bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunohistochemical Assessment of Melatonin Binding in the Pineal Gland
Authors: Holloway W. R. , Grota L. J. , Brown G. M. 
Published: February 2007

Melatonin binding in the pineal gland of albino rats is estimated using an immunohistochemical procedure. Binding is saturable, has relatively high affinity (Apparent KD= 2.7 nM), and competition studies indicate binding of indoleamines possessing an N‐acetyl group on the terminus of the side chain (N‐acetylserotonin and melatonin). These data are consistent with the interpretation that immunohistochemically determined melatonin in unfixed pineal tissue is assessing binding of N‐acetylated indolealkylamines to pineal cell components.In albino rats maintained on 12‐hour light: 12‐hour dark cycles, melatonin binding exhibits a diurnal rhythm with low levels of saturation (30%) early in the light and saturation by endogenous melatonin near the onset of darkness. An annual rhythm of melatonin binding was observed in albino rats with low levels during the summer and high levels during the winter. Other rats were maintained on 12‐hour light: dark cycles and fed for 2 hours either early in the light period or early in the dark period. For both morning‐ and evening‐fed animals, melatonin binding was high prior to feeding and dropped immediately after feeding. Changes in melatonin binding that occur in response to alterations of feeding and time of year suggest the possibility that this binding reflects a functional site for melatonin.
Distribution in the Macaque Pineal of Nerve Fibers Containing Immunoreactive Substance P, Vasopressin, Oxytocin, and Neurophysins
Authors: Ronnekleiv Oline K. 
Published: February 2007

The distribution of nerve fibers containing immunoreactive substance P (SP), estrogen‐stimulated neurophysin (ESN), nicotine‐stimulated neurophysin (NSN), oxytocin (OT), and vasopressin (VP) was examined in the epithalamic area of adult male and female macaques. Perfused or immersion‐fixed epithalamic tissues, sectioned, and mounted on glass slides were processed through the avidin–biotin immunofluorescence method.Fibers containing immunoreactive SP were observed in the pineal organ along the periphery, in the perivascular space, and dispersed between the pinealocytes. Fibers were often observed in the pineal stalk region, and the habenular nuclei had high concentration of immunoreactive SP. Immunoreactive ESN fibers were observed in the stria medullaris, in the lateral habenula, in the pineal stalk, and in the pineal organ. Within the pineal, fibers containing ESN were present in the perivascular space, often concentrated in the walls of blood vessels, but also dispersed between pineal cells. Fibers containing OT, NSN, and VP were also present in the macaque pineal, but in lower quantities compared with fibers containing ESN.These studies show that the pineal of subhuman primates contain nerve fibers (ESN, NSN, VP, OT) of possibly hypothalamic origin. It also has a rich supply of SP fibers, which might be of habenula origin, peripheral parasympathetic ganglia origin, or both. The functional significance of these peptidergic nerve fibers remains to be determined. However, there are indications that they might be involved in regulation of blood flow and release of secretory products from the pinealocytes.
Plasma, Cerebrospinal Fluid, and Brain Distribution of 14C‐Melatonin in Rat: A Biochemical and Autoradiographic Study
Authors: Vitte P. A. , Harthe C. , Lestage P. , Claustrat B. , Bobillier P. 
Published: February 2007

The distribution of 14C‐Melatonin (14C‐MT) after systemic injection was studied in the plasma, cerebrospinal fluid (CSF), and brain of rats. Chromatographic analysis (thin‐layer chromatography and high‐performance liquid chromatography) indicated that the radioactivity from biological samples taken at various times following the injection of label was mainly associated with 14C‐MT. Computer analysis of plasma 14C‐MT kinetics showed a three‐compartment system with half‐lives of 0.21 ± 0.05, 5.97 ± 1.11, and 47.52 ± 8.86 min. The volume of distribution and the clearance were 1,736 ± 349 ml. kg−1 and 25.1 ± 1.7 ml. min−1. kg−1 respectively. The entry of 14C‐MT into the CSF was rapid and reached a maximum at 5 min. The decay followed a two‐compartment system with half‐lives of 16.5 ± 2.9 and 47.3 ± 8.6 min. The CSF/plasma concentration ratio was 0.38 at the steady state (30 min). At 2 min the level of 14C‐MT in the brain was 3.8 higher than in the CSF. Representative autoradiograms revealed an heterogeneous localization of 14C‐MT in the grey matter. The highest regional values, as evaluated by the permeability area product technique, were found in cortex, thalamic nuclei, medial geniculate nucleus, anterior pretectal area, paraventricular nucleus of the hypothalamus, choroid plexuses, and bulb‐pons. Thirty minutes later 14C‐MT was still detected in most of the brain regions analyzed.These results point to a low but rapid penetration of circulating MT into the brain and the CSF. The heterogeneous distribution and the partial retention of 14C‐MT in the brain are compatible with the hypothesis of a central action of this hormone mediated via binding sites.
Thymidine kinase activity of the chick pineal gland
Authors: Wainwright Lillian K. , Wainwright S.D. 
Published: February 2007

Wainwright LK, Wainwright SD. Thymidine kinase activity of the chick pineal gland. J. Pineal Res. 1991:J Pineal Res 1991:10:71‐73.Abstract:Pineal thymidine kinase activity of 1‐week‐old chicks in situvaried significantly throughout the day. However, the circadian rhythm of thymidine incorporation seen with cultured chick pineal glands was not accompanied by variations in level of thymidine kinase activity in vitro. Thus the circadian rhythm in rate of cumulative incorporation of thymidine by cultured chick pineal glands is not determined by a rhythm in rate of the first reaction of the complex series of reactions by which thymidine is incorporated into DNA.
Pinealocyte subsurface cisterns II: Influence of time of day, sympathectomy, and castration
Authors: Heinzeller Thomas , Tutter IIse 
Published: February 2007

Heinzeller T, Tutter I. Pinealocyte subsurface cisterns 11: Influence of time of day, sympathectomy, and castration. J Pineal Res 199 1 : 10: 84‐90.Abstract:Subsurface cisterns (ssc) of the gerbil pinealocyte were studied by electron microscopic morphometry taking account of different external influences: time of day, sympathetic deafferentation, castration with or without substitution of testosterone. Male individuals of Meriones unguiculatus, aged 150 days, were used. Though ssc number is invariant with respect to the light‐dark cycle, ssc size follows a highly significant sinusoid curve. The largest ssc were found in the afternoon, the smallest ones in the early morning. Bilateral resection of the superior cervical ganglia reduces the density of pinealocyte ssc markedly, and their size is maximal or, in relation to the scaled‐down cell, unusually large. Castration with or without application of testosterone propionate does not alter pinealocyte ssc, neither with respect to density nor size. From these experimental data it is concluded that pinealocyte ssc may play a supportive role in the regulation of pinealocyte sensitivity, in so far as it depends on receptors located in the cell membrane.
Pinealocyte subsurface cisterns III: Storage of calcium ions and their probable role in cell stimulation
Authors: Tutter Use , Heinzeller Thomas , Seitz‐Tutter Dieter 
Published: February 2007

Tutter I, Heinzeller T, Seitz‐Tutter D. Pinealocyte subsurface cisterns 111: Storage of calcium ions and their probable role in cell stimulation. J Pineal Res 1991:10:91‐99.Abstract:Different techniques for the ultrastructural demonstration of calcium have been applied to the pineal gland of Meriones unguiculatus, attention being focussed on the endoplasmic reticulum (ER) and its subsurface cisterns (ssc). By means of a “loading” method [Walz, 1982; Wakasugi et al, 1982] it is shown that the pinealocyte ER‐ssc system sequesters calcium with dependency on ATP. Furthermore, a modification of the method of Duce and Keen [1978] is presented which turned out a) to be sensitive enough to demonstrate the cell's own low amounts of calcium as fine granular precipitates, and b) to preserve ultrastructure sufficiently. This method rendered possible comparison of the calcium distribution inside pinealocytes of the following groups: animals fixed during daytime, animals fixed at night, animals fixed at night with prior exposure to bright white light, animals fixed at night but injected at the end of the preceding light period with a pharmacon known to prevent the release of calcium from the ER of muscle fibers (Dantrolen). In contrast to the daytime findings, the pinealocyte ER‐ssc system at night is free of precipitable calcium; nocturnal illumination induces reacquisition, Dantrolen hinders nocturnal depletion. From the nocturnal coincidence of pinealocyte activity and calcium release from ssc, and from other cytological and experimental data, it is concluded that the functional significance of ssc refers to the regulation of pinealocyte sensitivity. Vice versa, pinealocyte activity may influence ER expansion and ssc size via the calcium‐dependent stability of microtubules.
Ultrastructure and opsin immunocytochemistry of the pineal complex of the larval Arctic charr Salvelinus alpinus: A comparison with the retina
Authors: Vigh‐Teichmann I. , Ali M.A. , Szél A. , Vigh B. 
Published: February 2007

Abstract: The fine structure and opsin immunocytochemistry of the pineal and parapineal organs of the salmonid fish Salvelinus alpinus, the landlocked Arctic charr, were studied and compared with the retina in various developmental stages, from prehatching to two‐month‐old. For opsin immunocytochemistry two polyclonal antibovine rhodopsin and the monoclonal antichicken opsin antibodies OS‐2 (detecting blue and green pigments) and OS‐1 (detecting green and red pigments) were used.Histologically, the pineal organ consists of nervous tissue like that of the retina. It is composed of photoreceptor pinealocytes, which formed axon terminals containing synaptic ribbons, on the dendrites and perikarya of secondary pineal neurons. Already in prehatching embryos, both the pineal and retinal photoreceptors display well‐developed outer segments and form synaptic terminals. The distal part of the pineal organ differentiates earlier than its proximal stalk. The differentiation of the retina starts centrally, but the caudal and dorsal retinae are differentiated earlier than the rostral and ventral ones. At the end of the larval period, the lateral retina is still undifferentiated.In all stages studied, (rhod)opsin immunoreactivity was found in the outer segments of the pineal organ and rod‐type retinal photoreceptors, a finding speaking in favour of the presence of the opsin of a rhodopsin/porphyropsin. Cone‐type retinal photoreceptors identified morphologically in the pre‐ and posthatching stages were opsinimmunonegative with the four primary antisera used. This result suggests that in the charr the opsins of cone visual pigments differ in their chemical nature from those of rhodopsin/porphyropsin. The parapineal organ was opsin immunonegative. Using the monoclonal antibody OS‐2 opsin immunoreactivity was also detected in inner segments, perikarya, and pedicles of rod‐type photoreceptors of both retina and pineal organ of embryos and 1‐ to 4‐day‐old larvae. This may indicate a high level of opsin gene expression during photoreceptor growth around hatching. The well‐developed pineal organ and its opsin content are discussed in connection with the photonegative behaviour of the larval charr.
Effects of melatonin and the melatonin receptor agonist S‐20098 on the vigilance states, EEG spectra, and cortical temperature in the rat
Authors: Tobler Irene , Jaggi Karin , Borbély Alexander A. 
Published: February 2007

Tobler I, Jaggi K, Borbély AA. Effects of melatonin and the melatonin receptor agonist S‐20098 on the vigilance states, EEG spectra, and cortical temperature in the rat. J. Pineal Res. 1994: 16: 26–32.AbstractThe effects of melatonin (3 mg/kg i.p.) and the melatonin receptor agonist S‐20098 (3 mg/kg i.p.) on the vigilance states, electroencephalogram power spectra (0.25–25.0 Hz), and cortical temperature were determined in eight rats in the first 6‐hr interval of the 12‐hr light period. Compared to the vehicle injection both compounds reduced the power density in non‐rapid eye movement sleep in the low frequency range (1–8 Hz) but did not affect the vigilance states and brain temperature. The present findings do not indicate that the stimulation of the melatonin receptor exerts a hypnotic effect at doses that had been shown to affect the circadian rest‐activity rhythm.
Characterization of high‐affinity melatonin binding sites in purified cell nuclei of rat liver
Authors: Acuña‐Castroviejo Dario , Reiter Russel J. , Menendez‐Pelaez Armando , Pablos Maria I. , Burgos Alejandro 
Published: February 2007

Acuna‐Costroviejo D, Reiter RJ, Menéndez‐Peláez A, Pablos MI, Burgos A. Characterization of high‐affinity melatonin binding sites in purified cell nuclei of rat liver. J. Pineal Res. 1994: 16: 100–112.AbstractHigh‐affinity 2‐125I‐iodomelatonin binding sites in homogenates of purified cell nuclei from rat liver were localized and characterized using biochemical binding techniques. Binding at these sites was found to be rapid, reversible, saturable, and to demonstrate pharmacological selectivity. At 0°C, binding reached equilibrium in about 10 min. Scatchard analysis of the data at equilibrium revealed a single class of binding sites with a dissociation constant of KD= 190 ± 47 pM, Bmax= 9. 8 ± 0. 6 fmol/mg protein, and a Hill coefficient of nH= 1. 02 ± 0. 034. Kinetic analysis of the association and dissociation curves indicated a kinetic KD= 148 ± 41 pM, which is in good agreement with the value obtained at equilibrium. The specific binding of 2‐125I‐iodomelatonin (45 pM) (0. 51 ± 0. 04 fmol/mg protein) was significantly improved (0. 79 ± 0. 04 fmol/mg protein) when the homogenates of purified liver cell nuclei were reinsulated with DNase (2 μg/ml at 37°C for 20 min) before being used in binding experiments. After the addition of either proteinase K or trichloroacetic acid to DNase‐treated purified cell nuclear homogenates, the specific binding disappeared. This suggests that the specific binding of 2‐125I‐iodomelatonin in liver cell nuclei is associated with nuclear protein. Competition experiments show that N‐acetyl‐serotonin (Ki= 81. 3 nM) was more potent than 5‐hydroxytryptamine (Ki > 1 μM) and 5‐methoxytryptamine (Ki≫ 10 μM) in inhibiting 2‐125I‐iodomelatonin binding (Ki melatonin = 146 pM). These data indicate that specific 2‐125I‐iodomelatonin binding sites exist in the cell nuclei of rat liver, and that they may comprise a locus for the intracellular action of melatonin. The correlation between the KD and Bmax values with melatonin concentrations in nuclei suggest that these binding sites may be a physiological melatonin receptor, which could explain the described genomic effects of the pineal hormone.
Effects of chronic melatonin administration on adrenal medulla catecholamine metabolism in adult male golden hamsters
Authors: Esquifino Ana I. , Moreno Maria L. , Steger Richard W. 
Published: February 2007

Esquifino AI, Moreno ML, Steger RW. Effects of chronic melatonin administration or adrenal medulla catecholamine metabolism in adult male golden hamsters. J. Pineal Res. 1994; 16: 154–158.AbstractThe role of melatonin on adrenal medullary function was evaluated in adult golden (Syrian) hamsters injected daily at either 0800 or 1600 with melatonin (25 μxg/hamster) or vehicle (0. 1% ethanol in saline). Sixty days after initiation of treatment and 16 or 24 hr after the last injection of melatonin, animals were killed by decapitation and blood and tissue collected. Plasma prolactin levels were reduced by chronic administration of melatonin only when animals were treated at 1600. Tyrosine hydroxylase (TH) activity in the adrenal medulla was not changed by either morning or afternoon administration of melatonin. Phenylethanolamine‐N‐methyl transferase (PNMT) was changed by afternoon administration of melatonin. Morning and afternoon melatonin injections led to the reduction of both adrenal monoamine oxidase (MAO) and catechol‐O‐methyl transferase (COMT) activities although the afternoon injections led to a greater magnitude of change. Norepinephrine and epinephrine contents were significantly reduced by morning melatonin administration but were not changed by afternoon administration of the hormone. These data suggest that melatonin has direct and possibly indirect effects on adrenal medullary function in the hamster. However, further studies will be required to characterize the effects of melatonin on catecholamine synthesis and release and the physiological significance of these effects.
Calcium, calcification, and melatonin biosynthesis in the human pineal gland: A postmortem study into age‐related factors
Authors: Schmid Hermann A. , Requintina Pura J. , Oxenkrug Gregory F. , Sturner William 
Published: February 2007

Schmid HA, Requintina PJ, Oxenkrug GF, Sturner W. Calcium, calcification, and melatonin biosynthesis in the human pineal gland: A postmortem study into age‐related factors. J. Pineal Res. 1994:16:178–183.AbstractIt is believed that pineal calcification may be age‐associated and that the well‐demonstrated age‐related decline in melatonin biosynthesis may be an expression of an alteration in calcium homeostasis in the pinealocyte. Prior correlations of melatonin to calcium deposition and age were made on the basis of radiological or semiquantitative analysis. In this postmortem study of 33 subjects (age range 3 months to 65 years) calcium deposits measured by atomic absorption spectrometry correlated positively with age in day and night samples (day: r = 0.56, P < 0.05; night: r = 0.818, P < 0.001). Nighttime (2200 h to 0800 h) pineal melatonin content (HPLC fluorometry) was higher than daytime melatonin levels (nighttime 3.80 ± 0.3 vs. daytime 0.85 ± 0.4 ng/mg protein). Nighttime calcium levels in the supernatant correlated negatively with melatonin content (r =−0.59, P < 0.05).
Elevation of cyclic GMP levels in the rat pineal gland induced by nitric oxide
Authors: Guerrero Juan M. , Reiter Russel J. , Poeggeler Burkhard , Chen Li‐Dun , Tan Dun‐Xian 
Published: February 2007

Guerrero JM, Reiter RJ, Poeggeler B, Chen L‐D, Tan D‐X. Elevation of cyclic GMP levels in the rat pineal gland induced by nitric oxide. J Pineal Res. 1994:16:210–214.AbstractThe present paper reports that nitric oxide (NO) released by sodium nitroprusside (SNP) is a potent activator of rat pineal cyclic GMP production without affecting cyclic AMP synthesis. Other drugs such as isoproterenol, vasoactive intestinal peptide, and peptide histidine isoleucine were ineffective in stimulating cyclic GMP production, but activated cyclic AMP production. However, L‐arginine, the physiological precursor of NO, did not activate either cyclic GMP or NO synthesis. Because L‐arginine failed to activate cyclic GMP production, results suggest that NO is not produced in the pineal gland, but behaves as a potent regulator of this cyclic nucleotide.
Identification and characterization of 2[125I]‐iodomelatonin binding sites in the rat epididymis
Authors: Yu Zong‐Han , Chow P. H. , Pang Shiu‐Fun 
Published: February 2007

Yu ZH, Chow PH, Pang S‐F. Identification and characterization of 2[125I]iodomelatonin binding sites in the rat epididymis. J. Pineal Res. 1994;17:195–201.AbstractPutative melatonin receptors in different parts of the male reproductive system of rats (Sprague‐Dawley), mice (ICR), hamsters (Syrian) and guinea pigs (Dunkin‐Hartley), rat epididymal sperm, and boar and human semen were studied by a radioreceptor assay using 2[125I]iodomelatonin as the radioligand. There was limited or no detectable binding of 2[l25I]iodomelatonin to membrane preparations of rat testis, seminal vesicles, prostate, or sperm from rat, human, and boar. However, significant bindings of 2[125I]iodomelatonin to the epididymides of rat, mouse, hamster, and guinea‐pig were demonstrated. The relative binding capacities of 2[125I]iodomelatonin to the distal epididymal segment in different rodent species was of the order rat mouse hamster guinea pig. The relative number of binding sites was much lower in the proximal segment than in the distal segment of epididymis. 2[125I]iodomelatonin binding to the distal segment of rat epididymis was studied in detail. The binding sites fulfilled all criteria for a receptor site; being stable, saturable, reversible, and of high affinity. The binding had an equilibrium dissociation constant (Kd) of 62.6 ± 7.79 pmol/1 (n = 7) and a density (Bmax) of 1.55 ± 0.16 fmol/mg protein (n = 7). The Hill coefficient approached 1. 0, suggesting a single class of 2[125I]iodomelatonin binding sites. Pharmacological studies revealed that these 2[125I]iodome‐latonin binding sites were specific for melatonin receptors. In addition, there was an age‐related change in the 2[125I]iodomelatonin binding sites in the rat distal epididymal segment. The binding increased from a lower value in 1‐month‐old rats to a higher adult value in the l1/i‐ to 24‐month‐old animals. The demonstration of 2[125I]iodomelatonin binding sites in the epididymis indicates the presence of melatonin receptors. A high binding level in the distal epididymal segment suggests the possible participation of melatonin in the process of sperm maturation.
Modulation of the subcellular distribution of calmodulin by melatonin in MDCK cells
Authors: Antón‐Tay Fernando , Martínez Isabel , Tovar Rosalinda , Benitez‐King Gloria 
Published: February 2007

Antón‐Tay F, Martínez I, Tovar R, Benítez‐King G. Modulation of the subcellular distribution of calmodulin by melatonin in MDCK cells. J. Pineal Res. 1998; 24:35–42. © Munksgaard, CopenhagenAbstractIn this paper we describe the interaction of melatonin with calmodulin in MDCK cells. The double staining immunofluorescent method showed that calmodulin in control MDCK cells appeared as fluorescent spots at the cell periphery. In contrast, MDCK cells cultured with 10‐‐9 M melatonin for 6, 12, 24 hr or for 4 days showed that calmodulin fluorescent spots were distributed throughout the cytoplasm as well as in the nucleus. These calmodulin rearrangements were reversed 6 hr after melatonin withdrawal. Moreover, calmodulin radioimmunoassay showed that in 10‐‐9 M melatonin‐treated cells, membrane‐bound calmodulin content was increased by 78% whereas cytosolic calmodulin decreased by 60%. Simultaneous labeling of MDCK cells with specific antibodies against calmodulin and melatonin showed that not only does the indole enter the cell, but that it has the same subcellular distribution as calmodulin. Besides the early responses induced by the melatonin antagonism to calmodulin, the results suggest that the indole may also induce long‐term cellular responses by changing calmodulin concentrations in specific cellular compartments.