunoreactive neoplastic cells; two malignant pineocytomas did not demonstrate any S-Ag immunoreactivity. Our results indicate that isolated cells in human pineal gland retain some of the cytochemical characteristics of photoreceptor cells recognized by the MAbA9-C6, and that S-Ag immunoreactivity may be occasionally expressed in pineal parenchymal tumors.

Adult↗
PubMed1984

Day:night variations of melatonin, 5-hydroxyindole acetic acid, serotonin, serotonin N-acetyltransferase, tryptophan, norepinephrine and dopamine in the rabbit pineal gland.

Pineal tryptophan, serotonin, serotonin-N-acetyltransferase (NAT), melatonin, 5-hydroxyindole acetic acid (5HIAA), norepinephrine and dopamine were measured in 5 castrated rabbits each at 11.00, 00.30 and 03.00 hours. The rabbits were housed in an L:D 14:10 (lights on 07.00 hours). Significant day:night variations were found in NAT, melatonin, dopamine and norepinephrine. These results were compared to data concerning rhythms of pineal constituents in other species.

Acetyltransferases↗
PubMed1985

Phase shift of daily profiles of N-acetyltransferase in the rat pineal gland.

Pineal N-acetyltransferase activity (NAT) has a circadian rhythm with peak values in the dark time and low values in the light time. NAT time profiles were measured in rats exposed to LD 14:10, to constant dark, and to acute (less than 48 hr) light-dark treatments. In all experiments, imposition of light suppressed NAT. The phase of the dark time NAT cycle was altered 2 hr or less by the following treatments: 3 hr light in the early subjective night, 3 hr light in the late subjective night, 2 hr or 6 hr light in the early subjective day, 4 hr early lights-on, 1 day of constant dark, or 1 day of constant light. When light was extended 4 hr into the dark time, NAT rose at lights out but fell again as the time of "expected" dawn approached. In contrast, the phase of the NAT cycle was shifted 12 hr (180 degrees) within 72 hr by reversing the phase of the light-dark cycle. NAT did not rise in the first dark period (coincident with the time of the subjective light time). The amplitude of the first shifted cycle was less than four control NAT profiles measured in rats kept in the original (unshifted) light-dark cycle.

Acetyltransferases↗
PubMed2003

Transcription factors may frame Aa-nat gene expression and melatonin synthesis at night in the Syrian hamster pineal gland.

Pineal melatonin synthesis is stimulated at night following an increase in arylalkylamine-N-acetyltransferase (AA-NAT) activity. Depending on the species, two mechanisms of enzyme activation have been described: a cAMP/phospho-cAMP response element-binding protein-dependent stimulation of Aa-nat gene transcription in the rat, presumed to occur in all rodents, or a posttranslational regulation of AA-NAT protein in ongulates. The present data obtained in the Syrian hamster indicate another route of AA-NAT regulation. Elevated nocturnal levels of Aa-nat mRNA were strongly suppressed following light exposure or adrenergic antagonist administration, demonstrating the involvement of norepinephrine in the stimulation of melatonin synthesis. However, administration of adrenergic agonists during the day did not increase Aa-nat mRNA unless a protein synthesis inhibitor was given during the previous night. This indicates that an inhibitory protein, synthesized at night, prevents melatonin synthesis during the day. By contrast, a protein synthesis inhibitor given at the beginning of the night markedly reduced Aa-nat mRNA, suggesting that a stimulatory protein (transcription factor?) is necessary for Aa-nat gene transcription at night. Noteworthy, hamsters raised in long photoperiod were responsive to adrenergic agonist injection only in the first hour after light onset, a response that may be important in this photoperiodic species in which the melatonin peak extends into the morning hours in a short photoperiod.

Adrenergic alpha-Agonists↗
PubMed2002

Circadian clock system in the pineal gland.

The pineal gland is a neuroendocrine organ that functions as a central circadian oscillator in a variety of nonmammalian vertebrates. In many cases, the pineal gland retains photic input and endocrinal-output pathways both linked tightly to the oscillator. This contrasts well with the mammalian pineal gland equipped only with the output of melatonin production that is subject to neuronal regulation by central circadian oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Molecular studies on animal clock genes were performed first in Drosophila and later developed in rodents. More recently, clock genes such as Per, Cry, Clock, and Bmal have been found in a variety of vertebrate clock structures including the avian pineal gland. The profiles of the temporal change of the clock gene expression in the avian pineal gland are more similar to those in the mammalian SCN rather than to those in the mammalian pineal gland. Avian pineal gland and mammalian SCN seem to share a fundamental molecular framework of the clock oscillator composed of a transcription/translation-based autoregulatory feedback loop. The circadian time-keeping mechanism also requires several post-translational events, such as protein translocation and degradation processes, in which protein phosphorylation plays a very important role for the stable 24-h cycling of the oscillator and/or the photic-input pathway for entrainment of the clock.

Animals↗
PubMed1997

Diurnal change of arachidonate 12-lipoxygenase in rat pineal gland.

Rat pineal gland contains a 12-lipoxygenase as demonstrated by the enzyme activity, RNA blot analysis and in situ hybridization. Using rats maintained with 12-h dark and light cycles, dynamic changes of the enzyme in pineal gland were examined. When the crude extract of pineal glands was incubated with arachidonic acid and the reaction products were analyzed by reverse-phase HPLC, the glands obtained from rats in the dark showed a higher 12-lipoxygenase activity than those obtained from rats in the light. The pineal 12-lipoxygenase activity decreased after the light was on at 7 o'clock and reached the lowest level around 16 o'clock. Upon Western blot analysis the amount of 12-lipoxygenase protein in pineal glands was high in the dark and lowest around 16 o'clock. A half life of the enzyme protein was estimated to be approximately 2.8 h in organ culture of rat pineal glands. Northern blot analysis also revealed a higher 12-lipoxygenase mRNA level in pineal glands obtained in the dark than those obtained in the light. Thus, the 12-lipoxygenase of rat pineal glands shows a diurnal fluctuation that is regulated at the transcription level, and may play a certain role in the regulation of neuroendocrine processes of this gland.

Animals↗
PubMed1981

Decapeptide luteinizing hormone releasing hormone in ovine pineal gland.

Ovine pineal gland extracts were examined throughout the year for content and molecular form of immunoreactive (IMR) LH releasing hormone (LH-RH). The content of IMR LH-RH in pineal glands collected in spring and summer was 160-2230 pg/gland, while the content in pineal glands collected in autumn and winter was lower (31-39 pg/gland). Pineal gland IMR LH-RH, purified by affinity and Sephadex G-25 chromatography, yielded displacement curves parallel to those of hypothalamic IMR LH-RH and synthetic LH-RH in radioimmunoassays employing four antisera which require different regions of the decapeptide for effective binding, suggesting considerable similarities in the structure of the molecule. The majority of pineal gland IMR LH-RH behaved identically to hypothalamic IMR LH-RH and synthetic LH-RH on gel filtration, cation exchange chromatography, high-pressure liquid chromatography and cellulose thin-layer chromatography. However, a small amount of a less positively charged LH-RH species was also present in all pineal gland extracts. Our findings indicate that hypothalamic decapeptide LH-RH occurs in the ovine pineal gland.

Animals↗
PubMed2003

Demonstration of nerve fibers immunoreactive to peptide N-terminal histidine C-terminal isoleucine (PHI) and vasoactive intestinal peptide (VIP) in the pig pineal gland.

The pineal functions are modulated by some neuropeptides including PHI and VIP. The presence of PHI-immunoreactive and VIP-immunoreactive nerve fibers in the pineal gland has been shown in several mammalian species. Both peptides influence the pineal serotonin N-acetyltransferase activity and melatonin synthesis. The aim of the present study was to examine the localization of PHI- and VIP-immunoreactive nerve fibers in the pig pineal gland. Four three-month old female pigs housed in natural light conditions, with free access to food and water, were used in the study. The pineals were fixed by perfusion with 4% paraformaldehyde in 0.1 M phosphate buffer. An immunohistochemical ABC streptavidin-biotin-complex method was used for the demonstration of PHI and VIP. PHI- and VIP-immunopositive nerve fibers were found in the pineal gland as well as in the habenular and posterior commissural areas. In the pineal gland, the density of PHI-immunoreactive nerve fibers was considerably higher than that of the fibers containing VIP. PHI- and VIP-immunopositive nerve fibers were more abundant in the cortical than in the medullary part of the gland. The nerve fibers formed bundles in the pineal capsule, from where they penetrated to the connective tissue septa and formed a dense meshwork surrounding blood vessels. In the parenchyma, PHI- and VIP-immunoreactive nerve terminals created baskets around clusters of pinealocytes. No PHI- or VIP-immunopositive cells were found in the pig pineal gland.

Animals↗
PubMed2006

Spectral sensitivity of melatonin suppression in the zebrafish pineal gland.

The pineal gland of the zebrafish (Danio rerio) is a clock-containing photoreceptive organ. Superfused pineal glands kept in darkness display rhythmic melatonin production that lasts for days, with high melatonin levels during the night and low levels during the day. Nocturnal light, however, evokes an acute suppression of melatonin synthesis in the photoreceptor cells. Towards characterizing zebrafish pineal photopigment that is involved in the acute melatonin suppression we have measured the spectral sensitivity of melatonin-suppression response in superfused pineal glands. The effect of 2 h light exposure of seven wavelengths (lambdaavg 408, 460, 512, 560, 608, 660 and 697+/-10-15 nm) at multiple irradiances (10(7)-10(14) photons/cm2/s) was determined, and an action spectrum was plotted. The resultant action spectrum provides evidence for the involvement of multiple photopigments in melatonin suppression. The most efficient melatonin-suppression response was achieved by exposure to light of around 512 nm; however, another peak of lower irradiance sensitivity was observed in the middle to long wavelengths. Opsins-specific RT-PCR analysis confirmed the expression of exo-rhodopsin and visual red-sensitive opsin in the pineal gland, while other zebrafish visual opsins as well as VA and VAL opsins were not detected. Dartnall monograms for exo-rhodopsin and visual red-sensitive opsin account for most but not all of the spectral sensitivity features. Therefore, additional pineal photopigments may contribute to the melatonin-suppression response in the pineal gland.

Animals↗
PubMed2006

The avian pineal gland.

The pineal gland plays a key role in the control of the daily and seasonal rhythms in most vertebrate species. In mammals, rhythmic melatonin (MT) release from the pineal gland is controlled by the suprachiasmatic nucleus via the sympathetic nervous system. In most non-mammalian species, including birds, the pineal gland contains a self-sustained circadian oscillator and several input channels to synchronize the clock, including direct light sensitivity. Avian pineal glands maintain rhythmic activity for days under in vitro conditions. Several physical (light, temperature, and magnetic field) and biochemical (Vasoactive intestinal polypeptide (VIP), norepinephrine, PACAP, etc.) input channels, influencing release of melatonin are also functional in vitro, rendering the explanted avian pineal an excellent model to study the circadian biological clock. Using a perifusion system, we here report that the phase of the circadian melatonin rhythm of the explanted chicken pineal gland can be entrained easily to photoperiods whose length approximates 24 h, even if the light period is extremely short, i.e., 3L:21D. When the length of the photoperiod significantly differs from 24 h, the endogenous MT rhythm becomes distorted and does not follow the light-dark cycle. When explanted chicken pineal fragments were exposed to various drugs targeting specific components of intracellular signal transduction cascades, only those affecting the cAMP-protein kinase-A system modified the MT release temporarily without phase-shifting the rhythm in MT release. The potential role of cGMP remains to be investigated.

Animals↗
PubMed2000

The pineal gland.

The pineal gland is located posterior to the midbrain and is the site of melatonin production. Research on pineal gland function in neonates is very limited. This article will discuss pineal gland development and the possible relationship between melatonin production and sudden infant death syndrome. Further research on pineal gland function is needed in order to establish its significance for the neonate.

Female↗
PubMed2004

[Advances in study on molecular mechanism of circadian clock in pineal gland].

The pineal gland functions as a central circadian oscillator in a variety of nonmammalian vertebrates. More recently, clock genes such as Per, Cry, Clock, and Bmal have been found in a variety of vertebrate clock structures including the avian pineal gland. The profiles of the temporal change of the clock gene expression in the avian pineal gland are more similar to those in the mammalian suprachiasmatic nucleus (SCN) of the hypothalamus. Avian pineal gland and mammalian SCN seem to share a fundamental molecular framework of the clock oscillator composed of a transcription/translation-based autoregulatory feedback loop. Some products of the clock genes serve as positive or negative regulators influencing the clock oscillation. The circadian time-keeping mechanism is also involved in several post-translational events. The above-mentioned processes play a quite important role in the stability of the oscillator and/or the photic-input pathway for entrainment of the clock.

Animals↗