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The main function of the rat pineal gland is to transform the circadian rhythm generated in the suprachiasmatic nucleus into a rhythmic signal of circulating melatonin characterized by a large nocturnal increase that closely reflects the duration of night period. This is achieved through the tight coupling between environmental lighting and the expression of arylalkylamine- N-acetyltransferase, the rhythm-controlling enzyme in melatonin synthesis. The initiation of Aanat transcription at night is controlled largely by the norepinephrine-stimulated phosphorylation of cAMP response element-binding protein by protein kinase A. However, to accurately reflect the duration of darkness, additional signaling mechanisms also participate to fine-tune the temporal profile of adrenergic-induced Aanat transcription. Here, we reviewed some of these signaling mechanisms, with emphasis on the more recent findings. These signaling mechanisms can be divided into two groups: those involving modification of constitutively expressed proteins and those requiring synthesis of new proteins. This review highlights the pineal gland as an excellent model system for studying neurotransmitter-regulated rhythmic gene expression. [ABSTRACT FROM AUTHOR]

Background. Pineal and adrenocortical cell morphology, dynamics, hormonal analysis and function in response to both natural and synthetic corticoids awaits in depth investigation in mammals. Aim. To investigate the pineal responsiveness to corticoid treatment from combined morphological and hormonal studies in postpubertal male mice. Material and methods. Three groups, each with 14 mice were used as control (C) or treated with the natural corticoid, hydrocortisone (HYC) at a dose of 4 mg/100 g.b.w. and synthetic corticoid, dexamethasone (DEX) at a dose of 4 mg/100 g.b.w. for ten consecutive days. Results. The treatment induced inverse changes in pineal-adrenocortical karyomorphology, cell proliferation (mitotic percentage M%) and hormonal milieu. Whereas both these corticoids caused pineal stimulation as evidenced from significantly increased nuclear diameter (μm) values (C 3.35 ± 0.05, HYC 4.77 ± 0.02, DEX 4.59 ± 0.04, p<0.001) and cell proliferation (M%) (C 1.11 ± 0.09, HYC 1.59 ± 0.07, DEX 1.44 ± 0.05, p<0.01), the changes induced in adrenocortical nuclear diameter in all the zones (p<0.001), cell proliferation (M%) (C 1.38 ± 0.05, HYC 0.53 ± 0.06, DEX 0.70 ± 0.05, p<0.001) and decreased content of adrenal corticosterone (C 0.24 ± 0.03, HYC 0.13 ± 0.01, p<0.001 DEX 0.15 ± 0.02, p<0.01) were those of adrenocortical inhibition. Conclusion. There exists an inverse relationship between the pineal and adrenocortical functions in post pubertal male mice (Mus musculus). [ABSTRACT FROM AUTHOR]

Schwannomas arising from the trochlear nerve are very rare and to our knowledge, less than 35 histologically documented cases have been reported in the literature. There are no reports of a schwannoma in the pineal region. We report a 24-year-old woman who underwent a para-occipital trans-tentorial approach and gross total excision of a pineal region schwannoma arising from the trochlear nerve. This is the first such reported case. [ABSTRACT FROM AUTHOR]

The relationship between pineal and thyroid in response to the adrenocortical modulation is poorly understood. In the present study post pubertal male rats were treated with natural and synthetic corticoids and an antiadrenal agent mitotane. Hydroxycortisone was administered at a dose of 4 mg / 100 g b.w., dexamethasone 2 mg / 100 g b.w. and mitotane 3 mg / 100 g b.w. for fifteen consecutive days. Our data revealed that both the corticoids, hydroxycorticosterone and dexamethasone induced hyperactivity of pineal and thyrofollicular cell morphology. The functional relation between the cells of the pineal parenchyma and thyroid follicles were noted. Similar results were induced by mitotane, an antiadrenal agent. It is concluded, that our present study indicates a mutual relationship between the pineal and the thyroid gland karyomorphological and functional parameters in response to corticoids and an antiadrenal agent in post pubertal male rat ( Rattus rattus). [ABSTRACT FROM AUTHOR]

Background: Melatonin reduces the development of breast cancer interfering with oestrogen-signalling pathways, and also inhibits aromatase activity and expression. Our objective was to study the promoters through which melatonin modifies aromatase expression, evaluate the ability of melatonin to regulate cyclooxygenases and assess whether the effects of melatonin are related to its effects on intracellular cAMP, in MCF-7 cells.Methods: Total aromatase mRNA, aromatase mRNA promoter regions and cyclooxygenases mRNA expression were determined by real-time RT-PCR. PGE(2) and cAMP were measured by kits.Results: Melatonin downregulated the gene expression of the two major specific aromatase promoter regions, pII and pI.3, and also that of the aromatase promoter region pI.4. Melatonin 1 nM was able to counteract the stimulatory effect of tetradecanoyl phorbol acetate on PGE(2) production and inhibit COX-2 and COX-1 mRNA expression. Melatonin 1 nM elicited a parallel time-dependent decrease in both cyclic AMP formation and aromatase mRNA expression.Conclusions: This study shows that melatonin inhibits aromatase activity and expression by regulating the gene expression of specific aromatase promoter regions. A possible mechanism for these effects would be the regulation by melatonin of intracellular cAMP levels, mediated by an inhibition of cyclooxygenase activity and expression. [ABSTRACT FROM AUTHOR]

Central nervous system germ cell tumors are neoplasms that affect children and young adults. They are subclassified into germinoma and nongerminomatous germ cell tumors. The latter include teratoma (mature teratoma, immature teratoma, teratoma with malignant transformation), choriocarcinoma, embryonal carcinoma, yolk sac tumors, and mixtures of these entities. Germinoma with syncytiotrophoblastic giant cells is a variant of germinoma. Germinomas respond well to radiation therapy, but late sequelae due to irradiation have been reported. The results of radiation treatment alone for nongerminomatous germ cell tumor are not satisfactory. Combination radiochemotherapy has been applied, and this yields a good outcome with less toxicity for germinomas and better survival of nongerminomatous germ cell tumors. This article also discusses other issues, including the controversy regarding spinal irradiation and the treatment of recurrent disease. [ABSTRACT FROM AUTHOR]

Papillary glioneuronal tumor (PGNT) is a newly described mixed glioneuronal tumor, recently included in the World Health Organization classification of central nervous system tumors. We report morphologic and immunohistochemical characteristics PGNT of the pineal region extending into the third and lateral ventricles in a four-year-old male child and reviewed all the cases reported in the international literature till date. In this child the diagnosis of PGNT was established by endoscopic biopsy and squash smear examination. [ABSTRACT FROM AUTHOR]

Abstract: Secretion of melatonin by the mammalian pineal gland is primarily regulated by the release of norepinephrine (NE) from sympathetic nerve terminals that originate from the superior cervical ganglia. Peptidergic nerves that originate in the perikarya located in the sensory trigeminal ganglia also innervate the pineal gland. Some of these peptidergic nerve fibers contain substance P. Previously, we have characterized neurokinin 1 type substance P receptors in the pineal gland. However, the function of this receptor in the pineal gland remains unclear. Here, we examined the modulatory effect of substance P on rat pineal NE transmission. We show that at the presynaptic level, substance P stimulates the KCl-induced [3H]NE release from the pineal nerve ending. However, we found that substance P did not affect the basal levels of either arylalkylamine-N-acetyltransferase (AANAT) activity or melatonin secretion in rat pineal organ cultures. However, in the presence of NE, substance P inhibited the NE-induced increase in AANAT activity and melatonin secretion. This is the first time that a function for substance P in the mammalian pineal gland has been demonstrated. [Copyright &y& Elsevier]

Abstract: The aim of this work was to confirm previous findings suggesting that the eyes are required for night-time melatonin production in Nile tilapia and further characterise this divergent circadian organisation. To do so, melatonin levels were firstly measured in eyecups and plasma to determine circadian patterns of melatonin production. Secondly, the effect of partial ophthalmectomy on the suppression of melatonin production was determined in vivo as well as ex vivo pineal light/dark sensitivity. Finally, to investigate whether such findings could be related to post-surgery stress, melatonin analyses were performed in the subsequent 24 h and 7 days post-ophthalmectomy with cortisol levels assessed as an indicator of stress. Our results showed an inverse pattern of melatonin production in the eye cups of tilapia compared to blood circulating levels, suggesting different roles played by melatonin in these two tissues. Results then demonstrated that total or partial ophthalmectomy resulted in the suppression of night-time melatonin production. Furthermore, although pineals in culture were shown to be photosensitive, night-time melatonin levels were much lower than seen in other species. Finally, when performing sampling immediately or one week post-surgery, no difference in the melatonin profiles were observed. It is therefore unlikely that post-surgery stress would explain such suppression in melatonin production although all fish displayed high cortisol levels most probably due to social and handling stress. Taken together, these results provide further evidence of a new type of circadian organisation in a teleost species where the eyes are required to sustain night-time melatonin levels. [Copyright &y& Elsevier]

This study investigates the relative strengths of food and light zeitgebers in synchronization of circadian rhythms of Indian weaver birds and the role of the pineal gland in food-induced synchronization of the circadian activity rhythms. Two experiments were performed. In the first experiment, six birds were concurrently exposed for 10 days to PA 12/12 (12 h food present: 12 h food absent) and LD 12/12 (12 h light: 12 h dark). Then, the PA 12/12 cycle was reversed: food was present during the dark period of the LD 12/12 cycle. After 15 days, birds were released into constant dim light (LLdim). During exposure to overlapping light and food availability periods, birds were active only during the daytime. When light and food availability periods were presented in antiphase, two of six birds became night active. However, with the removal of the light zeitgeber (i.e., under LLdim), all birds were synchronized with reversed PA 12/12; hence, they were active during the subjective night (i.e., the period corresponding to darkness [ZT12-0] of the preceding LD 12/12). The second experiment examined whether the pineal contributed to the food-induced synchronization. After two weeks of concurrent PA 12/12 and LD 12/12 exposure, six birds were released into LLdim for 2.5 weeks. Under LLdim, five of six birds were synchronized to PA 12/12 with the circadian period (tau, τ) = 24 h. The LD 12/12 was restored, and after seven days, birds were pinealectomized (pinx). After 2.5 weeks, pinx birds were again released into LLdim for 2.5 weeks. Under LLdim, pinx birds did not become arrhythmic; instead, they appeared synchronized to PA 12/12 with τ = 24 h (n = 4) or ∼24 h (n = 2). We conclude that both food and light act as zeitgebers, although light appears to be the relatively stronger cue when the two are present together, as in the natural environment. We also found that the pineal is not necessary for food-induced synchronization. The findings suggest that food cycles could act as the synchronizer of circadian rhythmicity in biological functions in individuals held in an aperiodic environment. [ABSTRACT FROM AUTHOR]

Abstract: Avian circadian organization involves interactions between three neural pacemakers: the suprachiasmatic nuclei (SCN), pineal, and retina. Each of these structures is linked within a neuroendocrine loop to influence downstream processes and peripheral oscillations. However, the contribution of each structure to drive or synchronize peripheral oscillators or circadian outputs in avian species is largely unknown. To explore these interactions in the chick, we measured 2-deoxy[14C]-glucose (2DG) uptake and mRNA expression of the chick clock genes bmal1, cry1, and per3 in three brain areas and in two peripheral organs in chicks that underwent pinealectomy, enucleation, or sham surgery. We found that 2DG uptake rhythms damp under constant darkness in intact animals, while clock gene mRNA levels continue to cycle, demonstrating that metabolic rhythms are not directly driven by clock gene transcription. Moreover, 2DG rhythms are not phase-locked to rhythms of clock gene mRNA. However, pinealectomy and enucleation had similar disruptive effects on both metabolic and clock gene rhythms, suggesting that both of these oscillators act similarly to reinforce molecular and physiological rhythms in the chicken. Finally, we show that the relative phasing of at least one clock gene, cry1, varies between central and peripheral oscillators in a tissue specific manner. These data point to a complex, differential orchestration of central and peripheral oscillators in the chick, and, importantly, indicate a disconnect between canonical clock gene regulation and circadian control of metabolism. [Copyright &y& Elsevier]

Many animals exhibit pronounced changes in physiology and behavior on a seasonal basis, and these adaptations have evolved to promote survival and reproductive success. While the neuroendocrine pathways mediating seasonal reproduction are well-studied, far less is known about the mechanisms underlying seasonal changes in social behavior, particularly outside of the context of the breeding season. Our previous work suggests that seasonal changes in melatonin secretion are important in regulating aggression in Siberian hamsters (Phodopus sungorus); it is unclear, however, how melatonin acts via its receptors to modulate seasonal variation in social behavior. In this study, we infused a MT 1 melatonin receptor-expressing (MT 1) or control (CON) lentivirus into the adrenal glands of male Siberian hamsters. We then housed hamsters in long-day (LD) or short-day (SD) photoperiods, administered timed melatonin or control injections, and quantified aggressive and non-aggressive social behaviors (e.g., investigation, self-grooming) following 10 weeks of treatment. LD hamsters infused with the MT 1 lentivirus had significantly higher adrenal mt1 expression than LD CON hamsters, as determined via quantitative PCR. While melatonin administration was necessary to induce SD-like reductions in body and relative reproductive mass, only LD hamsters infused with the MT 1 lentivirus displayed SD-like changes in social behavior, including increased aggression and decreased investigation and grooming. In addition, SD CON and LD hamsters infused with the MT 1 lentivirus exhibited similar relationships between adrenal mt1 expression and aggressive behavior. Together, our findings suggest a role for adrenal MT 1 receptor signaling in regulating behavior, but not energetics or reproduction in seasonally breeding species. • Melatonin injections reduce body and reproductive tissue mass in long day (LD) males. • Adrenal MT 1 overexpression and short days (SDs) induce similar changes in social behavior. • LD and SD males show distinct relationships between adrenal mt1 expression and behavior. • MT 1 overexpression and SDs produce similar associations between adrenal mt1 expression and aggression. • Adrenal MT 1 receptors modulate seasonal changes in behavior, but not energetics or reproduction. [ABSTRACT FROM AUTHOR]

Abstract: Promoters with high levels of ubiquitous expression are of significant utility in the production of transgenic animals and cell lines. One such promoter is derived from the human cytomegalovirus immediate early (CMV-IE) gene. We sought to ascertain if the simian CMV-IE promoter (sCMV), used extensively in non-mammalian vertebrate research, also directs intense, widespread expression when stably introduced into zebrafish. Analysis of sCMV-driven expression revealed a temporal and spatial pattern not predicted by studies using the hCMV promoter in other transgenic animals or by observations of early F0 embryos expressing injected sCMV-reporter plasmids. Unexpectedly, in transgenic fish produced by both integration of linearized plasmid or Tol2-mediated transgenesis, sCMV promoter expression was generally observed in a small population of cells in telencephalon and spinal cord between days 2 and 7, and was thereafter confined to discrete regions of CNS that included the olfactory bulb, retina, cerebellum, spinal cord, and lateral line. In skeletal muscle, intense transgene expression was not observed until well into adulthood (>2–3 months post-fertilization). One final unexpected characteristic of the sCMV promoter in stable transgenic fish was tissue-specific responsiveness of the promoter to heat shock at both embryonic and adult stages. These data suggest that, in the context of stable transgenesis, the simian CMV-IE gene promoter responds differently to intracellular regulatory forces than other characterized CMV promoters. [Copyright &y& Elsevier]

Glutamate transporters are expressed throughout the CNS where their major role is to clear released glutamate from presynaptic terminals. Here, we report a novel function of the transporter in rat pinealocytes. This electrogenic transporter conducted inward current in response to L-glutamate and L- or D-aspartate and depolarized the membrane in patch-clamp experiments. Ca2+ imaging demonstrated that the transporter-mediated depolarization induced a significant Ca2+ influx through voltage-gated Ca2+ channels. The Ca2+ rise finally evoked glutamate exocytosis as detected by carbon-fiber amperometry and by HPLC. In pineal slices with densely packed pinealocytes, glutamate released from the cells effectively activated glutamate transporters in neighboring cells. The Ca2+ signal generated by KCl depolarization or acetylcholine propagated through several cell layers by virtue of the regenerative "glutamate-induced glutamate release." Therefore, we suggest that glutamate transporters mediate synchronized elevation of L-glutamate and thereby efficiently downregulate melatonin secretion via previously identified inhibitory metabotropic glutamate receptors in the pineal gland. [ABSTRACT FROM AUTHOR]

Abstract: Photoreceptor cells in the fish pineal gland transduce light–dark information differentially into a neuroendocrine melatonin message; distinguishing features are the presence or absence of endogenous oscillators that drive these rhythms. In the present study, we have analysed the presence and distribution of nitric oxide (NO) synthase in both pineal types by NADPH-diaphorase (NADPHd) histochemistry and determined the effects of NO donors on cGMP formation and melatonin production. NADPHd staining was confined to photoreceptor cells in clock-driven pineal organs of zebrafish and goldfish as evidenced by a codistribution with S-antigen-immunoreactivity (-ir) or cyclic GMP-ir and, in the pineal of the trout, to cells that are S-antigen negative. In the trout pineal, but not in the other species, NADPHd staining was clearly codistributed with growth associated protein-43 (GAP-43) immunoreactivity, an antibody that recognizes developing and regenerating neurons in the fish brain. The presence of a functional NO system in photosensory pineal organs is supported by the fact that NO donors like S-nitroso N-acetylpenicillamine (SNAP) elevate intracellular cGMP levels. However, despite the significant rise in cGMP levels nitric oxide donors did neither affect acute light-dependent melatonin formation in the trout pineal nor the rhythmic production of melatonin in the zebrafish pineal. [Copyright &y& Elsevier]

Abstract: Experiments were conducted to determine if diurnal variations occur in the cellular and humoral immune responses of sexually mature, male Japanese quail and if this diurnal variation is mediated by the daily rhythm of melatonin. In Experiment 1, quail were exposed to LD 12:12 light–dark cycles and immune responses were measured in response to a single antigenic challenge given to different groups every 4h over a 24h period. Diurnal changes occurred in both the cellular and humoral immune responses. The cellular response was higher during the light phase than during the dark phase whereas the opposite was true for the humoral immune response. Experiment 2 was designed to determine if melatonin mediated these diurnal immune responses. Quail were maintained in continuous light (LL) to suppress endogenous melatonin production and half of them were given melatonin in the drinking water for 12h each day for 2 weeks. Contrary to control quail, significant daily variations occurred in both the humoral and cellular immune responses of birds given melatonin. As in Experiment 1, the cellular and humoral immune responses were out of phase with one another, with the humoral response being maximal when melatonin was present. We may conclude that there exists a melatonin dependent diurnal variation in both cellular and humoral immune responses of quail. The responses were inverse to one another during the daily light–dark cycle with the cellular response being maximal during the daily light period and the humoral response being maximal during the daily dark period. [Copyright &y& Elsevier]

Arylalkylamine N-acetyltransferase (AA-NAT) is the rhythm-generating enzyme for the synthesis of pineal melatonin. Molecular investigations have revealed two biological models for the activation of AA-NAT. In rodent species, Aa-nat gene transcription is turned off during the daytime and markedly activated at night. In primates, sheep, and cows, the Aa-nat gene is constitutively transcripted with no visible daily variations. This inter-species difference in Aa-nat gene regulation leads to different daily profiles in melatonin synthesis and release. Thus, the nighttime onset of the rise in circulating melatonin is delayed and slow in rodents, whereas it is fast and sharp in sheep. In the camel (Camelus dromedarius), we have observed that circulating melatonin rises immediately after sunset, suggesting AA-NAT activity is regulated at the post-transcriptional level. In agreement with this hypothesis, we report herein the amount of Aa-nat mRNA in the camel pineal gland is high, during both the day and night with no daily variations, while melatonin concentration in the same pineal tissue is five times higher during the night than daytime. (Author correspondence: simonneaux@neurochem.u-strasbg.fr) [ABSTRACT FROM AUTHOR]

Abstract: Our laboratory has pioneered long-term microdialysis to monitor pineal melatonin secretion in living animals across multiple circadian cycles. There are numerous advantages of this approach for rhythm analysis: (1) we can precisely define melatonin onset and offset phases; (2) melatonin is a reliable and stable neuroendocrine output of the circadian clock (versus behavioral output which is sensitive to stress or other factors); (3) melatonin measurements can be performed extremely frequently, permitting high temporal resolution (10 min sampling intervals), which allows detection of slight changes in phase; (4) the measurements can be performed for more than four weeks, allowing perturbations of the circadian clock to be followed long-term in the same animals; (5) this is an automated process (microdialysis coupled with on-line HPLC analysis), which increases accuracy and bypasses the labor-intensive and error-prone manual handling of dialysis samples; and (6) our approach allows real-time investigation of circadian rhythm function and permits appropriate timely adjustments of experimental conditions. The longevity of microdialysis probes, the key to the success of this approach, depends at least in part on the methods of the construction and implantation of dialysis probes. In this article, we have detailed the procedures of construction and surgical implantation of microdialysis probes used currently in our laboratory, which are significantly improved from our previous methods. [Copyright &y& Elsevier]

Abstract: Elevated geomagnetic activity has been linked with human psychological, neurological and cardiovascular outcomes, and altered melatonin production has been implicated as an underlying mechanism to explain these effects. The relationship between geomagnetic activity and overnight excretion of the melatonin metabolite, 6-hydroxymelatonin sulfate (6-OHMS), was evaluated in a population of 153 male electric utility workers. The effect of geomagnetic activity combined with either 60Hz magnetic field or ambient light exposures was also evaluated. Elevated equivalent amplitudes (USGS, Boulder, CO) were associated with lower adjusted mean nocturnal 6-OHMS/cr concentrations and reduced total overnight 6-OHMS excretion, consistent with a previous study. Time intervals in which geomagnetic activity predicted the largest differences in mean 6-OHMS excretion generally occurred between 15- and 33-h prior to urine sample collection. These times coincide with key periods of melatonin regulation and production, respectively, suggesting that geomagnetic activity may play a role in the entrainment of human melatonin rhythms. [Copyright &y& Elsevier]

The duration of nocturnal pineal melatonin secretion transduces effects of day length (DL) on the neuroendocrine axis of photoperiodic rodents. Long DLs support reproduction, and short DLs induce testicular regression, followed several months later by spontaneous recrudescence; gonadal regrowth is thought to reflect development of tissue refractoriness to melatonin. In most photoperiodic species, pinealectomy does not diminish reproductive competence in long DLs. Turkish hamsters (Mesocricetus brandti) deviate from this norm: elimination of melatonin secretion in long-day males by pinealectomy or constant light treatment induces testicular regression and subsequently recrudescence; the time course of these gonadal transitions is similar to that observed in males transferred from long to short DLs. In the present study, long-day Turkish hamsters that underwent testicular regression and recrudescence in constant light subsequently were completely unresponsive to the antigonadal effects of short DLs. Other hamsters that manifested testicular regression and recrudescence in short DLs were unresponsive to the antigonadal effects of pinealectomy or constant light. Long-term suppression of melatonin secretion induces a physiological state in Turkish hamsters similar or identical to the neuroendocrine refractoriness produced by short-day melatonin signals (i.e., neural refractoriness to melatonin develops in the absence of circulating melatonin secretion). A melatonin-independent interval timer, which would remain operative in the absence of melatonin during hibernation, may determine the onset of testicular recrudescence in the spring. In this respect, Turkish hamsters differ from most other photoperiodic rodents. [ABSTRACT FROM AUTHOR]

Abstract: Hyperglycemia is a well-known factor in reducing nocturnal pineal melatonin production. However, the mechanism underlying diabetes-induced insufficiency of pineal melatonin has remained uncertain. This study was undertaken to examine the structure, innervation and functional activity of the pineal gland in streptozotocin (STZ)-induced diabetes in rats by immunohistochemistry, Western blotting and image analysis. The number of the pinealocytes and the volume of pineal were also estimated using stereologic quantification including the optical fractionator and Cavalieri''s method. It has also shown a progressive reduction of the total area of the pineal gland and the nuclear size of pinealocytes beginning at 4 weeks of induced diabetes. Surprisingly, the immunoreactive intensities and protein amounts of serotonin (5-HT) and protein gene product (PGP) 9.5 in the pineal gland were progressively increased from 4 weeks of diabetes. Meanwhile, nerve fibers immunoreactive for PGP 9.5 had disappeared. Diabetes-induced neuropathy was observed in nerve fibers containing tyrosine hydroxylase (TH). The affected nerve fibers appeared swollen and smooth in outline but they showed a distribution pattern, packing density and protein levels comparable to those of the age-matched control animals. Ultrastructural observations have revealed diabetes-induced deformity of Schwann cells and basal lamina, accumulation of synaptic vesicles and deprivation of the dense-core vesicles in the axon terminals and varicosities. The increase in immunoreactivities in 5-HT and PGP 9.5 and shrinkage of pineal gland in the diabetic rats suggest an inefficient enzyme activity of the pinealocytes. This coupled with the occurrence of anomalous TH nerve fibers, may lead to an ineffective sympathetic innervation of the pinealocytes resulting in reduced melatonin production in STZ-induced diabetes. [Copyright &y& Elsevier]

The purpose of this work was to investigate the circadian melatonin system in two tropical teleost species characterized by different behavioral habits, Nile tilapia (diurnal) and African catfish (nocturnal). To do so, fish were subjected to either a control photoperiod (12L:12D), continuous light (LL) or darkness (DD), or a 6L:6D photoperiod. Under 12L:12D, plasma melatonin levels were typically low during the photophase and high during the scotophase in both species. Interestingly, in both species, melatonin levels significantly decreased prior to the onset of light, which in catfish reached similar basal levels to those during the day, demonstrating that melatonin production can anticipate photic changes probably through circadian clocks. Further evidence for the existence of such pacemaker activity was obtained when fish were exposed to DD, as a strong circadian melatonin rhythm was maintained. Such an endogenous rhythm was sustained for at least 18 days in Nile tilapia. A similar rhythm was shown in catfish, although DD was only tested for four days. Under LL, the results confirmed the inhibitory effect of light on melatonin synthesis already reported in other species. Finally, when acclimatized to a short photo-cycle (6L:6D), no endogenous melatonin rhythm was observed in tilapia under DD, with melatonin levels remaining high. This could suggest that the circadian clocks cannot entrain to such a short photocycle. Additional research is clearly needed to further characterize the circadian axis in teleost species, identify and localize the circadian clocks, and better understand the environmental entrainment of fish physiology. [ABSTRACT FROM AUTHOR]

Abstract: The mammalian pineal gland is an important component of the circadian system. In the present study, we examined the expression of roughly 8000 genes in the rat pineal gland as a function of time of day under light–dark (LD) cycles and in constant dark (DD) using oligo DNA microarray technique. We identified 47 and 13 genes that showed higher levels at night and day, respectively, under LD. The same patterns of expression were also observed in DD. About half of the genes that peaked at night have a known biological function, i.e., transcription factors and proteins that are involved in signaling cascades, whereas 14 are expressed sequence tags and 8 have an unknown biological function. Twelve of the genes that were up-regulated at night were also up-regulated after 1h NE stimulation, thus suggesting that the expression of these genes is controlled by adrenergic mechanisms. Of the 13 genes that were up-regulated in the daytime, 6 coded for proteins that are involved in intracellular signaling pathways. The results obtained with microarray analysis were well correlated with data obtained using real time quantitative RT-PCR. The present results provide new materials to dissect and understand the pineal physiology. [Copyright &y& Elsevier]

Avian behavior and physiology are temporally regulated by a complex circadian clock on both a daily and an annual basis. The circadian secretion of the hormone melatonin is a critical component of the regulation of circadian/daily processes in passerine birds, but there is little evidence that the gland regulates annual changes in primary reproductive function. Here it is shown that locomotor rhythms of house sparrows, Passer domesticus, which are made arrhythmic by either pinealectomy or maintenance in constant light, can be synchronized by daily administration of melatonin of different durations to simulate the melatonin profiles indicative of long and short photoperiods. Pinealectomized male sparrows maintained in constant darkness were entrained by both melatonin regimens. In both cases, testes were regressed and the song control nuclei were small. Intact male house sparrows maintained in constant light were also entrained to both melatonin regimens. However, sparrows that received a long duration melatonin cycle exhibited small song control nuclei, while sparrows that received short duration melatonin or no melatonin at all exhibited large song control nuclei. The data indicate that seasonal changes in melatonin duration contribute to the regulation of song control nuclei. [ABSTRACT FROM AUTHOR]

Summary: Organic cation transporter 3/4 (OCT3/4) is a transcription factor of embryonic stem cells; c-kit (CD117) is a tyrosine kinase receptor implicated in seminoma carcinogenesis. Their reactivity is well characterized in testicular, but not extragonadal and metastatic, germ cell tumors. A total of 93 germ cell tumors (41 seminoma, 22 embryonal carcinoma, 18 teratoma, and 12 yolk sac tumor) were obtained from the central nervous system (30), mediastinum (23), retroperitoneum/abdomen (31), and other locations (9). Immunohistochemical staining for c-kit, placental-like alkaline phosphatase (PLAP), OCT3/4, and new markers D2-40 and AP-2γ was performed on seminomas; CD30 and epithelial membrane antigen were added for nonseminomas. In embryonal carcinoma, c-kit reacted in 17 of 22 cases, OCT3/4 in 18 of 22, and PLAP in 13 of 22. OCT3/4 was superior to PLAP in intensity and percent cells staining. In seminoma, OCT3/4 and D2-40 were superior to PLAP in intensity and percent cells; c-kit and AP-2γ were superior in percent cells. D2-40 stained 23 of 24 seminomas strongly but had only weak focal reactivity in 6 of 17 embryonal carcinomas. Sensitivity and specificity were high for OCT3/4 discriminating seminoma and embryonal carcinoma, and c-kit discriminating seminoma, from other germ cell tumors. For embryonal carcinoma, OCT3/4 had higher specificity (0.94) than CD30 (0.786) owing to CD30 reactivity in 3 of 10 teratomas. Epithelial membrane antigen discriminated teratoma from other nonseminomas with a sensitivity of 1 but reacted occasionally in embryonal carcinoma (3/15) and yolk sac tumor (2/7). In conclusion, for extragonadal seminoma, OCT3/4, AP-2γ, D2-40, and c-kit were equivalently superior to PLAP. For embryonal carcinoma, OCT3/4 was superior to PLAP and more specific than CD30. D2-40 is recommended to discriminate between seminoma and embryonal carcinoma. [Copyright &y& Elsevier]

Egr-1 is a plasticity-related transcription factor that has been implicated in circadian regulation of the pineal gland. In the present study we have investigated the cellular expression pattern of Egr-1 in the adult rat pineal. Egr-1 protein is restricted to the nucleus of a sub-population of cells. These cells were characterised using a new transgenic rat model (egr-1-d2EGFP) in which green fluorescent protein is driven by the egr-1 promoter. Cellular filling by GFP revealed that Egr-1-positive cells exhibited processes, indicating a glial cell-type morphology. This was confirmed by co-localizing the GFP-filled processes with vimentin and S-100β. However, GFP/Egr-1 is expressed in only a tiny minority of the previously identified Id-1/vimentin-positive glial cells and therefore represents a novel sub-set of this (GFAP-negative) glial population. We have also demonstrated for the first time an extensive network of nestin-positive cells throughout the adult pineal gland, however these cells do not co-express Egr-1. Our studies have therefore broadened our understanding of the cell populations that constitute the adult pineal. Cellular localization of Egr-1 has revealed that this factor does not appear to be directly involved in pinealocyte production of melatonin but is required in a sub-set of pineal glia. [ABSTRACT FROM AUTHOR]

Circadian physiology in the vertebrate retina is regulated by several neurotransmitters. In the lateral eyes of the green iguana the circadian rhythm of melatonin content peaks during the night while the rhythm of dopamine peaks during the day. In the present work, the authors explore the interaction of these 2 neurotransmitters during the circadian cycle. They depleted retinal dopamine with intravitreal injections of 6-hydroxydopamine (6-OHDA) and measured ocular melatonin content in vivo throughout 1 circadian cycle. The circadian rhythm of ocular melatonin not only persisted but increased 10-fold in amplitude. This increase was substantially reduced by the intraocular administration of dopamine. 6-OHDA-treated retinas, unlike those from untreated animals, did not express a circadian rhythm of melatonin synthesis in vitro. To deplete retinal melatonin, the authors pinealectomized iguanas and blocked retinal melatonin synthesis by depleting serotonin with intraocular injections of 5,6-dihydroxytryptamine. In animals so treated, they found that the circadian rhythm of retinal dopamine content was abolished, the levels of dopamine were lowered, and the levels of dopamine metabolites were greatly increased. The data suggest that in iguanas, the amplitude of the circadian rhythm of melatonin synthesis in the eye is suppressed by dopamine while the rhythm of dopamine depends, at least in part, on the presence of melatonin. [ABSTRACT FROM AUTHOR]

Ultrastructural localization of neuronal nitric oxide synthase (nNOS) in olfactory receptor neurons (ORNs) and immunohistochemical detection of the enzyme in forebrain, pituitary, and pineal were undertaken in the teleost Oreochromis mossambicus. Application of post-embedding immunoelectron microscopy revealed nNOS-labeled gold particles on the cilia, microvilli, mitochondria, and Golgi complex of the ORNs. Gold particles were also seen adhered to microtubules in the axons that extend to the olfactory nerve layer in the olfactory bulb. With light microscopy, nNOS-immunoreactive neurons were seen in preoptic area, nucleus entopeduncularis, and parvocellular, and magnocellular subdivisions of nucleus preopticus (NPO). Numerous cerebrospinal fluid-contacting cells lining the wall of the third ventricle at the level of the NPO showed intense immunoreactivity. Intense to moderate immunoreactivity was observed in the neurons of suprachiasmatic nucleus, nucleus lateralis tuberis pars lateralis, and nucleus recessus lateralis. While several immunoreactive fibers were detected in medial olfactory tract, suprachiasmatic area, and hypothalamo-hypophyseal tract, a few were seen throughout the telencephalon, in the optic chiasma, tuberal area, and inferior lobes. In the pituitary, nNOS-containing fibers were seen in the neurohypophysis, rostral pars distalis, proximal pars distalis, and pars intermedia. While intense immunoreactivity was noticed in some cells in the pineal, immunoreactive fibers were detected in the pineal stalk as well as parenchyma. We suggest that nitric oxide may play a role in processing olfactory and photic information, circadian rhythms, and neuroendocrine regulation in tilapia. [ABSTRACT FROM AUTHOR]

Daily torpor in the Djungarian hamster ( Phodopus sungorus) is a precisely timed event gated by the circadian clock situated in the suprachiasmatic nuclei (SCN) of the hypothalamus. Timing-controlled hypothermia during which body temperature ( Tb) decreases to ∼15 °C implies temperature compensation of the circadian system. Nevertheless, it remains controversial how the molecular clockwork functions at those low Tb values and whether the torpor bout affects the circadian system. In this study, we investigated rhythmic clock and clock-related gene as well as protein expression in the SCN and pineal gland of torpid and normothermic Djungarian hamsters over a 48 h cycle. We clearly demonstrate rhythmic gene expression of Per1, Bmal1 and Avp in the SCN as well as Aa-nat in the pineal gland on a day of torpor. Alterations in the phase and amplitude of these rhythms, however, may be due to decreased protein synthesis during hypothermia. This decreased protein feedback resulting from the hypothermia might also be responsible for changes in gene expression observed 1 day after a torpor bout. We conclude that temperature has at least a modulatory effect on the circadian system. [ABSTRACT FROM AUTHOR]

The rhythm of plasma melatonin concentration is currently the most accurate marker of the endogenous human circadian pacemaker. A number of methods exist to estimate circadian phase and amplitude from the observed melatonin rhythm. However, almost all these methods are limited because they depend on the shape and amplitude of the melatonin pulse, which vary among individuals and can be affected by environmental influences, especially light. Furthermore, these methods are not based on the underlying known physiology of melatonin secretion and clearance, and therefore cannot accurately quantify changes in secretion and clearance observed under different experimental conditions. A published physiologically-based mathematical model of plasma melatonin can estimate synthesis onset and offset of melatonin under dim light conditions. We amended this model to include the known effect of melatonin suppression by ocular light exposure and to include a new compartment to model salivary melatonin concentration, which is widely used in clinical settings to determine circadian phase. This updated model has been incorporated into an existing mathematical model of the human circadian pacemaker and can be used to simulate experimental protocols under a number of conditions. [ABSTRACT FROM AUTHOR]

Melatonin exerts oncostatic effects on different kinds of neoplasias, especially on oestrogen-dependent tumours. Recently, it has been described that melatonin, on the basis of its antioxidant properties, inhibits the growth of glioma cells. Glioma cells express oestrogen receptors and have the ability to synthesise oestrogens from androgens. In the present study, we demonstrate that pharmacological concentrations of melatonin decreases the growth of C6 glioma cells and reduces the local biosynthesis of oestrogens, through the inhibition of aromatase, the enzyme that catalyses the conversion of androgens into oestrogens. These results are supported by three types of evidence. Firstly, melatonin counteracts the growth stimulatory effects of testosterone on glioma cells, which is dependent on the local synthesis of oestrogens from testosterone. Secondly, we found that melatonin reduces the aromatase activity of C6 cells, measured by the tritiated water release assay. Finally, by (RT)–PCR, we found that melatonin downregulates aromatase mRNA steady-state levels in these glioma cells. We conclude that melatonin inhibits the local production of oestrogens decreasing aromatase activity and expression. By analogy to the implications of aromatase in other forms of oestrogen-sensitive tumours, it is conceivable that the modulation of the aromatase by pharmacological melatonin may play a role in the growth of glioblastomas.British Journal of Cancer (2007) 97, 755–760. doi:10.1038/sj.bjc.6603935 www.bjcancer.com Published online 14 August 2007 [ABSTRACT FROM AUTHOR]

We recently reported a diurnal and norepinephrine (NE) -induced expression of mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) in the rat pineal gland and postulated that this MKP-1 expression might impact adrenergic-regulated arylalkylamine- N-acetyltransferase (AA-NAT) activity via modulation of MAPKs. In this study, we investigated the effect of depletion of MKP-1 expression by using doxorubicin, a topoisomerase inhibitor that suppresses the expression of MKP-1 in other cell types and small interfering RNA targeted against Mkp1 in NE-stimulated pinealocytes. We found that both treatments were effective in inhibiting NE induction of MKP-1 expression. Moreover, both treatments also resulted in a prolonged activation of p42/44MAPK and an increase in AA-NAT induction by NE. In contrast, treatment of pinealocytes with PD98059, an inhibitor of MAPK kinase, reduced NE-stimulated AA-NAT activity. Interestingly, suppressing MKP-1 expression had no effect on the time profile of NE-stimulated p38MAPK activation. These results indicate that MKP-1 modulates the profile of AA-NAT activity by selectively shaping the activation profile of p42/44MAPK but not that of p38MAPK. [ABSTRACT FROM AUTHOR]

Melatonin production is not restricted to the pineal gland. Several extrapineal sources of this indole such as retina, Harderian gland, and immune system are well documented. Melatonin of pineal origin is not present in the rat at early stages of development. To assess the potential capacity of local melatonin synthesis by the immature brain and to gain insight into the relationship between melatonin production by the brain (without the pineal gland) and pineal gland during rat development, the melatonin content as well as the expression and activity of the melatonin-synthesizing enzymes, N-acetyltransferase (NAT) and hydroxyindole- O-methyltransferase (HIOMT), were studied at fetal and postnatal stages. Moreover, melatonin-membrane receptor (MT1) expression was also analyzed. Both, the expression and activity of NAT and HIOMT were found in the brain with significant day/night differences in enzymes activities. Additionally, melatonin content was detected in all stages showing day/night differences depending on the stage of development. The brain nocturnal melatonin content was higher than diurnal content on postnatal day 16 and in adult rats which is in accordance with the pineal melatonin synthesis. To investigate the origin of this brain melatonin, pinealectomized rats were used and we found that the developing brain produced its own melatonin. Also, MT1 expression was detected in brain during development. These results demonstrate that, when the pineal is not yet producing melatonin, there is melatonin synthesis by the brain that could be used as protection from free radical damage and/or could exert some actions through MT1 receptors. [ABSTRACT FROM AUTHOR]

Abstract: Mammalian Nr2e1 (Tailless, Mtll or Tlx) and Nr2e3 (photoreceptor-specific nuclear receptor, Pnr) are highly related orphan nuclear receptors, that are expressed in eye and forebrain-derived structures. In this study, we analyzed the developmental expression patterns of zebrafish nr2e1 and nr2e3. RT-PCR analysis showed that nr2e1 and nr2e3 are both expressed during embryonic and post-embryonic development. To examine the spatial distribution of nr2e1 and nr2e3 during development whole-mount in situ hybridization was performed. At tailbud stage, initial nr2e1 expression was localized to the rostral brain rudiment anterior to pax2.1 and eng2 expression at the prospective midbrain–hindbrain boundary. During subsequent stages, nr2e1 became widely expressed in fore- and midbrain primordia, eye and olfactory placodes. At 24hpf, strong nr2e1 expression was detected in telencephalon, hypothalamus, dorsal thalamus, pretectum, midbrain tectum, and retina. At 2dpf, the initially widespread nr2e1 expression became more restricted to distinct regions within the fore- and midbrain and to the retinal ciliary margin, the germinal zone which gives rise to retina and presumptive iris. Expression of nr2e3 was exclusively found in the developing retina and epiphysis. In both structures, nr2e3 expression was found in photoreceptor cells. The developmental expression profile of zebrafish nr2e1 and nr2e3 is consistent with evolutionary conserved functions in eye and rostral brain structures. [Copyright &y& Elsevier]

The aim of the current investigation was to study the effect of lithium on circadian rhythms of pineal – testicular hormones by quantitations of pineal and serum serotonin, N-acetylserotonin and melatonin, and serum testosterone at four time points (06.00, 12.00, 18.00 and 24.00) of a 24-hr period under normal photoperiod (L:D), reversed photoperiod (D:L), constant light (L:L) and constant dark phase (D:D) in rats. Circadian rhythms were observed in pineal hormones in all the combinations of photoperiodic regimens, except in constant light, and in testosterone levels in all the photoperiodic combinations. Pineal and serum N-acetylserotonin and melatonin levels were higher than serotonin at night (24.00 hr), in natural L:D cycle, in reversed L:D cycle or similar to normal L:D cycle in constant dark phase, without any change in constant light. In contrast, testosterone level was higher in light phase (12.00 hr through 18.00 hr) than in the dark phase (24.00 hr through 06.00 hr) in normal L:D cycle, in reversed L:D cycle, similar to normal L:D cycle in constant dark (D:D), and reversed to that of the normal L:D cycle in constant light (L:L). Lithium treatment (2 mEq/kg body weight daily for 15 days) suppressed the magnitude of circadian rhythms of pineal and serum serotonin, N-acetylserotonin and melatonin, and testosterone levels by decreasing their levels at four time points of a 24-hr period in natural L:D or reversed D:L cycle and in constant dark (D:D). Pineal indoleamine levels were reduced after lithium treatment even in constant light (L:L). Moreover, lithium abolished the melatonin rhythms in rats exposed to normal (L:D) and reversed L:D (D:L) cycles, and sustained the rhythms in constant dark. But testosterone rhythm was abolished after lithium treatment in normal (L:D)/reversed L:D (D:L) cycle or even in constant light/dark. The findings indicate that the circadian rhythm exists in pineal hormones in alternate light – dark cycle (L:D/D:L) and in constant dark (D:D), but was absent in constant light phase (L:L) in rats. Lithium not only suppresses the circadian rhythms of pineal hormones, but abolishes the pineal melatonin rhythm only in alternate light – dark cycles, but sustains it in constant dark. The testosterone rhythm is abolished after lithium treatment in alternate light – dark cycle and constant light/dark. It is suggested that (a) normal circadian rhythms of pineal hormones are regulated by pulse dark phase in normal rats, (b) lithium abolishes pineal hormonal rhythm only in pulse light but sustains it in constant dark phase, and (c) circadian testosterone rhythm occurs in both pulse light or pulse dark phase in normal rats, and lithium abolishes the rhythm in all the combinations of the photoperiod. The differential responses of circadian rhythms of pineal and testicular hormones to pulse light or pulse dark in normal and lithium recipients are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The pineal gland of the zebrafish (Danio rerio) is a clock-containing photoreceptive organ. Superfused pineal glands kept in darkness display rhythmic melatonin production that lasts for days, with high melatonin levels during the night and low levels during the day. Nocturnal light, however, evokes an acute suppression of melatonin synthesis in the photoreceptor cells. Towards characterizing zebrafish pineal photopigment that is involved in the acute melatonin suppression we have measured the spectral sensitivity of melatonin-suppression response in superfused pineal glands. The effect of 2h light exposure of seven wavelengths (λ avg 408, 460, 512, 560, 608, 660 and 697±10–15nm) at multiple irradiances (107–1014 photons/cm2/s) was determined, and an action spectrum was plotted. The resultant action spectrum provides evidence for the involvement of multiple photopigments in melatonin suppression. The most efficient melatonin-suppression response was achieved by exposure to light of around 512nm; however, another peak of lower irradiance sensitivity was observed in the middle to long wavelengths. Opsins-specific RT-PCR analysis confirmed the expression of exo-rhodopsin and visual red-sensitive opsin in the pineal gland, while other zebrafish visual opsins as well as VA and VAL opsins were not detected. Dartnall monograms for exo-rhodopsin and visual red-sensitive opsin account for most but not all of the spectral sensitivity features. Therefore, additional pineal photopigments may contribute to the melatonin-suppression response in the pineal gland. [Copyright &y& Elsevier]

In the ewe, seasonal anestrus results from an increased responsiveness of the hypothalamus to the negative feedback of estradiol (E2) on the gonadotropic axis under long-day conditions. However, this seasonal effect could also depend upon variable uptake of steroids by the brain. The aim of the present experiment was to compare the concentration of E2 in the blood plasma and in the cerebrospinal fluid (CSF) from the third ventricle in groups of ovariectomized, estradiol treated ewes maintained under short day (SD) or long day (LD) conditions and to study the involvement of the pineal gland in this photoperiodic regulation. Pinealectomized and sham-operated ewes were equipped with an intracerebral cannula to sample the CSF. The plasma E2 concentrations showed no difference between LD and SD in sham-operated and pinealectomized animals. In contrast, in the CSF, E2 concentration was higher in the LD than the SD group, and pinealectomy suppressed this effect of photoperiod. Concomitantly, the stimulatory effect of SD on luteinizing hormone levels observed in sham-operated ewes was abolished by pinealectomy. The results demonstrate that LD increases the E2 concentration in the CSF by a mechanism involving the pineal gland. [ABSTRACT FROM AUTHOR]

Abstract: Dysfunction of circadian melatonin production by the pineal gland in aged humans and rats is thought to reflect the functional loss of its sympathetic innervation. Our ultrastructural neuropathologic studies of the sympathetic innervation of the pineal gland of aged (24 months old) Fischer-344 and Sprague–Dawley rats showed loss of nerve terminals as well as the development of neuroaxonal dystrophy (NAD), an ultrastructurally distinctive distal axonopathy, far in excess of that in young control rats. Immunolocalization of tyrosine hydroxylase confirmed the age-related loss of normal noradrenergic innervation and development of NAD. NAD was more frequent in aged female rats compared to males and was particularly severe in aged female Sprague–Dawley rats compared to Fischer-344 rats. Pineal NGF content was significantly increased or unchanged in female and male aged Fischer-344 rats, respectively, compared to young controls. The rat pineal is a sensitive experimental model for the quantitative ultrastructural examination of age-related neuropathological changes in nerve terminals of postganglionic noradrenergic sympathetic axons, changes which may reflect similar changes in the diffusely distributed sympathetic innervation of other targeted endorgans. [Copyright &y& Elsevier]

Studies in rodents with retinal degeneration indicated that neither the rod nor the cone photoreceptors obligatorily participate in circadian responses to light, including melatonin suppression and photoperiodic response. Yet there is a residual phase-shifting response in melanopsin knockout mice, which suggests an alternate or redundant means for light input to the SCN of the hypothalamus. The findings of Aggelopoulos and Meissl suggest a complex, dynamic interrelationship between the classic visual photoreceptors and SCN cell sensitivity to light stimuli, relative to various adaptive lighting conditions. These studies raised the possibility that the phototransductive physiology of the retinohypothalamic tract in humans might be modulated by the visual rod and cone photoreceptors. The aim of the following two-part study was to test the hypothesis that dim light adaptation will dampen the subsequent suppression of melatonin by monochromatic light in healthy human subjects. Each experiment included 5 female and 3 male human subjects between the ages of 18 and 30 years, with normal color vision. Dim white light and darkness adaptation exposures occurred between midnight and 0200 h, and a full-field 460-nm light exposure subsequently occurred between 0200 and 0330-h for each adaptation condition, at 2 different intensities. Plasma samples were drawn following the 2-h adaptation, as well as after the 460-nm monochromatic light exposure, and melatonin was measured by radioimmunoassay. Comparison of melatonin suppression responses to monochromatic light in both studies revealed a loss of significant suppression after dim white light adaptation compared with dark adaptation (p < 0.04 and p < 0.01). These findings indicate that the activity of the novel circadian photoreceptive system in humans is subject to subthreshold modulation of its sensitivity to subsequent monochromatic light exposure, varying with the conditions of light adaptation prior to exposure. [ABSTRACT FROM AUTHOR]

Purpose: Exposure to residential magnetic fields may disrupt the normal nocturnal rise in melatonin levels, resulting in increased risk for breast cancer, possibly through increased levels of reproductive hormones. We investigated whether exposure to a 60-Hz magnetic field under controlled conditions is associated with a decrease in urinary nocturnal 6-sulfatoxymelatonin level and increase in luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estrogen levels in healthy premenopausal women. Methods: Using a crossover design, half the participants were assigned to magnetic field exposure of 5 to 10 mG greater than ambient levels for 5 consecutive nights during the early to midluteal phase of the menstrual cycle. On the last night of exposure, a nocturnal urine sample was collected. The next month, participants were sham exposed. The other half of participants were assigned the reverse order of exposure. Results: Magnetic field exposure was associated with decreased 6-sulfatoxymelatonin levels, but no changes in reproductive hormone levels were observed. Participants using prescription medications and anovulatory participants had more pronounced decreases in 6-sulfatoxymelatonin levels with magnetic field exposure. Conclusion: This study provides further evidence that exposure to magnetic fields is associated with decreased nocturnal melatonin levels, but does not support the hypothesis that such exposure results in increased urinary levels of estrogens, LH, or FSH. [Copyright &y& Elsevier]

This study determined whether a blood plasma melatonin rhythm persists in constant photothermal environments in the sleepy lizard, Tiliqua rugosa. It builds upon an earlier investigation which provided equivocal results as to whether an in vivo melatonin rhythm persists in constant dark (DD) and light (LL) and temperature in this species. Using more frequent sampling points and new assay techniques, the present study showed that the melatonin rhythm persisted for at least 6 days at temperatures of 25 and 33°C in constant dark (DD). The melatonin rhythm, however, was largely eliminated in constant light (LL) at 33°C, thereby contradicting some previous findings in other species of reptiles where melatonin levels were apparently insensitive to an unexpected pulse of light at night. These results demonstrate that the sleepy lizard has a persistent, possibly circadian rhythm of melatonin in DD and constant temperature, and that the rhythm is inhibited by LL and constant temperature. Therefore, the sleepy lizard pineal gland may be an independent oscillator capable of driving the melatonin rhythm and be a transducer of the seasonally changing external photothermal environment. [ABSTRACT FROM AUTHOR]

Luteinizing hormone (LH) influences the secretion of melatonin ( N-acetyl-5-methoxytryptamine) from the pineal gland. The present study examined the possible presence of LH/chorionic gonadotropin (CG) receptor in the pineal gland of adult female rats. Reverse transcriptase-polymerase chain reaction analyses demonstrated that LH/CG receptor mRNA is expressed in the pineal gland. Western blotting showed that the pineal gland, like the ovary, contains an 80 kDa receptor protein. Immunohistochemistry revealed that LH/CG receptor, arylalkylamine N-acetyltransferase (a regulatory enzyme in melatonin biosynthesis) and serotonin (a melatonin precursor) are localized primarily to the same cells of the pineal gland. We further found that the levels of pineal LH/CG receptor protein in normal cycling female rats change significantly during the estrous cycle, being lowest at early metestrus. These results demonstrate that LH/CG receptor is expressed in the pineal gland, primarily in melatonin-synthesizing cells, namely pinealocytes. Furthermore, it is suggested that LH influences pineal melatonin secretion through binding to this receptor. In addition, LH/CG receptor levels in the pineal gland are regulated during the estrous cycle under normal physiological conditions. [ABSTRACT FROM AUTHOR]

Abstract: The gene encoding the last enzyme of the melatonin-synthesis pathway, hydroxyindole-O-methyltransferase (HIOMT), is selectively expressed in retinal photoreceptors and pineal cells. Here, we analysed the promoter of the chicken HIOMT gene and we found that a homeodomain-binding element located in the proximal region of this promoter was essential for its activation in primary cultures of embryonic chicken retinal cells. This homeodomain-regulatory element interacted with a protein expressed in the chicken retina and pineal gland, which was recognized by an anti-Otx2 antiserum. Recombinant Otx2 expressed in vitro was able to bind this DNA element and to directly transactivate the chicken HIOMT promoter. This promoter was also transactivated by another member of the Otx family, Otx5, but the amplitude of stimulation was lower than with Otx2. The spatio-temporal pattern of Otx2 expression was compatible with a possible role of this transcription factor in HIOMT gene activation. In adult chicken, Otx2 mRNA was found to be present in those two tissues that express HIOMT: the retina and the pineal gland. During development, a burst of Otx2 mRNA closely matched the timing of HIOMT gene activation in these two tissues. In the pineal, Otx2 immunolabelling was specifically localized in the nuclei of photoreceptor cells. In the neural retina, Otx2 immunoreactivity brightly decorated the photoreceptor nuclei and extended more faintly to the outer half of the inner nuclear layer. Together, the data support a role of Otx2 in the onset of HIOMT expression in developing chicken photoreceptors. [Copyright &y& Elsevier]

Abstract: The amount of 6-sulphatoxymelatonin, the chief metabolite of melatonin, in the urine was measured in nine patients, who were subjected to bilateral sympathectomy at the second thoracic ganglionic level for treatment of hyperhidrosis of the palms. All patients showed before surgery a normal 6-sulphatoxymelatonin excretion with a peak in the excretion during the night time. After the sympathectomy, the high night time excretion was clearly abolished in five patients but remained high in four patients. This indicates that the segmental locations of the preganglionic sympathetic perikarya in the spinal cord, stimulating the melatonin secretion in the pineal gland in humans, vary between individuals. An increase in daytime melatonin excretion was observed in the patients responding to the sympathectomy with an abolished 6-sulphatoxymelatonin rhythm. This increase could indicate that the final sympathetic neurons innervating the pineal gland might have a both stimulatory and inhibitory function. [Copyright &y& Elsevier]

Abstract: Activation of members of the mitogen-activated protein kinase (MAPK) family of signaling cascades is a tightly controlled event in rat pinealocytes. Cell culture studies indicate that whereas the NE→cGMP activation of p42/44MAPK is rapid and transient, the NE→cAMP activation of p38MAPK is slower and more sustained. The decline in the p42/44MAPK response is in part due to the induction of MAPK phosphatase-1 by NE. In comparison, p38MAPK activation is tightly coupled to the synthesis and degradation of an upstream element in its activation cascade. Whole animal studies confirm activation of p42/44MAPK occurring during the early part of night and precedes p38MAPK activation. Studies with selective MAPK inhibitors reveal a modulating effect of MAPKs on arylalkylamine-N-acetyltransferse (AA-NAT) activity, with involvement of p42/44MAPK in the induction of AA-NAT and p38MAPK participating in the amplitude and duration of the AA-NAT response. These effects of p42/44MAPK and p38MAPK on AA-NAT activity match their timing of activation. Taken together, our studies on the timing of MAPK activation and regulation of AA-NAT by MAPKs add to the importance of MAPKs in regulating the circadian biology of the pineal gland. [Copyright &y& Elsevier]

Abstract: Photoreceptor cells of the pineal gland express distinct sets of proteins dedicated to photoreception, phototransduction and to rhythmic melatonin production. This review discusses the function of key regulatory sequences and nuclear factors that determine tissue-restricted expression of photoreceptor genes, specifically, the photoreceptor conserved element (PCE) and the E-box and their cognate binding proteins. Recent research in zebrafish revealed that PCE and E-box mediate the action of OTX5 and BMAL/CLOCK, respectively. These transcription factors drive enhanced expression of serotonin-N-acetyltransferase-2 (aanat2) in the pineal gland by synergistic interaction. Extensive research of other photoreceptor-specific genes suggested that the presence of several PCEs along with additional sequence elements is required to drive enhanced tissue-specific expression of these genes. Therefore, the mechanism identified for zebrafish aanat2, or at least part of it, may apply to other photoreceptor-specific genes in zebrafish and other species. [Copyright &y& Elsevier]

Objectives.—To describe the clinical characteristics and laboratory findings of cluster headache patients whose headaches responded to testosterone replacement therapy. Background.—Current evidence points to hypothalamic dysfunction, with increased metabolic hyperactivity in the region of the suprachiasmatic nucleus, as being important in the genesis of cluster headaches. This is clinically borne out in the circadian and diurnal behavior of these headaches. For years it has been recognized that male cluster headache patients appear overmasculinized. Recent neuroendocrine and sleep studies now point to an association between gonadotropin and corticotropin levels and hypothalamically entrained pineal secretion of melatonin. Results.—Seven male and 2 female patients, seen between July 2004 and February 2005, and between the ages of 32 and 56, are reported with histories of treatment resistant cluster headaches accompanied by borderline low or low serum testosterone levels. The patients failed to respond to individually tailored medical regimens, including melatonin doses of 12 mg a day or higher, high flow oxygen, maximally tolerated verapamil, antiepileptic agents, and parenteral serotonin agonists. Seven of the 9 patients met 2004 International Classification for the Diagnosis of Headache criteria for chronic cluster headaches; the other 2 patients had episodic cluster headaches of several months duration. After neurological and physical examination all patients had laboratory investigations including fasting lipid panel, PSA (where indicated), LH, FSH, and testosterone levels (both free and total). All 9 patients demonstrated either abnormally low or low, normal testosterone levels. After supplementation with either pure testosterone in 5 of 7 male patients or combination testosterone/estrogen therapy in both female patients, the patients achieved cluster headache freedom for the first 24 hours. Four male chronic cluster patients, all with abnormally low testosterone levels, achieved remission. Conclusions.—Abnormal testosterone levels in patients with episodic or chronic cluster headaches refractory to maximal medical management may predict a therapeutic response to testosterone replacement therapy. In the described cases, diurnal variation of attacks, a seasonal cluster pattern, and previous, transient responsiveness to melatonin therapy pointed to the hypothalamus as the site of neurological dysfunction. Prospective studies pairing hormone levels and polysomnographic data are needed. [ABSTRACT FROM AUTHOR]

Abstract: The SIOP PNET 3 study was designed to determine whether 10 weeks of moderately intensive chemotherapy given after surgery and before radiotherapy (RT) would improve the outcome for patients with primitive neuroectodermal tumours (PNETs) compared with RT alone. Patients with a histological diagnosis of supratentorial PNET (StPNET) and no radiological evidence of metastatic disease were initially eligible for randomisation to either chemotherapy followed by craniospinal RT 35Gy in 21 fractions with a boost of 20Gy in 12 fractions to the primary site, or RT alone. In respect of the increasing recognition that StPNET were high-risk tumours, randomisation for this group closed in November 1999. This analysis includes both randomised and non-randomised patients with StPNET entered into the study database. Sixty-eight patients aged 2.9–16.6 years (median 6.5 years) were included in the analysis (chemotherapy+RT: 44, RT alone: 24). Fifty-four patients (79%) had a non-pineal and 14 (21%) a pineal site. At a median follow-up of 7.4 years, for all patients overall survival (OS) at 3 and 5 years was 54.4% and 48.3%, respectively. Event-free survival (EFS) at 3 and 5 years was 50.0% and 47.0%, respectively. There was no statistically significant difference in OS or EFS according to treatment received. OS (P =0.05) and EFS (P =0.03) were significantly better for patients with pineal primary sites. EFS for pineal tumours were 92.9% at 3 years and 71.4% at 5 years and for non-pineal primaries 40.7% at 3 years and 40.7% at 5 years. This study confirmed the relatively good survival for non-metastatic pineal PNETs but poor survival of non-pineal StPNETs. There was no evidence that pre-radiation chemotherapy improved outlook. Future treatment programs should be directed at the particular natural history of these tumours, to further define prognostic factors and to explore further biological characteristics. [Copyright &y& Elsevier]