Progesterone level in the peripheral blood plasma of the cow, following intrauterine injec-tion of PGF_2α, was investigated.
Cows were injected with either a daily dose of 0.51.0 mg of PGF_2α for 2 consecutive days, or with a single dose of 36 mg of PGF_2α into the middle portion of uterine horn ipsilateral to the corpus luteum.
In 8 cows treated between Day 2 and Day 4 of the estrous cycle (Day 0=day of ovulation), 4 cows ovulated 814 days after the treatment. The cycle length of the remaining four cows was not changed. Blood level of progesterone following the treatment fluctuated in various patterns; i.e. (A) a pattern that was almost the similar as that found in the normal estrous cycle, (B) concentration of progesterone decreased temporarily after the treatment, then in-creased once again, and was followed by the similar pattern as like as (A), (C) progesterone level showed somewhat to rise temporarily after the treatment, but fell soon, (D) concentration of progesterone decreased temporarily after the treatment and then increased again, but was reduced right soon. Two cows treated for 2 consecutive days at Day 4 and Day 5 of the early luteal stage ovulated 4 days after the treatment. Blood progesterone level fell rapidly after the treatment, and became one-third of the initial level 24 hours after the second treament. Three cows treated singly between Day 9 and Day 11 of the mid luteal stage ovulated 4 days after the treatment. Blood progesterone tended to decrease as early as 3 hours after the treat-ment, and reached up to one-half to one-sixth of the initial levels 24 hours after the treatment. Two cows treated at Day 15 of the late luteal stage ovulated 4 and 6 days after the treatment, respectively. Concentration of progesterone was reduced to one-half in one cow, and in another, less than one-eighth of the initial levels 24 hours after the treatment.
The pattern of the blood progesterone level almost reflected the growing on regressive changes of the corpora lutea examined by rectal palpation.
These results showed that the luteolytic action of the treated PGF_2α in cows in the luteal stage, seemed to be very intense at 5 days after ovulation or thereafter, but on the contrary, in very early stage of it up to 4 days after ovulation, the action seemed to be rather weak or indistinct.

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The data used in this survey were obtained from the calving record of Japanese cattle in Akita Prefecture, during the years 196871.
The sex ratio of offsprings was 52.2±0.43 in the Japanese Black, 47.1±0.85 in the Japanese Brown and 51.2±1.23 in the Japanese Shorthorn. The total sex ratio combined these three breeds was 51.2±0.37. The ratio in the Brown breed was significantly lower than those in the other two breeds.
Of a total of 117 bulls, each produced 10 to 2, 484 offsprings, 13 showed a high (shifting to male) or low (shifting to female) sex ratio of their offsprings. Especially, two bulls of the Brown breed exhibited lower sex ratios (40.1±3.0 and 31.0±4.3).
In the Black and Brown breeds, the sex ratios in artificial insemination were lower than those in natural mating. The differences, however, were insignificant in both the breeds.
Seasonal difference in sex ratio was significant only in the Brown breed with a low ratio (43.5) in summer.

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The investigation was carried out on the ovulation rate, ovulation ratio, and transuterine migration of the fertilized ovum in the dog.
The number of ova shed was determined by counting the number of corpora lutea in the ovaries of 135 mongrel bitches 24 years of age weighing about 10 kg each and autopsied during a period from 1 to 70 days after ovulation.
The transuterine migration of the fertilized ovum was considered on the basis of the number of corpora lutea in both ovaries and that of fetuses in both uterine horns of 69 pregnant ones among the 135 bitches.
The results obtained are as follows.
1. Rate of ovulation (in 135 bitches).
The ovulation rate of the dog in each estrus was 6.0±1.7 ova on the average with a range from 2 to 12; that is, 2.9±1.4, ranging from 0 to 8, in the right ovary and 3.1±1.4, ranging from 0 to 6, in the left ovary.
No influence of the season on the ovulation rate could be found statistically.
In the ovulation ratio of the right to the left ovary, no significant difference was observed.
2. Transuterine migration of the fertilized ovum (in 69 pregnant bitches).
Two of the 69 pregnant bitches were discarded from the data, as it was conjectured that plural ova might have been ovulated from a single ovarian follicle. Monozygotic twins were observed in only one bitch.
The fertilization rate of all the experimental bitches was 88.8%.
The number of fetuses in both uterine horns was equal to that of corpora lutea in both ovaries in 39 bitches (58.2%). The number of fetuses was one smaller than that of corpora lutea in 17 bitches (25.4%), two in 5 bitches (7.5%), and three, four, and five in 2 bitches each (8.9%).
It was observed that the rate of transuterine migration of the fertilized ovum was 49.3% in 33 of 67 bitches; that is, almost half the bitches had one or two ova. The direction of migration of the fertilized ovum was from the side of the predominant ovary to the uterine horn on the opposite side in 30 of 33 bitches. The ovulation rate in both ovaries was the same as in the other 3 bitches. As the consequence of the migration, the distribution of fetuses showed a tendency to be epual in both uterine horns. More fetuses were found in the uterine horn on such side as having a smaller number of corpora lutea in 11 bitches (33.3%).

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[in Japanese]

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The authors presented a simple and effective radioimmunoassay method for bovine plasma androstenedione (4-A'dione), and an assay result of it during gestation period, around parturition, and in postpartum was reported.
The bovine plasma, 3.0 ml was extracted with methylene dichloride and was subjected to a Sephadex LH-20 micro-column for the separation. The effluent containing 4-A'dione was evaporated and was incubated with an anti-DHEA-3-O•CO-BSA mixture, consisted of 4-A'dione-1-2-3H, pepsin-treated human immune serum globulin, bovine albumin and the antibody. For separation of free from bound 4-A'dione, ammonium sulphate was applied. Each of the accuracy, precision, sensitivity, and specificity test for this assay method revealed quite satisfactory result. This type of method, by which certain two, three steroids can be assayed at one time by a single antiserum may be recommended for clinical diagnostic laboratory use; the authors reported previously¹⁾ such an assay method for the three estrogens in bovine plasma by using an estrone-17β-BSA antiserum.
The plasma 4-A'dione from the time of conception through to the 210th day of pregnancy showed about 100 to 200 pg/ml level, rather in simple pattern, but after the time the level elevated gradually and the maximum levels ranging from 900 to 1, 600 pg/ml were recorded near term. In postpartum, very low levels about 100 or less pg/ml were recorded on the day or the next day of parturition and this state almost continued for the following 6 weeks. The increase of the plasma 4-A'dione which occured in the last trimester seemed to precede the general increase of the plasma estrogens in the late gestation period. This finding and also the assay result of 4-A'dione and estrogens in the plasmas in the feto-placental unit, which had been collected by Caesarian section might suggest that on the 198th and 244th day of pregnancy, secretion of 4-A'dione depended mostly upon the maternal adrenal, though for further reliable elucidations, apparently more of the additional works must be requested.

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The progesterone level in the peripheral blood serum of 5 mares was determined by radioimmunoassay during the estrous cycle and gestation period.
Material and method: The 5 mares used in this study were 2 Percherons and 3 Bretons of the Tokachi Livestock-Breeding Station, Hokkaido. Sexual receptivity of them was checked every 2 to 3 days by a teaser stallion, and the internal genitalia was examined by rectum palpation. The blood samples were collected from jugular vein of the mares at intervals of 1 to 2 days during the follicular phase, and of 2 to 3 days during the luteal phase, further of 15 or 30 days during the gestation period. Serum samples (0.0250.2 ml) were extracted with ethyl ether, and assayed by the radioimmunoassay technique of MAKINe⁴. The assay water blank showed 00.013 ng, and the recovery rate was 75100 percent. The working range of the standard curve was from 0 to 1 ng of progesterone.
Result: Throughout the estrous cycle in non-pregnant mares the progesterone levels showed the lowest just at estrus (1.039, with a range of 0.3891.363 ng/ml at day of ovulation), and on the 5th day it commenced to rise. Thereafter, the increased value reached a peak of 9.454 (5.36114.961)ng/ml on the 10th day, then dropped rapidly towards the 20th day.
In pregnancy, progesterone on the 15th day had a mean value of 13.008 (7.00518.961) ng/ ml, higher than that on the 20th day (mean of 5.857, range 3.176 to 10.897 ng/ml). Between the 30th and the 105th day there was an indication of increase on progesterone levels. There-after, it commenced to drop rapidly to 6.350 (5.1287.573) ng/ml at the 120th day. A rise was observed in progesterone levels in these 5 mares, after each 150th day of gestation.
The highest mean level among the 5 mares was 22.548 (10.71641.080) ng/ml which obtained from the sample at each 225th day of gestation. However, after the 240th day these levels declined gradually.
The present report indicates that the plasma progesterone level assayed could be useful for pregnancy diagnosis in early gestation and also for judging the fetal well-being status during pregnancy.

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The effects of unilateral ovariectomy on late pregnancy were investigated in Wistar strain rats. Animals were kept under control lighting room (light went on 6:00, Light (12 hrs): Dark (12 hrs)). The operation of unilateral ovariectomy was performed under light ether antesthesia. The animals were semi-spayed on day 18 (9:0011:00), day 19("), day 20("), day 21 (9:0011:00 or 16:0017:00) and day 22 (9:0011:00 or 12:0013:00) of pregnancy, respectively. The observation was carried out for delivery at 9:00, 12:00, 15:00 and 18:00 on every day from day 21 of pregnancy. All animals were killed the next day of delivery and the oviducts and ovaries were removed. Those weights were recorded immediately.
In the rats operated on day 18 of pregnancy, majority of animals delivered in day 23 of pregnancy. But, 50 percent of animals operated on day 19 of pregnancy delivered before 9:00 on day 22 of pregnancy. Also, large number of animals operated on day 20 of pregnancy de-livered on day 22 of pregnancy. The delivery of animals operated in another day of pregnancy was similar to the control group.
The weight of the remained ovary did not significantly increase from day 18 to day 22 of pregnancy, but, compensatory ovulation had occurred in all of the operated animals at postpartum estrus. The number of ova in rats operated at day 22 of pregnancy decreased significantly from the group operated at day 21 (9:0011:00) of pregnancy (p<0.05). When rats were unilaterally ovariectomized on day 19 of pregnancy, ovarian weights increased significantly at 48 hrs after operation (p<0.05).
It is suggested from the present study that the role of ovary during the late pregnancy changed from day 19 of pregnancy and the number of follicles ovulated in post-partum estrus should be determined between the evening of day 21 and the next morning.

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