A new mutant strain of rats with hereditary acholuric jaundice, now known as "Gunn rat", was discovered in 1934 by C.K. Gunn in the breeding stock of Wistar rats at the Connaught Laboratories, Toronto, Canada. The jaundiced condition has been characterized as an autosomal recessive inheritance, and the homozygote (jj) of Gunn rats is evidenced to be defective or extremely low in hepatic bilirubin UDP-glucuronyltransferase activity resulting in unconjugated hyperbilirubinemia and hence often kernicterus. From these points of view the Gunn strain of rats is generally regarded as an animal model comparable to a human inborn error of bilirubin metabolism, Crigler-Najjar syndrome, Type I, which is frequently accompanied by kernicterus in the neonatal period with rare exceptions. Hyperbilirubinemic Gunn rats have been used not only for biochemical and morphological investigations on pathogenic mechanisms of kernicterus including neurotoxicity of bilirubin in the central nervous system, but also for studies on the photochemical modification of bilirubin, the formation, transport, conjugation and excretion systems of the pigment in the liver and other tissues, mechanisms of renal urinary concentration insufficiency (polyuria) and cerebellar hypoplasia, behavioral disturbances and so forth. In this report we review advances in chemistry and metabolism of bilirubin, and biochemical, morphological and behavioral observations on the characteristic features of hyperbilirubinemic Gunn rats.

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Regular insulin and ultralente insulin were each administered sub-cutaneously (s.c.) in a single dose of 50 IU/body to adult female rats. Both types of insulin lowered blood glucose levels to a considerable degree in the first 1 hr, but they had a different duration of action; the ultralente insulin acted for more than 24 hr while regular insulin was effective for less than 12 hr. These two types of insulin with differently lasting hypoglycemic action were given s.c. in a dose of 50 IU/body/day to pregnant rats at different times during pregnancy. Regular insulin had no teratogenic effect but ultralente insulin specifically produced eye malformations, though not at a high incidence. Determinations of maternal blood glucose levels after s.c. dosing of 50 IU/body/day of ultralente insulin on days 6 - 8 of gestation revealed that most of the malformed fetuses were from among dams with hypoglycemia lasting until 48 hr after the last injection. The results of this study suggest that the teratogenic effect observed is closely related to the duration of maternal hypoglycemia.

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Although term "fetus in fetu" is well known, reports on this condition are scanty, and there have been only a score of authentic cases to date. One case of a 10-day old female was seen at this hospital with an abdominal tumor mass as the chief complaint. She was diagnosed as having this disease. Laparotomy revealed a tumor of the size of the head of a baby. It had a smooth surface and mobility and was covered with an amniotic tunica. The tumor was nourished by branches of the arteries and veins of the left kidney. When the tunica was cut open, about 300 ml of amniotic fluid were found. In the tumor there were parts which definitely looked like hands, feet, skin, fetal hair and nail. Histopathologically, tridermic tissues were all observed but the vertebra could not be confirmed. This case is a "probable" case according to the classification of Willis (1953) and Lord (1956).

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A case of congenital cystic adenomatoid malformation of the lung (CCAM) is reported. A 9-day-old newborn infant underwent successful lobectomy for CCAM. The lesion in the resected left lower lobe was composed of multiple large cysts. The cysts were lined by ciliated pseudostratified columnar epithelium with numerous polypoid projections. The wall of the cysts contained prominent smooth muscle and elastic tissue. Mucus producing cells were also present, however cartilage was not seen in the wall. Smaller cysts resembled dilated respiratory bronchioles or large alveoli were present adjacent to the larger cysts.

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Open-field behavior in rats with microcephaly induced by prenatal methylazoxymethanol acetate was studied. A significant deviation in start latency, outer ambulation, urination, latency of initial face washing and number of face washings was found in microcephalic rats compared to the controls.

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A mentally retarded male infant with multiple malformations is described. The patient's phenotype showed some resemblance to partial 4q trisomy syndrome. The cytogenetic analysis displayed a chromosome No.4 with an excess material attached to the distal end of the long arm, while normal karyotypes were confirmed in both parents.

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Cytogenetic analysis of mammalian oocytes is one of the useful methods for the detection of chromosomal mutagenic potential of environmental chemicals. So far, more than 20 chemicals have been examined for the induction of chromosome aberrations on the mammalian oocytes at various stages from dictyotene of the meiosis I to blastocysts. In this paper, these findings were reviewed and some technical aspects of these methods were discussed. Further, this technique of chromosome analysis of mammalian oocytes is thought to have wide applicability in the field of reproductive physiology.

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