An Assessment of Mutagenic Effect of 3, 3', 4, 4', 5 Pentachlorobiphenyl (PCB126) in Muta Mouse Fetuses.

PCBs are persistent environmental agents that induce multiple impairments in living beings. In this study we used a transgenic mouse model (Muta(TM) Mouse), carrying bacterial lacZ genes for mutation assays and for assessment of the genotoxic effect of PCB126 on fetal mice. Mothers of experimental groups were subjected to a single oral dose of PCB126 (125, 250 and 500 microg/kg) on the 10th day of pregnancy, respectively. Fetuses were autopsied on the 18th day of gestation. Cleft palate was observed in 2 out of 11 fetuses from 3 litters in 500 microg/kg treated group. Other external malformations were not observed. The DNA mutation frequencies (MF) of fetuses in each group were 1.15 +/- 0.24 x 10(-5), 0.90 +/- 0.20 x 10(-5) and 1.08 +/- 0.24 x 10(-5) in fetuses of 125, 250 and 500 microg/kg treated groups, respectively. The MF of controls was 0.81 +/- 0.22 x 10(-5). There were no significant differences among the groups. However, the MF of each treated group was a little highter than that of control group. Possible relationships between PCB and its mutagenic effects in the offspring of mice are discussed.

Development of external genitalia in fetal and neonatal domestic cats.

Development of the external genitalia of fetal and neonatal cat were studied macroscopically, paying attention to the formation of the labia and the sexual differentiation. The female urogenital folds budded from each side of the genital tubercle and, gradually extended to the tip of the genital tubercle by the 6.8 cm stage in crown-rump length. Then, the well-developed urogenital folds ensheathed completely the genital tubercle to form the prepuce of clitoris and the labia, flanking the external opening of vagina as the folds of skin which were equivalent to the labia minora in humans. The genital swellings known to become the labia majora in humans were clearly recognized in the caudolateral region of the genital tubercle during the fetal stage. These swellings became flat and obscure after birth. Thus, in cats the genital swellings did not join to the formation of the labia in the same way as in humans. The sex difference in the external genitalia was first observed at the 3.2-3.3 cm stages. In the male, the anogenital raphe appeared and the caudal portion of the genital swellings moved and fused each other at the caudal region of the genital tubercle. In the female, both features were not easy to observe.

Developmental changes of Müllerian and Wolffian ducts in domestic cat fetuses.

At 0.8 cm of crown-rump length (CRL) in sexually undifferentiated cat fetuses, the Wolffian duct is already observable on the ventro-lateral side of the mesonephros. At 1.2 cm CRL, the anlage of the Müllerian duct growing caudally in close parallel with the Wolffian duct was first observed. At 2.8 cm CRL in sexually differentiated fetuses, the Müllerian duct reached the urogenital sinus but remained indiscernible. Subsequently, at 3.2 cm CRL, regression of the upper part of the Müllerian duct was visible in males, while both ducts continued to grow in females. This suggests that the Müllerian inhibiting substance is produced before 3.2 cm CRL. At 7.0 cm CRL, male and female Wolffian ducts were reduced in diameter by about 50%, accompanied by involution of the mesonephros. Thereafter, the Wolffian duct was retained in the male; however, at 8.5 cm CRL in the female, the Wolffian duct was greatly reduced, by about 80% in diameter, then disappeared completely at 9.0 cm CRL.

A simple method for sutureless gastrointestinal anastomosis in rat.

A simple tubing stent was attempted to test a model for sutureless gastrointestinal anastomosis in 6 male rats at the age of 15 weeks. In the 3rd and 4th weeks after the operation, X-ray examination demonstrated that the gastrointestinal passage in the anastomotic site was quite satisfactory. There was no incidence of anastomotic leakage. In the 6th week after the operation, there were no macroscopic or microscopic ruptures, nor were there any obstructions at the anastomotic site. This simple sutureless method was effective at preparing anastomosis in the gastrointestinal tract in the rat and could be applied to other small experimental animals.