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At least 163 records · Page 9Linked to original sources

PubMed1978

Effects of the environmental light conditions on the ultrastructure of the harderian gland in the newborn rat. biochemical correlation with the pineal gland.

Morphological changes at the levels of both light and electron microscopy were studied regarding the secretory elements of the Harderian glands of neonatal rats, induced by environmental lighting conditions. The results were correlated with biochemical determinations of serotonin levels and hydroxyindole-O-methyl transferase (HIOMT) activity in the pineal gland. Neonatal male albino rats were divided into three groups: 12 were exposed to a light period for seven days; 12 to a dark period, and 12 to diurnal lighting conditions (light, 12 hours; darkness, 12 hours), as controls. In each group some animals were killed at 1.00 pm. The Harderian gland of each animal was immediately fixed and processed for light and electron microscopy while the pineal gland was homogenized in a fixative for biochemical determination of serotonin levels and HIOMT activity. On the light period the acinar lumen was observed to be dilated with increased secretions from the acini and excretory ducts while on the dark period the acinar lumen narrowed with hardly any secretions. On the dark period there were no changes in the cyclic variations of serotonin levels and HIOMT activity in the pineal gland; while on the light period, these cycles disappeared. It is concluded that secretory activity of the Harderian gland is modified by environmental lighting conditions, and that secretions produced by this gland appear to be directly related to the control mechanism of melatonin production by the pineal gland in neonatal rats.

Animals↗

PubMed1998

Ontogeny of a diurnal rhythm in arylalkylamine-N-acetyltransferase mRNA in rat pineal gland.

Melatonin synthesis in the pineal gland of adult rats is linked to cAMP-dependent transcriptional and post-transcriptional regulatory mechanisms affecting its rate-limiting enzyme, the arylalkylamine-N-acetyltransferase (AA-NAT). During development of the pineal gland, neuronal control gains access to the earlier matured cAMP-signaling pathway to shape the day-night rhythm in AA-NAT enzymatic activity. By semiquantitative in situ hybridization we analyzed if the developmental onset of a rhythmic AA-NAT activity is correlated to a temporally parallel onset in AA-NAT transcription. We found that AA-NAT mRNA levels in rat pineal gland become rhythmic at postnatal day 5. Thus, AA-NAT gene transcription in rat pineal gland starts to show day-night differences shortly prior to the appearance of a rhythmic AA-NAT activity.

Animals↗

PubMed2004

Melanopsin expression in the chick retina and pineal gland.

The chick retina and pineal gland exhibit circadian oscillations in biochemical and physiological processes in vivo and in vitro and entrain to 24 h LD cycles. However, the phototransductive mechanisms responsible for entrainment are largely unknown. Experiments utilizing mice lacking functional rods and cones reveal normal circadian responses to light. These studies also implicate a subset of photoresponsive cells in the ganglion cell layer (GCL) which express melanopsin (opn4). The current study investigates opn4 mRNA distribution and regulation in the chick. Opn4 mRNA is widespread in the central nervous system and peripheral tissues, with highest levels of transcript abundance in the pineal gland and retina. Opn4 mRNA is also regulated on a circadian basis in the pineal gland, reaching peak values of accumulation in the late subjective night. In the retina, opn4 is not robustly regulated at the transcriptional level, exhibiting a slight increase in mRNA abundance during subjective night. In situ hybridization (ISH) revealed opn4 mRNA in areas associated with phototransduction and the visual system, including the pineal gland and optic tectum of the brain, along with GCL, inner nuclear layer (INL), and photoreceptor layer (PL) of the retina. Opn4 is also present in cerebellum. Our results present an opsin-like gene located in two circadian oscillators associated with circadian phototransduction and melatonin biosynthesis that may play a role in entrainment of these tissues' clocks.

Animals↗

PubMed1976

[Allometry and linear correlation coefficients binding the volumes of the different pituitary gland lobes, of the pituitary gland, of the subfornical organ and of the pineal gland to body weight and to hypothalamic volume in Rodents and in a Lagomorphe].

The morphometric study of the hypophysis, of the subfornical organ and of the pineal gland of 41 Rodents and one Lagomorphe shows that the anterior lobe of the hypophysis as well as the total hypophysis are better correlated to body weight than to the volume of the hypothalamus, while it is the contrary for the pars nervosa. The volume of the intermediate lobe varies very much from one species to another for the same body weight. The high value of the allometry coefficient of the pineal gland on somatic weight (1.25) is due to the fact that the heavy Rodents of our temperate climates have a large epiphysis while the small african Rodents possess a small pineal gland.

Animals↗

PubMed1993

Effect of iron and estrogen on melatonin secretion by the chicken pineal gland.

Estrogen effects on pineal secretion of melatonin are controversial. Some feel that estrogen inhibits melatonin output in vitro but not in vivo. Melatonin levels vary with the age in chickens where circulating estrogen levels also vary. Laying hens have minimal melatonin levels and maximal serum iron concentrations. Thus, we reasoned that iron released by estrogen may inhibit melatonin secretion from the chick pineal gland. The present study shows that perifusion of estrogen-treated chick pineal glands with several concentrations of iron greatly inhibited melatonin secretion.

Animals↗

PubMed1992

Beta-adrenergic and peptide N-terminal histidine and C-terminal isoleucine stimulation of N-acetyl-transferase activity and melatonin production in the cultured rat pineal gland.

The purpose of this investigation was to compare the effect of peptide N-terminal histidine and C-terminal isoleucine (PHI) with that of the beta-adrenergic agonist isoproterenol (ISO) on N-acetyltransferase (NAT) activity and melatonin production in the cultured rat pineal gland. Pineal glands were removed and placed in organ culture containing PHI, ISO, or PHI plus ISO at different dosages, and subsequent changes in NAT activity and melatonin levels were measured. PHI stimulated these parameters in both a time- and dose-dependent manner. Combined treatment with PHI (10(-6) M) and high doses of ISO (either 10(-7) or 10(-8) M) did not potentiate the effect of the peptide in terms of either NAT activity or melatonin levels in the pineal gland. However, at a lower concentration, ISO (10(-9) M) had additive effects to those of PHI in both cultured pineals and medium. The results suggest that PHI modulates melatonin synthesis in the rat pineal gland. Furthermore, stimulation of the pineal with both PHI and ISO demonstrates an additive effect rather than a synergistic action of these compounds. It is presumed that ISO and PHI stimulate pineal melatonin production via separate receptors, but they probably use the same intracellular second messenger, cAMP, to do so. This is the first study showing an effect of the peptide PHI on pineal melatonin production in any vertebrate.

Acetyltransferases↗

PubMed1990

Molecular, enzymatic and functional properties of rhodopsin kinase from rat pineal gland.

Rhodopsin kinase activity from rat pineal gland and from rat retina are indistinguishable, based upon determination of a variety of enzymatic and molecular properties. Both activities are independent of calcium, cyclic nucleotides, and calmodulin. Both are activated by spermine and inhibited by adenosine and some rhodopsin kinase specific adenosine derivatives such as sangivamycin. The Km's for rhodopsin, ATP, and GTP are indistinguishable for the protein kinase in extracts from the retina and from the pineal gland. The apparent molecular weight of the kinase from both sources, as determined by gel filtration and autoradiography of the 32P-labeled autophosphorylated kinase, is about 70 kDa. Rhodopsin kinase activity from pineal binds in a light-dependent manner to rhodopsin in rod outer segments as does the enzyme from retina. Monoclonal antibodies against bovine rhodopsin were used in an immunochemical study that identified a rhodopsin-immunoreactive protein in rat pineal gland and retina. Using an ELISA we demonstrated the presence of a rhodopsin-immunoreactive protein in rat pineal gland equivalent to 0.075 pmol rhodopsin per gland. Frog pineal organ (Rana catesbiana) contains 33 times more of this rhodopsin-like protein than does rat pineal gland.

Animals↗

PubMed1996

[The effect of light with various wavelengths and impulse times on nocturnal suppression of N'acetyltransferase activation by serotonin in the pineal gland of the chick].

PURPOSE: Chick pineal gland synthesise melatonin in circadian rhythm, with peak values in the dark phase of an imposed light-dark illumination cycle. Light is the most important environmental factor regulating the melatonin-generating system in this gland. Exposure to light causes a dramatic decline of the night-time levels of the melatoninergic parameters. Effect of white and monochromatic lights of various wavelength on the night-time pineal gland serotonin N-acetyltransferase (NAT) activity were examined in chicks. MATERIAL AND METHODS: Male chicks (white leghorn: 3-4-week old) were used. They were purchased on the day of hatching. All animals were offered ad libitum access to standard food and water, maintained under an ambient temperature of 27 +/- 2 degrees C (chick), 60 +/- 5% humidity, and exposed to 12 hr light: dark illumination cycle for a minimum of 8-10 days before experiments. The daytime light intensity at the surface of the animals' cages was about 150 luxes. Each experiment was done at least twice. At the beginning of the fourth hour of the dark phase of the light-dark illumination cycle groups of chicks (four animals/group) were exposed to either white or monochromatic light for 5, 10, 30 or 60 min, and then killed by decapitation. In another set of experiment birds were illuminated for 5 min, returned to darkness for additional 5, 15, 60 or 120 min, and then decapitated. Decapitation was done quickly under dim red light (2 lux). Pineal glands were isolated and frozen on dry ice. The exposure of an animal to light took place in 25 x 21 cm white plastic chamber. Light produced by 5 W 14 bulbs (Osram) was passed through a cotton filter or filtered with glass, narrow band interference filters, 7 nm half-peak band-width. The spectral wavelength analysis for each interference filter was performed with the aid of Diode-Spectrophotometer, and the irradiance of the light of the three used wavelengths was measured with YSI Radiometer. The estimated peak wavelengths (Imax) of the filters were: 434 nm (blue), 548 nm (green) and 614 nm (red). The NAT activity was determined in supernatants of tissue homogenates with the radioisotopic method of Steinlechner with modifications by Nowak. RESULTS: Significant decrease of the night-time NAT activity of the chick pineal gland was observed after a 5-min pulse of either white or green light. In birds illuminated by blue light a marked reduction (by about 22%) in the pineal NAT activity was found after 10-min exposure, whereas in the group of animals that were exposed to red light a significant decline of the enzyme activity in pineal gland was produced by a 30-min pulse. The enzyme activity started to increase after 15 min in the dark and reached the control values by 1 hr (red light) or 2 hrs (blue and green lights). Two hrs and 5 min after the exposure to white light (5 min light and 120 min dark) pineal NAT activity was still significantly lower (by 16%) than the activity found in the dark control group. CONCLUSION: Suppressive effect of monochromatic (but not white) light on NAT activity was completely reversible in the pineal gland of chick.

Animals↗

PubMed2000

Gap junctions in the chicken pineal gland.

The chicken pineal gland, which contains a heterogeneous cell population, sustains a circadian rhythm of activity. Synchronization of cellular activity of heterogeneous cells might be facilitated by gap junctional intercellular channels which are permeable to ions and second messengers. To test this possibility, we looked for morphologically identifiable gap junctions between the different pineal cells, used antibodies and cDNA probes to screen for the presence of connexins, and tested for functional intercellular coupling. By transmission electron microscopy and immunocytochemistry, gap junctions and connexins were observed between pinealocyte cell bodies, stromal cells, astrocytes, and astrocyte and pinealocyte processes. Two gap junctional proteins, connexin43 and connexin45, were detected by immunocytochemistry, immunoblotting and RNA blot analysis. Functional intercellular coupling was observed in the gland by transfer of low molecular weight dyes. Dye transferred between homologous and heterologous cells. These data suggest that homologous and heterologous gap junctions may provide a mechanism for coordination of the cellular responses of the elements of the biological clock which are induced by lighting cues to produce the circadian rhythm of pineal activity.

Animals↗

PubMed1991

Tryptophan hydroxylase synthesis is induced by 3',5'-cyclic adenosine monophosphate during circadian rhythm in the rat pineal gland.

Tryptophan hydroxylase in the rat pineal gland undergoes diurnal rhythmic activity. Rat pineal glands exhibit increased tryptophan hydroxylase activity when incubated with a cyclic AMP analogue in vitro. Cyclic AMP-dependent protein kinase phosphorylates tryptophan hydroxylase, purified from rat brain, without any modification of its enzyme activity under our experimental conditions. Actinomycin D or cycloheximide decreases the stimulating effect of the cyclic AMP analogue on pineal tryptophan hydroxylase activity. Incubation of pineal glands in the presence of [35S]methionine showed a cyclic AMP-induced increase in tryptophan hydroxylase synthesis. These results explain the circadian rhythm of tryptophan hydroxylase activity in the rat pineal gland and suggest that the regulation of tryptophan hydroxylase expression by cyclic AMP occurs probably either at the translational level or via transient expression of a transcriptional regulatory element.

Animals↗

PubMed1983

Glial fibrillary acidic (GFA) protein-containing cells in the human pineal gland.

The development of human pineal astrocytes was studied in a prospective autopsy series of 115 cases with an age range of 24 weeks of gestation to 91 years. Pineal glands selected from cases with postmortem intervals of one to 24 hours were fixed in Bouin's fluid and immunostained using the peroxidase-antiperoxidase technique and an antiserum against human glial fibrillary acidic (GFA) protein. In adults, scattered, mostly angular and strongly-positive cells and processes were present. A few primary processes emanated from each astrocyte which abruptly subdivided into several secondary ones, creating a pervasive interstitial network of fibers which surrounded almost every individual pinealocyte. Astrocytic endfeet formed a limiting lamina at the periphery of the gland and a barrier between perivascular spaces and the pineal parenchyma. At 24 weeks of gestation, occasional punctate staining, mainly around vessels, was present in the pineal body, while in the surrounding white matter there was already pronounced astrocytic differentiation. Around 32 weeks of gestation, well-formed astrocytes and a weakly staining network of their processes appeared in differentiated areas of the pineal gland. Both astrocytes and their interstitial network of processes became more prominent with advancing age. There was no astrocytic hypertrophy or hyperplasia around calcified deposits. Rosenthal fibers stained negatively for GFA protein. These findings emphasize the significance of the astrocytic participation in the structure of the human pineal gland throughout life.

Adolescent↗

PubMed1989

Metastases to pineal gland.

Metastases to the pineal gland is an uncommon event. Bronchogenic carcinomas are the most frequent source of the primary lesion. A case of small cell carcinoma of the lung with solitary metastases to the pineal gland is reported; the literature is reviewed.

Brain Neoplasms↗

PubMed1984

The number and distribution of sympathetic neurons that innervate the rat pineal gland.

The sympathetic innervation of the rat pineal gland was examined using a variety of anatomical techniques. Following the injection of horseradish peroxidase into the pineal gland, approximately 250 labeled neurons were found in the ipsilateral superior cervical ganglion. No labeled neurons were found in the middle or inferior cervical ganglia. In animals whose left internal carotid nerve was lesioned prior to the injection of peroxidase, an average of only three labeled neurons was found in the ipsilateral superior cervical ganglion. These data suggest that most, if not all, of the sympathetic neurons innervating the pineal gland exit from the superior cervical ganglia via the internal carotid nerves. The distribution of sympathetic neurons innervating the pineal gland was similar, though slightly more rostrally placed, than the distribution of the entire population of superior cervical ganglion neurons which project into the internal carotid nerve. Both the small number of neurons innervating the pineal gland and their wide distribution in the rostral part of the superior cervical ganglion indicate that their study at the level of the ganglion would be difficult. Sympathetic axons reach the pineal gland via the nervi conarii. Electron microscopic studies indicate that in each nervus conarii there are about 440 axons which make contact with the surface of the pineal gland. In certain cases, bundles of axons from the left and right nervi conarii were found to fuse. Additional evidence for the intermingling of axons from the two nervi conarii was seen in orthograde transport studies with horseradish peroxidase.

Animals↗

PubMed2000

Glutamate receptor subunit delta2 is highly expressed in a novel population of glial-like cells in rat pineal glands in culture.

The mammalian pineal gland uses L-glutamate as an intercellular chemical transmitter to regulate negatively melatonin synthesis. To receive glutamate signals, pinealocytes express at least three kinds of glutamate receptors: metabotropic receptor types 3 and 5 and an ionotropic receptor, GluR1. In this study, we examined whether or not the fourth class of ionotropic receptor, delta, which is known for its nondefinitive molecular function and its unique expression pattern in brain, is expressed in pineal gland. RT-PCR analyses with specific probes indicated the expression of mRNA of delta2 but not that of delta1 in pineal gland and cultured pineal cells. Western blotting analysis with polyclonal antibodies specific to the carboxyl-terminal region of the delta2 receptor recognized a single 110-kDa polypeptide of cerebellar membranes and specifically immunostained Purkinje cells. The delta2 antibodies recognized a 110-kDa polypeptide of pineal membranes and specifically immunostained huge glial-like cells with the occasional presence of several long, branching processes in a pineal cell culture. delta2 is not uniformly distributed throughout the cells and is relatively abundant at the periphery of the cell bodies and long processes, where the terminals of synaptophysin-positive processes of pinealocytes, a site for glutamate secretion, are frequently present. The delta2-positive cells constitute a very minor population among total pineal cells (approximately 0.03%). Double immunolabeling with delta2 antibodies and antibodies against marker proteins for pineal interstitial cells clearly distinguishes delta2-positive pineal cells and other known interstitial cells, including glial fibrillary acidic protein- or vimentin-positive glial-like cells. These results indicated that the delta2 glutamate receptor is expressed in a novel subpopulation of pineal glial-like cells in culture and suggest the presence of a glutamate-mediated intercellular signal transduction mechanism between pinealocytes and delta2-expressing cells. The pineal cells may provide a good experimental system for studies on the function of glutamate receptor delta2.

Amino Acid Sequence↗

PubMed1981

The pineal gland of the mole (Talpa europaea L.). VII. Activity of hydroxyindole-O-methyltransferase (HIOMT) in the formation of 5-methoxytryptophan, 5-methoxytryptamine, 5-methoxyindole-3-acetic acid, 5-methoxytryptophol and melantonin in the eyes and the pineal gland.

Using a method in which no substrate is added to the incubation medium, the capacity of HIOMT to synthesize 5-methoxytryptophan, 5-methoxytryptamine, 5-methoxyindole-3-acetic acid, 5-methoxytryptophol and melatonin has been determined in the pineal and the eyes of the mole, a mammal having an atrophied visual system. The results demonstrate that the indoleamine metabolism in the retina is similar to the indoleamine metabolism in the pineal. Moreover, in all animals studied both eyes together synthesize 2 to 30 times more of 5-methoxyindoles than the pineal, a result which proves again that the pineal is not the only and not always the most important source of 5-methoxyindoles. With the exception of 5-methoxyindole-3-acetic acid, the synthesis of which is practically neglectable, the production of all other 5-methoxyindoles in the pineal as well as in the retinae is always larger than that of melatonin. In the pineal, 5-methoxytryptophan, for example, is synthesized in a quantity which is 60 to 170 times larger than that of melatonin, while in the retinae the synthesized amount of 5-methoxytryptophan is even 60 to 1000 times larger than that of melatonin.

5-Methoxytryptamine↗

PubMed1995

Cholinergic signaling in the rat pineal gland.

1. Innervation of the mammalian pineal gland is mainly sympathetic. Pineal synthesis of melatonin and its levels in the circulation are thought to be under strict adrenergic control of serotonin N-acetyltransferase (NAT). In addition, several putative pineal neurotransmitters modulate melatonin synthesis and secretion. 2. In this review, we summarize what is currently known on the pineal cholinergic system. Cholinergic signaling in the rat pineal gland is suggested based on the localization of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), as well as muscarinic and nicotinic ACh binding sites in the gland. 3. A functional role of ACh may be regulation of pineal synaptic ribbon numbers and modulation of melatonin secretion, events possibly mediated by phosphoinositide (PI) hydrolysis and activation of protein kinase C via muscarinic ACh receptors (mAChRs). 4. We also present previously unpublished data obtained using primary cultures of rat pinealocytes in an attempt to get more direct information on the effects of cholinergic stimulus on pinealocyte melatonin secretion. These studies revealed that the cholinergic effects on melatonin release are restricted mainly to intact pineal glands since they were not readily detected in primary pinealocyte cultures.

Acetylcholinesterase↗

PubMed1980

Evidence for a thyrotropin-releasing hormone inhibitor in the pineal gland.

Extracts of bovine pineal glands were filtered through Sephadex G-25 and tested for their effect on TRH-induced TSH release in cell cultures of dispersed rat pituitary glands. Highly significant anti-TRH activity was found in material which was retarded on G-25. This material was purified sequentially on Sephadex G-10, Sephadex LH-20, and high pressure reverse phase liquid chromatography columns. The ability of partially purified material to inhibit TRH-induced TSH release by dispersed pituitary cells and to displace [3H]TRH from pituitary tumor cell membranes was interpreted as evidence for a TRH inhibitory factor (TRH-IF) in bovine pineal glands. Evidence for binding to TRH receptors included parallel competition displacement curves with synthetic TRH and data showing that excess TRH could overcome both the inhibition of TRH-induced TSH release and the inhibition of [3H]TRH binding by TRH-IF. Copurification of anti-TRH bioactivity (as tested in dispersed pituitary cell cultures) and anti-TRH-binding activity (as tested in membrane preparations) suggests that the inhibitory activity in pineal extracts results from the binding of a TRH antagonist to receptors. Reports by others of PRL release-inhibiting activity in pineal extracts were confirmed. PRL release-inhibiting activity copurified with TRH-IF.

Animals↗

PubMed1989

Psychoactive drugs, pineal gland and affective disorders.

The possibility of pineal gland involvement as a part of "neuroendocrine dysfunction" in some of the psychiatric diseases has received special attention in recent years. The discovery of a cascade of receptors and the action of many psychoactive drugs on pineal gland supports the concept that the pineal gland can be considered as a suitable model system for assessing the action of psychotropic drugs. Psychotropic drugs, particularly antidepressants both tricyclics and monoamine oxidase inhibitors when administered either to animals or to patients suffering from depressive illness affects the pineal gland function and melatonin concentration. This raises the possibility that the beneficial effects of these drugs may relate to their ability to alter the pineal gland function and melatonin secretion. The occurrence of seasonal affective disorders and their response to bright light treatment implicate, melatonin as a "bio-chemical marker" for these disease states. In view of these facts it can be suggested that pineal gland does play an important role in the etiology of mental diseases, especially affective disorders.

Animals↗