Review: Exploration of placentation from human beings to ocean-living species.

This review covers four topics. 1) Placental pathology in Himalayan mountain people. To determine morphological changes of the placenta at high altitude, pathological examination was made of 1000 Himalayan placentas obtained in Nepal and Tibet and the results compared with Japanese placentas delivered at sea level. Characteristic findings in the placental villi of the Himalayan group included high incidences of villous chorangiosis and chorangioma. These processes were clarified by ultrastructural observation. 2) Placentation in Sirenians. The giant Takikawa sea cow, which lived 5 million years ago, was discovered on Hokkaido, Japan. It was an ancestor of the dugong as well as the manatees. Sirenia, the sea cow group, shares a common ancestor with Proboscidea, the elephants, even though they now inhabit quite different environments. A comparison was made of their zonary endothelial type of placentation. 3) Placentation in sharks and rays. The remarkable placentation of hammerhead sharks and manta rays is described. 4) Placentation in the Antarctic minke whale. Placental tissue samples of this whale were obtained from the Japan Institute of Cetacean Research. In an ultrastructural study of the utero-placental junction, microfilamental processes of the allantochorionic zone and crypt formation were visualized.

Plasma and pituitary concentrations of gonadotropins (FSH and LH) in minke whales (Balaenoptera acutorostrata) during the feeding season.

This study investigated plasma and pituitary concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and steroid hormones (progesterone: P4, testosterone:T, estradiol-17beta: E2) by enzyme-immunoassay (EIA) in minke whales (Balaenoptera acutorostrata) captured during the feeding season (December to March) in the Antarctic Ocean. Plasma FSH and LH levels in female minke whales were higher (P <0.05) than in male whales. Although the pituitary weight was not significantly different between male and female whales, pituitary FSH and LH levels were higher in females than in males (P<0.01) and mature whales than immature whales (P<0.05). Plasma levels of FSH, T and E2 were not significantly different between immature and mature male whales, but plasma LH and pituitary FSH and LH levels were higher (P<0.05) in mature than in immature whales. In both immature and mature whales regardless of gender, pituitary FSH and LH levels were correlated significantly (r=0.69: P<0.01). In mature male whales, plasma T and E2 levels (r=0.60: P<0.01), and testis weight and plasma T levels (r=0.46: P <0.05) were correlated. In immature female whales, plasma FSH and LH levels were highly correlated (r=0.68: P<0.001), but were not for mature female whales. The results show that gender and maturity influence gonadal and pituitary function of minke whales during the feeding season.

In vitro maturation and ultrastructural observation of cryopreserved minke whale (Balaenoptera acutorostrata) follicular oocytes.

Minke whale (Balaenoptera acutorostrata) follicular oocytes were cryopreserved by a slow-step freezing procedure using ethylene glycol. The morphologically viable proportion of postthawed minke whale follicular oocytes was 39.7%. The maturity of the animals (immature and mature whales) or the presence or absence of cumulus cells (CC) did not affect the proportion of morphologically viable oocytes. Postthawed oocytes were examined for nuclear status after in vitro maturation. The presence of CC (29.1%) significantly enhanced (P < 0.05) the proportion of oocytes at metaphase I/anaphase I/telophase I stages compared to results with the absence of CC (13.5%). A total of 4 of 194 postthawed oocytes matured to the second metaphase stage after culture for 5.5 days with or without CC. The cryopreserved immature oocytes obtained from immature and mature whales were processed to examine the ultrastructure by transmission electron microscopy. Varying ultrastructural damage to the cytoplasm was observed as a result of the cryopreservation procedures. These results show that 20-30% of cryopreserved minke whale follicular oocytes can resume meiosis in vitro, but damage induced by the freezing and thawing procedures was observed.

Factors affecting in vitro maturation of minke whale (Balaenoptera acutorostrata) follicular oocytes.

Factors affecting in vitro maturation (IVM) of minke whale (Balaenopetra acutorostrata) follicular oocytes were investigated. In experiment 1, recovery rates for oocytes from follicles of different sizes (small, 1-5 mm; medium, 6-10 mm; large, > or = 11 mm) were similar in both immature (54.7%) and mature (53.5%) females, and the follicular sizes did not affect recovery rate. Approximately half the oocytes recovered from small follicles in immature (55.5%) and mature (52.1%) whales were surrounded by at least a few layers of cumulus cells. Before culture, 71.7% and 61.2% of oocytes from immature and mature whales, respectively, were at the germinal vesicle stage. For IVM, effects of serum type, hormones, and additional cumulus cells (experiment 2) and effects of culture durations (24-120 h, experiment 3) were investigated. The three factors investigated in experiment 2 did not affect maturation rates. TCM199 supplemented with fetal whale serum, hormones, and additional cumulus cells showed the highest rate (21.6%) of matured oocytes and resulted in a significant difference from the rate in medium with only fetal calf serum added (6.6%). The first oocyte with an extruded polar body was observed after 84 h of culture. The maximum rate (27.3%) of matured oocytes was obtained by 96 h of culture, but there was no significant difference in the proportions of matured oocytes between 90 and 120 h in culture. These results indicate that in vitro nuclear maturation of immature follicular oocytes in minke whales can be induced.

Effect of human leukemia inhibitory factor on in vitro development of IVF-derived bovine morulae and blastocysts.

This study was conducted to investigate whether human leukemia inhibitory factor (hLIF) improves the subsequent development of IVF-derived bovine morulae and blastocysts. To obtain IVF-derived bovine morulae, ova were matured and fertilized in vitro and cultured in 0.5 ml of synthetic oviduct fluid (SOF) medium supplemented with 10% human serum (HS) for 5 d at 39 degrees C under a gas atmosphere of 5% CO(2), 5% O(2), 90% N(2). Morulae and early blastocysts at Day 5 of culture were cultured in 0.5 ml of SOF medium with or without 5000 U/ml recombinant hLIF for 2 or 3 d (2 groups). To investigate the effect of addition of hLIF on the subsequent development of morulae, SOF medium was supplemented with 8 mg/ml BSA instead of HS. To test whether hLIF affects the subsequent development of IVF-derived bovine blastocysts, only good blastocysts that developed from SOF medium with or without hLIF at Days 7 and 8 of culture were frozen by a conventinal slow freezing method and again cultured in SOF medium with or without the addition of hLIF for 3 d after thawing (4 groups). Survival of frozen-thawed bovine embryos was evaluated for re-expansion and hatching of blastocysts during 3 d of culture. There was no significant difference in the developmental rate of Day 5 embryos to blastocysts between those cultured with (47.8%) and without (47.6%) addition of hLIF. However, the addition of hLIF before freezing significantly increased the hatching rate of IVF-derived bovine morulae (P < 0.05), whereas addition of hLIF after thawing did not increase the subsequent development of blastocysts. These results suggest that hLIF added at the Day 5 morula stage may contribute to bovine embryonic development through the hatching process.