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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: HIOMT activity is significantly increased by 80% in mid-December compared with end of October, and this increase is correlated with the appearance of a nycthemeral rhythm of pineal 5-ML levels, suggesting that NPY could be an important neurotransmitter involved in the seasonal control of the biochemistry of the European hamster pineal gland via a stimulatory effect on HIOMt activity.
24 citations
TL;DR: The present results suggest that cytokines such as LIF and/or CNTF induce SPI-3 expression via STAT3 in the pineal gland in response to inflammatory stimulus, and it is concluded that although the functional consequences of SPI-2 in thepineal gland during systemic inflammation are unknown, SPI- 3 may have a crucial role in preventing some degenerative proteolysis induced by inflammatory stimuli.
24 citations
TL;DR: A series of 16 cerebellar medulloblastomas were studied immunohistochemically using a four-step immunoperoxidase method and a monoclonal antibody, finding that immunopositivity was demonstrated in a variable number of tumor cells in 50% of the cases.
Abstract: A series of 16 cerebellar medulloblastomas were studied immunohistochemically using a four-step immunoperoxidase (PAP) method and a monoclonal antibody (MAbA9-C6) which defines an epitope of the retinal S-antigen, a protein known to occur in retinal photoreceptor cells and pinealocytes of the pineal gland as well as in retinoblastomas, pineocytomas and pineoblastomas. Immunopositivity was demonstrated in a variable number of tumor cells in 50% of the cases. This finding may be an indication of a differentiation potential of medulloblastomas along the photoreceptor cell lineage. Alternatively, it may simply indicate the non-specificity of the retinal antigen in the neoplastic state.
24 citations
TL;DR: The results obtained indicate that the numbers of SR and SS are influenced by melatonin and serotonin and that the two structures are regulated by differential, but nevertheless biochemically closely related mechanisms.
Abstract: Previous studies have shown that the "synaptic" ribbons (SR) and spherules (SS) of the mammalian pineal gland may respond differently under physiological and various experimental conditions. The aim of the present study was to gain insight into the mechanisms that may be responsible for the numerical changes of these organelles during a 24-h cycle. As the possibility exists that the structures are influenced by substances synthesized within the pinealocyte, rat pineal glands were cultured with and without added melatonin or serotonin, using an experimental protocol such that the addition of melatonin and serotonin mimicks the circadian changes of the respective substances within the pineal. The tissue was processed for electron microscopy and the numbers of SR and SS were counted in a unit area of pineal tissue. The results obtained indicate that melatonin added to the incubation medium increases the number of SR in the first half of the night; serotonin decreases SR numbers in the morning. SS numbers, by contrast, decrease following melatonin administration in the afternoon, and increase in the morning following serotonin administration. It thus appears that the numbers of SR and SS are influenced by melatonin and serotonin and that the two structures are regulated by differential, but nevertheless biochemically closely related mechanisms.
24 citations
TL;DR: This study reveals that the stimulatory effect of opioid receptor on melatonin synthesis is mediated via the activation of adenylate cyclase system.
Abstract: Mammalian pinealocytes synthesize and secrete melatonin. The synthesis of melatonin is regulated by several biogenic amine, amino acid and peptide transmitters. In our previous study, the delta- and mu-opioid receptors have been identified and characterized in bovine pinealocytes. In order to elaborate the function of different types of opioid receptors in regulating melatonin synthesis, we used a selective mu-opioid receptor agonist, Tyr-[D-Ala(2), N-methyl-phe(4), glycol(5)] (DAMGO), a selective delta-opioid receptor agonist, Enkephalin [D-Pen(2), D-Pen(5)], (DPDPE) and a selective kappa-opioid receptor agonist, ((+)-(5alpha, 7alpha, 8beta)-N-methyl-N-[7- (1-pyrrolidinyl)-1-oxaspiro [4,5] dec-8-yl]-benzene acetamide) (U69593) to investigate the activity of N-acetyltransferase (NAT) activity and melatonin secretion. The results of the present study show that both DAMGO and DPDPE stimulated NAT activity and increased the level of melatonin in cultured bovine pinealocytes. These stimulatory effects were blocked by naloxone, an opioid receptor antagonist. However, the kappa-opioid receptor agonist U69593 was unable to alter either the activity of NAT or the level of melatonin. In order to clarify the mechanism of how the activation of mu- and delta-opioid receptors in bovine pinealocytes leads to an increase in NAT activity, cyclic AMP levels were measured after bovine pinealocytes were treated with morphine, DAMGO and DPDPE. The results indicated that these stimulatory effects acted via induction of cAMP production. This study reveals that the stimulatory effect of opioid receptor on melatonin synthesis is mediated via the activation of adenylate cyclase system.
24 citations