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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 24 (1998), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Posture change from a lying position to a standing position results in a decrease in plasma volume, which leads to an increase in plasma constituents, especially that of proteins and blood constituents bound to them. The aim of the present study was to investigate the physiological effects of postural changes on plasma nocturnal melatonin concentrations in healthy human volunteers. The study was divided into four stages. During stage one, subjects were seated from 21.00 hr to 01.00 hr. In stage two, subjects were lying at ground level from 21.00 hr to 01.00 hr. In stage three, subjects were is a sitting position from 2100 hr to 2300 hr and then in a standing position from 23.00 hr to 24.00 hr, and back to the sitting position from 24.00 hr to 01.00 hr. In the final stage, subjects were in a lying position from 21.00 hr to 23.00 hr and then in a standing position from 23.00 rh to 24.00 hr and back to the lying position from 24.00 hr to 01.00 hr. AUC analysis showed significant differences between sitting and lying positions (t=2.84; P〈0.05; df=5), with higher melatonin levels associated with the sitting position (mean difference in peak concentration of 17.1 pg/ml). Furthermore a change in posture from the lying to the standing position produced a statistically significant increase in melatonin concentrations (final stage) (t=−3.37; P〈0.05; df=5) (mean difference in peak concentration of 28.5 pg/ml). No differences were found with a change in posture from a sitting to a standing position. The hemoconcentration and hemodilution associated with posture changes may play a role in altering plasma protein bound hormones such as melatonin.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 14 (1987), S. 0 
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Platelet monoamine oxidase (MAO) activity was investigated in 30 patients with Huntington's disease and compared with the activity in a control group.2. Significantly elevated activity was found in the patients (P 〈 0.05; t-test) when same sex contrasts were carried out to account for the well known influence of sex on MAO activity.3. The mean MAO activity in male patients was 23.5±6.0 nmol/mg protein per h and female patients was 29.5 ± 8.9 nmol/mg protein per h using tyramine as the substrate.4. The possible influence of environmental factors on the results is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Nathan PJ, Maguire KP, Burrows GD, Norman T.R. The effect of atenolol, a β1-adrenergic antagonist, on nocturnal plasma melatonin secretion: Evidence for a dose-response relationship in humans. J. Pineal Res. 1997; 23:131–135. © Munksgaard, Copenhagen〈section xml:id="abs1-1"〉〈title type="main"〉AbstractPineal β1-adrenergic receptors are involved in the regulation of melatonin secretion. The involvement of β1adrenergic receptors has been demonstrated by the ability of acute administration ofβ-antagonists to suppress the nocturnal rise of circulating melatonin and its urinary metabolite 6-sulphatoxymelatonin (aMT6s). The present study was undertaken to examine the relationship between increasing doses of atenolol and nocturnal plasma melatonin concentrations. Six healthy subjects participated in the study for a period of 5 weeks. Subjects were administered placebo, 12.5, 25, 37.5, and 50 mg doses of atenolol in a randomized single blind design. Each dose was separated by a 1 week washout period. Blood samples were collected at regular intervals from 19.00 hr to 06.00 hr. Repeated measures analysis of variance showed a dose-dependent decrease in plasma melatonin concentrations (P 〈 0.01). A Student Newman-Keuls post hoc test indicated significant differences between placebo and all doses of atenolol (P 〈 0.05). The results demonstrate a dose-dependent relationship between β1-receptor blockade and suppression of nocturnal plasma melatonin in humans.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 20 (1996), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Early investigations of the effect of sleep deprivation on plasma melatonin reported no major changes. Recently, 36 hrs of sleep deprivation was reported to elevate melatonin levels on the post-sleep deprivation night. Given these contradictions melatonin, Cortisol, prolactin, and thyroid stimulating hormone before, during, and, after sleep deprivation were examined in nine healthy young males following one night of sleep deprivation. Hormone levels at hourly intervals, for each night, were statistically analyzed by a repeated measures, two-way factorial ANOVA. ANOVA was also performed for measures of area under the curve (AUC). No significant differences were observed for melatonin levels. Cortisol was significantly higher on the sleep deprivation night presumably reflecting the aroused state accompanying being awake; however, there were several time points on the control night when it was elevated also. Prolactin was higher on the post-sleep deprivation and control nights but did not rise on the deprivation night, indicating a useful nonpolysomnographic index for discriminating overnight sleep and awake states. TSH levels showed a similar rise during the control and sleep deprivation nights, but remained flat on the post-sleep deprivation night. It appears that the pineal is insulated against feedback from changes to the level of arousal accompanying sleep and wakefulness. In comparison, Cortisol, prolactin, and TSH levels vary with these states and are, therefore, useful indices of arousal and sleep-wake.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 4 (1987), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Human plasma saliva were collected at frequent intervals throughout the night after a nocturnal challenge by exposure to 3,000 Ix of light for 1 h in the middle of the night. Melatonin, as measured by radioimmunoassay, was found to correlate highly in plasma saliva, described by a linear regression equation: y = 55x - 2.6 (r = 0.90). The nocturnal melatonin rhythm in saliva was parallel to that observed in plasma. A good correlation was also observed between plasma salivary melatonin on exposure to light. Melatonin in both fluids showed a significant fall during light exposure. Levels returned to normal nocturnal values within 2 h after returning to darkness. These results indicate that salivary melatonin, although lower than plasma melatonin, may be used as an index of pineal glrelease of melatonin. It is suggested that saliva may be useful as a non-invasive technique for obtaining data on melatonin profiles, especially in pilot-test screening situations.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 6 (1989), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Five intensities of artificial light were examined for the effect on nocturnal melatonin concentrations. Maximum suppression of melatonin following 1 hr of light at midnight was 71%, 67%, 44%, 38%, and 16% with intensities of 3,000, 1,000, 500, 350, and 200 lux (lx), respectively. In contrast to some previous reports, light of 1,000 lx intensity was sufficient to suppress melatonin to near daytime levels, and intensities down to 350 lx were shown to significantly suppress nocturnal melatonin levels below prelight values. On the basis of these data, it is suggested that when examining the melatonin sensitivity of patient groups (such as bipolar affective disorders) to artificial light, an appropriate light intensity should be established in each laboratory. Light of less intensity (e.g., 200–350 lx) may be more suitable to dichotomize patient groups from control subjects.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 21 (1996), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effect on nocturnal melatonin secretion of acute administration of the indirectly acting serotonin (5-HT) receptor agonists d-fenfluramine (30 mg) and paroxetine (20 mg) and a partial 5-HT1A receptor agonist ipsapirone (20 mg) was investigated in healthy male volunteers and compared to a placebo condition. Each subject (n=8) received each drug on one occasion over a 4 week study period, with drug administration separated by 1 week. A randomized, counter-balanced design was used. Drugs or placebo were administered at 2,000 hours in the light, and all blood samples were collected throughout the night in the dark at regular intervals until 0600 hours. Neither d-fenfluramine, paroxetine, or ipsapirone following acute dosage had a statistically significant effect on nocturnal melatonin synthesis. The lack of effect seen with d-fenfluramine, paroxetine, and ipsapirone may be due to limitations imposed by the dose requirements.
    Type of Medium: Electronic Resource
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