PubMed · 964222
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J Scotto, T R Fears, G B Gori. 1976. Ultraviolet exposure patterns.. https://doi.org/10.1016/0013-9351(76)90030-x
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Vitamin B12 (methylcobalamin) was administered orally (3 mg/day) to 9 healthy subjects for 4 weeks. Nocturnal melatonin levels after exposure to bright light (ca. 2500 lx) were determined, as well as the levels of plasma melatonin over 24 h. The timing of sleep was also recorded. Vitamin B12 was given blind to the subjects and crossed over with placebo. We found that the 24-h melatonin rhythm was significantly phase-advanced (1.1 h) in the vitamin B12 trial as compared with that in the placebo trial. In addition, the 24-h mean of plasma melatonin level was much lower in the vitamin B12 trial than with the placebo. Furthermore, the nocturnal melatonin levels during bright light exposure were significantly lower in the vitamin B12 trial than with the placebo. On the other hand, vitamin B12 did not affect the timing of sleep. These findings raise the possibility that vitamin B12 phase-advances the human circadian rhythm by increasing the light sensitivity of the circadian clock.
The 24-h activity patterns of various enzymes were determined in human serum, red blood cells and white blood cells of maternal and umbilical cord blood. Blood was drawn from the brachial vein of mothers and from the umbilical cord within ten minutes after delivery. Corresponding blood specimens were obtained from 83 spontaneous labors, occurring at different hours over a period of 60 days. For each variable (variable = activity of a specific enzyme in one of the blood components) the results were grouped according to delivery hour, forming a 24-h pattern which was analyzed to elucidate time dependency. Five out of six corresponding maternal and fetal variables were similar with regard to pattern and peak time. The activity rhythms of glyceraldehyde-3-phosphate dehydrogenase and glucose phosphate isomerase in red blood cells of mothers and fetuses possessed a significant bimodal pattern. The activity rhythms of the latter enzyme in white blood cells and sera exhibited a significant 24-h period. Hexosaminidase activity exhibited a distinct 24-h rhythm in maternal white blood cells, but no significant rhythm could be detected in the fetal white blood cells. The activity of hexosaminidase showed, identical 24-h patterns in maternal and cord serum when analyzed by best fit cosine, and no significant time-dependency when analyzed by ANOVA.