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[in Japanese]

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The early stage of fertilization and implantation were studied in rats following gonadotrophin treatment. A total of 433 rats were kept under artificial lighting conditions (night controlled from midnight to 10 a.m. for 10 hours), and injected with human chorionic gonadotrophin (HCG) 12 hours before an estimated ovulation (at 8 p.m., or 4 hours before the beginning of artificial night), together with or without a priming injection of pregnant mare serum gonadotrophin (PMS) at 54 hours interval. The results obtained are as follows.
1) When the oviducts were treated with cold-shock (ice) in superovulated rats for a minute beginning at 12 (24), 15 (27), 18 (30), 21 (33) and 24 (36) hours after an estimated ovulation (or after HCG injection in parentheses), the second polar body was formed in 94.2, 94.0, 86.8, 60.2 and 33.7 % of ova, respectively.
2) When rats were allowed to copulate after treatment with 25 I.U. of HCG, 30 I.U. of PMS and 50 I.U. HCG and 50 I.U. of PMS and 50 I.U. of HCG, 75.8% (257 of 339 ova), 49.4% (496/1005), and 47.2% (727/1541) of the ova, respectively, were found to have been penetrated by the sperm, 6 hours after copulation. In other words, the second polar body was found to be present in 44.0, 28.4, and 27.8% of the sperm-penetrated ova, respectively. The percentage of sperm-penetrated ova was 68.8% (38.2% with the second polar body) in the untreated control rats.
3) When rats were examined at autopsy 9 days after copulation, the percentage of rats which. had implantation sites after treatment with 25 I.U. of HCG, 50 I.U. of HCG, 10 I.U. of PMS and 25 I.U. of HCG, 10 I.U. of PMS and 50 I.U. of HCG, 30 I.U. of FMS and 50 I.U. of HCG and no treatment (control rats) was 84.0% (42 of 50 rats), 52.0% (26/50), 72.0% (36/50), 60.0% (30/50), 0 % (0/40) and 95.2% (40/42), respectively. The average number of implanted embryos per head was 11.6 (7-17), 12.2 (10-16), 12.3 (8-16), 11.5 (7-16), and 11.8 (7-16) in female rats treated with 25 I.U.of HCG, 50 I.U. of HCG, 10 I.U. of PMS and 25 I.U. of HCG, 10 I.U. of PMS and 50 I.U. of HCG, and no gonadotrophic hormones (control rats), respectively.
4) The results mentioned above seem to suggest that the treatment of gonadotrophin may have negative effects on the fertilization and implantation of ova in adult rats.

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It is well known that hypophysectomy interrupts pregnancy in the rat when performed during the first half of pregnancy. In such animals, the pregnancy is maintained by human chorionic gonadotrophin (HCG) substituted for pituitary luteotrophin.
This study was carried out to examine for the effect of pregnant mare's serum gonadotrophin (PMSG) on maintenance of pregnancy in the rat hypophysectomized before establishment of placenta, and the effect of estrogen on maintenance of pregnancy with estrone, since PMSG stimulates estro-gen production in the ovary.
Hormones were injected subcutaneously, once daily, following hypophysectomy through day 10 of gestation (day 0 was the day of sperm detection in the vaginal smear, in the morning). Animals were sacrificed on day 20 of gestation (in this experiment, the Wistar-Imamichi rats were employed).
No effect of maintaining pregnancy was obtained by daily injections of 5, 10 and 50 I.U. of PMSG in animals hypophysectomized on days 4 and 5 of gestation. However, when animals were hypophysectomized on days 6, 7, 8 and 9 the pregnancy was maintained in various ratios by injec-tions of 1, 5 and 10 I.U. of PMSG. In the groups hypophysectomized on days 7, 8 or 9 of gestation, the pregnancy was maintained in 88% of animals, by daily injections of 5 or 10 I.U. of PMSG, but a deleterious effect of PMSG was found, when daily injections of 10 or 20 I.U. were continued to animals hypophysectomized on the same days described above.
The daily injections of 8.0 μg. of estrone maintained the pregnancy in 50 and 57% of animals hypophysectomized on days 8 and 9 of gestation, however, no effect was obtained in animals hypophysectomized on day 7, as far as daily injections of 1.016.0 μg. of estrone were continued.
This report demonstrated that it is possible for PMSG to maintain the pregnancy in rats hypophysectomized on and after day 6 of coitus, however, it is not clear whether PMSG acts directly on the corpus luteum to secretes a certain amount of progestin.

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In order to facilitate the sexing of rabbit embryo, the appearance of sex chromatin and the localization of sex chromatin in blastocyst were investigated.
The results are summarized as follows:
1. Sex chromatin in fertilized ova was not observed from 1 to 4 days of age. It seems to be due to absent of resting-stage nuclei.
2. Sex chromatin positive nuclei were observed 35.4 % or 51.2 % in blastocysts of 5 or 6 days of age, respectively.
3. In 5 ages eggs, the localization of sex chromatin positive nuclei was observed, namely, the section of A (inner cell mass) was higher than the section of D (the area oppositing to inner cell mass).

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[in Japanese]

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