The role of melatonin in immuno-enhancement: potential application in cancer.

Melatonin, a neurohormone produced mainly by the pineal gland, is a modulator of haemopoiesis and of immune cell production and function, both in vivo and in vitro. Physiologically, melatonin is associated with T-helper 1 (Th1) cytokines, and its administration favours Th1 priming. In both normal and leukaemic mice, melatonin administration results in quantitative and functional enhancement of natural killer (NK) cells, whose role is to mediate defenses against virus-infected and cancer cells.

Melatonin.

Melatonin, originally discovered as a hormone of the pineal gland, is produced by bacteria, protozoa, plants, fungi, invertebrates, and various extrapineal sites of vertebrates, including gut, skin, Harderian gland, and leukocytes. Biosynthetic pathways seem to be identical. Actions are pleiotropic, mediated by membrane and nuclear receptors, other binding sites or chemical interactions.

Melatonin and sleep in aging population.

The neurohormone melatonin is released from the pineal gland in close association with the light-dark cycle. There is a temporal relationship between the nocturnal rise in melatonin secretion and the 'opening of the sleep gate' at night. This association, as well as the sleep promoting effect of exogenous melatonin, implicates the pineal product in the physiological regulation of sleep.

Role of melatonin in neurodegenerative diseases.

The pineal product melatonin has remarkable antioxidant properties. It scavenges hydroxyl, carbonate and various organic radicals, peroxynitrite and other reactive nitrogen species. Melatonyl radicals formed by scavenging combine with and, thereby, detoxify superoxide anions in processes terminating the radical reaction chains.

Melatonin, a potent agent in antioxidative defense: actions as a natural food constituent, gastrointestinal factor, drug and prodrug.

Melatonin, originally discovered as a hormone of the pineal gland, is also produced in other organs and represents, additionally, a normal food constituent found in yeast and plant material, which can influence the level in the circulation. Compared to the pineal, the gastrointestinal tract contains several hundred times more melatonin, which can be released into the blood in response to food intake and stimuli by nutrients, especially tryptophan. Apart from its use as a commercial food additive, supraphysiological doses have been applied in medical trials and pure preparations are well tolerated by patients.

Does melatonin play a disease-promoting role in rheumatoid arthritis?

The pineal neurohormone melatonin (MLT) has been widely shown to exert an immunostimulatory and antiapoptotic role, mainly by acting on Th cells and on T and B cell precursors, respectively. Thus, MLT might favor or promote autoimmune diseases by acting directly on immature and mature immunocompetent cells. In fact, preclinical and clinical evidence point to a disease-promoting role of MLT in rheumatoid arthritis (RA).

REM sleep reduction, mood regulation and remission in untreated depression.

The contribution of increased rapid eye movement (REM) pressure through repeated, mild, reduction of (REM) sleep to remission from untreated depression was studied over a 5-month period in 20 depressed and 10 control volunteers. Sixty percent of the depressed subjects were in remission at the end of the study. Sixty-four percent of the variance in remission could be accounted for by four variables: the initial level of self-reported symptoms, the reported diurnal variability in mood, the degree of overnight reduction in depressed mood following interruptions of REM sleep and the quality of dream reports from these awakenings.

Senescence, sleep, and circadian rhythms.

The goal of this review article is to summarize our knowledge and understanding of the overlapping (interdisciplinary) areas of senescence, sleep, and circadian rhythms. Our overview comprehensively (and visually wherever possible), emphasizes the organizational, dynamic, and plastic nature of both sleep and circadian timing system (CTS) during senescent processes in animals and in humans. In this review, we focus on the studies that deal with sleep and circadian rhythms in aged animals and how these studies have closely correlated to and advanced our understanding of similar processes in ageing humans.

Interrelationships between nocturnal sleep, daytime alertness, and sleepiness: two types of alertness proposed.

The authors studied daytime sleepiness and alertness (based on the Multiple Sleep Latency Test [MSLT] and Maintenance of Wakefulness Test [MWT]) and nocturnal sleep in 22 patients with depression/anxiety and in 47 nondepressed patients with sleep apnea. The patients underwent two overnight sleep studies followed by daytime tests. In depressed patients, MWT scores correlated negatively with total sleep time and stage 3.

Diagnostic values of polysomnography in forensic medicine.

A man accused of a first-degree murder of a two-year-old girl claimed that he had not been conscious during the time of the alleged murder. The possibility that he may have committed the crime while "sleepwalking" was raised. The forensic psychiatrist looked to the sleep disorders facility to conduct polysomnographic investigation of the accused in order to investigate the possibility that he had a parasomnia.