Zinc toxicity following massive coin ingestion.

This is the first reported case of human fatality associated with zinc intoxication following a massive ingestion of coins. Four hundred and sixty-one coins were removed form the gastrointestinal tract of a schizophrenic patient during the course of hospitalization. Many of the post-1981 pennies, which consist primarily of zinc, showed severe corrosion due to their prolonged contact with acidic gastric juice. The patient presented with clinical manifestations consistent with the local corrosive as well as systemic effects of zinc intoxication and died 40 days after admission with multi-system organ failure. Tissue samples of the kidneys, pancreas, and liver obtained at autopsy revealed acute tubular necrosis, mild fibrosis, and acute massive necrosis, respectively, and contained high levels of zinc. The overall effects of zinc intoxication on the various organ systems, possible hematological derangement, and the impairment of copper absorption as well as the outcome with treatment are discussed.

Melatonin: a coordinating signal for mammalian reproduction?

There is a daily rhythm in the production of the pineal hormone melatonin in all mammalian species. Production is stimulated by darkness and inhibited by light. This provides a signal reflecting the changing environmental lighting cycle. In seasonally breeding mammals that use changes in the photoperiod to time their reproductive cycles, temporal signals to the reproductive system are controlled by the daily rhythm in melatonin production.

Regulation of luteinizing hormone release by pulsatile and continuous administration of gonadotropin-releasing hormone to superfused rat and hamster pituitary cells.

Regulation of LH release by GnRH was studied in superfused anterior pituitary cells from 30-day-old female rats or hamsters. Dispersed cells were cultured 4-6 days on Cytodex beads, then loaded into water-jacketed columns, and perfused with medium (0.5 ml/min) at 37 C. Three-minute fractions of effluent were assayed for LH by RIA. LH release was dose related between 10(-10) and 10(-7) M GnRH. Rat and hamster cells released LH at peak rates of 11.3 and 12.5 ng/(min X 10(6) cells), respectively, when first exposed to 10(-8) M GnRH. Short pulses (6 min) of 10(-8) M GnRH given at 30-min intervals had little effect on the rate of LH release by rat pituitary cells; however, if the interpulse interval was reduced to 12 min, release declined 72% by the fifth pulse. In contrast, pulses of 10(-6) M GnRH at 30-min intervals desensitized rat cells. Hamster cells were desensitized by 10(-8) M GnRH after a single pulse regardless of whether a second pulse was given 30 min or 2.5 h later. Similar desensitization also occurred at other doses (10(-9) and 10(-6) M). After five pulses at 30-min intervals, the LH release rate in hamster cells was depressed 65%. Release was depressed 80% by pulses at 12-min intervals. Thus, in rats, desensitization is both frequency and dose dependent, whereas in hamsters, it is independent of frequency and dose. Stimulation with 10(-6) M GnRH pulses completely overcame desensitization in both species. Continuous exposure of anterior pituitary cells to 10(-8) M GnRH caused an initial rapid LH release, followed by a steady decline in the rate of release from peak rates to baseline levels by 2.5 h in both species. A 6-min, 10(-6) M GnRH pulse given immediately after a 3-h 10(-8) M GnRH exposure rapidly stimulated the cells to release LH at rates up to 192% of initial rates. When these pulses were continued at 30-min intervals, additional desensitization occurred. This overcoming of desensitization shows that desensitized anterior pituitary cells are not refractory to GnRH and suggests that the GnRH regulation of LH release may involve more than one GnRH receptor-mediated phenomenon.