ABSTRACT Pathogenesis of lumbosacral agenesis following trypan blue treatment was studied in rats. Pregnant rats (on day 8 of pregnancy) were intraperitoneally injected with 2% trypan blue (40 mg/kg), and the fetuses at various stages of gestation were submitted to morphological examination. Every fetuses were observed under a stereoscop- ic microscope, and serial sections of the lumbosacral region were made for light microsco- py. Fetal growth was classified into 6 stages based on the fetal posture and the development of neutral tube. At Stage 2 (corresponding to gestational age of 237 2 6 hours) and at later stages, a cystic change was found stereoscopically on the dorsal side of the tail end in 23-33% of the fetuses. The cyst was unilocular or multilocular and was seen on one side or both sides of neural groove. After Stage 3 (240 +- 6 hours), the cysts were enlarged. At Stage 5 (252 +- 6 hours), cysts were various in shape and size. The initial histological lesion induced by trypan blue was edematous splitting of the intercellular spaces in the mesoderm and resultant cyst formation. After Stage 3, cysts in the mesoderm pushed the neural epithelium towards the back and caused deformation of the neural groove. After day 13, characteristic changes of lumbosacral agenesis, such as tail defect, short tail, and hind leg deformation, were observed in 20-30070 of the fetuses. At day 21, lumbosacral agenesis was recognized on soft X-ray films. The site and incidence of lumbosacral agenesis corresponded with those of cyst formation in an early gestation period. The present experiment showed that the cystic change in the mesoderm is the early and primary histological lesion of trypan blue-induced lumbosacral agenesis, and that alteration of the neural tube is secondary to the cystic change of the mesoderm.
ABSTRACT Relationships between plasma total or unbound bilirubin level and cerebellar bilirubin level were examined during the first 14 days after birth in homozygous Gunn rats with hyperbilirubinemia. Correlation coefficients between plasma total and cerebellar bilirubin levels were 0.63, 0.74, 0.48 and 0.60 at days 3, 7, 9 and 11, respectively, and were all significant, whereas the coefficient at day 14 (0.10) was not significant. The correlation coefficients between plasma unbound and cerebellar bilirubin levels were 0.40, 0.09, and 0.12 at days 7, 11 and 14, respectively, and were not significant. Thus, the cerebellar bilirubin level is suggested to depend on the plasma total bilirubin level from day 3 to 11.
ABSTRACT Bilateral hypoplastic kidneys have been found to associate with the male hypogonadism rat (hgn/hgn). The hypoplastic kidney was persistent to the male homozygote for hgn and it was also seen in some females with unknown genotype. The affected kidney was apparently smaller in size than phenotypically normal one. When females with hypoplastic kidney were mated to proven heterozygous males for hypogonadism (hgn/ +), the ratio of the affected testis to phenotypically normal one was 32 : 20 in the FI generation. This segregation ratio did not deviate siginificantly from the 1 : 1 ratio expected from the hypothesis that the genotype of females with hypoplastic kidney in parent generation for hypogonadism would consist of hgn/hgn alone. The ratio expected from the other hypotheses was denied statistically. The ratio of the affected kidney to phenotypically normal one in both sexs of the FI was 53 : 50, fitting to 1 : 1 hypothesis for a single autosomal recessive trait. There was neither a case showing the phenotypically normal kidney with the affected testis, nor the hypoplastic kidney with the phenotypically normal testis. The results suggest that the gene responsible for the hypoplastic kidney and the gene for hypogonadism would be identical or both genes reside in the close vicinity in a chromosome. The results also suggest that the homozygotes for hgn can be selected by the presence of hypoplastic kidney.
ABSTRACT Embryos with heart tube malformations on the 2nd and 3rd day of incu- bation were selected to support the hypothesis that the heart tube rotates and bends to the right due to the stronger tension generated on the right side of the heart primordium than that on the left side. In 4 embryos, lateral endothelial heart tubes did not fuse at the midline, and each heart tube looped independently. It is suggested that each lateral heart tube generates tension, and can bend to its own side. In 8 conjoined twins in which 2 embryos shared a head and each embryo extended in opposite directions, lateral endothelial heart tubes did not fuse within the embryo on the ventral side, but fused between the sister embryos lateral to the embryos. Such heart tubes bent to the left. Since the heart tubes fused between the sister embryos, the heart primordium on the right side for each embryo occupied the left side of the fused heart tube. Thus in this case our hypothesis that the right-side-derived heart tube generates stronger tension for bending is valid. Heart tubes of 5 other parallel twins also supported our hypothesis.
ABSTRACT The effects of oral dosing of folic acid (FA) on pyrimethamine (PYR) teratogenesis were examined in Goettingen minipigs. PYR (3.6 mg/kg/day) was orally ad- ministered in the feed to sows with or without FA (2.5, 10 or 50 mg/kg/day) for 12 days, (days 11 - 22 of gestation). Major malformations, such as cleft palate, cleft lips, micrognathia and clubfoot, were observed in all treated groups. The incidence of mal- formed fetuses decreased dose-dependently as the FA level was raised. This new finding suggests FA administration may prevent newborns from PYR induced malformations. This result contrasts in the observations in rats, in which PYR teratogenesis was potentiated by the concurrent oral dosing of FA. Neither PYR blood concentrations nor plasma protein binding was significantly affected by FA dosing in nonpregnant sows. These results suggest a mechanism other than pharmacokinetic modification was responsible for the protective effect of FA on PYR teratogenesis in minipigs.
ABSTRACT In order to establish an in vitro screening assay system for cleft palate- inducing teratogens, we tested 3 1 teratogenic and 10 honteratogenic compounds using human embryonic cultured cells. We examined whether cleft palate-inducing ability can be detected by differential growth inhibition between human embryonic palatal mesenchymal (HEPM) cells and human embryonic fibroblasts (MRC-5). Thirty one compounds with proven cleft palate-inductive effects in vivo preferentially inhibited the proliferation of HEPM cells. The average of the relative resistant rates (rate of IC50 value for HEPM cells to MRC-5 cells) of teratogens was 0.53. In contrast, almost all nonteratogens identically inhibited the proliferation of both cell lines and the average of the relative resistant rates was 1.01. These results show that teratogens which induce cleft palate in vivo preferentially inhibit the proliferation of embryonic palatal mesenchymal cells. The data indicated that in vifro screening using HEPM and MRC-5 cells is useful for detecting the cleft palate-inducing ability of chemicals.