bluuebunny/crossref_metadata_2025 huggingface dataset:
The presence of nerve fibers immunoreactive for vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), and preproVIP(111–122) in the mouse pineal gland
Authors: Mikkelsen Jens D. , Møiler Morten , Larsen Philip J. , Fahrenkrug Jan
Published: February 2007

Mikkelsen JD, Møller M, Larsen PJ, Fahrenkrug J. The presence of nerve fibers immunoreactive for vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), and preproVIP(111‐l22) in the mouse pineal gland. J. Pineal Res. 1994: 16: 50–56.

A low to moderate number of vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI)‐immunoreactive nerve fibers with prominent boutons‐en‐passage were demonstrated in the pineal gland of the mouse. The two peptides, which are parts of the same precursor molecule, were distributed identically in the gland. Positive fibers were present in the connective tissue septae in the gland, in the pineal capsule, and in the pineal parenchyma. No VIP‐PHI‐immunoreactive elements were found in the deep pineal gland, in the pineal stalk, or in habenular and posterior commissures. This morphological distribution of immunoreactive nerve fibers, which is similar to the distribution in other mammals, indicates that the VIP/PHI fibers of the mouse pineal gland originate exclusively from perikarya in a peripheral ganglion, presumably one of the cholinergic ganglia of the head. No evidence for a VIPergic central innervation was found. VIP and PHI are connected via a bridging peptide equivalent to amino acids 111‐122 of the precursor (preproVIP(111‐122)). In order to demonstrate the possible existence of this peptide in intra‐pineal nerve fibers, antisera directed against a synthetic sequence identical to pre‐proVIP(111–122) and immunohistochemistry were applied.

PreproVIP(111‐122)‐immunoreactive nerve fibers were observed in the mouse pineal gland, with the same distribution pattern and morphology as those immunoreactive for VIP and PHI. To quantify the peptide‐immunoreactivities, 50 mice pineals were pooled, extracted, and the concentrations were measured radioimmunologically. The concentrations of the VIP and preproVIP(111–122) immunoreactivities were 1.7 and 2.0 pmol/g, respectively, whereas the concentration of PHI was 0.9 pmol/g. This indicates that not only VIP and PHI, but also other fragments of preproVIP are present in the mammalian pineal gland. Whereas the stimulatory role of VIP is well documented, the effect of other fragments processed from preproVIP on pinealocytes remains to be established.
The role of serotonin and melatonin in gastrointestinal physiology: Ontogeny, regulation of food intake, and mutual serotonin‐melatonin feedback
Authors: Bubenik G. A. , Pang S. F.
Published: February 2007

Bubenik GA, Pang SF. The role of serotonin and megaton in gastrointestinal physiology: Ontogeny, regulation of food intake, and mutual serotonin‐melatonin feedback. J. Pineal Res. 1994: 16: 91–99.

Average levels of melatonin in the brain and the gastrointestinal (GIT) tissues of newborn mice declined dramatically during the first week postnatally. Food consumption increased considerably in mice bearing subcutaneous serotonin (5‐HT) implants (2 mg). Melatonin implants (2 mg) also increased overall consumption but to a lesser degree. Both 5‐HT and melatonin implants (2 mg) increased water content of mice fecal pellets, albeit the melatonin effect was less pronounced. Serotonin implants (2,4,6 mg/mouse) increased melatonin levels in brain, jejunum, ileum, and colon, but the effect was not dose‐dependent. Intraperitoneally administered melatonin (5, 20 and 200 ug/mouse) elevated melatonin levels in brain and GIT tissues more than 100 times that of the controls, but the effect was not dose‐dependent. In contrast, intraperitoneal administration of melatonin (5, 50, and 200 ug) in mice bearing a 5‐HT implant (2 mg) resulted in only 3‐7 times higher melatonin levels in the GIT as compared to controls, and the brain levels of melatonin were actually lower. A feedback system between 5–HT and melatonin is proposed that regulates appetite and digestive processes by endocrine as well as paracrine effects in both the brain and the GIT.
Hydroxyindole‐O‐methyltransferase activity in the pineal gland of the muskox (Ovibos moschatus)
Authors: Tedesco Susan C. , Morton Oougal J. , Reiter Russel J.
Published: February 2007

Tedesco SC, Morton DJ, Reiter RJ. Hydroxyindole‐O‐methyltransferase activity in the pineal gland of the muskox (Ovibos moschatus). J. Pineal Res. 1994: 16: 121–126.

Characteristics of hydroxyindole‐O‐methyltransferase (HIOMT) activity were examined in pineal gland tissue from 10 muskoxen shot by native hunters in November, 1990. The enzyme preferentially methylated N‐acetylserotonin, with other hydroxyindole compounds showing relatively low affinities; activity peaked sharply at pH 8. 2. HIOMT was noncompetitively inhibited by its substrate, N‐acetylserotonin, and competitively inhibited by its product S‐adenosylhomocysteine. The catalytic mechanism appeared to be ordered as described in previous studies: S‐adenosylmethionine was the obligatory first substrate, followed by N‐acetylserotonin; methyl transfer then occurred and the products, melatonin and S‐adenosylhomocysteine, were released sequentially. Interestingly, the inhibition constant (K) for N‐acetylserotonin was relatively close to the Michaelis‐Menten constant (Km), which might allow physiological concentrations of N‐acetylserotonin to inhibit HIOMT activity in vivo. This effect could be relevant to the ecology of free‐living muskoxen during the dramatic seasonal fluctuations in dietary protein and daily photoperiod associated with their arctic habitat.
Interaction between melatonin and estradiol on morphological and morphometric features of MCF‐7 human breast cancer cells
Authors: Crespo O. , Fernandez‐Viadero C. , Verduga R. , Ovejero V. , Cos S.
Published: February 2007

Crespo D, Fernández‐Viadero R, Verduga R, Ovejero V, Cos S. Interaction'between melatonin and estradiol on morphological and morphometric features of MCF‐7 human breast cancer cells. J. Pineal Res. 1994:16:215–222.

Melatonin has been shown to have a direct inhibitory effect on the proliferation of estrogen‐responsive MCF‐7 human breast cancer cells, involving an interaction with estradiol. The anti‐proliferative effect of melatonin is reversed by the addition of estradiol to the culture. In the present study, we examined whether inhibition by megaton and subsequent estrogen rescue of MCF‐7 cells are correlated with morphological and morph metric changes in these cells. After 4 days of exposure to melatonin, MCF‐7 cells showed significantly smaller cell and nuclear sizes than other groups. These morphometric results were closely related to the ultra structural features observed in these cells. While control and estradiol‐treated cells showed increased tumor characteristics, melatonin‐treated cells presented greater differentiation, in keeping with their epithelial origin (presence of cytokeratin filament bundles, conspicuous rough endoplasmic reticulum, and Golgi cisternae together with the presence of prominent nucleoli at the nuclear level). Additionally, some melatonin‐treated cells displayed degenerative features (mitochondrial swelling with disruption of cristae, cytoplasmic vacuolation, nuclear chromatin disgregation and cell lysis). The addition of estradiol to cells previously incubated with melatonin reversed the changes induced by the latter and these cells showed the same ultrastructural features as the control cells. Our results support the notion that melatonin exerts its antitumor effect through a cell‐cycle‐specific mechanism by delaying the entry of MCF‐7 cells into mitosis. This allows the tumor cells to achieve greater differentiation. The fact that the morph metric and morphological effects induced by megaton are counteracted by estrogens suggests a cell‐cycle acceleration induced by estradiol.
Immunohistochemical studies on the coexistence of catecholamine‐synthesizing enzymes and neuropeptide Y in nerve fibers of the porcine pineal gland
Authors: Kaleczyc Jerzy , Przybylska Barbara , Majewski Mariusz , Lewczuk Bogdan
Published: February 2007

Kaleczyc J, Przybylska B, Majewski M, Lewczuk B. Immunohistochemical studies on the coexistence of catecholamine‐synthesizing enzymes and neuropeptide Y in nerve fibers of the porcine pineal gland. J. Pineal Res. 1994: 17: 20–24.

The distribution of nerve fibers immunoreactive (IR) to catecholamine‐synthesizing enzymes, tyrosine hydroxylase (TH), dopamine‐β‐hydroxylase (DβH), and phenylefhanolamine‐N‐methyltransferase (PNMT) as well as neuropeptide Y (NPY), in the pineal gland of adult sows was investigated by the use of double‐labeling immunohistochemistry. The porcine pineal gland was found to be supplied by TH‐IR nerve fibers, the vast majority of which were also DBH‐positive. TH‐ and TH/DβH‐IR nerves were located mostly in the capsula and connective septa of the pineal gland, and their fine varicose branches terminated in the adherent parenchyma. NPY‐IR fibers formed a loose network overlapping that was observed in the case of TH‐and DβH‐IR fibers. Most of NPY‐IR fibers were also positive for TH. The density of the fiber networks depended on the region of the gland. No PNMT‐IR structures were observed.
Inhibitory effect of melatonin on cataract formation in newborn rats: Evidence for an antioxidative role for melatonin
Authors: Abe Mitsushi , Reiter Russel J. , Orhii Paul B. , Hara Masayuki , Poeggeler Burkhard
Published: February 2007

Abe M, Reiter RJ, Orhii PB, Hara M, Poeggeler B. Inhibitory effect of melatonin on cataract formation in newborn rats: Evidence for an antioxidative role for melatonin. J. Pineal Res. 1994; 17: 94–100. ©Munksgaard 1994

We evaluated the inhibitory effect of melatonin, a recently discovered scavenger of free radicals, on cataract formation in the newborn rat. The glutathione synthesis inhibitor, buthionine sulfoximine (BSO) (3 mmol/kg), was intraperitoneally injected into newborn rats for 3 consecutive days starting on day 2 after birth. These glutathione depleted rats develop cataracts. Melatonin (4 mg/kg) was injected intraperitoneally into half of the rats once a day beginning at day 2 after birth; the other half of the animals received solvent daily. The incidence of cataract was observed on day 16, after the eyes of the newborn animals had opened. Both reduced glutathione (GSH) and oxidized glutathione (GSSG) levels were measured. Cataracts were observed in all animals (18/18) treated with BSO plus solvent. The incidence of the cataract in the animals cotreated with melatonin was only 6. 2% (1/15). Total lenticular glutathione (GSH + GSSG) levels in BSO only treated rats were reduced by 97%. The total glutathione in the lens of the BSO plus melatonin group was significantly higher (by 3%) than that of the BSO only group. The percentage of the total glutathione as GSSG for the BSO plus solvent group was higher than the control value. Cotreatment of BSO injected rats with melatonin (4 mg/kg/day) clearly reduced cataract formation proving that it is directly or indirectly protective against oxidative stress which accompanies glutathione deficiency. The inhibitory effects of melatonin on cataract formation in this study could be due to melatonin's free radical scavenging activity or due to its stimulatory effect on glutathione production.
Inhibitory effect of melatonin on production of IFNγ or TNFα in peripheral blood mononuclear cells of some blood donors
Authors: Di Stefano Anna , Paulesu Luana
Published: February 2007

Di Stefano A, Paulesu L. Inhibitory effect of melatonin on production of IFNγ or TNFα in peripheral blood mononuclear cells of some blood donors. J. Pineal Res. 1994;17:164–169.

Melatonin, the main pineal hormone, has been shown to influence many biological functions, including the immune response and cancer growth. The purpose of this study was to examine the effect of melatonin on the production of interferon gamma (IFNγ) and tumor necrosis factor alpha (TNFα) by peripheral blood mononuclear cells (PBMC) in culture. Melatonin at physiological concentrations fails to induce production of IFN or TNF by PBMC in culture but causes a dose‐related inhibition of production of both cytokines if the PBMC are stimulated with phytohaemagglutinin. This inhibitory effect occurs in only 22% of cases (melatonin‐sensitive) but disappears when the cells are stored at 4°C for 4 days. The effect of melatonin appears not to be mediated by opiates nor to be correlated with the age, sex, or blood group of donors, but seems to be influenced by the seasonal time of blood collection. These results provide further evidence for an interaction between melatonin and the immune system and suggest that the effect of melatonin on production of IFN and TNF may be mediated by various factors not yet fully understood.
Response of collared lemmings to melatonin: II. Infusions and photoperiod
Authors: Gower Barbara A. , Hadjipanayis Constantinos , Nagy Tim R. , Stetson Milton H.
Published: February 2007

Gower BA, Hadjipanayis C, Nagy TR, Stetson MH. Response of collared lemmings to melatonin: II. Infusions and photoperiod. J. Pineal Res. 1994:17:185–194.

Collared lemmings (Dicrostonyx groenlandicus) show much phenotypic plasticity when exposed to photoperiods of varying length. In addition to “long day” and “short day” morphologies, apparent when animals are exposed to 22L:2D and 8L:16D, respectively, animals with intermediate features appear when collared lemmings are placed on day lengths ranging from 18L:6D to 14L:10D. Body mass, body composition, pelage color and length, the presence and size of a bifid claw, and reproductive condition are all influenced by ambient day length. We tested the hypothesis that variations in the melatonin signal mediate the physiological and morphological responses observed in collared lemmings housed in various photoperiods. One group of collared lemmings was fitted with a subcutaneous cannula at weaning and infused for 8 weeks with 2, 6, or 14 hr melatonin or 14 hr vehicle daily while housed in constant light (LL). Additional groups were transferred to LL, 20L:4D, 16L:8D, or 8L:16D (all uninfused). The response of the animals to both melatonin infusion and photoperiod was graded; the degree to which the “winter” morphology developed was proportional to the length of both the melatonin infusion and the scotophase. Both the 14 hr infusion and the 8L:16D photoperiod promoted development of the characteristic “winter” traits: large body size, white pelage, bifid claw, small uterus, and low serum prolactin (PRL). Conversely, treatment with the 2 hr infusion or exposure to the long photoperiods (LL, 20L:4D) resulted in a “summer‐like” morphology. Infusion of 6 hr melatonin per day or exposure to 16L:8D produced animals with an intermediate physiology. Overall, the results support the hypothesis that variations of the endogenous melatonin rhythm mediate the effect of photoperiod length on seasonal physiological and morphological changes in collared lemmings.
Circadian and ultradian variations of pituitary and pineal hormones in normal men: Evidence for a link between melatonin, gonadotropin, and prolactin secretion
Authors: Lerchl Alexander , Partsch Carl‐Joachim , Nieschlag Eberhard
Published: February 2007

Abstract: The study was performed to investigate the physiological relationship between the pineal hormone melatonin and pituitary functions in normal men. Se‐ries of blood samples were obtained at 10‐min intervals for 24‐hr periods from 10 male volunteers (age 19–25 years). Samplings were repeated after 2 weeks and 3 months. Serum levels of melatonin, follicle‐stimulating hormone (FSH), luteiniz‐ing hormone (LH), prolactin (PRL), and testosterone (T) were estimated by immu‐noassay methods (LH, PRL, every sample; melatonin, every 30 min; T, every 4 hrs; FSH once for each session). Diurnal characteristics of PRL and melatonin profiles were estimated by complex cosinor analysis, while short‐term pulsatility of LH and PRL secretion was analyzed by the PULSAR algorithm. Data were cor‐related by linear regression analysis. The combined information of all three sam‐pling sessions revealed significant negative correlations between the following parameters (N = 10): Amplitude (Ampl) melatonin and Ampl PRL: r = ‐0.727, P < 0.02; Ampl melatonin and maximal (Max) PRL values: r = ‐0.73, P < 0.02; Max melatonin and Max PRL: r = ‐0.725, P < 0.02; area under the curve (AUC) melatonin and Ampl PRL: r = ‐0.637, P < 0.05; AUC melatonin and Max PRL: r = ‐0.640; P < 0.05; duration (Dur) of melatonin synthesis and Ampl PRL: r = ‐0.685, P < 0.03; Dur melatonin and Max PRL: r = ‐0.676, P < 0.04; Dur mela‐tonin and FSH levels: r = ‐0.663, P < 0. 04; AUC melatonin and LH mean con‐centration: r = ‐0.732, P < 0. 02; Max melatonin and LH mean concentration: r = ‐0.657, P < 0.04. These correlations varied considerably between the three ses‐sions, mainly due to intra‐individual variabilities of secretory patterns of PRL and LH, while the melatonin profiles were comparably stable. The results indicate that melatonin production and pituitary functions may be related in normal men. Be‐cause of the substantial intra‐ and inter‐individual variations in hormone secretory patterns, large numbers of volunteers and/or repeated measurements are essential for studies addressing the pineal‐pituitary connection in normal humans.
Melatonin modulation of estrogen‐regulated proteins, growth factors, and proto‐oncogenes in human breast cancer
Authors: Molis Tina M. , Spriggs Louaine L. , Jupiter Yolanda , Hill Steven M.
Published: February 2007

Abstract: The growth‐inhibitory actions of the pineal hormone, melatonin, on hu‐man breast tumor cells and the possible association between this inhibition and melatonin's down‐regulation of the estrogen receptor (ER) expression were exam‐ined in the ER‐positive, estrogen‐responsive MCF‐7 human breast tumor cell line. As previously reported, melatonin dramatically inhibits the growth of these breast tumor cells and down‐regulates ER levels in these cells, suggesting that the modu‐lation of ER may be an important mechanism by which melatonin inhibits breast cancer cell growth. In the present studies, Northern blot analysis was used to ex‐amine the expression of estrogen‐regulated transcripts known to be involved in es‐trogen's mitogenic actions. Melatonin, at a physiologic concentration (10−9 M), rapidly, significantly, and, in some cases, transiently elevated the steady‐state mRNA levels of growth stimulatory products such as TGFα, c‐myc, and pS2, which are normally up‐regulated in response to estrogen. Conversely, melatonin decreased the expression of other factors normally up‐regulated by estrogen, such as progesterone receptor and c‐fos. Significant stimulation of the expression of the growth‐inhibitory factor TGFβ was seen with melatonin treatment, potentially sup‐porting the concept that melatonin's growth‐inhibitory activity is mediated through the breast tumor cells’estrogen‐response pathway. The early regulation of many of these products by melatonin suggests that mechanisms more rapid than the down‐regulation of ER are important in melatonin's modulation of their ex‐pression. However, the long‐term modulation of these transcripts (12–48 hr) may be heavily influenced by melatonin's down‐regulation of ER expression. These re‐sults clearly define the need for additional in depth studies to dissect the cellular events leading to melatonin‐induced growth inhibition in breast tumor cells.
The orphan receptor family RZR/ROR, melatonin and 5‐lipoxygenase: An unexpected relationship
Authors: Carlberg Carsten , Wiesenberg Irmgard
Published: February 2007

Abstract: The orphan receptors RZRoα, RZRβ, RORod, RZRα2, RORα3, and RORγform a subfamily within the superfamily of nuclear hormone receptors. Recently, experimental evidence that the pineal gland hormone melatonin is the natural ligand for these nuclear receptors has come to light. This discovery is rather surprising, given that most people in the field believed melatonin acts exclusively through membrane receptors. However, these new findings establish a nuclear signalling pathway for melatonin, i.e., direct ligand‐induced control of target gene transcription, which most probably mediates part of the physiological functions of the hormone. Interestingly, the very recently identified first RZR/melatonin responding gene, 5‐Iipoxygenase, is not expressed in the brain and is not involved in circadian rhythmicity, but rather acts in the periphery, mainly in myeloid cells, as one of the key enzymes of allergic and inflammatory reactions. Thus, nuclear melatonin signalling opens up a new perspective in understanding the actions of the pineal gland hormone.
Melatonin protects neurons from singlet oxygen‐induced apoptosis
Authors: Cagnoli Cinzia M. , Atabay Cagla , Kharlamova Elena , Manev Hari
Published: February 2007

Abstract: Singlet oxygen (O2[1Δg]) is a very reactive molecule that can be produced by living cells and may contribute to cytotoxicity. The pineal hormone melatonin has been reported to possess potent antioxidant activity, and to be capable of scavenging O2(1Δg). We investigated whether melatonin might reduce the neurotoxic action of O2(lΔg). The cytotoxic effect of singlet oxygen was studied in primary cultures of cerebellar granule neurons pretreated with a photosensitive dye, rose bengal, and exposed to light—a procedure that generates O2(1Δg). We found that this procedure triggers neuronal death, which is preceded by mitochondrial impairment (assayed by the rate of the reduction of MTT, 3‐[4,5‐di‐methylthiazol‐2‐yl]‐2,5‐diphenyl tetrazolium bromide, into formazan), and by DNA fragmentation—a marker of apoptosis. DNA fragmentation was determined in situ by terminal deoxynucleotidyl transferase assay; cell death was assayed with 0.4% trypan blue solution—viable cells with an intact membrane are not permeable to trypan blue; dead cells are, and thus, they are stained blue. Neuroprotection was obtained with the pineal hormone melatonin. In a cell‐free system, melatonin also protected the enzyme creatine kinase (EC 2.7.3.2) from the rose bengal‐induced injury. The results suggest that melatonin might counteract the cytotoxic action of singlet oxygen. Further studies are needed to clarify the exact role singlet oxygen and melatonin might play in neurodegenerative diseases.
Adenosine A2 receptor‐mediated stimulation of cyclic AMP in cultured chicken pineal cells
Authors: Falcón Jack , Van Camp Gilles , Collin Jean Pierre
Published: February 2007

Abstract: The pineal gland of vertebrates produces the time‐keeping hormone melatonin in a rhythmic manner. Regulation of melatonin production is a multifactorial process. In the chicken, light, perceived through the skull, and norepinephrine, acting through α2‐adrenergic receptors, synergistically inhibit day time melatonin production. In addition, adenosine exerts autocrine/paracrine modulatory effects on melatonin secretion. In an attempt to elucidate how these effects of adenosine are mediated, chicken pineal cells were cultured, in the dark during day time, in the presence of different analogs of adenosine. When the adenosine transmembranous carrier was inhibited, chloroadenosine stimulated cyclic AMP (cAMP) accumulation in a time‐ and dose‐dependent manner. The effects were antagonized by 8‐phenyltheophylline, an antagonist at the A1/A2 adenosine receptors. A dose‐dependent stimulation of cAMP accumulation was also obtained with other adenosine agonists, with the following order of potency: N‐ethylcarboxamidoadenosine > cyclopentyladenosine > R‐phenyl‐isopropylade‐nosine. The stimulatory effect of the latter compound was still observed when basal cAMP levels were increased in the presence of forskolin. Under our experimental conditions no inhibition of cAMP content was observed. Our results are consistent with the idea that stimulation of melatonin secretion by adenosine analogs is mediated through A2 receptors.
Melatonin stimulates the activity of the detoxifying enzyme glutathione peroxidase in several tissues of chicks
Authors: Pablos Marta I. , Agapito Maria T. , Gutierrez Regina , Recio Jose M. , Reiter Russel J. , Barlow‐Walden Lornell , Acuña‐Castroviejo Dario , Menendez‐Pelaez Armando
Published: February 2007

Abstract: The pineal hormone melatonin has been shown to directly scavenge free radicals and to stimulate, in the mammalian brain, at least one enzyme, glutathione peroxidase, which reduces free radical generation. In the present studies, we examined the effect of melatonin on glutathione peroxidase activity in several tissues of an avian species. Melatonin (500 μg/kg), when injected into chicks, increased glutathione peroxidase activity within 90 min in every tissue examined. Tissue melatonin levels, measured by radioimmunoassay, also increased following its peripheral administration. Depending on the tissue, the measured increases in melatonin varied from 75% to 1,300% over the control values. The melatonin‐induced increases in glutathione peroxidase activity varied with the tissue and were between 22% and 134%. These percentage increases in glutathione peroxidase activity were directly correlated with tissue melatonin content. These results suggest that melatonin induces the activity of the detoxifying enzyme, glutathione peroxidase, in several tissues in the chick. The findings also suggest that melatonin would reduce the generation of highly toxic hydroxyl radicals by metabolizing its precursor, hydrogen peroxide. Because of this ability to stimulate glutathione peroxidase activity, melatonin should be considered as a component of the antioxidative defense system in this avian species.
Minireview The influence of season, photoperiod, and pineal melatonin on immune function
Authors: Nelson Randy J. , Demas Gregory E. , Klein Sabra L. , Kriegsfeld Lance J.
Published: February 2007

Abstract: In addition to the well‐documented seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among many animal populations. Challenging winter conditions (i.e., low ambient temperature and decreased food availability) can directly induce death via hypothermia, starvation, or shock. Coping with these challenges can also indirectly increase morbidity and mortality by increasing glucocorticoid secretion, which can compromise immune function. Many environmental challenges are recurrent and thus predictable; animals could enhance survival, and presumably increase fitness, if they could anticipate immunologically challenging conditions in order to cope with these seasonal threats to health. The annual cycle of changing photoperiod provides an accurate indicator of time of year and thus allows immunological adjustments prior to the deterioration of conditions. Pineal melatonin codes day length information. Short day lengths enhance several aspects of immune function in laboratory studies, and melatonin appears to mediate many of the enhanced immunological effects of photoperiod. Generally, field studies report compromised immune function during the short days of autumn and winter. The conflict between laboratory and field data is addressed with a multifactor approach. The evidence for seasonal fluctuations in lymphatic tissue size and structure, as well as immune function and disease processes, is reviewed. The role of pineal melatonin and the hormones regulated by melatonin is discussed from an evolutionary and adaptive functional perspective. Finally, the clinical significance of seasonal fluctuations in immune function is presented. Taken together, it appears that seasonal fluctuations in immune parameters, mediated by melatonin, could have profound effects on the etiology and progression of diseases in humans and nonhuman animals. An adaptive functional perspective is critical to gain insights into the interaction among melatonin, immune function, and disease processes.
Effects of melatonin implants on winter fur growth and testicular recrudescence in adult male raccoon dogs (Nyctereutes procyonoides)
Authors: Xiao Yongjun , Forsberg Mats , Laitinen Jarmo T. , Valtonen Maija
Published: February 2007

Abstract: The effects of melatonin implants were investigated on winter fur growth, monitored by counting growing and mature hairs per bundle and testicular recrudescence, judged by testis width, score count of spermatogenesis, and serum testosterone in the adult male raccoon dogs. Melatonin administration in July highly elevated melatonin concentrations in serum and urine and induced an earlier decrease in prolactin secretion (August in the treated group vs September in the control group), winter fur growth (July‐beginning of November in the treated group vs. August‐end of November in the control group) and testicular recrudescence (October in the treated group vs. November in the control group). In the control animals, urinary excretion of melatonin between 1500–0900 hr increased during autumn followed by a rapid fall in winter. The increase from July (1.8 ± 0.4 ng) to August (3.9 ± 0.5 ng) and the subsequent unchanged levels until October coincided with the period of winter fur growth. The further increase in November (6.5 ± 1.2 ng) coincided with the significant elevation in both testis width and score count of spermatogenesis. These results suggest a role of the increase in endogenous melatonin secretion during autumn in the growth of winter fur and testicular recrudescence in this species under natural conditions. Relatively high serum concentrations of prolactin were shown in two animals, one in the control group and another in the treated group. However, the parameters for testis and winter fur growth in the two cases were similar to those in the remainder of the animals. Thereby, the role of prolactin in the winter fur growth and the initiation of testicular recrudescence, if it is truly involved, is manifested through its decreasing secretion rather than the actual blood concentrations.
Characterization of the antioxidant effects of melatonin and related indoleamines in vitro
Authors: Chan Tak‐Yuen , Tang Pak‐Lai
Published: February 2007

Abstract: The antioxidant and possible pro‐oxidant effects of melatonin and related indoleamines (tryptophan, serotonin, N‐acetylserotonin, and 5‐methoxytryptamine) were studied in vitro. In two model membrane systems, i.e., phospholipid liposomes and rat erythrocytes, lipid peroxidation induced by Fe2+ and H2O2, respectively, were reduced by the tested indoleamines except for tryptophan. The 5‐hydroxy‐indoleamines, serotonin, and N‐acetylserotonin exhibited pro‐oxidant actions in the bleomycin assay by reducing Fe3+ to Fe2+, which leads to DNA damage. The 5‐methoxy‐indoleamines, melatonin and 5‐methoxytryptamine, were devoid of any pro‐oxidant actions in this assay. Serotonin, but not N‐acetylserotonin, scavenged the superoxide anion. None of the indoleamines tested had any reactivity towards H2O2. All the indoleamines, including tryptophan, were, however, shown to react with hypochlorous acid. These findings support an antiperoxidative and antioxidant action of melatonin which is devoid of pro‐oxidant effect on non‐lipid substrates.
Release of vasopressin in response to altered plasma volume and sodium concentrations following pinealectomy in the rat
Authors: Forsling Mary L. , Stoughton R. , Kelestimur H. , Kostoglou‐Athanassiou I. , Demaine C.
Published: February 2007

Abstract: Pinealectomy has been shown to alter daily rhythms of neurohypophysial hormone release, with plasma hormone concentrations being elevated in the morning, as compared to intact rats. To determine whether pineal removal also altered the response to known stimuli of hormone release, vasopressin concentrations were measured in control, sham‐operated, and pinealectomized animals during extracellular fluid hypertonicity produced by an intraperitoneal (i.p.) injection of hypertonic saline or hypovolaemia produced by an i.p. injections of polyethylene glycol. In the combined sham‐operated and unoperated groups, injection of hypertonic saline produced a marked increase in plasma vasopressin concentrations from 2.18 ± 0.28 to 7.2 ± 1.24 pmol/liter, but the response was attenuated in pinealectomized animals, concentrations increasing to only 3.4 ± 1.2 pmol/liter. Similarly, following infusion of hypertonic saline, the increase in plasma vasopressin per unit increase in plasma sodium was lower in pinealectomized animals than the pineal intact controls. The response to hypovolaemia was also attenuated, plasma hormone concentrations following reduction in blood volume of approximately 10% increasing to only 3.6 ± 0.6 pmol/liter as compared to 7.3 ± 2.2 pmol/liter in the control groups. There were no significant differences in pituitary vasopressin content in any of the groups studied. Thus, the pineal may influence the vasopressin response to physiological stimuli.
Diurnal changes in the content of indoleamines, catecholamines, and methoxyindoles in the pineal gland of the Djungarian hamster (Phodopus sungorus): Effect of photoperiod
Authors: Míguez Jesús M. , Recio Joaquín , Vivien‐Roels Berthe , Pévet Paul
Published: February 2007

Abstract: Previous studies in Syrian hamster have shown that the correlations between the daily fluctuations in the contents of pineal indoleamines and methoxyindoles are influenced by the photoperiod, and that dopamine may play a role in the regulation of pineal function. The present study investigated the 24 hour changes in the content of 5‐hydroxytryptophan (5‐HTP), serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐HIAA), N‐acetylserotonin (NAS), melatonin, 5‐methoxytryptophol (5‐MT), noradrenaline (NA), dopamine (DA), and 3,4‐dihydroxyphenylacetic acid (DOPAC) in the pineal gland of female Djungarian hamsters exposed to long (LP; LD 16: 8) or short (SP; LD 10: 14) photoperiods for 10 weeks. Pronounced nocturnal increases of N‐acetylserotonin and melatonin content were observed irrespective of the photoperiod regime. The content of 5‐HT was markedly decreased during the first hour of the night in LP, which contrasted with the lack of changes in NAS and melatonin content at this time. In SP, an increased 5‐HTP content and a less obvious decrease in 5‐HT content was observed during the night, although melatonin and NAS content were even higher than in LP. Similar daily patterns as for 5‐HT were observed in the 5‐HT oxidative metabolites (5‐HIAA and 5‐MT). When considering values throughout the day, a poor correlation for 5‐HT vs. NAS and melatonin content was observed, which was particularly evident during the nighttime. These data indicate that the daily variation of pineal indoles may not only be dependent on changes in the N‐acetyltransferase activity but also in other mechanisms regulating pinealocyte 5‐HT availability. As previously reported in other species of hamster, pineal NA content did not show daily variations in LP conditions, although a nocturnal increase was detected in SP. In contrast, pronounced nocturnal increases were observed in the content of DA and its acid metabolite, DOPAC, irrespective of the photoperiod. These data indicate the existence of an increased dopaminergic turnover during the night and further support a role for DA in the regulation of melatonin synthesis and in the synchronization of the pineal functions.
Rat and gerbil pinealocytes contain the synaptosomal‐associated protein 25 (SNAP‐25)
Authors: Redecker P , Weyer C. , Grube D.
Published: February 2007

Abstract: It has recently been established that the neuroendocrine pinealocytes of mammals contain several synaptic membrane proteins that are involved in the regulation of vesicle trafficking in the nerve terminal. In the present study, we have conducted immunoblot and immunocytochemical analyses to demonstrate that another key component of the presynaptic plasmalemma, i.e., protein SNAP‐25 (synaptosomal‐associated protein 25 kDa), can be detected in pinealocytes. Immunostaining of serial semi‐thin sections of plastic‐embedded rat and gerbil pineals with monoclonal SNAP‐25 antibodies showed that SNAP‐25 was present in pinealocytes of both species. We proved its coexpression with other synaptic membrane proteins (synaptophysin, synaptotagmin I, synaptobrevin II, and syntaxin I) at the single cell level. Thus, pinealocytes obviously are endowed with the major proteins that are thought to regulate the targeting and exocytosis of secretory vesicles, in particular of synaptic ‐like microvesicles.
A role for bursa fabricii and bursin in the ontogeny of the pineal biosynthetic activity in the chicken
Authors: Youbicier‐Simo B.J. , Boudard F. , Mékaouche M. , Baylé J.D. , Bastide M.
Published: February 2007

Abstract: The tripeptide bursin (Lys‐His‐Gly‐NH2) is a B cell differentiation hormone derived from the bursa fabricii. The latter is a cloacal diverticulum and the site of B lymphocyte differentiation and selection in aves; also the bursa fabricii is involved in endocrine functions. Herein we demonstrate that in the chicken, the bursa fabricii and bursin are crucial to the ontogeny of both the pineal response to antigenic challenge and pineal circadian synthetic activity. In early embryonically bursectomized chickens, the plasma melatonin response to immunization by porcine thyroglobulin (Tg) was abolished. Also, the amplitudes of both plasma melatonin and pineal N‐acetyltransferase (NAT) circadian rhythms were reduced by 50%, whereas the activity of hydroxyindole‐O‐methyltransferase (HIOMT) remained unchanged. Conversely, administration of either minute amounts (100 pg, 100 fg) or highly dilute (5 × 10−27 g) bursin, with the exception of a highest dose (100 μg), to bursaless embryos induced recovery of normal antigen‐induced melatonin response and normal amplitudes of melatonin and NAT rhythms. These findings establish that early in embryonic life, the bursa fabricii and its derived signal (bursin) are essential for normal development of pineal synthetic activity and underline the efficacy of very dilute bursin as an informative signal.
5‐Methoxytryptophol and melatonin in children: Differences due to age and sex
Authors: Molina‐Carballo A. , Munoz‐Hoyos A. , Martin‐Garcia J.A. , Uberos‐Feritindez J. , Rodriguez‐Cabezas T. , Acuna‐Castroviejo D.
Published: February 2007

Abstract: It seems clear that the pineal hormone, melatonin (N‐acetyl‐5‐methoxytryptamine), is involved in the reproductive behavior of several animal species including humans. Moreover, several data also support a role for 5‐methoxytryptophol (ML), another pineal hormone, in the control of sexual processes. To test the role of ML in human reproductive axis, 128 healthy children, 68 boys and 60 girls, were studied. Each of these groups was divided in three age subgroups of 6, 11, and 14 years. A single blood sample (0900 hours) was obtained from each subject to determine melatonin, ML, FSH, LH, estradiol (girls), and testoterone (boys) by RIA. Statistical analysis of the data included ANOVA‐II (factor I: age, factor II: sex) and an analysis of covariance with age as covariate. A similar plasma melatonin concentration, with a significant decrease between 6 and 11 years, was found in boys and girls. Melatonin concentrations correlate well with initiation of the pubertal development in these children, although no sex differences were found. Concentrations of ML are approximately 50% of those of melatonin. In contrast to melatonin, ML levels show significant age and sex differences. Plasma ML concentration significantly increased in boys (P < 0.001) and decreased in girls (P < 0.001) after 8 years of age. These results support the hypothesis that, besides melatonin, other pineal compounds such as ML may be involved in the maturation process in humans. The pineal indole ML may also be used as a marker of the different chronobiology in the pubertal development in boys and girls.
Prenatal development of the sheep pineal gland: An ultrastructural study
Authors: Redondo Eloy , Franco Antonio J. , Regodon Sergio
Published: February 2007

Abstract: The ultrastructure of the pineal gland of 32 sheep embryos was studied from day 54 of development through birth. Embryos were arranged in four age‐groups, defined in terms of the most relevant histological features: group 1 (54 to 67 days of prenatal development), group 2 (71 to 92 days), group 3 (98 to 113 days), and group 4 (118 to 150 days). A primary cell type, designated the pinealoblast, was observed from 54 days until birth; ultrastructurally, this cell was found to contain all the organelles required for hormone synthesis. A second cell population, classified as interstitial cells by virtue of their location among pinealoblasts, appeared at 78 days gestation and persisted until birth. Interstitial cells were scarce and exhibited tropism for the perivascular space. From 118 days gestation until birth, a third cell type, termed the pigmented cell, was visible. Pigmented cells, whose ultrastructural characteristics differed from those of pinealoblasts, contained a large number of pigment granules of varying size and shape. The pineal gland of developing sheep embryos showed considerable innervation and abundant vascularization; this, together with certain ultrastructural characteristics, suggests that the gland has a secretory function in uterine life.
Microvesicle‐mediated exocytosis of glutamate is a novel paracrine‐like chemical transduction mechanism and inhibits melatonin secretion in rat pinealocytes
Authors: Yamada Hiroshi , Yamamoto Akitsugu , Yodozawa Susumu , Kozaki Shunji , Takahashi Masami , Morita Mitsuhiro , Michibata Hitoshi , Furuichi Teiichi , Mikoshiba Katsuhiko , Moriyama Yoshinori
Published: February 2007

Abstract: Mammalian pinealocytes are neuroendocrine cells that synthesize and secrete melatonin, these processes being positively controlled by norepinephrine derived from innervating sympathetic neurons. Previously, we showed that pinealocytes contain a large number of microvesicles (MVs) that specifically accumulate L‐glutamate through a vesicular glutamate transporter and contain proteins for exocytosis such as synaptobrevin 2 (VAMP2). These findings suggested that the MVs are counterparts of synaptic vesicles and are involved in paracrine‐like chemical transduction in the pineal gland. Here, we show that pinealocytes actually secrete glutamate upon stimulation by KC1 in the presence of Ca2+ at 37°C. The ability of glutamate secretion disappeared when the cells were incubated at below 20°C. Loss of the activity was also observed on successive stimulation, but it was recovered after 12 hr incubation. A low concentration of cadmium chloride or ω‐conotoxin GVIA inhibited the secretion. Botulinum neurotoxin E cleaved synaptic vesicle‐associated protein 25 (SNAP‐25) and thus inhibited the secretion. The released L‐glutamate stimulated pinealocytes themselves via glutamate receptor(s) and inhibited norepinephrine‐stimulated melatonin secretion. These results strongly suggest that pinealocytes are glutaminergic paraneurons, and that the glutaminergic system regulates negatively the synthesis and secretion of melatonin. The MV‐mediated paracrine‐like chemical transduction seems to be a novel mechanism that regulates hormonal secretion by neuroendocrine cells.
Use of melatonin in the treatment of paediatric sleep disorders
Authors: Jan James Emery , O'Donnell Maureen Eleanor
Published: February 2007

Abstract: A group of Vancouver health professionals, including the authors, have studied the use of oral melatonin in the treatment of chronic sleep disorders in children with disabilities since the Fall of 1991. This review article is based on the first 100 patients, half of whom were visually impaired or blind. Children with neurological, neuropsychiatric, and developmental disabilities are predisposed to chronic sleep‐wake cycle disturbances. Disorders such as blindness, deafblindness, mental retardation, autism, and central nervous system diseases, among others, diminish the ability of these individuals to perceive and interpret the multitude of cues for synchronizing their sleep with the environment. Melatonin, which benefitted slightly over 80% of our patients, appears to be a safe, inexpensive, and a very effective treatment of sleep‐wake cycle disorders. The oral dose of fast release melatonin taken at bed‐time ranged from 2.5 mg to 10 mg. Side effects or the development of tolerance have not been observed. Since the causes of sleep difficulties are extremely variable, not all children are candidates for treatment. For successful melatonin treatment, clinical experience is required, and the influences of other health problems and medications need to be considered. Further clinical and laboratory research in this field is imperative because melatonin treatment offers enormous health, emotional, social, and economic benefits to society, especially since multidisabled children with chronic sleep difficulties do not respond well to current therapeutic regimes.
6‐Sulphatoxymelatonin secretion in different locomotor activity types of the blind mole ratSpalax ehrenbergi
Authors: Ben‐Shlomo R. , Nevo E. , Ritte U. , Steinlechner S. , Klante G.
Published: February 2007

Abstract:6‐Sulphatoxymelatonin (aMT6S) excretion was examined in the urine of rhythmic and arrhythmic blind subterranean mole rats (Spalax ehrenbergi) to test the correlation between melatonin secretion (as represented by aMT6S) and variability in circadian locomotor activity. Activity pattern was tested in four males, first for a week under short photoperiod [light: dark (LD) 10: 14], followed by 10 days in constant darkness (DD). After several months the experiment was repeated under long photoperiod (LD 14: 10), followed by DD conditions. Under LD conditions all animals exhibited aMT6S excretion during the dark phase, with a decline just before the onset of light. No correlation was found between activity pattern and melatonin secretion. The animal with the highest melatonin secretion both under LD and DD had an arrhythmic locomotor pattern. The results suggest that in mole rats melatonin secretion and circadian locomotor activity are controlled by two different mechanisms. There were large differences in the aMT6S levels among individuals, suggesting the importance of duration of melatonin secretion over amplitude for gonadal development and thermoregulatory changes. During summer, i.e., before the breeding season, the animals keep a more stable aMT6S secretion than in winter, and the amplitude of secretion is higher under DD vs. LD conditions.