The reproduction and generation tests on barrier-sustained rats maintained on pellets exposed to 3 and 6 Mrad for sterilization were carried out. The rats fed the irradiated diets showed a reasonable reproduction rate through three successive generation, and all the animals grew well. The growth rate and diet comsumption were greater in young animals fed irradiated diets than in those fed autoclaved diets. In both 3 and 6 Mrad groups, no abnormality was observed in hematological, clinicobiochemical and pathological examinations made at the tenth weeks after birth.

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Several Strains of inbred mice (DDD, DDK, DDM, DKI, DDO, DSD, DY, etc) have been established in Japan from the common ancestor, so called “dd” mice which are not genetically uniform and have been maintained by pen-breeding [6, 9], and these strains are widely used for medical and biological researches [9] .
Unlike other strains, DSD mice have small litter size and low weaning rate and most of the new born pups in this strain die shortly after birth. These defects are not ameliorated by the improvement of feeding conditions. On the other hand, foster-nursing of the new born pups of DSD mice to the lactators of the other strains prevents the pups from death and results in the rise of weaning rate. Therefore, the inbreeding depression is likely to exert serious influence on some characteristics related to lactational performnance of this strain. Mammary development during pregnancy is an important factor for subsequent lactation.
The present experiment was carried out to compare mammary development and mammotropin levels of the pituitary and the placenta during pregnancy between DDD mice with normal rearing ability and DSD mice, as one step to elucidate the causes of the low rearing ability of DSD mice.
Virgin mice of both strains were mated with males at about 70 days of age. The day when vaginal plug or sperm was found or the last estrous day was designated as day 1 of pregnancy.
The body weight, number of placentae and anterior pituitary weight were significantly higher in DDD mice than in DSD mice (P<0.01) (Table 1) . DDD mice were also significantly higher than DSD mice in mammary lobulo-alve-olar formation on days 14 and 19 of pregnancy and in mammary nucleic acid contents on day 19 employed as the indices of mammary development (P<0.01) (Table 2) . Furthermore, DSD mice were inferior to C3H/He and C57BL/6 mice in these measures. Although mammary lobuloalveoli existed in the gland of DSD mice on day 14 of pregnancy, the developmental degree was much higher in DDD mice than in DSD mice (Fig.1-A, B) . On day 19, the well developed lobulo-alveoli covered the gland in DDD mice, and several alveoli contained the milk-like substance in their lumina (Fig.1—C) . On the other hand, the degree of lobulo-alveolar formation was much lower and no secretion was found in the alveoli in DSD mice even on day 19 (Fig.1—D) . Pituitary prolactin and growth hormone contents determined by disc electrophoresis [10] were significantly higher in DDD mice than in DSD mice (P<0.01), although there were little differences between strains in concentration per mg pituitary (Table 3) . Placental mammotropin level estimated by local mammary lobulo-alveolar de-2 times as many as that of the latter.
All the results would strongly suggest that the low pituitary and placental mammotropin secretion is one of the causes of low mammary development during pregnancy of DSD mice, which, in turn, might mostly account for the low rearing ability of this strain.
velopment of young C3H/He virgin mice injected with water extract equivalent to total 6 placentae was similar in both strains (Table 3), indicating that total placental mammotropin level was much higher in DDD mice than in DSD mice, because the number of placentae of the former was about

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Investigations were made on the susceptibility of the reproductive organs of inbred strain mice subcutaneously injected with human Chorionic gonadotopin (HCG) . The doses of HCG given per mouse were 1.5, 3.0 and 6.0 I.U. respectively. Immature female dd mice and 9 strains of inbred mice were employed. Each of them had a specificity in physiological features. The results are summerized as follows:
1) Body weight was found to be significantly different among the strains, both at time of injection (21 days) and autopsy (25 days) . However, no significant difference was observed with regard to doses of HCG.
2) When the vaginal opening was tested at time of injection, a significant difference was found among the strains of mice: Such strains of mice as C3H/He, RR and CFW were positive, but the other 7 strains were negative. The rate with which the positive vaginal opening occurred was higher in the strains of C3H/He and RR than in CFW. When autopsied after the injection of saline, DDK mice were negative for this response, whereas the other 9 strains of mice were positive, varying from strong to mild. The vaginal opening response differed significantly between the mice injected with saline and those with HCG. This finding was observed in each strain. No difference in the positivity was found, among the doses of HCG injected.
3) There was a significant difference in the hemorrhagic follicles and corpora lutea forming reaction among the strains of mice. A significant difference was found between AA and the following strains: DDK, C3H/He, NC and C57BL/6. On the other hand, significant differences were observed among all of the doses, except for 3.0: 6.0 I.U.
4) The ovarian weight reaction differed significantly among the strains of mice and the doses of HCG. It appears that the difference in this reaction was more strongly influenced by the strain of mice than by the doses of HCG. Significant differences were recognized among all of the doses, with the exception of 3.0 : 6.0 I.U.
5) As to the uterine weight reaction, a statistical difference was found in the strains of mice and the doses of HCG. The difference by doses was, however, more marked as compare with that by strains. The results of the uterine weight reaction differed from those of the ovarian weight reaction according to the doses of HCG given.
6) In any strain the results of the rate of vaginal opening response and the weight of ovary and uterus of mice were not connected with the body weight.
7) In any strain there were no relationship between the increase rate of the weight of ovary and uterus.
8) In regard to the uterine weight reaction to HCG within a litter, the variation in dd mice was more apparent than in the 9 strains of inbred mice. The reactivity was not uniform in the litter of dd mice.
9) The regression of the uterine weight reaction to HCG was significantly linear in various strains of mice. The variation ratio among the strains of mice was larger than that obtained for a single strain. The coefficient of Regression for the uterine weight reaction was linear and quodratic in C3H/He and CFW, linear and cubic in CF#1, but not in DDK, RR and NC. The coefficient of linear regression was statistically significant in AA, C57BL/6, SS and dd. This coefficient of the uterine weight reaction for AA mice was statistically higher than those for SS and dd.

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The changes in the reactivity of the reproductive organs to human chorionic gonadotropin (H CG) accrding to age were studied in dd mice and inbred strains of mice.
The results obtained are summarized as follows:
1) Vagina was not opend in saline injccted control dd mice (dd) at 15 days of age; however, vaginal opening was observed in 42% of 12 day old dd injected with HCG
The hemorrhagic follicles and corpora lutea formation were obsevred non of control animals in dd at 27 days of age, but were positive (80%) in injected with HCG at 18 days of age.
The ovarian weight was increased from 12 to 21 days in both of controls and HCG injected mice, but the uterine weight was significantly increased to HOG at 12 days of age in comparison with saline injectcd controls
2) At the time of the injection, C3H/He mice (C3H/He) showed vaginal opening at 18 days of age, SS mice (SS) and dd at 24 days of age; however, in CF#1 mice (CF#1), DDK mice (DDK) and C57BL/6 mice (C57BL/6) vagina were not opend at 24 days of age.
The vaginal opening reaction to HCG at the time of autopsy showed a high positive rate at 15 days of age in all the strains of mice except DDK and dd.
The hemorrhagic follicles and corpora lutea were not formed at 24 days of age in the various inbred strains of mice.
These response to HOG was not induced in the mice at 15 days of age, but it developed at 21 days of age in all inbred strain of mice; and it was recognized that there were differences in the reactivity among the strains at 18 days of age.
The ovarian weight reaction to saline and HOG in each age was significantly different among the various strains of mice. That is, the rate of increase in ovarian weight to HOG at 24 days of age proved to be an increasing type for SS and decreasing types for DDK, C57BL/6, CF#1 and dd.
The uterine weight reaction to HOG was significantly different in strains and ages, the difference in strains being larger than that in ages.
3) As for the vaginal opening reaction to HOG, a dose of 1.5 I.U. at 12 days of age induced a maximal response in SS. The hemorrhagic f olicles and corpora lutea formation was not induced in SS to HOG at 18 days of age but positive response was induced to HOG at 21 days of age, and a significant difference in the response to HOG was noted between the doses of 1.5 I.U. and 6.0 I.U. But there was no significant difference in the response by doses of HOG at 24 days of age. The ovarian weight reaction in SS was increased at 21 days of age due to the HOG administration a significant difference by doses of HOG was recognized at 24 days of age. The uterine weight reaction due to doses of HOG was significantly different in SS at 12 days of age; however, the response to 6.0 I.U. of HOG showed a tendency to decrease at 24 days of age.

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High serum lipid levels were obtaind in rabbits by consecutive daily bleeding with increasing volume over a six day period. The diet during breeding was shown to have a considerable effect on the elevation of lipids by use of rabbits fed on two dietary conditions. Biochemical analysis of serum and histological observations revealed the relation between the decrease of numbers of erythrocyte and the daily changes in the serum lipid and protein levels, and it was supported that hemic hypoxia results in an ischemia of whole cells and tissues.
Such hemorrhagic lipemia coupled with the improved method of bleeding in the rabbits under a controlled natural dietary condition may be used as a model for certain hypoxic diseases.

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MHV CF antibody survey in ex-breeder mice from an infected colony were done with routine and anamnestic serology, and antibody detection rates were 37/279 (13%) and 141/277 (51%) respectively (Table 1) . In contrast, all of 2153 sera from other 4 non-infected colonies were shown to be negative by the anamnestic method (Table 2) . With mice from the infected colony significant anamnestic response was induced after injection with 0.1 ml of about 4 or more units CF antigen (Table 3) .

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[in Japanese]

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[in Japanese]

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