Comparative studies was made on the whole processes of maturation of the secondary ossification centers in the extremity in the mouse, rat, dog and monkey in order to determine points of similarity and difference among these species. The appearance and the union of the secondary ossification centers were observed to follow a common sequence and order in all the species examined. The total bone score was defined as the sum of the bone scores of respective secondary ossification centers over the observation period according to a set criteria. By plotting these indices against the chronological age it was shown in all of these species that the whole process of maturation of the secondary ossification centers in the long bone consisted of three biological stages as indicated by the three straight lines with different slopes. The first stage is considered to account for the appearance of the secondary ossification centers and their accelerated development at early period, while the second stage corresponds to the subsequent gradual development. The third stage represents a period where the ossification centers reach a complete or almost complete union to diaphysis. It is concluded that in the mouse, rat, dog and monkey the maturation processes of the secondary ossification centers follow the same growth consisting of three developmental stages and that each of these three stages provides a measure of comparison among these species.

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In order to study the behavioral characteristics of F344/DuCrj (Fischer) strain rats, male rats of this strain were compared with those of the Wistar strain regarding both spontaneous motor activity and the processes of acquisition of conditioned avoidance responses under two types of avoidance situations, namely the Sidman (continuous) avoidance schedule and the discriminated (discrete) avoidance schedule with an escape contingency. It was found on the first point that the Fischer strain rats displayed higher activity than the Wistar strain rats under a 12: 12 hr light-dark situation. On the second point, strain differences were observed in the processes of acquisition of the avoidance responses. Here, in the early stage of the training, the Fischer strain rats received many shocks than the Wistar strain rats under the Sidman avoidance situation, while the wistar strain rats showed a lower avoidance rate than the Fischer strain rats under the discriminated avoidance situation. However, in the final stages of the training, no marked difference was observed in the results between the two strains. The present results suggest that the Fischer strain rats may show behavioral characteristics those differ from the Wistar strain rats.

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Hematological and clinical biochemistry values of two species of monkeys (Macaca mulatta and Macaca fascicularis) were measured by using auto-analyzers. WBC and RBC counts of M. fascicularis were high and Hb, MCV, MCH and MCHC values of M. fascicularis were low in comparison with those of M. mulatta. Albumin and creatinine levels of M. fascicularis were lower than those of M. mulatta. Total protein and AIP values of female M. fascicularis were higher than those of female M. mulatta. Differences between the sexes were observed in MCV, inorganic phosphorus, total protein, albumin and creatinine in M. mulatta, whereas in M. fascicularis, such differences were demonstrated as to creatinine, phospholipids and triglycerides.

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Strain differences of mice in the “Bruce effect” were examined among five inbred strains; C3H, C57BL/6, BALB/c, CBA and DDY. For mating, 3 virgin adult females were caged together with an adult male at 8-20 weeks of age, and checked daily for copulation for a maximum of 10 days. The females were removed from the male when the vaginal plug was found, and housed with strange or alien males for 8 or 15 days. The “Bruce effect” was evident in C3H, BALB/c, CBA and DDY strains having high percentages of blocked pregnancies on alien males. In contrast, C57BL/6 strain showed no such effect. Based on these findings, it was concluded that “Bruce effect” caused by alien male phero-mone showed strain differences among different strains of mice.

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Female germfree (Gf) and conventional (Cv) ICR mice aged 21-25 days were administered with hCG (50IU/head/day for 2 days) . Six hours after the last administration, uterine weights of Gf and Cv mice were 175.8 mg % and 238.7 mg % respectively, the difference between Gf and Cv animals was statistically significant (p<0.05) . Ovariectomized Gf and Cv mice aged 80-150 days were successively administered with estradiol benzoate (0.02 mg/head/day for 5 days) . Six hours after the last administration, uterine weights of Gf and Cv mice were 358.8 mg % and 462.7 mg % respectively, being statistically significant between Gf and Cv animals (p<0.01) . After administration of estradiol benzoate (0.02 mg/head/day for 2 days), 1.0 mg/head/day of progesterone for 3 days were given ovariectomized Gf and Cv mice aged 80-150 days. Six hours after the last administration, uterus of Gf and Cv mice were weighed 337.6 mg % and 423.5 mg % respectively, the difference was statistically significant (p<0.01) . Castrated Gf and Cv mice aged 80-150 days were administered with 1.0 mg of testosterone propionate (head/day for 5 days) . Six hours after the last administration, weights of seminal vesicle and coagulating gland of Gf and Cv mice were 376.0 mg % and 611.8 mg % respectively, the difference was statistically significant (p<0.01) .

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Methods for intravenous injection and blood collection by way of the forelimb in guinea pigs without anesthesia were investigated, with the results as follows: 1) Both the accessory cephalic and cephalic veins were found available for injection as well as for drawing blood samples. Venipuncture was accomplished with greater ease by using the accessory cephalic vein. 2) The following procedure has proven practical. (i) Clip the hair over the site. (ii) Restrain the animal to immobilize the foreleg in slight extension by grasping it at the elbow joint with the thumb and forefinger over its dorsal and ventral aspects, respectively. (iii) After disinfecting the skin surface with alcohol, perform injection using an appropriate syringe with a 27 (1/4) or 25 (1/3) gauge intravenous needle, or puncture the vein with a 23 (1/2) gauge i.v. needle to collect the blood that drips out.

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The non-surgical collection of rat embryos were examined. The apparatus for uterine flushing (Fig. 1 and 2) were designed to have a two-way system. Egg collection were made 5 days after mating. Eggs were collected from anesthetized donors using a pair of glass pipettes inserted to the end of each uterine horn through the cervix uteri. By non-surgical technique, it was successful to collect the eggs at an average of 4.0 from all the animal. The recovery rate was 40.7% as estimated the number of corpora lutea counted after the slaughter of the donor. The recovery rate in non-surgical methods was considerably lower as compared with that of the uterine flushing after the slaughter.

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Activity patterns of diurnal drinking behavior in male mice aged 12 to 20 weeks of IVCS, C3H/He and C57BL/6 strain were investigated in 14: 10 light-dark cycle. Drinking behavior activity of the mice synchronized with the light-dark alternation, thus showing regular 24-hr rhythms. The activity pattern of drinking behavior differed considerably among three strains. The highest activity of drinking behavior in IVCS mice was recorded around the time for lighting on and off, while in C3H/He and C57BL/6 mice it tended to be shown in the dark phase.

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Immunological characterization of nude rats (rnu/rnu) of outbred hooded stock was attempted. Antibody responses of IgM and IgG classes against thymus-dependent antigen, sheep red blood cells (SRBC), were detected in heterozygous (+/rnu) rats but were totally lacking in homozygous (rnu/rnu) nude rats. When mouse Sarcoma 180 was transplanted, tumor cells were not taken by heterozygous rats but grew in nude rats for more than 30 days showing marked tumor growth. Mitotic response to T-cell mitogens, concanavalin A and phytohemagglutinin, was seen in spleen cells of heterozygous but not of nude rats. It was concluded that the T-cell function is lacking in these nude rats.

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