Effect of photoperiod on early changes in the neonatal rat pineal gland

Summary It is concluded that photoperiod has little direct effect on the mitotic activity or morphological development of the pineal parenchymal cell of the rat in the early postnatal period.     

Aromatization of androgens to estrogens by the rat pineal gland

Résumé Des homogénats de glande pineale de rat mâle métabolisèrent de la testostérone-C¹⁴ in vitro en stradiol-C¹⁴ et en strone-C¹⁴. Les métabolites furent identifiés chiomatographiquement et dans le cas de l'stradiol par recristallisation à activité spécifique constante. La conversion de la testostérone en stradiol fut de 0.19–0.27% et en strone de 0.02–0.04%. Ces résultatsci indiquent que la pinéale ressemble à d'autres régions du cerveau soumises au contrôle de la sécrétion de gonadotropines.

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These studies were supported by grants from the Comisión Nacional de Estudios Geo-Heliofísicos, Argentina and the World Health Organization. D.P.C. and C.A.N. are established investigators of the Comisión Nacional de Estudios Geo-Heliofísicos. J.M.R. is an established investigator of the Consejo Nacional de Investigaciones Cientificas y Técnicas, Argentina.     

Concrement formation encountered in the rat pineal gland

Summary Morphological evidence is given for the concrement formation encountered in the rat pineal gland, the occurrence of which has not been reported so far (for the rat).     

Evidence for in vitro release of neurophysin by the rat pineal gland

Summary Cultured pineal ependymal cells from rat fetuses release into their incubation media immunoreactive neurophysin. The presence of neurophysin was assessed by radioimmunoassay. The culture medium was found to contain 440 pg neurophysin per mg protein.     

Scanning electron microscope observations of the canaliculi in the rat pineal gland

Summary The scanning electron microscope has shown rich ramifications of the parenchymal canaliculi forming a three-dimensional network of anastomosing intercellular spaces in the rat pineal gland. Every pineal cell seems to be in contact with this channel system. An abundance of cellular processes can be found within the canaliculi which may play an important role in the histophysiology of the pineal body. Dedicated to Prof. Dr. med.W. Bargmann on the occasion of his 70th birthday.     

Ultrastructural evidence of a secretory process in the rat pineal gland.

Pericapillar spaces of the rat pineal gland belong to the most active sites of this organ. Neighborhood of sympathetic nerve endings, capillaries and pinealocyte processes facilitates possibly the synthesis and the secretion of methoxyindoles. Lipid droplets migrate through the pinealocyte cellular processes towards the terminal enlargement or poles, where they are secreted into the pericapillar space, and the possibility that indoleamines are included in the lipid droplets has been discussed.     

Scanning electron microscope observations of the canaliculi in the rat pineal gland.

The scanning electron microscope has shown rich ramifications of the parenchymal canaliculi forming a three-dimensional network of anastomosing intercellular spaces in the rat pineal gland. Every pineal cell seems to be in contact with this channel system. An abundance of cellular processes can be found within the canaliculi which may play an important role in the histophysiology of the pineal body.     

Electrophysiological evidence for the action of light on the pineal gland in the rat

Résumé La lumière a un effet inhibiteur sur l'activité électrique tonique spontanée de l'épiphyse du rat, enregistrée dans l'obscurité. Les éléments photosensibles se trouvent au niveau des yeux. Le fait que la réponse a été bloquée par le chlorure de hexamethonium suggère qu'elle est transmise à l'épiphyse par les nerfs sympathiques postganglionnaires.     

Melatonin biosynthesis in the mammalian pineal gland

Rhythmic production of melatonin by the mammalian pineal occurs in response to noradrenergic stimulation which produces a cascade of biochemical events within the pinealocyte. In the rat, massive changes in NAT activity result from an increase in intracellular c-AMP levels produced by a synergistic interaction whereby an alpha 1 activation amplifies beta-adrenergic stimulation. The intracellular events mediating this effect are described. A major aspect of the temporal control of melatonin production is the programmed down-regulation of responses to noradrenergic stimulation once the initial surge of c-AMP is produced. Noradrenergic activation of the gland also influences other enzymic functions, including tryptophan hydroxylase and HIOMT activities, and produces a dramatic increase in intracellular c-GMP levels. Other neurotransmitters and neuropeptides, e.g. VIP, may also influence pineal function and comparisons are made between the rat, the subject of the bulk of experimental studies, and other species.     

Melatonin biosynthesis in the mammalian pineal gland

Summary Rhythmic production of melatonin by the mammalian pineal occurs in response to noradrenergic stimulation which produces a cascade of biochemical events within the pinealocyte. In the rat, massive changes in NAT activity result from an increase in intracellular c-AMP levels produced by a synergistic interaction whereby an ₁ activation amplifies -adrenergic stimulation. The intracellular events mediating this effect are described. A major aspect of the temporal control of melatonin production is the programmed down-regulation of responses to noradrenergic stimulation once the initial surge of c-AMP is produced. Noradrenergic activation of the gland also influences other enzymic functions, including tryptophan hydroxylase and HIOMT activities, and produces a dramatic increase in intracellular c-GMP levels. Other neurotransmitters and neuropeptides, e.g. VIP, may also influence pineal function and comparisons are, made between the rat, the subject of the bulk of experimental studies, and other species.     

Ultrastructure of the pineal gland after hypohysectomy

Résumé Nous avons étudié les modifications de l'ultrastructure de la glande pinéale du rat après hypophysectomie et constaté: (a) une atrophie du réticulum endoplasmique, (b) réduction des ribosomes, (c) dépletion du matériel sécrétoire des granules, (d) altération des mitochondries, (e) réduction dans le volume des noyaux et des nucléoles et (f) un agrandissement de l'espace périvasculaire. Il est très probable que l'hypophyse antérieure est nécessaire pour maintenir la structure et la sécrétion de la glande pinéale, mais le mécanisme par quoi s'exerce ce contrôle reste encore inconnu.