The present experiment was to make clear the histochemical natures and quantitative fluctuation of lipid droplets contained in the cytoplasm of Mongolian gerbil eggs from 1-cell to blastocyst stage. The activities of enzymes related to fat metabolism in the eggs were also investigated.
Different sizes of lipid droplets composed of lipoids were contained in the cytoplasm of Mongolian gerbil eggs. The droplets were abundant in the eggs from 1-cell to morula stage, but less in blastocysts. There could be found weak activities of α-glycerophosphate dehydrogenase and of β-hydroxybutyrate dehydrogenase and a strong activity of Δ⁵-3β-hydroxysteroid dehydrogenase (dehydroepiandrosterone as the substrate), but no non-specific esterase activity in the eggs through-out their early development.
From the results obtained here, it seems that Mongolian gerbil eggs may have abilities of fatty acid metabolism, steroid synthesis and interconversion between carbohydrates and lipids.

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Our previous studies revealed that ovulation took place between 1:00 h and 4:00 h on the day of estrus, and that an enough amount of ovulating hormone (OH) to induce ovulation was released before 17:00 h on the day of proestrus in the IVCS strain mouse with regular 4-day estrous cycle. Unlikely to the rats, only a short delay (about 2 hrs) in ovulation was caused by a single intrape-ritoneal injection of pentobarbital (Ptb ; 100 mg/kg) at 13:00 h of proestrous day in the mouse. Additional injections of Ptb (50 mg/kg/inj.) were performed every 2 hrs, starting from 17:00 h of proestrous day to extend the duration of anesthetic state. The delay in ovulation was prolonged for 2 hrs at each additional injection. When the additional Ptb injections were extended to 23:00 h of proestrous day, ovulation was delayed for 24 hrs as being reported in the rat.
In the present experiments, the effects of Ptb anesthesisa on changes of the pituitary OH content and the blood LH and FSH concentrations were investigated. The OH content was assayed by the extraovulation inducing potency, and the concentration of LH and FSH in serum was assayed by radioimmunoassay. In the normal cycle, the preovulatory sudden decrease of pituitary OH content was observed after 16:00 h and the blood LH concentration reached to the maximum level at 18:00 h on proertous day. Administration of Ptb at 13:00 h of proestrous day delayed the initiation of a decrcese of the pituitary OH content and an elevation of blood LH for 2-3 hours. Additional injections of Ptb at 17:00 h and 19:00 h of proestrous day resulted in a further delay in the release of OH; the sudden decrease of pituitary OH content started after 0:00 h of estrous day. However, if the additional Ptb was injected every 2 hour from 17:00 h to 23:00 h of proestrous day to maintain the anesthetic state for all the period, during which the preovulatory OH decrease in the pituitary lasted, the pituitary OH decrease and blood LH increase were not observed till 12:00 h of estrous day. The injection of Ptb at 18:00 h on proestrous day inhibited a further decrease of the pituitary OH content and this decrease was sustained till 0:00 h of estrous day in the normal cycle.
These result strongly suggest that the release of pituitary OH might require the continuous hypothalamic stimulation to the pituitary, rather than the triggering temporary stimulation, even after an enough amount of OH to cause the ovulation had been released. A duration of the hypo-thalamic excitation responsible for LH or OH release causing ovulation is assumed to last for very long time (for about 9 hours starting from 15:00 h) in the mouse compared with that in the rat.

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This study was undertaken to determine the survival of rabbit fertilized eggs after long term storage in liquid nitrogen. Eggs at the 8-16 cell stage were recovered at 45 h post coitum from mature Japanese White rabbits which had been induced to superovulate by treatment with FSH and HCG. The eggs were transferred into 0.1 ml PB1 supplemented with 50% rabbit serum contained in a 1 ml capacity plastic straw. The eggs were equilibrated with 1.5 M DMSO at 37°C for 15 min. The samples were cooled to -76°C at 1°C/min and transferred to liquid nitrogen vapor at -100°C for 5 min. The samples were finally transferred to liquid nitrogen at -196°C and preserved for 210, 4964 and 360463 days, respectively. The samples were warmed from -70°C to -10°C at approximately 4°C/min. At thawing, the DMSO in the medium was diluted in a step-wise manner with freezing medium at 37°C. The eggs were washed with Ringer's solution containing 20% rabbit serum and cultured for 45 days to determine the number of blastocysts developing in vitro. In the other experiments, the frozen-thawed eggs were transferred directly to the oviducts of synchronous pseudopregnant does which allowed to go to term. Statistical significance was determined by the X² test.
1. The proportions of eggs which appeared morphologically normal after thawing of eggs preserved for 4964 and 360463 days were 82.5 and 71.8%. These figures were not signficantly different from that obtained after thawing of eggs preserved for 210 days, 82.1%. 2. The proportions of eggs developed into blastocysts after culture of frozen-thawed eggs preserved for 4964 and 360463 days were 77.8 and 62.5%. These were not significantly different from that obtained after culture of eggs preserved for 210 days, 63.4%. 3. The proportions of eggs developed into live young after transfer of eggs preserved for 4964 days and 360463 days, 18.5 and 17.9%, were comparable to that obtained after transfer of eggs preserved for 210 days, 16.7%.

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Induction of estrus and ovulation by systemic injection of Prostaglandin F_2α (PGF_2α) or its two analogues (ONO-1045 and 1108) was demonstrated in 44 Holstein cows. The injection was given once intramuscularly or intravenously at the luteal phase in each cow. The ovulation was judged by the rectal examination, and assay of sex steroids was performed by radioimmunological method (RIA).
(1) By a single injection of 20 mg to 30 mg dose of PGF_2α, estrus and ovulation were induced in all cases (6/6), but in cases given the dose of 6 mg to 12 mg, the ovulation rate remained low (5/9). These ovulations occured at 45 to 150 h (aver. 92.8) after injection of PGF_2α. The external signs of estrus induced, such as vaginal mucus flow, swollen labia, opening and swelling of uterine orifice, congested vaginal mucosa and mounting behavior and so forth, were recognized fairly or well on the 2nd or 3rd day after the injection in ovulated cases and continued for 2 to 4 days, but those signs were feeble in unovulated group. Strong contraction of uterus and decline of corpus luteum were recognized on the 2nd day after the injection.
(2) With 0.5 mg and 0.75 mg dose of injection of PGF_2α analogue, ONO-1045, the ovulation occured in 2/4 and 3/4 of the treated cows respectively, and with 1.0 mg dose of it, all 8 cows showed ovulation. The time of ovulation in this group was recognized at 64 to 137 (aver. 96.2 h) after the injection. The external estrous signs were recognized well in ovulated cases.
(3) By a single injection of 0.5 mg of PGF_2α analogue, ONO-1108, all 13 cows treated showed ovulation. The time of ovulation was recognized at 68 to 158 h (aver. 99.2 h) after the injection and the external estrous signs were slightly weak than those induced by the former two materials.
(4) Progesterone levels in the peripheral blood decreased drastically after the injection of PGF_2α or the two PG analogues which were accompanying the increase of estradio1-17β levels in most of ovulated cases.

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Prostaglandin F_2α (PGF_2α) and estradiol benzoate (E2B) were used for synchronization of estrus and the fertility at the first synchronized estrus after the treatment was investigated in the grazing cow.
A total of 31 cows (Holstein) in the functional luteal phase of the estrous cycle were alloted to two experimental groups; i, e. Group A (15 cows) received an intramuscular (i. m.) injection with 15 mg of PGF_2α and Group B (16 cows) received the simultaneous i. m. injection with 15 mg of PGF_2α and 0.5 mg of E₂B. Cows in both groups were observed for standing estrus every 6 h during the period of 24 to 96 h after the treatment and were inseminated 10 to 24 h after being detected in estrus. The time of ovulation was examined every 6 to 12 h, and diagnosis of pregnancy was made between 46 and 48 days after the insemination by rectal palpation.
Number of cows showed estrus within 96 h after the treatment in Groups A and B were 13 cows (86.7%) and 15 cows (93.8%), respectively. However, estrus occurred in 13 cows (86.7%) during 3784 h of the post treatment period in Group A, and in 14 cows (87.5%) during 3160 h of the post treatment period in Group B. The average interval±S. D. from the treatment to estrus for the cows showing estrus within 96 h after the treatment in Groups A and B were 58.6±12.0 h and 45.6±14.0 h respectively. Ovulation occured in 10 cows (66.7%) during the period of 7396 h after the treatment in Group A, in 13 cows (81.3%) during the period of 6184 h after the treat-ment in Group B. The average interval±S. D. form the treatment to ovulation for the cows ovulated within 120 h after the treatment in Groups A and B were 89.6±11.8 h and 71.9±8.8 h, respectively. The corpora lutea which developed after the ovulation at the synchronized estrus were normal 1114 days after the inseintion in the most of cows in both groups, but those of 2 cows in Group B were detected small in size by rectal palpation. Conception rate by the insemination during 49120 h of the post treatment period was not different in both groups, 53.9% (7 of 13 cows) for Group A and 56.3% (9 of 16 cows) for group B. However, of 16 cows in Group B, 14 cows were inseminated during the period of 4972 h after the treatment and 9 cows (64.3%) conceived.
These results indicated that the interval from the treatment to estrus and ovulation could be reduced, and the occurrence of estrus and ovulation were synchronized precisely by the simultaneous i. m. injection of PGF_2α and the lower dose of E₂B, and E_2αB had no adverse effect on conception rate. Further investigation in large number of cows are needed to be sure whether or not the simultaneous injection of E2B with PGF_2α will result in normal conception rate.

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Litter size in utero was estimated with an ultrasonic Doppler apparatus ("Heart-tone" USD-1, Aloka Co. Ltd., Tokyo) in 16 pregnant sows inciuding three different breeds. In 15 out of 16 sows, experimental period was from 80 to 114 days of pregnancy, while in the remaining one sow experiments were undertaken during 58 to 107 days of pregnancy. Each experiment was carried out non-surgically at a sleeping position with neither restraint nor anaesthesia.
The results obtained were as follows.
1) In 5 out of 20 experiments, the estimated litter size was in accord with the actual number farrowed at parturition. In the remaining 15 experiments, however, errors of the estimation ranged from -5 to +3 piglets.
2) Cases of which the errors were less than ±1, ±2 and ±3 piglets, were 9 out of 20 (45%), 14 out of 20 (70%) and 17 out of 20 (85%) experiments, respectively.
3) The accuracy of estimation of the litter size tended to be higher after 91 days of pregnancy than before 90 days (P <0.10), and it tended to be low when the actual number of fetuses was more than 10, as compared with less than 9 piglets.
4) No harmful effects were observed in both fetuses and dams by the ultrasonic treatment used in this study.

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The amount of glycogen and the activities of phosphorylase and UDPG-glycogen transferase were histochemically examined in Mongolian gerbil eggs throughout the stages from 1-cell to the blasto-cyst. The eggs were collected under following conditions: 7 h after ovulation for 1-cell eggs, 31 h for 2-cell eggs, 79 h for 4-cell eggs, 103 h for 8-cell eggs, 127 h for morulae, and 151 h for blasto-cysts. For the demonstration of glycogen, eggs were treated with the periodic acid-Schiff with or without a preceding salivary test. The activity of phosphorylase was demonstrated by a modified TAKEUCHI and KURIAKI method and UDPG-glycogen transferase by the TAKEUCHI and GLENNER method.
Glycogen granules were abundant in the eggs throughout the stages from 1-cell to 8-cell, but slight in the morula and blastocyst. Phosphorylase activity was moderate in the 1-cell eggs, weak at the stages from 2-cell to 8-cell, but none in the morula and blastocyst. UDPG-glycogen trans-ferase activity was dot demonstrated in the eggs at any developmental stage.
From the results obtained here, Mongolian gerbil eggs seem to metabolize glycogen at the stages from 1-cell to 8-cell, but do not at the stages of morula and blastocyst. In other hand, the eggs are unlikely to synthesize glycogen throughout their developmental stages.

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An experiment was conducted to determine whether the administration of progesterone or medroxyprogesterone acetate (MPA) affects the recovery of the eggs from the vagina and the subsequent fertility and implantations in the rabbit. The does were divided into 6 groups according to dose and time of administration of the gestagen. Vaginal washings for recovery of eggs were carried out twice per day for 7 days following the mating.
Subcutaneous administration of 2.5 mg progesterone on day -2, -1 and 0 gave rise to a maximal recovery of vaginal eggs (40.8 ±14.8% in group 2), and intramuscular injection of 25 mg progesterone on day 0 (the day of mating) led to the lowest egg recovery (6.9 ±4.7% in group 5, p <0.01). The earliest eggs recovered from the vagina were obtained at the first vaginal washings 24 hours after mating in groups 1, 2, 3 and 6. And 80% in group 1, 96% in group 2, 77% in group 3, 71% in group 4, 0% in group 5 and 78% in group 6 of all eggs, which were collected vaginally for 7 days following the mating, were recovered by 72 hours after mating.
Implantation of eggs in the treated rabbits were examined on day 9 by laparotomy, and 24.3±15.7% and 55.6±16.1% of eggs were found to be implanted in group 4 and group 5, respectively. No implantations occurred in any other groups. Normal-looking cleaved or fertilized eggs were recovered only in group 3 and group 4; one 2-cell egg and two 4-cell eggs in group 3, one 32-cell egg, two morulae and one blastocyst in group 4. The proportions of unfertilized eggs were 80% for group 1, 88% for group 2, 46% for group 3, 50% for group 4, 20% for group 5, and 96% for group 6.
The results in the present study indicated that administration of progesterone or MPA greatly affected the fertilization and the egg transport in the rabbit.

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It has been reported that acrosome reaction in rat spermatozoa does not occur before their pene-tration of cumulus oophorus and zona pellucida. This study was conducted to examine whether any morphological change in acrosome could be observed in rat spermatozoa recovered from uterus.
Transmission and scanning electron microscopical observations showed that more than fifty percent of spermatozoa had partly or perfectly dispersed plasma membrane of acrosomal region when reco-vered from uterus 6 h after mating.
The most spermatozoa recovered from uterus 12 h after mating, lost plasma membrane, which apparently led to release of acrosomal substances. The anterior region of sperm head swelled and extremely changed. In some spermatozoa, the nuclear membrane was partly dispersed.

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