Methods are described for the preparation and maintenance of ovine trophoblast in monolayer cell culture, and for the preparation of cultured cells for ultrastructural examination. Monolayers grown from dispersed and explanted primary cultures were maintained in consecutive subcultures for periods of 12 to 16 weeks. Towards the end of the first week of incubation high concentrations as the cultured developed. In the second week of incubation small binucleate cells were seen in cultures prepared for electron microscopy. By the 14th day larger binucleate cells were visible at the outer edges of the developing monolayer, and by the third to fourth week 25 to 40 per cent of the cells in culture were in binucleate form. Mature binucleate cells seeded in primary dispersed cultures did not survive beyond the 14th day. The result suggest that (a) the binucleate cells which first appear in monolayers of cultured trophoblast during the second week of incubation are formed by nuclear division of uninucleate cells and not from mature binucleate cells seeded in primary dispersed cultures; and (b) there may be a correlation between the numbers of binucleate cells present in the monolayer and the rate of production of ovine placental lactogen. Monolayer cultures of sheep trophoblast may well provide a useful and relatively inexpensive experimental system for the study of binucleate cells and the mechanisms of placental hormone production.

Animals↗

PubMedDate not supplied

Ultrastructural observations on the placenta of the alpaca (Lama pacos).

The alpaca is one of the four South American species of the family Camelidae. Its placenta, like that of other camelids, is diffuse and epitheliochorial in type. The chorionic epithelium is thrown into unbranched villi or folds which are closely apposed to corresponding undulations of the uterine epithelium, and the fetal-maternal interface consists of an intricate interdigitation of fetal and maternal microvilli. In late gestation both chorionic and uterine epithelia are deeply indented by placental capillaries, so that the minimum intercapillary distance across the diffusion pathway may be as little as 2 microns. This distance appears to be less than that found in the epitheliochorial placenta of any other species of domestic ungulate in late gestation: it may be one of several adaptations to pregnancy at high altitude. Delivery of the fetal membranes occurs some 45 minutes after the birth of the fetus. The placenta is non-deciduate.

Amnion↗

PubMedDate not supplied

Morphological study of the fetal vasculature of the human term placenta: scanning electron microscopy of corrosion casts.

Microvascular corrosion casts of the fetal vessels of the normal human placenta were studied using the scanning electron microscope. All available evidence suggests that when prepared under standard conditions the resultant casts accurately replicate the original luminal morphology of the vessels, and are comparable between placentae. In conjunction with stereo-pair photography this technique allows for the rapid and unequivocal interpretation of the three-dimensional configuration of villous vasculature. Previously described structures such as dilated capillary loops and perivascular capillary networks can be viewed in new and dramatic perspective. It is hoped the technique may thus be of assistance to physiologists in the interpretation of experimental data concerning placental transport. Further work is in progress to apply the technique to the investigation of possible changes in fetal vasculature occurring in abnormal pregnancies.

Capillaries↗