Showing papers on "Pinealocyte published in 1990"
TL;DR: Comparison of the circadian variations in pineal adrenergic receptor numbers leads to the conclusion that the functional differences between rat and hamster pineal are probably not explicable in terms of the adrenergic receptors, but are caused most likely by (a) intracellular mechanism(s) beyond the Adrenergic receptors.
Abstract: Pineal adrenergic receptor numbers show circadian variations in both rat and Syrian hamster. In the rat pineal Β-adrenergic receptor density reaches peak values either late in the light phase or at middark; the differences in the circadian phase seem related to the light:dark cycle to which the animals are exposed. No circadian rhythm of pineal α-adrenergic receptors is documented in intact rats. In the Syrian hamster pineal Β-adrenergic receptor density is high throughout the light phase and drops to minimal values at the time of the nocturnal peak of melatonin production. The circadian rhythm of pineal α-adrenergic receptor numbers runs parallel to the Β-adrenergic receptor variation, but is less pronounced. In the rat, pineal melatonin production is rapidly induced by Β-adrenergic agonists at any time during a 24-hour period, even when the pinealocyte Β-adrenergic receptor number is lowest (early in the light phase). In contrast, the Syrian hamster pineal seems most responsive to Β-adrenergic agonists in the late night while being less responsive during the day when Β-adrenergic receptor density is high. Interestingly, the human pineal gland is also not especially responsive to adrenergic stimulation during the light phase, possibly making the Syrian hamster pineal a better model than the rat pineal for determining neural/pineal interactions in humans. Comparison of the circadian variations in pineal adrenergic receptors leads to the conclusion that the functional differences between rat and hamster pineal are probably not explicable in terms of the adrenergic receptors, but are caused most likely by (a) intracellular mechanism(s) beyond the adrenergic receptors.
77 citations
TL;DR: Immunological analysis indicated 33PP in both tissues is a previously reported 33-kDa protein (MEKA); this protein is a PKA substrate which has been reported to form a cytoplasmic complex with the beta gamma complex of transducin.
71 citations
TL;DR: The effect of interferon-γ (IFN-γ) on melatonin production was determined in rat pineal glands in organ culture and enhanced the production of melatonin in the glands incubated with EMT.
Abstract: The effect of interferon-γ (IFN-γ) on melatonin production was determined in rat pineal glands in organ culture. IFN-γ enhanced the production of melatonin in the glands incubated with eit...
52 citations
TL;DR: Results in rats suggest that central synapses employing ?
52 citations
TL;DR: The results provide evidence that neuronal circuits not involving the sympathetic system participate in the regulation of pineal functions in mammals, and that intimate histogenetic and functional relationships exist between the pineal organ and the habenular-pretectal nuclei in mammals.
Abstract: S-antigen-immunoreactive pinealocytes located in the deep portion of the pineal organ of inbred and wild pigmented mice give rise to long, beaded processes penetrating into the habenular and pretectal regions. In addition, the medial habenular nuclei and the pretectal area contain S-antigen-immunoreactive perikarya, which resemble pinealocytes in size, shape and immunoreactivity and are considered as “pinealocyte-like” epithalamic cells. Immunoblotting techniques reveal that a single protein band of approximately 48 kDa molecular weight accounts for this immunoreactivity. As shown with the use of the electron microscope, the majority of the S-antigen-immunoreactive processes is closely apposed to immunonegative neuronal profiles and perikarya of the habenular and pretectal regions. S-antigen-immunoreactive processes and perikarya of both pinealocytes of the deep pineal organ and pinealocyte-like epithalamic cells may form the postsynaptic element in conventional synapses involving axons provided with clear synaptic vesicles. Thus, certain mammalian pinealocytes may receive and transmit signals via point-to-point connections resembling neuro-neuronal contacts. These results challenge the concept that the mammalian pineal organ exerts its influence exclusively via the release of melatonin into the general circulation. Furthermore, they provide evidence (i) that neuronal circuits not involving the sympathetic system participate in the regulation of pineal functions in mammals, and (ii) that intimate histogenetic and functional relationships exist between the pineal organ and the habenular-pretectal nuclei in mammals.
45 citations
TL;DR: It is proposed that pre- and postsynaptic activity of GABA in the pineal does not differ from that found for GABA interneurons in local circuits of the brain.
45 citations
TL;DR: In cultured rat pinealocytes β‐adrenergic induction of N‐acetyltransferase, a key enzyme in the synthesis of melatonin, is amplified by addition of 5‐hydroxytryptamine (5‐HT) to the culture medium, but 5‐HT when added alone has no effect on enzyme activity.
Abstract: In cultured rat pinealocytes beta-adrenergic induction of N-acetyltransferase, a key enzyme in the synthesis of melatonin, is amplified by addition of 5-hydroxytryptamine (5-HT) to the culture medium. However, 5-HT when added alone has no effect on enzyme activity. Pharmacological experiments with a range of agonists and antagonists suggest that this action is not mediated by 5-HT1, 5-HT2, 5-HT3, or 5-HT4 receptor subtypes but may involve a site similar to the 5-HT1p receptor described in the enteric nervous system. The potential role of 5-HT in modulating adrenergic stimulation of N-acetyltransferase activity is discussed.
36 citations
TL;DR: Using correlative light and electron microscopic pre‐embedding immunocytochemistry, photosensory and neural elements that are immunoreactive with specific antisera against serotonin (5‐hydroxytryptamine) and the 48 kDa soluble protein S‐antigen (arrestin) are identified.
Abstract: Photoreceptor cells in the pineal complex of poikilothermic vertebrates are regarded as homologous with the neuroendocrine pinealocytes in the mammalian pineal organ. They possess an indolamine metabolism, and they contain a number of substances that are immunochemically similar to phototransduction‐related proteins otherwise found in photoreceptors of the lateral eye retina. Using correlative light and electron microscopic pre‐embedding immunocytochemistry, we have identified photosensory and neural elements that are immunoreactive with specific antisera against serotonin (5‐hydroxytryptamine) and the 48 kDa soluble protein S‐antigen (arrestin). One type of serotonin‐immunoreactive (5HTir) photoreceptor cell was identified. This was characterized by a short basal pole, into which an immunoreactive (postsynaptic?) element protruded. Two types of ‐antigen‐immunoreactive (SAir) photoreceptor cells were observed, one characterized by a short basal pole, similar to that of the 5HTir photoreceptors and the other characterized by a long, extensively branching basal pole. In addition, two types of neurons bearing no morphological specializations typical of photoreceptor cells were SAir: bipolar neurons and multipolar neurons. These were often situated dorsally in the pineal organ. The results indicate an emergence of multiple lines of photoreceptor‐derived “pinealocytes” either early in phylogeny, or independently in different taxa. The results are discussed in relation to current theories of pineal evolution. (Less)
32 citations
TL;DR: Nighttime tryptophan loading led to substantial increases in pineal 5-hydroxytryptophan, 5-Hydroxyindole acetic acid (5-HIAA), and 5-HT but a highly significant reduction in NAT activity in comparison to saline-injected controls.
Abstract: In the rat pineal gland, the activity of serotonin N-acetyltransferase (NAT) and the concentration of melatonin are normally high at night; conversely, the concentration of serotonin (5-HT), the precursor of melatonin, is low Since tryptophan administration increases the concentration of pineal 5-HT at night, we examined its effect of melatonin production Nighttime tryptophan loading led to substantial increases in pineal 5-hydroxytryptophan, 5-hydroxyindole acetic acid (5-HIAA), and 5-HT but a highly significant reduction in NAT activity in comparison to saline-injected controls In contrast to other measured indoles, melatonin levels also were significantly diminished by tryptophan loading Nocturnally high pineal norepinephrine levels were unaltered by tryptophan administration The idea that high concentrations of 5-HT could lead to substrate inhibition of NAT activity was not supported by kinetic analysis of control NAT levels versus tryptophan-inhibited NAT activity under varied substrate concentrations Hypotheses to explain these results include the possibility that tryptophan inhibition of melatonin synthesis is mediated by the release of 5-HT from the pinealocyte and its subsequent autocrine action on melatonin production
31 citations
TL;DR: The presence of synaptophysin in pinealocytes of the normal pineal, including the deep portions of the gland, emphasizes the paraneuronal character of these cells.
Abstract: Synaptophysin (protein p38), a major integral membrane glycoprotein of small presynaptic vesicles, was localized immunohistochemically in semithin sections of the superficial pineal gland of the Mongolian gerbil (Meriones unguiculatus). Synaptophysin immunoreactivity could be detected in all pinealocytes, which were visualized with antibodies directed against neuron-specific enolase (NSE) in adjacent sections. No p38 immunoreactivity was discernible in the interstitial glial cells, which showed a heterogeneous pattern of immunostaining for the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. Pinealocytes exhibited considerable intercellular differences in the densities of immunostaining. The various degrees of synaptophysin immunoreactivities in pinealocytes were not correlated with the densities of NSE immunostaining. Nerve terminals and varicosities displayed stronger immunoreactivities than pinealocytes. They were particularly numerous in the perivascular spaces. It is not clear whether this distribution indicates an innervation of pineal capillaries in addition to the functionally important innervation of pinealocytes. Several highly p38-positive dots of variable size were a conspicuous feature throughout the gland. By the consecutive semithin-thin section technique, they could be identified as processes of pinealocytes, filled with accumulations of small clear vesicles. Obviously, these vesicles represent the major site of synaptophysin immunoreactivity in pinealocytes. In the gerbil, similar vesicles have been ascribed a role in the secretory activity of the gland, and/or in the transport of calcium. The intercellular differences in the degrees of p38 immunostaining may, therefore, reflect different states of a specific cellular activity. The presence of synaptophysin in pinealocytes of the normal pineal, including the deep portions of the gland, emphasizes the paraneuronal character of these cells.
30 citations
TL;DR: All stages of differentiation of sensory structures are found in the chick pineal organ during the second half of the incubation period and the first two weeks after hatching, and the cytodifferentiation parallels the development in vivo.
Abstract: The development of sensory structures in the pineal organ of the chick was examined by means of scanning electron microscopy from embryonic day 10 through day 12 post-hatching. At embryonic day 10, the wall of the tubules within the pineal primordium is composed of cells with unspecialized luminal surface. Differentiation of sensory structures starts at embryonic day 12 when pinealocytes and supporting cells can be distinguished. Pinealocytes are recognized by virtue of an inner segment only rarely endowed with a cilium, whereas supporting cells exhibit numerous short microvilli. Further differentiation of the sensory apparatus is achieved by development of an oval-shaped, biconcave swelling at the tip of the cilium, 1×2 μm in size, and a collar of long microvilli at the base of the inner segment. Membrane specializations of sensory cilia, however, were not detected. Since during embryonic life new tubules and follicles are continuously formed, all stages of differentiation of sensory structures are found in the chick pineal organ during the second half of the incubation period and the first two weeks after hatching. In 200-μm-thick Vibratome sections of chick-embryo pineal organs cultured in medium BM 86 Wissler for periods up to 13 days the cytodifferentiation parallels the development in vivo. Using an organ-culture system the 24-h release of melatonin into the culture medium was measured by means of radioimmunoassay after solid-phase extraction. At embryonic day 10, the 24-h secretion of melatonin was at the lower range of detection of the RIA (5 pg). The rapid increase in 24-h secretion in melatonin until hatching (∼50 μg) is approximated by an exponential curve.
TL;DR: It is shown that the NPY/NPYamide-immunoreactive nerve fibers innervating the pineal gland in this spegcies are a component of the central innervation or originnate from extracerebral parasympathetic ganglia.
Abstract: An immunohistochemical investigation of the mink pineal gland was performed by use of antibodies raised in rabbits against neuropeptide Y (NPY) and Cys-NPY (32–36)-amide recognizing neuropeptide Y with an amidation at position 36 (NPYamide). NPY-immunoreactive nerve fibers were located predominantly in the rostral part of the pineal gland and in the pineal stalk. Immunoreactive nerve fibers were found throughout the pineal gland, but the number of fibers in the caudal part of the gland was low. The fibers were present both in the perivascular spaces and between the pinealocytes. Many NPY-immunoreactive fibers were also located in the posterior and habenular commissures; some of these fibers were connected with the fibers in the rostral part of the mink pineal gland, indicating that at least some of the NPY-immunoreactive nerve fibers are of central origin. The nerve fibers immunoreactive to amidated NPY were distributed in a similar manner. However, the number of fibers immunoreactive to NPYamide was lower than the number of fibers immunoreactive to NPY itself. After removal of the superior cervical ganglia bilaterally 22 days or 12 months before sacrifice, NPY-immunoreactive nerve fibers remained in the gland. This immunohistochemical study of the mink pineal gland therefore shows that the NPY/NPYamide-immunoreactive nerve fibers innervating the pineal gland in this spegcies are a component of the central innervation or originnate from extracerebral parasympathetic ganglia.
TL;DR: Results indicate that cGMP is involved as a second messenger in the regulation of synaptic ribbon numbers in the rat pineal gland.
Journal Article•
TL;DR: Detailed examination of pineal-brain relationships clearly suggests that, due to the generally deep location of the pineal in relation to cerebral hemispheres, pinealectomies in the species studied may be extremely difficult, it not entirely impossible.
Abstract: This investigation is based upon the pineal organs of 92 specimens of 36 species of the family Pteropodidae (Mammalia, Chiroptera). The size of the megachiropteran pineal correlates well with body size (r = 0.864), confirming the former conclusions that generally larger bodied bats have larger pineals. The range of the pineal size index in 36 megachiropteran species is from 33 to 4393. In most species the pineal organs are small, deeply recessed under the cerebral hemispheres and of Type A (except in Dobsonia and Pteropus, where they are of Type alpha beta C and AB, respectively). Morphological and volumetric data gathered from serially sectioned brains include body and brain weights, pineal type, dimensions, volume and size index for each species. There are distinct dorsal and ventral subdivisions of the pineal in some species and a clear separation of pineal parenchyma into cortical and medullary regions in others. In several species where overlying ependyma is lacking pinealocyte clusters communicate freely with the CSF. Groups of intrapineal neurons are noted in the connective tissue beside blood vessels. The habenular commissure shows much interspecific variation in its course through the pineal. Detailed examination of pineal-brain relationships clearly suggests that, due to the generally deep location of the pineal in relation to cerebral hemispheres, pinealectomies in the species studied may be extremely difficult, it not entirely impossible. The absolutely and relatively largest pineal organ among bats, and relatively perhaps among all vertebrates, has been discovered in the New Guinean naked-backed bat, Dobsonia praedatrix, with pineal size index of 4393, and a volume of 16.3447 mm3, which is 0.56% of the brain. This alpha beta C-type, mushroom-shaped, solid and compact pineal organ measures 5.33 x 4.51 mm. The cortical and medullary parenchyma are divided into lobes by large calibre blood vessels along which numerous intrapineal neurons are observed. A smaller but similarly shaped pineal is noted in the other three Dobsonia. Data on the largest known pineals in ratitae birds, seals and walruses have been compared with that of D. praedatrix and the human pineal. This study supports the hypothesis that pineal development may reflect dependence on habitat and possibly other related factors.
TL;DR: Using the histochemical method for the demonstration of NADPH-diaphorase activity, the pineal organ of the frog and rat was investigated in serial sections and results are discussed in light of previous morphological findings using the acetylcholinesterase reaction and with electrophysiological results.
Abstract: Using the histochemical method for the demonstration of NADPH-diaphorase activity, the pineal organ of the frog and rat was investigated in serial sections. A positive NADPH-diaphorase activity was demonstrated in pinealocytes and nerve cells in the pineal organ of the frog, but not in the rat. An intense activity existed in the apical portion of the photosensitive pinealocytes of the frog. Large NADPH-diaphorase positive nerve cells (15-20 microns in diameter) were located within the parenchyma of the pineal organ in the frog. Large NADPH-positive nerve cells were more numerous in the rostral than in the caudal portion of the organ, but the intensely stained cells, counting 25-35 in number, showed almost equal distribution and number in the ventral and the dorsal aspect of the pineal organ. In their staining ability, NADPH-diaphorase positive pineal nerve cells resembled retinal amacrine cells. The results in the pineal organ of the frog are discussed in light of previous morphological findings using the acetylcholinesterase reaction, and with electrophysiological results.
TL;DR: The accumulation of phosphorylated neurofilaments in the processes of pinealocytes appears to be a normal morphological characteristic of the pineal gland and may not represent a pathological change in patients with Alzheimer's disease or controls.
Abstract: Patients with Alzheimer's disease (AD) and some aged controls may have diminished functions of the pineal gland. In this immunocytochemical study, we stained pineal glands from cases of AD and young and aged controls for cytoskeletal elements and amyloid. We found no evidence of neurofibrillary tangles (NFT) or the accumulation of neurofilaments, tau, A68, or beta/A4 amyloid deposition in pinealocytes or associated structures in cases of AD or controls. In both AD and controls, we observed dense immunoreactivity for phosphorylated neurofilaments in marginal plexuses associated with processes of pinealocytes, boutons, and knob-like endings. The accumulation of phosphorylated neurofilaments in the processes of pinealocytes appears to be a normal morphological characteristic of the pineal gland and may not represent a pathological change.
TL;DR: The location of VIP‐containing fibers in the capsule of the pineal gland indicates that the fibers originate from perikarya located in a peripheral ganglion.
Abstract: Vasoactive intestinal peptide (VIP)-like immunoreactive nerve fibers were demonstrated by peroxidase antiperoxidase (PAP) inmmunohistochemistry to be distributed throughout the entire pineal gland of the sheep. VIP-containing fibers were observed along the blood vessels, penetrating into the gland from the pial capsule and also in the capsule itself. Some fibers left the perivascular position and entered the pineal parenchyma, where they were located among pinealocytes. This suggested that the VIPergic fibers might influence both pinealocytes and blood vessels of the gland. The location of VIP-containing fibers in the capsule of the pineal gland indicates that the fibers originate from perikarya located in a peripheral ganglion.
TL;DR: The ultrastructure of the dog pineal gland from the first postnatal day to the seventh month is described, which shows immature proliferative cells with abundant cytoplasmic glycogen are still found in the pineal glands of 1 mo‐old dogs.
Abstract: The ultrastructure of the dog pineal gland from the first postnatal day to the seventh month is described. In the first postnatal stages, pineal parenchyma only shows immature proliferative cells with abundant cytoplasmic glycogen. Nerve fibers are seen in the pineal connective tissue spaces. The differentiation of the dog pineal cell types begins in the first postnatal week. Both pinealocytes and pigmented cells are first seen on the fourth postnatal day. The pineal astrocytes are observed on the tenth day. Immature cells are still found in the pineal gland of 1 mo-old dogs. The differentiation of the dog pineal cell types is completed by the second postnatal month.
TL;DR: In the mammalian pineal and in other cells or tissues, S-antigen, or a family of structurally related proteins, could similarly be involved in the regulation of chemical signal transduction.
Abstract: S-antigen has been considered a specific protein of photoreactive cells by immunohistochemical criteria. It was observed in the retina and pineal gland of all examined vertebrates as well as in photoreceptors of invertebrates, but not currently in other organs. However, contrary to pineal cells of poikilotherms and birds which are true or modified photoreceptors, mammalian pinealocytes are not photosensitive. Recent experiments demonstrated that S-antigen-like proteins are present in low amount in many other cells in the body. These proteins are characterized by the same migration pattern (the same molecular weight) as retinal S-antigen in SDS-electrophoresis and by their immuno-reactivity with a panel of monoclonal and polyclonal antibodies to S-antigen. These cells are not photosensitive, but are controlled by β adrenergic, G-protein mediated adenylate cyclase system, a transduction system that shares many structural and functional homologies with visual transduction. S-antigen (arrestin) plays a regula...
TL;DR: The distribution of two major immunoreactive forms of somatostatin within the brain, pancreas and intestine of adult lampreys, Petromyzon marinus, was identified using antisera raised against these peptides as mentioned in this paper.
Abstract: The distribution of two major immunoreactive forms of somatostatin, somatostatin-14 and somatostatin-34, within the brain, pancreas and intestine of adult lampreys, Petromyzon marinus, was identified using antisera raised against these peptides. Immunostaining of the brain is similar in juveniles and upstream migrants, and somatostatin-14 is the major somatostatin form demonstrated. A few somatostatin-34-containing cells are localized within the olfactory bulbs, thalamus and hypothalamus, but cells immunoreactive to anti-somatostatin-34 in the hypothalamus and thalamus do not co-localize somatostatin-14. Immunostaining of pinealocytes within the pineal pellucida with anti-somatostatin-14 may infer a novel function for this structure. Somatostatin-14 and somatostatin-34 are co-localized within D-cells of the cranial pancreas and caudal pancreas of juveniles and upstream migrants. Numerous somatostatin-34-immunoreactive cells are distributed within the epithelial mucosa of the anterior intestine but not all of these cells cross-react with anti-somatostatin-14. It appears that somatostatin-34 is the major somatostatin in the pancreo-gastrointestinal system of adult lampreys.
TL;DR: The results indicate that the development and differentiation of pinealocytes in both pineal portions may be advanced under long photoperiods and delayed under short photoperperiods, although pineAlocytes in the deep pineal may remain not fully differentiated even in adults.
Abstract: Male adult (200-day-old) Chinese hamsters (Cricetulus griseus) raised from weaning under either LD 16:8 or LD 8:16 were used. The pineal gland of the Chinese hamster consists of superficial (major) and deep (minor) components and a continuous, or interrupted, narrow parenchymal stalk interposed between them. The volume of the superficial pineal including the parenchymal stalk is greater under LD 16:8 than under LD 8:16. Under both photoperiods, pinealocytes in the superficial pineal have larger nuclei and more abundant cytoplasm than those in the deep pineal. Nuclei in the superficial pineal appear pale and usually have irregular profiles, whereas those in the deep pineal appear dark and have round profiles. In the superficial pineal, pinealocyte nuclei are larger, paler, and more irregular; and, in addition, nuclear density is lower under LD 16:8 than under LD 8:16. Similar, but less prominent, photoperiod-induced changes occur in the volume of the deep pineal, the size of pinealocytes, and pinealocyte nuclear morphology in the deep pineal. The results indicate that the development and differentiation of pinealocytes in both pineal portions may be advanced under long photoperiods and delayed under short photoperiods, although pinealocytes in the deep pineal may remain not fully differentiated even in adults. Since testicular weights and body weights are similar under both photoperiods, the photoperiod may exert marked influences on the development of the pineal gland without affecting reproductive activity and growth rates of animals.
TL;DR: Both the rat and hamster pineal gland showed a transient and temporally defined expression of c-fos protein in the middle of the dark period, which may be related to a more active functional state of pinealocytes, which is reflected in a peak of melatonin synthesis during the darkness.
Abstract: Induction of c-fos protein (FOS) after the onset of darkness was studied immunocytochemically in the rat and hamster pineal gland. The animals were kept on a 12:12 h light-dark cycle. Before the dark period no FOS staining was seen in either rat or hamster pineal cells. Five hours after the onset of darkness 342±18 pinealocytes/0.2 mm2 (mean±SD) displayed FOS-like immunoreactivity in the hamster pineal gland; in the rat pineal gland only 5±2 pinealocytes/0.2 mm2 showed a faint staining. Two hours later the density of FOS positive cells was decreased to 60±11/0.2 mm2 in the hamster but increased to 519±103/0.2 mm2 in the rat pineal gland. Three hours before the beginning of the light period no FOS positive cells were detected in either animal. Both the rat and hamster pineal gland showed a transient and temporally defined expression of c-fos protein in the middle of the dark period. This may be related to a more active functional state of pinealocytes, which is reflected in a peak of melatonin synthesis during the darkness.
TL;DR: It is concluded that the age-related decline in pineal metabolism may be due to both decreased parenchymal cell number and reduced sympathetic innervation.
TL;DR: Results of the present study show that morphological patterns of higher metabolic activity of the rat pinealocyte at night when compared to those during daytime correlate with melatonin concentrations.
Abstract: The aim of this study was to investigate the ultrastructure of rat pinealocyte during daytime (1600 h) and at night (0100 h) and to compare these observations with serum melatonin levels in the same animals. In addition, pineal melatonin concentrations were determined in other animals. Both serum and pineal melatonin concentrations were significantly higher at night than during daytime (34 and 21 times, respectively). Sizes of pinealocytes, their nuclei, and nucleoli, as well as cross-sectional areas of mitochondria and granular endoplasmic reticulum were also higher at night than during daytime, whereas areas of lysosomes, Golgi apparatus, and vacuoles containing flocculent material did not differ at the time points studied. In contrast, the number of dense-core vesicles was higher during daytime. The results of the present study show that morphological patterns of higher metabolic activity of the rat pinealocyte at night when compared to those during daytime correlate with melatonin concentrations.
TL;DR: Nocturnal light exposure did not suppress enzyme activity in 3- to 5-day-old rats, even though these animals displayed clear light:dark differences in pineal gland NAT activity, suggesting that this effect is retinally mediated.
Abstract: In adult rats, light acting via a retino-pineal gland neural pathway influences pineal gland biochemistry in two ways: (1) it entrains endogenous circadian rhythms in melatonin biosynthesis to the environmental photoperiod and (2) exposure to even very brief periods of light during the nighttime rapidly suppresses the high levels of nocturnal melatonin production. The present studies were undertaken to determine precisely when photic stimulation first influences the enzymic activity of N-acetyltransferase (NAT), the pineal gland enzyme which rate-limits the overall biosynthesis of the hormone melatonin, and to examine some of the cellular mechanisms which might mediate light-induced effects in neonatal animals. Rats of different ages were either killed during the light phase or were exposed to darkness or light for 1 min during the dark phase of the lighting cycle, returned to their litters in darkness for 30 min and then killed. Pineal gland NAT activity in animals nocturnally exposed to 1 min of light was suppressed in animals 6 days of age or older. Nocturnal light exposure did not suppress enzyme activity in 3- to 5-day-old rats, even though these animals displayed clear light:dark differences in pineal gland NAT activity. Nocturnal light exposure also did not suppress nighttime levels of NAT activity in 7-day-old animals who had been bilaterally enucleated, suggesting that this effect is retinally mediated. Pretreatment of 7-day-old animals with the beta-noradrenoceptor agonist drug, isoproterenol, prevented the nocturnal light-induced suppression of NAT activity.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The lack of neurofilament- and tubulin-immunoreactivity in rat pinealocytes might be attributable to very low concentrations of these proteins or species differences as to their expression, and further studies including in situhybridisation of relevant mRNAs will be necessary to answer these questions definitely.
Abstract: Although some embryological and morphological features speak in favour of a neuronal character of rodent pinealocytes, histochemistry and ultrastructure let this issue appear controversial. Using antibodies to different neurofilaments, the neural adhesion molecule L1, synaptophysin and tubulin as neuronal markers, the pineal glands of rat and guinea-pig were studied by means of immunfluorescence. Neurofilament-immunoreactivity was present in some rat pineal nerve fibers and in the majority of guinea-pig pinealocytes, L1 decorated rat intrapineal nerve fibers, synaptophysin was almost ubiquitously distributed in the pineal of both species, while tubulin-immunofluorescence was seen in nerve fibers of rat and guinea-pig pineal and in some pinealocytes of the latter. These findings speak in favour of the neuronal character of guinea-pig pinealocytes. The lack of neurofilament- and tubulin-immunoreactivity in rat pinealocytes might be attributable to very low concentrations of these proteins or species differences as to their expression. Further studies including in situhybridisation of relevant mRNAs will be necessary to answer these questions definitely.
TL;DR: Results indicate that pinealocytes have a single beta-adrenoceptor, of the beta 1-subtype, which mediates adrenergic stimulation of not only cyclic AMP but also cyclic GMP.
Journal Article•
TL;DR: It was found that primary mineralization occurs in an organic matrix formed by pinealocytes and that hydroxyapatite also takes place in mineral deposition.
Abstract: Acervuli and fragments of pineal gland obtained from 33 subjects of both sexes and age ranging from 1 to 87 years, (30 autopsy and 3 biopsy specimens) were analyzed by light microscopy, transmission and scanning electron microscopy, X-ray diffraction and X-ray energy dispersive microanalysis. It was found that primary mineralization occurs in an organic matrix formed by pinealocytes and that hydroxyapatite also takes place in mineral deposition. From our analysis, the formation of acervuli appears to be age and sex independent and can be possibly related to the secretory activity of the gland.
TL;DR: The large and extremely active pineal gland in newborn southern elephant seal suggests that it is actively involved in thermoregulation.
Abstract: In the newborn southern elephant seal the pineal gland is very large, and both pineal and plasma melatonin concentration is elevated. The pineal gland was investigated during the first 24 h, and up to 20 days of age, in elephant seal pups. A primary aim of this investigation was to determine whether there are obvious ultrastructural characteristics of pinealocytes that are exhibiting extraordinarily high levels of activity. Blood and pineal glands were collected from thirty seven pups of known age which were sampled at random from early September to early November (1985) at Macquarie Island. The pineal gland is large (mean weight, 4.71 +/- 0.35 gm, range 1-9.3 gm) and actively secreting melatonin at birth. Melatonin concentrations were extremely variable, yet very high in pups during the first 24 h post-partum. Mean melatonin plasma concentration for pups 0-24 h was 17632.8 +/- 5723.8 pmol/l (4090.8 +/- 1327.9 pg/ml), ranging from 126 pmol/l (29 pg/ml) to 297000 pmol/l (68904 pg/ml). Electron microscopic examination did not reveal any marked changes in pinealocyte ultrastructure suggestive of increased secretory activity during this period. The large and extremely active pineal gland in newborn southern elephant seal suggests that it is actively involved in thermoregulation.
TL;DR: Findings indicate that even in advanced age, the human pineal gland maintains some functions, such as intercellular communication and photoreception, in common with the pineal in lower vertebrates.
Abstract: An ultrastructural study of human pineal glands obtained at autopsy from 7 patients older than 70 years was conducted in order to clarify the functional anatomy of the pineal in the aged. By light microscopy, the pineal glands from aged patients were parenchymatous and almost indistinguishable from those of younger controls. Electron microscopy of the pineal parenchymal cells revealed deep nuclear indentations, synaptic ribbons and ribbon fields, Golgi apparatus, lipofuscin granules and microtubular sheaves in all subjects, cilia with a 9 + 0 pattern in a few, and lamellated structures suggestive of the outer segment of photoreceptor cells very rarely. Microtubules were numerous in the cytoplasmic processes and bulbous endings. Fibrous astrocytes located between the pinealocytes showed long and thin cytoplasmic processes containing numerous glial filaments. Two types of nerve bouton were present in the pineal parenchyma, one of which contained clear vesicles forming synapse-like contacts with pinealocytes. There were no significant age-related changes in these features in a qualitative comparison with pineal glands from 5 adult patients younger than 70 years. These findings indicate that even in advanced age, the human pineal gland maintains some functions, such as intercellular communication and photoreception, in common with the pineal in lower vertebrates.