Age-related histological changes were studied in various organs from SD-JCL rats reared throughout their lifespan. In aged-male rats examined at 5 to 36 months of age were frequently observed nephropathy, periarteritis, skeketal muscle degeneraion, pigmentation of the follicular epithelium in the thyroid, fibrosis of the pancreatic islets, hyperplasia of the parathyroid epithelium, and changes of the acini in the extraorbital lacrymal gland. In aged-female rats sinusoid dilatation of the adrenal, and atrophy of the ovary were also noted. Perilobular fat deposition of the liver, dilatation of the gastric gland and severe hemosiderosis of the spleen were observed similar frequency in the both sexes. The nephropathy and cardiovasculopathy were major factors to cause death for males, while the main cause of death for females was tumors, especially of the mammary and pituitary glands. Enlargement of the parathyroid gland, bone resorption and metastatic calcification in the soft tissues were found in rats with severe nephropathy.

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Incidence of spontaneous tumors was examined in 77 male and 73 female SDJCL rats reared throughout their lifespan of 5 to 36 months. Total tumor incidences were 60 % and 95 % for males and females, respectively. The sex difference was mostly attributable to a high incidence of mammary tumor in females. The pituitary tumor was found in 30 % of males and 66 % of females aged 5 to 36 months while islet cell tumor of the pancreas and thyroid tumor occurred later and the incidence of latter was particulary high in rats lived more than 2 years. Myeloid leukemia appeared to occur as early as 5 months of age.

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An efficient and simplified method for hand-rearing of Caesarean-derived infant rabbits under gnotobiotic condition was devised. The Caesarean-derived infant Dutch or Japanese-White rabbits and their hybrids (F₁ ; Japanese-White _??_× Dutch _??_) were reared in sterilized vinyl-isolators by hand-feeding with two kinds of milk diets, A and B, consisted mainly of a commercial milk powder for dogs and cats (Esbilac ^®) supplemented with several minor components (Table 2) and administered intragastrically once a day through a Nelaton's catheter. Bacteriological examinations revealed that feces and urine were sterile for the first three days. On the third day, Escherichia coli, Staphylococcus epidermidis, Streptococcus faecalis, Bacillus subtilis, Enterococcus, and Bacteroides sp. were given with milk diet and the infant rabbits were reared until 10 to 12 weeks of age. The weaning rate at 5 weeks of age and the raising rate at 3 months of age were approximately 78 % and 77 %, respectively (Table 3), indicating that feeding once-a-day with a milk diet mainly composed of Esbilac^® is suitable for the hand-rearing of infant rabbits. There was, however, no significant difference milk diet A and B on the weaning rate.

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This paper describes changes in the uterine size during the normal course of pregnancy in cynomolgus monkeys. Twenty-four females which had conceived by 3-day individual mating with a male were laparotomized 4, 5, 6, 7, 8, 9, 10, 15 and 20 weeks after conception. The width, thickness and length of uterus were measured by a pair of callipers. Then, the uterine volume was estimated by the formula, V = 4/3 2rab² (a, b : uterine length × 1/2, uterine width × 1/2) . The increase in the uterine width (y) during pregnancy could be expressed as a linear equation : y=0.35x + 1.48 (x : weeks after conception) . The thickness of pregnant uteri could be represented by a linear equation : y = 0.36x + 1.40. From the 4 th to the 20th week of pregnancy, the uterine length increased along a straight line expressed as a linear equation : y = 0.58x + 1.14. Except for nonpregnant uteri, the change in the uterine volume after pregnancy could be expressed as a linear logarithmic equation : log y = 2.319 log x = 0.315. These 24 pregnant monkeys had followed the normal course of gestation until the time of laparotomy without any abnormality in their fetuses or their placentas, indicating that the values obtained throughout this study are of practical use for taking care of pregnant cynomolgus monkeys.

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We attempted the breeding experiment in order to establish an inbred strain of disease model animal derived from a spontaneously hyperlipidemic rabbit (HLR) . The clinical, pathological features and breeding results of HLR strain were as follows ; 1) A prominent clinical feature of this strain was conspicuous elevation of serous lipid ingredients including cholesterol (S-ch), β-lipoprotein (β-LP) . The S-ch level was 400 ± 70 mg/dl, the β-LP level 9.1 ± 1.5 unit and the total lipid 1146 ± 270 mg/dl in the HLR strain. These values were approximately 9, 10 and 4 times higher than those of normal rabbits respectively. 2) After sacrifice, aterosclerotic lesions were evident extensively in the aorta and renal arteries. Nodular or plane xanthomas were conspicuous over the articuli digitorum of manus and pedis. 3) HLR strain indicated a striking resemblance of the condition to type III hyperlipidemia in the Fredrickson's classification of hyperlipidemia in man. 4) Inbreeding was carried out in two lines, viz. sister-brother mating, parent-offspring mating and back crossing. As the result, the second filial generation showed an incidence of HLR of 15.0%, the third generation 50.0%, and the fourth generation 56.1% respectively. In the fourth generation, the coefficients of inbreeding and relationship were 50% ann 72.3% respectively.

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In order to check genetic purity of inbred strains of mice, we surveyed five biochemical variants in certain 69 strains, some of which had established from Japanese fancy mice. The loci examined were Hemoglobin beta-chain, Malic enzyme (supernatant form), Isocitrate dehydrogenase (supernatant form), Serum esterase-1, and Serum esterase-2. These loci were all in homozygous states as far as examined, however, some subline divergences were found in a few strains, that is to say, sublines were found to be fixed with different alleles at some loci. Importance of biochemical marker genes to check genetic purity of strains and several derived problems are mentioned.

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For the purpose of experimental infection with human hepatitis B virus, 14 chimpanzees (Pan troglodytes) were delivered to the Division of Animal Research, Faculty of Medicine, University of Tokyo, Tokyo. These chimps, 11 males and 3 females, born in the West Africa, had been reared in America for two to six months. Several days after delivery, they were anesthetized with Ketalar in order to make clinical, bacteriological and parasitological examinations. It was found that one of them was in malnutrition, and that another had dislocation of the shoulder joint and the associating abscess. All of them were negative for tuberculin test. In the bacteriological examinations, Skigella sonnei was detected in the feces from one of them. Mycoplasma sp. was detected in the materials from the oral cavity of four head. As intestinal parasites, Ascaris sp. were detected in two head, Enterobius vermicularis in eight, Strongyloides sp, in two, Oesophagostomum sp. in nine, tape worms in four, and Entamoeba coli in twelve. Microfilaria as blood parasite was detected in 11 of them. The laboratory used for the experimental infection was a room occupying about 42 m², which had been built by renovating a part of our division building. Each of the cages used for rearing the chimps was contained in the isolation box made of stainless steel. The contaminated air in the isolation box was discharged forcedly into the exhausting duct with a fan, and further passed through the HEPA filter and the Miraceram honeycomb heater, and was then conducted to the already existing ventilation duct of the division building. Each chimp was fed on a ration of 200-350 g of the inported“Purina Monkey Chow 25”and also one grapefruit and one banana daily for the supply of vitamin C. The chimps weighed 16. 1 kg on the average on delivery, but gained an average weight of 4.2 kg during the following four months.

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