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  • 1
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We evaluated the feasibility of using morning urine samples in epidemiological studies aimed at clarifying the relationship between nocturnal melatonin levels and breast cancer risk. Initially, a laboratory-based study of 29 women (40–70 yr old) was performed to examine the correlation between plasma melatonin levels in hourly nocturnal blood samples and both melatonin and its major enzymatic metabolite, 6-hydroxymelatonin-sulfate (6-OHMS) in morning urine samples. In a companion field study, morning urine samples were collected from 203 healthy women to assess similarities and differences in laboratory versus field measures. Taken together, our results indicate: 1) levels of melatonin and of creatinine-corrected 6-OHMS in the first morning void urine are strongly correlated with total nocturnal plasma melatonin output (P〈0.001) and also with peak nocturnal melatonin values (P〈0.001); 2) similar ranges for 6-OHMS were found in the laboratory and the field; and 3) neither menopausal status nor hormonal replacement therapy altered 6-OHMS values in morning void urine. The inclusion of morning urine samples in epidemiological studies of cancer could allow cost-effective, widespread testing of the role played by melatonin in human health and disease.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The objective of this study was to determine whether daytime occupational exposure to extremely low frequency magnetic fields (MFs) suppresses nocturnal melatonin production. Sixty female volunteers were recruited. Thirty-nine worked in a garment factory, and 21 office workers served as a reference group. Exposure assessment was based on the type of sewing machine used and MF measurements around each type of machine. Eye-level MF flux density was used to classify the operators to higher (〉1 μT) and lower (0.3–1 μT) exposure categories. A third group of factory workers had diverse MF exposures from other sources. The reference group had average exposure of about 0.15 μT. Urine samples were collected on Friday and Monday for three consecutive weeks. Melatonin production was assessed as urinary 6-hydroxymelatonin sulfate (6-OHMS) excretion. The ratio of Friday morning/Monday morning 6-OHMS was used to test the hypothesis that melatonin production is suppressed after 4 days of occupational MF exposure with significant recovery during the weekend. Possible chronic suppression of melatonin production was evaluated by studying exposure-related differences in the Friday values by multivariate regression analysis. The Monday/Friday ratios were close to 1.0, suggesting that there is no increase in melatonin production over the weekend. The average 6-OHMS excretion on Friday was lower among the factory workers than in the reference group, but no monotonous dose–response was observed. Multivariate regression analysis identified MF exposure, smoking, and age as significant explanatory variables associated with decreased 6-OHMS excretion.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 396-405 
    ISSN: 0197-8462
    Keywords: occupational exposure ; premature infants ; melatonin suppression ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Effects of light and electromagnetic fields (EMFs) on pineal function could have implications for long-term risk of breast cancer, reproductive irregularities, or depression. Health-care workers in a neonatal intensive care unit (NICU) were interviewed to determine the tasks, work locations, and practices in their work environment as well as the care provided to the infants. After an initial visit, methods for measuring illuminance, luminance, and broadband resultant magnetic fields throughout the NICU were developed. Measurements were made of one nursery during a daytime (1:00 p.m.) and a night-time (12:30 a.m.) visit. Measurements relevant to both nurses and premature infants in the NICU were made. Some measurements could not be completed so as not to interfere with nurses' duties in the NICU. Illuminances measured during the daytime and nighttime averaged 184 and 34 lux (lx), respectively, much lower than those reported in other studies of illuminance in NICUs, with a maximum illuminance of 747 lx. Peak levels may be consistent with those thought to suppress melatonin. There was a high degree of variability in EMF levels, which exceeded 1,000 mG close to certain hospital equipment but averaged 1-2 mG at the nurses' workstation. Fields within incubators exceeded 10 mG. © 1996 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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