Concentrations of inhibin in peripheral blood were determined in cattle treated with porcine follicle-stimulating hormone (FSH). Changes in plasma concentrations of FSH, luteinizing hormone (LH), estradiol and progesterone were also examined. These results were compared with hormonal profiles in the intact estrous cycle prior to FSH treatment of the same cows. Plasma levels of estradiol before ovulation and of progesterone after ovulation during the period of treatment with porcine FSH were much higher than those in the intact cycle. Concentrations of plasma inhibin rose promptly after injections of porcine FSH and maintained high levels for a longer period than estradiol after the LH surge. Changes in plasma concentrations of inhibin were not correlated to those of progesterone in superovulating cattle. In the superovulating animals, peaks of the preovulatory FSH surge were suppressed to 70.4% of the intact cycle, though LH peaks were not significantly suppressed. These results indicate that high levels of inhibin after treatment with porcine FSH may be involved in a partial suppression of the preovulatory surge of FSH in superovulating cattle. These findings also suggest that unovulated follicles maintain the ability to secrete inhibin and that the corpus luteum in superovulating cattle is not the active source of inhibin secretion.

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Ultrastructural changes of mouse oocytes obtained from the different ages were compared. (1) In oocytes stocked in primordial follicles, microvilli and desmosomes decreased with the advancement of age of animals; materials collected were 2-day-, 20-day-, 60 to 90-day-and 360 to 390-day-old. In the oocytes of 360 to 390-day-old animals, there appeared shallow depressions of the nuclear membrane. Mitochondria were of an even size, but some of them were markedly large in the oocytes of 20-day-and 60 to 90-day-old animals. Mitochondrial cristae were lamellar or vesicular; the lamellar cristae decreased and the vesicular ones increased with the advancement of age. Golgi apparatuses, smooth-surfaced endoplasmic reticula and ribosomes tended to decrease with aging. (2) In oocytes immediately after ovulation, zonae pellucidae were homogeneous in those of 30-day-old animals, but they partly showed a feature of rough fiber-network in some oocytes of 60 to 90-day-and 180 to 210-day-old animals. Irregularly shaped mitochondria became smaller with the advancement of age, and the number of their cristae also gradually decreased. Cortical granules were few in the oocytes of 30-day-old animals, but were numerous in those after 60-day-old animals. Fibrous strands were more abundant in the oocytes of 180 to 210-day-old animals than in those of the younger ones.

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Ovariectomy postpones the onset of the decline in the milk production which occurs at late or prolonged stage of lactation in intact rats. To determine whether this effect of ovariectomy on milk production is mediated by prolactin or corticosterone secretion, the effect of ovariectomy on secretory responses of prolactin and corticosterone to suckling by pups was examined at various stages of normal and prolonged lactation. Lactating rats were ovariectomized on day 1 (day 0= the day of parturition) and litter size was adjusted to 8 on day 2. Pups were replaced with those aged 6-8 days at every 8th day from day 16 onwards. Mothers were allowed to suckle for 30 min after 4-hr separation from pups, and were bled for 2hr at 10-30 min intervals from the onset of suckling on days 8, 16, 24, 32 and 40. Plasma prolactin and corticosterone concentrations elevated in response to suckling on days 8 and 16 both in sham-operated and ovariectomized rats. The response of these hormones almost disappeared on day 24 onward. Ovariectomy did not affect the secretory response of prolactin and corticosterone to suckling from days 16 to 40 except that the level of prolactin response was lowered on day 8. These results suggest that neither prolactin nor corticosterone mediates the effect of ovariectomy on the decrease in the milk production which occurs around the end of normal lactation.

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Changes in the food intake and the body composition of normal and prolonged lactating rats were examined to know the mechanism(s) of nutrient partition during lactation. Fat reserve in the body of mother rats depleted progressively from day 0 to day 24 of lactation, but restored during the prolonged lactation. Protein reserve decreased abruptly between day 16 and 24 and rose thereafter. Both of the fat and the protein losses occurred at quite the same rate in normal lactating and prolonged lactating mothers. A simple input-output relation between food intake and milk production could not explain the results. Some changes in the homeorhetic control of nutrient flow in maternal body occurred at the time corresponding to the end of normal lactation.

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Estrus was induced by three treatments and their utility for embryo transfer was investigated. The treatments were as follows: Treatment I, PMSG-hCG treatment on the day of weaning (23 sows); Treatment II, PMSG-hCG treatment after injection of PGF₂α analogue (26 pregnant gilts); Treatment III, PMSG-hCG treatment after Altrenogest administration (23 cyclic gilts). Estrus was detected by checking twice with mature boars. A high proportion of animals showed estrus on day 0 (day 0: the day of hCG injection) to day 1 for the Treatment I and II, and on day 1 for: III. The incidence of cystic ovaries was observed in three pigs after the Treatment I. The pigs exhibited estrus were inseminated 2-3 times, and then the recovery of embryos was carried out on day 5-8. The proportion of normal embryos in the Treatment I, II and III were 81.8%, 81.0% and 52.5% respectively (Treatment I & II vs III: p<0.05). Thirteen to 22 normal embryos were transferred to recipients synchronized by the three treatments. The conception rate was lower in the Treatment III than the Treatment I, but the difference was not statistically significant. In conclusion, the Treatment II is suitable for estrus synchronization in gilts, whereas the utility of the Treatment III appears to be so far questionable. Although the incidence of cystic ovary was observed, the Treatment I is available for sows.

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Thirty five and 40 bovine embryos collected on day 7 of pregnancy were suspended into 1.4M glycerol and 1.6M 1, 2-propanediol solutions employed as cryoprotectants respectively. They were loaded into 0.25ml plastic straws with 0, 0.2, 0.4 and 0.8M sucrose in PBS. Those straws were cooled directly to 0°C in the cooling chamber, seeded at -6°C, cooled to-30°C at a rate of 0.3°C/min and then stored in liquid nitrogen. The straws were thawed in a water bath at 30°C, followed by zero-step dillution of cryoprotectant. The recovered embroyos were cultured with Ham's F-10 medium supplemented with 10% calf serum to evaluate the survival rate from their developments in vitro. With 0. 0.2, 0.4 and 0.8M sucrose in PBS, the survival rates of embryos were 83, 91, 91 and 100% for 1.6M 1, 2-propanediol and 0, 0, 83 and 90% for 1.4M grycerol, respectively. This study indicates that, when 1.6M 1, 2-propanediol solution is employed as a cryoprotectant, a high survival of bovine embryos after being frozen-thawed can be obtained without using sucrose solution for the dilution of cryoprotectant.

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Bovine follicular oocytes (oocytes-cumulus complexes) were matured, fertilized and developed in vitro utilizing a co-culture system with bovine cumulus cells. Oocytes from individual cows were cultured separately throughout the experiment.
Experimental groups were classified into three groups based on the number of oocytes collected from individual cows: Group 1, n ?? 20; Group 2, 21 ?? n ?? 30; Group 3, n ?? 31.
Although there were no significant differences in the development rates of oocytes among 3 groups, percentage of embryos developed to blastocyst stage in Group 3 tended to be higher than those of Groups 1 and 2 (14.3% vs 9.0% and 7.9%). There were considerable differences in the rates of development to blastocyst stage within the same group (Group 1, 043.8%; Group 2, 026.1%; Group 3, 025.0%). The number of blastocysts obtained from individual cows after in vitro culture varied from 0 to 11. (mean=3). The result of this study indicates that oocytes from individual cows have different ability of development in vitro.

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Two-cell rat embryos were exposed to one or a train of two electric pulses with different field strengths and durations. It was difficult to induce blastomere fusion with a field strength of 1.0 kV/cm of 50μs duration: only 1 (7%) of 15 treated embryos fused after either one or a train of two pulses. The rate of fusion reached a maximum (80-100%) with 1.5-2.0 kV/cm and with 100-200μs duration. While the fusion rates were improved when the embryos were treated with a train of two pulses of 1.0 kV/cm for 100-200 μs, little effect was observed with 1.5 and 2.0 kV/cm. With 1.0 and 1.5 kV/cm, the fusion times were shortened when the embryos were exposed to a train of two pulses of 50 to 200 μs duration; no marked shortening of the time by the increased number of pulses was observed with 2.0 kV/cm. When fused embryos were transferred into pseudopregnant females and recovered 3 days later, 15 (83%), 12 (80%) and 9 (64%) of recovered embryos, which were originally submitted to 1.0, 1.5 and 2.0 kV/cm of field strengths each for 150 μs, respectively, had developed to the morula-blastocyst stage. There were no significant differences in the rates of development among these different field strengths.

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The maternal vascular architecture of the dog girdle placenta from 30 to 63 (full term) days of pregnancy was investigated on corrosion casts by means of scanning electron microscopy.
Each zone in the zonary girdle of the dog placenta was supplied by the radial arteries which were emitted from the arcuate arteries. The radial arteries branched three to five times giving off arterioles in the middle of the labyrinth which reached the allantochorionic side of the labyrinth. Subsequently, the arterioles emitted capillaries which formed a network in the labyrinthine zone. The capillary network was oriented in feto-maternal direction. Venules originating from the network converged into the radial veins near the junctional zone. Finally the radial veins joined the arcuate veins.
At 30 days of pregnancy, the capillary network of the labyrinthine zone had a basic architecture. It developed remarkably in quantity from 30 to 45 days of pregnancy, with prominent development from 40 to 45 days. Though the network continuously developed from 45 days onward, the rate of development was lower than before. In the placenta of 45 days, the capillary network of the labyrinthine zone completed its development as well as its arrangement.

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The failure of one-cell embryos of non-inbred mouse (CD-1) to develop in vitro (2-cellblock) was examined by culture in a chemically defined (WM-HEPES) medium containing activin A (erythroid differentiation factor, EDF). Successful development of one-cell embryos into 4-cell embryos or morulae in the WM-HEPES medium was significantly enhanced in the presence of activin A. More than 83% of one-cell embryos developed into 4-cell embryos in the presence of 1.0 ng/ml activin A during the 2-cell stage in contrast with 15% in control cultures without activin A. This activity was most evident at the mid-2-cell stage. Eight of 40 embryos treated with activin A were delivered alive from the 2 recipient mothers 18 days later. This capacity of activin A to stimulate early embryonal development was also demonstrated in 8-cell embryos, the proportion of embryos developing to the morula stage being significantly promoted. Our results demonstrate the capacity of activin A to release the 2-cell block and to stimulate early embryonal development in vitro.

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