Pinealocyte

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

The synaptic ribbons of the guinea pig pineal gland in sterile, pregnant and fertile but non-pregnant females and in reproductively active males

Abstract: Pinealocyte ultrastructure has been studied in four sterile, four pregnant and three fertile but non-pregnant females, and also in three reproductively active male pigmented Duncan Hartley guinea pigs. Synaptic ribbons are dense, rod-like structures with a linear arrangement of clear vesicles periodically spaced on both sides of the rodlet. Although these structures were observed in the pinealocytes of all of the animals studied, they were scarce and difficult to locate in tissue from the fertile, non-pregnant females and from the reproductively active males. They were numerous in the pineal glands of the pregnant and sterile females. Typically they lie perpendicular to the cell membrane of the pinealocyte polar process and in close proximity to a polar process of a neighboring cell. The increased incidence of synaptic ribbons in pinealocytes which appear to be in a heightened state of activity strongly suggests a function for this structure. Synaptic ribbons are also present in sensory systems such as rods and cones of the retina, hair cells of the organ of Corti and hair cells of the vestibular apparatus. This fact, plus the photoreceptor function of pinealocytes in lower vertebrates, lends credence to the possibility that this structure may serve a sensory or receptor function in the guinea pig gland.

Midline brain tumors in MSV-SV 40-transgenic mice originate from the pineal organ.

Abstract: Adult transgenic mice expressing the large T-antigen of the Simian virus 40 (SV 40) under the control of the Moloney murine sarcoma virus (MSV) enhancer and the SV 40 promoter develop inheritable uniform midline brain neoplasms showing features of primitive neuroectodermal tumors. The origin and histogenesis of these tumors were investigated in the present study. The brain and pineal organ of fetal and young transgenic mice less than 3 months old displayed normal macroscopic and microscopic features. In 3.5-month-old animals, the pineal organ was considerably enlarged due to hyperplasia, finally leading to tumor formation. Immunocytochemical demonstration of large T-antigen showed that this oncoprotein was already expressed in the nuclei of certain cells in the pineal organ of fetuses (16 and 18 days old) and newborn animals, but was absent from all other parts of the brain. The immunocytochemical demonstration of S-antigen (arrestin), a highly characteristic marker for pinealocytes, was used for further characterization of the large T-antigenimmunoreactive cells. The fetal pineal organ did not contain immunoreactive S-antigen. This first occurred in certain pinealocytes of newborn mice. Double immunostaining revealed that in newborn and older transgenic mice the immunoreactive large T-antigen was exclusively found in nuclei of cells containing S-antigen immunoreaction in their cytoplasm. Thus, transformed pinealocytes appear as stem cells of the experimental tumors. The results of this study suggest that primitive neuroectodermal tumors and the normal tissue from which they originate share certain molecular and immunocytochemical features.

Cloning, localization and functional properties of a cGMP-gated channel in photoreceptor cells from fish pineal gland.

Abstract: The perception of photic information and its translation into a rhythmic melatonin signal differ considerably among vertebrates. In the fish pineal gland, melatonin biosynthesis is controlled directly by the natural light/dark cycle. There are indications that the mechanisms of phototransduction are similar in the retinal and pineal photoreceptor cells. Here we report the molecular cloning of a novel ionic cyclic guanosine monophosphate (cGMP)-gated channel from trout pineal photoreceptors. The deduced amino acid sequence exhibits a high sequence homology to cyclic nucleotide-gated-3 (CNG) channels from retinal cones. In situ hybridization with sections of trout pineal gland revealed the expression of CNG channel in photoreceptor cells of the pineal organ. Electrophysiological studies by means of patch-clamp technique indicated that the native channel in photoreceptor cells and the expressed channel in a human cell line (HEK 293 cells) have properties similar to those of cone-CNG (cCNG)-3 channels. They are activated by cGMP, insensitive to cyclic adenosine monophosphate (cAMP) and blocked by intracellular Mg2+ ions at positive voltage values. They have a single-channel conductance close to 42 pS in negative voltage range. In transfected HEK cells loaded with the calcium indicator dye Fura 2, direct activation of CNG channels by 8-Br-cGMP increased fluorescence. The signal was blocked by the addition of Mg2+ ions. From these results, it is suggested that the pineal cyclic nucleotide-gated channel is a good candidate for mediating calcium entry into the pineal photoreceptors. It is most probably a key element in the signalling pathways that control the rhythmic production of melatonin.

Ovarian hormones regulate alpha 1- and beta-adrenoceptor interactions in female rat pinealocytes.

Abstract: We have examined the effects of alpha 1- and beta-receptor activation on cyclic AMP (cAMP) accumulation in cultured pinealocytes from female ovariectomized rats, and from intact rats at proestrus treated with the antiestrogen Tamoxifen, the antiprogestagen RU486, or with both. Isoproterenol (a beta-agonist) significantly increased cAMP levels in pinealocytes from intact and ovariectomized rats. This response was considerably enhanced in pinealocytes from rats treated with RU486 or Tamoxifen alone, but not with both. Moreover, incubation of pinealocytes with isoproterenol together with phenylephrine (an alpha 1-agonist) produced a synergistic effect in animals that had been ovariectomized, or that had received RU486, either alone or in combination with Tamoxifen. These results suggest that, in female rats, ovarian steroids may regulate the interactions between alpha 1- and beta-adrenergic receptors, and thus modulate pineal melatonin synthesis during the oestrous cycle through these mechanisms.

Spontaneous and nicotine-induced Ca2+ oscillations mediated by Ca2+ influx in rat pinealocytes.

Abstract: The pineal gland regulates circadian rhythm through the synthesis and secretion of melatonin. The rise of intracellular Ca2+ concentration ([Ca2+]i) following nicotinic acetylcholine receptor (nACh...