Pinealocyte

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

Does the Manatee Have a Pineal Body

Abstract: The brain of an adult, female manatee (Trichechus manatus) was prepared for histological examination of the region of the diencephalon and mesencephalon, where the pineal body typically would be located. Careful examination of hematoxylin-eosin stained, interrupted serial microtomy sections revealed that this animal has a tubular epiphyseal recess apparently lacking organic pineal differentiation. There was no cytological evidence of pinealocytes in the vicinity of the atypical pineal rudiment.

Ultrastructure of the pineal body of the common vampire bat, Desmodus rotundus.

Abstract: The type AB pineal body of the common vampire bat, Desmodus rotundus was recessed and lobulated, was extensively vascularized and intimately related to great veins, and was unassociated with the epithalamic region. The habenular and the posterior commmissures coursed anteriorly and were unassociated with the pineal. The saccular suprapineal recess of the third ventricle extended dorsally juxtaposed to the pineal body. These anatomical features are likely to make pinealectomies in the vampire more difficult to manage. The pineal parenchyma consisted of light pinealocytes surrounded by canaliculi of various sizes, often transmitting unmyelinated nerve fibers and glial processes. Desmosomes were common. The pinealocyte nuclei were large and highly infolded; characteristic cytoplasmic constituents included abundant dilated Golgi complexes associated with clear vesicles, numerous polyribosomes, few single cisternae of ribosome-studded rough endoplasmic reticulum, mitochondria, and occasional multivesicular bodies and lysosomes. Almost all pinealocytes exhibited centrioles and some, in addition, displayed basal bodies but rarely ciliary shafts. A conspicuous feature of the pinealocyte cytoplasm was the presence of branched bundles of intermediate filaments, especially in the perinuclear zone. Siderotic macrophages, lipofuscin-pigment-containing phagocytic cells, mast cells, myelin bodies, and both fenestrated and continuous capillaries were present. The perivascular compartment was densely packed with unmyelinated nerve bundles containing small to large fibers exhibiting axoaxonic densities. Other constituents of the perivascular compartment were club-shaped pinealocyte processes filled with clear vesicles, microtubules, an occasional mitochondrion, glial processes, and collagen fibers. “Synapselike” contacts were observed between the axons and pinealocyte processes. Abundant pinocytotic vesicles in the capillary endothelium indicated active pinocytosis. Myelinated nerve fibers were lacking. The pineal ultrastructure of Desmodus is in part unlike that reported for other mammals, including bats.

Biochemical and ultrastructural approaches to the onset of the pineal melatonin rhythm in the rat.

Abstract: To determine the pineal gland content of melatonin during rat development and the onset of the circadian rhythm, a biochemical and ultrastructural experimental model was designed. Body and pineal gland weights and DNA and protein contents of the pineal glands increased rapidly during ontogenic development. No significant differences in the values of these parameters were observed when the data were obtained during the day or at night. Pineal melatonin content as expressed by pineal gland or by micrograms of DNA, was very small in 21-day-old fetuses and 5- and 10-day-old suckling rats and the values determined were similar for both day and night. However, in 20-day-old suckling and adult rats higher melatonin concentrations and significant differences between the values obtained during the day and at night were observed. The onset of the circadian melatonin rhythm coincided with the time at which the components involved in melatonin synthesis reached adult levels and pinealocytes adopted an adult morphological appearance as observed with the electron microscope. These results indicate that the appearance of a circadian melatonin rhythm in the rat pineal gland is delayed until the end of the suckling period, although the transfer of melatonin from the mother to the pups may be important for postnatal reproductive and somatic development.

Homeobox genes in melatonin-producing pinealocytes: Otx2 and Crx act to promote hormone synthesis in the mature rat pineal gland.

Abstract: Homeobox genes encode transcription factors that regulate developmental processes; however, in the pineal gland, a neuroendocrine organ responsible for nocturnal melatonin synthesis, expression of the homeobox genes Otx2 (orthodenticle homeobox 2) and Crx (cone-rod homeobox) persists postnatally. We here show that OTX2 and CRX are exclusively present in melatonin-producing pinealocytes of the rat pineal gland. To understand the roles of Otx2 and Crx in the mature pineal gland, we used siRNA technology in cultured rat pinealocytes with the nocturnal situation mimicked by adding norepinephrine to the culture media. siRNA-induced knockdown of Otx2 was found to reduce expression levels of the enzymes involved in melatonin synthesis at both transcript and protein levels. Similar results were obtained when knocking down Crx. Knocking down Otx2 and Crx simultaneously produced an even larger reduction in both transcript and protein levels of the melatonin-producing enzymes and also reduced the levels of melatonin released to the culture media. These results suggest that Otx2 and Crx, both alone and in combination, act to control pineal melatonin synthesis.

Morphometric analysis of the pineal complex of the golden hamster over a 24-hour light:dark cycle: II. The deep pineal in untreated and optically enucleated animals.

Abstract: The deep pineal gland of golden hamsters was morphometrically analyzed and quantitatively compared with the superficial pineal under a 14:10 lighting regime and following blinding. The deep pineal comprised 6-10% of the total pineal parenchymal tissue. Pinealocytes of the deep gland were smaller than the cells of the superficial pineal and showed a greater percent volume of Golgi bodies, rough endoplasmic reticulum, and dense-cored vesicles. Twenty-four-hour rhythms in nucleoli and Golgi bodies were found in deep pinealocytes. These rhythms were out of phase with comparable rhythms in the superficial pineal gland, suggesting that distinct subpopulations of pinealocytes are present within the respective parts. Blinding resulted in decreased nuclear and nucleolar volume, while the amount of smooth endoplasmic reticulum, Golgi bodies, dense bodies, and dense-cored vesicles increased significantly. Marginal increases were seen in mitochondria and lipid droplets. The greater abundance of those organelles involved in synthesis and secretion suggests enhanced cellular activity after blinding. Many of the morphological responses are similar to alterations in the pinealocytes of the superficial pineal following optic enucleation.