In an attempt to investigate the possibilities of uterine invasion by Escherichia coli and the development of endometritis, experimental studies were carried out in 216 normal healthy bitches in the different stages of the estrous cycle, employing the modified endotracheal tube for inoculation of the organisms into the canine vagina. The inoculated E. coli originated from a severe clinical case of canine pyometra and showed a serological type of 025, H+, and K-.
The results obtained were as follows:
1. Regardless of the stage of the estrous cycle, E. coli injected into vagina could be present in the uterus of 9.1 to 100% of the bitches within 30 minutes after inoculation. The highest incidence of uterine invasion by inoculated E. coli and is longest retention time in the uterus occurred in the proestrous + estrous stage, and several uteri of this stage showed an appearance of acute endometritis.
2. At 5 days after inoculation, neither E. coli nor inflammatory process could already be demonstrated in the uterus of all the bitches with the proestrous + etsrous and postpartum stages of the estrous cycle.
3. The bitches inoculating E. coli before copulation brought about the normal process of pregnancy, and also no evidence of endometritis or placentitis was found at 30 days after inoculation.
4. It is suggested from these results that the settling of E. coli seldom occurs in the uterus of normal healthy bitches in the different stages of the estrous cycle, although the uterus can easily be invaded by organisms injected into the canine vagina.

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Efficacy of progesterone pre-treatments in combination with 'ram effect' on estrus induction and lambing rate in Suffolk ewes was investigated during the late anestrous season. In Trial 1, effects of a single i.m. injection of 20 mg progesterone followed by ram introduction or a single injection of 100 μg synthetic gonadotropin releasing hormone were examined. The proportions of estrous ewes during the first 14 days after ram introduction were significantly larger in the progesterone pre-treated group than in control, but not between 15 and 28 days. No significant difference was found in either lambing rates or prolificacy. An injection of gonadotropin releasing hormone is as effective as the use of 'ram effect' for the lambing rate and prolificacy. In Trial 2, methods of progesterone pre-treatment (a single injection or vagina sponge) before ram introduction were investigated. No significant difference was found between the two groups in the proportions of estrous ewes, lambing rates or prolificacy except a significantly higher proportion of estrous ewes during the first 2 weeks after ram introduction in the group treated with progesterone. However, the use of 'ram effect' combined with progesterone pre-treatment was less effective in inducing out-of-seasonal reproductive activities than the conventional method using progesterone-impregnated vaginal sponge and pregnant mare's serum gonadotropin.

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This experiment was conducted to examine the effects of parity, body weight changes, milk yield and suckling stimulation on Japanese Black cows using 66 postpartum first ovulation records. The multiple regression equations using backward procedure for estimating the recurrence interval of postpartum first ovulation are as follows.
Y=37.157-1.842X₁-0.036X₃-0.112X₄+2.001X₅+0.521X₆
+0.103X₈+0.364(X₁-3.7)²-0.001(X₇-100.1)²
(Adjusted R²=63.8%)
where, Y: Days from calving to first ovulation, X₁: Parity, X₃: Body weight just after calving (kg), X₄: Body weight loss from just after calving to 30 days postpartum (kg), X₅: Milk yield at 30 days postpartum (kg/day), X₆: Suckling events at 30 days postpartum (times/day), X₇: Total suckling time at 30 days postpartum (min /day), X₈: Frequency of suckling interval time (%).
The relative importance of the variables' order was X₁>X₅>X₄>X₃>X₇>X₈>X₆. In this analysis, increasing of milk yield and the number of suckling events indicated inhibitory effects on the occurrence of first ovulation, and body weight changes affected as well as the effects of parity, milk yield and suckling stimulation.

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Prostaglandin (PG) E₂ and its dehydrogenase (PGDH) activity were histo-chemically detected in mouse blastocysts developed from 2-cell embryos in media con-taining graded concentrations of indomethacin (IM).
Fluorescence that showed the presence of PGE₂ was observed in all blastocysts developed in the IM-free medium. Its intensity in the blastocysts developed in media containing 100 nM to 100 μM gradually and significantly diminished as the concentrations of IM became higher; fluorescence wholly lacked in some blastocysts developed in media containing 10μM and 100μM.
Diformazan granules representing PGDH activity were observed in all blastocysts developed in the IM-free medium. The depression of PGDH activity was more significant when the blastocysts were developed in media containing higher concentrations of IM, and no activity was detected in those embryos developed in the medium containing 100 μM.
These results indicate that both synthesis and metabolism of PGE₂ in mouse blastocysts are suppressed by IM at the concentrations higher than 100 nM.

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Washed ejaculated goat and boar spermatozoa were preincubated in isolatedrat uteri, open test tubes and sealed glass tubes with or without rat uterine fluid. The acrosome reaction was evaluated by a triple-stain technique and a hamster test. Goat and boar spermatozoa underwent the acrosome reaction during preincubation in the isolated rat uteri and sealed tubes. In the open test tubes, the acrosome reaction did not occur in the goat, but did in the boar. The addition of rat uterine fluid to the medium accelerated the onset of the acrosome reaction in goat spermatozoa preincubated in sealed tubes and in boar spermatozoa in open test tubes. Increasing sperm concentration in the suspension promoted the acrosome reaction. These results indicated that the acrosome reaction of boar spermatozoa could be induced by preincubation in open test tubes, and preincubation in isolated rat uteri and sealed tubes was effective for inducing the acrosome reaction of both goat and boar spermatozoa, and that the supplemented rat uterine fluid in the medium shortened the time required for inducing the acrosome reaction. Possibly, the difference in the effect of preincubation in open test tubes between these two species may correspond to the difference in the mechanism to acquire energy between them, and one of the factors in isolated rat uteri to induce the reaction may be a lack of oxygen.

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A linear-array ultrasound scanner with a 5 MHz rectal transducer wasevaluated for diagnostic studies of twin pregnancy and embryonic mortality in 52 Japanese Black cattle received bilateral egg transfer. Observations for pregnancy and fetus survival were monitored every 10 days from 27 to 107 days (estrus=day 0) of gestation. Accurate twin pregnancy diagnosis could be made on day 27 of gestation. The cows with non-echogenic areas in the both uterine horns on day 27 were diagnosed as twin pregnancy, since these non-echogenic areas observed only in cows later confirmed to be pregnant of twin embryos day 37 or later. Both and single embryonic losses in twin pregnant cows were also clearly detectable by using ultrasonography. Pregnancy rate in bilaterally embryo transferred cows decreased gradually from 59.6% on day 27 to 46.2% on day 67. Twinning rate of pregnant cows was as high as 80% by day 37, but it fell down to 54.2% on days 77-107. In 25 twin pregnant cows on day 27, loss of single embryo occurred in 8 cows and loss of two embryos occurred in 4 cows by day 67. The greater part of embryonic mortality and loss of single embryo happened between 38-57 days. Furthermore, the most of these embryonic losses (85.7%) occurred in the uterine horn contralateral to the side of persistent corpus luteum.

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A double-antibody enzyme immunoassay (EIA) for the determining GnRH in bovine plasma was studied. Antiserum raised against [Glu¹]-GnRH-rabbit serum albumin conjugate in a male horse was used. Enzyme-labelled antigens were prepared by coupling synthetic GnRH with horseradish peroxidase using bis-diazotized benzidine. GnRH analogues and fragment of GnRH were tested for cross-reactivity in the EIA system. These results suggested that the C-terminus of GnRH molecule plays more important role in antigen-antibody binding than the N-terminus of it.
Plasma specimens were extracted with acid-methanol. Process standard curve was suitable for plasma assay. The sensitivity of this EIA system was as little as 50 pg/tube of GnRH. After intravenous injection of 200 μg of synthetic GnRH in 2 steers, plasma concentrations of GnRH were determined in this EIA system. The levels abruptly increased just after injection and decreased thereafter.

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Concerning effects of post-ovulatory anti-LH serum (aLH) administration on luteal progesterone (P) secretion and reactivity to prolactin (PRL), comparisons were made between 4-and 5-day cycles. Plasma P declined by 6:00 hr on diestrus (D) in control 4-day cycling rats and by 18:00 hr on day D in control 5-day cycling rats. Daily injections of aLH from 8:00 hr on estrus (E) in 4-day cycles did not alter P secretion. However, aLH injections from 8:00 hr on metestrus (M) prolonged P secretion up to 18:00 hr on day D, while aLH injections from 19:00 hr on day M failed to prolong P secretion. In 5-day cycles, aLH injections from 8:00 hr on day E or 19:00 hr on day M prolonged P secretion. Control 4-day cycling rats responded to PRL injections from 8:00 hr on day M with elevated P secretion and persistent leukocytic vaginal smears for 9-10 days, but they failed to respond to PRL injections from 19:00 hr on day D. Control 5-day cycling rats also failed to respond to PRL injections from 19:00 hr on day D. Injections of aLH from 8:00 hr on day M in 4-day cycles preserved the full luteal re-activity at 19:00 hr on day D. The aLH injections from 19:00 hr on day M maintained the full luteal reactivity at 19:00 hr on day D in 5-day cycles, but not in 4-day cycles. At 18:00 hr on day D, changes in the fine structure of the lutein cells from control and aLH-treated 4-day cycling rats were correlated to those in plasma P levels. These results indicate (1) tonic LH levels on day E of 4-day cycles "enhance" luteal P secretion, (2) tonic levels of LH secreted on day M suppress luteal function, which has a structural basis, (3) the suppressive effect is imposed at least 11 hr later in 5-day cycles than in 4-day cycles.

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Present investigation was carried out to examine whether the loss of zona pellucida occurs in unfertilized eggs of mice during the estrous cycle and pseudopregnancy. A total of 1271 eggs were recovered from the oviducts and uterus by flushing with modified K.R.B. solution between 10:00 h on day 3 and 10:00 h on day 4 of the estrous cycle at 3 h intervals (day 1= day of estrus). Also 190 eggs were collected between at 5:00 h on the 4th day of pseudopregnancy and at 3:00 h on the following day at 2 h intervals. The percentage of unfertilized eggs without the zona pellucida were 2% (25/1271) in cyclic mice and 0.5% (1/190) in pseudopregnant mice.

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