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  • 1
    Electronic Resource
    Electronic Resource
    The pineal melatonin rhythm and its regulation by light in a subterranean rodent, the valley pocket gopher (Thomomys bottae) (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 16 (1994), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Reiter RJ, Reiter MN, Hattori A, Yaga K, Herbert DC, Barlow-Walden L. The pineal melatonin rhythm and its regulation by light in a subterranean rodent, the valley pocket gopher (Thomomys bottae). J. Pineal Res. 1994; 16: 145–153.〈section xml:id="abs1-1"〉〈title type="main"〉AbstractThe daytime and nighttime levels of pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity, and melatonin were measured in adult male and female valley pocket gophers, Thomomys bottae. This species was chosen for study because it is a subterranean rodent that inhabits burrows whose openings to the surface are closed. Therefore, under field conditions it is estimated that the pocket gopher spends roughly 99% of its time in absolute darkness in underground burrows. When wild captured pocket gophers were maintained under a light dark cycle (light intensity during the day of roughly 140 μ,W/cm2), nighttime levels of pineal NAT activity and melatonin content were higher than values measured during the day; on the other hand, HIOMT activity in the pineal gland was similar in the day and at night. When pocket gophers were exposed to an extended light period (220 μW/cm2) 4 hr into the night, the rise in melatonin synthesis normally associated with darkness onset was not inhibited. Also, when gophers were acutely exposed to a light intensity of 400 μW/cm2 for 1 hr beginning 4 hr after darkness onset, neither high nocturnal levels of pineal NAT nor pineal melatonin contents were reduced. Finally, when pocket gophers were exposed to a 600 (μW/cm2 light intensity at either 4 hr or 8 hr into the dark period, pineal melatonin synthesis remained elevated at a level comparable to that measured in dark-exposed controls. The results show that under controlled laboratory conditions the pineal gland of the valley pocket gopher, a species that in its natural habitat spends about 99% of its time in absolute darkness, exhibits higher melatonin synthesis during night than during the day. While the rhythm in pineal melatonin production in the pocket gopher is clearly synchronized by the prevailing light: dark cycle, high nighttime pineal melatonin synthesis is not readily inhibited by light in the intensity range of 220 to 600μW/cm2. In terms of its relative insensitivity to light at night, the pineal gland of the valley pocket gopher resembles that of other diurnally active rodents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1994.tb00094.x
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  • 2
    Electronic Resource
    Electronic Resource
    Twenty-four hour urinary excretion of 6-hydroxymelatonin sulfate in Down syndrome subjects (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 20 (1996), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Because of the overexpression of the enzyme superoxide dismutase, individuals with Down syndrome (DS) are believed to suffer from increased oxidative stress as a result of the excessive production of oxygen-based free radicals; their exposure to higher than normal free radical production may account in part for signs of premature aging, early onset of cataracts, and of Alzheimer's disease. Free radicals are normally neutralized by free radical scavengers and other antioxidants. The pineal hormone melatonin is a potent scavenger of both the hydroxyl and peroxyl radicals, both of which are highly toxic, and a stimulator of the antioxidative enzyme glutathione peroxidase. Considering this, we deemed it important to define the day/night rhythm and levels of melatonin production in DS subjects. To do this, we assessed the urinary excretion of the chief melatonin metabolite, 6-hydroxymelatonin sulfate, throughout a 24 hr period in DS subjects; comparisons were made with the metabolite levels in the urine of non-Down siblings and parents of the DS subjects. All 8 non-Down subjects exhibited what was classified as normal urinary excretion of 6-hydroxymelatonin sulfate with the usual low daytime and high night-time levels of the melatonin metabolite. Of 12 DS subjects studied, 10 exhibited the normal day/night rhythm in urinary 6-hydroxymelatonin sulfate levels; 2 subjects were devoid of a rhythm. However, when all the data from each group were averaged, there were no noticeable differences in the absolute levels or 24 hr variations in urinary 6-hydroxymelatonin sulfate excretion between DS and non-Down subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1996.tb00238.x
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  • 3
    Electronic Resource
    Electronic Resource
    Melatonin—A Highly Potent Endogenous Radical Scavenger and Electron Donor: New Aspects of the Oxidation Chemistry of this Indole Accessed in vitro (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 738 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb21831.x
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  • 4
    Electronic Resource
    Electronic Resource
    Melatonin stimulates the activity of the detoxifying enzyme glutathione peroxidase in several tissues of chicks (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 19 (1995), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The pineal hormone melatonin has been shown to directly scavenge free radicals and to stimulate, in the mammalian brain, at least one enzyme, glutathione peroxidase, which reduces free radical generation. In the present studies, we examined the effect of melatonin on glutathione peroxidase activity in several tissues of an avian species. Melatonin (500 μg/kg), when injected into chicks, increased glutathione peroxidase activity within 90 min in every tissue examined. Tissue melatonin levels, measured by radioimmunoassay, also increased following its peripheral administration. Depending on the tissue, the measured increases in melatonin varied from 75% to 1,300% over the control values. The melatonin-induced increases in glutathione peroxidase activity varied with the tissue and were between 22% and 134%. These percentage increases in glutathione peroxidase activity were directly correlated with tissue melatonin content. These results suggest that melatonin induces the activity of the detoxifying enzyme, glutathione peroxidase, in several tissues in the chick. The findings also suggest that melatonin would reduce the generation of highly toxic hydroxyl radicals by metabolizing its precursor, hydrogen peroxide. Because of this ability to stimulate glutathione peroxidase activity, melatonin should be considered as a component of the antioxidative defense system in this avian species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1995.tb00178.x
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  • 5
    Electronic Resource
    Electronic Resource
    Nuclear localization of melatonin in different mammalian tissues: Immunocytochemical and radioimmunoassay evidence (1993)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 53 (1993), S. 373-382 
    Details
    ISSN: 0730-2312
    Keywords: cell fractionation ; pinealectomy ; rat ; hamster ; mouse ; baboon ; liver ; brain ; gut ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Melatonin was detected by an improved immunocytochemical technique in the cell nuclei of most tissues studied including several brain areas, pineal gland, Harderian gland, gut, liver, kidney, and spleen from rodents and primates. Cryostat sections from tissues fixed in Bouin's fluid, formalin, or acetone/ethanol were used. The nuclear staining appeared primarily associated with the chromatin. The nucleoli did not exhibit a positive reaction. The melatonin antiserum was used in the range of 1:500 to 1:5,000. Incubation of the antibody with an excess of melatonin resulted in the complete blockade of nuclear staining. Pretreatment of the sections with proteinase K (200-1,000 ng/ml) prevented the positive immunoreaction. In a second aspect of the study, we estimated the concentration of melatonin by means of radioimmunoassay in the nuclear fraction of several tissues including cerebral cortex, liver, and gut. The subcutaneous injection of melatonin (500 μg/kg) to rats resulted, after 30 min, in a rapid increase in the nuclear concentration of immunoreactive melatonin which varied in a tissue-dependent manner. However, samples collected 3 h after the injection showed that melatonin levels had decreased to control values. Pinealectomy in rats resulted in a clear reduction in the nuclear content of melatonin in the cerebral cortex and liver but not in the gut. The results of these studies suggest that melatonin may interact with nuclear proteins and that the indole may have an important function at the nuclear level in a variety of mammalian tissues.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240530415
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  • 6
    Electronic Resource
    Electronic Resource
    Melatonin administration prevents lipopolysaccharide-induced oxidative damage in phenobarbital-treated animals (1995)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 58 (1995), S. 436-444 
    Details
    ISSN: 0730-2312
    Keywords: Key words ; melatonin ; glutathione ; lipopolysaccharide ; oxidative damage ; oxygen free radicals ; antioxidant ; phenobarbital ; cytochrome P450 reductase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The protective effect of melatonin on lipopolysaccharide (LPS)-induced oxidative damage in phenobarbital-treated rats was measured using the following parameters: changes in total glutathione (tGSH) concentration, levels of oxidized glutathione (GSSG), the activity of the antioxidant enzyme glutathione peroxidase (GSH-PX) in both brain and liver, and the content of cytochrome P450 reductase in liver. Melatonin was injected intraperitoneally (ip, 4mg/kg BW) every hour for 4 h after LPS administration; control animals received 4 injections of diluent. LPS was given (ip, 4 mg/kg) 6 h before the animals were killed. Prior to the LPS injection, animals were pretreated with phenobarbital (PB), a stimulator of cytochrome P450 reductase, at a dose 80 mg/kg BW ip for 3 consecutive days. One group of animals received LPS together with Nw-nitro-L-arginine methyl ester (L-NAME), a blocker of nitric oxide synthase (NOS) (for 4 days given in drinking water at a concentration of 50 mM). In liver, PB, in all groups, increased significantly both the concentration of tGSH and the activity of GSH-PX. When the animals were injected with LPS the levels of tGSH and GSSG were significantly higher compared with other groups while melatonin and L-NAME significantly enhanced tGSH when compared with that in the LPS-treated rats. Melatonin alone reduced GSSG levels and enhanced the activity of GSH-PX in LPS-treated animals. Additionally, LPS diminished the content of cytochrome P450 reductase with this effect being largely prevented by L-NAME administration. Melatonin did not change the content of P450 either in PB- or LPS-treated animals. In brain, melatonin and L-NAME increased both tGSH levels and the activity of GSH-PX in LPS-treated animals. The results suggest that melatonin protects against LPS-induced oxidative toxicity in PB-treated animals in both liver and brain, and the findings are consistent with previously published observations related to the antioxidant activity of the pineal hormone.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240580406
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  • 7
    Electronic Resource
    Electronic Resource
    Regularly scheduled, day-time, slow-onset 60 Hz electric and magnetic field exposure does not depress serum melatonin concentration in nonhuman primates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 111-118 
    Details
    ISSN: 0197-8462
    Keywords: baboon (Papio cynocephalus) ; cannula ; electric field ; magnetic field ; pineal gland ; radioimmunoassay ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Experiments conducted with laboratory rodents indicate that exposure to 60 Hz electric fields or magnetic fields can suppress nocturnal melatonin concentrations in pineal gland and blood. In three experiments employing three field-exposed and three sham-exposed nonhuman primates, each implanted with an indwelling venous cannula to allow repeated blood sampling, we studied the effects of either 6 kV/m and 50 μT (0.5 G) or 30 kV/m and 100 μT (1.0 G) on serum melatonin patterns. The fields were ramped on and off slowly, so that no transients occurred. Extensive quality control for the melatonin assay, computerized control and monitoring of field intensities, and consistent exposure protocols were used. No changes in nocturnal serum melatonin concentration resulted from 6 weeks of day-time exposure with slow field onset/offset and a highly regular exposure protocol. These results indicate that, under the conditions tested, day-time exposure to 60 Hz electric and magnetic fields in combination does not result in melatonin suppression in primates. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250160711
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  • 8
    Electronic Resource
    Electronic Resource
    Rapid-onset/offset, variably scheduled 60 Hz electric and magnetic field exposure reduces nocturnal serum melatonin concentration in nonhuman primates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 119-122 
    Details
    ISSN: 0197-8462
    Keywords: baboon (Papio cynocephalus) ; intermittent ; irregular ; pineal gland ; transient ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Experiments with rodents indicate that power-frequency electric field (EF) or magnetic field (MF) exposure can suppress the normal nocturnal increase in melatonin concentration in pineal gland and blood. In a separate set of three experiments conducted with nonhuman primates, we did not observe melatonin suppression as a result of 6 weeks of day-time exposure to combined 60 Hz electric and magnetic fields (E/MF) with regularly scheduled “slow” E/MF onsets/offsets. The study described here used a different exposure paradigm in which two baboons were exposed to E/MF with “rapid” E/MF onsets/offsets accompanied by EF transients not found with slowly ramped E/MF onset/offset; profound reductions in nocturnal serum melatonin concentration were observed in this experiment. If replicated in a more extensive experiment, the observation of melatonin suppression only in the presence of E/MF transients would suggest that very specific exposure parameters determine the effects of 60 Hz E/MF on melatonin. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250160712
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