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Comparative Study 2010; 31(3): 330-335 PubMed PMID: 20588229 Citation  Keywords:  Adolescent, Adult, Circadian Rhythm:physiology, Energy Transfer, Humans, Melatonin:blood, Photic Stimulation:instrumentation, Phototherapy:instrumentation,.   

OBJECTIVE: Practicability remains a problem in light therapy of biological rhythm disorders. We report here the effect on melatonin secretion of a device consisting of a prototype of eyeglasses including light emitting diodes (LED) in lenses (Somnavue).

METHODS: Light (1,200 lx) was administered in a randomised crossover design to ten healthy subjects with Somnavue for 1 or 2 hours, Lumino (a helmet which administers light) for 1 hour, and placebo, beginning at 01:00 h. Plasma melatonin concentrations were evaluated between 20:00-05:00 h.

RESULTS: Multiple comparisons showed differences between placebo and Somnavue administered for one or two hours (p<0.01 and p<0.05 respectively) and Lumino and placebo (p<0.05).

CONCLUSIONS: In conclusion, Somnavue was able to suppress melatonin. The development of such a device could increase adherence with light treatment in SAD or circadian rhythm sleep disorders....

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Journal Article 2007; 28(4): 489-495 PubMed PMID: 17693961 Citation  Keywords:  Animals, Cell Count, Circadian Rhythm:physiology, Corticosterone:blood, Immune System:physiology, Macrophages:pathology, Male, Melatonin:blood, Microspheres, Peritoneal Cavity:cytology, Phagocytosis:physiology, Physical Conditioning, Animal:physiology, Ra.   

: Corticosterone is thought to be the main glucocorticoid secreted in response to stressful exercise, while melatonin buffers the adverse immunological effects of stress. The present work was aimed to evaluate whether swimming-exercise-induced stress leads to changes in the chronobiology parameters of the circadian rhythms of melatonin and corticosterone, and in the number and phagocytosis of peritoneal macrophages in 3-month-old male Wistar rats. The animals were subjected to a physical activity trial consisting of 2 h of free swimming. Radioimmunoassay was used to determine the plasma levels of melatonin and corticosterone. Phagocytosis was measured by the latex-bead phagocytosis index (PI), i.e., the number of latex beads ingested by 100 macrophages, the phagocytosis percentage (PP), i.e., the percentage of cells that had phagocytosed at least one latex bead, and the phagocytosis efficiency (PE), i.e., the ratio PI: PP which indicates how effectively the phagocytes ingested the particles. Stress significantly decreased the MESOR and amplitude of the melatonin rhythm, and significantly increased the MESOR of the corticosterone rhythm. The control animals' peritoneal macrophage number and PI showed a circadian rhythm with maxima at 02:00 and 03:00, respectively. The stressed group displayed higher values of PI than the controls at most hours of the night, but the number of cells in the peritoneal cavity was practically the same at all hours studied. These data confirm that melatonin and corticosterone act as modulators of the innate immune response, and that the circadian rhythm of the two hormones are altered in situations of stress....

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Comparative Study 2007; 28(2): 159-165 PubMed PMID: 17435669 Citation  Keywords:  Animals, Circadian Rhythm, Corticosterone:blood, Diabetes Mellitus, Experimental:metabolism, Gastrointestinal Tract:metabolism, Kidney:metabolism, Male, Melatonin:blood, Pancreas:metabolism, Pineal Gland:metabolism, Rats, Rats, Wistar, Spleen:metabolism, .   

OBJECTIVE: Exogenous melatonin was found to protect target organs under conditions of diabetes mellitus, however, concentrations of the hormone in peripheral tissues have not been determined. Therefore the aim of the present study was to measure the daily profile of melatonin levels in the pineal gland, plasma, pancreas, kidney, spleen, duodenum and colon of control and diabetic rats.

MATERIAL & METHODS: Diabetes was induced by a single injection of streptozotocin (STZ, 65 mg/kg of body weight) and samples were collected over a 24 hr cycle on day 17 after STZ treatment. Melatonin and corticosterone levels were measured directly in plasma and after extraction in the pineal gland and peripheral organs (pancreas, kidney, spleen, duodenum and colon).

RESULTS: A significant daily rhythm of melatonin concentrations was found not only in the pineal gland and plasma but also in the pancreas, kidney, spleen and duodenum. The daily pattern of melatonin levels in the colon was arrhythmic without a characteristic night-time increase of hormone concentration. Experimentally induced diabetes resulted in lower melatonin levels in the pancreas, kidney and duodenum as compared to control. No differences between STZ-treated and control rats were found in the spleen and colon. Plasma corticosterone levels were enhanced in diabetic rats in comparison with controls and the daily profile was not rhythmic.

CONCLUSION: Our data suggest that the lower amplitude of melatonin rhythm in target organs induced by experimental diabetes can contribute to desynchronization of daily rhythms and can lower the antioxidative capacity of tissues....

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Clinical Trial 2006; 27(5): 659-664 PubMed PMID: 17159819 Citation  Keywords:  Estradiol:administration & dosage, Female, Follicle Stimulating Hormone:blood, Humans, Hydrocortisone:blood, Luteinizing Hormone:blood, Melatonin:blood, Middle Aged, Postmenopause:blood, Time Factors,.   

OBJECTIVES: It has been well-documented that serum melatonin levels are insensitive to estrous or menstrual ovarian steroid variations in the female rat or the human. However, a negative coupling has been already demonstrated between the nocturnal serum melatonin peak and serum E2 concentration during the late premenopausal period in the woman. The objection of the present study was designed to determine if diurnal serum melatonin values can be also lowered by a single administration of estrogen.

METHODS: We performed a detailed analysis of variations of serum estradiol, LH, FSH, melatonin and cortisol after one single I.M. injection of 2 mg of a conjugated estrogen, delestrogen (estradiol valerate) in 0.1 ml of oil. A 15 ml blood collection was done at 8:00 a.m. before the injection, and at 8:30 a.m., 9:00 a.m., 10:00 a.m., 12:00 noon, and 4:00 p.m. 17beta-estradiol, LH and FSH were determined by microparticle enzyme immunoassays kits. Melatonin determination was made using a RIA kit and cortisol was assayed by a RIA method.

RESULTS: A significant rise in serum 17beta-estradiol was already seen by one hour after the injection of estradiol valerate. Then, an almost linear increase was observed up to at last eight hours after the injection of estradiol valerate. A significant decrease in serum LH was not seen before four hours after the injection of estradiol valerate. Overall, there was a trend toward a decline in serum melatonin and cortisol concentration. The decreasing trend of cortisol serum level was tested as significant over time (p< 0.001). However, the decrease in serum concentration did not reach a significant level for melatonin.

CONCLUSION: Overall, these results show that after menopause an acute administration of estrogen during the early diurnal period of the day leads to a significant rapid decrease in cortisol serum values, but to only a partial non significant decrease in melatonin serum values....

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Controlled Clinical Trial 2005; 26(6): 653-656 PubMed PMID: 16380697 Citation  Keywords:  Adult, Circadian Rhythm:physiology, Down-Regulation, Female, Humans, Kidney Failure, Chronic:blood, Male, Melatonin:blood, Middle Aged, Reference Values, Renal Dialysis, Reproducibility of Results,.   

OBJECTIVES: In spite of broad interest, intensive studies on function of melatonin have not yielded much information about relationships between this hormone and kidneys in health, and particularity, in disease. There are only a few studies dealing with melatonin concentrations in renal diseases, mainly performed in hemodialyzed patients with end-stage renal disease (ESRD). Moreover, the most melatonin assays were performed during the daytime, and the results are conflicting. Therefore, the aim of the present study was to determine the circadian melatonin profiles in patients ESRD before and after hemodialysis.

MATERIAL AND METHODS: Thirty patients (19 males and 11 females) with ESRD undergoing dialysis, aged 22 to 64 years (mean+/-SEM: 49.1.0+/-1.9 years) were included in the study. The control group consisted of 20 healthy volunteers (13 males and 7 females) aged 35 to 55 years (mean+/-SEM: 46.2+/-1.4 years) matched according to sex and age. Blood samples were collected on the day preceding hemodialysis and one day following dialysis at 08:00, 12:00, 16:00, 20:00, 24:00, 02:00, 04:00, and 08:00 h. Melatonin concentration was measured by enzyme immunoassay.

RESULTS: In patients with renal insufficiency undergoing dialysis mean melatonin nocturnal concentrations were significantly lower then those in healthy volunteers. The presence of the circadian rhythm in melatonin concentrations (although of significantly lower nocturnal amplitude) was detected only in 8 patients with renal failure undergoing hemodialysis, whereas in remaining 22 patients no such rhythm was found. Hemodialysis did not influence melatonin concentrations.

CONCLUSIONS: The mechanism of depressed melatonin concentrations in hemodialyzed patients observed in our study remains unclear. However, it seems possible that decline in melatonin levels is due to impairment in adrenergic function that occurs in renal failure. Because the studies on the melatonin secretion in chronic renal failure bring about conflicting results, the relationship between renal diseases and melatonin secretion needs further investigations....

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Clinical Trial 2005; 26(5): 493-498 PubMed PMID: 16264413 Citation  Keywords:  Adult, Circadian Rhythm:physiology, Humans, Light, Lighting, Male, Melatonin:blood, Middle Aged, Photic Stimulation, Pupil:physiology, Retina:physiology, Signal Transduction:physiology,.   

OBJECTIVES: Published data, both on nocturnal melatonin suppression in humans and on widely accepted retinal structure and function, suggest that spectral opponency plays a role in human circadian phototransduction. We directly test subadditivity, implied by spectral opponency, in human circadian phototransduction in response to nearly monochromatic and to polychromatic light.

METHODS: Adult male human subjects were exposed for 60 minutes to two intensities each of two lighting conditions, during nighttime experimental sessions. One condition consisted of light from mercury vapor lamps (450 and 1050 lx), and one condition consisted of light from these lamps filtered such that only the spectral line from this lamp at 436 nm was presented to subjects (7.5 and 15 lx).

RESULTS: Melatonin suppression from the filtered illumination at 436 nm alone was greater than mercury lamp illumination (containing energy at 436 nm in addition to other wavelengths), even when the sources exposed subjects' retinae to equal amounts of irradiance at 436 nm.

CONCLUSION: This direct test of subadditivity, together with evidence from neuroanatomy, supports the inference that spectral opponency is a fundamental characteristic of human circadian phototransduction....

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Journal Article 2005; 26(5): 575-580 PubMed PMID: 16264398 Citation  Keywords:  Acetylserotonin O-Methyltransferase:metabolism, Animals, Arylalkylamine N-Acetyltransferase:metabolism, Female, Melatonin:blood, Microscopy, Electron, Pineal Gland:metabolism, Pregnancy, Pregnancy, Animal:metabolism, Rabbits, Radioimmunoassay,.   

OBJECTIVES: The morphological and biochemical aspects of the pineal gland of pregnant and non-pregnant female vizcachas were investigated to examine whether there is a relationship between the pregnancy and this gland.

METHODS: Pregnant and non-pregnant adult female vizcachas were used. The ultrastructure of type I cell (dark and light pinealocytes) was studied. Pineal and serum melatonin were investigated by radioimmunoassay. Radiometric methods were applied to investigate the arylalkylamine-N-acetyltransferase (AA-NAT) and hydroxyindole-O-methyltransferase (HIOMT) activities.

RESULTS: The morphological study showed the existence of dark and light pinealocytes. The differences between both cells are slight. However, the appearance of dark pinealocytes suggests that they have a high activity. These cells were more abundant in the pineal gland of pregnant females. The pineal melatonin levels and the AA-NAT activity were higher in the pregnant females. Serum melatonin and HIOMT activity did not show significant differences.

CONCLUSION: Our results suggest that the morphological and biochemical changes in the pineal gland of pregnant vizcachas are associated with the gestation. However, the relation between the pineal gland and the pregnancy is complex and further studies are necessaries to clearly establish it....

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Journal Article 2004; 25(6): 411-414 PubMed PMID: 15665801 Citation  Keywords:  Adolescent, Adult, Circadian Rhythm:physiology, Female, Humans, Hyperprolactinemia:metabolism, Melatonin:blood, Middle Aged, Prolactin:blood,.   

OBJECTIVES: Relationship between melatonin and prolactin has been suggested on the basis of both experimental and clinical studies. However, there are scarce and controversial data concerning melatonin concentrations in hyperprolactinemic patients. Therefore, the aim of the present study was to evaluate the circadian rhythm of melatonin in female patients suffering from hyperprolactinemia.

MATERIAL AND METHODS: The study was performed on 28 women aged 17-58 years (mean+/-SEM: 30.5+/-1.8 years) suffering from idiopathic hyperprolactinemia and 14 healthy volunteers aged 20-50 years (mean+/-SEM: 36.4+/-3.0 years) with normal prolactin levels. Blood samples for measurements of serum melatonin and prolactin concentrations were collected at 08:00, 12:00, 16:00, 20:00, 24:00, 02:00, 04:00, 06:00, and 08:00 h. Melatonin and prolactin concentrations were measured by enzyme immunoassay.

RESULTS: Significant increase in melatonin serum concentrations was also observed in hyperprolactinemic patients in comparison with healthy volunteers during the night. Similar increase was also observed in the area under curve of melatonin concentrations. However, no correlation was found between prolactin and melatonin concentrations in any examined time points.

CONCLUSION: The results of the present study confirm suggestions of the presence of the relationship between melatonin and prolactin secretion....

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