Pinealocyte

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

Physical stress in the middle of the dark phase does not affect light-depressed plasma melatonin levels in humans.

Abstract: The human pineal gland has been shown to be unresponsive to stress-induced sympathetic activation during the day However, the effects of stress on human melatonin production have received little investigation at night, when the pinealocytes should be physiologically responsive to noradrenergic stimulation For this purpose, plasma melatonin and cortisol levels were measured in 7 healthy men (aged 25-34 years), both in resting condition and before and after a physical exercise performed between 2340 and 2400 h, 30 min after exposure to bright light (2,500 lx) The exercise consisted in bicycling on a bicycle ergometer at 50% of the personal maximum work capacity (MWC) for 10 min, followed by another 10 min of bicycling at 80% of the MWC The results clearly showed that physical exercise does not affect light-depressed plasma melatonin levels, whereas it clearly increased plasma cortisol concentrations (p less than 0002, two-way ANOVA with repeated measures), systolic blood pressure, pulse pressure and heart rate These findings suggest that the human pineal gland is not responsive to systemic sympathetic activation induced by physical stress even in the middle of the dark phase

Some functional aspects of the ultrastructure of rat pinealocytes.

Abstract: An analysis of more than 75000 electron micrographs from 84 intact control and 167 experimental male rats divided into 11 groups subjected to various treatments, was performed in the present study, a special attention being paid to the relation of cytoplasmic organelles to the processes of synthesis and secretion of pinealocytes. From these observations the following conclusions have been drawn: 1. specific pineal cells - the pinealocytes - show several attributes of metabolically active endocrine cells; 2. at least two probably intimately related secretory processes are present in the rat pinealocytes; 3. several cytoplasmic structures may be involved in the secretory mechanism of the rat pinealocytes.

Cholinergic signaling in the rat pineal gland

Abstract: 1. Innervation of the mammalian pineal gland is mainly sympathetic. Pineal synthesis of melatonin and its levels in the circulation are thought to be under strict adrenergic control of serotoninN-acetyltransferase (NAT). In addition, several putative pineal neurotransmitters modulate melatonin synthesis and secretion.

Structural dissimilarities in different regions of the pineal gland of Pirbright white guinea-pigs.

Abstract: In the present study, the proximal, intermediate and distal parts of dumbbell-shaped pineal glands of Pirbright White guinea-pigs were investigated with respect to structural dissimilarities. The most conspicuous difference was that while in the proximal part the pinealocytes were arranged in a random fashion, the intermediate and distal regions, except a small ventral area in the latter, exhibited a prominent follicular arrangement of the pinealocytes. Concretions were restricted to the subcapsular region of the intermediate part, whereas cells with hyperchromatic nuclei increased in number in an anterior-posterior direction. In males, pinealocyte nuclear size did not differ significantly in the regions investigated, whereas in females the karyometric results were much more heterogeneous. Exposure of male guinea-pigs to continuous illumination for 45 days resulted in (i) a 25% decrease of pineal volume, the intermediate area being relatively little affected, (ii) an increase in the number of follicles and (iii) a decrease in pinealocyte nuclear size, especially in a ventral zone of the proximal part of the pineal gland.