Pinealocyte

About: Pinealocyte is a research topic. Over the lifetime, 1605 publications have been published within this topic receiving 55609 citations.

Localization of N-ethylmaleimide-sensitive fusion protein in pinealocytes

Abstract: N-ethylmaleimide-sensitive fusion protein (NSF), a protein necessary for vesicular docking and/or fusion, was detected immunohistochemically in pinealocytes. NSF was distributed similarly to synaptophysin and vacuolar-type H(+)-ATPase (V-ATPase), marker proteins for synaptic-like microvesicles (MVs) abundantly present in pinealocytes. A subcellular fractionation study indicated that .> 95% of NSF was present as a membrane-bound form and that some NSF was associated with MVs. Like neuronal NSF, the protein was not solubilized from membranes with either 2 mM Mg-ATP or 2% sodium carbonate, suggesting that NSF was tightly bound to the membranes. NSF was also detected in purified MVs from bovine posterior pituitaries. Since MVs are the organelles in which transmitters are stored, these results suggest that NSF is involved in the MV-mediated exocytosis of transmitters from endocrine cells.

Immunohistochemical study of the glutamate transporter proteins GLT-1 and GLAST in rat and gerbil pineal gland.

Abstract: Several investigations performed during this decade have led to the hypothesis that small secretory vesicles of pinealocytes (generally referred to as synaptic-like microvesicles, SLMVs) are components of a system for intercellular paracrine communication between pineal cells, which shares many features with the process of synaptic neurotransmission. According to a recent study, one parallel that can be drawn to synaptic signal transduction seems to be the presence of pineal re-uptake systems for messenger molecules released from SLMVs, i.e. for neuroactive amino acids such as L-glutamate. In order to further characterize these uptake mechanisms, we have carried out an immunohistochemical study to explore the presence and cellular localization of the glutamate transporters GLT-1 and GLAST in rat and gerbil pineal glands. GLT-1 and GLAST were always detected in a subpopulation of pineal parenchymal cells in both species. Using immunostaining of serial semithin sections with antibodies against marker proteins of pineal cell types, GLT-1- and GLAST-positive cells were identified as interstitial glial cells. In addition, some pinealocytes also displayed immunoreactivity for GLT-1. In contrast to current thinking, our findings show that GLT-1 is not the only glutamate transporter subtype expressed in the pineal gland. Moreover, our observations point to a significant participation of interstitial cells in the process of pineal glutamatergic communication, reminiscent of the role of glial cells during glutamatergic neurotransmission in the central nervous system.

A diurnal rhythm in pineal protein 1 content mediated by beta-adrenergic neurotransmission

Abstract: A diurnal rhythm was found in the total amount of the neuron-specific phosphoprotein protein I in rat pinealocytes. β-Adrenergic neurotransmission appears to be the mechanism regulating the amount of pineal protein I in vivo.

Characterization of tryptophan high affinity transport system in pinealocytes of the rat. Day-night modulation

Abstract: Tryptophan is required in the pineal gland for the formation of serotonin, precursor of melatonin biosynthesis. The level of this amino acid in the serum and in the pineal gland of the rat undergoes a circadian rhythm, and reduced plasma tryptophan concentration decreases secretion of melatonin in humans. Tryptophan is transported into the cells by the long chain neutral amine acid system T and by the aromatic amino acid system T. The high affinity component of [3H]tryptophan uptake was studied in pinealocytes of the rat. Inhibition was observed in the presence of phenylalanine or tyrosine, but not in the presence of neutral amino acids, alanine, glycine, serine, lysine or by 2-aminobicyclo[2,2,1]-heptane-2-carboxylic acid, a substrate specific for system L. The transport of tryptophan was temperature-dependent and trans-stimulated by phenylalanine and tyrosine, but was energy-, sodium-, chloride-, and pH-independent. In addition, the sulphydryl agent N-ethylmaleimide did not modify the high affinity transport of tryptophan in pinealocytes. The kinetic parameters were not significantly different at 12:00 as compared to 24:00 h. The treatment with the inhibitor of tryptophan hydroxylase, p-chlorophenylalanine, produced an increase in the maximal velocity of the uptake and a reduction in the affinity at 12:00, but not at 24:00 h, probably indicating that during the day, the formation of serotonin in the pineal gland is favoured by elevating the uptake of tryptophan, whereas at 24:00 h other mechanisms, such as induction of enzymes are taking place. High affinity tryptophan uptake in the rat pineal gland occurs through system T and is upregulated during the day when the availability of serotonin is reduced.

Effect of superior cervical ganglionectomy on the ultrastructure of pinealocytes in the Djungarian hamster (Phodopus sungorus): quantitative study.

Abstract: OBJECTIVES: Superior cervical ganglia are of crucial importance in regulating the secretion of the pineal hormone ‐ melatonin. Changes in pineal morphology have been observed in many mammalian species after sympathectomy. Therefore, we decided to investigate the ultrastructure of Djungarian hamster pinealocytes following superior cervical ganglionectomy. MATERIAL AND METHODS: Eight adult female Djungarian hamsters (Phodopus sungorus) were used in this study. The superior cervical ganglia were removed bilaterally in four animals, whereas the other four animals served as shamoperated controls. The pineal glands were removed four weeks after the operation and processed for electron microscopic study. The cross-sectional areas of pinealocyte and its nucleus, and relative volume of mitochondria, Golgi apparatus, lysosomes, granular endoplasmic reticulum, and glycogen particles as well as the numbers of dense-core vesicles and “synaptic” ribbons were estimated using a digital analyzer connected on-line to IBM-PC computer. Statistical analysis of the data was performed using Student’s t test and Snedecor F test. RESULTS: Signifi cant reduction in the cross-sectional areas of the pinealocyte and its nucleus as well as in the relative volumes of mitochondria and glycogen particles was observed after superior cervical ganglionectomy in comparison with sham-operated controls. Sympathectomy resulted also in reduction of the number of dense-core vesicles. On the contrary 2,5 fold increase in the number of “synaptic” ribbons was observed in ganglionectomized animals in comparison to sham-operated controls. CONCLUSION: Deprivation of sympathetic innervation leads in Djungarian hamsters not only to suppression of melatonin synthesis and secretions but, as appears from our studies, induces also morphological changes suggesting lower metabolic and secretory activity of pinealocytes.