Pinealocyte

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

Pinealocytes contacting the cerebrospinal fluid of the suprapineal recess in the Mongolian gerbil (Meriones unguiculatus).

Abstract: The pineal system of the Mongolian gerbil (Meriones unguiculatus) was investigated by light and electron microscopy, special attention being paid to the sites of contact with the ventricular system. The results reveal that the pineal system of this species has a specific topographical relationship to the suprapineal recess of the third ventricle. The dorsal side of the proximal part of the pineal system forms the floor and the caudal wall of this recess. Here, a consistent and relatively large area lacks an ependymal lining, enabling pinealocytes to come into direct contact with the cerebrospinal fluid (CSF). This area is assumed to be the morphological correlate of a close functional interrelationship between the pineal tissue and the CSF.

Distribution of two forms of somatostatin in the brain, anterior intestine, and pancreas of adult lampreys (Petromyzon marinus).

Abstract: The distribution of two major immunoreactive forms of somatostatin, somatostatin-14 and somatostatin-34, within the brain, pancreas and intestine of adult lampreys, Petromyzon marinus, was identified using antisera raised against these peptides. Immunostaining of the brain is similar in juveniles and upstream migrants, and somatostatin-14 is the major somatostatin form demonstrated. A few somatostatin-34-containing cells are localized within the olfactory bulbs, thalamus and hypothalamus, but cells immunoreactive to anti-somatostatin-34 in the hypothalamus and thalamus do not co-localize somatostatin-14. Immunostaining of pinealocytes within the pineal pellucida with anti-somatostatin-14 may infer a novel function for this structure. Somatostatin-14 and somatostatin-34 are co-localized within D-cells of the cranial pancreas and caudal pancreas of juveniles and upstream migrants. Numerous somatostatin-34-immunoreactive cells are distributed within the epithelial mucosa of the anterior intestine but not all of these cells cross-react with anti-somatostatin-14. It appears that somatostatin-34 is the major somatostatin in the pancreo-gastrointestinal system of adult lampreys.

Ultracytochemical Localization of Calcium in the Superficial Pineal Gland of the Mongolian Gerbil

Abstract: In order to demonstrate fine localization of Ca2+ in the superficial pineal gland of Meriones unguiculatus, the pyroantimonate technique was employed. Control experiments were performed with EGTA and analysis of obtained reaction product using an energy-dispersive x-ray microanalysis. Precipitates of calcium antimonate were formed almost exclusively in swollen clear pinealocytes, in and along their cell membranes, over their nuclei, in mitochondria, the Golgi apparatus, endoplasmic and integrade reticulums. acervuli, in vesicles surrounding synaptic bars, cytoplasmic matrix, and flocculent extracellular material. It has been concluded that the swollen pinealocytes represent a degenerative cell form probably occurring by impairment of plasmalemmal Ca2+-ATPase's ability to eliminate Ca2+ ion from the cell, with consecutive increase of calcium in the cytoplasmic matrix, followed by increase of intramitochondrial Ca2+ concentration, gradual arrest of mitochondrial function, depolymerization of cytoskeletal microtubuli, loss of the cell form, and cell death. Decrease of function of pinealocyte plasmalemma seems to be related to aging.

Demonstration of circadian rhythm in granular vesicle number in pinealocytes of mice and the effect of light: semi-quantitative electron microscopic study.

Abstract: Adult (70-100 days) male dd-mice were killed at 7 a.m., 1 p.m., 7 p.m. and 1 a.m. under controlled daily photoperiods (L: 7 a.m.-7 p.m.) and temperature, and at 6, 12 and 18 hours after exposure to continuous lighting which started at 7 p.m. Montage photographs were made from electron micrographs at x8200 based on mesh hole areas, using either 150 or 300 meshes. The number of granular vesicles per unit area was counted (GV Score). The GV Score in distal, mid and proximal portions of the body of the pineal gland showed marked 24 hour change, with high values in the late light period and low values in the dark period. The GV Score in the Golgi region showed a 24 hour change with a smaller amplitude. A peak level was attained at mid-light period and low values during a dark period. Additional lighting inhibited the nocturnal decrease in the GV Score in both the whole cytoplasm and the Golgi region, resulting in a slight increase. It is concluded that the number of granular vesicles in mouse pinealocytes (and in their Golgi regions) follows a 24 hour rhythm, and that the nocturnal decrease in the vesicle number depends upon darkness.

Cyclic GMP-activated channels of the chick pineal gland: effects of divalent cations, pH, and cyclic AMP.

Abstract: Chick pineal cells maintained in dissociated cell culture express an intrinsic photosensitive circadian oscillator, but the mechanisms of phototransduction in avian pinealocytes are not fully understood. In this study, we have used inside-out patches to examine the characteristics of cyclic GMP-activated channels of chick pinealocytes in more detail, concentrating on the effects of factors known to modulate the secretion of melatonin and/or the function of circadian pacemakers. In most patches, the predominant conductance state was 19 pS in symmetrical 145 mM NaCl. But in some patches, a second cyclic GMP-activated channel with a unitary conductance of 29 pS was also present. The current flowing through cyclic GMP-activated channels was not affected by application of salines containing 1 μM Ca2+ to the cytoplasmic face of the patch membrane. By contrast, application of 1 mM Ca2+ caused a partial reduction in cyclic GMP-activated current at all membrane potentials. Application of 1–5 mM Mg2+ ions caused a virtually complete blockade of current at positive membrane potentials, but caused only a small decrease in current at negative membrane potentials. No obvious differences in the gating of cyclic GMP-activated channels were observed in pH 8.2, 7.4 or 6.2 salines. Application of salines containing 100 μM, 500 μM, or 1 mM cyclic AMP did not cause activation of the channels, but 5 mM cyclic AMP evoked a low level of channel activity. Application of 5 mM but not 100 μM cyclic AMP decreased the probability of channel activation caused by 20–100 μM cyclic GMP and also increased the percentage of openings to an 11 pS subconductance state. Thus, cyclic AMP acts as a weak partial agonist. Nevertheless, the gating of these channels does not seem to be controlled directly by physiologically relevant changes in intracellular Ca2+, pH, or cyclic AMP.