Time of perinatal immunization, thimerosal exposure and neurodevelopment at 6 months in breastfed infants.

AIM: Brazilian newborns immunized with hepatitis-B (thimerosal containing vaccine, TCV) receive the first dose within 24 h if delivered in public hospitals, but at a later time if born in private hospitals. We compared neurodevelopment (ND) in infants born in a state hospital (immunized within 24 h) and in privately run hospitals (immunized 2-4 days postnatally). METHODS: We used the Gesell Developmental Schedules in 82 healthy exclusively breastfed infants at 6 months to assess motor skills, language development, comprehension capacity and social skills. RESULTS: Compared to the group immunized 2-4 days after hospital discharge, the group immunized within 24 h showed no significant difference in ND delays. Despite the variation in gestational age (range 36-42 weeks) and TCV-ethylmercury (EtHg) dose (5.7-11.3 microg Hg/kg b.w.) at birth, time of exposure to TCV showed no significant association with ND. Gesell Developmental Score was not significantly correlated with total parenteral EtHg/unit of body mass neither with the relative increase in hair-Hg (as an additional challenge to prenatal Hg exposure). CONCLUSION: In breastfed infants, differences in early exposure to TCV-EtHg cannot portend clinical neurodevelopment delays at 6 months. We speculate that breastfeeding remains a significant strategy to improve central nervous system protection of infants facing early exposure challenges.

[The tissue distribution and the effect of mercury on the hepatic cholesterol biosynthesis following the oral administration of methyl- and ethylmercurial compounds (author's transl)].

Hepatic cholesterol biosynthesis from acetate-1-14C, hepatic cholesterol level and accumulation of mercury into various tissues were examined following oral administration of methyl- or ethyl-mercury to mice (or rat) at next dosage levels, 80 ppm for 10-19 days, 50 ppm for 30 days and 100 ppm for 15 days. The results obtained were as follows. 1. Hepatic cholesterol biosynthesis was elevated at a dose of 80 ppm and decreased at a dose of 50 and 100 ppm. The change of hepatic cholesterol biosynthesis showed the negative correlation with that of cholesterol level. 2. In comparison between methyl-and ethylmercury, the latter accumulated more than the former in liver and spleen, while the former accumulated more than the latter in kidney, cerebum and skeletal muscle. The administration of ethylmercury caused more decrease of body weight, increase of hepatic cholesterol biosynthesis and hepatic cholesterol level than the administration of methylmercury.

Teratogenicities of ophthalmic drugs. II. Teratogenicities and tissue accumulation of thimerosal.

Under the conditions of this study, systemically or topically applied thimerosal was found to have no teratogenic effect even when given in concentrations approaching the 50% lethal dose of these compounds. A comparison of topical and subcutaneous administration of thimerosal to rabbits shows that a substantial concentration of mercury was present in blood and tissues of the treated animals and their offspring. Thimerosal was found to cross the blood-brain and placenta barriers.