Pinealocyte

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

Calcified inclusions in the superficial pineal gland of the mongolian gerbil, Meriones unguiculatus.

Abstract: A histological and histochemical study of the pineal gland of neonatal, juvenile and adult gerbils is described. Calcified inclusions appear within pinealocytes in the superficial pineal about the third week of age, and the incidence of inclusions increased with age until, by the eleventh week, they are found in all animals. The inclusions contain an organic matrix composed of a carbohydrate, probably an acid mucopolysaccharide, complexed to protein. Calcification does not occur in the deep pineal. The data are interpreted to indicate that the formation of calcified inclusions is a normal process within the gerbil pineal. The similarity of the process of calcification in the gerbil and in the human pineal suggests that the gerbil may be an animal of choice for the controlled study of the phenomenon of pineal calcification.

Developmental and Diurnal Dynamics of Pax4 Expression in the Mammalian Pineal Gland: Nocturnal Down-Regulation Is Mediated by Adrenergic-Cyclic Adenosine 3′,5′-Monophosphate Signaling

Abstract: Pax4 is a homeobox gene that is known to be involved in embryonic development of the endocrine pancreas. In this tissue, Pax4 counters the effects of the related protein, Pax6. Pax6 is essential for development of the pineal gland. In this study we report that Pax4 is strongly expressed in the pineal gland and retina of the rat. Pineal Pax4 transcripts are low in the fetus and increase postnatally; Pax6 exhibits an inverse pattern of expression, being more strongly expressed in the fetus. In the adult the abundance of Pax4 mRNA exhibits a diurnal rhythm in the pineal gland with maximal levels occurring late during the light period. Sympathetic denervation of the pineal gland by superior cervical ganglionectomy prevents the nocturnal decrease in pineal Pax4 mRNA. At night the pineal gland is adrenergically stimulated by release of norepinephrine from the sympathetic innervation; here, we found that treatment with adrenergic agonists suppresses pineal Pax4 expression in vivo and in vitro. This suppression a...

Hypocretin (orexin) in the rat pineal gland: a central transmitter with effects on noradrenaline‐induced release of melatonin

Abstract: Hypocretin-1 (HCRT-1) and hypocretin 2 (HCRT-2), also known as orexin-A and orexin-B, are two neuropeptides derived from the same precursor. Hypocretinergic neurons have been found exclusively in the hypothalamic dorsolateral area. These neurons are implicated in sleep and feeding through activation of specific G-protein-coupled orexin-1 and orexin-2 receptor (OR-R1 and OR-R2). The purpose of this study was to determine the existence of the HCRT peptides in the central input of the rat pineal gland. Further, OR-R1 and OR-R2 expression was determined in the pineal gland and the effect of HCRT-2 on melatonin synthesis and secretion was analysed in dissociated rat pinealocytes. A large contingent of HCRT-positive nerve fibres and terminals were observed in the epithalamus, many of which entered into the pineal parenchyma. A significant number of nerve fibres endowed with positive boutons were identified in the pineal stalk, though the number of positive fibres decreased along the extension of the stalk. So far, no positive fibres have been found in the superficial pineal gland. RT-PCR analysis revealed the expression of OR-R2 mRNA, whereas OR-R1-receptor mRNA was not detected. When tested alone, HCRT-2 had no effect on secretion of melatonin from cultured rat pinealocytes. However, HCRT-2 partially inhibited (by a maximum of 30%) the beta-adrenergic-induced melatonin secretion. The same effect was seen on activation of N-acetyltransferase activity. The distribution and the large number of HCRT-positive fibres together with the effect on noradrenaline-mediated melatonin release through specific receptors suggests that these peptides may be significant central transmitters in pineal function, probably mediating homeostatic signals to the pineal gland.

Circadian variations in pinealocytes of the Chinese hamster, Cricetulus griseus. A quantitative electron-microscopic study.

Abstract: Circadian morphological variations of pinealocytes in the superficial pineal of the Chinese hamster (Cricetulus griseus) were studied using quantitative electron-microscopic techniques. The volume of the nucleus and cytoplasm of pinealocytes exhibited similar circadian variations, with the maximum around the middle of the light period and the minimum during the first half of the dark period. Synaptic ribbons in pinealocytes were classified into three groups, type-1, −2 and −3 synaptic ribbons, which appeared as rods, round or irregular bodies and ring-shaped structures, respectively; a synaptic ribbon index was determined for the respective types. The synaptic ribbon index was expressed as the number of synaptic ribbons in the pinealocyte profile representing the cell size. The type-1 synaptic ribbon index, which was smallest during the second half of the light period, was increased during the dark period. The length of straight or slightly curved rods showed a 24-h change similar to that of the type-1 synaptic ribbon index; the length of the rods was maximal during the first half of the dark period and minimal at the end of the light period. There was no apparent circadian variation in the type-2 synaptic ribbon index. The type-3 synaptic ribbon index was higher during the light period than during the dark period; the index attained zero 3h after the onset of darkness and, thereafter, increased gradually.

Co-expression of vesicular glutamate transporters (VGLUT1 and VGLUT2) and their association with synaptic-like microvesicles in rat pinealocytes

Abstract: A vesicular glutamate transporter (VGLUT) is responsible for the accumulation of l-glutamate in synaptic vesicles in glutamatergic neurons. Two isoforms, VGLUT1 and VGLUT2, have been identified, which are complementarily expressed in these neurons. Mammalian pinealocytes, endocrine cells for melatonin, are also glutamatergic in nature, accumulate l-glutamate in synaptic-like microvesicles (SLMVs), and secrete it through exocytosis. Although the storage of l-glutamate in SLMVs is mediated through a VGLUT, the molecular nature of the transporter is less understood. We recently observed that VGLUT2 is expressed in pinealocytes. In the present study, we show that pinealocytes also express VGLUT1. RT-PCR and northern blot analyses indicated expression of the VGLUT1 gene in pineal gland. Western blotting with specific antibodies against VGLUT1 indicated the presence of VGLUT1 in pineal gland. Indirect immunofluorescence microscopy with a section of pineal gland and cultured cells indicated that VGLUT1 and VGLUT2 are co-localized with process terminal regions of pinealocytes. Furthermore, immunoelectronmicroscopy as well as subcellular fractionation studies revealed that both VGLUT1 and VGLUT2 are specifically associated with SLMVs. These results indicate that both VGLUTs are responsible for storage of l-glutamate in SLMVs in pinealocytes. Pinealocytes are the first exception as to complementary expression of VGLUT1 and VGLUT2.