Higher Melatonin Concentrations Research Articles

Epinephrine Preworkout Elevation May Offset Early Morning Melatonin Concentrations to Maintain Maximal Muscular Force and Power in Track Athletes

The optimal time of day for training has become an important question for many strength and conditioning specialists, and this study was designed to add some insights into this complex question. The primary purpose of this investigation was to examine physical performance within the temporal context of the relationship between physical performance, epinephrine, and melatonin concentrations in the early morning (0530 hours) and late (1500 hours) afternoon in elite collegiate male track and field athletes (jumpers and sprinters). Subjects had a mean (±SD) age, height, and body mass of 20.4 (±1.6) years, 185.8 (±9.4) cm, and 77.9 (±8.5) kg, respectively. Blood was obtained before each AM and PM testing session. Mean plasma melatonin concentrations were 34.9 ± 22.7 pg·ml and 4.8 ± 3.3 pg·ml for the AM vs. PM trials, respectively, demonstrating a significant (p ≤ 0.05) difference between time points. Mean resting plasma epinephrine concentrations for AM (171.7 ± 33.7 pmol·L) and PM (127.6 ± 47.8 pmol·L) also differed significantly between trails at the different times. In addition, significant differences were observed with respect to foot quickness in the AM (5.14 ± 1.06 seconds) and PM (4.39 ± 0.76 seconds). Mean peak power output for vertical jump power was 5,407.1 ± 1,272.9 W, 5,384.6 ± 888.3 W for AM vs. PM trials, respectively, which were not significantly different. The results of this investigation indicate that time of day did not negatively impact whole body physical performance in trained track athletes but did impact the quality of quickness. Thus in the morning, whole body power performances may be enhanced through adrenergic arousal when melatonin is elevated. However, this was not the case for movements requiring quickness and accuracy of movement. To compensate for the "sleepiness" associated with high concentrations of melatonin, being secreted from the pineal gland representing a continued "sleepiness" effect on the body, early morning practices may require greater adrenergic arousal to potentially offset melatonin's effects. The results of this study raise important questions on the use of early morning practices for more complex tasks that require high reaction speeds, even under conditions of adrenergic arousal.

Melatonin in the Biliary Tract and Liver: Health Implications

Melatonin is a widely-produced and ubiquitously-distributed molecule with multiple critical functions in all organs and organisms. These functions are mediated by both receptor-mediated and receptor-independent actions of the indole. This survey reviews the reports documenting the presence and function of melatonin in the hepatobiliary system. The published data document the exceptionally high concentrations of melatonin in the bile; herein, we speculate on the significance of these high melatonin levels to the function of the biliary tree. Moreover, we suggest that the elevated concentrations of melatonin in the bile fluid may be a consequence of its recirculation in what is referred to as the enterohepatic circulation. The article also examines the published reports related to melatonin levels in hepatocytes, which appear to be independent of pineal-derived melatonin. In both the biliary system and liver, melatonin provides protection against free radicals in cells of these organs. This is particularly important in these organs since they are under constant assault by highly toxic agents/processes that could compromise their critical physiology. As in other tissues, melatonin provides hepatocytes and cholangiocytes with a buffer against free radicals that are persistently produced and thereby this indole protects against oxidative molecular damage and metabolic dysfunction. Melatonin achieves this protection via the diverse free radical scavenging mechanisms of it and its metabolites (known as the antioxidant cascade), due to its ability to reduce electron leakage from the respiratory complexes in the inner mitochondrial membrane (radical avoidance) and as a result of the stimulation of antioxidative enzymes.

Suppression of fertility in adult cats.

Cats are animals with highly efficient reproduction, clearly pointing to a need for suppression of fertility. Although surgical contraception is highly effective, it is not always the method of choice. This is predominantly because it is cost-intensive, time-consuming and irreversible, with the latter being of major importance for cat breeders. This article reviews the use of progestins, scleroting agents, immunocontraception, melatonin, GnRH antagonists and finally, GnRH agonists, in adult male and female cats in detail, according to the present state of the art. By now, various scientific and clinical options are available for the suppression of fertility in adult cats and the decision as to which should be chosen - independent of the legal registration of any state - depends on different facts: (i) feral or privately owned animal? (ii) temporary or permanent suppression of fertility wanted/needed? (iii) sex of the animal? New effective and available methods for hormonal contraception include melatonin implants for short-term post ponement of oestrus in adult queens and slow-release GnRH-agonist implants containing deslorelin (Suprelorin(®) ) for short- and long-term contraception in male and female companion and breeding cats.

Profiling the melatonin content in organs of the pepper plant during different growth stages

Melatonin (N-acetyl-5-methoxytryptamine), a well-known animal hormone, was first isolated from bovine pineal gland and, since then, it was discovered in evolutionary distant organisms including bacteria, algae, invertebrates, and finally in higher plants. Although the presence of melatonin in plants seems to be a universal phenomenon, there is still an absence of information on its occurrence in important plant species, one of which is pepper (Capsicum annuum L.). Our objective was to determine the presence of melatonin in different organs (leaves, roots, fruits and seeds) of two pepper cultivars and its variation during various growth stages (germination, seedling, flowering, and harvest) using HPLC–FD. We found very high concentration of melatonin in seedlings at the cotyledon stage (108.6–111.6ngg−1FW) with a progressive decline as the plants matured. Melatonin was also found to accumulate highly in mature seeds, and to varying concentrations in fruits, leaves, and roots depending on the developmental stage, strongly suggesting that melatonin controls these developmental processes.

Melatonin treatment increases the transcription of cell proliferation-related genes prior to inducing cell death in C6 glioma cells in vitro

A number of studies have suggested that melatonin possesses anticancer properties. However, conflicting data exists with regard to the role of melatonin in the treatment of cancer. In the present study, the effects of melatonin on the transcriptional regulation of three genes associated with cell proliferation (Nestin, Bmi-1 and Sox2), and on C6 glioma cell survival and viability, were investigated in vitro to evaluate the use of melatonin in cancer therapy. Melatonin was shown to increase the mRNA levels of Nestin, Bmi-1 and Sox2 in a similar pattern, with the highest mRNA levels noted at a concentration of 3 mM. At higher concentrations of melatonin (5 mM), the mRNA levels of Nestin, Bmi-1 and Sox2 were reduced from their peak levels, and were correlated with changes observed in immunofluorescence morphology studies, cell viability and survival assays. Immunofluorescence studies of Nestin-stained cells demonstrated that treatment with a higher concentration of melatonin (3 and 5 mM) led to the Nestin filaments condensing and rearranging around the cell nuclei, and an alteration in the cell morphology. C6 cell viability was also significantly decreased at 3 mM melatonin, and cell death was observed at 5 and 10 mM melatonin. These results suggested that Nestin, Bmi-1 and Sox2 were strongly correlated with the survival of C6 cells following treatment with melatonin, and that high therapeutic concentrations of melatonin (>5 mM) were required to induce cell death. These findings suggested that the implementation of melatonin in the treatment of glioma and other types of cancer may be inhibited by conflicting cell growth signals in cells. Therefore, adjunct therapy is required to improve the efficacy of melatonin in the treatment of cancer.

Supplementation with low concentrations of melatonin improves nuclear maturation of human oocytes in vitro

Studies in bovine and porcine have indicated that melatonin (MT) could induce meiotic maturation of immature oocytes in vitro. The object of the current study was to investigate if MT could ameliorate human oocytes maturation during rescue in vitro maturation (IVM). Two hundred seventy eight germinal vesicle (GV) oocytes and 451 (MI) metaphase I oocytes were vitrified, thawed and then matured in vitro. All the oocytes were randomly allocated into six groups in which the oocytes were cultured in medium supplemented with different concentrations of MT (0, 10(-2), 1, 10(2), 10(4), 10(6)nM) and nuclear maturation was evaluated at 6h, 12h, 18h, 24h and 48h of culture. The optimal MT concentration for both GV and MI oocytes was 1nM. At 24h of culture, nuclear maturation rate of MI oocytes cultured in 1nM MT medium was significantly higher than other groups (P < 0.05); Nuclear maturation rate of GV oocytes cultured in 1nM MT medium was also significantly higher than the control group (P < 0.05). On the other hand, decreased nuclear maturation rate was observed in the high MT concentration group (10(6)nM). The current study demonstrated that low concentration of exogenous MT could ameliorate nuclear maturation of human oocyte during rescue IVM, while high concentration of MT presented negative effects.

Melatonin inhibits the expression of vascular endothelial growth factor in pancreatic cancer cells.

To investigate the effects of melatonin on cellular proliferation and endogenous vascular endothelial growth factor (VEGF) expression in pancreatic carcinoma cells (PANC-1). PANC-1 cells were cultured for this study. The secreted VEGF concentration in the culture medium was determined using ELISA method, VEGF production in the tumor cells was detected by immunocytochemistry, and VEGF mRNA expression was determined by RT-PCR. Higher melatonin concentrations significantly inhibited cellular proliferation, with 1 mmol/L concentration exhibiting the highest inhibitory effect (P<0.01). VEGF concentrations in the cell culture supernatants and intra-cellules were all significantly reduced after melatonin (1 mmol/L) incubation (P<0.05). VEGF mRNA expression decreased markedly in a time-dependent manner during the observation period (P<0.05). High melatonin concentrations markedly inhibited the proliferation of pancreatic carcinoma cells. The endogenous VEGF expression was also suppressed by melatonin incubation.

The Effects of Melatonin on the Physical Properties of Bones and Egg Shells in the Laying Hen

Laying hens often experience unbalanced calcium utilization which can cause deficiencies in bone and egg mineralization. Because melatonin has been shown to affect bone mineralization in other animals, we examined whether treating hens with melatonin would affect eggshell thickness and improve skeletal performance, thereby reducing skeletal and egg shell defects. Birds were given a diet containing either low (30 µg/kg), medium (300 µg/kg), or high (3 mg/kg) concentrations of melatonin, or control feed through approximately one laying cycle. We examined the weight, length, and strength of egg, femur, tibia, and keel. Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls. Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin. Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin. Our data suggest that melatonin may affect the allocation of calcium to bone at the expense of egg shell mineralization.

Clinical significance of melatonin concentrations in predicting the severity of acute pancreatitis

To assess the value of plasma melatonin in predicting acute pancreatitis when combined with the acute physiology and chronic health evaluation II (APACHEII) and bedside index for severity in acute pancreatitis (BISAP) scoring systems. APACHEII and BISAP scores were calculated for 55 patients with acute physiology (AP) in the first 24 h of admission to the hospital. Additionally, morning (6:00 AM) serum melatonin concentrations were measured on the first day after admission. According to the diagnosis and treatment guidelines for acute pancreatitis in China, 42 patients suffered mild AP (MAP). The other 13 patients developed severe AP (SAP). A total of 45 healthy volunteers were used in this study as controls. The ability of melatonin and the APACHEII and BISAP scoring systems to predict SAP was evaluated using a receiver operating characteristic (ROC) curve. The optimal melatonin cutoff concentration for SAP patients, based on the ROC curve, was used to classify the patients into either a high concentration group (34 cases) or a low concentration group (21 cases). Differences in the incidence of high scores, according to the APACHEII and BISAP scoring systems, were compared between the two groups. The MAP patients had increased melatonin levels compared to the SAP (38.34 ng/L vs 26.77 ng/L) (P = 0.021) and control patients (38.34 ng/L vs 30.73 ng/L) (P = 0.003). There was no significant difference inmelatoninconcentrations between the SAP group and the control group. The accuracy of determining SAP based on the melatonin level, the APACHEII score and the BISAP score was 0.758, 0.872, and 0.906, respectively, according to the ROC curve. A melatonin concentration ≤ 28.74 ng/L was associated with an increased risk of developing SAP. The incidence of high scores (≥ 3) using the BISAP system was significantly higher in patients with low melatonin concentration (≤ 28.74 ng/L) compared to patients with high melatonin concentration (> 28.74 ng/L) (42.9% vs 14.7%, P = 0.02). The incidence of high APACHEII scores (≥ 10) between the two groups was not significantly different. The melatonin concentration is closely related to the severity of AP and the BISAP score. Therefore, we can evaluate the severity of disease by measuring the levels of serum melatonin.

Seasonal Reproductive Activity of Domestic Queens (Felis catus) in the Tropics of Mexico

The objective of this study was to determine the seasonal ovarian activity of domestic queens under the tropical conditions of southern Mexico (19° 30' and 21° 35' N latitude). A total of 250 reproductive tracts were evaluated, and the frequencies of queens with ovarian activity (oestrus, dioestrus or pregnant), anoestrus, pregnancies and ovulation rate by season of the year (spring, summer, autumn and winter) were calculated. Ovarian activity was observed throughout the year, but a significant reduction occurred during the winter; conversely, anoestrous cases were lower during spring and showed an increase during summer, autumn and winter. Pregnancies were most common during spring and decreased during summer, autumn and winter. Ovulation rate varied from 2.5 to 2.8 during the four seasons. Cystic endometrial hyperplasia, pyometra and ovarian follicular cysts were the most common lesions found. The results demonstrate that domestic queens are not seasonal in tropical conditions, but a clear effect of the season of the year reducing ovarian activity is present.

Melatonin enhances root regeneration, photosynthetic pigments, biomass, total carbohydrates and proline content in the cherry rootstock PHL-C (Prunus avium × Prunus cerasus)

The present study, investigates the effects of melatonin (0, 0.05, 0.1, 0.5, 1, 5 and 10 μM) on the morphogenic and biochemical responses in the cherry rootstock PHL-C (Prunus avium L. × Prunus cerasus L.), from shoot tip explants. The incorporation of melatonin (0-10 μM) in the Murashige and Skoog (MS) medium, greatly influenced rooting either positively or negatively. Melatonin, irrespective of its concentration, had a negative effect concerning the number of roots. However, application of 0.5 μM melatonin significantly increased the root length; while 1 μM melatonin increased the root length by 2.5 times, and the fresh weight of the roots by 4 times, in comparison to the control. Although 0.05 μM melatonin increased rooting by 11.11%, 5 μM melatonin had a significant reduction on the number, the fresh weight of roots, and the rooting percentage. Melatonin concentration of 0.1 μM resulted in the greatest chlorophyll (a + b) content, and 5-10 μM reduced the chlorophyll concentration by 2 times, compared to the control. The high melatonin concentrations (5 and 10 μM), increased the levels of proline and carbohydrates in leaves by 3-4 times. In the roots, 0.5 μM of melatonin concentration increased the carbohydrate levels by 1.5 times, while 0.05, 0.1 and 1 μM melatonin concentration significantly reduced the proline content.

Does supplementation of in-vitro culture medium with melatonin improve IVF outcome in PCOS?

Human pre-ovulatory follicular fluid (FF) contains a higher concentration of melatonin than serum. The aim of this study was to evaluate the effect of melatonin supplementation of culture medium on the clinical outcomes of an in-vitro maturation (IVM) IVF-embryo transfer programme for patients with polycystic ovarian syndrome (PCOS). Melatonin concentrations in the culture media of granulosa cells (GC) or cumulus-oocyte-complexes (COC) were measured and the clinical outcomes after using IVM media with or without melatonin were analysed. In the culture media of GC or COC, melatonin concentrations gradually increased. When human chorionic gonadotrophin priming protocols were used, implantation rates in the melatonin-supplemented group were higher than those of the non-supplemented control group (P<0.05). Pregnancy rates were also higher, although not significantly. The findings suggest that the addition of melatonin to IVM media may improve the cytoplasmic maturation of human immature oocytes and subsequent clinical outcomes. It is speculated that follicular melatonin may be released from luteinizing GC during late folliculogenesis and that melatonin supplementation may be used to improve the clinical outcomes of IVM IVF-embryo transfer.Melatonin is primarily produced by the pineal gland and regulates a variety of important central and peripheral actions related to circadian rhythms and reproduction. Interestingly, human pre-ovulatory follicular fluid contains a higher concentration of melatonin than serum. However, in contrast to animal studies, the direct role of melatonin on oocyte maturation in the human system has not yet been investigated. So, the aim of the study was to evaluate the effect of melatonin supplementation of culture medium on the clinical outcome of an in-vitro maturation (IVM) IVF-embryo transfer programme for PCOS patients. The melatonin concentrations in culture medium of granulosa cells (GC) or cumulus-oocyte-complexes (COC) were measured and the clinical outcomes of IVM IVF-embryo transfer using IVM medium alone or supplemented with melatonin were analysed. In the culture media of GC or COC, the melatonin concentration gradually increased. With human chorionic gonadotrophin priming, the pregnancy and implantation rates in the melatonin-supplemented group were higher than those of the non-supplemented control (P<0.05). Our findings suggest that follicular melatonin is released from luteinizing GC during late folliculogenesis and plays a positive role in oocyte maturation. Therefore, addition of melatonin into IVM medium may improve cytoplasmic maturation of human immature oocytes and subsequent clinical outcomes.

345 Analysis of Antioxidative Status of Human Milk and its Variations at Day and Night Time

IntroductionHuman milk (HM) contains antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase. Melatonin (MT) shows antioxidative properties both directly by stimulating the activities of antioxidant enzymes...

High levels of melatonin generated during the brewing process

Beer is a beverage consumed worldwide. It is produced from cereals (barley or wheat) and contains a wide array of bioactive phytochemicals and nutraceutical compounds. Specifically, high melatonin concentrations have been found in beer. Beers with high alcohol content are those that present the greatest concentrations of melatonin and vice versa. In this study, gel filtration chromatography and ELISA were combined for melatonin determination. We brewed beer to determine, for the first time, the beer production steps in which melatonin appears. We conclude that the barley, which is malted and ground in the early process, and the yeast, during the second fermentation, are the largest contributors to the enrichment of the beer with melatonin.

Differential expression of rhodopsin and Exo-rhodopsin genes in the retina and pineal gland of olive flounder (Paralichthys olivaceus)

To explore the part of molecular mechanism of rhodopsin family genes in the olive flounder (Paralichths olivaceus), we observed the change patterns of the photoreceptors, rhodopsin (RH) and extra-ocular rhodopsin (Exo-RH) genes. We isolated cDNAs of RH and Exo-RH genes from the retina and pineal gland, respectively, of the olive flounder and investigated the differential expression of these genes in these organs during a 28-h time period under the 12-h light:12-h dark (LD) photocycle, constant dark (DD) and constant light (LL). The expression of RH gene in retina showed clear circadian pattern under LD, with the highest level at Zeitgeber time (ZT) 4 and ZT28 and lowest at ZT16. The expression level of Exo-RH gene in pineal organ under LD showed opposite pattern to that of RH, with higher expression during the dark period, and the peak was at ZT20. This expression pattern was similar between in vivo and in vitro (incubated) pineal organs. Under DD and LL conditions, the expression patterns of RH and Exo-RH genes were similar to those under LD photocycle, but the circadian change patterns were less clear. The expression levels of Exo-RH were about 100-fold (LD), 30,000-fold (DD) and 10-fold (LL) lower in pineal organ treated with high concentration of melatonin compared to the untreated pineal organ. The melatonin concentration in plasma had similar circadian pattern with that of the expression of Exo-RH gene, with the peak at ZT20 for fish kept under all LD, DD and LL conditions. Our results suggest that circadian rhythm in the olive flounder is controlled and maintained by the environmental photocycle through the mediation of RH and Exo-RH, and the melatonin concentration in blood plasma.

Melatonin Supplementation Decreases Prolactin Synthesis and Release in Rat Adenohypophysis: Correlation With Anterior Pituitary Redox State and Circadian Clock Mechanisms

In the laboratory rat, a number of physiological parameters display seasonal changes even under constant conditions of temperature, lighting, and food availability. Since there is evidence that prolactin (PRL) is, among the endocrine signals, a major mediator of seasonal adaptations, the authors aimed to examine whether melatonin administration in drinking water resembling in length the exposure to a winter photoperiod could affect accordingly the 24-h pattern of PRL synthesis and release and some of their anterior pituitary redox state and circadian clock modulatory mechanisms. Melatonin (3 µg/mL drinking water) or vehicle was given for 1 mo, and rats were euthanized at six time intervals during a 24-h cycle. High concentrations of melatonin (>2000 pg/mL) were detected in melatonin-treated rats from beginning of scotophase (at 21:00 h) to early photophase (at 09:00 h) as compared with a considerably narrower high-melatonin phase observed in controls. By cosinor analysis, melatonin-treated rats had significantly decreased MESOR (24-h time-series average) values of anterior pituitary PRL gene expression and circulating PRL, with acrophases (peak time) located in the middle of the scotophase, as in the control group. Melatonin treatment disrupted the 24-h pattern of anterior pituitary gene expression of nitric oxide synthase (NOS)-1 and -2, heme oxygenase-1 and -2, glutathione peroxidase, glutathione reductase, Cu/Zn- and Mn-superoxide dismutase, and catalase by shifting their acrophases to early/middle scotophase or amplifying the maxima. Only the inhibitory effect of melatonin on pituitary NOS-2 gene expression correlated temporally with inhibition of PRL production. Gene expression of metallothionein-1 and -3 showed maxima at early/middle photophase after melatonin treatment. The 24-h pattern of anterior pituitary lipid peroxidation did not vary after treatment. In vehicle-treated rats, Clock and Bmal1 expression peaked in the anterior pituitary at middle scotophase, whereas that of Per1 and Per2 and of Cry1 and Cry2 peaked at the middle and late photophase, respectively. Treatment with melatonin raised mean expression of anterior pituitary Per2, Cry1, and Cry2. In the case of Per1, decreased MESOR was observed, although the single significant difference found between the experimental groups when analyzed at individual time intervals was increase at early scotophase in the anterior pituitary of melatonin-treated rats. Melatonin significantly phase-delayed expression of Per1, Per2, and Cry1, also phase-delayed the plasma corticosterone circadian rhythm, and increased the amplitude of plasma corticosterone and thyrotropin rhythms. The results indicate that under prolonged duration of a daily melatonin signal, rat anterior pituitary PRL synthesis and release are depressed, together with significant changes in the redox and circadian mechanisms controlling them. (Author correspondence: danielcardinali@uca.edu.ar; danielcardinali@fibertel.com.ar)

Correlation between peripheral melatonin and general immune status of domestic goat, Capra hircus: A seasonal and sex dependent variation

Caprine immune system has largely been neglected by ruminant researchers despite of its high economic importance in bioindustry. We made an attempt to note the annual/seasonal and gender dependent variation in immune status of the domestic goat, Capra hircus, Jamunapari breed and correlated with the concentration of peripheral gonadal hormones (testosterone, 17β-estradiol) and melatonin. Based on the data of general immune parameters such as total leukocyte count (TLC) and percent lymphocyte count (%LC) along with blastogenic response of splenocytes in terms of percent stimulation ratio (%SR), we found an annual variation in immune status of male, female and castrated male goats in a gender dependent manner. Female goats showed higher immune parameters than that of castrated as well as intact male goats. Testosterone in intact male goats was high throughout the year, which might be responsible for low immune status. However, in castrated male goats, plasma testosterone was undetectable and presented an immune status equivalent to that of female goats. We observed a high immune status during the winter season in all the groups of goats, which might be due to high circulatory concentration and longer duration of melatonin induced by short days. Being released by circulating lymphocytes, the concentration of interleukin-2 (IL-2) in blood plasma, showed an annual and seasonal variation being higher in female than castrated and intact male goats throughout the year, having a similar trend in plasma melatonin concentration. The higher immune status in female goats during the winter months might have helped them to overcome the winter bound stress, i.e. low temperature. Therefore, we may propose that testosterone acts as an immunosupressor while melatonin as an immunostimulator for goats as it showed a positive correlation with immune parameters noted.

The role of melatonin as an antioxidant in the follicle

Melatonin (N-acetyl-5-methoxytryptamine) is secreted during the dark hours at night by pineal gland, and it regulates a variety of important central and peripheral actions related to circadian rhythms and reproduction. It has been believed that melatonin regulates ovarian function by the regulation of gonadotropin release in the hypothalamus-pituitary gland axis via its specific receptors. In addition to the receptor mediated action, the discovery of melatonin as a direct free radical scavenger has greatly broadened the understanding of melatonin's mechanisms which benefit reproductive physiology. Higher concentrations of melatonin have been found in human preovulatory follicular fluid compared to serum, and there is growing evidence of the direct effects of melatonin on ovarian function especially oocyte maturation and embryo development. Many scientists have focused on the direct role of melatonin on oocyte maturation and embryo development as an anti-oxidant to reduce oxidative stress induced by reactive oxygen species, which are produced during ovulation process. The beneficial effects of melatonin administration on oocyte maturation and embryo development have been confirmed by in vitro and in vivo experiments in animals. This review also discusses the first application of melatonin to the clinical treatment of infertile women and confirms that melatonin administration reduces intrafollicular oxidative damage and increase fertilization rates. This review summarizes our recent works and new findings related to the reported beneficial effects of melatonin on reproductive physiology in its role as a reducer of oxidative stress, especially on oocyte maturation and embryo development.

Functional roles of melatonin in plants, and perspectives in nutritional and agricultural science

The presence of melatonin in plants is universal. Evidence has confirmed that a major portion of the melatonin is synthesized by plants themselves even though a homologue of the classic arylalkylamine N-acetyltransferase (AANAT) has not been identified as yet in plants. Thus, the serotonin N-acetylating enzyme in plants may differ greatly from the animal AANAT with regard to sequence and structure. This would imply multiple evolutionary origins of enzymes with these catalytic properties. A primary function of melatonin in plants is to serve as the first line of defence against internal and environmental oxidative stressors. The much higher melatonin levels in plants compared with those found in animals are thought to be a compensatory response by plants which lack means of mobility, unlike animals, as a means of coping with harsh environments. Importantly, remarkably high melatonin concentrations have been measured in popular beverages (coffee, tea, wine, and beer) and crops (corn, rice, wheat, barley, and oats). Billions of people worldwide consume these products daily. The beneficial effects of melatonin on human health derived from the consumption of these products must be considered. Evidence also indicates that melatonin has an ability to increase the production of crops. The mechanisms may involve the roles of melatonin in preservation of chlorophyll, promotion of photosynthesis, and stimulation of root development. Transgenic plants with enhanced melatonin content could probably lead to breakthroughs to increase crop production in agriculture and to improve the general health of humans.

Enantioselective micro‐2D‐HPLC determination of aspartic acid in the pineal glands of rodents with various melatonin contents

Enantioselective determination of aspartic acid (Asp) in the pineal gland of rodents with various melatonin contents was performed using a highly sensitive and selective two-dimensional HPLC system. After derivatization of the amino group with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), NBD-Asp was separated using a capillary monolithic ODS column in the first dimension. The fraction of NBD-Asp was automatically collected and transferred to the second dimension, and the D- and L-Asp were separated and determined using a narrowbore enantioselective column. Large amounts of D-Asp were observed in the pineal gland of the rats and specific strains of mice (C3H and CBA) possessing a high concentration of melatonin in their pineal gland. On the other hand, the amounts of D-Asp were small in the pineal gland of mice possessing a trace or no melatonin in their pineal gland (ddY, ICR, C57BL and BALB/c). In other tissues and physiological fluids, no significant strain-dependent changes of the D-Asp amounts were observed. These results indicate that large amounts of D-Asp are present only in the pineal gland containing large amounts of melatonin, and special care should be taken when selecting mouse strains for the investigation of D-Asp.