[Ultrastructural study on human placental villi in toxemia of pregnancy--characteristic features obtained by a quick quenching and freeze substitution method].

In order to precisely assess ultrastructural changes in toxemic placenta, we tried to use the quick quenching and freeze substitution method (QM) during the preparation of placental villi. The findings in 10 normal and 15 toxemic placentae prepared by the conventional double fixation method (CM) were compared with the findings when prepared by QM. Most of the microvilli (m.v.) in syncytial cells (SCs) swelled in cases of toxemia. The average diameter of the Mv prepared by QM was approximately 48% greater than that of those prepared by CM. Many rough surfaced endoplasmic reticulum (rER) in the cytoplasm of SCs enlarged to form irregular shaped vesicles. The average diameter of rER prepared by QM was about 80% greater than that by CM. Protrusions of SCs towards the villous core and intervillous space were observed in all toxemic placentae prepared by CM, but only in severe toxemic placentae with IUGR when tissue preparation was done by QM. Fetal capillary endothelial cells were thicker in toxemic placentae than in normal ones by CM, but thinner in placentae prepared by QM. It is probable that the swelling of Mv and r-ER is due to hydropic degeneration. The contraction of SCs occurs in placentae of severe toxemic pregnancies with IUGR before fixation probably in situ.