Mammary transfer of 203 Hg from mothers to brains of nursing rats

Consumption habits of pregnant women and implications for developmental biology: a survey of predominantly Hispanic women in California

BACKGROUND

Healthy post-pregnancy outcomes are contingent upon an informed regimen of prenatal care encouraging healthy maternal consumption habits. In this article, we describe aspects of maternal intake of food, drink, and medication in a population of predominantly Hispanic women in Southern California. Potential implications for unhealthy prenatal dietary choices are discussed.

METHODS

The Food, Beverage, and Medication Intake Questionnaire (FBMIQ) measures common practices of maternal consumption during pregnancy. The FBMIQ was administered to English and Spanish speaking pregnant and recently pregnant (36 weeks pregnant - 8 weeks post-partum) women over the age of 18 who were receiving care from a private medical group in Downey CA.

RESULTS

A total of 200 women completed the FBMIQ. Consumption habits of healthy foods and beverages, unhealthy foods, unhealthy beverages, and medication are characterized in this article. Data indicate widespread consumption of fresh fruit, meats, milk and juice and indicate most women used prenatal vitamin supplements. Studies in developmental neuroscience have shown that certain substances may cause teratogenic effects on the fetus when ingested by the mother during pregnancy. Those potentially harmful substances included in our study were Bisphenol-A (BPA), methylmercury, caffeine, alcohol and certain medications. Our results show that a proportion of the women surveyed in our study consumed BPA, methylmercury, caffeine, alcohol, and certain medications at varied levels during pregnancy. This represents an interesting finding and suggests a disconnect between scientific data and general recommendations provided to pregnant mothers by obstetricians.

CONCLUSIONS

The results of our study demonstrate that a proportion of pregnant women consume substances that are potentially teratogenic and may impact the health and well being of the offspring. It is important to appraise healthy and unhealthy consumption habits in order to encourage healthy practices and alleviate future effects of preventable, toxin-induced developmental issues. Prenatal advising should discourage the consumption of dangerous foods, beverages, and medications that women commonly report eating during pregnancy.

Thyroid hormones and methylmercury toxicity

Thyroid hormones are essential for cellular metabolism, growth, and development. In particular, an adequate supply of thyroid hormones is critical for fetal neurodevelopment. Thyroid hormone tissue activation and inactivation in brain, liver, and other tissues is controlled by the deiodinases through the removal of iodine atoms. Selenium, an essential element critical for deiodinase activity, is sensitive to mercury and, therefore, when its availability is reduced, brain development might be altered. This review addresses the possibility that high exposures to the organometal, methylmercury (MeHg), may perturb neurodevelopmental processes by selectively affecting thyroid hormone homeostasis and function.

Effects of gestational methylmercury exposure on immunoreactivity of specific isoforms of PKC and enzyme activity during post-natal development of the rat brain

Protein kinase C (PKC)-mediated phosphorylation has been implicated in neuronal growth and differentiation [R.S. Turner, R.L. Mazzei, G.J. Raynor, P.R. Girard, J.F. Kuo, Proc. Natl. Acad. Sci. U.S.A., 81 (1984) 3143-3147.]. We examined effects of gestational exposure to the neurotoxicant, methylmercury (CH3Hg), on the developmental profile of immunoreactivity (IR) for alpha, beta, gamma and epsilon PKC isoforms and cytosolic PKC activity. Long-Evans dams were dosed on gestational days (GD)6-15 (p.o.) with 0, 1, or 2 mg kg-1 day-1 CH3Hg dissolved in saline. Pups were sacrificed and perfused with buffered paraformaldehyde on post-natal days (PND) 1, 4, 10, 21, 45 and 85. The brains were sectioned sagittally, stained immunohistochemically, and examined throughout the medial to lateral extent. IR in neuronal cell bodies for PKC isoforms alpha, beta, gamma, and epsilon was densest in the olfactory bulb, hippocampus, shell of the inferior colliculus, pons, cerebral, piriform, and cerebellar cortex, whereas axonal staining was prominent in the brainstem, internal capsule, corpus callosum, anterior commissure, fornix and olfactory tract. In controls, the PKC alpha and epsilon IR was highest on PND1-4, decreased dramatically by PND10, and decreased further by PND21. In the neonate, the regional and cellular distributions of alpha and epsilon IR were similar. The PKC gamma IR was greater at post-weaning ages (PND21-85) with the greatest regional density apparent in the hippocampus, cortex, and cerebellum. Only the highest dose of CH3Hg (2 mg kg-1 day-1; GD6-15) produced a persistent decrease in regional alpha and epsilon, but not beta or gamma IR during the post-natal period. These regional and time-dependent changes in PKC isoforms were complemented by the examination of PKC activity in cortex, olfactory bulb, cerebellum and brainstem. Cytosolic PKC activity increased from PND1 to 10 in cortex, olfactory bulb, and cerebellum. On PND21, PKC activity decreased in the cortex and olfactory bulb, but remained high in the cerebellum. By contrast, PKC activity in the brainstem was highest on PND1 and 4 and decreased dramatically by PND21. CH3Hg (2 mg kg-1 day-1) significantly decreased PKC activity on PND1 and 4 in the cortex. The present results characterize the cellular and regional ontogeny of PKC isoenzymes alpha, beta, gamma and epsilon, and indicate that developmental exposure to CH3Hg can alter the ontogeny of specific isoforms and regional PKC activity.

Heavy metal toxicities

Several reviews have been published recently on the toxicity of heavy metals, but few of these have made any reference to the influence of the nutritional state of animals upon their tolerance of heavy metals. Furthermore, the clinical and metabolic changes occurring as a consequence of increased dietary intake of heavy metals are extremely dependent on factors such as the mineral composition of the diet and nature of the protein source. These aspects will be given particular attention in this review.