[In-vitro formation of plasma polyps in the human placenta and their isolation by means of "inverted centrifugation" (author's transl)].

1. Histological observations on sliced human placenta shaked in Krebs-Ringer-solution showed an high plasma polyp formation by the syncytiotrophoblast without any monoidoacetate or sodiumfluoride poisoning [1]. 2. The high plasma polyp formation of placenta slices incubated with gased (96% O2, 4% CO2) Krebs-Ringer-solution and shaked at 37 degrees C decreased rapidly and lasted up to 40 min. 3. Perfusion of the placenta intervillosum with fetal serum added Krebs-Ringer-Solution gave results in plasma polyp production up to six times higher than serum free Krebs-Ringer-solution perfusions. 4. Plasma polyp isolation and concentration by one step is discribed applying the inverted centrifugation technique: Plasma polyps migrate centripetally in Krebs-Ringer-solution containing 6% Ficoll (Pharmacia) and were concentrated in the tip of a tube invertedly placed into a swing-out-rotor.