Calcium acetate controls serum phosphorus and calcium-phosphate product more effectively than sevelamer hydrochloride. Cost-benefit analysis indicates that in the absence of hypercalcemia, calcium acetate should remain the treatment of choice for hyperphosphatemia in hemodialysis patients.

In order to determine whether the human pattern of circulating melatonin resembles that previously described in lower animals, men 19-32 years old were exposed to a light-dark cycle with 14 hours of light per day (L:D 14:10). In whites and blacks, nocturnal (dark phase, sleeping) melatonin levels were almost always elevated to 0.05-0.1 ng/ml plasma compared with lower or undetectable levels during the day, measured by the tadpole bioassay. Thin-layer migration of bioactive material was identical to that for melatonin standard. A rhythm with nocturnal elevation of urinary 5-hydroxyindoleacetic acid (5-HIAA) was observed. Nocturnal (sleep phase) rise in blood melatonin (but not urinary 5-HIAA) continued during 21/2 day-night cycle lengths after the onset of constant light. Though the dark phase plasma melatonin rise was less marked after reversal of the sleep-wake cycle (no change in the light cycle), dark phase rise in urinary 5-HIAA continued. Though marked cardiovascular and other effects were produced by intravenous isoproterenol or scopolamine, no definite effect on melatonin levels was observed after either drug during the light phase in waking subjects.

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SUMMARY BackgroundThe pharmacokinetics of polyethylene glycol 3350 (PEG-3350) have not been fully described because of lack of a sufficiently sensitive analytical method.

Melatonin, a suspected hormone of the pineal organ, was extracted from chicken serum and quantified by the Rana pipiens bioassay. When chickens were housed in an alternating light-dark photoperiod, serum melatonin was usually not detected during the light phase. Serum melatonin rose within 1 hr after the lights were extinguished, plateaued around midnight and fell before the lights were turned on. Serum melatonin was not detected at any time of day in pinealectomized chickens, suggesting that the pineal is neccessary for, and may be the source of, circulating melatonin.