bluuebunny/crossref_metadata_2025 huggingface dataset:
Rough endoplasmic reticulum in the adrenaline and noradrenaline cells of the adrenal medulla: Effects of intracranial surgery and pinealectomy
Authors: Kachi Takashi , Takahashi Gen , Banerji Tapan K. , Quay Wilbur B.
Published: February 2007

Abstract: Adrenal medullas in 53‐day‐old rats of the nonoperated (NO) group (n = 31), the sham‐operated (SPX) group (n = 35) and the pinealectomized (PX) group (n = 38) were examined electron microscopically 14 days after surgery. Cell profiles showing solitarily and sparsely distributed rough endoplasmic reticulum (RER) were most frequent in the PX group (daily mean: 66.9%, 427/638), less in the NO (56.0%, 336/600), and least in the SPX (48.5%, 297/612) in adrenaline (A) cells (x2‐test: P < 0.001), while most frequent in the NO group (68.8%, 340/494), less in the PX (64.3%, 303/471), and least in the SPX (57.4%, 256/446) (P < 0.005) in noradrenaline (N) cells. Individual variation was less in A cells than in N cells. Cell profiles showing a large accumulation of RER was more frequent in A cells (N0:8.5%, SPX:13.1%, PX:7.7%) than in N cells (NO:2.8%, SPX:4.5%, PX:4.7%) (controls: P < 0.001). Sham pinealectomy increased a large accumulation of RER in A cells (P < 0.02) and a small aggregation of RER in N cells (P < 0.005) with opposite effects of pinealectomy (P < 0.005, P < 0.025). Pinealectomy decreased a small aggregation of RER without effects of sham pinealectomy in A cells (P < 0.001). Conclusions: (1) Accumulation or aggregation of RER in adrenomedullary chromaffin cells was influenced from the pineal gland either as or without effects of intracranial surgery, and (2) RER in adrenomedullary chromaffin cells showed differences due to cell types.
Synergistic action of melatonin and vasoactive intestinal peptide in stimulating cyclic AMP production in human lymphocytes
Authors: Lopez‐Gonzalez Miguel A. , Calvo Juan R. , Osuna Carmen , Rubio Amalia , Guerrero Juan M.
Published: February 2007

Abstract: In the present study we investigated the synergistic effect of melatonin and vasoactive intestinal peptide (VIP) on cyclic AMP production in human blood lymphocytes. As shown by our group previously, VIP alone behaved as a potent activator of cyclic AMP production in human lymphocytes. On the other hand, melatonin alone did not affect the intracellular levels of cyclic nucleotide at any time or dose studied. However, when cells were incubated with melatonin plus VIP, melatonin potentiated the effect of the peptide. This effect can be observed in the presence of physiological doses of both melatonin (10–100 pM) and VIP (1–100 pM). The effect is specific for VIP because with other peptides belonging to the secretin‐VIP family the effect was not observed. Results suggest that melatonin, in conjunction with VIP, may directly participate in the regulation of immune function in the human.
Regulation of the androgen receptors in the Harderian gland of the male Syrian hamster: Influence of photoperiod, castration, and chronic melatonin treatment
Authors: Stankov Bojidar , Lucini Valeria , Negri‐Cesi Paola , Cozzi Bruno , Fumagalli Pietro , Fraschini Franco
Published: February 2007

Abstract: Male Syrian hamsters that were exposed for 8 weeks to short photoperiod (LD 10:14) or treated with melatonin in the late afternoon under long photoperiod conditions (LD 14:10) had a significantly higher content of androgen receptors in the Lipidex‐purified soluble fractions isolated from the Harderian glands as compared to the long photoperiod (LD 14:10) exposed controls. Simultaneous computer‐assisted analyses of all series of saturation and competition experiments revealed that the numerical value of the apparent Kd, as determined by using the synthetic androgen R‐1881 (methyltrienolone), was not different between the experimental groups, and ranged from 0.050 to 0.067 nM. Of the principal natural androgens, testosterone (T) was most potent in inhibiting methyltrienolone binding to the receptor (Ki values from 0.33 to 0.55 nM), and 5α‐dihydrotestosterone (DHT) and α4‐androstenedione (AD) were less effective (Ki values between 1 and 1.9 nM). In the hypothalami and pituitaries of the same animals, used in parallel control assays, DHT was twice as potent as T. Short‐term castration (24 hr post‐orchidectomy) did not result in significant changes in the receptor binding characteristics. Following 8 weeks exposure to a long photoperiod (LD 14:10) the Bmax values demonstrated a four‐fold increase in castrated animals (179 fmoles/mg protein vs. 47 fmoles/mg protein) over intact controls. The relative binding affinity of the major androgens under these conditions remained unchanged, with the exception of AD, where a five‐fold increase in the numerical Ki values (decrease in the binding affinity) was recorded (Ki = 9.6 nM). Studies on in vitro metabolism of the natural androgens by the cytosol during incubation under conditions identical to those employed in the binding studies revealed that in the normal intact animal AD is metabolized to T in elevated amounts. The ability of the Harderian gland to make this conversion is dramatically diminished following long‐term castration. This could explain the apparent “shift” in the high affinity of AD toward a much lower one. Testosterone, however, was not further metabolized. No DHT was formed and small amounts of AD were recovered. Thus, in the androgen receptor system of the hamster Harderian gland testosterone appears to be a strong androgen per se, binding to the receptor with affinity higher than that of DHT. This receptor system is apparently flexible in its response to changes in the photoperiod and to removal of the natural steroids from the endogenous milieu following long‐term castration. Both situations are accompanied by a significant increase in receptor numbers, though castration seemingly results in concomitant changes in the androgen metabolism in the gland.
A phase‐dependent delay of the chick pineal rhythm in rate of thymidine incorporation by brief exposure to ouabain
Authors: Wainwright S.D. , Wainwright Lillian K.
Published: February 2007

Abstract: Cultured chick pineal glands show a persistent rhythm in the rate of cumulative incorporation of thymidine into DNA [Wainwright and Wainwright, 1989]. In this study we have examined the effects of a pulse‐exposure to ouabain in the dark on the first day of culture upon thymidine incorporation during the second and third days of culture in the dark with ouabain‐free medium. The phase of the rhythm in rate of thymidine incorporation was delayed by a 4‐hr exposure to 100 μM ouabain commencing in the final hour of the photoperiod, but not by a 2‐hr exposure or by 10 μM ouabain. This effect was phase‐dependent and not seen when exposure to ouabain began earlier in the photoperiod. The phase delay caused by ouabain was not due to a persistent direct inhibition of the process of thymidine incorporation. The phase‐shift due to exposure to ouabain was superimposed on a phase delay caused by renewal of culture medium 4 hr after explanting the glands into culture.
Effects of melatonin on water metabolism and renal function in male Syrian hamsters (Mesocricetus auratus)
Authors: Richardson Bruce A. , Studier Eugene H. , Stallone John N. , Kennedy Colleen M.
Published: February 2007

Abstract: The pineal indoleamine, melatonin, has been shown to influence many physiological systems within the mammalian body. Few studies, however, have examined the influence of melatonin on renal function. This study investigated the effects of melatonin on water metabolism and renal function. Young adult male Syrian hamsters were maintained on a long photoperiod (LD 14:10) in metabolic cages. The animals received daily (1700) injections of either control vehicle or 25 μg of melatonin for 85 consecutive days. Melatonin administration resulted in significant increases in water consumption and urine production. Water budgets were also significantly influenced by melatonin, as were urinary osmolality, urinary sodium, and potassium concentrations, but urinary calcium concentrations were essentially unaltered. When excretion rates for sodium, potassium, and calcium were calculated, no differences were observed between the vehicle control and melatonin‐treated groups. Injections of melatonin also significantly decreased plasma antidiuretic hormone (ADH). These results demonstrate that afternoon injections of melatonin can alter renal function, which may involve direct (i.e., on ADH secretion and/or thirst mechanisms) or indirect (i.e., behavioral) effects.
Calcium channel blockers in vivo inhibit serotonin N‐acetyltransferase (NAT) activity in chicken retina stimulated by darkness and not by agents elevating intracellular cyclic AMP level
Authors: Zawilska Jolanta B. , Wawrocka Marlena , Zurawska Ewa , Nowak Jerzy Z.
Published: February 2007

Abstract: The molecular mechanism underlying the role of calcium influx in the regulation of retinal serotonin N‐acetyltransferase (NAT) activity was studied in vivo in chickens. Systemic administration of organic antagonists of voltage‐sensitive calcium channels (VSCC), i.e., nimodipine and nifedipine, resulted in a marked suppression of the nocturnal increase of NAT activity in chicken retina. In contrast, NAT activity stimulated by nonhydrolysable analogs of cyclic AMP (dibutyryl‐cyclic AMP and 8‐bromo‐cyclic AMP), forskolin, a direct activator of adenylate cyclase, and by phosphodiesterase inhibitors (aminophylline and 3‐isobutyl‐l‐methylxanthine), was not significantly affected by various tested VSCC antagonists. The inhibitory effect of nimodipine on the dark‐dependent increase in NAT activity of chicken retina was abolished by Bay K 8644, a selective VSCC agonist. The results presented in this paper indicate an important role of calcium influx through L‐type of VSCC in the induction of NAT activity in chicken retina, and suggest that a requirement of calcium ions in the process of NAT induction in the retina may be primarily at the level of cyclic AMP production.
Serum prolactin and luteinizing hormone levels and the activities of hypothalamic monoamine oxidase A and B and phenylethanolamine‐N‐methyl transferase are changed during sexual maturation in male rats treated neonatally with melatonin
Authors: Moreno Maria L. , Villanua Maria A. , Esquifino Ana I.
Published: February 2007

Abstract: Male rat pups were given a single dose of melatonin on day 5 of age. On days 30, 45, and 60, prolactin (PRL), luteinizing hormone (LH), follicle‐stimulating hormone (FSH), and testosterone (T) were measured in serum and monoamine oxidase A (MAO A) activity, monoamine oxidase B (MAO B), and phenylethanolamine‐N‐methyl transferase (PNMT) activity were measured in the hypothalamus. Melatonin administration increased serum PRL levels at all ages studied. Serum LH levels were decreased in the melatonin treated group on day 30, but levels were elevated on days 45 and 60 of age as compared to controls. LH response to luteinizing hormone‐releasing hormone (LHRH) only increased in melatonin treated animals at 30 days of age. Serum T levels decreased with melatonin treatment at 30 days of age, but increased on days 45 and 60 of age. T response to human chorionic gonadotropin (hCG) was blunted by melatonin treatment at 30 days of life. Hypothalamic MAO A activity increased, after neonatal melatonin administration, at 30 and 45 days of age and decreased at 60 days of life. Early neonatal melatonin administration increased MAO B and PNMT activities on day 45. These findings suggest that neonatal melatonin administration induces an earlier sexual maturation in male rats, possibly related to PRL, LH, MAO, and PNMT increases.
The immunoneuroendocrine role of melatonin
Authors: Maestroni Georges J. M.
Published: February 2007

Abstract: A tight, physiological link between the pineal gland and the immune system is emerging from a series of experimental studies. This link might reflect the evolutionary connection between self‐recognition and reproduction. Pinealectomy or other experimental methods which inhibit melatonin synthesis and secretion induce a state of immunodepression which is counteracted by melatonin. In general, melatonin seems to have an immunoenhancing effect that is particularly apparent in immunodepressive states. The negative effect of acute stress or immunosuppressive pharmacological treatments on various immune parameters are counteracted by melatonin. It seems important to note that one of the main targets of melatonin is the thymus, i.e., the central organ of the immune system. The clinical use of melatonin as an immunotherapeutic agent seems promising in primary and secondary immunodeficiencies as well as in cancer immunotherapy. The immunoenhancing action of melatonin seems to be mediated by T‐helper cell‐derived opioid peptides as well as by lymphokines and, perhaps, by pituitary hormones. Melatonin‐induced‐immuno‐opioids (MHO) and lymphokines imply the presence of specific binding sites or melatonin receptors on cells of the immune system. On the other hand, lymphokines such as ‐γ‐interferon and interleukin‐2 as well as thymic hormones can modulate the synthesis of melatonin in the pineal gland. The pineal gland might thus be viewed as the crux of a sophisticated immunoneuroendocrine network which functions as an unconscious, diffuse sensory organ.
In vivo and in vitro effects of the pineal gland and melatonin on [Ca2++ Mg2+]‐dependent ATPase in cardiac sarcolemma
Authors: Chen Li‐Dun , Tan Dun‐Xian , Reiter Russel J. , Yaga Ken , Poeggeler Burkhard , Kumar Pramod , Manchester Lucien C. , Chambers James P.
Published: February 2007

Abstract: The possible diurnal variation in cardiac [Ca2++ Mg2+]‐dependent ATPase (Ca2+ pump) activity and the influence of pinealectomy and melatonin on this enzyme in rat heart have been studied. Lowest levels of cardiac sarcolemma] membrane [Ca2++ Mg2+]‐dependent ATPase activity were measured in late afternoon in rats kept under a 14:10 light:dark cycle. Late in the dark phase the enzyme activity began to increase with the rise continuing until 0900, 3 hr after light onset. These time‐dependent changes in [Ca2++ Mg2+]‐dependent ATPase activity did not occur in either pinealectomized or light‐exposed rats suggesting that melatonin, secreted from the pineal gland during the night, induces the change in [Ca2++ Mg2+]‐dependent ATPase activity. In vitro studies in which cardiac tissue was incubated in the presence of melatonin over a wide range of doses showed that this indole stimulated the Ca2+ pump. The half‐maximal effect of melatonin was observed at a melatonin concentration of 28 ng/ml. These findings suggest that the daily change in [Ca2++ Mg2+]‐dependent ATPase activity in the sarcolemma of heart tissue is a result of the circadian rhythm in pineal melatonin production and secretion. These findings may be applicable to normal cardiac physiology.
Antigonadal effects of two novel melatonin analogues in adult Djungarian hamsters
Authors: Chong Nelson W.S. , Sugden David
Published: February 2007

Abstract: This study examined the effects of two novel melatonin analogues in adult Djungarian hamsters housed under long photoperiod (LD 16:8). Daily injection (10 μg, s.c.) of either melatonin, 5‐methoxy N‐butanoyltryptamine (bMT), or 5‐methyl N‐butanoyltryptamine (5‐MebT) 3 hr before lights off for 8 weeks led to a significant decrease in paired testis weight compared to vehicle‐injected controls. The reduction in testis weight was of similar magnitude with melatonin and bMT, but 5‐MebT was not as effective. The affinity of the analogues was determined in competition experiments using chicken brain membranes and 2‐[125I]iodomelatonin (2‐[125I]aMT). Replacing the N‐acetyl side‐chain of melatonin with an N‐butanoyl group increased affinity for the chicken brain 2‐[125I]aMT binding site, but exchanging the 5‐methoxy group of melatonin for a 5‐methyl group reduced affinity. These studies show that these analogues not only inhibit 2‐[125I]aMT binding in vitro but also mimic melatonin's antigonadal activity in vivo.
Characterization and localization of delta opioid binding sites in the bovine pineal gland
Authors: Aloyo Vincent J. , Battisi Wendy P. , Pazdalski Paul S.
Published: February 2007

Abstract: Opioid binding sites in the bovine pineal were characterized using the highly selective delta opioid agonist 3H‐[D‐Pen2, pCl‐Phe4, D‐Pen5] enkephalin (DPDP(Cl)E). Pineal membranes possess a single class of high affinity binding sites for this delta ligand (Kd= 0.26 nM; Bmax= 250 fmol/mg protein). The specific opioid antagonist naloxone dose dependently inhibited 3H‐DPDP(C1)E binding, confirming that this ligand is indeed binding to opioid receptors. The delta selective ligands deltorphin and [D‐Pen2,5] enkephalin (DPDPE) were much more potent than the mu selective compounds dermorphin and [D‐Ala2, MePhe4 Gly5‐ol]enkephalin (DAMGO) in inhibiting 3H‐DPDP(Cl)E binding. These results demonstrate that in bovine pineal membranes, DPDP(Cl)E binds to delta opioid sites. Autoradiographic studies showed a uniform distribution of 3H‐DPDP(Cl)E binding over the bovine pineal in the sections we analyzed. This distribution suggests that delta opioid binding sites are associated with pinealocytes which account for the majority of cell types in the pineal. However, it is not possible to rule out that these receptors may also be associated with other cell types which are present in the bovine pineal. The density and widespread distribution of delta opioid receptors supports the hypothesis that endogenous opioid peptides directly modulate pineal function.
Melatonin and human puberty: Current perspectives
Authors: Cavallo Anita
Published: February 2007

Abstract: Many studies of melatonin in human puberty are difficult to interpret in light of methodological considerations such as the use of single blood samples collected either during the day or at night; a small number of observations; the failure to include the temporal characteristics of melatonin secretion; the definition of puberty by the use of broad clinical features without use of hormonal markers of puberty; the lack of control for the actual duration and intensity of light exposure during the days preceding the study; and the cross sectional nature of most studies. The few studies that have examined the plasma melatonin rhythm in humans by multiple blood sampling overnight or over 24 hr suggest that normal pubertal development (as well as normal ovarian function) are not linked to alterations in the plasma melatonin profile. There is, however, some evidence to suggest that disorders of the hypothalamic‐pituitary‐gonadal axis (delayed puberty, precocious puberty, hypothalamic amenorrhea) may be linked to altered plasma melatonin profile, at least in some cases. These findings, taken together with strong evidence for the role of the pineal gland in the reproductive function of other vertebrate species, render unlikely the inference that the pineal gland has no role in the development and function of the human reproductive axis. Thus, one may speculate that a pineal‐puberty relation does exist in humans and that the research techniques applied to date have been inadequate to uncover this relation. Greater knowledge might be gained from studies of melatonin metabolism during growth and pubertal maturation, from longitudinal studies of the melatonin rhythm under rigorously controlled conditions of light exposure, and, perhaps, from the development of research strategies to explore the human melatonin receptor in vivo.
Fine structure of the free‐living parakeet pineal in relation to the breeding cycle
Authors: Prasadan T.N. Krishna , Kotak Vibhakar C.
Published: February 2007

Abstract: Seasonal changes in the ultrastructure of the free‐living Rose‐Ringed Parakeet Psittacula krameri pineal were examined in relation to the sub‐tropical environment and seasonal reproduction. Dark and light pinealocytes of the presumptive neuroendocrine cell line predominated, while supporting cells, ependymal cells, myelinated and non‐myelinated nerve fibers with nerve endings, and regressed photoreceptor elements were also observed. Unlike in pineals of many animals, particularly mammals, the presence of dense‐core vesicles (DCVs) with varying core density, and absence of clear vesicles and vacuoles with flocullent material, indicate the involvement of DCVs in the synthesis and secretion of pineals principle/s. In November (pre‐breeding) when the day length registered a drop to LD 10:14, pinealocytes showed significantly decreased and smaller DCVs and mitochondria, nuclei with heterochromatin, and greater distribution of glycogen and lipid droplets, all indicating low pineal metabolic activity. During the shortest day regime from December to March, when the birds peaked breading, the number and size of DCVs and mitochondria increased, and Golgi body‐endoplasmic reticulum‐lysosome complex (GERL) was very well defined. Images of DCVs suggested possible secretion of pineal principle/s by dissolution, and exocytosis. Coincidence of these features with peak gonadotrophic (circulating LH) and spermatogenic and testicular endocrine activity described previously suggested an active turnover of pineal products during this short day length regime when parakeets breed. In contrast, during the post‐breeding season (April onwards), when the day‐length increased to LD 13:11 and hypophyseal‐gonadal function was down, nuclei and RER continued to show active profile, the Golgi body and associated complex were moderately seen, and the DCVs and mitochondria were significantly smaller and lesser. It is therefore probable that the pineal is an important relay to translate cues related to less drastic sub‐tropical environmental change into DCV‐linked neurohormones that in turn may be involved in modulating seasonal breeding in parakeets.
Absence of circadian rhythm in the disposition of melatonin in the cow
Authors: Berthelot Xavier , Ravault Jean Paul , Concordet Didier , Ferney Jean , Toutain Pierre Louis
Published: February 2007

Abstract: Five adult pasture‐bred Prim Holstein cows were used to document the time invariance of melatonin disposition in the cow. Melatonin was administered by an intravenous route as a bolus (5 μg/kg of body weight) at either 1430 or 2230. Data were analysed according to a three‐compartment open model with melatonin elimination from the central compartment. The mean (±SD) kinetic parameters describing melatonin disposition, during day and night, respectively, were plasma clearances: 0.0267 ± 0.0084 1/kg per min and 0.0229 ±0.0031 1/kg per min; steady state volume of distribution: 0.826 ±0.229 1/kg and 0.780 ±0.193 1/kg; terminal half lives: 58.9 ±23.7 min and 64.1 ±33.7 min; mean residence times: 32.0 ±8.8 min and 33.9 ±6.2 min. No statistical difference was found between diurnal and nocturnal values for these parameters. These results support the concept of time invariance for melatonin kinetics in cattle and validate the use of diurnal experiments for the study of melatonin kinetics.
Putative melatonin receptors in the male guinea pig kidney
Authors: Song Y. , Poon A.M.S. , Lee P.P.N. , Pang S.F.
Published: February 2007

Abstract: The direct action of pineal melatonin on the renal system is supported by our demonstration of 2‐[125I]iodomelatonin binding sites in the male guinea pig kidney. Scatchard analyses and Hill coefficients revealed a single type of binding site with an equilibrium dissociation constant (Kd) of 22.3 ±1.6 pmol/1 and a maximum binding density (Bmax) of 0.99 ±0.03 fmol/mg protein (n = 7) at mid‐light. There was no significant difference in the Kd and Bmax values between kidney tissues collected at the middle of light and dark periods. The pharmacological profile of these 2‐[125I]iodomelatonin binding sites indicated high specificity for melatonin, 2‐iodomelatonin and 6‐chloromelatonin while kinetic studies generated a Kd value of 28.4 ±7.3 pmol/1 (n = 5) which was comparable to that determined from Scatchard transformations. Our results suggest that these binding sites are stable, reversible, saturable, specific, and of high affinity. Regional distribution study showed that specific binding of 2‐[125I]iodomelatonin was 8‐fold higher in the cortical region than that in the medullary region. Studies of subcellular distribution showed that 59.3% of binding sites were localized in crude nuclear fractions followed by crude mitochondrial fractions (22.3%) and crude microsomal fractions (18.3%) with no detectable binding in cytosolic fractions. Our present findings suggest the presence of putative melatonin receptors in the guinea pig kidney, which support the hypotheses of melatonin‐regulated renin secretion together with renal excretory functions via melatonin receptors.
Effects of melatonin and the melatonin receptor agonist S‐20098 on the vigilance states, EEG spectra, and cortical temperature in the rat
Authors: Tobler Irene , Jaggi Karin , Borbély Alexander A.
Published: February 2007

Tobler I, Jaggi K, Borbély AA. Effects of melatonin and the melatonin receptor agonist S‐20098 on the vigilance states, EEG spectra, and cortical temperature in the rat. J. Pineal Res. 1994: 16: 26–32.

The effects of melatonin (3 mg/kg i.p.) and the melatonin receptor agonist S‐20098 (3 mg/kg i.p.) on the vigilance states, electroencephalogram power spectra (0.25–25.0 Hz), and cortical temperature were determined in eight rats in the first 6‐hr interval of the 12‐hr light period. Compared to the vehicle injection both compounds reduced the power density in non‐rapid eye movement sleep in the low frequency range (1–8 Hz) but did not affect the vigilance states and brain temperature. The present findings do not indicate that the stimulation of the melatonin receptor exerts a hypnotic effect at doses that had been shown to affect the circadian rest‐activity rhythm.
Characterization of high‐affinity melatonin binding sites in purified cell nuclei of rat liver
Authors: Acuña‐Castroviejo Dario , Reiter Russel J. , Menendez‐Pelaez Armando , Pablos Maria I. , Burgos Alejandro
Published: February 2007

Acuna‐Costroviejo D, Reiter RJ, Menéndez‐Peláez A, Pablos MI, Burgos A. Characterization of high‐affinity melatonin binding sites in purified cell nuclei of rat liver. J. Pineal Res. 1994: 16: 100–112.

High‐affinity 2‐125I‐iodomelatonin binding sites in homogenates of purified cell nuclei from rat liver were localized and characterized using biochemical binding techniques. Binding at these sites was found to be rapid, reversible, saturable, and to demonstrate pharmacological selectivity. At 0°C, binding reached equilibrium in about 10 min. Scatchard analysis of the data at equilibrium revealed a single class of binding sites with a dissociation constant of KD= 190 ± 47 pM, Bmax= 9. 8 ± 0. 6 fmol/mg protein, and a Hill coefficient of nH= 1. 02 ± 0. 034. Kinetic analysis of the association and dissociation curves indicated a kinetic KD= 148 ± 41 pM, which is in good agreement with the value obtained at equilibrium. The specific binding of 2‐125I‐iodomelatonin (45 pM) (0. 51 ± 0. 04 fmol/mg protein) was significantly improved (0. 79 ± 0. 04 fmol/mg protein) when the homogenates of purified liver cell nuclei were reinsulated with DNase (2 μg/ml at 37°C for 20 min) before being used in binding experiments. After the addition of either proteinase K or trichloroacetic acid to DNase‐treated purified cell nuclear homogenates, the specific binding disappeared. This suggests that the specific binding of 2‐125I‐iodomelatonin in liver cell nuclei is associated with nuclear protein. Competition experiments show that N‐acetyl‐serotonin (Ki= 81. 3 nM) was more potent than 5‐hydroxytryptamine (Ki > 1 μM) and 5‐methoxytryptamine (Ki≫ 10 μM) in inhibiting 2‐125I‐iodomelatonin binding (Ki melatonin = 146 pM). These data indicate that specific 2‐125I‐iodomelatonin binding sites exist in the cell nuclei of rat liver, and that they may comprise a locus for the intracellular action of melatonin. The correlation between the KD and Bmax values with melatonin concentrations in nuclei suggest that these binding sites may be a physiological melatonin receptor, which could explain the described genomic effects of the pineal hormone.
Effects of chronic melatonin administration on adrenal medulla catecholamine metabolism in adult male golden hamsters
Authors: Esquifino Ana I. , Moreno Maria L. , Steger Richard W.
Published: February 2007

Esquifino AI, Moreno ML, Steger RW. Effects of chronic melatonin administration or adrenal medulla catecholamine metabolism in adult male golden hamsters. J. Pineal Res. 1994; 16: 154–158.

The role of melatonin on adrenal medullary function was evaluated in adult golden (Syrian) hamsters injected daily at either 0800 or 1600 with melatonin (25 μxg/hamster) or vehicle (0. 1% ethanol in saline). Sixty days after initiation of treatment and 16 or 24 hr after the last injection of melatonin, animals were killed by decapitation and blood and tissue collected. Plasma prolactin levels were reduced by chronic administration of melatonin only when animals were treated at 1600. Tyrosine hydroxylase (TH) activity in the adrenal medulla was not changed by either morning or afternoon administration of melatonin. Phenylethanolamine‐N‐methyl transferase (PNMT) was changed by afternoon administration of melatonin. Morning and afternoon melatonin injections led to the reduction of both adrenal monoamine oxidase (MAO) and catechol‐O‐methyl transferase (COMT) activities although the afternoon injections led to a greater magnitude of change. Norepinephrine and epinephrine contents were significantly reduced by morning melatonin administration but were not changed by afternoon administration of the hormone. These data suggest that melatonin has direct and possibly indirect effects on adrenal medullary function in the hamster. However, further studies will be required to characterize the effects of melatonin on catecholamine synthesis and release and the physiological significance of these effects.
Calcium, calcification, and melatonin biosynthesis in the human pineal gland: A postmortem study into age‐related factors
Authors: Schmid Hermann A. , Requintina Pura J. , Oxenkrug Gregory F. , Sturner William
Published: February 2007

Schmid HA, Requintina PJ, Oxenkrug GF, Sturner W. Calcium, calcification, and melatonin biosynthesis in the human pineal gland: A postmortem study into age‐related factors. J. Pineal Res. 1994:16:178–183.

It is believed that pineal calcification may be age‐associated and that the well‐demonstrated age‐related decline in melatonin biosynthesis may be an expression of an alteration in calcium homeostasis in the pinealocyte. Prior correlations of melatonin to calcium deposition and age were made on the basis of radiological or semiquantitative analysis. In this postmortem study of 33 subjects (age range 3 months to 65 years) calcium deposits measured by atomic absorption spectrometry correlated positively with age in day and night samples (day: r = 0.56, P < 0.05; night: r = 0.818, P < 0.001). Nighttime (2200 h to 0800 h) pineal melatonin content (HPLC fluorometry) was higher than daytime melatonin levels (nighttime 3.80 ± 0.3 vs. daytime 0.85 ± 0.4 ng/mg protein). Nighttime calcium levels in the supernatant correlated negatively with melatonin content (r =−0.59, P < 0.05).
Elevation of cyclic GMP levels in the rat pineal gland induced by nitric oxide
Authors: Guerrero Juan M. , Reiter Russel J. , Poeggeler Burkhard , Chen Li‐Dun , Tan Dun‐Xian
Published: February 2007

Guerrero JM, Reiter RJ, Poeggeler B, Chen L‐D, Tan D‐X. Elevation of cyclic GMP levels in the rat pineal gland induced by nitric oxide. J Pineal Res. 1994:16:210–214.

The present paper reports that nitric oxide (NO) released by sodium nitroprusside (SNP) is a potent activator of rat pineal cyclic GMP production without affecting cyclic AMP synthesis. Other drugs such as isoproterenol, vasoactive intestinal peptide, and peptide histidine isoleucine were ineffective in stimulating cyclic GMP production, but activated cyclic AMP production. However, L‐arginine, the physiological precursor of NO, did not activate either cyclic GMP or NO synthesis. Because L‐arginine failed to activate cyclic GMP production, results suggest that NO is not produced in the pineal gland, but behaves as a potent regulator of this cyclic nucleotide.
Identification and characterization of 2[125I]‐iodomelatonin binding sites in the rat epididymis
Authors: Yu Zong‐Han , Chow P. H. , Pang Shiu‐Fun
Published: February 2007

Yu ZH, Chow PH, Pang S‐F. Identification and characterization of 2[125I]iodomelatonin binding sites in the rat epididymis. J. Pineal Res. 1994;17:195–201.

Putative melatonin receptors in different parts of the male reproductive system of rats (Sprague‐Dawley), mice (ICR), hamsters (Syrian) and guinea pigs (Dunkin‐Hartley), rat epididymal sperm, and boar and human semen were studied by a radioreceptor assay using 2[125I]iodomelatonin as the radioligand. There was limited or no detectable binding of 2[l25I]iodomelatonin to membrane preparations of rat testis, seminal vesicles, prostate, or sperm from rat, human, and boar. However, significant bindings of 2[125I]iodomelatonin to the epididymides of rat, mouse, hamster, and guinea‐pig were demonstrated. The relative binding capacities of 2[125I]iodomelatonin to the distal epididymal segment in different rodent species was of the order rat mouse hamster guinea pig. The relative number of binding sites was much lower in the proximal segment than in the distal segment of epididymis. 2[125I]iodomelatonin binding to the distal segment of rat epididymis was studied in detail. The binding sites fulfilled all criteria for a receptor site; being stable, saturable, reversible, and of high affinity. The binding had an equilibrium dissociation constant (Kd) of 62.6 ± 7.79 pmol/1 (n = 7) and a density (Bmax) of 1.55 ± 0.16 fmol/mg protein (n = 7). The Hill coefficient approached 1. 0, suggesting a single class of 2[125I]iodomelatonin binding sites. Pharmacological studies revealed that these 2[125I]iodome‐latonin binding sites were specific for melatonin receptors. In addition, there was an age‐related change in the 2[125I]iodomelatonin binding sites in the rat distal epididymal segment. The binding increased from a lower value in 1‐month‐old rats to a higher adult value in the l1/i‐ to 24‐month‐old animals. The demonstration of 2[125I]iodomelatonin binding sites in the epididymis indicates the presence of melatonin receptors. A high binding level in the distal epididymal segment suggests the possible participation of melatonin in the process of sperm maturation.
Influence of prenatal photoperiod on postnatal plasma concentrations of progesterone and prolactin in female red deer (Cervus elaphus) reared in constant equatorial photoperiod
Authors: Adam Clare L. , Kyle Carol E. , Young Pauline , Hirst David J.
Published: February 2007

Abstract: Prenatal photoperiod influences postnatal prolactin secretion and the timing of reproductive development in male red deer reared from birth in a constant equatorial photoperiod (12: 12 light: dark). The present trial investigated whether a similar phenomenon occurs in female red deer. Female deer whose mothers had been exposed for the last 14 weeks of gestation to long (group L, 18: 6 light: dark) or short day length (group S, 6: 18 light: dark) were kept from birth in constant equatorial day length with food available ad libitum. Both groups showed similar live‐weight gain to 90–100 weeks of age. Blood samples taken once or twice weekly were analyzed for progesterone and prolactin. Progesterone concentrations indicated that there was no difference between the groups in the timing of the first incidence of ovarian (luteal) activity, which occurred at a normal or late age for natural puberty (67 weeks or older). Only one individual per group exhibited normal repeated luteal cyclicity since there was a high incidence of irregular or abnormal luteal function. Plasma prolactin concentrations at birth were higher in group L than group S (P < 0.001). Thereafter, although the mean and peak values did not differ significantly between the groups, there was a significant difference in the pattern of secretion; deer in group L showed significant clustering of prolactin peaks (P < 0.01) at a mean age of 48 weeks, whereas deer in group S showed a random distribution of peaks. Therefore, for female red deer raised in constant equatorial photoperiod, prenatal long day lengths did not advance timing of puberty. However, the long‐term pattern of prolactin secretion tended to be synchronized by long but not by short day lengths experienced prenatally.
Effects of photoperiod on pineal melatonin in the marsh rice rat (Oryzomys palustris)
Authors: Edmonds Kent E. , Rollag Mark D. , Stetson Milton H.
Published: February 2007

Abstract: Pineal melatonin content was examined under four different photoperi‐ods (10L: 14D, 12L: 12D, 14L: 10D, and 16L: 8D) in adult female rice rats (Experiment 1). Pineal melatonin was basal during the light and increased beginning 1 hr after lights off. Within 2 hr after lights off, melatonin increased to levels that were maintained throughout the dark period. In all but one photoperiod (10L: 14D), melatonin remained elevated prior to light onset and decreased markedly within one hour after lights on. In addition, the duration of pineal melatonin was inversely related to the length of the photoperiod. In Experiment 2, the time course of pineal melatonin content on 16L: 8D was examined every 20 min during the first hour after lights off and the first hour after lights on. Melatonin content increased gradually during the first hour and decreased markedly within 20 min after lights on. These data show that pineal melatonin in female rice rats is regulated by photoperiod.
Parallel nocturnal secretion of melatonin and testosterone in the plasma of normal men
Authors: Schulz P. , Chardon F. , Agosti R. Degli , Schaad N. , Rivest R.W.
Published: February 2007

Abstract: Differences and similarities in the temporal organization of hormone secretion in plasma reflect the activity of CNS pacemakers. One aspect of this activity, the temporal synchronization of the secretion of different hormones is still poorly understood. We report the analysis of melatonin and testosterone plasma concentrations during two nights in 6 normal healthy young men. Blood was collected every 20 min between 2040 and 0640. Plasma testosterone concentrations increased by 1.5‐ to 2‐fold during the second part of the night, and melatonin by 2.5‐ to 4‐fold. In each subject, the individual temporal pattern of melatonin was quite stable over the two nights of sampling, while testosterone profiles showed fluctuations. There was a high degree of parallelism in these two hormones nocturnal secretion. These results, together with previous studies, suggest that melatonin might entrain the nocturnal secretion of testosterone.
Microvascularization of the pineal gland in the freshwater turtle, Pseudemys scripta elegans (Reptilia): A scanning electron microscopic study of vascular corrosion casts
Authors: Kleiter Natascha , Lametschwandtner Alois
Published: February 2007

Abstract: Gross supply, microvascular patterns, and drainage routes of the pineal gland and its vascular relations with associated structures (dorsal sac, paraphysis, choroid plexus of the third ventricle) were studied by scanning electron microscopy of microvascular corrosion casts in 10 specimens of the freshwater turtle, Pseudemys scripta elegans. Light microscopy of tissue sections (one transverse and one longitudinal series) served to attribute cast vascular territories to anatomical structures. The tubular pineal gland body is supplied bilaterally by small branches of the saccular artery, a branch of the lateral choroidal artery. Branches of the diencephalic artery supply the pineal stalk. The pineal gland microvascular bed is a two‐dimensional network that embraces the tubular gland. The network is made up mainly of venules with few true capillaries. Venules draining the ventral surface of the pineal gland body join those coming from the choroid plexus of the third ventricle and drain into the sagittal sinus. The less dense vascular network embracing the dorsal surface of the pineal body drains directly into the sagittal sinus. The pineal stalk drains into the diencephalic vein or directly into the sagittal sinus. No efferent (venous) vascular connections capable as transport route for pineal secretions toward surrounding telencephalic, diencephalic, or mesencephalic areas were found.
Daily variation in the content of indoleamines, catecholamines and related compounds in the pineal gland of Syrian hamsters kept under long and short photoperiods
Authors: Miguez J. M. , Recio J. , Vivien‐Roels B. , Pévet P.
Published: February 2007

Abstract: This study examined the diurnal changes in the content of 5‐hydroxytryptophan (5‐HTP), serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐HIAA), N‐acetylserotonin (NAS), melatonin, 5‐methoxytryptophol (5‐ML), noradrenaline (NA), dopamine (DA), and 3,4‐dihydroxyphenylacetic acid (DOPAC) in the pineal gland of Syrian hamsters kept under long (14L: 10D) and short (10L: 14D) photoperiods. The nocturnal increase in NAS and melatonin levels was dependent upon the prevailing photoperiod, with a prolonged duration when the night lengthened. In both photoperiods, NAS and melatonin contents increased several hours after the onset of darkness, and, in animals kept in short photoperiod, the levels of both compounds began to decrease before light onset. On the contrary, decreases were noted in 5‐HT, 5‐HIAA, and 5‐ML contents during the night, which was directly proportional to the dark phase. 5‐HTP levels did not show a rhythmic variation. Correlations between the mean values of 5‐HT‐related compounds showing daily rhythms were very high when group means were compared, but they decreased when values from individual animals were considered. In addition, when correlations were calculated on per‐animal basis during the night phase, a weak negative correlation was found for 5‐HT vs NAS and 5‐HT vs melatonin, although the correlation of 5‐HT with positively 5‐HT‐correlated compounds (5‐HIAA and 5‐ML) continued to be high. These results indicate that the nocturnal increase in the N‐acetyl transferase activity is the major factor generating the rhythm of pineal 5‐HT content, but that other photoperiod‐dependent mechanisms (i.e., 5‐HT synthesis or release) seem to be also implicated. On the other hand, this study shows that NA content in the Syrian hamster pineal gland does not exhibit daily variations, although marked nocturnal increases in the levels of DA and DOPAC were evident. These results suggest the existence of parallel daily alterations in pineal catecholamine synthesis and release, and suggest a role for DA in the pineal activation at night.
Electron probe X‐ray microanalysis of the elemental composition of the pineal gland of young adults and aged rats
Authors: Humbert Willy , Pévet Paul
Published: February 2007

Abstract: Fractures of deep‐frozen and freeze‐dried pineal glands were analysed for elemental composition by means of X‐ray microanalysis with a scanning electron microscope. The results from young adults (3 months old) were compared with those from aged animals (24 months old); significant increases in S, Ca, Al, Si, and Fe were observed in aged animals when compared to young adults. There were no significant differences with Na, Mg, CI, K, Ti, Cr, Mn, Ni, Cu, Zn, whereas a decrease of P was observed in aged animals when compared to young adults. Whether the changes observed in elemental composition have a direct effect on the activity and production of metalloenzymes and the overall physiology of the pineal gland are discussed.
An enzyme immunoassay for 6‐sulphatoxy‐melatonin in human urine
Authors: Peniston‐Bird John F. , Di Wei‐Li , Street Catherine A. , Edwards Ray , Little John A. , Silman Robert E.
Published: February 2007

Abstract: We describe a newly developed enzyme immunoassay (EIA) for the determination of 6‐sulphatoxy‐melatonin (aMT6s) in human urine, using a aMT6s‐bovine serum albumin‐horseradish peroxidase (aMT6s‐BSA‐HRP) conjugate as the enzyme label. The assay incorporates a highly specific antibody raised in rabbits. The EIA has a sensitivity of 2 pg/well (40 pg/ml) with intraassay coefficients of variation of 2.3–6.1% in the range of the assay. The material with the highest level of cross‐reactivity was N‐acetyl serotonin sulphate, with a relative potency of 0.000078%. One hundred thirty‐four urine samples from children and adults at different time points were assayed and the results compared with those from an established radioimmunoassay (RIA) and with a newly developed RIA using the same antibody as the EIA. The correlation coefficient, r, comparing the two RIA's was 0.9869, and the regression equation was log (kit) = 0.9340 log (new) + 0.1213. The correlation coefficient, r, comparing the EIA with the newly developed RIA, was 0.9686, and regression equation log (new) = 0.9674 log (EIA) + 0.0600. The EIA for the measurement of aMT6s in urine represents a new approach in the investigation of pineal function.
Melatonin as a therapeutic agent in experimental endotoxic shock
Authors: Maestroni Georges J. M.
Published: February 2007

Abstract: We demonstrated that the pineal neurohormone melatonin exerts immunoregulatory effects via T‐helper 2 (Th2) cell products. Th2 products may modulate the secretion and/or action of inflammatory cytokines, which play an important role in the development of septic shock associated with endotoxemia. Here we report that a single melatonin injection protects mice treated with a lethal dose of lipolysaccharide (LPS) especially when melatonin was injected 3 to 6 hr after LPS. This effect did not apparently involve Th cells or inhibition of inflammatory cytokines or macrophage nitric oxide (NO) generation. Nevertheless, plasma nitrate concentration, which reflects the rate of NO synthesis, showed a significant reduction at 18 and 24 hr after LPS administration. Melatonin is being studied in humans for cancer immunotherapy. The data presented here identify melatonin as potential therapy for septic shock.
Nocturnal secretory patterns of melatonin, luteinizing hormone, prolactin and Cortisol in male patients with gonadotropin‐releasing hormone deficiency
Authors: Luboshitzky Rafael , Lavi Schahar , Thuma Isam , Herer Paula , Lavie Peretz
Published: February 2007

Abstract: To clarify whether disorders of gonadotropin releasing hormone (GnRH) deficiency are associated with altered melatonin and pituitary hormones secretory patterns, we studied male patients with hypogonadotropic hypogonadism (IGD; n = 6), delayed puberty (DP; n = 7) and age‐matched pubertal controls (n = 7). Serum samples for the determination of melatonin, luteinizing hormone (LH), prolactin and Cortisol levels were obtained at 15 min intervals from 1900 to 0700 in a controlled light‐dark environment, complete bed‐rest and fasting with simultaneous sleep recordings. Mean (± SD) dark‐time melatonin levels were significantly higher in IGD (286 ± 26 pmol/L) and DP (205 ± 44 pmol/L) compared with 178 + 64 pmol/L in controls (P < 0.003). So were the mean (± SD) peak melatonin levels (453 ± 63, 346 ± 106 and 292 ± 96 pmol/L) in IGD, DP and controls, respectively (P < 0.03). Integrated nocturnal melatonin (AUC) values were also higher in IGD and DP (184 ± 15 and 134 ± 28 pmol/min/L × 103) compared with 116 ± 42 pmol/min/L × 103 in controls (P < 0.003). The time of onset of the nocturnal melatonin rise was observed earlier in IGD and DP patients as compared to controls. No correlations were found between melatonin and LH levels, between melatonin and prolactin levels, or between melatonin and Cortisol levels. These data indicate that melatonin secretion is enhanced in male patients with GnRH deficiency. The lack of correlation between melatonin and LH suggest that circulating gonadal steroids, rather than LH, modulate melatonin secretion in a reverse fashion.