Pinealocyte

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

Ultrastructural study of the distribution of calcium in the pineal gland of the rat subjected to manipulation of the photoperiod.

Abstract: Using the pyroantimoniate technique, a study was conducted at electron microscope level on the distribution of the calcium ion in the pineal glands of normal adult Sprague-Dawley rats with initial weights of 150–200 g subjected to a 12:12 light dark cycle and others under the same conditions were subjected to modifications in the noradrenergic signal, such as continuous illumination over 7 days, blinding by bilateral enucleation (7 or 90 days) before sacrifice and bilateral superior cervical gangliectomy at 21 days before sacrifice. All the animals were sacrificed by decapitation, half of them at midday and the other half at midnight. Abundant fine precipitations of calcium were found in the intercellular spaces of the pineal glands of the normal rats. By contrast, in the gangliectomized animals subjected to constant illumination and chronic binding these precipitations were few in number. Additionally, two types of pinealocytes were observed regarding the distribution and concentration of intracytoplasmic calcium in both the normal and experimentally manipulated animals. Type I correspond to the classic light pinealocytes, with an absence of intracytoplasmic precipitations, although in the normal and gangliectomized animals sacrificed at midnight it was possible to observe fine deposits inside the mitochondrial matrix. Type II correspond to the classic dark pinealocytes, with a dense cytoplasmic matrix and numerous deposits of intracytoplasmic and intranuclear calcium; these were never seen in the type I pinealocytes.

Day-night changes in the ultrastructure of pinealocytes in the Syrian hamster: a quantitative study.

Abstract: The ultrastructure of pinealocytes was studied in Syrian hamsters maintained under 12:12 light: dark cycle, both during the daytime (1300h) and at night (0100h). At night the pinealocytes showed ultrastructural features indicating an increased metabolic and synthetic activity of these cells. It was expressed by higher relative volumes of mitochondria, lysosomes, lipid droplets, granular endoplasmic reticulum and vacuoles containing flocculent material at night in comparison with those during the daytime. By contrast, the number of the dense-core vesicles, both in the cell body and in the endings of pinealocyte processes was higher during the daytime than at night. Quantitative morphological results correlate with the well known nocturnal enhancement in biochemical activity of the pineal gland, especially the circadian rhythm of the secretion of the pineal hormone-melatonin.

Influence of a short light pulse at night on the ultrastructure of the rat pinealocyte: a quantitative study

Abstract: Although it is generally known that light strongly influences N-acetyltransferase activity and melatonin production in the pineal gland, little information is available concerning morphological changes following light exposure. As exposure of rats to a short light pulse at night rapidly depresses melatonin synthesis, we decided to determine whether this experimental condition produces rapid changes in the pinealocyte organelles. A 30-min light pulse at night (six hours after lights out) provoked rapid changes in the relative volumes of some pinealocyte organelles. The volume fractions of mitochondria, Golgi apparatus and lipid droplets, and the numbers of dense-core vesicles and “synaptic” ribbons decreased, whereas the volume fraction of lysosomes increased. There were no differences in the volumes of granular endoplasmic reticulum and vacuoles containing flocculent material in those animals exposed to light compared with control animals. These results indicate that a short light pulse at night causes ultrastructural changes that can be interpreted as morphological features of diminished activity of pinealocytes.

Effects of hereditary hypopituitarism and ectopic pituitary transplants on pinealocytes of the mouse: a quantitative ultrastructural study.

Abstract: The ultrastructure of the pinealocytes of Snell dwarf mice (dw/dw) was examined morphometrically and compared with that of both phenotypically normal (dw/+ or +/+) animals of the same strain and dwarf mice with ectopic pituitary grafts. Ultrastructural features characteristic of diminished activity of the pinealocytes were observed in dwarf mice as compared with controls. Ectopic pituitary grafts induced morphological signs of activation of the pinealocytes in this mutant. The results of the present study demonstrate the influence of the adenohypophysis on the pineal gland and these data, together with the known influence of the pineal gland on the adenohypophysis, support the existence of a reciprocal relationship between these two glands.

Ultrastructure of the rat pineal gland grafted under the kidney capsule.

Abstract: Pineal glands were grafted under the kidney capsule of mature male rats for periods of 20, 40, 60 and 100 days. Each grafted gland was then excised and divided into two halves. One half was processed for conventional electron microscopy and the other was fixed in aldehydes and then incubated in a zinc iodide-osmium tetroxide mixture at pH 4.4 (A-ZIO-4.4). During the forty days following the operation pinealocytes showed the typical ultrastructural features associated with cells with a high protein and/or peptide secretory activity. On the other hand, during this period, the number of granular vesicles decreased progressively. From day 40 on, the grafted pinealocytes lacked granular vesicles. During the second half of the experimental period the ultrastructure of the pinealocytes indicated that their secretory activity was considerably decreased. During the acute phase of the experimental period numerous structures regarded as the tip of growing axons as well as typical nerve fibres appeared around blood vessels and within the parenchyma of the grafted gland. In the transplanted tissue obtained 60 and 100 days after the operation the growth cones were scarce, whereas typical nerve endings became numerous. These endings contained small clear vesicles which reacted positively when the tissue was treated with A-ZIO-4.4. The secretory activity of the grafted pineal gland and the nature of the nerve fibres which innervate the graft are discussed.