Showing papers on "Pinealocyte published in 1986"

Pinealocyte projections into the mammalian brain revealed with S-antigen antiserum.

Abstract: Neural processes from mammalian pinealocytes have been discovered in several brain areas. These processes were visualized immunocytochemically in the Djungarian hamster, Phodopus sungorus, with an antiserum against bovine retinal S-antigen and traced as far as the region of the posterior commissure and habenular nuclei. This result indicates that pineal-to-brain connections exist in the mammal, and that the mammalian pineal gland, currently thought of only as a neuroendocrine organ, may communicate directly with select brain regions by way of these projections. The existence of mammalian pinealocyte projections is consistent with the view that these cells are not of glial origin but are derivatives of photoreceptor cells of the pineal complex of lower vertebrates that transmit signals to the brain by neural projections.

Interphotoreceptor retinoid-binding protein in retinal rod cells and pineal gland.

Abstract: Immunoelectron microscopic staining demonstrates Interphotoreceptor Retinoid-Binding Protein (IRBP) in monkey rod cell cytoplasm with virtually none in cone cells. The pineal also contains significant amounts of IRBP demonstrating a similarity of pinealocytes to rod but not cone photoreceptors.

Neural pathways and neurotransmitters affecting melatonin synthesis.

Abstract: In addition to its sympathetic innervation, a mammalian pineal gland also receives a distinct central pinealopetal innervation. Earlier studies in rat have established that the photic signals originating in the retina pass via the retinohypothalamic tract to the suprachiasmatic nucleus, to the tuberal hypothalamus, over medial forebrain bundle, reticular formation, and upper thoracic interomediolateral cell column to the superior cervical ganglion, whose postganglionic sympathetic fibers, traveling along the tentorium cerebelli, enter the pineal gland via the conarian nerve. Recent electron microscopic analyses of the pineal gland of several mammalian species have revealed intrapineal nerve terminals different from the sympathetic ones. In addition, lesion experiments performed in the habenular nuclei or the posterior commissure support the central origin of these terminals. The intact sympathetic innervation, the functional beta-adrenergic receptors, and the appropriate level of norepinephrine are all essential prerequisites for the circadian pattern of melatonin synthesis. However, other receptors such as alpha-adrenergic, D2-dopaminergic, GABAergic, benzodiazepinergic, and glutamatergic receptors and their agonists are also able to modulate the synthesis of melatonin, and this function depicts dramatic species variation. The impact of pinealopetal projections and intrapineal neurons on the physiological and biochemical aspects of pineal functions awaits clarification.

S-antigen-like immunoreactivity in a human pineocytoma.

Abstract: A pineocytoma was investigated by means of immunocytochemistry with the use of a polyclonal antibody against bovine retinal S-antigen. Several cells of this tumor displayed strong S-antigen-like immunoreaction in analogy to certain pinealocytes in normal human pineal organs. This study indicates that S-antigen immunocytochemistry may be applied to characterize tumors of the pineal region.

Cell types in the pineal gland of the horse: an ultrastructural and immunocytochemical study.

Abstract: A combined ultrastructural and immunocytochemical study was performed on the pineal gland of the horse in order to identify the cell types present and describe their characteristics. Comparisons have been made with other mammals. Two main cell types are present: pinealocytes and glial cells. Pinealocytes display different degrees of electron density in the nucleus and the cytoplasm, yet no ultrastructural feature supports the idea of separate populations. Putative secretory materials are stored in vesicles related to the Golgi apparatus. A variety of electron-dense bodies are present in the cytoplasm. Interstitial cells responding to anti-GFAP (glial fibrillary acid protein) and anti-vimentin antibodies, but not to anti-neuronal 200-kD protein antibodies, are located close to the perivascular spaces and connective septa. Morphological and immunocytochemical features support classifying them as astrocytes, probably protoplasmic. The presence of a cavity lined with pericytes, putatively a remnant of the embryonic lumen of the organ, is a consistent finding and may relate to the third ventricle.

Fine-structural study of the pineal body of the monkey (Macaca fuscata) with special reference to synaptic formations

Abstract: Various types of synaptic formations on pinealocytes and pineal neurons were found in the pineal body of Macaca fuscata Axo-somatic synapses of the Gray type-II category were detected on the pinealocyte cell body Gap junctions and ribbon synapses were observed between adjacent pinealocytes About 70 nerve-cell bodies were detected in one half of the whole pineal body bisected midsagittally They were localized exclusively deep in the central part When examined electron-microscopically, they were found to receive ribbon-synapse-like contacts from pinealocytic processes They also received synaptic contacts of the Gray type-I category on their dendrites, and those of the Gray type-II category on their cell bodies from nerve terminals of unknown origin All these synapse-forming axon terminals contained small clear vesicles Thus, the pineal neurons of the monkey, at least in part, are suggested to be derived from the pineal ganglion cells in the lower vertebrates and not from the postganglionic parasympathetic neurons The functional significance of these observations is discussed in relation to the innervation of the pineal body of the monkey

Pineal calcification: its mechanism and significance.

Abstract: On the basis of conventional transmission electron microscopy and ultracytochemical reactions for demonstration of calcium, for glucose-6-phosphatase, and for Ca2+-ATPase, intracellular and extracellular mineralization foci in the superficial pineal gland of the Mongolian gerbil (Meriones unguiculatus) have been described. The initial intracellular calcification sites occur in the cytoplasmic matrix, vacuoles, mitochondria and the endoplasmic reticulum of large clear pinealocytes. These loci, and particularly those within the cytoplasmic matrix, transform into acervuli by a further addition of hydroxyapatite crystals. The cells gradually degenerate, die, break down, and the acervuli reach the extracellular space. It has been suggested that the reason for a rise in intracellular calcium levels could be the incapacity of Ca2+-ATPase to eliminate this cation from the cell, so that the hypercalcemic intracellular milieu becomes favourable for the initial crystallization. The primary extracellular mineralization sites occur in the calcium-rich flocculent material. The mineralization process in the gerbil pineal gland is interpreted as a histophysiological phenomenon intimately related to the metabolic activity of the pineal gland.

Synaptic ribbon populations in the pineal gland of the rhesus monkey (Macaca mulatta).

Abstract: Pinealocytes of rhesus monkeys that had been ovariectomized and given intramuscular injections of 250 μg estradiol-benzoate for 3 consecutive days tended to have more synaptic ribbons (SR) and exhibited a significantly greater size of ribbon fields (RF) compared to untreated animals. These data are consistent with hypotheses that pinealocyte function in primates is altered by hormonal imbalances and that the SR participates in this response. RF were positioned in various parts of the cytoplasm and along the plasma membrane. Participation of SR in direct cell-to-cell contacts was suggested by the formation of densities along the plasma membrane. It is postulated that large RF serve as storage organelles and that the formation of RF results from division of pre-existing SR in each field. Reconstructions made from serial thin sections revealed that profiles of RF comprised separate SR that were not folded and sectioned along various planes.

Demonstration of differential immunohistochemical localization of the neuron-specific enolase antigen in rat pinealocytes.

Abstract: A refined method for the immunohistological demonstration of neuron-specific enolase (NSE) on 1- to 2-micron Epon-812 section gave characteristic staining of cerebral and cerebellar neurons. This method has made it possible to obtain a more detailed characterization of the heterogeneity of rat pinealocytes in the superficial portion of the rat pineal complex. Thirty adult male rats have been studied, five of which were used in a photometric analysis of the distribution of NSE. Pinealocytes stained either intensely or weakly for the NSE antigen and exhibited an uneven distribution within a given region. Further analysis of the gland revealed a distal to proximal decrease in stain intensity. It is suggested that the more strongly stained cells, being concentrated distally, are under sympathetic control.

Inverse behaviour of synaptic ribbon and spherule numbers in the pineal gland of male guinea-pigs exposed to continuous illumination

Abstract: There is increasing evidence that pineal “synaptic” ribbons are a heterogeneous population of organelles. In addition to “synaptic” ribbons (SR) sensu stricto, which consist of an electron-dense rod surrounded by electronlucent vesicles, “synaptic” spherules (SS) exist, the electrondense core of which is round and much wider than that of the SR. In the guinea-pig SR and SS numbers exhibit an inverse day/night rhythmicity. To gain more insight into the functional significance of SR and SS, guinea-pigs were exposed to continuous illumination for approximately 4 months (LL) and the respective structures in the pineal gland were quantitated under the electron microscope and compared with control animals kept under a lighting regiment of 12 h light and 12 h dark. It was found that SR numbers increase following LL whereas SS numbers decrease. The proximal, intermediate and distal parts of the dumbbell-shaped organ respond differently. The increase in SR numbers is significant in the distal and intermediate regions only, whereas the decrease in SS numbers is significant in the proximal and the intermediate regions only. Within each pineal region analyses of parenchymal subareas measuring 65 μm by 65 μm exhibit an inverse correlation of SR and SS numbers indicating that there are parenchymal domains in which either SR or SS predominate. Morphometric analyses of a number of pinealocytic parameters reveal minor differences between different pineal regions and that exposure to LL does not strikingly affect the pinealocyte perikarya. By contrast, the numbers of pinealocyte processes increase significantly after LL in the distal and intermediate, but not the proximal region of the pineal gland. These observations suggest structural and functional differences between different parts of the guinea-pig pineal gland.

Different types of pinealocytes as revealed by immunoelectron microscopy of anti-S-antigen and antiopsin binding sites in the pineal organ of toad, frog, hedgehog and bat.

Abstract: S-antigen- and opsin-immunoreactive sites were studied in the pineal organ of toad (Bufo bufo), frog (Rana tigrina), hedgehog (Erinaceus roumanicus) and bat (Myotis myotis) by light microscopic avidin-biotin-peroxidase and electron microscopic immunoglobulin-gold (immunogold), protein A-gold and avidin-biotin-ferritin techniques. The corresponding retinas served as reference tissues. A large number of photoreceptors of toad and frog pineal organ exhibited either strong or weak S-antigen immunoreaction in the outer segments, perikarya and basal processes. A small number of photoreceptors was S-antigen-negative. In general, the intensity of the reaction was stronger in the immunoreactive outer segments of the pineal organ than in those of the rods and certain cones of the retina. In hedgehog and bat, the perikarya and processes of the pinealocytes were either strongly or weakly S-antigen-positive or they lacked immunogold labeling. By use of an antibovine rhodopsin antiserum either strong or weak opsin immunoreactivity was found in the pineal outer segments of toad and frog. A small number of pineal photoreceptors lacked opsin antigenic sites. Double labeling with both antibovine S-antigen and antibovine opsin antisera showed that the opsin immunoreaction was present in the outer segments which also exhibited S-antigen immunoreaction. In the pineal organ of hedgehog and bat, no opsin immunoreaction was observed with the antisera used. It is proposed that in the pineal organ at least two types of photoreceptors are present: one "rod-type" elaborating rhodopsin accompanied by S-antigen and one (or two) "cone-type(s)" using an unknown photopigment(s). Obviously, the different photoreceptors enable the animal to perceive the different wavelengths of the light spectrum.

Estradiol modulation of pineal gland activity in the wild bandicoot rat, Bandicota bengalensis

Abstract: In the present study, the effect of estradiol dipropionate on the cytology and mitotic activity of the pineal gland was evaluated in adult ovariectomized and juvenile bandicoot rats, Bandicota bengalensis. Estradiol treatment for 5 days inhibited the ovariectomy-induced hypertrophy of the pineal gland, and increased the nuclear diameters of pinealocytes in juvenile males while having no effect on the pineal cytology of juvenile females. Estradiol injection induced mitosis in the pinealocytes of adult ovariectomized and juvenile bandicoot rats. Thus, estradiol exhibited a dual action (stimulatory and inhibitory) on the pineal gland of this wild rat.

Multipotentiality in differentiation of the pineal as revealed by cell culture.

Abstract: Publisher Summary The pineal complex of lower vertebrates is a photoreceptive organ known as the “median eye” that furnishes function and morphology comparable with two lateral eyes. In the course of phylogenic development, the pineal changes its major function from photoreceptive to endocrine. A number of pinealogists have suggested repeatedly that photoreceptive cells in the pineal of lower vertebrates are the direct ancestors of endocrine pinealocytes of higher vertebrates. It has been well demonstrated that nonlenticular cells of vertebrate eyes can convert their cell types, or transdifferentiate, into lens in cell culture conditions. This chapter, therefore, examines whether pineals of higher vertebrates still retain the potency to differentiate into their ancestral phenotypes, into lens and various other ocular cells, when cultured in vitro . Recent results along this line indicate that pineals of higher vertebrates are provided with an unexpectedly wide repertoire of differentiation. This system may not only offer another interesting example of transdifferentiation, but also provides a unique opportunity to analyze the nature of an exogenous cue by which multipotent cells can select a given pathway of differentiation. The chapter also reviews studies on the multiplicity of differentiation of pineals.

Ultrastructural demonstration of secretion by exocytosis in rat pinealocytes with the use of the tannic acid method.

Abstract: In the rat pineal gland the mechanism of release of secretory material was studied ultrastructurally after incubating tissues in Ringer solution containing tannic acid. The results indicate that pinealocytes release the contents of secretory vesicles into the extracellular space via exocytosis, a phenomenon that has not been visualized previously in this cell type. This finding may reflect release of polypeptides by the pineal gland.

Influence of photoperiod on dense-core vesicles and synaptic ribbons of pinealocytes of the djungarian hamster (Phodopus sungorus).

Abstract: The ultrastructure of the superficial part of the pineal gland ofPbodopus sungorus was examined. Dense-core vesicles and synaptic ribbons in pinealocytes of animals kept under different photoperiods were counted, revealing marked differences. Pinealocytes of short-day animals compared with long-day animals exhibit an increase of dense-core vesicles coincident with a decrease of synaptic ribbons. It is assumed that the corresponding numerical changes of these organelles are of functional significance in relation to pineal secretory activity.

Nucleolus-like bodies in the pineal gland of the Djungarian hamster ( Phodopus sungorus )

Abstract: Light- and electron-microscopic observations on the pineal gland of Phodopus sungorus revealed intracytoplasmic inclusions resembling nucleolus-like bodies similar to those found in other regions of the central nervous system. Bernhard's EDTA method was used to confirm that these inclusions were nucleolus-like bodies. These structures were rarely found in pinealocytes of sexually active longday animals, whereas large numbers of them were observed in pinealocytes of sexually quiescent short-day animals. Nucleolus-like bodies may therefore be involved in pineal secretion.

Ultracytochemical evidence for the presence of GERL in pinealocytes of the Mongolian gerbil ( Meriones unguiculatus )

Abstract: Ultracytochemical reactions for the demonstration of acid phosphatase, glucose-6-phosphatase and thiamine pyrophosphatase, as well as zinc iodide-osmium tetroxide impregnation, revealed the existence of GERL (Golgi apparatus — Endoplasmic Reticulum — Lysosomes) in pinealocytes of the Mongolian gerbil (Meriones unguiculatus). The spatial arrangement of this structure was studied on thick sections using a goniometric stage. Although it was not possible to determine whether GERL in pinealocytes belongs to the Golgi apparatus or to endoplasmic reticulum, it can be concluded that its presence in studied cells signifies that they are considerably more active synthetically than has been believed to date.

Characteristic pattern of monoaminergic nerve fibers in the pineal organ of the monkey, Macaca fuscata

Abstract: Monoaminergic nerve fibers were studied in the pineal organ of the monkey, Macaca fuscata, by use of fluorescence and immunohistochemical procedures. Abundant formations of noradrenergic nerve fibers were observed in the pineal organ. They entered the parenchyma in the form of several coarse bundles via the capsule in the distal portion of the organ and spread throughout the organ after branching into smaller units. The density of the autonomic innervation decreased gradually toward the proximal portion of the organ. In the distal portion, numerous nerve fibers formed perivascular plexuses around the blood vessels and some fibers ran as bundles unrelated to the blood vessels in the stroma. Fine varicose fibers and bundles derived from these plexuses penetrated among the pinealocytes. However, only a few intraparenchymal fluorescent fibers were detected in the proximal third of the gland. With the use of serotonin antiserum serotonin-immunoreactive nerve fibers were clearly restricted to the ventroproximal part of the pineal organ. Although the somata of the pinealocytes showed intense immunoreactivity, their processes were not stained. In one exceptional case, clusters of pinealocytes displaying very intense immunoreactivity were found in an area extending from the distal margin of the ventral portion of the pineal stalk to the proximal portion of the pineal organ proper; these cells were bipolar or multipolar and endowed with well-stained processes.

Effects of Long and Short Photoperiod on the Ultrastructure of Pinealocytes of the Cotton Rat (Sigmodon hispidus)

Abstract: The ultrastructure of the pinealocytes of wild-captured cotton rats (Sigmodon hispidus) housed in either long or short photoperiod was examined. Quantitative comparison of selected pinealocyte organelles revealed larger relative volumes of mitochondria, granular endoplasmic reticulum and ribosomes, Golgi apparatus, and inclusion bodies, as well as a higher number of dense-core vesicles in the animals kept in short photoperiod (LD 8:16) as compared to those in animals kept in long photoperiod (LD 16:8). These observations suggest that restricting the amount of light to which animals are exposed activates pinealocytes of the cotton rat.

Effect of continuous darkness on circadian morphological rhythms in pinealocytes of the Chinese hamster, Cricetulus griseus.

Abstract: Effects of a short-term exposure to continuous darkness on 24-h morphological variations in pinealocytes in the superficial pineal of the Chinese hamster (Cricetulus griseus) were examined. Pinealocytes contained type-1, -2 and -3 synaptic ribbons (SR), which had a central dense structure showing rod-like, various and ring-like profiles, respectively, and the quantity of each type of SR was expressed by SR index. 24-h changes in the type-1 and type-3 SR indices persisted in darkness and thus may be endogenous in nature. As under alternating light and dark (LD) conditions, the type-2 SR indices were almost constant over a 24-h period under continuous darkness, but the indices were larger in animals under darkness than in those under LD conditions. The 24-h variations in the nuclear and cytoplasmic volumes were abolished after exposing animals to darkness for 7 days, suggesting that these rhythms may be regulated exogenously. The amount of condensed chromatin exhibited a circadian change; this rhythm persisted under darkness. The results suggest that 24-h variations in the nuclear and cytoplasmic volumes in pinealocytes of the Chinese hamster are regulated by mechanisms different from those controlling the rhythms in SR and chromatin, and that the changes in the nuclear and cytoplasmic volumes and chromatin are related to the change in synthetic activity of pinealocytes.

Effects of Pineal Factors on the Action Potentials of Sympathetic Neurons

Abstract: 1. Neurons from rat superior cervical ganglia were grown in coculture with pineal cells. Action potentials of neurons in cocultures were 25% longer and were 25% greater in amplitude than those recorded from neurons grown in the presence of ganglionic nonneuronal cells alone. 2. Neurons showed an increase in action potential duration with increasing time in culture. This may have been related to the recovery of nonneuronal cell populations after an initial exposure to the antimitotic agent Ara-C. In cultures not initially exposed to Ara-C, a subsequent exposure after 7 days in culture resulted in a shortening of the action-potential duration. 3. Neuronal cultures were exposed to gel slabs containing the pineal indolamines, serotonin,N-acetylserotonin, and melatonin. Serotonin andN-acetylserotonin showed no effect on the neuronal action potentials at the concentrations tested. 4. Melatonin caused an increase in action-potential duration that was associated not with an increase in action-potential amplitude, but with a decrease in actionpotential rise rates. The effects of long-term exposure in melatonin appeared to be reversible in some cells but not in all. 5. Short-term effects of melatonin were observed in older cultures and in younger cultures after the cells were stimulated repeatedly. Older cultures also had higher levels of spontaneous activity. The dependence of the short-term effects of melatonin on electrical activity may suggest a role for melatonin as a neuromodulator.

Ultrastructural studies on the mitochondria of the pinealocyte under conditions of persistent lighting--L24.

Abstract: Rat pinealocytes were found to contain mitochondria in three configurational states and they were calculated at 11.00 a.m. and 11.00 p.m. Their proportions were found to change in 24 hours. Analysis of these results indicated the existence of correlation between pinealocyte bioenergetics and melatonin biosynthesis and its lack in relation to serotonin. Cell groupings with mitochondria in the same configurational state were observed, which suggest the existence of functionally differentiated zones within the pineal gland.