Pinealocyte

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

Effects of acute cold exposure on the ultrastructure of the mouse pinealocyte

Abstract: Ultrastructural changes in pinealocytes were investigated qualitatively and quantitatively in mice exposed to low temperatures at 0° C or 5° C for 30 or 60 min. A quantitative estimation of the granulated vesicles of about 100 nm diameter in pinealocytes demonstrated that the number of these vesicles per pinealocyte in mice exposed to cold at 0° C or 5° C increased remarkably as compared with that of the controls. This finding indicates that cold stimuli may activate the formation of the granulated vesicles in pinealocytes. In mice exposed to cold at 0° C for 60 min, granulated vesicles were often found in groups close to the plasma membrane of the pinealocyte cell bodies or processes, indicating the release of the vesicle content into the extracellular spaces. Additionally, the pinealocytes of the mice exposed to cold at 0° C for 60 min were characterized by the frequent occurrence of lysosome-like bodies and filaments. The development of these structures in response to severe cold may represent a depressed functional state of pinealocytes.

On the Significance of the 5-Hydroxytryptamine Stores in Pineal Gland

Abstract: Publisher Summary The rat is the most frequently used model in studies on the importance of certain indole derivatives, notably melatonin, in pineal gland function. The gland has a rich distribution of sympathetic nerves supplying both blood vessels and pinealocytes. These nerves are highly involved in the control of pineal indoleamine metabolism. The nerves also store a considerable quantity of 5-HT, which is taken up from the pinealocytes. There is a remarkable discrepancy between the low concentration of melatonin and the high level of 5-HT in the gland, which reflect a further significance of pineal 5-HT besides merely being a precursor in the formation of melatonin. Combined fluorescence microscopy and chemical assay of pineal 5-HT in different species reveal that the concentration of the indole in the pineal sympathetic nerves exceed that in the pinealocytes. In accordance with the high level of 5-HT in the rat pineal gland, very high activity of the unspecific aromatic amino acid decarboxylase is recorded. A considerable enzyme activity is also found in the cow, cat, and rabbit pineal, although little or no 5-HT (or catecholamines) is demonstrated histochemically in the pinealocytes from these animals.

Peptidergic peripheral nervous systems in the mammalian pineal gland.

Abstract: The distribution and density of tyrosine hydroxylase (TH) and neuropeptide Y (NPY)-immunoreactive, sympathetic fibers and calcitonin gene-related peptide (CGRP)-, substance P (SP)-, and vasoactive intestinal polypeptide (VIP)-immunoreactive, non-sympathetic fibers in the pineal gland, the effects of superior cervical ganglionectomy (SCGX) on these fibers, and the location of their terminals in the pineal gland were compared between rodents and non-rodents. A dense network of TH/NPY-positive fibers is present all over the pineal gland. A less dense network of CGRP/SP- or VIP-positive fibers occurs in the whole pineal gland of non-rodents, but these fibers are usually confined to the superficial pineal gland in rodents. After SCGX, some TH/NPY-fibers remain only in the deep pineal gland in rodents, whereas considerable numbers of these fibers persist throughout the gland in non-rodents. Thus, the remaining fibers, probably originating from the brain, may be more numerous in non-rodents. Since CGRP-, SP- or VIP-immunoreactive fibers in the pineal capsule can be traced to those in the gland, and since these fibers are ensheathed by Schwann cells, it is concluded that these fibers belong to the peripheral nervous system. However, the existence of SP-positive central fibers cannot be denied in some species. In the superficial pineal gland of rodents, sympathetic terminals are mostly localized in perivascular spaces, whereas the parenchymal innervation by sympathetic fibers in the pineal gland is more dense in non-rodents than in rodents. Synapses between sympathetic nerve terminals and pinealocytes occur occasionally in non-rodents, but only rarely in the superficial pineal gland of rodents. The occurrence of the synapses may depend on the frequency of intraparenchymal sympathetic terminals.

Modes of protein and peptide uptake in the pineal gland of the Mongolian gerbil: an ultrastructural study.

Abstract: The possible existence of either a blood-brain barrier or a CSF-brain barrier was examined in the pineal gland of the Mongolian gerbil using the ultrastructural tracers, horseradish peroxidase (HRP) and microperoxidase (MP). The mechanism of protein and peptide transport within the pineal gland and its possible relationship to pineal concretions was also considered. Gerbils were injected with either MP or HRP intravenously (IV), or they received intraventricular (IVT) injections of HRP. The IV injections resulted in both MP and HRP movement through the endothelial cells of the gland by vesicular transport and by diffusion through the endothelial cells of the gland by vesicular transport and by diffusion through the endothelial intercellular junctions. Following the IVT injections, the tracer was demonstrated in the subarachnoid space as well as in the glial cells associated with the periphery of the gland. In addition, after the IVT injections, rounded enlargements of the intercellular space that resembled canaliculi were filled with reaction product. In both cases (IVT and IV), the reaction product was localized to the perivascular space, to the glial cells and pinealocytes, and to the intercellular spaces. More importantly, there was specific localization of the tracers in the vacuolated pinealocytes and in the pineal concretions. The results of this study demonstrate several significant findings: 1) neither a blood-brain barrier nor a CSF-brain barrier exists in the pineal gland of the gerbil, 2) localization of the tracers in pineal concretions indicates a relationship between these structures and protein and peptide storage within the gland, and 3) the presence of the tracers within canaliculi after the IVT injections suggests a possible mode of secretion of pineal substances into the CSF.