An animal model for chorioamnionitis at term.

OBJECTIVE: The purpose of this study was to develop an animal model for intrapartum inflammation at term to investigate the interactions between maternal and fetal inflammatory responses and adverse neurologic outcome. STUDY DESIGN: Lipopolysaccharide (160, 320, or 640 µg/kg) was administered intraperitoneally to day 20 term-pregnant Sprague Dawley rat dams 2, 4, and 6 hours before sample collection. Maternal outcomes included dam core temperature and plasma interleukin 6 (IL-6). Fetal outcomes included plasma IL-6, brain IL-6 messenger RNA expression, and brain IL-6 protein expression. Primary cortical cell cultures were prepared to examine neuronal morphologic condition. Neurite counts were obtained with the use of automated Sholl analysis. RESULTS: Maternal plasma IL-6 levels peaked 2 hours after lipopolysaccharide stimulus and rapidly resolved, except for an observed low level persistence at 6 hours with 640 µg/kg. Fetal plasma and placental IL-6 expression also peaked rapidly but only persisted in placental samples. Fetal brain IL-6 RNA and protein expression was significantly higher than control litters at 6 hours after the exposure to both 320 µg/kg (P ≤ .05) and 640 µg/kg (P ≤ .01). Cortical cells from fetuses that were exposed for 6 hours to maternal systemic inflammation showed reduced neurite number and neurite length (P < .001) with increasing lipopolysaccharide dose. CONCLUSION: Our results demonstrate that fetal brain injury follows isolated systemic maternal inflammation and that fetal brain inflammation lags after maternal stimulus, which creates a potential 4-hour clinical window for therapeutic intervention.

In vitro effects of yessotoxin on a primary culture of rat cardiomyocytes.

Oral administration of yessotoxin (YTX) has been reported to induce ultrastructural alterations in rodent cardiac muscle. To study its effects on various fundamental aspects of cardiac muscle cells activity, that is, cell beating, Ca(2+) and cyclic adenosine 3',5'-monophosphate (cAMP) levels, as well as cell vitality, a primary culture of rat cardiomyocytes was used. Patch-clamp recordings, Ca(2+) imaging, and cAMP assays were performed on cultured cardiomyocytes to characterize YTX effects on the cell beating frequency. 3-(4,5-Dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) and sulforhodamine B (SRB) tests were carried out to determine its effect on cardiomyocytes viability. Videoimaging techniques showed a time- and concentration-dependent reduction in the beating frequency after 1, 5, and 24 h incubation with YTX (0.1-1 microM). This effect was neither associated to the uncoupling between the membrane electrical activity and Ca(2+) release from intracellular stores nor to the impairment of the mechanisms controlling the Ca(2+) homeostasis. In addition, 1 microM YTX did not modify basal cAMP levels in cardiomyocytes. MTT and SRB assays revealed that incubation of cardiomyocytes with YTX (0.01-1 microM; 24, 48, and 72 h) caused a decrease in cell viability in a concentration- and time-dependent way. This effect was still evident in cardiomyocytes exposed to YTX for 1, 5, and 24 h and cultured up to 72 h in YTX-free medium. Our results demonstrate that, at nanomolar concentrations, a short incubation with YTX causes an inhibition of the beating activity and an irreversible reduction of viability of cardiac cells in vitro.