Résumé
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a highly toxic halogenated aromatic hydrocarbon, is a teratogen to induce cleft palate when exposed during the pregnancy. There are inter-strain differences in the sensitivity to cleft palate induced by TCDD and other chemicals including polychlorinated terphenyls (PCTs). The C57BL/6 mouse and the ddY mouse had been shown to be different in the induction of cleft palate following the treatment of PCTs, which attempts us to evaluate the TCDD-induced cleft palate in two mouse strains to understand the mechanism through which TCDD and PCTs induce cleft palate. This study evaluated the induction of cleft palate in the fetuses of ddY and C57BL/6 mice after subcutaneous treatment of TCDD on gestation day (GD) 10.5-14.5 or oral treatment on GD 8.5-13.5. Our results clearly showed that ddY mice, a susceptible strain to PCTs-induced cleft palate, are resistant to the induction of cleft palate by TCDD comparably to the high susceptibility of C57BL/6 mice, suggesting a different teratological mechanism between TCDD and PCTs. In addition, at the low doses, our study supported the concept of "window effect" of TCDD on around GD 12 for the induction of cleft palate in C57BL/6 and ddY mice.
Sujets)
Animaux , Femelle , Mâle , Souris , Grossesse , Administration par voie orale , Fente palatine/induit chimiquement , Maladies foetales/induit chimiquement , Incidence , Injections sous-cutanées , Souris de lignée C57BL , Polychloroterphényles/toxicité , Maladies des rongeurs/induit chimiquement , Tératogènes/toxicité , Dibenzodioxines polychlorées/administration et posologieRésumé
A single sublethal dose of Vacor (1 mg/rat) or Silmurin (50 microgram/rat) brought about dissimilar changes in cardiac physiology of bandicoot rats. Delayed myocardial repolarization and stress on cardiac tissues were noticed. Elevation of S-T segment above the isoelectric axis diagnostic of recent myocardial infarction was observed. Vacor and Silmurin induced differential changes in heartbeat; Vacor poisoning resulted in bradycardia, whereas Silmurin tachycardia. It is inferred that Vacor deaths may be due to bradycardia associated with atrioventricular block and that of Silmurin to delayed myocardial repolarization and tachycardia.