Search results for "Pineal gland"

The columnar gene vnd is required for tritocerebral neuromere formation during embryonic brain development of Drosophila.

2006

International audience; In Drosophila, evolutionarily conserved transcription factors are required for the specification of neural lineages along the anteroposterior and dorsoventral axes, such as Hox genes for anteroposterior and columnar genes for dorsoventral patterning. In this report, we analyse the role of the columnar patterning gene ventral nervous system defective (vnd) in embryonic brain development. Expression of vnd is observed in specific subsets of cells in all brain neuromeres. Loss-of-function analysis focussed on the tritocerebrum shows that inactivation of vnd results in regionalized axonal patterning defects, which are comparable with the brain phenotype caused by mutatio…

Perspectives of Comparative Anatomy of the Mammalian Pineal Gland

1983

As the precise role of the pineal gland has been established in a few mammalian species only, every effort should be made to elucidate the function of this potentially important neuroendocrine organ in as many species as possible. One way in which the morphologist can contribute to reach this goal is to carry out comparative studies. Comparative anatomical studies with respect to the pineal gland can be, and should be, carried out at different structural levels: (a) At the gross anatomical level; (b) at the tissue level; (c) at the cellular level, and (d) at the level of cell organelles.

Differential Effects of Fluvoxamine and Other Antidepressants on the Biotransformation of Melatonin

2001

Melatonin, the predominant product of the pineal gland, is involved in the maintenance of diurnal rhythms. Nocturnal blood concentrations of melatonin have been shown to be enhanced by fluvoxamine, but not by other serotonin reuptake inhibitors. Because fluvoxamine is an inhibitor of several cytochrome P450 (CYP) enzymes, the authors studied the biotransformation of melatonin and the effects of fluvoxamine on the metabolism of melatonin in vitro using human liver microsomes and recombinant human CYP isoenzymes. Melatonin was found to be almost exclusively metabolized by CYP1A2 to 6-hydroxymelatonin and N-acetylserotonin with a minimal contribution of CYP2C19. Both reactions were potently in…

Dopaminergic agents acting at D1 and D2 receptor sites differently affect melatonin synthesis in rat pineal gland during night.

2001

Day-night differences in the sensitivity of adrenoceptors in the Syrian hamster pineal gland: an in vivo iontophoretic study.

1989

Abstract Investigations on the regulation of pineal melatonin synthesis in the Syrian hamster revealed distinct differences compared to this well-understood mechanism in rat. E.g., a circadian profile of pineal norepinephrine (NE) is absent, there is no β-adrenoceptor sensitivity during daytime and adrenergic receptor supersensitivity is not easily achieved. To elucidate the action of NE on pineal receptor sites, the effects of iontophoretic application of adrenergic compounds on spontaneous electrical discharge rates of pinealocytes were investigated during day- and nighttime. Following application of either NE, isoproterenol or clonidine, cells were activated, inhibited or not affected. W…

Changes in the Three Dimensional Structure of Synaptic Ribbons in the Pineal Gland of the Guinea-Pig Caused by Constant Light

1997

Synaptic bodies (SBs) are dynamic synaptic organelles of afferent synapses of the retina, inner ear, lateral line organ and pineal gland in vertebrates. When investigated in a transmission electron microscope, their electron-dense rod-like, round or irregular profiles are surrounded by electron-lucent vesicles. The three-dimensional structure of pineal SBs is not precisely known. Pineal glands of two guinea-pigs (one kept under an LD cycle of 12:12 h; one kept in constant light for 8 weeks) were investigated. SBs were reconstructed in three dimensions to visualise morphological changes in constant light. Transmission electron microscope micrographs from up to 18 serial sections with a known…

Circadian and Infradian Activity Rhythms in the Mammalian Pineal Body

1982

The neuroendocrine nature of the pineal organ is well established. Linked to the optic system via postganglionic sympathetic fibres coming from the superior cervical ganglia, the parenchymal cells of the pineal synthesize serotonin from tryptophan and convert it to melatonin, the most widely studied pineal substance, and other indoleamines. Melatonin synthesis is stimulated by noradrenaline released from intrapineal sympathetic nerve fibres, involving β-adrenergic mechanisms and the adenyl cyclase-cAMP-system. The rate-limiting enzyme of melatonin formation is serotonin-N-acetyltransferase (NAT) that converts serotonin to N-acetylserotonin. Hydroxyindole-O-methyltransferase (HIOMT) catalyze…

A differential role of CREB phosphorylation in cAMP-inducible gene expression in the rat pineal

2000

In the rat pineal gland cAMP mediates nocturnal induction of the enzyme arylalkylamine N-acetyltransferase (AA-NAT) as well as of transcription factors such as inducible cAMP early repressor (ICER), Fos-related antigen-2 (Fra-2) and JunB. Cyclic AMP stimulates the phosphorylation of the DNA binding protein cAMP response element binding protein (CREB). While cAMP-induced CREB phosphorylation appears to be a prerequisite for AA-NAT and ICER gene expression, it is not known whether CREB phosphorylation accounts for the full cAMP response of the two genes. Furthermore, the significance of CREB phosphorylation in cAMP-activated Fra-2 and JunB transcription is unknown. In the present in vitro stu…

Expression of Nitric Oxide Synthase I Determines the Strength of Adrenergic Cyclic GMP Response in the Rat Pineal Gland

1997

In the rat pineal gland the adrenergic cGMP response is not static but changes during postnatal development and depends on environmental lighting conditions. Since the adrenergic cGMP transduction is mediated by stimulation of the enzyme nitric oxide synthase I (NOS I), we investigated whether changes in the strength of adrenergic cGMP response coincide with the expression of NOS I. Using immunoblot analysis, we found that the increase in adrenergic cGMP transduction in the second postnatal week coincides with enhanced NOS I expression. Similarly, we observed that changes in the intensity of adrenergic cGMP transduction under different environmental lighting conditions correspond to NOS I e…

Electrophysiology of the Mammalian Pineal Gland: Evidence for Rhythmical and Non-Rhythmical Elements and for Magnetic Influence on Electrical Activity

1982

Although the mammalian pineal gland has been extensively studied by biochemical, pharmacological and morphological techniques, the precise nature of the intrinsic cells, the pinealocytes, was unknown for a long time. Biochemically the pinealocyte has been shown to be an endocrine cell synthesizing melatonin and other hormones. In view of the importance of the mammalian pineal as a neurotransducer, and of the limited usefulness of the methods mentioned, an attempt was made to characterize the cells electro-physiologically.