The bronchial reactivities in Hartley guinea pigs to acetylcholine (ACh) or histamine (Hist) were investigated, and the following results obtained; 1. Eight-week-old animals were exposed to ACh and Hist. A significant relationship was observed between the concentrations of the chemicals and the time needed to produce falling down (TNPFD) due to the asthmatic reaction to ACh and Hist. 2. Eight-week-old animals were exposed to 0. 1 % ACh and 0.05 % Hist, for which the mean TNPFD ± standard error were 377 ±33 sec and 122 ±5 sec respectivity. However, no difference in reactivity between male and female animals was noted. 3. Eight-and 9-week-old animals were exposed to 0.01 % ACh and 0.025 % Hist. A positive correlation was observed (r=0.736, p <0.01) between the TNPFD for ACh and that for Hist. 4. Growing animals from 2 weeks to 20 weeks old were exposed to 0.08% ACh and 0.025% Hist. After inhalation of both chemicals, 6-week-old animals showed the greatest prolongation of mean TNPFD (lowest sensitivity) . 5. Eight-week-old animals were exposed to 0.08% ACh and 0.025% Hist. With both of these chemicals, a positive correlation was observed between TNPFD and dose threshold (ACh r= 0.886, p<0.001 ; Hist r=0.891, p<0, 001) .

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IV CS mice (ddN origin) aged 90 days (control) and 180, 210, 240, 270, 300, 330, 360 and 420 days were used for observation of the length of the estrous cycle, and the numbers of ovulated and fertilized ova. The estrous cycle between the ages of 90 and 330 days presented a regular 4-day pattern. Thereafter, regularity of the cycle declined steadily between the ages of 360 and 420 days. All mice over 420 days old exhibited cessation of cyclicity and ultimately persistent diestrus. The average number of ova ovulated in mice aged between 90 and 240 days was consistent (11.8 to 11.4 ova), whereas a steady decline was observed for mice between 270 days old (10.5 ova) and 360 days old (4.8 ova) . Ova were not recovered from oviducts of mice aged about 420 days. The average number of fertilized ova (2-cell stage) in mice between 90 and 210 days old showed no significant change (11.5 to 10. 3), whereas the number began to decrease in mice aged between 240 days (8.7 fertilized ova) and 330 days (2.5 fertilized ova) . No fertilized ova were recovered from the oviducts of mice around 360 days old. These findings demonstrate that the decline of reproductive activity is initially observed in the number of fertilized ova, followed by a decline in the number of ovulations and finally by loss of the estrous cycle.

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We previously reported that persistent estrus was induced in rats by PMSG administration at a specified period during the estrous cycle. This was again undertaken to clarify the characteristics of gonadotropin secretion during the persistent estrus induced by PMSG and to investigate the possibility of restoration to the normal cycle by various treatments. During the persistent estrus, the LH levels were lower and the FSH higher than in the controls. Following ovariectomy the LH and FSH secretions were delayed as a negative feedback response. When estradiol was implanted in these rats, LH was secreted as a low positive feedback response. Progesterone and hCG injections induced ovulation and then the restoration of the cycle. However, no copulation occurred when females so treated were paired with male rats for a week. Stimulation of the uterine cervix also failed to restore the normal cycle. Based on these results, the following conclusions were drawn : 1) during the persistent estrus, low negative and positive feedback responses are indicative of abnormal secretion of LH and FSH ; 2) there is an apparent dysfunction of the central nervous system in relation to mating ; and 3) the regular estrous cycle can be restored through appropriate treatments.

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Control litter data from reproduction toxicity studies in SD derived rats bred in our closed colony were investigated for historical changes, differences due to study design or generations, seasonal variations and effects of vehicle-treatment. The litter size did not change visibly during the entire 16-year period, but the number of live fetuses differed significantly between study designs or generations. The fetal weight gradually increased during these years. The malformation rate decreased, while the rate of 14 th ribs remained stable. There were no seasonal variations and no effects of vehicle-treatment.

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Strain differences among BALB/c, BDF₁, CDF₁, C3H/He, C57BL/6, DBA/2, ddy and ICR mice were investigated with respect to the ratios of histamine release from mouse peritoneal mast cells induced by compound 48/80, a Ca²⁺ dependent histamine releaser, and the Ca²⁺ ionophore A₂₃₁₈₇. The ratios of histamine release from mouse peritoneal mast cells induced by compound 48/80 were found to be high in BALB/c, ddY and ICR mice, but low in BDF₁, CDF₁, C3H/He, C57BL/6 and DBA/2 mice. Those induced by Ca²⁺ ionophore A₂₃₁₈₇ were high in BALB/c, BDF₁, CDF₁, C3H/He, DBA₂, ddy and ICR mice but low in C57 BL/6 mice. These results indicate that differences in histamine release from mouse peritoneal mast cells are strain dependent.

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The newly found mutant rat was characterized by small body size, shortened broad skull, slightly shortened limbs and flattened thorax due to shortened ribs and lordosis of thoracic vertebrae. Another distinctive feature of this mutant was polycystic kidneys. The reproductive ability was poor and it died at 6-11 months of age. These constitutional skeletal abnormalities and polycystic kidneys were found to be inherited by an autosomal recessive gene, to which the gene symbol, chi, was proposed.

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Antigenicity of penicillin G (PCG) was studied in guinea pigs. PCG 5 mg, 10 mg or 25 mg with Freund's complete adjuvant each on days 0, 7 and 21 was injected to a guinea pig : intramuscularly into both thighs and intracutaneously into four locations on the back. A remarkable antigenicity was induced in animals immunized with 25 mg although only low antigenicity in 5 mg and 10 mg. A maximum serum level of the antibody was observed about 2 weeks after last immunization and all of animals immunized with 25 mg died in active systemic anaphylaxis test. As mentioned above, it has been firstly demonstrated that a remarkable antigenicity of PCG can be produced by immunizing with a high dose of 25 mg in the guinea pig model in which PCG itself is used as immunogen.

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A total of 48 Donryu rats from 8 colonies of 5 lines were inoculated intravenously with 10⁷ cells of the ascites hepatoma strain AH 66. All the conventional rats of the lines D-1 and D-2 died between 9 and 15 days after inoculation with a good growth of implanted tumor cells. On the other hand, SPF rats of the lines A-1, B-1, C and E survived for 60 days showing complete rejection of the implanted tumor cells. A 50% of conventionalized ex-SPF rats of the lines A-2 and B-2, which had been once established as SPF colonies, and thereafter had been “re-conventionalized”, rejected the tumor cells. The present observations indicate that the microbial conditions of the animal, e. g. whether the animal is SPF or not, might play an important role in the growth of the implanted ascites hepatoma.

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Woodchuck (Marmots monax) is a very useful animal for studying human diseases such as endocrine, metabolic or cardiovascular diseases. It is regarded especially as the most excellent animal model for human hepatic cell cancer since woodchuck hepatitis virus has various biological characters similar to those of human hepatitis B virus. We have investigated in domesticating this wild animals as laboratory experimental animals and suceeded in breeding and rearing in our outdoor fascilities.

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Nuclear protein antigens to the antinuclear antibodies in serum of non-obese diabetic (NOD) mice were investigated. In the serum of diabetic NOD female mice (20 weeks old), the antinuclear antibodies were detected by indirect immunofluorescence assay using frozen sections of liver of C 57 BL/6 J or NOD mice as antigen. Nuclei were separated from the liver of C 57 BL/6 J mice and solubilized. Solubilized nuclear antigens were analyzed by SDS PAGE-Western immunoblotting techniques. Nuclear protein antigens with molecular weights of 26, 000, 32, 000 and 65, 000showed strongly positive reactions with the antinuclear antibodies in the serum of the NOD mouse.

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Angiotensin converting enzyme (ACE ; EC 3.4. 15. 1) activities were compared in plasma samples obtained from three species using a furanacryloyl tripeptide substrate. The enzyme activity observed in Wistar rat plasma was higher than the activities observed in the other two species. Using this substrate, human and canine plasma enzyme activities were similar-unlike published data where hippurylhistidyl-leucine was used as substrate.

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Spontaneous malignant fibrous histiocytoma (MFH) of the chest wall was found in a 10-year-old male Japanese white rabbit. Histologically, the MFH consisted mainly of areas of storiform, pleomorphic and myxoid patterns. Positive reactions for acid phosphatase (Ac-P), non-specific esterase (N-SE) and β-glucuronidase (β-GL) were demonstrated in fibroblast-like, histiocyte-like and giant cells. Moreover, a strongly positive fibronectin (FN) reaction was observed mainly in histiocyte-like and giant cells. In electron microscopy, tumor cells were composed morphologically of various types of cells such as fibroblast-like, histiocyte-like, undifferentiated and giant cells. This case was quite similar to those reported in man or other animals.

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