[in Japanese]

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In IVCS strain mice with 4 day cycle, kept under the 14L, 10D lighting schedule (light phase from 5:00 am. to 7:00 pm.), the ovulation took place regularlly on every 4 day in the period be-tween 1:00 am. and 4:00 am. of the day of vaginal estrus. And the release of an enough quantity of ovulating hormone (LH) to cause ovulation occured through the period from 1:00 pm. to 5:00 pm. on the day of vaginal proestrous. These data was quite comparable to the rats of Wistar-Imamichi strain under the same lighting schedule.
Although the rats showed the delay in ovulation for 24-hrs. by a single intraperitoneal injection of Nembutal (30 mg/kg) at 1:00 pm. of the proestrous day, the mice showed only a short delay (about 2 hrs.), but not 24-hrs-delay by the similar Nembutal treatment even with a much higher dosage (100 mg/kg). To extend duration of anesthetic state, additional injections of Nembutal (50 mg/kg/inj.) were performed at every 2 hrs., starting from 5:00 pm. of the proestrous day. In the mice given an additional injection at 5:00 pm., tubal ova were firstly found at 8:00 am. on the following morning. Unitil 9:00 pm. of the proestrous day when the last additional injection was made, with increase in numbers of additional injections, the delay in ovulation was proportionally prolonged for 2 hrs. per each injection. However, if the additional injections were extended to 11:00 pm. of the proestrous day or farther, the ovulation was completely blocked during the next day (the day of vaginal estrus), and showed 24-hrs-delay in ovulation.
A similar result was obtained with the atropine treatment. Namely, a single subcutaneous injection of atropine (500 mg/kg) at 1:00 pm. of the proestrous day resulted in ovulation for a several hrs. but not for 24 hrs.
It is assumed, therefore, that in the IVCS mice, a duration of the central excitation period, responsible for the LH-surge might last much longer than that in the rat.
A short delay in ovulation, however, was seemed to be present also in the rat under a certain condition. As was already pointed out by EVERETT et al. (1950), two succesive injections of Nembu-tal at 1:00 pm. on the second day into the rat which had been blocked its ovulation in the first day, needed to get the delay in ovulation for 2 days. In the condition, when the supplemental injection at 5:00 pm. of the second day was omitted, the ovulation was delayed for about 3 hrs.-from the proper time of ovulation.

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Ovulatory responses and fertility in the cow by injection of human chorionic gonadotrophin (HCG) for treating quiescent ovary have been reported by many workers. In these reports, however, a wide range of doses has been employed due to a lack of precise evidence on the optimum therapeutic doses of HCG. In small animals, such as mouse, rat and rabbit, it has been recognized that ovarian responses to exgenous gonadotrophin given by intravenous injection are more sensitive than those by intramuscular injection, and the preparations of HCG suspended in oil appear to be more effective than those dissolved in saline. These problems are important for the practical treatment of ovarian diseases in cattle, but have not been investigated. The objectives of the present study were (1) to examine the ovulatory responses of quiescent ovary in the cow by injecting different doses of two forms of HCG preparation-aqueous solution and oily suspension, at the same time to establish the minimum effective dose of HCG, and (2) to compare two routes of administration-intravenous and intramuscular injection-on the effectiveness for stimulating quiescent ovary.
A total of 338 Japanese beef cows was employed as materials. These animals were treated from 1963 to 1969 as outpatient cows of our laboratory or treated by ambulatory clinic. Ovaries were examined by rectal palpation once or twice a week prior to the treatment and diagnosed as ovarian quiescence because of abscence of corpus luteum and non or poor development of follicle. Aqueous solution or oily suspension of HCG at a dose level ranging from 250 M to 3, 000 IU were injected either intravenously or intramuscularly. Animals were divided randomly into three treatment groups: (1) aqueous solution-intravenous injection group, (2) aqueous solution-intramuscular injection group and (3) oily suspension-intramuscular injection group. Ovarian responses following the treatment were examined per rectum at an interval of 57 days, and occurrence of estrus was checked by owner. Certain animals in which ovulation was not induced primarily or ovarian condition relapsed into quiescence following the induction of ovulation were retreated with HCG, PMS (5001, 000 IU) or anterior pituitary gonadotrophins (Vetrophin 10 RU, Antrin 10 AU). The results obtained were summarized as follows:
(1) Within 57 days after HCG injection, ovulation was induced in 222 of 338 treated cows (65.7%) as shown in Table 1. By rectal palpation, 4 of them were known to be at postovulotory phase. The remaining 218 animals having medium sized corpora lutea which seemed to be passed for few days after the induced ovulation. These findings suggested that ovulation might be induced as early as within 23 days after HCG injection in most of the treated animals. Corpora lutea existing in 149 out of 218 animals were as soft and elastic as those in early luteal phase of normal estrous cycle, whereas corpora lutea existing in the remaining 69 animals were as hard as those in regressive phase. In 116 unovulatory cows, one or two follicles of various size including two cases of cystic follicles were found, except 26 animals in which no follicular development was palpated per rectum.
(2) Ovulation rate in the groups each received an injection of 250 IU, 500 750 IU, 1, 0001, 500 IU and 2, 0003, 000 IU of HCG was 26%, 75%, 67% and 76% respectively, as shown in Table 2. Among the three groups given more than 500 IU, the ovulation rate did not differ, and no difference was found between two forms of HCG preparation-aqueous solution and oily suspension. In the group given 250 IU of an aqueous solution, ovulation rates were little higher in animals injected intravenously than in those injected intramuscularly. However, they were distinctly lower than those in the groups given more than 500 IU.

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EVERETT (1948) demonstrated that in the 5-day cyclic rat, progesterone could induce ovulation 24 hours early when given nearly midday on the day of stage late V (the previous day of proestrus).
On the other hand, no advance of ovulation time is obtained in 4-day cyclic rats injected on 24 hours before the expected proestrus.
Authers tried to induce the ovulation by injection of progesterone on the day of stage V (diestrus) in the 4-day cyclic mice (IVCS strain) under the constant lighting from 5 a. m. to 7 p. m..
The results obtained are as follows:
1) In the 4-day cyclic mice, the single subcutaneous injection of progesterone (0.25 mg and 0.5 mg/mouse) at 7 p. m. on the day of stage V induced the ovulation on the next day as high ratio (Figs. 1, 2 and 5).
2) Induced ovulation by progesterone (0.5 mg/mouse) was observed 1315 hrs. after the injection, it was injected singly and subcutaneously at 7 p. m. on the day of stage V in 4-day cyclic mice (Fig. 4).
3) In the 4-day cyclic rats (Wistar-Imamichi strain), the subcutaneous single injection of progesterone (1.5 mg and 3 mg/rat) on the day of stage V did not cause induction of ovulation on the next day.

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The observation was made concerning the changes in the weight of ovaries and uterus and the development of ovarian follicles during the process of puberty in female Wistar rats.
Ovarian and uterine weights were measured from 15 age of days to puberty.
The ovaries were serially sectioned at 10μ and stained with hematoxylin-eosin to measure the development of ovarian follicles. All follicles with a diameter exceeding 100μ in the sections were scanned by using micrometer and the largest diameter in each follicle in which ova was observed within were used as a deta.
The results were as follows:
1) Weight of ovaries were rapidly increased from 19 days to 23 days, and since then the remarkable changes in the ovaries were not observed till near puberty. The condition in the ovarian development obtained here agreed with that of PMS-single treatment in immature rats previously reported in which the response of ovulation occurred at about 21 days and remained unchangeable in ovulation rate afterwards.
2) Ovaries and follicles were compared in grouping by the presence of the fluid within uterii (activated uterus) or not (non-activated uterus) near puberty.
The number of follicles exceeding 350μ were inclined to increase in activated uterus comparing: non-activated uterus although the difference between two groups was not so clear.
3) Weight of uterus was gradually developed from 15 days to near puberty and then increased' abruptly just before puberty (the first ovulation).

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