Offspring of women who smoke during pregnancy show behavioral abnormalities, including increased incidence of attentional deficit, learning disabilities, and cognitive dysfunction. Animal models indicate that nicotine elicits changes in neural cell replication and differentiation, leading to deficits in synaptic neurochemistry and behavioral performance, many of which first emerge at adolescence. We evaluated cellular morphology and regional architecture in the juvenile and adolescent hippocampus and the somatosensory cortex in rats exposed to nicotine prenatally. Pregnant rats were given nicotine throughout gestation via minipump infusion of 2 mg/kg/day, a regimen that elicits nicotine plasma levels comparable with those found in smokers. On postnatal days 21 and 30, brains were perfusionfixed, coronal slices were taken between the anterior commissure and median eminence, and the morphology of the dorsal hippocampus and somatosensory cortex was characterized. In the hippocampal CA3 region and dentate gyrus, we found a substantial decrease in cell size, with corresponding decrements in cell layer thickness, and increments in cell packing density. Smaller, transient changes were seen in CA1. In layer 5 of the somatosensory cortex, although there was no significant decrement in the average cell size, there was a reduction in the proportion of medium-sized pyramidal neurons, and an increase in the proportion of smaller, nonpyramidal cells. All regions showed elevated numbers of glia. Taken together with previous work on neurochemical and functional defects, these data demonstrate that prenatal nicotine exposure compromises neuronal maturation, leading to long-lasting alterations in the structure of key brain regions involved in cognition, learning, and memory.

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Chlorpyrifos is used increasingly as a pesticide in place of more toxic alternatives such as parathion. Although chlorpyrifos is not a potent dysmorphogen, recent reports that fetal or infant exposures may exceed acceptable limits have raised concern about the potentially more subtle effects on brain development. In the current study, whole rat embryo culture was used to study the effects of chlorpyrifos at the neural tube stage of development. On embryonic day 9.5, embryos were exposed to 0.5, 5, or 50 μg/ml of chlorpyrifos. After 48 hr (embryonic day 11.5), embryos were examined for dysmorphogenesis and were then processed for light microscopic examination of the neuroepithelium. Examination of 1‐μm‐thick toluidine blue‐stained sections of the forebrain and hindbrain region revealed reduced and altered mitotic figures, with dispersion and disorientation of the mitotic layer. In addition, cytotoxicity was evidenced by cytoplasmic vacuolation, enlargement of intercellular spaces, and the presence of a significant number of apoptotic cells. These alterations were evident even at the lowest concentration of chlorpyrifos, which produced no dysmorphogenesis. The effects were intensified at higher concentrations, which were just at the threshold for dysmorphogenesis; the neuroepithelial abnormalities, however, were still present in embryos that were not dysmorphogenic. Our results in rat embryo culture support the idea that chlorpyrifos specifically targets brain development at low concentrations, indicating the need to reevaluate the safety of this compound for exposure in vivo. Teratology 58:62–68, 1998. © 1998 Wiley‐Liss, Inc.

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The present study is probably the first systematic analysis of stereologic parameters in renal biopsies of IMGN with FSGS. Our results objectively demonstrate the glomerular enlargement in the non-sclerosed glomeruli in cases of IMGN with FSGS. This detection of enlarged glomeruli may serve to alert the renal pathologist to the possibility of coexisting FSGS, which is a poor prognostic factor in IMGN.