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Pinealocyte
About: Pinealocyte is a research topic. Over the lifetime, 1605 publications have been published within this topic receiving 55609 citations.
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TL;DR: The results suggest that the pineal circadian clock may determine timing when Aa‐Nat gene expression can respond to inputs from the master circadian clock in the suprachiasmatic nucleus, e.g. adrenergic stimulation.
Abstract: In mammals it has been thought that the circadian clock localizes only in the suprachiasmatic nucleus of the hypothalamus. Recent studies have revealed that certain brain regions and peripheral tissues may also have intrinsic circadian clocks. However, the roles played by 'peripheral circadian clocks' have not been fully elucidated. In this study, we investigated their function using mouse pineal glands, and found that expression of the arylalkylamine N-acetyltransferase (Aa-Nat, EC 2.3.1.87, the rate-limiting enzyme of melatonin synthesis) gene after adrenergic receptor stimulation depended on the time of day even in vitro (gating). Phase-dependent Aa-Nat responses were observed in both melatonin-proficient and melatonin-deficient mouse pineal glands. Phosphodiesterases are unlikely to suppress Aa-Nat induction because a phosphodiesterase inhibitor itself had no effect on the mRNA levels. Puromycin was ineffective in inducing Aa-Nat mRNA levels in either the presence or absence of isoproterenol, suggesting that newly synthesized proteins may not be necessary to gate the Aa-Nat responses. We also discovered circadian dependence of the expression of Period1-luminescence in Period1-luciferase transgenic mouse pineal glands: circadian clocks may be functional in culture. Aa-Nat mRNA levels showed no significant circadian rhythms in the absence of isoproterenol, thus suggesting that Aa-Nat mRNA levels are induced by adrenergic mechanisms, not by a pineal circadian clock. Our results suggest that the pineal circadian clock may determine timing when Aa-Nat gene expression can respond to inputs from the master circadian clock in the suprachiasmatic nucleus, e.g. adrenergic stimulation.
30 citations
TL;DR: The authors' results suggest that P. m.
30 citations
TL;DR: These observations are the first to document that deletion of Lhx9 results in hydrocephalus and as such indicate that Lh x9 contributes to the maintenance of normal brain structure and that this effect is not secondary to Hydrocephalus.
Abstract: Lhx9 is a member of the LIM homeobox gene family. It is expressed during mammalian embryogenesis in the brain including the pineal gland. Deletion of Lhx9 results in sterility due to failure of gonadal development. The current study was initiated to investigate Lhx9 biology in the pineal gland. Lhx9 is highly expressed in the developing pineal gland of the rat with transcript abundance peaking early in development; transcript levels decrease postnatally to nearly undetectable levels in the adult, a temporal pattern that is generally similar to that reported for Lhx9 expression in other brain regions. Studies with C57BL/6J Lhx9−/− mutant mice revealed marked alterations in brain and pineal development. Specifically, the superficial pineal gland is hypoplastic, being reduced to a small cluster of pinealocytes surrounded by meningeal and vascular tissue. The deep pineal gland and the pineal stalk are also reduced in size. Although the brains of neonatal Lhx9−/− mutant mice appear normal, severe hydrocephalus develops in about 70 % of the Lhx9−/− mice at 5–8 weeks of age; these observations are the first to document that deletion of Lhx9 results in hydrocephalus and as such indicate that Lhx9 contributes to the maintenance of normal brain structure. Whereas hydrocephalus is absent in neonatal Lhx9−/−mutant mice, the neonatal pineal gland in these animals is hypoplastic. Accordingly, it appears that Lhx9 is essential for early development of the mammalian pineal gland and that this effect is not secondary to hydrocephalus.
30 citations
TL;DR: A parsimoneous explanation of this is that a single circadian system regulates the expression of both AA-NAT and TPH genes in most teleosts, and that in trout this system has been disrupted, perhaps by a single mutation.
29 citations
TL;DR: Evidence that secretory activity is maintained from embryonic stages to adulthood is provided and dense core vesicles are located both around the Golgi apparatus and in the basal process.
Abstract: The pineal organ of the chicken was investigated electron microscopically during embryonic and post-hatching development with special regard to photosensory and secretory features. Throughout the developmental period both pinealocytes and supporting cells, of which the pineal parenchyma is composed, were rich in ribosomes, granular endoplasmic reticulum and mitochondria, but lacked agranular endoplasmic reticulum. The outer segments of pinealocytes barely showed formation of lamellar structures (disks) at the 17th and 21st day of incubation. Before and after hatching the follicular lumen was often filled with amorphous material presumed to be derived from outer or inner segments. By 15 days after hatching the whorl-like structures were occasionally connected to bulbous outer segments, and their relation appeared similar to that of the adult. Mitochondria disappeared from the inner segments after 21 days of incubation. Dense core vesicles (about 80–120 nm in diameter), regarded as secretory granules, appeared first at the 10th day of incubation in the supranuclear region of the pinealocyte. With the extending of basal processes the dense core vesicles gradually migrated into these processes, attained maximum number one month after hatching and increased further in the adult; they are located both around the Golgi apparatus and in the basal process. These results provide evidence that secretory activity is maintained from embryonic stages to adulthood.
29 citations