ABSTRACT The genetic polydactyly/arhinencephaly mouse, Pdn/Pdn, exhibits severe polydactyly both in the fore-and hindlimbs, agenesis of the olfactory bulbs, corpus callosum, anterior commissure, and hydrocephalus. A candidate gene for the Pdn mouse has been speculated to be Gli3, because Pdn has been considered to be an allele of Xt whose responsible gene has been clarified to be Gli3. Recently, it has been cleared that retro-transposons are inserted into nitron 3, upstream of zinc finger domain, of the Gli3 gene in the Pdn mouse, resulting to the severe suppression of Gli3 gene expression in Pdn/Pdn embryos. Meanwhile, XtJ/XtJ mice exhibit more severe polydactyly than that of Pdn/Pdn. Arhinencephaly and microholoprosencephaly including agenesis of the olfactory bulbs, corpus callosum, anterior commissure, hippocampal commissure, habenular commissure, and posterior commissure, and moreover, the cerebral cortical plates and hippocampus are not formed in the XtJ/XtJ mice. The XtJ/XtJ mouse has a large deletion in Gli3 structural gene and shows null expression. From these corroborations, we speculated that the differences in the Gli3 gene expression levels resulted in the phenotypic differences between the Pdn/Pdn and XtJ/XtJ mice.
ABSTRACT Vascular endothelial growth factor (VEGF) is induced by hypoxic environment and contributes to vascular formation in both developing embryos and adults. Exogenous retinoic acid (RA) induces avascular yolk sacs with anemic stunted embryos of day 9 and 10 of gestation when RA is given to pregnant mice on day 6, 6.5 or 7 of pregnancy (Yasuda et al., 1996). We undertook the present studies to find out whether VEGF is activated and plays any role in those RA-exposed embryos. Embryos were obtained from dams given 60 mg/kg of RA on day 6 or 7 of pregnancy and sacrificed three days later. Most RA-exposed embryos showed edematous swelling without prominent vascular nets, but had beating heart tubes on day 9 and day 10 of gestation. Microscopic examination of developing tissue components showed various degrees of degeneration, and distension of the dorsal aorta when the body cavity was dosed. Northern blot analysis revealed expression of VEGF mRNA in the RA-exposed and control embryos. The highest expression of VEGF mRNA was seen in the embryos of day 10 exposed to RA on day 7, and these embryos had a significantly lower ATP content than did the controls (p < 0.01). Immunoreactive VEGF was detectable in both experimental and control embryos; in the former it was especially visible in the distended neuroepithelium, endothelium and membranes. These VEGF-immunoreactive regions also expressed another permeability factor, bradykinin. These findings suggest that VEGF upregulated by hypoxic conditions in edematous embryos induced by RA exposure in utero acts as hyperpermeability.
ABSTRACT In our previous studies, an administration of triphenyltin chloride (TPTCl) at 4.7 or 6.3 mg/kg on days 0–3 of pregnancy caused implantation failure, and the same doses of TPTCl on days 0–3 of pseudopregnancy caused a suppression of uterine decidualization correlated with a reduction in serum progesterone levels in rats. This study was conducted to determine the roles of progesterone on the TPTCl-induced suppression of uterine decidualization and implantation failure in rats. Although lower uterine weight was found in hormone-maintained ovariectomized rats given TPTCl at 4.7 or 6.3 mg/kg on days 0–3 and induced decidual cell response on day 4, no statistical significance in the uterine weight was detected between the control group and the TPTCl-treated groups. The pregnancy rate and number of implantations in the groups given TPTCl at 4.7 or 6.3 mg/kg on days 0–3 of pregnancy and progesterone on days 0–8 of pregnancy were significantly higher than those in the groups given TPTCl alone. No significant differences in these parameters were found between the control group and the groups given TPTCl and progesterone. It can be concluded that the TPTCl-induced suppression of uterine decidualization is mediated, at least partially, via the ovarian hormones, and that progesterone protects against the TPTCl-induced implantation failure.
ABSTRACT Aniline hydrochloride (AH), a methemoglobin formation-stimulating substance, at a dosage level of 520 mg/kg which does not induce apparent fetal death, was injected subcutaneously into pregnant rats once on day 14, 15 or 16 of gestation in order to assess the stage specificity of cleft palate induction. Also, doses of 260, 390, 520 and 650 mg/kg were administered to pregnant rats on day 15 of gestation, and the dose-response relationships with respect to fetal cleft palate and maternal methemo-globinemia induction were studied. In the stage-specificity study, paleness, decreased body weight gain and elevated methemoglobin concentration were noted in the dams treated with AH. Upon fetal examinations, although reduced body weight was noted in all AH-treated groups, cleft palate was observed only in fetuses from those dams treated on day 15 of gestation. In the dose-dependency study, AH induced maternal methemoglobinemia, decreased fetal body weight and increased the incidence of cleft palate dose dependently when administered at dosage levels of 260, 390, 520 and 650 mg/kg on day 15 of gestation. Additionally, administration of methylene blue, a methemoglobinemia-preventing substance, to the AH-treated dams ameliorated maternal methemoglobinemia and reduced the incidence of fetal cleft palate. In summation, it is considered that AH stage-specifically induces cleft palate in rats and that cleft palate is caused not by a direct teratogenic effect of AH but by maternal hypoxia due to methemoglobinemia.
ABSTRACT Aniline hydrochloride (AH), a methemoglobin-formation stimulating substance, at a dosage level that does not induce apparent fetal death was injected subcutaneously into pregnant rats once a day on days 6–8, 9–11, 12–14 or 15–17 of gestation in order to assess its ability to stage-specifically produce cardiovascular malformations. In addition, AH at dosage levels of 195, 260, 325 and 395 rag/kg was injected into pregnant rats subcutaneously once a day on days 12–14 of gestation, and the dose-dependent induction of ventricular septal defect (VSD) in relation to maternal methemoglobinemia was studied. In the stage-specificity study, paleness, decreased body weight gain and elevated methemoglobin concentration were noted in the dams. Upon fetal examination, reduced body weight was noted in all AH-treated groups. AH induced cardiovascular malformations, mainly VSD, which was most frequently observed in the day 12–14 group and also observed in the day 15–17 group. Abnormal branching of subclavian, pulmonary and vertebral arteries were most frequently observed in the day 9–11 group. In the dose-dependency study, AH induced maternal methemoglobinemia, decreased fetal body weight and increased the incidence of VSD dose dependency. Additionally, administration of methylene blue, a methemoglobinemia-preventing substance, to the AH-treated dams ameliorated maternal methemoglobinemia and reduced the incidence of fetal VSD. From these results, it is considered that AH stage-specifically induces cardiovascular defects, mainly VSD, in rats and that VSD is induced not by a direct teratogenic effect of AH but by maternal hypoxia due to methemoglobinemia.