It has been shown that HCG stimulates the ovary to secrete progestin and estrogen in normal and hypophysectomized rat, judging from the decidual reaction in traumatized uterine horn and the cornification of vaginal wall.
In this study, ovary-stimulating effects of HCG were examined by means of the maintenance of pregnancy in hypophysectomized rat during various stages in the first half of pregnancy, and the effect of estrogen on maintenance of pregnancy in hypophysectomized pregnant rat was also examined with estrone.
Injections of hormones were continued following hypophysectomy through 9 days of gestation, subcutaneously, once daily (day 0 was the day of sperm detection in the vaginal smear in the morning, on which day fertilization occurs).
Animals were sacrificed at 20 days of gestation (in this experiments the Sprague Dawley rats were employed).
When hypophysectomy was performed on 9, 8 and 7 days of gestation, pregnancy was maintained in 100 % of animals in all groups by injections of 4 IU/day of HCG.
In the groups in which animals were hypophysectomized on 5 and 4 days of gestation, no effect was obtained by injections of 4 IU/day of HCG to maintain the pregnancy, but, when injections of 40 IU/day of HCG were continued, high ratios of pregnancy were maintaened in both groups.
The injections of estrone to the rat hypophysectomized on 9, 8 and 7 days of gestation effected also the maintenance of pregnancy in 17%, 88% (with 0.5 and 1.0 μg/day of estrone) 29%, 71% (with 1.0 and 2.0 μg/day) 44%, 50% (with 1. 0 and 4.0 μg/day) of animals in respective groups.
In the rat hypophysectomized on 6 days of gestation, no effect was obtained by the injections of estrone to maintain the pregnancy.
Thus, it was supposed that the maintenance of pregnancy in the rat which was hypophysectomized in nearer days to the end of mid-gestation and injected with 4 IU/day of HCG might be attributed to the synergestic action of estrogen and small amount of progestin rather than sufficiently secreted progestin from the ovaries stimulated by HCG.

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Quantitative test for the determination of individual PMSG in the pregnant mare is one of the important tools for pregnancy diagnosis. The present paper reports on the quantitative assay of standard PMSG and pregnant mare sera using antibody agar plate method. The research using antibody agar plate were performed according to modification of Fafey's technique³⁾. With this technique, specific anti-PMSG immuno rabbit serum (IgG) is mixed uniformly in an agar plate. Antigen containing solutions are placed in small antigen wells cut in the agar. A concentric ring of antigen-antibody reaction forms around the antigen well. By graphically comparing the ring diameters with those of appropriate standard, the concentration of the test sera of pregnant mares can be determined. The mean PMSG levels in 30 pregnant mare sera were found to be minimum 60 IU/ml and maximum 210 IU/ml from pregnant mare sera. However, for definite evalution of the samples, more experimental data will be needed. In this study, by means of the antibody agar plate technique, it was possible to use the anti-PMSG serum for an immunoassay for qua, titative analysis.

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The Serotest, immunological pregnancy tests of mares, was studied on 282 sera of 196 mares and 3 stallions at Tokachi and Hidaka districts in Hokkaido, from May to September in 1967.
Results obtained may be summarized as follows;
1. Accuracy of tests on nonpregnant mares and stallions was 100.0 %, but on pregnant mares, it varied with gestation periods. That is, at 1 to 29, 30 to 44, 45 to 80, 81 to 120 and more than 121 days after the last service, accuracy of tests was 6.3, 51.7, 96.6, 40.0 and 40.0 % respectively.
2. Positive reactions with this test were first observed at 3946 days and continued to 76126 days of gestation through long-term observations of 5 pregnant mares.
3. Accuracy of tests on light horses was seemed to be higher than that of half blood or heavy horses.
4. Eight mares out of 160 were suspected to have aborted through this tests and biological assays.

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Nobunaga et al. observed that the interval between the ovulation induced by HCG injection at 4 PM on the day of diestrous stage and the first spontaneous ovulation occurring thereafter was 72 hours.
This report deals with the interval between the ovulation induced by a single intravenous injection of HCG (injection was done at 0 AM, 9 AM, or 4 PM on a day during stage IV, V, or I respectively) and the first spontaneous ovulation taking place thereafter.
1) In a few of the animals injected with HCG at 0 AM on the day during stages IV and V, first spontaneous ovulation after the ovulation induced by HCG took place 76 hours after the HCG injection (or 64 hours after the induced ovulation).
In the most of them, however, those ovulations occurred 100 hours after the HCG injection (or 88 hours after the induced ovulation).
In animals injected with HCG at 0 AM on the day of stage I, the time interval between the injection and first spontaneous ovulation after the induced ovulation was 100 hours (or 88 hours after the induced ovulation).
2) In a few of the animals injected with HCG at 9 AM on the days during stages IV and V, first spontaneous ovulation were observed to have possibly taken place 67 hours after the HCG injection (or 55 hours after the induced ovulation).
In the most of them, however, those ovulations were seen 91 hours after the HCG injection (or 79 hours after the induced ovulation).
In animals injected with HCG at 9 AM on the day of stage I, those ovulations was occurred about 115 hours after the HCG injection (or 103 hours after the induced ovulation).
This time interval is longer than 91 hours when was injected at 9 AM on the day during stages IV and V.
3) In animals injected with HCG at 4 PM on the day during stages IV and V, first spontaneous ovulations were discoverd about 84 hours after injection (or 72 hours after the induced ovulations), without exception.
In animals injected with HCG at 4 PM on the day of stage I, first spontaneous ovulations took place 108 hours after the HCG ihjection (or 96 hours after the induced ovulation).
Namely, the time interval between the ovulation induced by HCG injection at 4 PM on the day of stage I and the first spontaneous ovulation thereafter was 96 hours, when was longer than 72 hours, or the time interval between the ovulation induced by HCG injection at 4 PM on the day during stages IV and V, and the next spontaneous ovulation.
4) Accordingly, after the ovulation induced by HCG injection some time between 0 AM and 4 PM on the day of stage IV, first spontaneous ovulations were discoverd on the morning of the same day in the most of the animals injected.
After HCG injection performed some time between 0 AM and 4 PM on the day of stage V, first spontaneous ovulations were observed on the morning of the same day.
In a few of the animals injected with HCG at 0 AM on the day of stage V, next spontaneous ovulation took place on the morning of the same day one's due to the cases of HCG injection on the day of stage IV.
In the case of HCG injection at 0 AM on the day of stage I, next spontaneous ovulation occurred on the next morning of the day one's due to the case of HCG injection at 4 PM on the day stage V.
In the case of HCG injection at 9 AM and 4 PM on the day of stage I, next spontaneous ovulations were delayed and took place on the next morning of the day of first spontaneous ovulation when HCG was injected at 0 AM in stage V.
5) The fiirst spontaneous ovulation after the induced ovulation was observed over a period from 0 to 4 AM in all the cases.
6) In all the cases of first spontaneous ovulation after the induced ovulation, an ovulation-blokade by pentobarbital (Nembutal) anesthesia was seen when injected with Nembutal intraperitoneally (30 mg/kg) at 0 PM on the day before the first spontaneous ovulation.
It was not seen however, when injected with Nembutal at 4 PM on the day before the ovulation.

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[in Japanese]

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