The investigation of the embryonic development of the cerebellum has a long history. The postnatal normal development of the cerebellum in rodents and other animals became a popular topic for morphological investigations nearly a century ago. However, surprisingly, only a few studies are available regarding the prenatal normal development of the rodent cerebellum, especially in guinea pigs. Cell proliferation is essential for the development of the nervous system. The assessment of cell proliferation can be achieved by using various methods. In this study, we investigated the cell proliferation of the cerebellar cortex in guinea pigs at different stages of pregnancy and in postnatal life. Fetuses were obtained by cesarean section at 50 or 60 days of gestation (dg). Immunohistochemistry was performed with proliferating cell nuclear antigen (PCNA) antibody in the cerebellum. Strong PCNA immunoreactivity was observed in the external granular layer (EGL), which is a neurogenic zone in the cerebellum. The proportion of PCNA-IR cells was greater at 1 week than at 60 dg in lobule I, but not lobule VIII. After 50 dg, the width of the EGL continued to decline until 1 week, due to the maturation of the EGL cells. These results demonstrate the pattern of PCNA immunoreactivity in the developing cerebellum of guinea pigs. This serves as a guideline to study abnormal cerebellum development.

The purpose of the present study was to investigate differences in the sensitizing potential of Rhus Veniciflua(Rhus-II), when tested by the guinea pig maximization test(GPMT) and Freund's complete adjuvant test(FCAT) with an identical, intradermal induction concentration. A new grading. classification of the sensitization potential is proposed. The GPMT was conducted according to OECD guideline #406, using a multiple-dose design and test results were analysed with logistic regression analysis. During the induction stage, we injected intradermally each three site 0.1 ml( 1mg/animal) test material. 0.1ml complete Freund's adjuvant and 0.1ml the test agent emulsified in the adjuvant. 7 days later, we induced weak sensitization with 10% sodium lauryl sulfate(SLS) and applide 1ml(10mg/animal) test agent topically on the same site and made a tight occlusion. 14 days later we challenged with 1ml(10mg/animal) of test material on the flank and observed ant 24 hours and 48 hours later. The results were also observed 0% at 24 hours challenge. The results observed 48 hours after challenge were the identical. These data indicated that. although Rhus-II is a no contact allergen. It was reported that the skin sensitization by Rhus-II was not detected the skin sensitization in the guinea pig maximization test (GPMT). Consequently, it was confirmed that Rhus-Il had no contact allergic sensitization in guinea pig maximization test.