The esterase isozymes in the livers of mice were separated by agar-electrophoresis. The changes of esterase isozymes in the liver according to age were observed in C3H/HeN and ICR-JCL mice from birth to 56 days of age, and strain differences of the same isozymes were investigated in the AKR, BALB/c, C3H/HeN, C57BL/6, DBA/2, 4CS, DDD, KK, NC, CF#1-JCL, ddN-JCL and ICR-JCL strains. The results were summarised as follows.
1. Esterase isozymes in the livers of neonates showed a few partitions, but several partitions could be distinguished about 14 days after birth. The adult pattern became stable since about 40 days after birth.
2. Four different patterns of esterase isozymes in the livers were found in the various strains. The Type I pattern was the most common and found in AKR, BALB/c, CF#JCL, C3H/HeN DBA/2, ICR-JCL, 4CS and NC strains. Type II lacking the 2nd, 3rd and 4th anodal bands was found only in KK strain. In Type III observed in C57BL/6 strain, the first anodal band moved faster than in Type I. Type IV was found in DDD and ddN.JCL strains. In this type, the intermediate bands moved slower than in Type I. Several variations were found in ICR-JCL and ddN-JCL mice from closed-colony.

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[in Japanese]

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Rabbits of the Dutch strain were bred at the Nippon Merck-Banyu Research Laboratories, and some of their characteristics were compared with those of the Japanese White rabbit, which has been generally used in biomedical experiments in Japan. It was observed that the Dutch had the following advantages
1) Easy to handle for their small size andtameness.
2) Economical for their small food consumption (about a half of that of the Japanese white) .
3) Highly reproductive (the conception rate, 92%; the average litter size, 6.8; the mortality by the weaning, 24%) .
However, they seemed to be more susceptible to coccidiosis than the Japanese White.

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This note describes a case of the cesarean section applied to a female Cynomolgus monkey.
The monkey became pregnant by one-to-one mating in a cage under the feeding conditions of our laboratory monkey facility. Anorexia and body weight decrease were noticed after the 17th week of pregnancy. Besides, at the 21st week of pregnancy, transverse presentation of fetus was confirmed by roentgenography. These findings seemed to be indications for cesarean section.
The operation was carried out on the 150th day of pregnancy. Supine position was taken to restrain the animal on a wooden cross. Field of the operation was locally anesthetized with 2% HCIprocaine. Mid-line incision was made in the uterine body as the fetus showed the above-mentioned presentation and commonly Cynomolgus monkey have somewhat narrow pelvis. Any special surgical instrument was not necessary for the operation.
The newborn female monkey was vigorous and weighed 270 grams. She was nursed artificially by an animal care-taker and grew well. General and hematologic findings of the mother monkey recovered to normal about 4 weeks after the operation.

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Multiple focal necrotic lesions were observed in the liver of 8 3-week-old rats of the same litter among 120 youngs from 15 mothers treated with a steroid hormone. The lesions resembled those observed in Tyzzer's disease of mice and many PAS-positive bacillary bodies were detected within liver cells neibouring the necrotic foci. No evident correlation was noticed between the incidence of the disease and the hormone treatment.

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