The time of production of the uterine luteolytic factor, which is considered to be derived from the endometrium following induced inflammation, was investigated in the cow.
By histological examination, it was found that inflammatory damage on the endometrium indu-ced by a single intrauterine injection of Lugol's solution (I : KI : H₂O= 1 : 2 : 300) was repaired almost completely, 34 days after the treatment. To prevent the repair of the inflammatory damage to the endometrium, cows were treated successively with Lugol's solution twice a day at inrervals of 12 hours from Day 3, 5, or 7 to 9 of the estrous cycle (Day 0 =day of ovulation). The mean cycle length of these cows was reduced to 17.018.0 days. These cycle lengths were almost equal to those of the cow treated singly on Day 9 of the estrous cycle. When the successive dsily intra-uterine treatments from Day 3 to 9 of the estrous cycle were interrupted for 3 days, begining the day folliwing the first day of the treatment, and hence the reparation of the endometrium was allowed during this period, the mean cycle length was reduced to 10.0 days. This cycle length was almost equal to that of the cow treated singly on Day 3 of the estrous cycle. While, when the treatments were interrupted for 1 or 2 days, the mean cycle length became 16.5 days. This cycle length was almost equal to that of the cows treated successively. When cows were treated once on Day 13 of the estrous cycle, and retreated 4 to 8 days later, their cycle lengths were pro-longed in all cases which were retreated 4 days later and in half of them which were retreated 6 days later. In the remaining half of the cows in the latter group, and in all cows retreated 8 days after the first treatment, the cycle lengths remained normal.
These results indicated that the luteolytic factor might be derived from the endometrium dur-ing the reprartory process of inflammatory damages, or after completing it, and produced 34 days after the induction of the endometrial inflammation in the cow during the early luteal stage. The time of psoduction of this factor in the cow, during the late luteal stage, seemed to be some what delayed. Ferthermore, the luteolytic factor produced following the endometrial inflammation, should have an intensive character which could regress the corpus luteum within a priod as short as approximately one day.

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Recently, ovulation inducing and luteineizing properties of FSH were demonstrated by IMAMICHI et al. Applying the ovulation inducing property of FSH, KATO (1971), KASAZIMA & KAWADA (1972)and INANIWA & KAWAGUCHI (1973) obtained successful results in the treament of ovarian follicularcysts in dairy cows.
In this study, we carried out an experimental treatment of ovarian follicular cysts and ovu-lation failures in light breed mares with highly purified FSH (Antrin, Toshiba Pharmaceutical Co.)by intramuscular injection.
The following results were obtained.
1. Sixteen mares with ovarian follicular cysts were treated with 2040 Armour Units (A.U.)of FSH. The cystic follicles were mostly ruptured, within 8.5 days (ranged 321 days) after thetreatment. All treated mares were cured. Eight of 12 mares (66.7%) conceived and the remaining4 were not bred or not certified for conception.
2. Thirty mares with ovulation failure were injected with 1040 A. U. of FSH. Ovulationwas induced within 2.6 days (ranged 24 days) in 28 mares (93.3%) and ovulation rate in eachdose group was 71.4% (10 A. U.), 100% (20 A. U.) and 100% (40 A. U.), respectively. Nineteen outof 26 mares (73.1%) conceived. The remaining two were not certified for conception.
3. It was demonstrated that FSH had an action to induce ovulation in mares as in rats. Inthe cases of ovulation failure, an intramuscular injection of 10 A. U. of FSH could induce ovulation, though we recommended to inject 20 A. U. of FSH for obtaining more definite effect. For treatmentof mares with ovarian follicular cyst, being not so severe, sufficient effect to induce ovulation maybe expected with intramuscular injection of 20 A. U. of FSH.

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Fifty-four light breed mares suffering from difficulties of follicular development were treatedwith gonadotrophin given intramuscularly alone or in combination with intrauterine infusion. xperimental animals were allotted to four groups, each group being contained two subgroups ofanimals treated with gonadotrophin alone and animals received combined treatment. Since both group 3 and 4 contained a few animals and showed poor efficacy, the comparison of efficacy between simple onadotrophin treatment and combined treatment was done only for the group 1 and 2.
1. On the whole, the gonadotrophin treatment with or without uterine treatment yielded thefollowing results.
Mares injected with the combination of 5, 000 I. U. of PMS and 5, 000 I. U. of HCG (group 1), and 5, 000 I. U. of PMS and 2, 500 I. U. of HCG in oil suspension (group 2), were induced estrus in32 of 35 mares (91.4%) and 9 of 14 (64.3%) respectively. Mares treated with a single injection of 5, 000 I. U. of PMS (group 3) and 2, 500 I. U. of HCG in oil suspension (group 4) decame estrus in 1 of 2 (50%) and 1 of 3 (33.3%) respectively.
2. It is suggested that mares with difficulties of follicular development may be expected toshow normal estrus by a single intramuscular injection of 5, 000 I. U. of PMS and 5, 000 I. U. of HCG, or by additional injection of the same dose (or double doses) given 1014 days after theinitial administration when it is not effective.
3. In group 1 and 2, 21 of 24 mares (87.5%) with difficulties of follicular development in which ovaries were atrophic or corpus luteum-like structure persisted in ovaries, and did not show estroussigns, estrus occured by the PMS-HCG treatment and intrauterine infusion of gel-like substancethat was given into the uterus simultaneously or 10 to 14 days prior to gonadotrophin administr-ation.
In the similar cases in which non or poor development of follicle in normal sized ovary wasdetectable by rectal palpation and showed non or feeble estrus, 20 of 25 mares (80.0%) were inducedestrus with the gonadotrophin therapy.

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Prostaglandin F_2α (PGF_2α) and pregnant mare serum gonadotropin (PMS) were used for estrous synchronization in beef cows, and the fertility at the first estrus after the treatment was investigated.
A total of 40 beef cows (24 Japanese Shorthorn and 16 Japanese Black Cattle) in the luteal stage of the estrous cycle were alloted to two experimental groups; i. e. Group A consisting of 15 cows, which were given a single intrauterine injection of 6 mg of PGF_2α, and Group B consisting of 25 cows, which were given the PGF_2α treatment and an intramuscular injection of 500 IU of PMS. PGF_2α dissolved either in 2.5 ml or 5.0 ml of sterile saline was injected into the middle portion of the uterine horn, ipsilateral to the corpus luteum through the cervix, by using a metal catheter. PMS was injected immediately after the PGF_2α treatment. Estrus was checked every 4 hours, du-ring the period 24 to 96 hours after the treatment, and the ovaries of the cows exhibiting estrus were examined per rectum. Each cow that came into estrus was inseminated with frozen semen, and diagnosis of pregnancy was made between 40 to 60 days later, by rectal palpation.
Estrus occurred in 8 (53.3 %) of 15 cows in Group A, during 6172 hours of the post treatment period, and in 11 (44.0%) of 25 cows in Group B, during 4960 hours of the post treatment period. Number of cows which came into estrus within 60 hours after the treatment in Groups A and B, were 3 (20.0%) and 13 (52.0%), respectively. However, the cows which showed estrus during 3796 hours of the post treatment period in Groups A and B, were 12 (80.0%) and 20 (80.0%), respectively. The remaining 8 cows in both groups exhibited estrus between 5 and 15 days after the treatment. Occurrence of estrus was somewhat later in the cow receiving PGF_2α dissolved in 5.0 ml saline, than in that receiving PGF_2α dissolved in 2.5 ml saline. The average number of follicles larger than 8 mm in diameter in the cow of Groups A and B, which came into estrus during 3796 hours of the post treatment period, were 1.2 (12) and 1.5 (13), respeectively. One ovulation occurred in all cows of both groups, except one animal in Group B, which ovulated two follicles. In the cows that had been inseminated either once or twice, or not inseminated during the period prior to the experiment, their conception rates were 75.0% (9 of 12 cows) in Group A, and 62.5% (5 of 8 cows) in Group B by the service during 3-5 days of the post treatment period, whereas, the cow which had received more than three inseminations, conceived in 33.3% (4 of 12 cows).
These results indicated, that the time interval between treatment and the occurrence of estrus could be reduced by the simultaneous injection of PGF_2α and the lower dose of PMS. However, there was no marked differences between the cow treated with PGF_2α alone, and the cow injected with PMS immediately after the PGF_2α treatment, in (a) the number of cows which came into estrus during the period of 96 hours after the treatment, (b) the number of grown follicles and ovulations, and (c) the conception rates at the first synchronized estrus.

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The minimum effective dose of prostaglandin F_2α (PGF_2α) for regressing the corpus luteum and the effectiveness of PGF_2α for estrous synchronization were investigated in the cow, by injecting it intramuscularly.
Seven cows with mean weight of 421 kg (ranging from 420 to 490 kg, except one weighing 280 kg) were injected intramuscularly with PGF_2α, at mid luteal stage (714 days after ovulation) of the estrous cycle. Either 6-30 mg of PGF_2α dissolved in distilled water, or 810 mg suspended in propylene glycol, was used. The corpora lutea regressed rapidly during the period of 13 days after the treatment. Ovulation occurred in 46 days, mainly in 4 days, after the treatment. Ho wever, in cows that were injected with 5 mg of PGF_2α dissolved in distilled water, and 4-6 mg of PGF_2α suspended in propylene glycol, the corpora lutea did not regress, or regressed slightly, during the period of 14 days after the treatment, and began to grow again thereafter. There were no marked changes in the treatment cycle length of these cows.
These results indicated that the minimum effective dose of PGF_2α for regressing the corpus lutetm of the cow was 6 mg, when it was dissolved in distilled water, and 8 mg when it was suspended in propylene glycol. There is no great difference in the minimum effective dose, between both vehicles.
In 17 heifers (10 Holstein and 7 Japanese Short Horn), weighing an average of 337 kg (ranging from 275 kg to 413 kg), those were injected intramuscularly with 10 mg of PGF_2α dissolved in distilled water, estrus occurred in 12 heifers (70.6 %) during the period of 2-5 days after the treatment. In 3 of the remaining 5 heifers, corpora lutea regressed during the period of 2-4 days after the treatment, and there followed follicular development. However, onset of estrus and ovulation in these heifers, were delayed until 7-9 days after the treatment. Corpora lutea of 2 other heifers did not regress following the treatment.
The results indicated that the single intramuscular injection of 10 mg of PGF_2α was applicable to synchronization of estrus and ovulation in the cow.

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The authors previously reported^{1, 2)} that the post-partum ovulation in the rats occurred from 12 hrs to 30 hrs after delivery, and then, in the rats delivered from 10:00 to 20:00 that ovulation was blocked with Nembutal administration (subcutaneously) between delivery time and 2 hrs after delivery.
This experiment was carried out to determine the follicular development and oocyte maturation with special reference to the time of the release of ovulating hormone (OH) in normal cyclic, HCG treated and post-partum rats. Adult virgin female rats of the Wistar strain were kept under 12 hrs light and 12 hrs darkness (light on 6:00, light off 18:00) and 25°C room. Vaginal smears were taken daily and only animals which had shown more than 3 times consecutive 4-days estrous cycle were used.
OH potency of the anterior pituitary was expressed as number of rats ovulating per the animals injected with test sample on the 2nd day of diestrus (D₂).
In proestrous rats, OH potency of the anterior pituitary at 11:00, 13:00 and 14:00 was 6/6, 4/5 and 4/5, respectively, but the potency began to decrease from 15:00 (2/5), and then it disappeared at 19:00 (4/5).The changes of the nucleus of the oocyte began from 2 hrs after the time expected for the release of OH, and the ovulation points were observed at 12 hrs after OH release (correspond to 2:00 on the day of estrus). The intraperitoneal administration of Nembutal at 13:30 on proestrus did not decrease in OH potency and it also prevented the maturation division in the change of oocyte maturation.
In the rats delivered between 10:00 and 20:00, OH potency at 0, 1, 2, 4 and 6 hrs after delivery was 10/10, 3/3, 4/7, 3/5 and 0/5, respectively.
The breakdown of germinal vesicle was first observed 4 hrs after delivery.
It is suggested that only brief exposure of the follicles to OH is essential for the initiation of maturation division of the oocyte.
In estrous cycle, the follicles over 550 μin diameter had suddenly developed during the time between D₂ and proestrus. Also, larger follicles than 550 p in pre-or post-partum rats grew rapidly from the 22nd day of pregnancy to delivery time.
It was found that the follicular development and the oocyte maturation in post-partum pro-ceeded quite similar to that in estrous cycle.
Further, process of the oocyte maturation in the rat treated with HCG on D₂ was similar to that in proestrus of the normal cyclic rat.
The time of OH release could be estimated from the number of normal follicles (over 550 μ) showing normal maturation changes.
It is suggested that OH may be released 2 to 4 hrs after delivery which has occurred between 10:00 and 20:00 in the rats.

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In order to investigate the cellular elements of vaginal smear of the bitch in the estrous cycle, 32 mongrel bitches 24 years of age weighing about 10 kg each were observed during approximately 130 days from 3 months before proestrus to 10 days after estrus.
Vaginal smears were collected every day using a metal spatula at any time between 8 and 9 a. m. Various cell components contained in the vaginal smear were divided into 4 groups; -(non), ± (a few), + (moderate), and ?? (numerous), on the basis of the number of cells which appeared.
A smear was air-dried quickly, fixed in 90 per cent methanol and stained with Giemsa solution.
The results obtained are as follows.
1. Pre-proestrus.
Leucocytes, epithelial cells and cornified epithelial cells were always low in count in the cons-tituents of smear. In two-thirds of the animals the latter two increased slightly in count over a period from 1 to 1.5 months before vulval bleeding could be recongnized by the naked eye.
Erythrocytes were observed in smear for only several days from 40 to 50 days before vulval bleeding. The consistent appearance of erythrocytes began to be observed in smear 7 days on the average (020 days) before vulval bleeding.
2. Proestrus (317 days, or 8.4 days on the average).
Cornified epithelial cells increased gradually. Epithelial cells and leucocytes were hardly found in numerous animals in the late stage of this phase. Erythrocytes increased in count in the early phase, but decreased gradually in the latter half of this phase.
3. Estrus (520 days, or 11.1 days on the avarage).
Epithelial cells and leucocytes began to appear in the vaginal smear again in late estrus.
Cornified epithelial cells decreased moderately in about half of the animals in the latter half of this phase.
In some animals, erythrocytes stained indistinctly were absent from smear in this phase.
4. Metestrus.
A few epithelial cells and cornfied epithelial cells were found in vaginal smears during post-estrus. Leucocytes increased temporarily in about half of the animals. Erythrocytes appeared moderately in smears in about two-thirds of the animals studied. As mentioned above, it was found that various cell elements changed rhythmically in the vagi-nal smear in relation to the ovarian cycle in numerous bitches. Four bitches (13%), however, showed no periodical changes. So that, it was difficult to decide the estrous cycle accurately by examining vaginal smears alone.

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