Pinealocyte

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

Opsin photoisomerases in the chick retina and pineal gland: characterization, localization, and circadian regulation.

Abstract: PURPOSE. The chick retina and pineal gland exhibit circadian oscillations in biochemical and physiological processes in vivo and in vitro, which entrain to 24-hour light- dark cycles. However, the phototransduction mechanisms responsible for entrainment are largely unknown. The present study characterizes two candidate opsinlike genes that may play a role in entrainment of the clocks in these tissues. METHODS. Bioinformatics, cladistic techniques, and in situ hybridization and Northern blot analyses were conducted to characterize, localize, and determine the circadian expression of the candidate opsinlike genes in the retina and pineal gland. RESULTS. Two candidate photosensors and/or photoisomerases were predominantly distributed within the pineal gland and retina: the retinal pigmented epithelium-derived rhodopsin homologue (peropsin, gRrh) and retinal G-protein- coupled receptor opsin (RGR opsin, gRgr). Northern blot and in situ analyses revealed mRNA expression for both opsins in the pineal gland, retina, and brain tissue. The mRNA for both genes within the pineal gland and retina is regulated on a circadian basis such that they are highest in late subjective day. Digoxigenin in situ analyses showed retinal gRgr message within the inner nuclear layer (INL) and retinal ganglion cell layer (RGL), whereas gRrh message was distributed predominantly in the RGL. In the pineal gland, gRgr message was sparsely distributed among pinealocytes in follicles, but not within the follicles themselves, whereas gRrh was localized in interstitial areas indicative of astrocytic and/or endothelial origin. CONCLUSIONS. The presence of two putative photoisomerases within the pineal gland and in retinal layers associated with biological clock function provides two candidate opsinlike genes that may serve in the visual cycle regulation of the circadian clock.

Interferon-γ Modulates Melatonin Production in Rat Pineal Glands in Organ Culture

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...

Retinoschisin expression and localization in rodent and human pineal and consequences of mouse RS1 gene knockout.

Abstract: Purpose: The pineal gland shares a common neuroectoderm origin with the retina, and like the retina, regulates circadian rhythms through melatonin secretion. Recent expressed tag sequence (EST) analysis showed that several gene mutations, including RS1, which cause retinal degeneration, are also expressed in the pineal gland. Mutations in RS1 result in structural delamination of the neural retinal layers, leading to formation of schisis cavities in men affected with “X-linked retinoschisis” (XLRS). In this study, we evaluated RS1 expression in the rat and mouse as well as in human pineal and looked for morphological changes in the pineal of the RS1 knockout (RS1 -/Y ) mouse. Methods: We analyzed rat and mouse pineal for RS1 expression by Northern blot and in situ hybridization. RS protein, synaptophysin, S-100, and GFAP localization in the pineal of rat and mouse and RS protein in human pineal were evaluated immunohistochemically. Morphological studies were performed using transmission electron microscopy and light microscopy comparing wild-type to the RS1 -/Y mouse. Results: RS1 expression was detected in RNA isolated from both the pineal and retina as a single major band migrating at about 5.5 kbp in Northern blots. RS1 riboprobe in situ hybridization demonstrated message in rat and mouse pineal, and immunohistochemistry showed RS protein in pinealocytes expressing synaptophysin but not in interstitial GFAP- and S100-positive glial cells. RS protein was present in many pinealocytes in human pineal. In light and electron microscopic examination of the pineal gland from RS1 -/Y mice none of the structural changes found in the retina, such as cavity formation and loosening of the tissue, were seen. Conclusions: This study demonstrates that RS protein is expressed in the pinealocytes but not in interstitial glial cells. The lack of structural abnormalities in the RS1 -/Y mice suggests that RS serves a different function in the pineal gland than in the retina.

Melatonin synthesis and melatonin-membrane receptor (MT1) expression during rat thymus development: role of the pineal gland.

Abstract: To gain insight into the relationship between thymus and pineal gland during rat development, the melatonin content as well as the activity and expression of the two key enzymes for melatonin biosynthesis, i.e. N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were studied in the thymus at fetal and postnatal stages. Moreover, melatonin-membrane receptor (MT1) expression was also analyzed. We found both the expression and activity of thymic NAT and HIOMT at 18 days of fetal life. Additionally, there is production of melatonin in the thymus as well as MT1 expression at this fetal age. These results show values higher in day-time than at night-time. The pineal gland begins to produce significant levels of melatonin around postnatal day 16, and this synthesis shows a circadian rhythm with high values during the dark period; therefore the nocturnal serum melatonin may inhibit thymic melatonin production. To document this, we report an increased melatonin content of the thymus in pinealectomized rats compared with sham-pinealectomized. In conclusion, these results show, for the first time, the presence of the biosynthetic machinery of melatonin and melatonin production in developing rat thymus and that the pineal gland may regulate this process.